For the sustainable utilization of carbon dioxide (CO2), the development of an inexpensive, active, selective and highly stable catalyst is essential to overcome the economic challenges in its reduction to carbon monoxide (CO). Molybdenum and tungsten carbides-based materials are regarded as attractive catalysts for the reverse water gas shift RWGS reaction. This work began with a series of catalytic tests indicating that mixed Mo-W carbides behave essentially like blends of monocarbides Mo2C and WC. To establish a performance baseline, an in-depth evaluation of the two monometallic carbides was conducted enabling a precise assessment of their intrinsic activity and mechanistic behavior under RWGS conditions. The results revealed that Mo2C promoted the formation of both CH4 and CO, while increasing the tungsten content gradually, enhances CO selectivity with decreasing reaction rate. Monometallic tungsten carbide WC achieved complete CO selectivity and maintained it even after 100 h exposure to harsh reaction conditions at 600 & ring;C. In-situ DRIFTS and density functional theory (DFT) calculations revealed that WC can achieve 100 % CO selectivity through two distinct mechanisms on different facets, a concerted redox mechanism on WC (-100), and an associative mechanism on WC (101) facet where further hydrogenation of *CHO intermediate is kinetically unfavorable. Both pathways steer the reaction toward CO production and prevent the formation of undesired side product CH4. This work not only provides valuable insights into the role of metal carbide phases in catalytic performance but also contributes to the fundamental understanding of reaction mechanism.

A series of K/alpha-Fe2O3/gamma-Al2O3 catalysts with high specific surface area (150-300 m2/g) and various levels of alkali promotion (0-11 wt% K) were synthesized using the reverse microemulsion method. The capacity of the catalysts to transform CO2 into light olefins and paraffins via direct hydrogenation at moderate pressures was examined. The effect of potassium loading was investigated in the 300-500 degrees C range at 11 bar, evaluating catalytic performance in terms of CO2 conversion, C2+ selectivity, and space time yield (STY). Reaction tests showed that 7.8 wt% K loading provides the highest CO2 conversion and C2+ selectivity, of 45 % and 46 %, respectively, with a space time yield of 6.5 mmol g- 1 h- 1 at 11 bar and 400 degrees C. The catalyst without alkali promotion provided only 24 % CO2 conversion, 12 % C2 + selectivity, and a space time yield of 0.87 mmol g- 1 h- 1. Under reaction conditions alpha-Fe2O3 was converted to a mixture of Fe3O4 and chi-Fe5C2 nanoparticles that act synergistically to reduce and hydrogenate CO2. Alkali promotion notably enhanced the formation of chi-Fe5C2, leading to higher selectivity to C2 + hydrocarbons.

NiCuCeO 2 nanocatalyst synthesized via ammonia-induced precipitation efficiently reduces CO 2 via methane dry reforming with carbon deposition being strongly affected by the synthesis sequence.

Transition metal carbides (TMCs) have attracted considerable attention because of their high chemical and thermal stability and, in particular, due to their electronic structure that is similar to that of platinum group metals (PGMs). This similarity in the electronic structure, alongside significantly lower cost (compared to PGMs), made TMCs particularly interesting for catalysis applications. Indeed, recent advances in utilizing TMCs have revealed their excellent performance in various catalytic processes. This review explores several essential aspects of customizing TMCs for thermocatalytic reactions. In this context, physical and chemical properties of TMCs are first discussed. It is shown that the unique properties of TMCs are attributed to their charge polarization, structural adjustability, capacity to form alloys, and ability to undergo phase transitions. Next, various synthesis techniques are reviewed, including solid-state and solvothermal methods, as well as microwave- and plasma-assisted techniques. The review then focuses on the utilization of TMCs in thermocatalytic processes, including those used for generation of renewable synthetic fuels and chemicals. Among applications discussed are water gas shift, reforming, CO 2 reduction and hydrogenation, hydrotreating, hydrocracking, and isomerization. For each application, design strategies and the impact of the catalyst composition and morphology on the catalytic performance are discussed. Each section incorporates case studies, including experiments and theoretical investigations that provide additional insights into catalyst design considerations. The review is concluded with a critical discussion of challenges associated with the design, synthesis, and utilization of TMCs and of future research directions. This review offers fundamental insights into tailoring TMCs for applications in thermocatalysis, showing that TMCs are emerging catalytic materials for thermocatalytic processes, such as production of renewables synthetic fuels and chemicals.

Biogas is a product of anaerobic fermentation, which is rich in CO2. The upgrade of biogas to renewable natural gas (RNG) is commercially achieved by separating carbon dioxide (CO2) and impurities to improve its quality. As an alternative, the CO2 contained in biogas can be directly converted into CH4 via the thermocatalytic Sabatier reaction without separation, using H2 generated by water electrolysis (utilizing renewable or surplus, low-carbon-footprint electricity). One of the major elements of this technology is the configuration of the Sabatier reactor. For industrial applications, it is beneficial to eliminate the energy-intensive CO2 separation step, converting biogas to RNG directly. In this study, we report the experimental lab-scale proof of concept of the autothermal Sabatier reactor for direct biogas upgrade. We demonstrate a completely autothermal operation of the air-cooled, stainless steel reactor using a commercial Ni catalyst with a synthetic biogas feed. The effects of feed temperature, space velocity, and reactor cooling were investigated using three prototypes with different sizes and configurations. The maximum CO2 conversion of 91% with 100% selectivity to CH4 generation was achieved in a 10 ''-length reactor, over 100 h of continuous, stable operation, without any external reactor heating or feed preheating.

Thermally coupled catalytic hydrogen combustion-reverse water gas shift reactor for CO2 conversion to synthesis gas was designed and numerically analyzed using a 2D model with a shell-and-tube configuration. A transient, pseudo-homogeneous mathematical model was formulated accounting for axial and radial heat dispersion and using experimentally obtained reaction kinetic parameters. Transient reactor behavior was studied to analyze the dynamic behaviour. Steady-state reactor performance was analyzed in terms of temperature and reactant/product distribution, as well as output parameters of practical importance, namely maximum and outlet reactor temperatures, and outlet conversions. Numerical simulations demonstrate the feasibility of the suggested reactor concept and providing insights into thermal management, including the formation of hot spots, appearance of temperature fronts, and the importance of thermal insulation. The model predicted the possibility of 100 % catalytic H-2 combustion conversion and 80 % CO2 conversion, with the reactor temperature of ca. 900 degrees C.

This study explored bagasse's energy potential grown using treated industrial wastewater through various analyses, experimental, kinetic, thermodynamic, and machine learning boosted regression tree methods. Thermogravimetry was employed to determine thermal degradation characteristics, varying the heating rate from 10 to 30 degrees C/min. The primary pyrolysis products from bagasse are H2, CH4, H2O, CO2, and hydrocarbons. Kinetic parameters were estimated using three model-free methods, yielding activation energies of approximately 245.98 kJ mol- 1, 247.58 kJ mol-1, and 244.69 kJ mol-1. Thermodynamic parameters demonstrated the feasibility and reactivity of pyrolysis with Delta H R:1 240.72 kJ mol-1, Delta G R:1 162.87 kJ mol-1, and Delta S R:1 165.35 J mol-1 K1. The distribution of activation energy was analyzed using the multiple distributed activation energy model. Lastly, boosted regression trees predicted thermal degradation successfully, with an R2 of 0.9943. Therefore, bagasse's potential as an eco-friendly alternative to fossil fuels promotes waste utilization and carbon footprint reduction.

Copper‐doped ceria (CuCeO2) catalysts with 0‐26.5 Cu/(Cu+Ce) at% were synthesized via the reverse microemulsion method. X‐ray diffraction analysis of freshly synthesized and spent (post‐reaction) catalysts showed no separate phase of copper of copper oxide, indicating that Cu was incorporated into the CeO2 lattice, replacing Ce. Temperature programmed desorption experiments showed that the activation energy of CO2 desorption increased for higher Cu loadings, indicating stronger CO2 adsorption. This phenomenon was attributed to enhanced formation of oxygen vacancies due to Cu doping. X‐ray photoelectron spectroscopy further confirmed the enhanced generation of oxygen vacancies due to Cu incorporation. Catalytic performance evaluation with the H2/CO2 feed in the 300‐600 °C range showed that all catalysts were 100% selective to CO generation, with higher Cu loadings resulting in CO2 conversion close to equilibrium values at 500‐600 °C. The activation energy of the reaction, determined through reaction tests, exhibited a linear relationship with the activation energy of CO2 desorption. The relationship between these two energy barriers is explored, providing valuable insights into the mechanism of RWGS activity enhancement.

Efficient CO2 conversion to fuels and chemicals is of paramount importance for mitigating greenhouse gas emissions that accelerate climate change. In CO2 conversion reactions, catalyst nanoparticle growth and sintering under reaction conditions pose significant challenges, limiting the catalytic performance and catalyst stability. In this study, high surface area CeO2/gamma-Al2O3 nano-catalysts were synthesized via the reverse microemulsion method and evaluated for reverse water gas shift. The effect of the active phase dispersion on the CeO2 nano particle growth was investigated via X-ray diffraction and gas adsorption. The 47.9 wt% CeO2/Al2O3 catalyst showed complete selectivity to CO generation, while attaining nearly equilibrium values for CO2 conversion at 600 degrees C and 8000 mL/(g h). As compared to bulk CeO2, nanoparticle growth in the CeO2/Al2O3 catalyst was hindered significantly, resulting in a relatively stable catalytic performance, similar to that of the bulk CeO2. Our findings reveal that the reverse microemulsion synthesized gamma-Al2O3 support significantly decreases CeO2 nano particle growth and agglomeration. This reduction in nanoparticle sintering contributes to the enhanced catalytic performance and stability, facilitating efficient CO2 reduction.

Transition metal-doped ceria (M-CeO2) catalysts (M=Fe, Co, Ni and Cu) with multiple loadings were experimentally investigated for reverse water gas shift (RWGS) reaction. Density functional theory (DFT) calculations were performed to benchmark the properties that impact catalytic activity of CO2 reduction. Temperature-programmed desorption (TPD) was conducted to study the CO2 binding strength on doped CeO2 surfaces; the trend of the energy along increasing metal loading agrees with the DFT calculations. Notably, CO2 dissociative adsorption energy and oxygen vacancy (OV) formation energy are key descriptors obtained from both DFT and experiments, which can be used to evaluate catalytic performance. Results show the effectiveness of transition metal doping in enhancing CO2 adsorption and reducibility of the surfaces, with Fe showing particularly promising results, i. e., CO2 conversion higher than 56 % at 600 °C and 100 % selectivity to CO. Cu exhibits 100 % selectivity to CO but low CO2 conversion, while Co and Ni showed notable ability of methanation, particularly at high loadings. This study finds that an effective CeO2 based RWGS catalyst corresponds to OV sites that have low OV formation energies for surface reduction, and moderate CO2 adsorption energies for strong interaction with the surface to promote C-O bond scission.

Desalination fuel cell (DFC) is an electrochemical cell driven by hydrogen-oxygen redox reactions to simultaneously generate electricity and desalted water. Methanol reforming (MR), although being a relatively well-established method for H-2 generation, produces CO2 and small amounts of CO. While the detrimental effect of CO on proton exchange membrane fuel cells has been extensively studied, the effect of CO on DFC performance has not yet been investigated. In this study, we introduce a novel integrated MR-DFC system and investigate its performance characteristics experimentally. Specifically, we examined the system's response to the presence of CO2 and CO in the MR outlet stream that is directly fed to the DFC inlet. Our findings reveal a decrease in the open-circuit voltage (OCV) and limiting current when utilizing the MR outlet as a feed, although the ohmic region remains intact and the desalination process is not affected significantly. Rotating disk electrode (RDE) tests were conducted to validate the observed reduction in the OCV. A stability test was conducted for 25 h, revealing that feeding the MR outlet to DFC initially provides a similar discharge current to that with pure H-2 feed, followed by certain degradation that was attributed to CO poisoning. Our study provides valuable insights into the performance of the integrated MR-DFC unit, advancing the development of this sustainable water-power system.

High specific surface area K-Fe/gamma-Al2O3 was synthesized via the reverse microemulsion method and tested for direct hydrogenation of CO2 to light hydrocarbons (lower paraffins and olefins). The effect of the synthesis method was investigated by several characterization techniques and via reaction tests, while using wet impregnation-synthesized catalysts as a reference. The reverse microemulsion method resulted in superior catalytic performance, ascribed to the enhanced specific surface area, enhanced active phase-support interaction and reducibility, and facile formation of the active Hagg iron carbide (chi-Fe5C2) phase. The maximum obtained CO2 conversion and selectivity to C2+ hydrocarbons were 56 % and 52 %, respectively, attaining 7.4 mmol g- 1 h- 1 space time yield at 10 bar and 375 degrees C. Characterization results revealed the formation of chi-Fe5C2 and Fe3O4 phases under reaction conditions. Compared to the impregnation method that resulted in the formation of Fe3O4 nanoparticles and Fe/Fe3O4 core-shell nanoparticles, the reverse microemulsion-synthesized catalyst comprised of a mixture of Fe3O4 and chi-Fe5C2 nanoparticles with a relatively uniform particle size distribution. The superior catalytic activity of the reverse microemulsion-synthesized catalyst can be elucidated by the promoted magnetite -* iron carbide transformation that results from the small initial nanoparticle size (below 10 nm).

This study presents the synthesis, characterization, and performance evaluation of copper-doped ceria (Cu/CeO2) 2 ) catalysts with varying Cu/(Cu + Ce) atomic percentages in the context of the reverse water gas shift (RWGS) reaction. Temperature-programmed desorption (TPD) and Density Functional Theory (DFT) calculations revealed that higher Cu loadings promote stronger CO2 2 adsorption due to enhanced formation of OVs through Cu doping. Catalysts exhibited 100 % selectivity toward CO in the 450-600 degrees C range indicating the Cu doped CeO2 2 is a promising candidate for RWGS. Higher Cu loadings were found to enhance CO2 2 conversion, particularly at 600 degrees C. Insights gained from this work revealed that lowering OV formation energy and enhancing CO2 2 activation are key to improving RWGS activity in the presence of doped ceria (Cu/CeO2) 2 ) catalysts.

High surface area cerium oxide was synthesized via the reverse microemulsion method and assessed for CO2 reduction to CO via reverse water gas shift. The resulted ceria nanoparticles (ca. 4 nm) were 100% selective to CO formation, while attaining a nearly equilibrium CO2 conversion at 600 degrees C. As compared to ceria synthesized by wet precipitation, the reverse microemulsion-synthesized ceria exhibited enhanced surface stability and a more stable catalytic performance (declining from 63% to 50% over 100 h on stream). No significant carbon formation was detected and a relatively small decline in conversion was related to the specific surface area reduction induced by the growth of ceria nanoparticles under the reaction conditions.

Reverse microemulsion method was implemented to synthesize a CuO/γ-Al2O3 catalyst (18 wt % Cu) with a specific surface area (SSA) of 328 m2/g (after calcination at 400 °C). Catalytic performance was evaluated in the range of temperatures and space velocities (300-600 °C and 10,000-200,000 mL/(g h)). The catalyst was 100% selective to CO generation while attaining a nearly equilibrium CO2 conversion at 500 °C (ca. 50% at 10,000 mL/(g h) and H2/CO2 = 4). Despite the initial reduction of surface area under the reaction conditions, the reduced Cu/γ-Al2O3 catalyst demonstrated a stable performance for 80 h on stream, attaining a nearly equilibrium CO2 conversion at 600 °C (ca. 60% at 60,000 mL/(g h) and H2/CO2 = 4). The selectivity to CO generation remained complete during the stability test, and no significant carbon deposition was detected.

The present study investigated the thermochemical performance of grape juice processing byproducts, namely grape pomace grits, grape pomace powder, grape seeds, and grape seed powder, using differential thermogravimetric analysis to determine kinetic parameters during thermal decomposition. Pyrolysis experiments were carried out at heating rates of 10, 20, and 30 degrees C to a maximum temperature of 700 degrees C. The mean activation energy for grape pomace powder of 29.96 kJ/mol was the most energy efficient pyrolysis among the four byproduct types. Physicochemical characterization confirmed that these pulp residues can serve as a potential feedstock for fuel and energy production. Grape seeds had a higher lignin content (49 and 52% for seeds and powder) than grape pomace (38 and 45% for grits and powder), making them an appropriate raw material for industrial applications, particularly chemical production. Moreover, their relatively high cellulose and hemicellulose contents indicate a high saccharification potential. The proposed thermal conversion technique could be used downstream from the conventional biodigesters to convert the digestates of juice processing byproducts to biochar and bioenergy. The key findings of this study target growth of sustainable circular economy in the food industry. (C) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.

The presence of emerging contaminants in water and wastewater resources is of ongoing concern for public health and safety. Pharmaceutical compounds are designed to be biologically active and therefore may have effects on nontarget organisms in terrestrial and aquatic environments, even at trace concentrations. The presence of pharmaceutical and personal care products (PPCPs) in wastewater treatment plants is reported in various countries worldwide, mostly in the levels of nanograms to micrograms per litre. The present study investigates the thermal degradation of municipal sewage sludge containing PPCPs at various heating rates. The examined characteristics of the samples include thermal decomposition behavior, volatile release characteristics, and pyrolytic product composition. Thermal characterization of the PPCPs was conducted using differential scanning calorimetry. The gaseous products and typical functional groups of the released volatiles detected by Fourier-transform infrared spectroscopy mainly contained CO2, CO, small-chain hydrocarbons, and oxygen- and nitrogen-containing functional groups together with other species. In addition, the potential of bioenergy production was investigated as a spin-off opportunity during thermal degradation of biosolids. Study results showed that PPCP concentrations can be lowered significantly by thermal treatment of municipal biosolids. Antifungal/antibacterial agents together with opioids, in particular triclosan and tramadol, showed less resistance to thermal degradation while antibiotics could be more recalcitrant to heat treatment. The thermodynamic results provide an important reference for future reactor design and the thermochemical treatment of biosolids as well as their conversion to value-added products.

94% CO 2 conversion and 100% formation selectivity to CH 4 are obtained in a laboratory Sabatier reactor with a packed bed, air-cooled configuration, using a commercial Ni catalyst.

Identifying key catalyst parameters that govern catalytic performance is a main challenge for many reactions. The complex and convoluted behavior of the Mn2O3-Na2WO4/SiO2 catalyst for the oxidative coupling of methane (OCM) makes this task even more challenging. Herein, structure-function correlations are obtained using a simplified methodology that involves cross-referencing statistically estimated reaction kinetic parameters with various experimentally measured catalyst and reaction properties. These correlations and conclusions are shown to be consistent with literature data, which was obtained using advanced in situ techniques. Specifically, these correlations highlight the importance of maintaining highly dispersed Mn2O3 particles in a dispersed Na2WO4 melt, under OCM conditions. The promotion of OCM is associated with the efficient interaction of the two phases in the gel-like formation, which apparently promotes the release of the catalytic active species. However, it is also shown that under reaction conditions the molten state of the Na2WO4 promotes the growth of a separate Mn2O3 phase, which enhances CO2 formation over the OCM by reducing the effective level of interaction between the Mn and the W phases. As a whole, this work not only provides new data but also exemplifies a relatively simple and general tool for identifying catalyst descriptors that govern reaction performance.