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CONVERGE: CarbON Valorisation in Energy-efficient Green fuels
- Giampaolo Manzolini
- Ježovič Tomáš
- Berend VREUGDENHIL
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The tetralin hydrocracking process into benzene, toluene, and xylenes (BTX) was investigated over metal-modified (Ga, Nb, Ni, NiMo, Sn, W, Zr or H3 [P(W3O10)4])/ZSM-5 zeolite catalysts without sulfidation procedures, mechanism was analyzed, and compared with a pristine microporous material in a packed bed reactor under applied atmospheric pressure (p). This experimental study presents an investigation of the metal-promoted ZSM-5 for the BTX production under the ambient p for the first continuously-operated time. It is demonstrated that metal-wise there are no significant improvements in the formation of BTX. The yield of 43.1 mol% towards BTX over the parent HZSM-5 (SiO2/Al2O3 = 30) at 420 °C after 4 h on time on stream (TOS) was achieved, while methane, ethylene, ethane, propylene and propane were main gas products. The outstanding functional performance of HZSM-5 was mainly ascribed to structure, its high dealkylation and a measured large amount of the solid surface area in tandem with the porosity, protonating total Brønsted (BAS)/Lewis (LAS) acidity and BAS/LAS ratio. However, BTX dropped drastically with increasing TOS due to coke. It was found that HZSM-5 was the most affected within studied reaction conditions, but could be easily regenerated with preserving realistic catalytic chemistry. The pathway of cracking was proposed. Simultaneously, the 5 wt%Zr/ZSM-5 catalyst possessed the highest selectivity (SBTX = 24.2 mol%; TOS = 25 h; 370 °C) due to the low diffusion thermomigration of the Zr species into framework compared to parent zeolite under the same reaction conditions after a long TOS. Influence of metal loading on the activity of ZSM-5 zeolite was systematically studied and the complex relationship between physicochemical properties and catalytic activity of bifunctional catalysts was observed. All these findings shed light, on how the incorporation of different metals affects BTX selectivity.
In this experimental study, various NiMo-promoted (as follows: H-beta, H-mordenite, H-USY, H-Y, and H-ZSM-5) catalysts were prepared, tested, and compared with pristine zeolites for the purpose of the gas phase hydrocracking, hydrogenation, and isomerization in a packed bed reactor at 370 °C under atmospheric relative pressure. 5 wt.% naphthalene/95 wt.% 1-methylnaphthalene were selected as biomass tar model molecule compounds, based on real chemical compositions. A series of material characterization techniques were applied to determine the physical structural, morphological, textural, redox, and acidic properties of synthesized catalysts. An outstanding catalytic activity and stability were found over the 2.5 wt.% Ni–2.5 wt.% Mo/ZSM-5 with high carbon deposition resistance, 2-methylnaphthalene selectivity (96.0 mol.%) in the liquid with the products with a yielded total conversion of 96.3 mol.% after an 18 h time on stream, where ethylene/propane were main (94.2 wt.%). The latter can be attributed to the presence of mesopore volume/surface area, existing boundary interface, the amount of medium/strong acid sites, and the synergetic interaction phenomena between metal atom species/supports. Attention should be paid to particle size dimensions, diameters and acidity, which facilitated poly-aromatic hydrocarbon removal. Considering particular obtained distributions, intermediates reaction pathway was proposed. Cracking, synthetic ring opening, alkylation, condensation and disproportionation were additionally involved. Results were consistent with the occurrence of two competing mechanisms, a monomolecular, as well as a bimolecular one.
Gas-phase conversion of a model mixture of biomass tar (5 wt% naphthalene and 95 wt% of 1- methylnaphthalene) into 2-methylnaphthalene liquid product and ethylene and propane gas mixture was carried out over different zeolites and metal promoted zeolites in a packed-bed reactor for the first time. In the present work, a series of MFI (H-ZSM-5), BEA (H-Beta), FAU (H-Y, H-USY), and MOR (H-Mordenite) zeolites were investigated. The effect of Ni metal addition on the promotion of parent zeolite catalysts was studied. The most successful catalysts were characterized by BET, ICP-AES, XRD, HRSEM, STEM-HAADF, and STEM-BF with EDXS, NH3-TPD, H2-TPR, TGA, and pyridine-DRIFT techniques. The superior performance in comparison to the other studied catalysts was established over the 5 wt%Ni/H- ZSM-5 (SiO2/Al2O3 = 30) with 96.2 mol% of selectivity to 2-methylnaphthalene in the liquid phase, 90 mol% total conversion with the highest part (82.9 wt%) of ethylene and propane in the gas phase after 24 h time-on-stream. This high catalytic performance of the 5 wt%Ni/H-ZSM-5 catalyst can be attributed to the presence of the high mesopore volume, pore diameter, and high mesopore surface area, the existence of the redox active sites, and the presence of strong Lewis acid sites due to synergetic interaction between Ni metal species and zeolite acid support. Based on the product distributions observed, the reaction scheme of the conversion of biomass tar model mixture of naphthalene and 1- methylnaphthalene over studied catalysts was proposed. Our catalytic results obtained over pristine and Ni-modified zeolite catalysts shed light on the potential use of these catalysts in the biomass tar valorization process under atmospheric pressure.
The gas phase selective hydrocracking process of tetralin (biomass tar model chemical compound) into benzene, toluene and xylenes (BTX) was carried out over the H-Beta, H-Mordenite, H-USY, H-Y, and H-ZSM-5 zeolite catalysts in a packed bed reactor under applied atmospheric pressure. To the best of our scientific knowledge, this performed work presents the first systematic investigation, focused on tetralin, cracking to BTX under ambient 1 bar. The highest catalytic activity and carbon deposition resistance were established over the H-ZSM-5 (SiO2/Al2O3 = 30) with the selectivity to the BTX of 52.2 mol. % in intermediates’ liquid phase, 88.7 mol. % of total conversion yield after the 4 h time on stream, 370 °C and gas hourly space velocity (GHSV) =530 h–1, and limited site deactivation. The gas phase was analyzed and ethylene, propane, ethane and methane were identified as main gas products in the product mixture at different reaction conditions. All catalysts were characterized by BET, ICP-AES, XRD, HRSEM, NH3-TPD, and pyridine-DRIFT technique. This high catalytic performance of the H-ZSM-5 catalyst is attributed to the presence the high mesopore volume and mesopore surface area, the mild acidity and the highest Brönsted to Lewis acid sites ratio (BAS/LAS) comparing with other studied zeolite catalysts. Based on the experimental results, the reaction pathway of tetralin transformation into BTX was proposed. Hydrocracking, ring opening, ring contraction, dehydrogenation/hydrogenation, alkylation/dealkylation, isomerization, and overcracking reactions were involved. Results were consistent with the occurrence of the monomolecular reaction mechanism.
The optimal design of a biomass supply chain is a complex problem, which must take into account multiple interrelated factors (i.e the spatial distribution of the network nodes, the efficient planning of logistics activities, etc.). Mixed Integer Linear Programming has proven to be an effective mathematical tool for the optimization of the design and the management strategy of Advanced Biofuel Supply Chains (ABSC). This work presents a MILP formulation of the economical optimization of ABSC design, comprising the definition of the associated weekly management plan. A general modeling approach is proposed with a network structure comprising two intermediate echelons (storage and conversion facilities) and accounts for train and truck freight transport. The model is declined for the case of a multi-feedstock ABSC for green methanol production tested on the Italian case study. Residual biomass feedstocks considered are woodchips from primary forestry residues, grape pomace, and exhausted olive pomace. The calculated cost of methanol is equal to 418.7 €/t with conversion facility cost accounting for 50% of the fuel cost share while transportation and storage costs for around 15%. When considering only woodchips the price of methanol increases to 433.4 €/t outlining the advantages of multi-feedstock approach.
The gasification of biomass is one of the most prominent technologies for the conversion of the raw material feedstock to polymers, useful chemical substances, and energy. The main engineering challenge during the processing of wastes is the presence of tars in gaseous reaction products, which could make this operation methodology unsuccessfully due to the blockage of separating particle filters, fuel line flow, and substantial transfer losses. Catalytic hydrocarbon cracking appears to be a promising developing approach for their optimal removal. However, it is still highly desirable to enhance the catalysts’ activity kinetics, selectivity, stability, resistance to (ir)reversible coke deposition, and regeneration solutions. The purpose of this Review is to provide a comparative systematic evaluation of the various natural, synthetic, and hybrid ways to convert the model molecular compounds into benzene, toluene, xylene, (poly)aromatics, syngas, and others. The recent scientific progress, including calcite, dolomite, lime, magnesite, olivine, char, nonmetallic activated carbons, supported alkali, noble, and transition metals, and (metal-promoted) zeolites, is presented. A special concentrated attention is paid to effectiveness, related to hydrogenation, peculiar pore structure, and formulations’ suitable acidity. The role of catalysis is described, recommendations for prospective catalyzed mechanisms are provided, and future technical feasibility is discussed as well.
The energy world is changing rapidly pushed also by the need for new green energy sources to reduce greenhouse gas emissions. The fast development of renewable energies has created many problems associated with grid management and stability, which could be solved with storage systems. The hydrogen economy could be an answer to the need of storage systems and clean fuel for transportation. The Electrochemical Hydrogen Compressor (EHC) is an electrochemical device, which could find a place in this scenario giving a solution for the hydrogen purification and compression for storage. This work analyzes, through experimental and modeling studies, the performance of the EHC in terms of polarization curve, Hydrogen Recovery Factor (HRF) and outlet hydrogen purity. The influence of many input parameters, such as the total inlet flow rate, the hydrogen inlet concentration, the contaminant in the feed, and the cathode pressure have been investigated. Furthermore, the EHC performance have been modelled in a 1D + 1D model implemented in Matlab® solving the Butler-Volmer system of equations numerically. The experimental campaign has shown that high purities can be obtained for the hydrogen separation from N 2 and CH 4 and purities over 98% feeding He. An increase in the cathode pressure has shown a slight improvement in the obtained purity. A comparison between PSA unit and EHC for a mixture 75% H 2 – 25% CH 4 at different outlet hydrogen pressure and purity was performed to analyze the energy consumption required. Results show PSA unit is convenient at large scale and high H 2 concentration, while for low concentration is extremely energy intense. The EHC proved to be worthwhile at small scale and higher outlet hydrogen pressure.
