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Evaluation of the economic and environmental impact of combining dry reforming with steam reforming of methane
Abstract
Lately, there has been considerable interest in the development of more efficient processes to generate syngas, an intermediate in the production of fuels and chemicals, including methanol, dimethyl ether, ethylene, propylene and Fischer–Tropsch fuels. Steam methane reforming (SMR) is the most widely applied method of producing syngas from natural gas. Dry reforming of methane (DRM) is a process that uses waste carbon dioxide to produce syngas from natural gas. Dry reforming alone has not yet been implemented commercially; however, a combination of steam methane reforming and dry reforming of methane (SMR + DRM) has been used in industry for several years. The aim of this work was to simulate both the SMR and SMR + DRM processes and to conduct an economic and environmental analysis to determine whether the SMR + DRM process is competitive with the more popular SMR process. The results indicate that the SMR + DRM process has a lower carbon footprint. Further research on DRM catalysts could make this process economically competitive with steam methane reforming.
... SMR (i) is a well-established and large-scale technology, mostly used for hydrogen production from methane. In this route, CH 4 and steam react in a reformer over a nickel-alumina catalyst [16], at a temperature of 1073.15 to 1173.15 K and a pressure of 15 to 30 bar. ...
... This approach is particularly interesting as it can tolerate the varying concentration of CO 2 associated with biomethane. Nevertheless, the commercialization of this technology is still in its preliminary stage [16,19]. However, there are some drawbacks linked to these reforming routes, such as catalyst deactivation (mainly due to carbon deposition), and high energy demand, as the reforming reaction is endothermic and requires to be operated at high temperatures (1123.15 to 1273.15 ...
... Gangadharan et al. [16] also simulated the technology of chemical scrubbing with DEA in Aspen Plus for acid gas removal from natural gas. The simulation is rate-based, the thermodynamic property method is ELECNTRL, and also here the main blocks of the flowsheet are the absorber and stripper (RADFRAC distillation columns), but no solvent recirculation is included. ...
The Paris COP21 held on December 2015 represented a step forward global GHG emission reduction: this led to intensify research efforts in renewables, including biofuels and bioliquids. However, addressing sustainable biofuels and bioliquid routes and value chains which can limit or reverse the ILUC (indirect land-use change effect) is of paramount importance. Given this background condition, the present study targets the analysis and modelling a new integrated biomass conversion pathway to produce renewable advanced fuels, enabling the issue of indirect land-use change (ILUC) of biofuels to be tackled. The bioenergy chain under investigation integrates the decentralized production of biogas through anaerobic digestion and its upgrading to biomethane, followed by a centralized conversion to liquid transport fuels, involving methane reforming into syngas, Fischer–Tropsch (FT) synthesis, and methanol synthesis. The methodology adopted in this work stem from extensive literature review of suitable bio/thermo-chemical conversion technologies and their process modelling using a commercial flow-diagram simulation software is carried out. The major significance of the study is to understand the different modelling approaches, to allow the estimation of process yields and mass/energy balances: in such a way, this work aims at providing guidance to process modellers targeting qualitative and quantitative assessments of biomass to biofuels process routes. Beyond FT products, additional process pathways have been also explored, such as MeOH synthesis from captured CO2 and direct methane to methanol synthesis (DMTM). The analysis demonstrated that it is possible to model such innovative integrated processes through the selected simulation tool. However, research is still needed as regards the DMTM process, where studies about modelling this route through the same tool have not been yet identified in the literature.
... It is a mixture of CO and H 2 gases, which is toxic, odorless, and colorless [162]. For the production of syngas, any carbon source can be used; however, steam reforming of methane is the most commonly used production process for syngas [163]. Considering the high emissions, carbon dioxide is gaining extensive interest to be used as a primary feedstock in the syngas production. ...
... The new technologies involve various routes with CO 2 reforming processes using hydrocarbons. Other ways can be catalytic reverse water gas shift (RWGS), thermocatalytic route, plasma process, electro-or photocatalysis, and other bioprocesses such as enzyme coupled nanoparticle systems, using a biomass char, bio-electrochemical reduction, and catalysts [163,164]. ...
... process. Supported nickel is the most studied among the catalysts among a few other supported noble metals like Rh, Ru, and Pt [163,164,166]. ...
Carbon dioxide levels in the earth atmosphere have been rising to alarming levels over the past few decades by human activity and thus caused global climate change due to the “greenhouse effect,” which in turn brought about adverse effects on the planet. Major sources of carbon dioxide (CO2) emissions include fossil fuel combustion, land-use change, industrial processing, respiration of various life forms, and decomposition of biomass. However, over the past 20 years, there has been a continuous research effort on the reducing carbon dioxide levels, by converting into the syngas, methanol, dimethyl carbonate, epoxides, polymers, and fine chemicals through chemical catalytic or biotransformation routes. Biological conversion including microbial and/or enzymatic conversion holds high potential as an alternative to the energy-intensive chemical conversion of CO2. Besides being the low energy process, bio-conversion of CO2 offers several unique advantages such as an easy and improved production at a high scale with a better conversion rate, the possibility of a diverse product range, and hyper-production by genetic modifications with zero competition for land with food crops. To this end, products that use CO2 biotransformation by the global biotech and chemical industry are only about 11.5 million tons annually, and it is a very small fraction of the approximately 24 billion tons of annual CO2 emission. Hence, there is an enormous scope for generation of high end biorefineries through CO2 bioconversion systems. Here, we review the various production sources of CO2, the metabolic and enzymatic CO2 conversion pathways, and the commercialization potentiality of various green chemicals from CO2.
... The potential environmental impact due to component k in streams is denoted by ø k such that the PEI generated within the chemical process is determined as the difference between the PEI out and PEI in of the system. An extensive discussion of the WAR algorithm is beyond the scope of this study and is available in the literature [33,35]. To determine the value of ø k , the summation of the separate PEIs from the disposal of component k responsible for the impacts of l is undertaken with the categories of impacts l summarized in Table 2. ...
... Category of impact[35] ...
Pomace is generated during fruit processing and is regarded as a highly polluting waste stream due to its high moisture content, biological instability, and acidic properties. To facilitate pomace management, this study has applied the biorefinery concept to develop systems that facilitate value extraction. To this regard, alternative scenarios for the production of polyphenolic compounds and bioenergy from apple pomace were investigated using ASPEN Plus for process modeling, simulation, and analysis. Systems facilitating the production of polyphenols via the use of the green solvents (i.e. subcritical water in scenario (a) and ethanol in scenario (b)), while also co-producing bioenergy, were compared to a system that produced only bioenergy (i.e. scenario (c)). Comparisons of profitabilities and environmental performances were achieved via considerations of the net present values (NPVs) and potential environmental impacts (PEIs) of all scenarios. The study was able to show that scenario (a) constituted the only economically viable strategy, with a NPV of US$ 19.86 million, while scenarios (b) and (c) were determined to have NPVs of US$ − 88.12 million and US$ − 4.05 million respectively. Scenario (b) was also determined to have the poorest environmental performance with a PEI of 148 kPEI/h. Notably, although scenario (c) (PEI of 0.21 kPEI/h) was determined to present a better environmental performance than scenario (a) (PEI of 47 kPEI/h), its economic infeasibility indicated that it will be impractical to consider it as a viable pomace valorization strategy in a scaled-up system. This study therefore proposed that scenario (a) may constitute a preferred pomace valorization strategy provided technological innovations, i.e., use of alternative energy sources and gas filters, are explored to reduce the major existing challenge of enhanced global warming potential due to greenhouse gas emissions. This study therefore provides information regarding the sustainability implication of executing different biorefinery scenarios for pomace management in the fruit processing industry.
Graphical abstract
... 1−3 Recently, it has also been recognized as a potential fuel/energy carrier in applications, such as electrochemical fuel cells, providing direct power output to electric vehicles, and combustors without CO 2 coproduct formation. 4,5 Globally, >90% of the industrial hydrogen (gray hydrogen) is produced using the methanesteam reforming (SMR) process (CH 4 + 2H 2 O ⇌ 4H 2 + CO 2 , ΔH 0 ≈ 206 kJ/mol). However, for each kilogram of hydrogen, the SMR process simultaneously generates ∼9.5 kg of CO 2 . ...
... A noncatalytic model of HC pyrolysis has been previously reported. 31 The intermediates of primary pyrolysis, 4 and H 2 moles near the inlet produced by two stages of pyrolysis, which are dependent on the functional-group composition of the selected HC fuel, is crucial in this case. However, the catalytic environment might affect the selectivity of the product intermediates (CH 4 and H 2 ) of the first two stages of HC pyrolysis. ...
... • A combination of steam and dry reforming of methane (SMR + DRM) were highlighted, methane separation and SMR process simulation and environmental implications and global warming potential 2012 [34] • Methane to synthesis gas; a review of the steam reforming reaction is presented, and the dry reforming and partial oxidation 2013 [35] • Utilization of steel slag, physical recovery and granulation methods, Chemical methods, coal gasification analysis. 2013 [36] • Preparation and activity of Ni-based catalysts (Ni/CeAl, Ni/LaAl and Ni/CeLaAl) highly effects of modification of Ni/Al catalysts with CeO 2 and/or La 2 O 3 on catalytic performance. ...
... Carbon Capture and Storage (CCS) is acquiring a lot of attention at the current time due to its efficiency in curtailing the effect of anthropogenic processes yielding CO 2 . Projections of the world energy are moving towards the generation of less hazardous green materials and reducing to the barest minimum, reliance on processes with detrimental side effects [34,[48][49][50][51]. However, dry methane reforming provides more advantage over CSS in that it incorporates the conversion of both CO 2 and methane to produce energy-based gaseous fuels. ...
Environmental pollution and energy depletion are among society's great concerns today. Simultaneous removal of the two most harmful greenhouse gases viz; CH 4 and CO 2 by dry reforming of methane (DRM) is a promising alternative. Production of hydrogen as a substitute fuel is an exciting and promising technology since it contributes to the decrease of environmentally hazardous emissions. Despite the numerous environmental incentives of the DRM process, it is still at an immature stage in the industry; its main problems are being highly endo-thermic, severe catalyst coking and subsequent deactivation among others. Hereunder, the bibliometric analysis of title search from 1970 to 2022 for keywords, countries, journals, inter-country coauthor networks and co-occurrence visualizations using the WoS database along with the R-studio were presented. Within 32 years (1990-2022), data were filtered from 1000 publications, 863 of which are research papers with an average citation of 6.182 per document, 34 review articles and 86 article proceedings with 1730 and 1338 total author keywords, respectively. It is justified that a research gap still exists as the DRM industrialization is only partly achieved. In the subsequent sections, highlights of the significance of commercializing the process is highly emphasized while effort is devoted to devising techniques to address related challenges undermining its commercialization. Possible solutions to problems that may hinder the commercialization of the process were discussed and how its commercialization will be of immense benefit in that profitable implementation could generate feed for the Fischer-Tropsch's energy process. To wind up, the article stated how the various factors can be put into practice for hydrogen production.
... The potential environmental impact due to component k in streams is denoted by øk such that the PEI generated within the chemical process is determined as the difference between the PEI out and PEI in of the system. An extensive discussion of the WAR algorithm is beyond the scope of the present study and is available in the literature [41,42,44]. To determine the value of øk, the summation of the separate PEIs from the disposal of component k responsible for the impacts of l is undertaken with the categories of impacts l summarized in Table 1. ...
... Category of impact[42,44] ...
Pomace is a waste stream that is generated during fruit processing and is regarded as highly polluting due to its high moisture content, biological instability and acidic properties. To facilitate pomace management, the current study has applied the biorefinery concept to develop systems that facilitate value extraction. In this regard, alternative scenarios for the production of polyphenolic compounds and electricity from apple pomace were investigated using ASPEN Plus for process simulations. Scenarios enabling the production of polyphenols using green solvents of subcritical water (scenario (a)) and ethanol (scenario (b)), while also co-producing electricity, were compared to scenario (c) in which the pomace was employed in only electricity production. Comparisons of profitabilities and environmental performances were achieved via a consideration of the net present values (NPVs) and potential environmental impacts (PEIs) respectively, of all scenarios. The study was able to show that scenario (a) constituted the only economically viable strategy, with an NPV of US$19.86 million, while scenarios (b) and (c) were determined to have NPVs of US$-88.12 million and US$-4.05 million respectively. Scenario (b) was also determined to have the poorest environmental performance with a PEI of 148 kPEI/h. Notably, although scenario (c) (PEI of 0.21 kPEI/h) was determined to present a better environmental performance than scenario (a) (PEI of 47 kPEI/h), its economic infeasibility indicated that it will be impractical to consider it as a viable pomace strategy in a future scaled-up system. The present study therefore proposed that scenario (a) may constitute a preferred pomace valorization strategy provided technological innovations i.e. use of renewable energy and gas filters are explored and integrated to reduce the major existing challenge of greenhouse gas emissions. This study provides information regarding the sustainability implications of executing the proposed biorefinery scenarios for pomace management in the fruit processing industry.
... This article contains data related to the research article entitled "Environmental and energetic analysis of coupling a Biogas combined cycle power plant with carbon capture, organic Rankine cycles and CO 2 utilization processes" [2] . The tables contain the necessary data for the realization of the CO 2 utilization processes simulation, first for comparison and verification, are presented the parameters obtain by other articles [3][4][5] , then the parameters used for the simulations of the study cases of the related article are presented. Fig. 1 and Table 1 , presents the flowchart and the parameters used in the simulations of each case, for the formic acid production plant (FAPP), Fig. 2 and Table 2 the parameters for the methanol production plant (MPP), Fig. 3 and Table 3 the parameters for the syngas production plant (SynPP) via hydrogenation, and finally Fig. 4 and Table 4 presents the parameters for the syngas production plant (SynPP) via dry reforming of methane (DRM). ...
... Fig. 3 shows the flowchart of the production of syngas by CO 2 hydrogenation, which was carried out with the parameters in Table 3 , obtained from Barbera et al. [5] . Finally, the process of syngas production by dry reforming of methane is shown in Fig. 4 , the parameters of Table 4 were used in the simulation and were obtained from the article of Gangadharan et al. [4] . ...
The simulation of chemical processes is a useful tool that provides valuable information and data for process analysis. The obtained data from simulations, could be used later in optimization, economic, environmental, energetic, exergetic and different kind of analysis. In this work, it is presented the data that serves as basis for the simulation of different chemical process that use CO2 as a raw material, to produce some value-added chemicals and fuels. The stream of captured CO2 is taken from a biogas combined cycle power plant, and it is fed to a formic acid production plant, a syngas production plant and a methanol production plant.
... Furthermore, PEI/h of the WAP was considered negligible in both cases due to the implied renewability of the biomass resource. Further descriptions of the WAR algorithm and the governing equations are outside the scope of the present study and are presented elsewhere [85,86,88]. Table 2. Impact categories that constitute the basis of the potential environmental impact [86,88]. ...
... Further descriptions of the WAR algorithm and the governing equations are outside the scope of the present study and are presented elsewhere [85,86,88]. Table 2. Impact categories that constitute the basis of the potential environmental impact [86,88]. ...
The global demand for acrylic acid (AA) is increasing due to its wide range of applications. Due to this growing demand, alternative AA production strategies must be explored to avoid the exacerbation of prevailing climate and global warming issues since current AA production strategies involve fossil resources. Investigations regarding alternative strategies for AA production therefore constitute an important research interest. The present study assesses waste apple pomace (WAP) as a feedstock for sustainable AA production. To undertake this assessment, process models based on two production pathways were designed, modelled and simulated in ASPEN plus® software. The two competing production pathways investigated included a process incorporating WAP conversion to lactic acid (LA) prior to LA dehydration to generate AA (denoted as the fermentation–dehydration, i.e., FD, pathway) and another process involving WAP conversion to propylene prior to propylene oxidation to generate AA (denoted as the thermochemical–fermentation–oxidation, i.e., TFO, pathway). Economic performance and potential environmental impact of the FD and TFO pathways were assessed using the metrics of minimum selling price (MSP) and potential environmental impacts per h (PEI/h). The study showed that the FD pathway presented an improved economic performance (MSP of AA: USD 1.17 per kg) compared to the economic performance (MSP of AA: USD 1.56 per kg) of the TFO pathway. Crucially, the TFO process was determined to present an improved environmental performance (2.07 kPEI/h) compared to the environmental performance of the FD process (8.72 kPEI/h). These observations suggested that the selection of the preferred AA production pathway or process will require a tradeoff between economic and environmental performance measures via the integration of a multicriteria decision assessment in future work.
... Methane reformation proceeds following a mixture of Eqs. (12)-(14) ( Gangadharan et al., 2012 ). ...
... Economically speaking, the dry reforming of methane is quite attractive as it reduces CO 2 and methane emissions while creating a syngas stream which can be further processed into valuable chemicals. Dry reforming has not yet been introduced as a distinct operation on a commercial basis yet, it has been used in conjunction with steam reforming for quite a long time ( Gangadharan et al., 2012 ). Theoretical calculations show that dry reforming temperatures can be further reduced from current practice, perhaps to as low as 300 °C, but it will require the development of a high efficiency heterogeneous catalyst ( Nikoo and Amin, 2011 ). ...
CO2 utilizations are essential to curbing the greenhouse gas effect and managing the environmental pollutant in an energy-efficient and economically-sound manner. This paper seeks to critically analyze these technologies in the context of each other and highlight the most important utilization avenues available thus far. This review will introduce and analyze each major pathway, and discuss the overall applicability, potential extent, and major limitations of each of these pathways to utilizing CO2. This will include the analysis of some previously underreported utilization avenues, including CO2 utilization in industrial filtration and the processing of raw industrial materials such as iron and alumina. The core theme of this paper is to seek to treat CO2 as a commodity instead of a liability.
... A microchannel reactor is preferably designed to achieve a temperature trajectory down the length of the reaction chamber that approaches a predetermined temperature trajectory [79,80]. Typically, this predetermined temperature trajectory is substantially different from the temperature trajectory that will occur if the reaction is allowed to proceed adiabatically or isothermally [81,82]. This predetermined temperature trajectory approaches a theoretically determined optimum temperature trajectory based on the reaction rate and design parameters specific to the particular application [83,84]. ...
Conventional methods of producing a synthesis gas are expensive and complex installations. In order to overcome the complexity and expense of such installations, it is proposed to generate the synthesis gas within autothermal fixed bed reactors that utilize structured catalysts and different surface features to generate the heat necessary to support endothermic heating requirements of the steam reforming reactions. The present study is focused primarily upon the thermal chemical reaction characteristics of autothermal fixed-bed reactors with structured catalysts and different surface features. The heat capacity, thermal conductivity, and viscosity of the mixture are calculated as a mass-weighted average of the values for each constituent. In addition, the material properties of each individual species are functions of the local temperature. When solving the species mass transport equations, binary mass diffusion coefficients are used directly. Only isotropic catalyst structures are considered and the permeability and inertial resistance factor are held constant. The effective thermal conductivity of the catalyst structure system including the porous structure and intervening gas is calculated based upon the porosity of the porous medium, the fluid phase thermal conductivity, and the porous medium effective thermal conductivity as measured in air at ambient conditions. The present study aims to explore how to effectively generate the synthesis gas within autothermal fixed bed reactors that utilize structured catalysts and different surface features. Particular emphasis is placed upon the heat and mass transport phenomena involved in autothermal fixed bed steam reforming reactors. The results indicate that for catalytic thermal chemical reactions, both kinetic impediments are substantially reduced permitting realization of theoretical or near theoretical reaction kinetics. The heat transfer chamber is in thermal contact with the reaction chamber volume, the heat transfer chamber transferring heat at the enhanced heat transfer rate across the wall between the heat transfer chamber and the reaction chamber, thereby obtaining the enhanced production rate per reaction chamber volume for the thermal chemical reaction. Structured catalyst configurations result in high rates of heat transport from the oxidation side to the reforming side. Typically, combustion takes place at low or near-atmospheric pressure, although high pressure combustion is widely practiced. The heat that is generated on the combustion side is quickly transferred on the reforming side. The heat integrated reforming reactor offers several advantages over conventional flame-based reforming reactors. The incorporation of a simultaneous endothermic reaction to provide an improved heat sink may enable a typical heat flux of roughly an order of magnitude above the convective cooling heat flux. The wall can be constructed from any material, but materials that offer low resistance to heat transfer such as metals and metallic alloys are preferred. In this configuration, heat is generated by combustion in the catalytic chamber and is transported very easily and efficiently though the wall to the reforming chamber where the heat demanding reforming reactions take place. The presence of a catalyst and lower temperatures permit significantly higher space velocities to be used compared to flame-based reformers.
Keywords: Hydrocarbons; Reactors; Structures; Properties; Reforming; Combustion
... S-3 (H2/CO = 1.90), and S-4 (H2/CO = 1.65). In their work, Preeti et al. [47] found a higher ratio of synthetic gas (H2/CO = 3) during steam reforming of methane, whereas the ratio required for the Fischer-Tropsch process or methanol synthesis was found equal to H2/CO = 2 [48,49]. ...
The generation of hydrogen from unconventional oil is expected to increase significantly during the next decade. It is commonly known that hydrogen is an environmentally friendly alternative fuel, and its production would partially cover the gap in energy market requirements. However , developing new cheap catalysts for its production from crude oil is still a challenging area in the field of petroleum and the petrochemical industry. This study presents a new approach to synthesizing and applying promising catalysts based on Ni, Co, and Ni-Co alloys that are supported by aluminum oxide Al2O3 in the production of hydrogen from extra-heavy crude oil in the Tahe Oil Field (China), in the presence of supercritical water (SCW). The obtained catalysts were characterized via scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, transmission electron microscopy (TEM), and, X-ray diffraction analysis (XRD). The obtained XRD data showed 3.22% of Co 2+ in the Co/Al2O4 catalyst, 10.89% of Ni 2+ in the Ni/Al2O4 catalyst, and 1.51% of Co 2+ and 2.42% of Ni 2+ in the Ni-CoAl2O3 bimetallic catalyst. The BET measurements of the obtained catalysts showed a surface area ranging from 3.04 to 162 m²/g, an average particle size ranging from 0.037 to 0.944 µm, and micropore volumes ranging from 0.000377 to 0.004882 cm³/g. The thermal, SCW, and catalytic upgrading processes of the studied samples were conducted in a discontinuous autoclave reactor for 2 h at a temperature of 420 °C. The obtained results revealed that thermal upgrading yielded 1.059 mol.% of H2, and SCW led to 6.132 mol.% of H2; meanwhile, the presence of Ni-CoAl2O3 provided the maximal rate of hydrogen generation with 11.783 mol.%. Moreover, Ni-CoAl2O3 and NiAl2O3 catalysts have been found to possess good affinity and selec-tivity toward H2 (11.783 mol.%) and methane CH4 (40.541 mol.%). According to our results, the presence of SCW increases the yield of upgraded oil (from 34.68 wt.% to 58.83 wt.%) while decreasing the amount of coke (from 51.02 wt.% to 33.64 wt.%) due to the significant amount of hydrogen generation in the reaction zone, which reduces free-radical recombination, and thus, improves oil recovery. Moreover, the combination of SCW and the synthetized catalysts resulted in a significant decrease in asphaltene content in the upgraded oil, from 28% to 2%, as a result of the good redistribution of hydrogen over carbons (H/C) during the upgrading processes, where it increased from 1.39 to 1.41 in the presence of SCW and reached 1.63 in the presence of the Ni-CoAl2O3 catalyst. According to the XRD results of the transformed form of catalysts (CoNi3S4), after thermal processing , heteroatom removal from extra-heavy crude oil via oxidative and adsorptive desulfuriza-tion processes is promoted. These findings contribute to the expanding body of knowledge on hydrogen production from in situ unconventional oil upgrading. Citation: Djimasbe, R.; Ilyasov, I.R.; Kwofie, M.; Khelkhal, M.A.; Emelyanov, D.A.; Al-muntaser, A.A.; Suwaid, M.A.; Varfolomeev, M.A. Direct Hydrogen Production from Extra-Heavy Crude Oil under Supercritical Water Conditions Using a Catalytic (Ni-Co/Al2O3) Upgrading Process.
... Por ello, en la actualidad, el 80 -85% de H2 en el mundo es producido mediante reformado con vapor [19,22]. El SRM (r.1) produce una relación H2/CO que es de 3:1 [23], más alta que la relación requerida para la síntesis de Fischer -Tropsch que es de 2:1 [24]. El SRM requiere un aporte energético intensivo debido a su naturaleza endotérmica por lo que su costo es muy elevado [25]. ...
... Simpson and [29][30][31]. Gangadharan et al. [32], Rhodes et al. [33], and other papers performed techno-economic analysis combining SMR with carbon sequestration [34][35][36][37][38][39][40]. The authors have mapped the cost structures and economics of H 2 production from different conversion pathways, including the factors affecting the techno-economic analysis of SMR, CO 2 utilization, and life cycle assessment. ...
The European Union (EU) imports a large amount of natural gas, and the injection of renewable hydrogen (H 2) into the natural gas systems could help decarbonize the sector. The new geopolitical and energy market situation demands urgent actions in the clean energy transition and energy independence from fossil fuels. This paper aims to investigate techno-economic analysis, barriers, and constraints in the EU policies/frameworks that affect natural gas decarbonization. First, the study examines the levelized cost of hydrogen production (LCOH). The LCOH is evaluated for blue and grey hydrogen, i.e., Steam Methane Reforming (SMR) natural gas as the feed-stock, with and without carbon capture, and green hydrogen (three type electrolyzers with electricity from the grid, solar, and wind) for the years 2020, 2030, and 2050. Second, the study evaluates the current policies and framework based on a SWOT (Strength, Weakness, Opportunities, and Weakness) analysis, which includes a PEST (Political, Economic, Social, and Technological) macroeconomic factor assessment with a case study in Portugal. The results show that the cheapest production costs continue to be dominated by grey hydrogen (1.33 €/kg.H 2) and blue hydrogen (1.68 €/kg.H 2) in comparison to green hydrogen (4.65 €/kg.H 2 and 3.54 €/kg.H 2) from grid electricity and solar power in the PEM-Polymer Electrolyte Membrane for the year 2020, respectively. The costs are expected to decrease to 4.03 €/kg.H 2 (grid-electricity) and 2.49 €/kg.H 2 (solar-electricity) in 2030. The LCOH of the green grid-electricity and solar/wind-powered Alkaline Electrolyzer (ALK) and Solid Oxide Electrolyzer Cell (SOEC) are also expected to decrease in the time-span from 2020 to 2050. A sensitivity analysis shows that investments costs, electricity price, the efficiency of electrolyzers, and carbon tax (for SMR) could play a key role in reducing LCOH, thereby making the economic competitiveness of hydrogen production. The key barriers are costs, amendments in rules/regulations, institutions and market creation, public perception, provisions of incentives, and constraints in creating market demand.
... Currently, the combination of dry and steam reforming is gaining increasing attention. The interest of the combined process lies in the results from the higher efficiency of the H 2 production, thus a higher H 2 /CO ratio, which is the key factor in syngas quality [52,115,116] and the possibility to control the composition of the outlet stream. Moreover, the steam in the inlet gas can result in a decrease in the carbon deposition on the catalyst surface due to the gasification of coke, and therefore it allows to avoid the major problem involving catalyst deactivation [117]. ...
Emissions of greenhouse gases and growing amounts of waste plastic are serious environmental threats that need urgent attention. The current methods dedicated to waste plastic recycling are still insufficient and it is necessary to search for new technologies for waste plastic management. The pyrolysis-catalytic dry reforming (PCDR) of waste plastic is a promising pro-environmental way employed for the reduction of both CO2 and waste plastic remains. PCDR allows for resource recovery, converting carbon dioxide and waste plastics into synthetic gas. The development and optimization of this technology for the high yield of high-quality synthesis gas generation requires the full understanding of the complex influence of the process parameters on efficiency and selectivity. In this regard, this review summarizes the recent findings in the field. The effect of process parameters as well as the type of catalyst and feedstock are reviewed and discussed.
... The chain growth probability is affected by the parameters of temperature, pressure, and hydrogen-to-carbon monoxide ratio (van Berge and Everson, 1997;Ma et al., 1999;Gangadharan et al., 2012;and Lopes et al., 2012). Figures 11.3 and 11.4 show the effect of temperature on a fraction of hydrocarbons formed during Fischer-Tropsch synthesis using a cobalt catalyst (Aluha et al., 2018) and ruthenium catalyst (Hunpinyo et al., 2017). ...
DESCRIPTION
Graphene is a carbon allotrope; a single layer of carbon atoms arranged in a hexagonal lattice structure makes it the thinnest and strongest 2D material. However, graphene alone cannot be used directly for many applications. Graphite (multilayer graphene sheets), when introduced to oxidation, gives graphene oxide (GO), which has oxygen-containing functional groups and can integrate metal nanoparticles. Metal attaches to GO sheets both electrostatically and covalently by GO–COOH groups that undergo simultaneous reduction to form metal–reduced graphene oxide (M-rGO) nanocomposites. Syntheses of M-rGO nanocomposites include solvothermal processes, hydrothermal processes, UV-assisted photocatalytic and chemical reduction, microwave irradiation, sol-gel, and self-assembly. The nanocomposite characterization is essential to study the structural and chemical properties like core morphologies, crystallographic structure, electronic state, disorder, and defects. The M-rGO provides benefits like enhanced peroxidase-like catalytic activity, high surface area, electrical conductivity, thermal stability, and optical property. These exquisite properties make it a better platform for sensing environmental pollutants, and metabolites including biologically important analytes with high specificity and selectivity. This chapter discusses the synthesis processes, characterization techniques, and sensing applications for environmental pollutants and biologically relevant molecules/species using metal–rGO-based nanocomposites.
... The chain growth probability is affected by the parameters of temperature, pressure, and hydrogen-to-carbon monoxide ratio (van Berge and Everson, 1997;Ma et al., 1999;Gangadharan et al., 2012;and Lopes et al., 2012). Figures 11.3 and 11.4 show the effect of temperature on a fraction of hydrocarbons formed during Fischer-Tropsch synthesis using a cobalt catalyst (Aluha et al., 2018) and ruthenium catalyst (Hunpinyo et al., 2017). ...
... The effluent from the reactor is cooled to 25 • C and then sent to a flash separator where the water formed during the reaction is separated. The parameters used for the simulation were obtained from the article by Gangadharan et al., 2012 and they are shown in Table S4 (see SD), as well as the parameters used later for the study case of this work. ...
Greenhouse gas emissions from power plants that use fossil fuels cause a serious impact to the environment, for this reason the use of renewable energy technologies is an important alternative as a way of combatting climate change. The production of power via biomass is considered as a carbon neutral energy resource, but it is well known that the non-fossil CO2 emitted from this type of processes can also be captured. In order to do so, in this work it is proposed a match between a Biogas combined cycle power plant and postcombustion carbon capture process, to capture the CO2 produced by the biogas combustion, and also it considered a match with an organic Rankine cycle that uses the wasted energy of the combustion gases. Additionally, it is considered that the captured carbon is used to produce some value-added chemicals and fuels. Environmental and energetic evaluations were carried out for the coupling of those technologies. The implementation of the carbon capture plant, results on a diminution of the 87% of the emission of the combined cycle power plant. The life cycle analysis results show that the study case of Syngas production via dry reforming of methane, presents the lower global warming potential (0.088 CO2-eq kg/kg) and it was also found that the global warming potential has a reduction with the help of the mass integration between the different alternatives of CO2 utilization. Finally, it was found an annual reduction of 0.055 CO2-eq t for the system with mass integration compared with the cases without mass integration.
... 43 Various research articles demonstrated the ability of dry reforming process for the production of synthetic diesel, gasoline, hydrogen, etc. [44][45][46] Gangadharan et al, carried out an investigation to study the economic and ecological impact of dry reforming in combination with steam reforming of methane (CH 4 ). 47 The results revealed that the combination of steam reforming and dry reforming of CH 4 is a more environmental friendly approach as compared to standalone steam reforming of CH 4 . However, more emphasis is needed to develop a suitable catalyst that can make the process an economically friendly option. ...
Energy plays a pivotal role in industrial development of any country. At present, most of the countries are utilizing fossil fuels, mainly coal and natural gas as energy sources for power production. However, these sources emit high amounts of carbon dioxide (CO2) into the atmosphere resulting in global warming. Hence, the fossil fuel–based thermal power plants need to be integrated with CO2 sequestration and utilization processes for sustainable power production. In this work, four natural gas combined cycle (NGCC) power plant configurations are proposed—two with CO2 capture and sequestration (single and double calcium looping units) and two with CO2 capture and utilization (for production of dimethyl ether). Energy, exergy, environmental, and economic analyses are carried out to assess the performance of the proposed novel configurations against the conventional NGCC power plant. These analyses reveal that the NGCC power plant integrated with double calcium looping unit captures 91.32% of CO2 with an energy penalty of 6.73%. The proposed CO2 capture and utilization integrated configurations have low electrical power output; however, the conversion of CO2 to high energy density dimethyl ether (DME) product resulted in overall energy and exergy efficiency gain. The CO2 capture and utilization configuration integrated with solar energy is able to convert the total captured CO2 to DME and makes the process sustainable.
... In the HyChem approach, the quantification of key pyrolysis intermediates of first stage pyrolysis is described using stoichiometric parameters in three lumped fuel chemistry reactions, as shown in eqs 1, 2, and 3 and Table 1. (1) These stoichiometric parameters were obtained experimentally with the help of real fuel pyrolysis speciation data of CH 4 and C 2 H 4 in shock tube experiments 42,43 and C 3 H 6 , C 4 H 8 , C 6 H 6 , and C 7 H 8 (toluene) in flow reactor experiments. 39−41 Here, e d , b d , e a , and b a are dependent upon the rest of the stoichiometric parameters by carbon and hydrogen mass balance. ...
The evolution of hydrogen from methane decomposition in a liquid metal bubble reactor (LMBR) has become a recent subject of interest; this study examines a novel approach to hydrogen production from pyrolysis of complex hydrocarbon fuels. Modeling hydrocarbon fuel decomposition in an LMBR is executed in two stages of pyrolysis: First, primary pyrolysis intermediates are simulated using a functional-group-based kinetic model (FGMech). Then, a detailed high temperature mechanism (AramcoMech 1.3 + KAUST PAH + 5 solid carbon chemistry) is applied to simulate secondary pyrolysis of intermediates. The quantities of major products of the secondary pyrolysis simulation (CH4, H2, Cs, C6H6) are approximated by simplified regression equations. Further decomposition of smaller hydrocarbons (until exiting the reactor) is simulated using a coupled kinetic and hydrodynamics model that has been reported in the literature. The mixing effects of bubble coalescence and breakup are investigated in a comparative study on homogeneous and non-homogeneous reactors. Finally, a qualitative relationship between H2 yield per mass of fuel, functional group, and other factors such as temperature, pressure, and residence time is analyzed. In general, the H/C ratio and cyclic/aromatic content are the main features influencing total conversion to H2.
... The dry reforming of CH 4 has been researched for a long time in the utilization of natural gas [5]. From the view of CH 4 utilization, the dry reforming is inferior to the steam reforming because the dry reforming produces a less amount of H 2 and forms a larger amount of carbonaceous deposit (coke) [6][7][8]. ...
The dry reforming of CH4 (with CO2) at 800 °C under 1 MPa to synthesis gas and the synthesis of dimethyl ether (DME) from synthesis gas were combined. A Ni/(MgO)3·Al2O3 catalyst derived from Mg3Ni3Al2(OH)16CO3·xH2O hydrotalcite precursor showed a CH4 conversion of 85.4% after 5 min on stream for the dry reforming. The CH4 conversion decreased to 70.1% after 15 h on stream because the carbonaceous deposit formed during the reaction covered the active sites of Ni/(MgO)3·Al2O3 catalyst. The deactivated Ni/(MgO)3·Al2O3 catalyst was refreshed by calcining in air at 800 °C and subsequently reducing in H2. A mechanical mixed catalyst containing Cu/(ZnO)3·Al2O3 and Cs2.5H0.5PW12O40 (denoted as Cu/(ZnO)3·Al2O3 + Cs2.5) was used for the DME synthesis from syngas. Cu/(ZnO)3·Al2O3 + Cs2.5 showed a CO conversion of 38.5% and a DME selectivity of 63.8% at 260 °C under 1 MPa. A stable activity of Cu/(ZnO)3·Al2O3 + Cs2.5 had been maintained over 30 h in the DME synthesis. A two-stage process was designed for the DME synthesis from CH4 and CO2. Two fixed-bed reactors filled with Ni/(MgO)3·Al2O3 were connected in parallel (switching between reaction and refresh) for the CH4 dry reforming. A fixed-bed reactor filled with Cu/(ZnO)3·Al2O3 + Cs2.5 was connected in series with the two reactors filled with Ni/(MgO)3·Al2O3 to produce DME. The conversion of CH4 was kept at above 80% and the yield of DME was kept at above 20% after 30 h on stream for the DME synthesis from CH4 and CO2.
Graphic Abstract
A two-step process combining CH4 dry reforming to syngas and DME synthesis from syngas was designed for the DME synthesis from CH4 and CO2. The conversion of CH4 was kept at above 80% and the yield of DME was kept at above 20% after 30 h on stream in the two-stage process
The main object of this research is the development of a mathematical framework to investigate the effect of CO2 feeding on the quality of produced syngas in an industrial autothermal reforming over Ni-Al2O3 catalyst. The considered reformer is consist of two main parts including the combustion and catalytic sections aligned in a series structure. The combustion chamber as a perfectly mixed reactor is simulated by the CHEMKIN package considering different detailed kinetic mechanisms including DRM 22, GRI 1.2, and GRI 3.0. The tabular catalytic reactor is heterogeneously modeled based on the mass and energy balance equations considering heat and mass transfer resistances in the gas and catalyst phases. The accuracy of developed model and considered thermal mechanisms are compared to plant data. After selection of an accurate thermal kinetic model, the effect of CO2 injection on the conversion of CH4 and CO2 and the quality of produced syngas are investigated at steady state conditions. Based on the simulation results, increasing the CO2 to CH4 molar ratio in the range of 0.2–2.0 could increase the CO2 conversion in the applied reformer up 30.83%.
Electrochemical methane-to-methanol technologies are regarded as one of the most attractive options to improve greenhouse gas emissions while providing a pathway to produce one of the most important bulk industrial chemicals. In recent years, several reports demonstrated individual cells producing methanol and other C-1 products while proclaiming that these cells will inevitably lead to industrial adoption at small sites with flared, stranded natural gas. However, the practical realization of these systems relies on finding operating regimes that can lead to profitability, which has not been well studied in the literature to date. Here we provide detailed calculations of process profitability over 4000 cases for electrochemical methane-to-methanol processes while considering two different overall reactions, multiple production scales, a wide range of operating conditions (voltage, current density), and various electrical costs. Finally, the analysis shows that the technology requires substantial improvement before expecting profit, and targets are determined for future performance, providing direction for R&D in this potentially transformational area.
The NiAl2O4 spinel exhibited a metal exsolution phenomenon to form Ni nanoparticles and nonstoichiometric Ni1−xAl2O4−x without structural collapse in a reducing atmosphere. The Ni exsolution behavior of NiAl2O4 was strongly affected by the reducing conditions, such as the reduction temperature and holding time during the reduction. The average particle size and amount of the exsolved Ni metal increased with increase in both the reduction temperature and the holding time. The re-dissolution oxidation reaction of the exsolved Ni into Ni1−xAl2O4−x to form NiAl2O4 occurred reversibly over 900 °C. The exsolved Ni nanoparticles were socketed into the surface of the reduced NiAl2O4 matrix and well dispersed without any agglomeration. Owing to this microstructure leading to an extension of the catalytic active site and suppression of agglomeration, the Ni-exsolved NiAl2O4 exhibited better steam methane reforming performance compared with the commercial Ni/Al2O3 catalyst. In addition to the improvement in catalytic activity, the Ni-exsolved NiAl2O4 showed strong tolerance for the formation of carbon due to a smaller driving force for carbon diffusion resulting from the nano-socketed structure.
Jet biofuel (JBF) is identified as an essential solution to mitigate the carbon footprint of the aviation sector. Since aeroplanes rely solely on liquid fuels, the development of pathways that generates JBF as a major product has become crucial. Thus far, seven pathways to produce JBF have been developed and certified over the past decade. Each of these pathways accommodates a specific type of biomass. However, the availability, sustainability and feasibility of feedstocks to fulfil the growing demand on jet fuel remains an issue. As such, this study presents a holistic approach for the design of a state-of-the-art hybrid biorefinery that accommodates multiple biomass feedstocks across different categories including energy crops (i.e., Jatropha energy crop), dry biomass (i.e., municipal solid waste) and wet biomass (i.e., livestock manure). A Qatar-based industrial scale biorefinery was modelled in Aspen Plus® considering a pre-defined geospatial distribution of biomass and the optimal biorefinery site in the country. The hybrid system integrated advanced technologies such as hydroprocessing, Fischer-Tropsch, gasification, dry-reforming and hydrothermal liquefaction. While biomass optimal insertion streams were evaluated using a prediction model. Besides, intensive materials, heat, water and power integrations were performed to maximise JBF production, mitigate its environmental impact and control its cost. The system generated 328, 94 and 44 million litres of JBF, gasoline and diesel, respectively. Produced JBF was characterised and found to comply with all international standards. The generated JBF can substitute 15.3 % of Qatar’s jet fuel needs, while it can power around one third of its fleet considering a maximum allowable jet biofuel blend of 50 %. The proposed model achieved a minimum selling price of JBF at 0.43 $/kg, which is 22 % lower than the market price of conventional Jet-A fuel (2019). In addition, the environmental analysis of the model indicated a 41 % mitigation in greenhouse gas emissions achieved by JBF throughout its lifecycle, relative to Jet-A fuel.
In the last few decades, excessive greenhouse gas emissions into the atmosphere have led to significant climate change. Many approaches to reducing carbon dioxide (CO2) emissions into the atmosphere have been developed, with carbon capture and sequestration (CCS) techniques being identified as promising. Flue gas emissions that produce CO2 are currently being captured, sequestered, and used on a global scale. These techniques offer a viable way to encourage sustainability for the benefit of future generations. Finding ways to utilize flue gas emissions has received less attention from researchers in the past than CO2 capture and storage. Several problems also need to be resolved in the field of carbon capture and sequestration (CCS) technology, including those relating to cost, storage capacity, and reservoir durability. Also covered in this research is the current carbon capture and sequestration technology. This study proposes a sustainable approach combining CCS and methane production with CO2 as a feedstock, making CCS technology more practicable. By generating renewable energy, this approach provides several benefits, including the reduction of CO2 emissions and increased energy security. The conversion of CO2 into methane is a recommended practice because of the many benefits of methane, which make it potentially useful for reducing pollution and promoting sustainability.
A series of nFe(III)Ox/ZnO photocatalysts with different Fe contents was prepared by impregnation method, and the samples were characterized by XRD, N2 physisorption, TEM, XPS, UV-vis and PL. It was found that by changing the concentration of Fe species in the impregnation solution, the Fe content in the final sample could be properly adjusted. Within the scope of this work, the loading of Fe does not cause significant changes in the phase, morphology, and porous structure of the ZnO support. However, the electronic state of the catalyst surface was altered considerably, with more O-vacancies were introduced. Fe species enhanced the separation of photo-induced electron-hole pairs, which was responsible to improve the performance of photocatalytic CH4 conversion. Through the optimization of solvent volume, H2O2 concentration and reaction time, the 0.1Fe(III)Ox/ZnO sample showed the best performance over which the yield and selectivity of liquid oxidation products (CH3OH, CH3OOH, HCHO) was 5443 μmol/(gcat·h) and 99%, respectively. Based on radical quenching experiments, it was found that the ·O2⁻ radicals derived from H2O2 played a major role for the activation of CH4 to ·CH3.
Recently, atmospheric non-equilibrium plasma has been proposed as a potential and novel type of "reaction carrier" for the activation and conversion of greenhouse gases (methane and carbon dioxide) into value-added chemicals, due to its unique non-equilibrium characteristics. In this paper, a zero-dimensional plasma chemical reaction kinetic model in CH4/CO2 gas mixture is constructed, with an emphasis on reaction mechanism for plasma dry reforming of methane to syngas and oxygenates. Especially, the effect of the CH4 molar fraction (5%-95%) on plasma dry reforming of methane is investigated. First, the time evolution of electron temperature and density with initial methane content is presented, and the results show that both the electron temperature and electron density vary periodically with the applied triangular power density pulse, and the higher initial methane content in gas mixture is favored for a larger electron temperature and density. Subsequently, the time evolution of number densities of free radicals, ions and molecules at different CH4/CO2 molar fraction are given. The higher the initial methane content, the greater the number densities of H, H⁻, H2, and CH3, leading to insufficient oxygen atoms to participate in the reaction for oxygenates synthesis. The conversions of inlet gases, the selectivities of syngas and important oxygenates are also calculated. The conversion rate of carbon dioxide increases with the increasing methane content, but the conversion rate of methane is insensitive to the variation of methane content. As methane mole fraction is increased from 5% to 95%, the selectivities of important oxygenates (CH3OH and CH2O) are relatively low (<5%), and the selectivity of H2 gradually increases from 13.0% to 24.6%, while the selectivity of CO significantly decreases from 58.9% to 9.7%. Moreover, the dominant reaction pathways governing production and destruction of H2, CO, CH2O and CH3OH are determined, and CH3 and OH radicals are found to be the key intermediate for the production of valuable oxygenates. Finally, a schematic overview of the transformation relationship between dominant plasma species is summarized and shown to clearly reveal intrinsic reaction mechanism of dry reforming of methane in atmospheric non-equilibrium plasma.
This work describes computational thermal analysis process carried out in a biodigester of RICO POLLO SAC., which aims to predict the internal thermal behavior of biogas produced in a lagoon-type anaerobic biodigester covered with a flexible high-density polyethylene membrane (HDPE). Due to the danger of carrying out internal measurements by the amount of H2S present in biogas, which is harmful to health, and the risk of explosiveness (due to presence of flammable gas methane) that some invasive method of measuring properties would represent. Computational simulation provides reliable information. In Chapter 1, information on the company and the work carried out by it is provided. In Chapter 2, the facilities and the biogas generation process are described. In Chapter 3 the properties of biogas are calculated from a typical composition produced by digestion of excreted waste from pig farms, such as specific gravity, pseudocritical properties, compressibility factor, density, dry biogas formation factor, moisture content, H2S content, heat capacity and viscosity of biogas at operating conditions measured in situ. Further, the volume of the confined gas and the external surface area of the HDPE cover are also calculated. In Chapter 4, computational thermal analysis is performed using SOLIDWORKS FLOW SIMULATION, and calculated results are validated with the help of ASPEN HYSYS. Finally, in chapter 5, analysis and post-processing of the graphs to obtain CFDs are presented, and graphs that allow the understanding of the phenomenon that involves heat transfer and fluid flow, in addition to obtaining useful values for biodigester design and biogas management.
Recognizing the emergency of global climate issue, the current fossil fuel‐based economic structure with massive carbon emission is urgent to be transformed. Catalytic conversion of COx, as an emerging alternative technology to produce advanced chemicals and fuels, has received enormous attention. Particularly, photothermal COx conversion, combing the advantages of high‐efficiency and low pollution, has shown the potential for the production of solar fuels and chemicals, and the progress of this field is accelerating. This review summarizes the fundamental of photothermal catalysis as well as the state‐of‐the‐art advances of the photothermocatalytic COx conversion in three main parts that involves COx hydrogenation, water‐gas shift reaction and CO2 reforming of CH4. Moreover, the challenges and perspectives are also briefly discussed, which proposes guidance for future investigation of photothermal C1 conversion and anthropogenic carbon cycle. This article is protected by copyright. All rights reserved.
The development of direct conversion for selective functionalization of inert methane plays an important role in the chemical sciences. Here, we report a photocatalytic approach to successfully convert methane into methyl chloride over NaTaO3photocatalyst using an alkali chloride solution as the chlorine source under ambient conditions, which can overcome disadvantages of toxicity and corrosiveness in the traditional chlorination of methane. Various noble metals and oxide cocatalysts (Pt, Pd, Au, Ag, and Ag2O) and different chloride ion solutions (NaCl, KCl, LiCl, MgCl2, BaCl2, CaCl2, CuCl2, FeCl3, ZnCl2, etc.) are investigated to optimize the photocatalytic chlorination processes. Ag2O/NaTaO3is the best photocatalyst, giving the maximum CH3Cl yield of 152 μmol g⁻¹h⁻¹in aqueous NaCl solutions and an apparent quantum yield of 7.2% under 254 nm monochromatic light irradiation. The target product CH3Cl is verified to be formed by a direct combination of the photoinduced species •CH3and •Cl on the Ag2O surface. This work provides a meaningful approach for the conversion of methane into chloromethane under normal conditions.
In this work, the integrated system of pressurized solid oxide fuel cell (SOFC) and supercritical water reforming of glycerol was proposed. The syngas from the reforming process has high temperature and pressure and thus, it can be used as fuel for the SOFC. The performance of an integrated system was determined through the Aspen Plus simulator in which the electrochemical equations were also included. The developed model was employed to examine the performance of the integrated system with respect to the wider ranges of operation of the reformer and SOFC. In this work, the desired power output of an SOFC stack is set as 10 kW and thus, the area of an SOFC is determined. A smaller area is required as it normally leads to a lower fabrication cost for the SOFC. The simulation results revealed that the smallest SOFC area can be provided when the reformer is operated at 800°C and 240 atm with a ratio of supercritical water to glycerol as 50 whereas the SOFC operation is at 900°C and 4 atm with the current density as 7000 A/m2. Under these operating conditions, the integrated system can provide the cell voltage, required area, fuel utilization, and SOFC efficiency as 1 V, 1.42 m2, 75% and 61%, respectively. From the exergy analysis, it was found that the compressor, heater, and turbine are the highest exergy destruction units whereas the reformer has the lowest exergy destruction, followed by the SOFC stack. In this work, the integrated system of pressurized solid oxide fuel cell (SOFC) and supercritical water reforming of glycerol was proposed. The syngas from the reforming process has high temperature and pressure and thus, it can be used as fuel for the SOFC. The performance of an integrated system was determined through the Aspen Plus simulator in which the electrochemical equations were also included.
Clean hydrogen energy demand comes into picture due to the issues of climate changes and rapid depletion of fossil resources. There are some renewable and nonrenewable sources from which hydrogen is potentially produced. Hydrogen production using renewable sources is getting increasing attraction gradually to obtain clean and sustainable energy. Hydrogen as a secondary source of energy needs different technologies for production. However, hydrogen production technologies used today are highly expensive and require tremendous innovations and technological advancement to make hydrogen energy economically viable. Some clean hydrogen production technologies using renewable sources have been developed, but still their efficiency remains infancy for commercial utilization. In this chapter, a comprehensive overview on major hydrogen production sources and techniques has been systematically reviewed. Emphasis has been given for comparative study over conventional fossil fuel and renewable hydrogen production system from economical point of view. However, deep study concerning innovations and technological improvement for hydrogen production along with their adequate storage and transportation is highly sought after to decrease fossil fuel overdependence and to make the green hydrogen fuel accessibility realistic.KeywordsFossil fuelHydrogen fuelRenewable energyHydrogen economyHydrogen production technologies
Here, we report for the first time the synthesis of a TiO2-based photoanode containing nickel-modified poly(heptazine imide) (Ni-PHI), a polymeric carbon nitride, as well as its application for the methanol oxidation reaction (MOR) under solar simulated and UV illumination. The photoanode was obtained initially as a thin film and the photocurrent response was evaluated in solutions containing Na2SO4 and methanol. For the methanol oxidation reaction under illumination in an acidic medium, an optimal composition of the catalyst was found depositing 30-layers of TiO2-Ni-PHI, which yielded a photocurrent of 11 mA cm⁻² using UV radiation. The material also showed excellent stability, with a decay of approximately 5% of the photocurrent after 100 minutes. The improvement in the performance with Ni-PHI is likely due to the formation of a heterojunction between TiO2 and the graphitic carbon nitride, while nickel sites act through a co-catalysis process possibly driven by in situ generation of nickel active species for MOR like Ni(OH)2|NiOOH. Finally, mechanistic insights from in situ infrared Fourier transform spectroscopy (FTIR) showed that TiO2-Ni-PHI can selectively oxidize methanol to formaldehyde in the dark, while under irradiation of UV light the oxidized products are CO2 and formic acid, a product with high added value.
Steam methane reforming (SMR) has been adopted for the mass production of hydrogen that has been actively used in various industrial processes for several decades. Currently, the demand for hydrogen...
Production of methanol, as a green energy, from syngas is coming into focus. However, natural gas based methanol plants, which are used steam reforming of methane for syngas production, have a high CO2 emission resulting in the global warming. In this study, a novel process for methanol synthesis is proposed to reduce CO2 emission. In this regard, natural gas and flue gas are fed to a parallel-series system with tri and dry reforming of methane for syngas production with the optimized stoichiometric number. Then, the produced syngas is converted to methanol in a reactor. Finally, the produced methanol is purified by two distillation towers. The proposed method is compared to a referenced method in the view of technological, economic and environmental metrics. The techno-economic-environmental analysis of the processes reveals that not only the proposed method, as compared to the referenced one, increases CO2 conversion from 20.93% to 99.22%, but also it is more economical and environmentally friendly. In addition, the global warming potential of the proposed method is almost 60% lower than that for the referenced method due to the lower CO2 emission. Therefore, the proposed method can save above MUS$ 8 a year by CO2 capture.
The possibility of alleviation of methane and carbon dioxide levels in the atmosphere are of major global interest. One of the alternatives that attracts much scientific attention is their chemical utilization, especially because both of these gases are components of the biogas. Thus, the rapid and extensive shale gas development makes them abundant raw materials. The development of an effective catalytic process that could be scaled-up for industrial purposes remains a great challenge for catalysis. As well, understanding of the mechanisms of molecular activation and the reaction pathways over active centers on heterogeneous catalysts needs to be advanced. It has been shown that biogas is a very interesting source of renewable energy. Because of its elevated methane content, biogas has excellent potential, as reflected in its year-over-year rise in production. This is because its manufacturing promotes the use of organic waste, prevents uncontrolled dumping and minimizes atmospheric methane and carbon dioxide emissions. Moreover, its use as an energy source is in some cases an alternative to fossil fuels and can help to minimize energy dependence. Another aspect of interest is that it can be used in situ, allowing agro-livestock farms or small industrial plants to achieve energy self-sufficiency.
Methanol is an important product in chemical industries, having many applications: solvent, fuel and mainly being a feedstock for a large number of industrial processes. As the search for a more sustainable synthesis process grows, the methanol synthesis loop from synthesis gas was studied. In this work, an optimization based on an environmental objective function was developed to reduce the total water consumption of the plant. The methanol synthesis plant and the utility plants of a cooling water system and steam generation cycle were modeled and simulated. A multi-objective optimization study was performed to obtain the optimal trade-off between the economic performance and the reduced water usage. Two distinct scenarios were considered: the integrated use of the steam produced in the reactor cooling and its exporting for profits. The results show that the optimized green design can reduce up to 18% of the water consumed by the process. The exported steam case study provided more economic benefits, while the integrated steam case attained a smaller water consumption indicator.
Graphical abstract
Ni-based catalysts are highly efficient in methane-reforming processes. In the particular case of methane reforming in the presence of carbon dioxide, or dry reforming of methane (DRM), it is necessary to modify and control the initial properties of the catalyst to confer on it resistance to carbon deposition in particular, and to sintering of the Ni metal particles. In this regard, catalytic supports and promoters of different natures have been proposed. Likewise, the addition of small amounts of noble metals to avoid oxidation of the Ni active phase during the reforming reaction has been proposed. Catalyst preparation methods have also been identified as being of particular interest, since they can affect the structure of the Ni metal particles. In this review, the thermodynamic and kinetic aspects of the dry reforming of methane reaction are presented first. The most recent developments in synthetic methods (impregnation, sol-gel, co-precipitation, equilibrium deposition filtration, atomic layer deposition, non-thermal glow discharge plasma, multi-bubble sonoluminescence, “core-shell” structure) aimed at maximizing the dispersion and thermal resistance of Ni particles are then discussed and compared. The catalytic supports used to promote dispersion of the active metallic phase, the oxygen-storage capacity, and the metal/support interaction are also described. The review then addresses the fact that both the nature of the support and the addition of promoters and other metallic phases that modify the surface properties can control the interaction between the metal and the support, the electronic density of the active phase, and the degree of Ni reduction. Finally, new lines of research focused on the DRM process to make the reaction conditions milder and favor the process at low temperatures are also summarized.
Aware of the uncontrolled increase in greenhouse gas emissions, and designated as the main contributor, carbon dioxide (CO2), until now, has been the hottest point in research on gaseous waste management. Thus, the use of CO2 is attracting more and more interest in renewable fuel generation processes. In this sense, this chapter aims to compile a wide range of applications for the use of CO2 as an essential raw material in the conversion of fuels. Beyond briefly discussing the technologies for direct chemical conversion of CO2 for the generation of alternative fuels, our approach focused on examining in more detail the biological use of CO2, through microalgae-based processes. Finally, the chapter presents some recommendations for the future exploration of CO2 generation technologies for fuels.
DESCRIPTION
The depletion of crude oil reserves has created interest to produce transportation fuels such as petrol and diesel from renewable biomass. The conversion of biomass to liquid fuels is a two-step process. In the first step, the biomass is converted to synthesis gas (A mixture of carbon monoxide and hydrogen) via gasification. In the second step, synthesis gas is converted to liquid fuels via Fischer-Tropsch Synthesis (FTS) using a suitable catalyst such as iron, cobalt and ruthenium on supports such as alumina, silica and carbon-based supports such as activated carbon, carbon nanofibers, and carbon nanotubes. The FTS reaction is highly exothermic. The selectivity to liquid fuels depends on reactor type, catalyst and operating conditions. This can be improved by removing the heat produced at a faster rate. The FTS is generally carried out in fixed bed, fluidized bed and slurry reactors. The conventional reactors suffer from effective removal of heat. Microchannel reactors are efficient in removing the heat produced due to very high heat transfer coefficient (> 5000 W/m²K) and high surface area for heat transfer. This book chapter discusses the synergistic effect of carbon nanostructures as supports in microchannel reactors for efficient conversion of biomass-derived syngas to engine-grade fuels.
Recent advances in machine learning (ML) have witnessed a profound interest and application in the domain of waste to energy. However, their black-box nature renders challenges for ubiquitous acceptance. To address this issue, we developed a novel and first-of-its-kind hybrid data-driven and mechanistic modelling approach for hydrothermal gasification (HTG) of wet waste, in which a gradient boost regressor (GBR) integrated optimization model was first developed to predict and optimize the yield of syngas from HTG of wet waste, and then the predictions of the GBR model were validated and interpreted via mechanistic simulations in Aspen Plus. Results showed that the GBR model had a prediction performance with test R2 > 0.90. GBR-based feature analysis identified that reaction temperature and feedstock solid content were the two significant features necessary to achieve high H2 yield in syngas. Moreover, the GBR-based optimization provided optimal process conditions for H2-rich syngas production, which was validated over mechanistic simulations in Aspen Plus with an error of less than 20%. Interpretation from the mechanistic simulation revealed that steam and dry methane reforming and CO2 methanation were the most significant reactions in the overall HTG process, responsible to produce H2-rich syngas. Integrated modelling approach as presented in this study shows how data-driven and mechanistic models complement each other and can aid the acceleration of experimental design of HTG by ML in general.
Today, bi - reforming of methane is considered as an emerging replacement for the generation of high-grade synthesis gas (H2:CO = 2.0), and also as an encouraging renewable energy substitute for fossil fuel resources. For achieving high conversion levels of CH4, H2O, and CO2 in this process, appropriate operation variables such as pressure, temperature and molar feed constitution are prerequisites for the high yield of synthesis gas. One of the biggest stumbling blocks for the methane reforming reaction is the sudden deactivation of catalysts, which is attributed to the sintering and coke formation on active sites. Consequently, it is worthwhile to choose promising catalysts that demonstrate excellent stability, high activity and selectivity during the production of syngas. This review describes the characterisation and synthesis of various catalysts used in the bi-reforming process, such as Ni-based catalysts with MgO, MgO-Al2O3, ZrO2, CeO2, SiO2 as catalytic supports. In summary, the addition of a Ni/SBA-15 catalyst showed greater catalytic reactivity than nickel celites; however, both samples deactivated strongly on stream. Ce-promoted catalysts were more found to more favourable than Ni/MgAl2O4 catalyst alone in the bi-reforming reaction due to their inherent capability of removing amorphous coke from the catalyst surface. Also, Lanthanum promoted catalysts exhibited greater nickel dispersion than Ni/MgAl2O4 catalyst due to enhanced interaction between the metal and support. Furthermore, La2O3 addition was found to improve the selectivity, activity, sintering and coking resistance of Ni implanted within SiO2. Non-noble metal-based carbide catalysts were considered to be active and stable catalysts for bi-reforming reactions. Interestingly, a five-fold increase in the coking resistance of the nickel catalyst with Al2O3 support was observed with incorporation of Cr, La2O3 and Ba for a continuous reaction time of 140 h. Bi-reforming for 200 h with Ni-γAl2O3 catalyst promoted 98.3% conversion of CH4 and CO2 conversion of around 82.4%. Addition of MgO to the Ni catalyst formed stable MgAl2O4 spinel phase at high temperatures and was quite effective in preventing coke formation due to enhancement in the basicity on the surface of catalyst. Additionally, the distribution of perovskite oxides over 20 wt % silicon carbide-modified with aluminium oxide supports promoted catalytic activity. NdCOO3 catalysts were found to be promising candidates for longer bi-reforming operations.
Abundant and affordable methane is not only high‐quality fossil energy, but also the raw material for the synthesis of value‐added chemicals. Solar‐energy‐driven conversion of methane offers a promising approach to directly transform methane to valuable energy sources under mild conditions, but remains as a grand challenge currently. In this Review, recent advancements of photocatalytic conversion of methane are systematically summarized. Insights into the construction of effective semiconductor‐based photocatalysts from the perspective of light‐absorption units and active centers are proposed and discussed in detail. Moreover, photocatalytic performances of methane conversion over various catalysts are also presented and classified by oxidant systems. Lastly, challenges and future perspectives concerning mechanistic study and practical application of photocatalytic methane oxidation are introduced.
Abundant and affordable methane is not only high-quality fossil energy, but also the raw material for the synthesis of value-added chemicals. Solar-energy-driven conversion of methane offers a promising approach to directly transform methane to valuable energy sources under mild conditions, but remains as a grand challenge currently. In this Review, recent advancements of photocatalytic conversion of methane are systematically summarized. Insights into the construction of effective semiconductor-based photocatalysts from the perspective of light-absorption units and active centers are proposed and discussed in detail. Moreover, photocatalytic performances of methane conversion over various catalysts are also presented and classified by oxidant systems. Lastly, challenges and future perspectives concerning mechanistic study and practical application of photocatalytic methane oxidation are introduced.
Methane reforming with the application of combined H2O and CO2 is appropriately known as bi-reforming of methane (BRM). The method is promising because it has potential to deliver an alternative energy source and is effective in mitigating greenhouse gases (GHGs). In this study, Ni-based catalyst with 5 wt% supported Al2O3 and various Ca (2–4 wt%) loadings were prepared by following the wetness impregnation method. Characterization techniques, including Brunauer-Emmett-Teller (BET) and X-ray diffraction (XRD), were applied to observe prepared catalysts' structural morphology and physicochemical properties. Based on XRD analysis, the CaO-4wt% catalyst exhibited higher crystallinity than the CaO-2wt% catalyst, enabling it to withstand greater forces and take longer to deteriorate. To improve the catalyst activity, CaO was added as a promoter that altered the contact between Ni and Al2O3 and modified the properties of the catalysts for an excellent activity. A fixed-bed continuous reactor with a feed ratio CH4: CO2: H2O of 3:1:2 at 1073 K was used to observe the catalysts performance. BRM catalytic reaction at 800 °C having Ni-4CaO/Al2O3 catalyst, proved greatly in converting CH4 and CO2 with 79.6% and 87.2% respectively during the 6 h reaction.
Fe-ZSM-5 is an active catalyst for the selective oxidation of methane with H2O2 in liquid water. To prepare the active Fe-ZSM-5 catalyst, the effect of the Fe precursor on the catalytic performance was examined. Additionally, two preparation methods, wet impregnation (WI) and ion-exchange (IE), were also applied. The prepared catalysts were characterized using various techniques, such as nitrogen physisorption, X-ray diffraction, UV–Vis spectroscopy, and Fourier-transform infrared (FTIR) spectroscopy after NO adsorption (NO-FTIR). Fe-ZSM-5 prepared from FeCl2 appears to be the most active among the Fe-ZSM-5 catalysts prepared from FeCl2, FeSO4, Fe(CH3CO2)2, FeCl3, Fe2(SO4)3, Fe(C5H7O2)3, and Fe(NO3)3 using the WI method. For Fe-ZSM-5 catalysts prepared using the IE method, divalent Fe precursors, such as FeSO4, FeCl2, and Fe(CH3CO2)2, are better than trivalent Fe precursors, such as Fe2(SO4)3, FeCl3, and Fe(NO3)3, in terms of catalytic activity. The active catalyst has the dominant extra-framework Fe²⁺ species probed with UV–Vis spectroscopy and NO-FTIR.
In this work, we are interested in acid gas (H2S and CO2) removal by aqueous solutions of alkanolamine. The first part of the article deals with the development of the experimental apparatus used to determine the partial acid gas pressure as a function of acid gas loading in the reactive liquid phase with the synthetic method. New measurements on water + diethanolamine + CO2 and water + diethanolamine + H2S systems were performed. The second part concerns the modelling of such data. The model used couples the chemical reactions in liquid phase with the phase equilibrium. We use the electrolyte NRTL model for the liquid phase and the Peng and Robinson equation of state to describe the vapour phase. The parameters of the electrolyte NRTL model are determined on experimental acid gas partial pressure data of the studied systems.
Fuel cell development has seen remarkable progress in the past decade because of an increasing need to improve energy efficiency as well as to address concerns about the environmental consequences of using fossil fuel for producing electricity and for propulsion of vehicles [1]. The lack of an infrastructure for producing and distributing Hâ has led to a research effort to develop on-board fuel processing technology for reforming hydrocarbon fuels to generate Hâ [2]. The primary focus is on reforming gasoline, because a production and distribution infrastructure for gasoline already exists to supply internal combustion engines [3]. Existing reforming technology for the production of Hâ from hydrocarbon feedstocks used in large-scale manufacturing processes, such as ammonia synthesis, is cost prohibitive when scaled down to the size of the fuel processor required for transportation applications (50-80 kWe) nor is it designed to meet the varying power demands and frequent shutoffs and restarts that will be experienced during normal drive cycles. To meet the performance targets required of a fuel processor for transportation applications will require new reforming reactor technology developed to meet the volume, weight, cost, and operational characteristics for transportation applications and the development of new reforming catalysts that exhibit a higher activity and better thermal and mechanical stability than reforming catalysts currently used in the production of Hâ for large-scale manufacturing processes.
A mixed metal oxide substrate consisting of CeO2 and Gd2O3 (CGO) at a ratio of 4:1 Ce/Gd was synthesized by either a glycine-nitrate process or coprecipitation of metal salt precursors followed by calcination at 600°-1000°C. A group VIII transition metal selected from the noble metals (Pt, Ru, or Rh) or non-noble metals (Co or Ni) was loaded onto the CGO substrate using the incipient wetness technique. Metal loadings ranged from 0.1 to 1 wt %. These materials were evaluated for autothermal reforming of isooctane, which is used as a single component surrogate for gasoline. For all metals, the conversion of isooctane was > 99% at above 700°C. Below 600°C, the H2 yields for Ru, Rh, and Ni were significantly higher than the H2 yields for Pt or Co. Rh, Ru, and Ni were more active than Pt or Co for steam reforming. The primary reaction products were H2, CO, CO2, and CH4. The yields of H2 and CO increased with increasing temperature. The CO2 yield decreased with increasing temperature due to either the water-gas shift reaction, which favors the reactants (H2O + CO) as the temperature increases, or possibly CO2 reforming.
In principle, syngas (primarily consisting of CO and H2) can be produced from any hydrocarbon feedstock, including: natural gas, naphtha, residual oil, petroleum coke, coal, and biomass. The lowest cost routes for syngas production, however, are based on natural gas, the cheapest option being remote or stranded reserves. Economic considerations dictate that the current production of liquid fuels from syngas translates into the use of natural gas as the hydrocarbon source. Nevertheless, the syngas production operation in a gas-to-liquids plant amounts to greater than half of the capital cost of the plant. The choice of technology for syngas production also depends on the scale of the synthesis operation. Syngas production from solid fuels can require an even greater capital investment with the addition of feedstock handling and more complex syngas purification operations. The greatest impact on improving the economics of gasto liquids plants is through 1) decreasing capital costs associated with syngas production and 2) improving the thermal efficiency with better heat integration and utilization. Improved thermal efficiency can be obtained by combining the gas-to-liquids plant with a power generation plant to take advantage of the availability of low-pressure steam.
The kinetics of the CO2 reforming of methane was investigated on a Ni−Rh−Al2O3 catalyst. Twenty-seven mechanistic models were considered and fitted to the experimental data by numerically integrating the rate equation of the dry reforming of methane reaction. A thermodynamic analysis showed that the reverse water gas shift reaction operates in or very close to thermodynamic equilibrium. A strategy of model discrimination and parameter estimation led to a model that considers CO2 molecular adsorption, CH4 dissociative adsorption, and its surface chemical reaction as the rate-determining step. The parameter estimates in the resulting model are statistically significant and thermodynamically consistent.
The WAR algorithm, a methodology for determining the potential environmental impact (PEI) of a chemical process, is presented with modifications that account for the PEI of the energy consumed within that process. From this theory, four PEI indexes are used to evaluate the environmental friendliness of a process design. These indexes are used in a comparative manner in the process design stage to help minimize the environmental impact of that process. Eight PEI categories (four global and four toxicological) are used in the evaluation of the PEI indexes. Details for relating these categories to known or measured quantities are also presented. An illustrative case study is presented which provide an example for the intended use of the WAR algorithm within the scope of process design and simulation.
CARBON DIOXIDE is nontoxic, nonflammable, and essentially free for the taking. Those attributes make it sound like CO 2 could be a great feedstock for making commodity chemicals, fuels, and materials—and it already is playing that role for a few applications. But there are a few catches. One is that CO 2 is very stable, which means it takes extra effort to activate the molecule so it will react. Another reality check is that so much of the unwanted greenhouse gas is escaping into the atmosphere as a consequence of burning fossil fuels that even shunting millions of tons of it each year into making chemicals won't have much of a bearing on the gas's global warming threat. So what's one to do with CO 2 ? C&EN asked that question of a number of chemists and chemical engineers. These investigators were unanimous on the scope of the CO 2 problem. They understand that technology to capture ...
Worldwide demand for clean, reliable and affordable energy has never been greater. New technologies are needed to produce more oil and natural gas from remote or "stranded" locations. Gas to Liquids (GTL) conversion is an umbrella term for a group of technologies that can create liquid hydrocarbon fuels from a variety of feedstocks. The conversion of natural gas into liquid fuels is an attractive option to commercialize abundant gas reserves. GTL, with virtually unlimited markets, offers a new way to unlock large gas reserves, complementary to other traditional technologies such as Liquefied Natural Gas (LNG) and pipelines. GTL has the potential to convert a significant percentage of the world's estimated proved and potential gas reserves which today holds little or no economic value. In essence, GTL uses catalytic reactions to synthesize complex hydrocarbons from carbon monoxide and hydrogen. There has been significant improvement in reactor design and technology over the last decade. Fundamental research is essential to achieve new and improved catalysts. Such research is concerned with establishing reaction mechanisms, in understanding the surface science of catalysis and catalyst structure performance relationships, as well as searching for new techniques for scientific design of catalysts.
The kinetics of methane steam reforming over a Ru/ZrO2 catalyst was studied at 1.3 bar total pressure and in the temperature range 425–575 °C. These data were fitted by combining a reactor model with a series of kinetic models. The best fit was obtained by a model with methane dissociative adsorption as the rate limiting step and with CO and H adspecies partly blocking the active sites. The Ru/ZrO2 catalyst was characterized by TEM and H2 chemisorption. By comparison of ex situ and in situ TEM, it is evident that Ru particles with diameters of <2 nm are difficult to observe with ex situ TEM due to oxidation when exposed to air.
Dry reforming of methane by carbon dioxide was investigated over La2−xSrxNiO4 perovskite-type oxides. The catalysts exhibited promising activity and very good stability at equimolar methane and carbon dioxide feed. Small amounts of Sr increase carbon deposition on the catalyst surface but addition of higher amounts of Sr suppresses coking and increases the CO2 conversion and the CO production. The kinetics of the reaction over LaSrNiO4 was also investigated by variation of the partial pressures of the reactants. The experimental data were fitted using the semi-empirical power rate law equation as well as using a Langmuir–Hinshelwood kinetic model. The activation energy for methane consumption estimated from both interpretations was ∼41 kJ/mol. Lower values of activation energy estimated for carbon dioxide elimination, when compared to values obtained for methane consumption, correspond to higher reaction rate of CO2 in comparison to CH4 reaction rate.
Absorption of acid gases such as CO{sub 2} and H{sub 2}S from natural and process gases is of great industrial importance. The kinetics of the reaction between CO{sub 2} and aqueous diethanolamine (DEA) were estimated over the temperature range of 293--343 K from absorption data obtained in a laminar-liquid jet absorber. The absorption data were obtained over a wide range of DEA concentrations and for CO{sub 2} partial pressures near atmospheric. A rigorous numerical mass-transfer model based on penetration theory in which all chemical reactions are considered to be reversible was developed and used to estimate kinetic rate coefficients from the experimental absorption data. The kinetic data were found to be consistent with the zwitterion mechanism. The scarce zwitterion rate coefficient estimates reported in the literature are in fair agreement with the results of this work.
Kinetic studies of COâ reforming of methane over a highly active Ni/La/α-AlâOâ catalyst were performed in an atmospheric microcatalytic fixed-bed reactor. The reaction temperature was varied between 700 and 900 C, while partial pressures of COâ and CHâ ranged from 16 to 40 kPa. From these measurements kinetic parameters were determined; the activation energy amounted to 90 kJ/mol. The rate of COâ reforming was described by applying a Langmuir-Hinshelwood rate equation. The developed kinetics was interpreted with a two-phase model of a fluidized bed. The predictions for a bubbling-bed reactor operated with an undiluted feed (CHâ:COâ = 1:1) at 800 C showed that, on an industrial scale, significantly longer contact times (H{sub mf} = 7.8 m, m{sub cat}/V{sub STP} = 31.8 g·s·ml) are necessary for achieving thermodynamic equilibrium (X{sub CHâ} = 88.2%, X{sub COâ} = 93.6%). The performance of the reactor was strongly influenced by the interphase gas exchange: the highest space time yields were obtained for small particles (D{sub p} = 80 μm).
Auto-thermal reforming of methane, combining partial oxidation and reforming of methane with CO2 or steam, was carried out with Pt/Al2O3 Pt/ZrO2 and Pt/CeO2 catalysts, in a temperature range of 300–900°C. The auto-thermal reforming occurs in two simultaneous stages, namely, total combustion of methane and reforming of the unconverted methane with steam and CO2, with the O2 conversion of 100% starting from 450°C. For combination with CO2 reforming, the Pt/CeO2 catalyst showed the lowest initial activity at 800°C, and the highest stability over 40 h on-stream. This catalyst also presented the best performance for the reaction with steam at 800°C. The higher resistance to coke formation of the catalyst supported on ceria is due to the metal-support interactions and the higher mobility of oxygen in the oxide lattice.
Nanocomposite Ni/ZrO2-AN catalyst consisting of comparably sized Ni metal and ZrO2 nanoparticles is studied in comparison with zirconia- and alumina-supported Ni catalysts (Ni/ZrO2-CP and commercial Ni/Al2O3-C) for steam reforming of methane (SRM) and for combined steam and CO2 reforming of methane (CSCRM). The reactions are performed under atmospheric pressure with stoichiometric amounts of H2O and CH4 or (H2O+CO2) and CH4 at 1073K. Under a wide range of methane space velocity (gas hourly space velocity of methane GHSVCH4=12,000–96,000ml/(hgcat.), the nanocomposite Ni/ZrO2-AN catalyst always shows higher activity and stability for both SRM and CSCRM reactions. The two supported Ni catalysts (Ni/ZrO2-CP and Ni/Al2O3-C) exhibit fairly stable catalysis under low GHSVCH4 but they are easily deactivated under high GHSVCH4 and become completely inactive when they are reacted for ca.100h at GHSVCH4=48,000ml/(hgcat.). The CSCRM reaction is carried out with different H2O/CO2 ratios in the reaction feed while keeping the molar ratio (H2O+CO2)/CH4=1.0, the results prove that the nanocomposite Ni/ZrO2-AN catalyst can be highly promising in enabling a catalytic technology for the production of syngas with flexible H2/CO ratios (ca. H2/CO=1.0–3.0) to meet the requirements of various downstream chemical syntheses.
Experimental work has been carried out on the mixed reforming reaction, i.e., simultaneous steam and CO2 reforming of methane under a wide range of feed compositions and four different reaction temperatures from 700 °C to 850 °C using a commercial steam reforming catalyst. The experiments were conducted for a CO2/CH4 ratio from 0 to 2 and a steam to methane ratio from 3 to 5. The effect of CO2/CH4 ratio on the exit H2/CO ratio and the conversions of the reactants indicate that the dry reforming reaction is dominant under increased carbon dioxide in the feed. Steam reforming of typical steam hydrogasification product gas consisting of CO, H2 and CO2 in addition to steam and methane has also been investigated. The H2/CO ratio of the product synthesis gas varies from 4.3 to 3.7 and from 4.8 to 4.1 depending on the feed composition and reaction temperature. The CO/CO2 ratios of the synthesis gas varied from 1.9 to 2.9 and 2.0 to 3.3. The results are compared with simulation results obtained through the Aspen Plus process simulation tool. The results demonstrate that a coupled steam hydrogasification and reforming process can generate a synthesis gas with a flexible H2/CO ratio from carbon-containing feedstocks.
The solubility of methane and ethane in monoethanolamine and diethanolamine solutions is measured. The experimental procedures used to collect the data are presented along with selected data and graphs showing effects of temperature, amine concentration, and acid gas content. The solubilities of these hydrocarbons n the amine solutions are about the same as their solubility in an equal weight or volume of water. However, the type and concentration of amine, temperature, and presence of hydrogen sulfide and carbon dioxide affect the methane and ethane solubility.
In this work, the potential for the catalytic partial oxidation (CPOX) of methane (CH4) to produce synthesis gas (H2 and CO) was studied both experimentally and thermodynamically at a fixed pressure (1 bar) and electric power (0.3 kW). The investigations were performed in a partially adiabatic plasma-assisted (nonthermal) Gliding Arc (GlidArc) reactor, using a Ni-based catalyst. Two cases were studied: in the first, normal air (molar ratio of O2/N2 = 21/79) was used, whereas enriched air (O2/N2 = 40/60) was utilized in the second. The individual effect of the O2/CH4 molar ratio, gas hour space velocity (GHSV), and bed exiting temperature (Texit) was studied for both cases. The main trends of the CH4 conversion, the synthesis gas yield, and the thermal efficiency of the reactor based on the LHV (lower heating value) were analyzed and compared, and any deviations from equilibrium could be explained by temperature gradients and an irregular gas flow. In the findings from the studies, the results revealed that an H2/CO ratio of 2 could be obtained. For the normal air case, an optimal value of the O2/CH4 molar ratio of 0.7, a GHSV of 1.8 NL/(gcat.h), and a maximum temperature (Tmax) of 1065 °C were good reforming choices, whereas for enriched air, these values were 0.7, 1.8, and 1105 °C, respectively.
In the design of chemical/energy production systems, a major challenge is how to quantify the sustainability of the systems. Concerns on economic return and environmental impacts have been well received by researchers and practitioners. However, the irreversibility of the process has not been taken into consideration yet. Based on the first and second laws of thermodynamics, exergy analysis allows accounting for irreversibility in the process and provides a detailed mechanism for tracking the transformation of energy and chemicals. Sustainability assessment in the societal dimension is mostly a “soft” activity, as the aspects to be considered and the method of evaluation are frequently subjective. How to assess the societal impact of a process in the early design stage remains as a challenging issue. This paper will present a sustainability assessment method incorporating economic, environmental, efficiency, and societal concerns. The efficiency assessment is conducted through exergy analysis, while the societal concerns are measured by an enhanced inherent safety index method. In conjunction with a multicriteria decision-analysis method, this methodology will provide critical guidance to the designers. The efficacy of this methodology will be demonstrated through a case study on biodiesel production processes. The results show that the new heterogeneous catalyst process performs better than the traditional homogeneous process in every dimension.
The true kinetics of methane steam reforming was measured in powder of Ni/Al2O3 catalyst (“Octolyst 1001” from Degussa) at different temperatures (733–890 K) for several operating conditions. New reaction rate constants were determined for this catalyst. The observed reaction rate was measured on catalyst extrudates to determine diffusion effects within the porous structure of the particle. A non-isothermal model with diffusion was used to determine effectiveness factors for each reaction. The objective was to measure all necessary data to model the performance of the catalyst in a Sorption Enhanced Reaction Process (SERP) for H2 production with in situ CO2 capture.
On a mesuré la cinétique réelle du reformage à la vapeur de méthane sur un catalyseur Ni/Al2O3 sous forme de poudre (« Octolyst 1001 » de Degussa) à différentes températures (733–890 K) dans plusieurs conditions d'exploitation. De nouvelles constantes de vitesse de réaction ont été déterminées pour ce catalyseur. On a mesuré la vitesse de réaction observée sur des extrudats de catalyseur pour déterminer les effets de diffusion à l'intérieur de la structure poreuse de la particule. On a utilisé un modèle non isothermique avec diffusion pour déterminer les facteurs d'efficacité de chaque réaction. L'objectif consistait à mesurer toutes les données nécessaires pour modéliser la performance du catalyseur dans un procédé de réaction améliorée de sorption pour la production de H2 avec captage in-situ de CO2.
Intrinsic rate equations were derived for the steam reforming of methane, accompanied by water-gas shift on a Ni/MgAl2O4 catalyst. A large number of detailed reaction mechanisms were considered. Thermodynamic analysis helped in reducing the number of possible mechanisms. Twenty one sets of three rate equations were retained and subjected to model discrimination and parameter estimation. The parameter estimates in the best model are statistically significant and thermodynamically consistent.
Kinetics of methane steam reforming over a commercial nickel-based catalyst and over an innovative rhodium-perovskite catalyst of formula BaRhxZr(1−x)O3 was studied at atmospheric pressure and in the temperature range 723–1023 K. Extensive experimental runs were firstly carried out in a micro-reactor, with the catalysts in powder form, to evaluate their performances in steam methane reforming process. The behaviour of rhodium-perovskite catalyst was analyzed as function of steam-to-methane ratio and temperature, comparing the obtained performances of this catalyst with that showed by the commercial nickel-based one. Rhodium-perovskite catalyst shows higher activity for steam methane reforming reaching methane conversions higher than those obtained with the nickel-based catalyst and closer to the thermodynamic equilibrium value. Based on a detailed review of the kinetic models proposed for steam reforming, the experimental data were fitted using a simple kinetic model where the conversion of methane is proportional only to the methane partial pressure. Good agreement was obtained between the experimental data and the kinetic model prediction.Graphical abstractView high quality image (57K)Research highlights▶ Rh-perovskite catalyst has higher activity in SMR than commercial Ni-based catalyst. ▶ The found activation energies are 69.1 kJ/mol for Rh and 96.1 kJ/mol for Ni. ▶ Results confirm SMR is first order and zero order for CH4 and steam, respectively.
The mechanism for the catalytic partial oxidation of CH 4 on Rh-coated α-Al 2 O 3 foam monoliths was investigated by measuring species and temperature profiles along the catalyst axis and comparing them with numerical simulations. A thin quartz capillary connected to a quadrupole mass spectrometer was moved through the catalyst with a spatial resolution of ∼0.3 mm. Profiles were measured under autothermal operation for C/O ratios of 0.7, 1.0 and 1.3. The influence of the flow rate (5 vs. 10 l min −1) was studied for syngas stoichiometry (C/O = 1). Numerical simulations were performed with a 38 step surface mechanism using both a porous 2D-model with mass and heat transfer and a simple plug-flow model. The experimental profiles reveal complete O 2 conversion within 2 mm of the catalyst entrance for all C/O ratios and flows. H 2 and CO are formed partly in the oxidation zone and partly after O 2 is fully converted by steam reforming. CO 2 is formed in small amounts in the oxidation zone and remains constant thereafter, except for C/O = 0.7, where some water gas shift is observed. CO 2 reforming does not occur under the experimental conditions. Based on the experimental findings, a two-zone picture of the reaction mechanism is proposed. The 2D numerical simulations and the measured profiles agree qualitatively for all experimental conditions. Quantitative agreement is best for syngas stoichiometry (C/O = 1.0) at 5 and 10 l min −1 flow rate. Some quantitative differences are observed for C/O = 0.7 and 1.3. The plug flow model is for all conditions inferior to the 2D model. The importance of spatial profiles for mechanism and reactor model validation is highlighted.
Several Ni-based catalysts supported on a mixture of MgO, La2O3, and Al2O3 were prepared. The catalytic performance in the steam reforming of m-cresol was evaluated. In the investigation of the effect of Ru loading added to the Ni-catalyst, it was found that the presence of Ru strongly enhances the catalytic performance of the Ni-based catalyst when increasing Ru loading up to 2 wt%. Effect of Ni loading to the Ru-based catalyst system was also investigated. It was found that the addition of nickel to the Ru-based catalyst up to 15 wt% enhanced significantly the catalytic activity of the catalyst. The lifetime of the Ru–Ni catalysts in the reforming of m-cresol was further tested at 750 °C. In agreement with general observations of the use of Ni monometallic catalyst, deactivation of the catalyst due to the carbon deposition reaction already occurred in the reforming of the oxygenated compound. On the other hand, a reasonable high resistant on the carbon deposition in the reforming of m-cresol was given by the 2 wt% Ru–15 wt% Ni catalyst system. An effort in improving the strength of the catalyst support with this catalyst system was also conducted, and the catalyst showed significant increase in the stability of the reforming of oxygenated aromatic compound.
Steam reforming, CO2 reforming and simultaneous steam and CO2 reforming reactions of methane for its conversion into syngas (H2 and CO) over NiO/MgO/SA-5205 catalyst (prepared by depositing NiO on MgO precoated SA-5205 support) have been investigated at different process conditions. In some cases O2 was present in the feed, while in other cases it was not. The catalyst has been characterised by its temperature programmed reduction and also, after its reduction, by temperature programmed desorption of hydrogen. It showed high activity and selectivity in the above methane-to-syngas conversion reactions at low contact times. The H2/CO product ratio in the simultaneous methane conversion reactions showed a strong dependence on the feed composition; such dependence is increased by increasing the concentration of steam relative to that of O2 and/or CO2 in the feed. In the oxy-steam and/or CO2 reforming reactions, there is a direct coupling of the exothermic and endothermic reactions and hence these processes over the catalyst occur in the most energy efficient and safe manners, requiring little or no external energy. The net heat of reactions in these processes is strongly influenced by the reaction temperature and/or CH4/O2 ratio in the feed. In the simultaneous steam and CO2 reforming of methane in both the presence and absence of O2, it is possible to convert methane into syngas with high conversion (above 97%) and 100% selectivity for both CO and H2.
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