Reverse Water Gas Shift Research Articles

Gallium-Mediated switching in product selectivity for CO2 hydrogenation over Ni/CeO2 catalysts

Achieving high activity and selectivity for the reverse water–gas shift (RWGS) reaction at low-temperatures continues to pose a significant challenge. Ni-based catalysts have been widely employed in CO2 hydrogenation due to their strong capacity to dissociate H2, but it exhibits low selectivity for CO. Herein, we successfully altered the product selectivity for CO2 hydrogenation via controlling the distribution of Ga species on Ni/CeO2 catalysts. When Ga was combined with Ni to form the spinel of NiGa2O4 (NiGa2O4/CeO2), the main product selectivity was CO. While, the Ga was doped into CeO2 to support Ni (Ni/Ga4-CeO2), the product selectivity was the CH4. The NiGa2O4 spinel supported on CeO2 exhibits excellent performance in the RWGS reaction, with a CO selectivity over 99 %, and a production rate as high as 74.5 mmol/gcat·h at 450 °C and 24000 mL/gcat·h, without any loss of activity after 72 h. The Ni/Ga4-CeO2, containing metallic Ni species and abundant oxygen vacancies, enhances the methanation process, with a CO2 conversion as high as 81.38 %, and a CH4 production rate of 136 mmol/gcat·h. The CO-TPD analysis and density functional theory calculation reveals that the NiGa2O4/CeO2 catalyst exhibits weak adsorption of CO*, which plays a key role in enhancing the selectivity towards CO. Subsequent in-situ DRIFTS analysis further confirms that the differences in CO2 hydrogenation product obtained from NiGa4/CeO2 and Ni/Ga4-CeO2 can be attributed to the formation of different intermediate species over their surface, leading to a change in the selectivity of CO2 hydrogenation products. This study provides an insight to switch the product selectivity for CO2 reduction by controlling the distribution of Ga species.

Sulfate residuals on Ru catalysts switch CO2 reduction from methanation to reverse water-gas shift reaction

Efficient heterogeneous catalyst design primarily focuses on engineering the active sites or supports, often neglecting the impact of trace impurities on catalytic performance. Herein, we demonstrate that even trace amounts of sulfate (SO42−) residuals on Ru/TiO2 can totally change the CO2 reduction from methanation to reverse-water gas shift (RWGS) reaction under atmospheric pressure. We reveal that air annealing causes the trace amount of SO42− to migrate from TiO2 to Ru/TiO2 interface, leading to the significant changes in product selectivity from CH4 to CO. Detailed characterizations and DFT calculations show that the sulfate at Ru/TiO2 interface notably enhances the H transfer from Ru particles to the TiO2 support, weakening the CO intermediate activation on Ru particles and inhibiting the further hydrogenation of CO to CH4. This discovery highlights the vital role of trace impurities in CO2 hydrogenation reaction, and also provides broad implications for the design and development of more efficient and selective heterogeneous catalysts.

Pivotal copper bimetallic oxide in hierarchical Calcium magnesium materials for low-temperature carbon capture and utilization

Carbon removal from anthropogenic greenhouse gas emissions is essential to achieve net-zero emissions and mitigate climate change, and integrated carbon capture and utilisation (ICCU) has been studied for subsequent in-situ chemical production. However, high temperature and CaO sintering remain critical issues, highlighting the need for improved, low-cost CO2 adsorbents that can be regenerated at lower temperatures. Herin, we innovatively introduce the low-temperature ICCU coupled with reverse water gas shift reactions (RWGS) using dual functional materials (DFMs), exemplifying a range of potential transition metals doped over CaO with or without the MgO support. Among all the prepared DFMs, D-Cu showed desirable enhanced catalytic activity at a comparatively low-temperature performance (550°C) and still maintained a stable CO2 capture capacity (7.0mmol g−1) and CO yield (8.0mmol g−1) with an exceptional CO2 conversion (94.4 %) and CO selectivity (97.6 %) after cyclic hydrogenation. The mechanism study revealed that Ca2CuO3 bimetalliccatalyst in the hierarchical porous 2CaO/MgO matrix of D-Cu plays a crucial role in retaining its cyclic stability, surpassing that of noble D-Pt. Given the ICCU-RWGS performance and cyclic stability of cost-effective D-Cu at reduced operating temperatures, the findings would minimise energy and cost consumption.

High pressure microreactor for minute amounts of catalyst on planar supports: A case study of CO2 hydrogenation over Pd0.25Zn0.75Ox nanoclusters

High-pressure studies of well-defined catalysts, deposited on planar supports in ultra-high vacuum using physical methods, may bridge the gap between surface science and applied catalysis approaches in order to develop better catalysts for crucial reactions such as CO2 hydrogenation. However, the chemical reactors necessary for such investigations, typically involving catalyst quantities down to a few hundred nanograms, are lacking.We present the novel design and evaluation of a 50 µL rectangular microchannel reactor capable of testing small quantities of catalyst at pressures up to 40 bar and temperatures up to 240 °C. To evaluate the microreactor performance, Pd0.25Zn0.75Ox nanoclusters soft-landed on SiO2-coated mica sheets using the cluster beam deposition technique, were tested for CO2 hydrogenation via the reverse water–gas shift reaction through a series of kinetic experiments.Experimental results, combined with computational fluid dynamics and mass transport analysis, demonstrate that the proposed microreactor setup allows for testing minute quantities of catalysts with very high sensitivity at industrially relevant temperatures and pressures. Although not restricted to a particular catalyst preparation method, the setup is an excellent platform for conducting catalytic tests on composition-controlled, mass-selected, gas-phase nanoparticles deposited on planar substrates, facilitating the determination of reliable structure–activity relationships and enabling a more rational design of catalysts.

Strong Metal-Support Interaction between Pt and TiO2 over High-temperature CO2 Hydrogenation.

The catalytic activities and stability of oxide-supported metal catalysts are significantly affected by metal-support interactions (MSI) between oxidic supports and supported metals. The surface properties of the support, such as its phase and defects, are crucial in MSI, including both the strong metal-support interaction (SMSI) and electronic metal-support interaction (EMSI). In this study, modulation of SMSI was achieved on rutile-supported Pt nanoparticles (NP) over high-temperature CO2 hydrogenation. The encapsulation of Pt NP surfaces with TiO2-x overlayers is precisely controlled by the defects. It is found that oxygen vacancy defects significantly enhance the catalytic stability of Pt/rutile under high-temperature reverse water-gas shift (RWGS) reaction by inhibiting the occurrence of SMSI. Pt/rutile with oxygen vacancies achieves a 301 molCO×gM-1×h-1 space time yield and considerably catalytic stability (decreased by 8%) at 800 °C over 100 h time-on-stream. Density functional theory (DFT) calculations suggest that the adsorption capacity of Pt NP on the rutile overlayer can be reduced by increasing electron density. Experimental results combined with DFT calculations show that electron transfer from Pt NP to rutile is reduced by the oxygen vacancy defects on Pt/R, preserving the metallic nature of Pt species during CO2 hydrogenation, thereby preventing the formation of SMSI.

Strong Metal‐Support Interaction between Pt and TiO2 over High‐temperature CO2 Hydrogenation

The catalytic activities and stability of oxide‐supported metal catalysts are significantly affected by metal‐support interactions (MSI) between oxidic supports and supported metals. The surface properties of the support, such as its phase and defects, are crucial in MSI, including both the strong metal‐support interaction (SMSI) and electronic metal‐support interaction (EMSI). In this study, modulation of SMSI was achieved on rutile‐supported Pt nanoparticles (NP) over high‐temperature CO2 hydrogenation. The encapsulation of Pt NP surfaces with TiO2−x overlayers is precisely controlled by the defects. It is found that oxygen vacancy defects significantly enhance the catalytic stability of Pt/rutile under high‐temperature reverse water‐gas shift (RWGS) reaction by inhibiting the occurrence of SMSI. Pt/rutile with oxygen vacancies achieves a 301 molCO×gM‐1×h‐1 space time yield and considerably catalytic stability (decreased by 8%) at 800 °C over 100 h time‐on‐stream. Density functional theory (DFT) calculations suggest that the adsorption capacity of Pt NP on the rutile overlayer can be reduced by increasing electron density. Experimental results combined with DFT calculations show that electron transfer from Pt NP to rutile is reduced by the oxygen vacancy defects on Pt/R, preserving the metallic nature of Pt species during CO2 hydrogenation, thereby preventing the formation of SMSI.

Hydrogenation of CO2 to light olefins over Ga2O3-ZIF-8 tandem catalyst

Tandem catalysts composed of metal oxides and zeolites have demonstrated significant potential for the hydrogenation of CO2 to light olefins. However, their development is hindered by the competing reverse water–gas shift reaction and carbon accumulation on the zeolite surface. To address these challenges, we developed a series of innovative tandem catalysts by substituting conventional zeolites with ZIF-8. Our research primarily focused on examining the effects of metal species and content, as well as the particle size of ZIF-8, on catalytic performance. Notably, we achieved a CO2 conversion of 20.2 % and a light olefins selectivity of 73.6 % using a catalyst with 20 % Ga2O3 content and a ZIF-8 particle size of 100 nm at a reaction temperature of 340 °C and pressure of 3.0 MPa. In order to improve the stability of the catalyst, ZIF-8 was modified with La to improve its thermal stability. A CO2 conversion of 23.5 % and a light olefins selectivity of 66.5 % were maintained after 50 h of continuous reaction. While the catalytic activity of La-modified catalysts is slightly lower than that of unmodified ones, their superior stability makes them more suitable for thermal catalytic hydrogenation of CO2. Various characterizations and theoretical calculations revealed that La modification not only enhanced the thermal stability of catalyst but also improved its adsorption and activation capabilities for the reacting gases. Furthermore, the reaction mechanism of CO2 hydrogenation to light olefins was investigated by in-situ diffuse reflectance Fourier transform infrared spectroscopy. This study provides a technical foundation for designing efficient catalysts based on metal–organic frameworks in the field of carbon dioxide thermal catalytic conversion.

Capture and catalytic conversion of CO2 from marine and offshore applications – A review

Abstract This contribution examines recent advances in modeling fluid dynamics and capture/conversion of CO2 from marine and offshore applications in packed-bed columns/trickle-bed reactors subjected to static inclination, externally-induced rolling and heaving motions. Breaking the axial symmetry of the two-phase flow once the packed bed system is tilted results in a significant decrease in process performance, the extent of which is determined by the magnitude of the tilt and the column/reactor diameter. Only the conversion of CO2 from marine engine emissions on-board large cargo ships via catalytic cycloaddition of CO2 to styrene oxide in multiphase large-diameter trickle-bed reactors increases slightly with increasing reactor inclination. Under the externally induced column/reactor oscillations, CO2 capture/conversion performance shifts toward the steady-state solution of the vertical column/reactor as the asymmetry between the two inclined positions decreases. Oscillating (between two inclined symmetrical positions) and heaving packed-bed columns/trickle-bed reactors generate an oscillating performance around the steady-state solution of the vertical static position, which is driven by the amplitude and period of the angular and heaving motions via the continuous evolution of the intensity of the reverse secondary flow and by the magnitude of the reactor/column diameter. The catalytic conversion of CO2 captured from marine emissions via an integrated process coupling reverse water-gas shift reaction and methanol synthesis in a fixed-bed reactors network system shows a remarkable enhancement with the addition of H2O adsorbent to the reaction systems in the sorption-enhanced process periods.

Manufacturing Single‐Atom Alloy Catalysts for Selective CO2 Hydrogenation via Refinement of Isolated‐Alloy‐Islands

AbstractSingle‐atom alloy (SAA) catalysts exhibit huge potential in heterogeneous catalysis. Manufacturing SAAs requires complex and expensive synthesis methods to precisely control the atomic scale dispersion to form diluted alloys with less active sites and easy sintering of host metal, which is still in the early stages of development. Here, we address these limitations with a straightforward strategy from a brand‐new perspective involving the ‘islanding effect’ for manufacturing SAAs without dilution: homogeneous RuNi alloys were continuously refined to highly dispersed alloy‐islands (~1 nm) with completely single‐atom sites where the relative metal loading was as high as 40 %. Characterized by advanced atomic‐resolution techniques, single Ru atoms were bonded with Ni as SAAs with extraordinary long‐term stability and no sintering of the host metal. The SAAs exhibited 100 % CO selectivity, over 55 times reverse water‐gas shift (RWGS) rate than the alloys with Ru cluster sites, and over 3–4 times higher than SAAs by the dilution strategy. This study reports a one‐step manufacturing strategy for SAA's using the wetness impregnation method with durable high atomic efficiency and holds promise for large‐scale industrial applications.

Pt‐Mo₂N Catalyst Formed by Inverse Sintering for the Reverse Water‐Gas Shift Reaction

AbstractThe reverse water‐gas shift (RWGS) reaction is significant for the resource utilization of CO2. However, this reaction requires high temperatures and metal catalysts are prone to agglomeration, leading to loss of activity. In this work, a Pt catalyst supported on Mo₂N formed via phase transition and metal reverse sintering under a high‐temperature NH₃ atmosphere is developed. This catalyst exhibits excellent RWGS activity, achieving a CO production rate of 294.8 mmolgcat−1 h−1 at 623 K, with CO selectivity maintained at 93%. Moreover, under continuous testing conditions for 100 h, the catalyst's activity shows no significant decline. Notably, further investigation reveals that the surface reaction mechanism at 623 K differs from the previously reported associative mechanism, instead following a redox mechanism in the presence of H₂. This research not only provides a deeper theoretical understanding of the mechanism of CO2 hydrogenation but also offers valuable insights for developing novel and efficient metal catalyst regeneration technologies.

Manufacturing Single-Atom Alloy Catalysts for Selective CO2 Hydrogenation via Refinement of Isolated-Alloy-Islands.

Single-atom alloy (SAA) catalysts exhibit huge potential in heterogeneous catalysis. Manufacturing SAAs requires complex and expensive synthesis methods to precisely control the atomic scale dispersion to form diluted alloys with less active sites and easy sintering of host metal, which is still in the early stages of development. Here, we address these limitations with a straightforward strategy from a brand-new perspective involving the 'islanding effect' for manufacturing SAAs without dilution: homogeneous RuNi alloys were continuously refined to highly dispersed alloy-islands (~1 nm) with completely single-atom sites where the relative metal loading was as high as 40 %. Characterized by advanced atomic-resolution techniques, single Ru atoms were bonded with Ni as SAAs with extraordinary long-term stability and no sintering of the host metal. The SAAs exhibited 100 % CO selectivity, over 55 times reverse water-gas shift (RWGS) rate than the alloys with Ru cluster sites, and over 3-4 times higher than SAAs by the dilution strategy. This study reports a one-step manufacturing strategy for SAA's using the wetness impregnation method with durable high atomic efficiency and holds promise for large-scale industrial applications.

A Specific Review of CO2 Catalytic Conversion Reactions Based on the Concept of Catalytic Sites Contiguity

AbstractThermocatalytic conversions of carbon dioxide (CO2) to value‐added products offer promising approaches to achieving net negative emissions. The catalysts for CO2 conversions, particularly for CO2 hydrogenation reactions, usually involve more than one catalytic sites working together. In this review, we first introduce the advanced characterization techniques used to identify the catalytic sites in CO2 hydrogenation catalysts, sites for hydrogen (H2) activation and CO2 adsorption/activation. We then discuss how the dual or multiple‐site configurations influence the catalytic activity and selectivity in reactions such as reverse water‐gas shift (RWGS), CO2 methanation, and CO2 hydrogenation for methanol (MeOH). We finally explain the Catalytic Sites Contiguity (CSC) concept that our research group developed from the work in CO2 reforming of methane and use it to understand the relationship between the spatial arrangement of catalytic sites and the efficiency of reactant activation and conversion in recent publications on MeOH synthesis from CO2 hydrogenation. We hope our insights into the impact of CSC on catalytic performance lead to a potential top‐down design method in optimizing the CO2 hydrogenation catalysts.

Catalytic enhancement of water gas shift reaction with Cu/ZnO/ZSM-5: Overcoming challenges of CO2 and H2 rich feeds

Water gas shift (WGS) reaction commonly converts CO to CO2 using H2O and produces H2 and CO2 in a catalytic fixed bed reactor. This study aims to develop a Cu/ZnO/ZSM-5 catalyst loaded in water gas shift reactor for converting typical synthesis gas produced from dry reforming of methane (DRM) at medium temperature shift (MTS, 200–350 oC) conditions and for preventing reverse reaction due to high feed concentrations of CO2 and H2. The Cu/ZnO/ZSM-5 catalyst was prepared by impregnation method with lower Cu metal loading of 5, 10, and 15 wt%, respectively, compared to commercial catalysts. The synthesized catalyst was characterized using XRF, XRD, SEM, H2-TPR, NH3-TPD, and TGA. The catalyst activity and stability for the WGS reaction were tested in the fixed bed reactor at atmospheric pressure and temperature of 325 °C. The experimental results show that CO conversion increases with increasing Cu loading. The 15 wt% Cu/ZnO/ZSM-5 catalyst showed the best results with a CO conversion of 35% and a yield of H2 of 36% and showed good stability for 32 h. Based on the TGA, the 15 wt% Cu/ZnO/ZSM-5 catalyst forms a 0.04 g carbon/g catalyst, which is much lower when compared to commercial catalyst (0.105 g carbon/g catalyst). The relative activity of the synthesized catalyst indicates 2.4 times better when compared to commercial catalysts. High concentrations of H2 and CO2 in the feed may initiate side reactions, including reverse WGS, methanation, and carbon formation, which will decrease H2 yield.

Preparation of nano Cu-Mo2C interface supported on ordered mesoporous biochar of ultrahigh surface area for reverse water gas shift reaction

High conversion rate and selectivity are challenges for CO2 utilization through catalytic reverse water gas shift (RWGS) reaction. Herein, a novel mesoporous biochar (MB) supported Cu-Mo2C nano-interface was prepared by consecutive physical activation of coconut shells followed by carbothermal hydrogen reduction of bimetal. As compared with traditional carbon materials, this MB exhibited ultra-high specific surface area (2693 m2 g–1) and mesopore volume of mesopore (0.81 cm3 g–1) with a narrow distribution (2–5 nm), responsible for the high dispersion of binary Cu-Mo2C sites, CO2 adsorption and mass transfer in the reaction system. Moderate carbothermal reduction led to the sufficient reduction of Mo ion with carbon matrix of MB and dispersive growth of nano Cu-Mo2C binary sites (~ 6.1 nm) on the surface of MB. Cu+ species were formed from Cu0 via electron transfer and showed high dispersion with simultaneous boosted bimetal loading due to the strong interaction between nano Mo2C and Cu. These were advantageous to the intrinsic activity and stability of the Cu-Mo2C binary sites and their accessibility to the reactant molecules. Under the RWGS reaction conditions of 500 °C, atmospheric pressure, and 300,000 ml/g/h gas hour space velocity, the CO2 conversion rate over Cu-Mo2C/MB reached 27.74 × 10–5 molCO2/gcat/s at very low H2 partial pressure, which was more than twice that over traditional carbon supported Cu-Mo2C catalysts. In addition, this catalyst exhibited 99.08% CO selectivity and high stability for more than 50 h without a decrease in activity and selectivity. This study offers a new development strategy and a promising candidate for industrial RWGS.Graphical

Constructing efficient Pd/Al2O3 catalyst for reverse water-gas shift via alkali-modification

The intrinsic nature of irreducible oxides (e.g. Al2O3) makes it hard to tune the charge state of supported late-transition metals, then difficult to adjust the selectivity of catalysts in CO2 hydrogenation. Herein, we find that modifying the Pd/Al2O3 catalyst with alkali metals (especially potassium) is efficient to boost the CO formation in CO2 hydrogenation. In comparison to Pd/Al2O3, approximately twenty-fold promotion in reverse water–gas shift (RWGS) rate was achieved on K-modified catalysts with proper K/Pd proportions. Combined structural characterizations demonstrate that the enhanced Pd-O interactions through K mediation stabilize the ca. 2 nm sized Pd particles as well as the electron-deficient state of Pd, which are robust enough during long-termed evaluation with undamped performance. In situ spectroscopy unveils a bi-dentate *HCOO associated reaction mechanism taking effect on alkali-modified catalysts, which contributes to ∼ 100 % of CO selectivity and 3318.1 mmol∙gPd-1∙h−1 of CO formation rate at 340°C.

In‐Situ Dynamic Carburization of Mo Oxide with Unprecedented High CO Formation Rate in Reverse Water‐Gas Shift Reaction

AbstractIn situ construction of active structure under reaction conditions is highly desired but still remains challenging in many important catalytic processes. Herein, we observe structural evolution of molybdenum oxide (MoOx) into highly active molybdenum carbide (MoCx) during reverse water‐gas shift (RWGS) reaction. Surface oxygen atoms in various Mo‐based catalysts are removed in H2‐containing atmospheres and then carbon atoms can accumulate on surface to form MoCx phase with the RWGS reaction going on, both of which are enhanced by the presence of intercalated H species or Pt‐dopants in MoOx. The structural evolution from MoOx to MoCx is accompanied by enhanced CO2 conversion, which is positively correlated with the surface C/Mo ratio but negatively with the surface O/Mo ratio. As a result, an unprecedented CO formation rate of 7544.6 mmol ⋅ gcatal−1 ⋅ h−1 at 600 °C has been achieved over in situ carbonized H‐intercalated MoO3 catalyst, which is even higher than those from noble metal catalysts. During 100 h stability test only a minimal deactivation rate of 2.3 % is observed.

In-Situ Dynamic Carburization of Mo Oxide with Unprecedented High CO Formation Rate in Reverse Water-Gas Shift Reaction.

In situ construction of active structure under reaction conditions is highly desired but still remains challenging in many important catalytic processes. Herein, we observe structural evolution of molybdenum oxide (MoOx) into highly active molybdenum carbide (MoCx) during reverse water-gas shift (RWGS) reaction. Surface oxygen atoms in various Mo-based catalysts are removed in H2-containing atmospheres and then carbon atoms can accumulate on surface to form MoCx phase with the RWGS reaction going on, both of which are enhanced by the presence of intercalated H species or Pt-dopants in MoOx. The structural evolution from MoOx to MoCx is accompanied by enhanced CO2 conversion, which is positively correlated with the surface C/Mo ratio but negatively with the surface O/Mo ratio. As a result, an unprecedented CO formation rate of 7544.6 mmol ⋅ gcatal -1 ⋅ h-1 at 600 °C has been achieved over in situ carbonized H-intercalated MoO3 catalyst, which is even higher than those from noble metal catalysts. During 100 h stability test only a minimal deactivation rate of 2.3 % is observed.

Metal oxide (Al, Zr and Ce)-modified Fe-CaO dual functional materials for O2-containing simulate flue gas

In this study, a bifunctional material was synthesis with Fe-CaO doped by Al, Zr and Ce using a one-pot sol–gel method. The doped materials exhibiting a sustainable CO2 capture performance at 650 °C, with initial CO2 absorption capacities of FCZ > FCCe > FCA (16.46, 15.5 and 15.1 mmol/g, respectively). The respective CO yields were 8.71, 7.68 and 6.78 mmol/g. The incorporation of metal oxides into the CaO matrix serves to enhance the structural framework stability, while the strong basic sites can facilitate improved Fe-CaO for CO2 capture and conversion. The doping of Al, Zr and Ce into Fe-CaO enhances the reduction of Fe3+ to Fe0, which is accompanied by the formation of numerous O2− species that are capable of adsorbing CO2. Additionally, Fe3+/Fe3+,2+ serves as the active species in the high-temperature reverse-water–gas-shift (RWGS) reaction. In the presence of O2-containing, the competitive adsorption of CO2 and H2O on the adsorbent surface was observe during CO2 capture. It is noteworthy that the structure of Ca12Al14O33 and CaZrO3 within the CaO matrix acts as a physical barrier and enhances electron interactions, thereby mitigating the influence of O2-containing species on the material performance after 10 cycles during the CO2 capture stage.

Insights into Mechanisms of Reverse Water Gas Shift Activity Enhancement over Reverse Microemulsion‐Synthesized CuCeO2

AbstractCopper‐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 or 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 inverse 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.

Kinetic investigation of dry reforming of methane reaction over Ni–Rh/ZrO2–Al2O3 catalyst using Langmuir-Freundlich isotherm

The study involved conducting kinetic measurements for the dry reforming of methane (DRM) over a Ni–Rh/Al2O3 (85%)-ZrO2(15%) catalyst under a wide range of operating conditions (temperature: 500–900 °C, total flow rate of the inlet feed: 50–100 mL/min). The support material was prepared using the sol-gel method, followed by impregnation of Ni–Rh catalyst on the incipient wetness of the Al2O3–ZrO2 support. The calcined, reduced and spent samples were characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA), inductively coupled plasma atomic emission spectrometer (ICP-AES), N2 adsorption/desorption and CHNS analyzer, and tested for activity, yield and stability in DRM reaction. Furthermore, kinetic behavior of Ni–Rh/Al2O3–ZrO2 catalyst in DRM process was investigated by assuming DRM and reverse water-gas shift (RWGS) reactions take place on two kinds of different active sites. Experimental data were fitted using rate expressions based on the Langmuir-Freundlich (LF) isotherm for DRM and RWGS reactions. The activation energy for the DRM reaction was optimized at 43.62 kJ/mol, falling within the reported literature range of 24.73–108.9 kJ/mol. Statistical indices indicated that the kinetic model accurately predicted CO2 conversion compared to other responses, with an error of 12.054%. The computed and experimental trends for CH4 and CO2 conversions, H2 and Co yield in terms of temperature were similar with each other and the difference between the calculated and experimental trends was lower for conversions compared to yields.