
Romel JiménezUniversity of Concepción · Departamento de Ingeniería Química
Romel Jiménez
PhD
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76
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January 2007 - present
Publications
Publications (76)
Producing biomass‐derived chemicals to substitute their petrochemical counterparts has long been an aspiration of the green chemistry research community. However, synthesizing secondary amines from biomass precursors presents several challenges related to catalyst nature and the mechanistic understanding of reaction systems. Here, we unravel the me...
CO2 hydrogenation to methanol is currently of great importance for energy and environmental objectives. Herein, the effect of ultra-low amounts of Zn on Cu/SiO2 catalysts for CO2 hydrogenation was studied, maintaining the average Cu particle size in the 2–4 nm range to minimize structure sensitivity effects. The addition of Zn amounts as low as Zn/...
Ce promotion increases the rate of methanol formation by two orders of magnitude compared to Cu/TiO2 and
Cu/SiO2 catalysts. The promotion proceeds via the generation of a new active site in which Ce3+ intervenes at the
interface with Cu, without significant influence of the support identity. For higher promoter concentrations (Ce/
(Cu + Ce) greater...
The production of renewable chemicals using lignocellulosic biomass has gained significant attention in green chemistry. Among biomass-derived chemicals, secondary amines have emerged as promising intermediates for synthetic applications. Here, we report a systematic study on the reductive amination of phenolics with cyclohexylamine using Pd/C and...
The mechanistic understanding of the CO2 hydrogenation reaction is essential for the rational design of active and selective catalysts for this process, nevertheless, there are still important controversies related to the structural requirements, the sequence of elementary steps and the reaction intermediate involved in the formation of CH4 and CO(...
Cu-based catalysts promoted with elements such as Zn or Ga are the most studied for CO2 hydrogenation to methanol due to their low cost and high activity. However, the fundamental causes of promotion are still not fully understood. In this work we assessed the effect that these promoters have on the number and intrinsic activity of surface sites us...
The heterogeneously catalyzed reductive amination of phenolics from lignin is considered an attractive sustainable route for the synthesis of primary or high-order aromatic and aliphatic amines. Here, the reductive amination...
Biomass‐based amines have received a lot of attention due to their sustainability and carbon economy. Herein, the roles of the metal sites (Rh⁰ or Pd⁰) and operating conditions on the kinetics and reaction pathways of the heterogeneous catalytic amination of cyclohexanone with aniline have been discussed. Rh/C provides secondary amines with remarka...
The validation of protocols for carrying out the experimental analysis of amination reactions is of paramount importance to enhance the scientific knowledge and reproducibility of results. Accordingly, in the present paper, a protocol has been proposed for the study of the amination of cyclohexanone-to-secondary amines (Diphenylamine and N-Cyclohex...
The liquid phase amination of the cyclohexanone (CyO) with aniline (PhNH2) was studied on a Pd/C catalyst using NaCO2H as a H-donor. Catalytic tests were performed in batch reactors by varying reactant concentrations (0, 0.1, 0.2 and 0.4 mol/L), the temperature (80 to 160 °C) and H2-equivalents availability (0, 2 and 4 H2-equivalents with respect t...
Metal catalysts based on Ni, Co, and Pd supported on SiO2 were evaluated in the catalytic pyrolysis of waste tires using pyrolysis experiments coupled to gas chromatography/mass spectrometry (Py–GC/MS) and thermogravimetric analysis coupled with Fourier Transform Infrared spectrometer (TGA–FTIR) techniques. The effect of temperature and the nature...
Iron-catalyzed tar decomposition is studied by inspecting changes in catalytic activity and its correlation to the metal oxidation numbers. A carbon-aerogel-supported iron (Fe/CAG) catalyst was used herein to decompose toluene (model tar) at between 500 °C and 700 °C. The catalytic decomposition was studied in a conventional reaction system, and th...
The hydrogenation of CO2 to methanol is a viable alternative for mitigating greenhouse gases net emissions as well as a route for hydrogen storage and transportation. In this work, we studied the nature of the active sites generated by the promotion of Pd with Ga and the surface species and their reactivity under reaction conditions. SiO2-supported...
CO hydrogenation reaction was studied at methanation conditions (H2/CO > 3, 250-300ºC) on Co/SiO2 catalysts with different mean Co nanoparticle size (dp = 4 nm, 13 nm y 33 nm). Catalysts were prepared by incipient wetness impregnation; the cobalt loading and reduction conditions were suitably selected in order to produce catalysts with different dp...
The hydrogenation of CO2 to methanol is a viable alternative for reducing greenhouse gases net emissions as well as a route for hydrogen storage and transportation. In this context, the synthesis of active and selective catalysts is a relevant objective. In this work,
we study the promotion of Pd with Ga and Zn in the hydrogenation of CO2 to methan...
The size of copper nanoparticles affects the intrinsic rate of methanol and CO formation in the hydrogenation of CO2 at 230–270 °C and total pressure 8 bar. Cu/SiO2 catalysts with different mean Cu particle sizes were prepared by water-in-oil microemulsions and suitably pretreated to obtain samples with mean particle size between 4 and 36 nm. The i...
The effect of H2O pressure (PH2O) on CH4 formation turnover rate (TOFCH4) was evaluated as a function of Rh cluster size. In-situ DRIFTS and kinetic measurements were used to study the CO hydrogenation at methanation conditions on two Rh/Al2O3 catalysts with different cluster sizes (Rh-1nm and Rh-3nm). It was observed a significant effect of PH2O o...
The present study reports on the technical, economic and environmental analysis of small-scale gasification-ICE systems integrated into sawmills in Chile. Two scenarios were considered, (i) a 100 kWe system for self-consumption in a sawmill and (ii) a 1000 kWe system for using residues from different sawmills. The gasification system was technicall...
La síntesis de metanol a partir de CO2/H2, complementada con la actividad selectiva de diversos catalizadores, es una alternativa viable para reducir las emisiones netas de gases de efecto invernadero. Se conoce que en paralelo a la síntesis de metanol puede ocurrir la reacción indeseada reverse water-gas shift (r-WGS) bajo las condiciones de sínte...
Se estudió la promoción con Ga y Zn de partículas de Pd soportadas en SiO2, en la hidrogenación de CO2 a metanol a 800 kPa y 220-280°C. Se sintetizaron catalizadores mono y bimetálicos (Pd/SiO2, Pd-Ga/SiO2 y Pd-Zn/SiO2) mediante un método de formación de complejos orgánicos superficiales a partir de una impregnación húmeda incipiente, obteniéndose...
Biomass gasification is a promising way to obtain “green energy”, but the gas composition makes it unsuitable for use in traditional technologies (i.e., IC engine). Gas purification over nickel and/or iron catalysts is an attractive alternative. Cellulose-based carbon aerogels (CAGs) have shown suitable physical chemical properties for use as catal...
A comprehensive study of carbon aerogel-supported nickel (Ni/CAG) in the catalytic fast pyrolysis (CFP) of torrefied Eucalyptus globulus was performed in a micropyrolysis unit (Py-GCMS). Effects of pyrolysis temperatures (450–600 °C), catalyst-to-biomass ratio (1:1 < C-to-B < 10:1) and metal cluster sizes (9.6 < Dpi < 21) on upgrading reactions wer...
Tar removal from gasification gases is a determinant step to guarantee the operational feasibility of gasification-to-chemicals/energy systems. This study aimed to develop novel carbon-supported catalysts for the elimination of tarry aromatics (toluene, naphthalene and benzene) from gasification gases. Effects of reaction temperature (700 < T < 900...
Nickel and iron supported on thermostable cellulose-derived carbon aerogels (CAG), were used for the catalytic fast pyrolysis (CFP) of crude and torrefied Eucalyptus globulus. Pyrolysis vapors produced from torrefied biomass under non-catalytic conditions were reduced by 70% in carboxylic acids with respect to vapors originating from crude biomass,...
The effects of using (NH4)2SO4 as a carbonization promoter for producing cellulose-derived carbon aerogels (CAG) was studied. The effects of pretreatment on the textural, morphological, and chemical properties of pristine cellulose nanofibers (CNF) were analyzed through N2 adsorption, scanning electron microscopy (SEM), X-ray diffraction (XRD), ele...
Catalysts of rhodium supported on pure oxides and modified alumina with 50, 75 and 100% of ZrO2 were prepared by the impregnation method, to be tested in the reaction of dry reforming of methane in order to study the effect of the metal-support interaction on the reaction rate. The catalysts were characterized by N2 adsorption isotherms, CO chemiso...
During the last years, the interest for developing carbon-based structures has been renewed. Among several candidates, carbon aerogels (CAGs) have demonstrated potential for several applications such as catalysts support, adsorbents, electrodes and supercapacitors for secondary batteries. This work focuses on the production of carbon structures obt...
Rapidly growing research on biomass reactivity has not benefited enough from the very abundant knowledge acquired on coal-derived materials. Literature comparisons using similar methods are scant and inconclusive. To clarify differences (or similarities) between coal- and biomass-derived chars, we performed a systematic study using three different...
The influence of lanthanum stoichiometry in Ag-doped (La1-xAgxMn0.9Co0.1O3) and A-site deficient (La1-xMn0.9Co0.1O3-δ) perovskites with x equal to 10, 20 and 30 at.% has been investigated in catalysts for soot combustion. The catalysts were prepared by the amorphous citrate method and characterized by XRD, nitrogen adsorption, XPS, O2-TPD and TPR....
The use of wood as feedstock for the production of energy and chemicals is a strategy used by both developing and developed countries because it increases the sustainability of their energy infrastructure. Torrefaction of forest resources for co-firing and densification of biomass energy is among the most prominent alternatives. This study is focus...
Carbon monoxide hydrogenation was studied over a γ-alumina-supported 1 wt.% Rh catalyst by means of kinetic and in situ-Infrared measurements. The study was carried out at 200-300ºC, 0 – 22.5 kPa H2 and 1 – 7.5 kPa CO. The in-situ FTIR scrutiny of catalyst surface shows that adsorbed CO* species and vacancies dominate the Rh surface, while no effec...
Substituted La1-xCexCoO3 perovskite-type oxides (0.0≤x≤0.9), prepared by the self-combustion method, have been investigated as catalysts in soot combustion. The characterization results indicate modification in the specific surface area, crystal structure, oxygen mobility and reducibility of cobaltite upon cerium substitution. Cobaltite structure d...
This work shows that loading Fe into the K/MgO catalyst for soot combustion can reduce K volatilization due to the formation of potassium-iron oxide compounds. K/MgO and K–Fe/MgO catalysts were prepared by the impregnation of potassium and iron precursors on MgO, and their activity for soot combustion was assessed by thermogravimetric analysis. Cat...
gamma-Al2O3 support was modified with zirconia by the grafting method, using zirconium(IV) n-propoxide as precursor. Rh catalysts were prepared by wet impregnation of pure gamma-Al2O3 (Rh/A), Zr modified gamma-Al2O3 (Rh/100Z-A), and pure ZrO2 (Rh/Z) supports. Rh/A presents a good activity in dry reforming of methane and exhibits a high amount of su...
Perovskite-type compounds (La1–xAgx)Mn0.9Co0.1O3 (x = 0.0, 0.1, 0.2, 0.3), prepared by the amorphous citrate method, have been investigated as catalysts for soot combustion. The catalysts were characterized by nitrogen adsorption, XRD, SEM, TPR, O2-TPD, and XPS techniques. The silver addition to the perovskites produces a slight modification of the...
MNbO3 powders (M: Li, Na, K, Rb) are synthesized by a citrate method and calcined at 450, 550, 650, and 750 °C.
The lack of studies in the current literature about the assessment of alkaline niobates as catalysts for soot oxidation has motivated this research. In this study, the synthesis, characterization and assessment of alkaline metal niobates as catalysts for soot combustion are reported. The solids MNbO3 (M = Li, Na, K, Rb) are synthesized by a citrate...
An in-situ sulphated-combustion synthesis is reported to obtain gadolinium [Ce0.9Gd0.1O1.95] and samarium [Ce0.9Sm0.1O1.95] doped ceria electrolytes for solid oxide fuel cells (SOFCs). Nitrate precursors of cerium, gadolinium and samarium reactants were mixed homogenously with a citric acid fuel with an in-situ addition of 10 and 20 mol% ammonium s...
Alumina supported catalytic systems K–Me (Me=Cu, Co and V) for the simultaneous removal of soot and NOx, were prepared by impregnation of a powder particle size alumina, using nitrate solutions of the corresponding metals. Physico-chemical characterization of the prepared catalysts was performed by means of XRD, SEM-EDX, ICP, N2-adsorption and TPR....
Halide imidazolium-based ionic liquids 1-butyl-3-methylimidazolium bromide [bmim][Br] and 1-propylamine-3-methylimidazolium bromide [pamim][Br] were synthesised and tested experimentally as absorbents for biogas upgrading. The former solvent is a conventional off-the-shelf room temperature ionic liquid (RTIL), which is soluble in water and expected...
Catalytic filters for the simultaneous removal of soot and nitrogen oxides were prepared by means of coating cordierite monoliths with alumina-based suspensions containing Cu, Co or V and K as the catalytically active phase. Textural and chemical properties of the coated monoliths were determined by means of N2-physisorption, XRD, SEM-EDX and tempe...
Grafting CeO2 or ZrO2 (monolayer coverages of 25 to 100%) on Rh(1 wt.%)/Al2O3 catalysts resulted in the enhancement of DRM reaction-rate, as compared to Rh over pure supports. This improvement is mainly attributed to better dispersion, and in a lesser degree to H2-spillover, both evidenced in TPR-H2 profiles.
La1−xCaxFeO3 (x=0.1, 0.2, 0.3 and 0.4) perovskites, prepared by the citrate method and characterized by AAS, XRD, TPR-H2 and TPD-O2, were assayed, and its catalytic activity evaluated for soot combustion, using carbon black as a model compound for soot. The catalytic activity was determined by non-isothermal thermogravimetric analysis. A significan...
Reports suggest KNO3 as the active phase for the catalytic combustion of soot, through a redox mechanism with KNO2. Previously, the high activity of KNO3 for coal gasification (mechanism similar to that of soot combustion) was attributed to decomposition into active KxOy (y 3/MgO catalyst showed decomposition into NOx, (to which starting of CB comb...
The thermal degradation of metal complexes formed by chitosan with Cu(II), Ni(II), Co(II), and Hg(II), at different metal concentrations, was studied by thermogravimetric analysis in a nitrogen atmosphere over the temperature range 25–800°C. The results indicate that thermal degradation of chitosan and chitosan-metal ion complexes could be of one o...
Synthesis of nanocrystalline gadolinium doped ceria (Ce0.9Gd0.1O1.95) was attempted by nitrate-fuel combustion technique involving different organic fuels namely urea, citric acid, glycine and poly ethylene glycol. As-combusted ceria precursors were calcined at 700°C for 2h for obtaining fully dense, nanocrystalline ceria powders. Cylindrical ceria...
Beef chops (longissimus dorsi) were pre-treated with 5% carbon monoxide (CO) − 95% N2 for 24 h, vacuum packed in thermo-contractile bags and stored at 0 ± 2°C. Shelf life, as determined by the viable aerobic bacterial load, was 11 weeks. Vacuum-packed chops with heat-contractile film produced a smaller drip loss, had a more intense red colour and h...
The effect of adding alkali metals (Li, Na, K) to a CaO–MgO mixture, on the catalytic combustion of carbon black (CB), a model compound for soot, was studied. Catalysts were prepared by the Sol–Gel method and characterized by surface (BET surface area, XPS, DRIFTS) and bulk (AAS, XRD and TPR) techniques. Samples with a 4:1 catalyst-CB ratio were su...
The effects of modified atmosphere packaging (MAP) containing CO 2 and low CO concentrations (0.1 and 0.4%) on the red color of beef meat and on its shelf life were evaluated. Microbiological, physico-chemical and organoleptic-sensorial characteristics and color of the meat were determined and the results were compared to those of meat packed under...
Resumen Se evaluó el efecto de envasado en atmósfera modificada (MAP) con bajo contenido de CO (0.1% y 0.4%) y presencia de CO 2 sobre el color rojo y la vida útil de carne de vacuno. Se determinaron características microbiológicas, fisicoquímicas, organolépticas-sensoriales y de color del músculo y se compararon los resultados con el MAP de 70%O 2...
A study was made of the catalytic oxidation of a model mixture of effluents from forest biomass combustion equipment, consisting principally of methane (CH 4), naphthalene (C 10 H 8), carbon monoxide (CO) and oxygen-poor air (10% O 2 , balance N 2), in a laboratory reactor, using MeOx/TiO 2 catalysts (Me = Fe, Cu or Mn), prepared using incipient we...
This paper explores the possible effect of the potassium precursor on the activity of K/MgO catalysts for soot combustion and, in particular, which of previously described potassium roles would be more affected. The catalytic activity of the prepared K-catalysts was evaluated through thermogravimetric assays using catalyst-carbon black mixtures. Se...
The catalytic combustion of carbon black (CB), a model compound for soot, was studied in the presence of MgO and of KOH/MgO, the latter prepared by impregnation of MgO with an aqueous solution of KOH. The catalysts were characterized by atomic absorption spectroscopy, thermal programmed desorption, carbothermic reduction, X-ray photoelectron spectr...
MgO, CaO, an equal ratio mixture of the oxides (50-CaO) and a sample with 10% potassium added to the previous mixture, showed increasing activity for the catalytic combustion of carbon black, a model compound for soot. These catalysts were characterized by XPS, BET, DRIFTS and AAS. Activity was measured by TGA and by TPO; CO and CO2 concentration i...
Although coal blends are increasingly utilized at power plants, ash slagging propensity is a non-additive property of the pure coals and hence difficult to predict. Coal ash tendency to slag is related to its bulk chemistry and ash fusion temperatures, and the present study aims to compare the results obtained from thermodynamic simulation with cha...