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Supercritical water gasification has emerged as a promising technology to sustainably convert waste residues into clean gaseous fuels rich in combustible gases such as hydrogen and methane. The composition and yield of gases from hydrothermal gasification depend on process conditions such as temperature, pressure, reaction time, feedstock concentration, and reactor geometry. However, catalysts also play a vital role in enhancing the gasification reactions and selectively altering the composition of gas products. Catalysts can also enhance hydrothermal reforming and cracking of biomass to achieve desired gas yields at moderate temperatures, thereby reducing the energy input of the hydrothermal gasification process. However, due to the complex hydrodynamics of supercritical water, the literature is limited regarding the synthesis, application, and performance of catalysts used in hydrothermal gasification. Hence, this review provides a detailed discussion of different heterogeneous catalysts (e.g., metal oxides and transition metals), homogeneous catalysts (e.g., hydroxides and carbonates), and novel carbonaceous catalysts deployed in hydrothermal gasification. The article also summarizes the advantages, disadvantages, and performance of these catalysts in accelerating specific reactions during hydrothermal gasification of biomass, such as water–gas shift, methanation, hydrogenation, reforming, hydrolysis, cracking, bond cleavage, and depolymerization. Different reaction mechanisms involving a variety of catalysts during the hydrothermal gasification of biomass are outlined. The article also highlights recent advancements with recommendations for catalytic supercritical water gasification of biomass and its model compounds, and it evaluates process viability and feasibility for commercialization. [ABSTRACT FROM AUTHOR]

Biodiesel production through transesterification results in a large quantity of crude glycerol as a byproduct, the utilization of which is technically and economically challenging. Because of the ability to efficiently process wet feedstocks, supercritical water gasification (SCWG) is utilized in this study to convert crude glycerol into hydrogen-rich syngas. A significant challenge addressed through this study is the decomposition routes of different heterogeneous components of crude glycerol during SCWG. Pure glycerol, methanol and oleic acid were investigated for SCWG as the model compounds of crude glycerol. SCWG of model compounds at temperature, pressure, feedstock concentration and reaction time of 500 °C, 23–25 MPa, 10 wt% and 1 h, respectively, revealed methanol to exhibit the highest H2 yield of 7.7 mmol/g, followed by pure glycerol (4.4 mmol/g) and oleic acid (1.1 mmol/g). The effects of feedstock concentration from 30 wt% to 10 wt% increased H2 yield from all model compounds. Response surface methodology (RSM) was used to develop a response curve to visualize the interactive behavior and develop model equations for the prediction of H2-rich gas yields as a function of the composition of model compounds in the crude glycerol mixture. Predictive models showed a good agreement with experimental results, demonstrating high accuracy and robustness of the model. These findings demonstrated a strong potential of crude glycerol for SCWG to generate H2-rich syngas. [ABSTRACT FROM AUTHOR]

Hydroprocessing of vegetable oil to high‐quality jet fuel range hydrocarbons (HRJ) plays a significant role in the development of completely interchangeable substitute for conventional petroleum‐derived jet fuel and has drawn the attention of aviation experts due to its capacity to mitigate greenhouse gas emissions associated with the aviation industry. The limited performance of 1 wt. % Sn promoted Fe(3)‐Cu(13)/SiO2‐Al2O3 catalyst in our previous study has been attributed to the successive consideration of one variable at a time in its evaluation. Maximization of oleic acid conversion and selectivity of jet fuel range hydrocarbons from hydroprocessing of oleic acid over 1 wt. % Sn promoted Fe(3)‐Cu(13)/SiO2‐Al2O3 catalyst with the best combination of the process parameter involved via multivariate approach, and evaluation of kinetic and thermodynamic activation parameters is the focus of this study. Reduced cubic oleic acid conversion model and reduced quadratic jet fuel range hydrocarbons selectivity model of high significance levels, adequate precision, and high correlation coefficient were developed. Reaction temperature of 339.5°C, 1.6 MPa H2 pressure, 6.2 wt.% catalyst concentration, and 8.0 h reaction time were optimum process parameters that can maximize oleic acid conversion and selectivity of jet fuel range hydrocarbons at 98.2% and 82.2%, respectively. This process was found to be endothermic, irreversible, and nonspontaneous with 45.8 KJ/mol activation enthalpy of reaction, 0.25 KJ/mol entropy of reaction, and the reaction's Gibb's free energy of 198.8 KJ/mol at 340°C. The minimum energy required for the reaction to take place was evaluated as 50.7 KJ/mol. [ABSTRACT FROM AUTHOR]

Canola hull, meal and straw are abundantly available as low-value agricultural residues in Canada. These lignocellulosic feedstocks have the potential for the generation of biofuels as alternatives to fossil fuels. Supercritical water gasification is an emerging hydrothermal process for the conversion of recalcitrant biomasses into value-added hydrogen with the application of water beyond its critical temperature and pressure. This study focuses on the comparative investigation of supercritical water gasification of canola residues for H 2 production through optimization of process temperature (350–500 °C), reaction time (20–80 min) and feedstock concentration (10–25 wt%) at a constant pressure of 23–25 MPa. Supercritical water gasification of canola straw resulted in a high H 2 yield of 7.1 mmol/g to 6.2 mmol/g of H 2 from canola hull and 5.5 mmol/g of H 2 from canola meal at a temperature, reaction time and feedstock concentration of 500 °C, 40 min and 20 wt%, respectively. Furthermore, H 2 yield and total gas yield from canola straw were maximized to 8.1 mmol/g and 29.7 mmol/g at the optimized supercritical water gasification conditions of 500 °C, 60 min and 10 wt%. Hydrochar obtained at high gasification temperatures also revealed aromatic carbon structures and thermal stability due to dehydrogenation, decarboxylation, deamination and aromatization. The overall results demonstrated the potential of supercritical water gasification as an evolving hydrothermal process to convert lignocellulosic biomass into high-value H 2 -rich gas. [Display omitted] • A comparative study of hydrothermal gasification of canola residues was performed. • Temperature, reaction time and feed concentration were optimized for H 2 production. • H 2 yield varied as canola straw (7.1 mmol/g) > hull (6.2 mmol/g) > meal (5.5 mmol/g). • Hydrochar at high temperatures revealed high aromatic carbon and thermal stability. • Water-gas shift, methanation and hydrogeneration affected H 2 , CO, CO 2 and CH 4 yields. [ABSTRACT FROM AUTHOR]

In this study, two catalyst grain sizes (fine powders and pellets) have been investigated to elucidate the effects of both external and internal mass transfer diffusion as well as particle size during the CO hydrogenation reaction to produce higher alcohols. Catalyst grain sizes of 88 and 254 μm were advisedly chosen based on our previous investigations with a similar catalyst matrix for the higher alcohol synthesis (HAS) reaction. The focus in this work was to explore the attractive textural properties of CNH support for CO hydrogenation reaction to produce higher alcohols under specified reaction conditions. Also, to ascertain the possibilities of commercialization of the developed carbon nanohorn (CNH)-supported KCoRhMo catalyst, bentonite clay was added to the pristine support as a binder to enhance its mechanical/crushing strength and kinetic analyses of such catalyst assessed. The influence of bentonite clay was investigated by incorporating 5 wt % of this binder into the formulation of the KCoRhMo/CNH catalyst. For mass transfer considerations, the finely ground KCoRhMo/CNH catalyst powder of 88 μm particle size was used so as to eradicate mass transfer resistance. CO hydrogenation experiments were carried out using a two-phase fixed-bed reactor system to ascertain the intrinsic kinetics of the liquid alcohol products (methanol, ethanol, higher alcohols) as well as the gaseous products generated by the reaction. Syngas of H2/CO ratio of 1.25 was used as feedstock at temperatures, pressures, and gas hourly space velocity ranges of 290-350 °C, 800-1400 psig, and 2.4-4.8 m3 STP/kgcat/h, respectively. The power law model was used to fit experimental data to evaluate kinetic parameters for the HAS reaction on the catalyst surface. Fitting of the experimental data with the developed power law models showed good fits with high R2 values in the range of 0.88-0.96 for the components evaluated. The activation energies computed for ethanol and propanol in the HAS reaction over CNH-supported KCoRhMo catalyst were 54.4 and 92.2 kJ/mol, which are low compared to values obtained by other researchers in similar studies. [ABSTRACT FROM AUTHOR]

The present work investigated the effects of operating conditions (temperature (T), pressure (P), and gas hourly space velocity (GHSV)) on the higher-alcohols synthesis reaction, using a downward-flow fixed-bed reactor. The carbon nanohorn (CNH)-supported KCoRhMo catalysts with compositions of 9% K, 4.5% Co, 1.5% Rh, and 15 wt% Mo were used for this study. The Design Expert software was used to analyze the interaction effects of T (290-370 °C), P (800-1400 psig), and GHSV (2.4-4.8 m³(STP)/kgcat/h) on CO conversion, alcohols, and hydrocarbon product selectivities, as well as their respective yields. The validity of the models was assessed by statistical tests: test of significance and coefficient of determination (R²) values. The recorded R² values suggested that the quadratic models generated could sufficiently depict the experimental data. Increasing temperature and pressure in the ranges of 290-350 °C and 800-1400 psig, respectively, resulted in corresponding increases in CO conversions; however, with increasing GHSV, the CO conversion decreased monotonically. Numerical optimization assessments of the models selected the optimum operating conditions to be 325 °C, 1320 psig, and 2.4 m³(STP)/kgcat/h to give the maximum ethanol and higher alcohols space time yields of 0.126 and 0.177 g/gcat/h, respectively. [ABSTRACT FROM AUTHOR]

Ordered mesoporous carbons (OMC) of desirable textural properties have been synthesized by the novel one-pot soft-templating synthesis approach. Prior to catalyst metals loading, the OMC supports were functionalized using the wet chemical oxidation technique to introduce surface oxygen-containing functional groups for metals anchorage. In this regard, the crucial role functionalizing agents (acidic and basic) on the morphology & structural integrity of the parent OMC support was also investigated. It was observed that the structural integrity of the parent OMC material remained intact as confirmed by the TEM analyses. Moreover, less defective sites were generated as evidenced from the Raman spectroscopic analysis; suggesting that non-acidic oxidative treatment could be a mild way of introducing oxygen functionalities as metal anchoring sites on the surface of pristine OMC support. Based on the defective sites generated on the OMC supports, the severity of chemical oxidative treatment was observed to follow the trend: HNO 3 > NH 4 OH/H 2 O 2 > KOH. The HNO 3 , NH 4 OH/H 2 O 2 and KOH treated-OMC supports were used to prepare a series of KCoRhMoS 2 catalysts with nominal compositions of 9%K, 4.5%Co, 15%Mo, & 1.5 wt.%Rh, respectively. Catalytic performance evaluations of these catalysts for syngas conversion to higher alcohols were also studied at similar reaction conditions: T = 300–340 °C, P = 8.3 MPa, GHSV = 3600 mL (STP)/h.g cat , and H 2 /CO = 1.25. The HNO 3 -treated OMC-supported KCoRhMoS 2 catalyst showed superior total alcohol productivity as compared to its NH 4 OH/H 2 O 2 and KOH counterparts; probably due to the greater number of surface oxygen-containing functional groups, thereby, enhancing its metal-oxygen anchorage properties in the catalyst formulation. All catalysts showed an increase in CO conversion with incremental temperature with a maximum of 40.2% recorded for the KCoRhMo/OMC-HNO 3 catalyst at T = 330 °C as opposed to 26.1 and 19.6% for the catalysts with KOH and NH 4 OH/H 2 O 2 treatment, respectively. [ABSTRACT FROM AUTHOR]

The rising issues of global warming due to the rapid use of fossil fuels are calling for sustainable energies such as dihydrogen, thereafter named 'hydrogen'. The hydrogen demand has quadrupled in the past 45 years from 18 million tons in 1975 to 90 million tons in 2020 with a projected increase to 180 million tons by 2030. Here, we review the conversion of biomass into hydrogen by supercritical water gasification into hydrogen-rich syngas, with focus on thermophysical properties of supercritical water, parameters influencing water gasification and supercritical water gasification of cellulose, hemicellulose, lignin, biomass and model compounds. Parameters influencing water gasification include temperature, pressure, feedstock concentration and reaction time. Processes influencing products distribution comprise hydrolysis, water–gas shift, methanation, hydrogenation and reforming. [ABSTRACT FROM AUTHOR]

Productionof Fischer–Tropsch catalysts is challenging becauseit involves controlling and optimizing multiple parameters in numeroustechnical steps. Here, we present C-supported nanometric Fe and Cocatalysts synthesized by plasma spraying, a method that contractscatalyst production into a single step, in contrast to traditionalmultistep catalyst production by precipitation or impregnation. Thecatalysts were reduced in situand then tested forFischer–Tropsch synthesis in a gas–solid fixed-bed reactorat 230 °C and 30-bar pressure for 24 h. The performance of plasma-synthesizedcatalysts was superior at a gas hourly space velocity of 6,000 mL·gcat–1·h–1, with Fe/C catalysts showing about 30%CO conversion per pass while Co/C catalysts yielded about 20% CO conversion.Identical C-supported Co and Fe catalysts prepared by impregnationor precipitation gave CO conversions of about 7% under similar reactionconditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydroprocessing of oleic acid was done to produce aviation turbine fuel range hydrocarbons. • Sn(1)-Fe(3)-Cu(13)/SiO 2 -Al 2 O 3 was identified as the most promising catalyst. • Catalyst with high oxophilic reduced iron has a positive influence on product selectivity. • Catalyst with high surface area and greater pore volume resulted in high catalyst productivity. • Catalyst with weak metal–support interaction was highly productive for aviation turbine fuel. In this work, the synergistic effects of 1 wt.% Ti, 1 wt.% Zr, and Sn in the range of 0.5−2 wt.% on Fe(3)-Cu(13)/SiO 2 -Al 2 O 3 catalyst were ascertained through extensive characterization and their subsequent evaluation for the production of aviation turbine fuel range hydrocarbons (C 8 -C 16) via hydroprocessing of oleic acid. The largest surface area (571 m2/g) and pore volume (0.65 cm3/g) were obtained from the N 2 physisorption analysis of 1 wt.% Sn-promoted catalyst (E). Cu 2 O and CuO were identified in the X-ray diffractograms (XRD) of all the catalysts except for catalyst E, which revealed only the peaks of Cu 2 O owing to the small particle size of CuO below the threshold of detection of XRD. X-ray photoelectron spectroscopy (XPS) analysis revealed the presence of both oxidized and reduced phases of Cu, Fe, Ti, Zr and Sn in their respective catalysts, with the highest and lowest atomic compositions of reduced Fe and CuO, respectively, detected in catalyst E; corroborating findings from XRD analyses. The relatively homogeneous dispersion of phases present in catalyst E (revealed by its smallest crystallite size of 5.1 nm) was also evidenced by the weakest metal-support interaction from the H 2 -TPR analysis of the same catalyst. Hydroprocessing of oleic acid using catalyst E at 320 °C under H 2 pressure of 2.1 MPa and reaction time of 8 h resulted in the highest aviation turbine fuel range hydrocarbons selectivity of 76.8 % and yield of 71.7 %. This was due to its high metal dispersion, desirable textural properties and high oxophilic reduced iron content. [ABSTRACT FROM AUTHOR]

In this study, alkalinized MWCNT supported MoS catalysts have been doubly-promoted with Co and Rh. Catalysts were prepared by the conventional co-impregnation method and stabilized under argon atmosphere. Characterization of the oxidic samples by BET revealed that the mesoporosity of the pristine MWCNT support was not compromised after loading a combined total of 30 wt% metals (9 wt% K, 4.5 wt% Co, 1.5 wt% Rh, and 15 wt% Mo) on the support; however, a significant decrease in specific surface area was observed. Broad angle XRD analysis confirmed the homogenous dispersion of catalyst metals on the support. Two catalyst grain sizes were first investigated to elucidate the effect of particle size: a finely ground powder (88 μm) and a pelletized form (1,780 μm). Despite the total alcohol yield of 0.261 g/(g h) observed by conducting higher alcohol synthesis reaction at T = 330 °C, P = 8.3 MPa, H/CO = 1.25, and GHSV = 3.6 m/(kg h) for the fine powdered sample, the relatively higher pressure drop could be minimized by using the pelletized form of the catalyst. Finally, a systematic study of variety of selected binders was conducted to gain insight of catalyst's applicability for industrial purposes. Three selected binders namely: bentonite clay, coal tar, and humic acid were thus investigated; taking into consideration significant factors such as melting point and binder requirement per catalyst support. The CO conversions evaluated for the two binder-free catalysts (88 and 1,700 μm) showed that the catalyst with fine particle sizes (88 μm) performed better than that in the pelletized form (binder-free, 1,700 μm); yielding a maximum ethanol selectivity of 38.5 % at steady-state reaction conditions. [ABSTRACT FROM AUTHOR]

In the present work, a series of FeW/SBA-15 catalysts were prepared and screened for their hydrodesulfurization and hydrodenitrogenation activities using bitumen-derived heavy gas oil from Athabasca. A systematic process optimization study has been conducted to investigate the optimum process conditions required to evaluate kinetic parameters for these reactions. Catalyst metal loadings were varied from 0 to 5 and 15 to 45wt.% for Fe and W, respectively; resulting in an optimum catalyst (Cat-5) with metal loadings of 3.0 and 30.0wt.% for Fe and W, respectively. Several techniques were employed to characterize the prepared catalysts and activity results have been correlated with that obtained from characterization. Hydrotreating experiments were performed in a continuous flow micro trickle-bed reactor at the temperatures, pressures, and LHSVs of 633–693°K, 7.6–9.6MPa, and 0.5–2h−1, respectively, with H2 flow rate and catalyst weight maintained constant at 50mL/min and 1.5g, respectively, in all cases. Three kinetic models were applied to fit experimental data obtained from HDS and HDN reaction studies evaluated within temperature range of 633–693°K. The optimum operating conditions for maximum sulfur and nitrogen conversions occurred at temperature, pressure, and LHSV of 673°K, 8.8MPa, and 1h−1, respectively. Experimental data fitted with the Power Law model yielded reaction orders of 2.0 and 1.5 for HDS and HDN reactions, respectively; and activation energies of 129.6kJ/mol and 150.6kJ/mol, respectively. By fitting a modified power law model (Multi-parameter model) to the kinetic data yielded hydrodesulfurization (HDS) and hydrotreating (HDN) reactions orders of 2.2 and 1.8, with respective activation energies of 126.7kJ/mol and 118.8kJ/mol. [ABSTRACT FROM AUTHOR]

Abstract: This work focuses on utilizing mesoporous SBA-15 materials of different pore diameters as potential hydrotreating catalyst supports for heavy gas oil (HGO). Hexane was used as swelling agent for the preparation of variable pore diameter SBA-15 materials. Four kinds of SBA-15 supported FeW catalysts with different pore diameters in the range of 5–20nm were prepared and designated as Cats-A to D. The aqueous co-impregnation technique was employed for preparation of the catalysts. The supports were characterized by several techniques including X-ray powder diffraction (XRD) and N2 adsorption–desorption isotherms. The SBA-15 supported FeW catalysts were characterized by ICP-MS, BET surface area analysis, powder XRD, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and CO chemisorption. Results from XRD profiles, TEM images, and N2 adsorption–desorption isotherms confirmed the presence of highly ordered two-dimensional hexagonal structure with cylindrical arrays of pores. The structural integrity of the samples was preserved even after loading of 2wt.% Fe and 15wt.% W. Hydrotreating experiments were conducted using bitumen derived heavy gas oil under industrial conditions of temperature, pressure, LHSV, and gas to oil ratio of 375–400°C, 8.8MPa, 1h−1, and 600mL/mL, respectively. The SBA-15 supported catalyst with pore diameter of 10nm (Cat-B) was the best among the supports studied for FeW catalysts, probably due to sufficient mass transfer of reactant liquids and gases through the catalyst''s pores while still maintaining a high surface area necessary for metal dispersion. [Copyright &y& Elsevier]

[Display omitted] • Developed bifunctional mesoporous catalysts of Pt/Al-TUD-1 for hydroisomerization. • F-T wax with C 8 -C 44 n-paraffins was hydrorefined into jet fuel with a yield of 63%. • Pt/Al-TUD-1 was tailored with a suitable Brønsted acidity for jet fuel isoparaffins. TUD-1 supported bifunctional platinum catalysts were prepared and characterized for structural and textural properties, acidity, and platinum dispersion. The acidity of TUD-1 was varied by isomorphous substitution of Al and Ti in the framework. The TUD-1 supports possess a three-dimensional amorphous structure as shown by XRD. BET-N 2 adsorption and pyridine FTIR studies revealed that the incorporation of Al in the TUD-1 framework enhances the surface area and generates Brønsted acidity. The catalysts were screened for hydrorefining of Fischer-Tropsch wax with C 8 -C 44 n-paraffins. The catalysts prepared with Si-TUD-1 and Ti-TUD-1 supports were not active for hydrocracking and hydroisomerization due to the absence of Brønsted acid sites, which was verified by pyridine FTIR. Increasing the amount of Al in the framework gradually increased the Brønsted acid sites and thus promoted hydrocracking and hydroisomerization of F-T wax. Pt/Al-TUD-1 catalyst with a Si/Al ratio of 10 produced more jet fuel range hydrocarbons. Hydrorefining of F-T wax was evaluated over an optimal Pt/Al-TUD-1 (Si/Al = 10) catalyst at different pressures and temperatures. Hydroisomerization was favored at low hydrogen pressure. Increasing the temperature shifted the hydrocarbon distribution more towards gasoline due to severe cracking. The temperature of 330 °C and a hydrogen pressure of 5 MPa were found to be optimum to produce jet fuel range hydrocarbons that meet the ASTM specification of cold flow properties. This study proves the feasibility of the production of renewable jet fuel that is directly compatible with fossil-based aviation engines, through hydrorefining of F-T waxes using a mesoporous bifunctional catalyst. [ABSTRACT FROM AUTHOR]

Hydrothermal liquefaction of microalgae under milder reaction conditions was studied for the production and characterization of high quality biocrude oil and hydrochar confirming its feasibility as sustainable biofuel source. The present study investigates the effects of solvents, temperature and time on the yield of biocrude oil. The comparatively higher yield of biocrude oil (47 wt%) obtained in methanol-water mass ratio of 0.75:0.25 also contained higher amount of ester components resulting in higher biocrude oil quality. Methanol-water co-solvent favored higher biocrude oil yield with lower nitrogen and oxygen contents as compared to pure water. Response surface methodology was applied to study the effects of temperature (222–322 °C), and reaction time (10–60min) at constant pressure of 11.5 MPa for methanol-water and biomass-solvent ratios of 0.75:0.25 and 1:5, respectively. The optimum yield of biocrude oil (57.8 wt%) and highest energy recovery (85.3%) was obtained with 75 wt% of methanol in water at 272 °C and reaction time of 35 min. Subcritical condition (temperature of 222 °C, pressure of 11.5 MPa) resulted in the highest hydrochar yield (19.5 wt%). Hydrochars were also characterized by CHNS, BET, FT-IR and TGA techniques to ascertain their prospective elemental composition, textural properties, functional groups as well as thermal stability. • Hydrothermal liquefaction of microalgae in methanol-water system was investigated. • Methanol-water (0.75:0.25 by wt.) system produced optimum bio oil yield of 57.8 wt%. • Addition of methanol in water in HTL lowered oxygen and nitrogen content in bio oil. • Highest hydrochar yield was obtained at 222 °C, 11.5 MPa and reaction time of 10 min. [ABSTRACT FROM AUTHOR]

Mesoporous supports with a π-acceptor were developed for adsorptive desulfurization of petroleum distillates. Pristine mesoporous Al 2 O 3 and Ti-substituted mesoporous Al 2 O 3 were synthesized and used as supports along with commercial γ-Al 2 O 3 for immobilizing ethylenediamine (EDA) linker followed by the π-acceptor, 2, 7-Dinitro-9-fluorenone (DNF). The adsorbents and supports were characterized using BET, FTIR, TGA techniques to ascertain their physicochemical properties. The extent of π-acceptor functionalization on supports was characterized using XRD, TGA and XPS techniques. Adsorbents were examined for the desulfurization of a model oil feed with 500 ppm of sulfur. The commercial γ-Al 2 O 3 -EDA-DNF adsorbent successfully removed 90.4 wt% of sulfur. The substitution of Ti in the framework of mesoporous Al 2 O 3 did not promote its desulfurization efficiency. The higher desulfurization activity of the commercial γ-Al 2 O 3 based adsorbent than that of others is attributed to its textural properties. [ABSTRACT FROM AUTHOR]

In the present study, a series of monometallic Cu/SiO2-Al2O3 catalysts exhibited immense potential in the hydroprocessing of oleic acid to produce jet-fuel range hydrocarbons. The synergistic effect of Fe on the monometallic Cu/SiO2-Al2O3 catalysts of variable Cu loadings (5–15 wt%) was ascertained by varying Fe contents in the range of 1–5 wt% on the optimized 13% Cu/SiO2-Al2O3 catalyst. At 340 °C and 2.07 MPa H2 pressure, the jet-fuel range hydrocarbons yield and selectivities of 51.8% and 53.8%, respectively, were recorded for the Fe(3)-Cu(13)/SiO2-Al2O3 catalyst. To investigate the influence of acidity of support on the cracking of oleic acid, ZSM-5 (Zeolite Socony Mobil–5) and HZSM-5(Protonated Zeolite Socony Mobil–5)-supported 3% Fe-13% Cu were also evaluated at 300–340 °C and 2.07 MPa H2 pressure. Extensive techniques including N2 sorption analysis, pyridine- Fourier Transform Infrared Spectroscopy (Pyridine-FTIR), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), and H2-Temperature Programmed Reduction (H2-TPR) analyses were used to characterize the materials. XPS analysis revealed the existence of Cu1+ phase in the Fe(3)-Cu(13)/SiO2-Al2O3 catalyst, while Cu metal was predominant in both the ZSM-5 and HZSM-5-supported FeCu catalysts. The lowest crystallite size of Fe(3)-Cu(13)/SiO2-Al2O3 was confirmed by XRD, indicating high metal dispersion and corroborated by the weakest metal–support interaction revealed from the TPR profile of this catalyst. CO chemisorption also confirmed high metal dispersion (8.4%) for the Fe(3)-Cu(13)/SiO2-Al2O3 catalyst. The lowest and mildest Brønsted/Lewis acid sites ratio was recorded from the pyridine–FTIR analysis for this catalyst. The highest jet-fuel range hydrocarbons yield of 59.5% and 73.6% selectivity were recorded for the Fe(3)-Cu(13)/SiO2-Al2O3 catalyst evaluated at 300 °C and 2.07 MPa H2 pressure, which can be attributed to its desirable textural properties, high oxophilic iron content, high metal dispersion and mild Brønsted acid sites present in this catalyst. [ABSTRACT FROM AUTHOR]

Cu-ZnO-based catalysts are of importance for CO2 utilization to synthesize methanol. However, the mechanisms of CO2 activation, the split of the C=O double bond, and the formation of C-H and O-H bonds are still debatable. To understand this mechanism and to improve the selectivity of methanol formation, the combination of strong electronic adsorption (SEA) and atomic layer deposition (ALD) was used to form catalysts with Cu nanoparticles surrounded by a non-uniform ZnO layer, uniform atomic layer of ZnO, or multiple layers of ZnO on porous SiO2. N2 adsorption, H2 temperature-programmed reduction (H2-TPR) X-ray diffraction (XRD), transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDX), CO-chemisorption, CO2 temperature-programmed desorption (CO2-TPD), X-ray adsorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) were used to characterize the catalysts. The catalyst activity was correlated to the number of metallic sites. The catalyst of 5 wt% Cu over-coated with a single atomic layer of ZnO exhibited higher methanol selectivity. This catalyst has comparatively more metallic sites (smaller Cu particles with good distribution) and basic site (uniform ZnO layer) formation, and a stronger interaction between them, which provided necessary synergy for the CO2 activation and hydrogenation to form methanol. [ABSTRACT FROM AUTHOR]

[Display omitted] • FTS performance of promoted iron catalysts supported on CNTs were investigated. • Hydrophobicity of catalysts was compared by the water contact angle measurement. • The carburization degree of catalysts was compared by XPS and XAS spectra. • COMSOL Multiphysics was used to simulate the FTS fixed-bed reactor. Light olefins and C 5+ are strategically important products of Fischer-Tropsch synthesis (FTS) over Fe catalysts. In the present work, FTS performance of 0.5K5Mo10Fe/CNTs (DOE 2) and 2 K0.5Mo30Fe/CNTs (DOE 5) catalysts was assessed in terms of CO conversion, C 5+ selectivity, and C 2 -C 4 selectivity under industrially relevant FTS conditions (H 2 /CO = 1.0; GHSV = 2000 h−1; T = 280 ℃; P = 4.13 MPa). The C 2 -C 4 selectivity increased in DOE 2 catalyst to 51.2% with respect to DOE 5 catalyst (2.9%). Meanwhile, the selectivity toward C 5+ hydrocarbons decreased from 93.1% in DOE 5 to 8.3% for DOE 2 catalyst. DOE 5 catalyst was more hydrophobic than DOE 2 as confirmed by the water contact angle measurement, lowering CO 2 selectivity and water gas shift rate. H 2 -TPR and CO 2 -TPD indicated an increase in reducibility and basicity of DOE 5 compared with DOE 2 catalyst, which enhanced iron carbide formation and chain growth probability. The highest amount of metallic Fe in DOE 5 calcined and spent catalysts obtained by XPS and XAS spectra also suggested higher degree of carburization in DOE 5. Additionally, COMSOL Multiphysics software package was employed to provide a 2-dimensional simulation of the FTS fixed-bed reactor. Simulation results were validated using the experimental data for FTS over DOE 2 and DOE 5 catalysts. Effects of temperature on CO conversion as well as distribution of H 2 , CO, and ethylene were discussed. The simulation illustrated the effects of the fixed-bed reactor wall on both velocity and temperature profiles. [ABSTRACT FROM AUTHOR]