CO Hydrogenation Research Articles

Morphology effect of In2O3/Co3O4 on Co–In2O3 interface formation to drive the hydrogenation of CO2 to methanol

In2O3 is loaded onto Co3O4 with diverse morphologies to prepare In2O3/Co3O4 for better understanding of the interaction between metallic Co and In2O3 in CO2 hydrogenation to methanol. After in-depth characterizations, we found that loading In2O3 on platelike Co3O4 (P–Co) can achieve more uniformly dispersed surface hexagonal In2O3 (h-In2O3) and stronger electron transfer between In2O3 and Co3O4 than Co3O4 with other morphologies. Under reaction stabilization, Co3O4 is transformed into metallic Co0, which can promote the reactivity of h-In2O3 to form cubic In2O3 (c-In2O3), accompanied by the formation of Co3InC0.75 carbide. Especially for In2O3/P–Co, stronger interaction between Co0 and c-In2O3 is formed to produce more oxygen vacancies in comparison with other samples owing to the absent of h-In2O3. Furthermore, density functional theory calculation reveals that H2 and CO2 molecules are more easily adsorbed on Co-c-In2O3 interfacial site. As a result, In2O3/P–Co exhibits the best methanol space-time yield of 11.6 mmol · gcat−1 · h−1 and excellent thermal stability for an additional continuous run of 64 h after reaction stabilization.

Functionalization of ionic liquids for heterogeneous catalysis in CO2 conversion: Cycloaddition of epoxides and hydrogenation

The mitigation of environmental impacts caused by greenhouse gas emissions has become increasingly urgent, and the use of CO2 as a primary carbon source is an alternative in chemical transformations, including the synthesis of organic carbonates, formic acid, or methanol. This work aims to synthesize ionic liquids from the imidazolium cation family to be used in the cycloaddition of CO2 with ILs anchored in SiO2-clay heterostructure, MCM-41 and KIT-6 mesoporous materials, as well as the hydrogenation of CO2 with ILs added to ruthenium complexes, i.e., two catalytic systems. The most satisfactory result for CO2 cycloaddition (TON PC = 226) was obtained using the IL (MeO)3Sipmim.Cl anchored in SiO2-clay heterostructure (0.16 mol%) as the catalyst and ZnBr2 (0.04 mol%) as the co-catalyst. The hydrogenation was conducted with the IL (edaO)3Sipmim.Cl and the ruthenium complex Ru-PNN were not successful, but with co-catalyst PEHA, formic acid/formamide was produced (TON Form = 552). The unique catalytic system that showed activity for forming methanol was the commercial Ru-MACHO, Ru-C29H30ClNOP2, (TON MeOH = 3.3). These results highlight the potential of ruthenium-based complexes and supported ionic liquids as active systems in CO2 conversion.

Active Sites for CO2 Hydrogenation to Methanol: Mechanistic Insights and Reaction Control.

Catalytic CO2 conversion to methanol is a promising way to extenuate the adverse effects of CO2 emission, global warming and energy shortage. Understanding the fundamental features of CO2 activation and hydrogenation at the molecular level is essential for carbon utilization and sustainable chemical production in the current climate crisis. This review explores the recent advances in understanding the design of catalysts with desired active sites, including single-atom, dual-atom, interface, defects/vacancies and promoters/dopants. We focused on the design of various catalytic systems to enhance their catalytic performances by stabilizing active metal in a catalyst, identifying the unique structure of active species, and engineering coordination environments of active sites. Mechanistic insights provided by advanced operando and in situ spectroscopies were also discussed. Moreover, the review highlights the key factors affecting active sites and reaction mechanisms, such as local environments, oxidation states, and metal-support interactions. By integrating recent advancements and relating knowledge gaps this review aims to endow an inclusive overview of the field and guide future research toward more efficient and selective catalysts for CO2 hydrogenation to methanol.

A thermodynamic consideration on the synthesis of methane from CO, CO2, and their mixture by hydrogenation

The synthesis of methane from CO and CO2 by hydrogenation is now considered as a promising route in effectively storing hydrogen energy as well as sustainably producing fuels and chemicals, while many reaction details involved in such processes, in particular for the hydrogenation of the CO and CO2 mixture, are not yet adequately understood. As a supplement to our previous works on the hydrogenation of CO and CO2 into alcohols and hydrocarbons, a thermodynamic consideration is made in this work to evaluate the potential and limit for the synthesis of methane from CO, CO2, and their mixture in particular. The results consolidate that in comparison with single CO or CO2, their mixture is probably more credible in practice for the production of methane by hydrogenation, where the overall C-based methane yield can be used as the major index to evaluate the process efficiency. The hydrogenation of CO shows a higher equilibrium yield of methane than the hydrogenation of CO2, while the overall C-based equilibrium yield of methane for the hydrogenation of the CO and CO2 mixture just lies in between and decreases almost lineally with the increase of the CO2/(CO+CO2) molar ratio in the feed, despite the great change in the equilibrium conversions of CO and CO2 with the feed composition. Nevertheless, an adequate overall C-based equilibrium yield of methane (> 85%) can be achieved at a temperature lower than 400 °C and a pressure higher than 0.1 MPa for the stoichiometric hydrogenation of CO, CO2, or their mixture whichever. These results should be beneficial to the design of more efficient catalysts and processes for the hydrogenation of CO/CO2 to methane.

Enhanced CO2 Hydrogenation Performance of CoCrNiFeMn High Entropy Alloys

CO2 hydrogenation is a promising process for removing anthropogenic CO2 emissions and yielding C1 chemicals that can be utilized as fuels and valuable precursors for chemical synthesis. Commercial high-entropy alloys (HEAs) have widespread application in various fields owing to their exceptional thermal stability and tunable microstructure. However, their potential application as catalysts is often limited by the low exposure of active sites. In this study, the commercial CoCrNiFeMn powder was applied for atmospheric pressure CO2 hydrogenation and enhanced its catalytic performance by a combined treatment of ball milling and high-temperature H2 reduction. The high-energy ball milling results in a morphological transition in CoCrNiFeMn HEAs from spherical to irregular. This transformation leads to a significant decrease in particle size and more surface reactive sites. The high-temperature H2 reduction promoted the atomic rearrangement on the CoCrNiFeMn surface, thereby improving its alloy structural homogeneity. These modifications greatly improve the performance of CoCrNiFeMn for CO2 hydrogenation. This work introduces a facile modification approach to facilitate the catalytic efficiency of commercial HEAs in CO2 hydrogenation with high selectivity.

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.

Modulating the electronic interaction of ZnFemCrOx/SAPO-34 to boost CO2 hydrogenation to light olefins

Hydrogenation of CO2 into light olefins presents a promising strategy to realize carbon neutrality. Efficient adsorption and activation of CO2 are critical steps in CO2 hydrogenation into light olefins. Nevertheless, the development of a promotional catalyst that obtains high CO2 conversion and C2=-C4= selectivity is challenging, constrained by the chemical inertness of CO2. In this paper, we have synthesized a highly stable catalyst consisting of ZnFe0.38CrOx oxides and SAPO-34 zeolite, which achieves 11.4 % C2=-C4= yield at CO2 conversion up to 35.4 %. Comprehensive characterization results substantiate the existence of electronic interaction among Fe, Zn, and Cr, which facilitates the adsorption and activation of CO2. More significantly, the CO2 adsorption capacity is linearly related to the degree of electron transfer. In situ DRIFTS results further reveal that electronic interaction promotes the production of carbonate species and subsequent transformation into formate species, contributing to high CO2 conversion. These findings uncover an intrinsic connection between electronic interaction and catalytic activity, offering theoretical guidance for designing bifunctional catalysts.

Optimal design of PdAu/In2O3 catalysts for CO2 hydrogenation

Efficient catalyst design has garnered significant interest in recent decades due to its potential to address both the challenges of the greenhouse effect and energy shortages by facilitating the conversion of CO2 into valuable chemicals through catalytic reactions. To investigate maximizing the synergistic effects of supported PdAu catalysts, we conducted first-principles calculations on the activation and decomposition of CO2 and H2 on the PdAu/In2O3(110) system. The results demonstrate that the incorporation of a secondary metal (Au) into the supported Pd catalyst, in conjunction with precise control over Au concentration, exerts influence on both reactant binding energy and activation. The adsorption and activation of CO2 at the interface sites of Au4/In2O3(110) and PdAu3/In2O3(110) are not observed. The transition state for the dissociation of CO2 into *CO and *O is determined based on adsorbed CO2, providing insights into the properties of activated CO2. The Bronsted–Evans–Polanyi relation, which correlates activation barriers (Ea) with reaction energies (Er), was established for the CO2 dissociation mechanism on PdAu/In2O3(110) catalysts using equation E = 0.4Ea + 0.63. It was carried out to investigate the H2-dissociated adsorption processes and mobility energy on various PdAu/In2O3(110) catalysts. Finally, a highly efficient Pd2Au2/In2O3 catalyst for the hydrogenation of CO2 into methanol has been proposed. This research provides valuable insights into the hydrogenation of CO2 to methanol using bimetal-oxide catalysts and contributes to the optimization of the design of PdAu/In2O3 catalysts for CO2 reactions.

Interface engineering on single-atom Cu-modified BiOBr1−xClx for efficient artificial photosynthesis of methanol

Converting CO2 into value-added fuels was an attractive way to alleviate the energy crisis. Cu-based catalysts were recognized as the most effective candidates for catalyzing CO2 to solar fuels due to their specific electronic structure. However, selective production of desired fuels from photocatalytic CO2 reduction remained a grand challenge. Herein, the interface engineering of single-atom Cu with BiOBr1−xClx nanosheets (Cu-SA/BOBC) was demonstrated to address this challenge. The single-atom Cu in BOBC favored charge transition, carrier separation, and photon utilization, with a superior performance of CO2 photoreduction yielding CH3OH of 8.21 μmol·g−1·h−1, 94.3 % electron-based CH3OH selectivity. Meanwhile, it could lower the CO2 activation energy barrier, and be conducive to strong CO* adsorption and subsequent hydrogenation of CO* to CHO*, which was critical for the high selectivity of CH3OH. This work highlighted a new insight into regulating the photoreduction of CO2 to CH3OH by interfacial interaction.

Mo2Ti2C3TX MXene performance in catalytic CO2 hydrogenation and its promotion with single Pt atoms

Mo2Ti2C3Tx MXene materials, bare or loaded with strongly anchored single Pt atoms, were investigated using various methods, including STEM, XPS, XAS and DFT calculations. Upon Pt impregnation, the delaminated Mo-rich MXene surface undergoes partial oxidation, which is reversed by an H2 thermal treatment at 400 °C. The optimized MXene shows high catalytic activity for CO2 hydrogenation to CO and smaller amounts of methane and methanol. Above the pretreatment temperature of 400 °C, the MXene is gradually defunctionalized from O- and F-containing groups and depleted in carbidic carbon, leading to deactivation. Single Pt atoms are cationic after impregnation, and reduce upon H2 treatment, filling surface Mo vacancies. Pt addition increases the MXene activity, in particular by facilitating H2 dissociation, but has little effect on the single-atom catalyst selectivity and on the rate dependence upon reactant partial pressures. The lowest Pt loading leads to the highest turnover frequency, indicating that the MXene surface sites are key to CO2 activation.

Atomically dispersed Ru on flower-like In2O3 to boost CO2 hydrogenation to methanol

Metal-based catalysts are prevalent in the CO2 hydrogenation to methanol owing to their remarkable catalytic activity. Herein, Ru/In2O3 catalysts with different morphologies obtained by doping Ru into In2O3 with irregular, rod-like, and flower-like morphologies are used for catalytic CO2 hydrogenation to methanol. Results indicate that the flower-like Ru/In2O3 (Ru/In2O3-F) exhibits higher catalytic performance than Ru/In2O3 with other morphologies, achieving a 12.9% CO2 conversion, 74.02% methanol selectivity, and 671.36 mgMeOH·h−1·gcat−1 methanol spatiotemporal yield. Furthermore, Ru/In2O3-F maintains its catalytic stability over 200 h at 5 MPa and 290 °C. The promotional effect mainly stems from the fact that electronic structure of Ru can be effectively adjusted by modulating the morphology of In2O3. The strong interaction between atomically dispersed Ru and In2O3-F enhances the structural stability of Ru, inhibiting the agglomeration of the catalyst during the reaction process. Furthermore, density-functional theory calculations reveal that highly dispersed Ru atoms not only perform efficient and rapid electronic gain and loss processes, facilitating the catalytic activation of H2 into H intermediates. It also enables the generated reactive H to rapidly overflow to the surrounding In sites to participate in CO2 reduction. These findings provide a theoretical basis for the development of high-performance catalysts for CO2 hydrogenation.

Fine-tuning catalytic selectivity by modulating catalyst-environment interactions: CO2 hydrogenation over Pd-based catalysts

Fine-tuning catalytic selectivity by modulating catalyst-environment interactions: CO2 hydrogenation over Pd-based catalysts

Mechanism of methanol synthesis from CO2 hydrogenation over Rh16/In2O3 catalysts: A combined study on density functional theory and microkinetic modeling

In this study, the hydrogenation of carbon dioxide (CO2) to methanol (CH3OH) over Rh16/In2O3 catalyst was studied through Density Functional Theory (DFT) and microdynamics modeling. The spontaneous dissociation mechanisms of H2 and CO2 adsorption at the Rh16/In2O3 interface were investigated. The oxygen vacancies in In2O3 enhanced the adsorption process. Bader charge analysis revealed a marginal positive charge on Rh16, elucidating the critical insights into the electronic characteristics and catalytic activity. The study established the RWGS+CO-Hydro pathway as the predominant mechanism for methanol synthesis, characterized by a sequential transformation of intermediates: CO2*→COOH*→CO*+OH*→HCO*→CH2O*→CH2OH*→CH3OH*. Furthermore, Degree of Reaction Rate Control (DRC) analysis conducted in the range of 373–873 K and 10–2 to 103 bar identified two principal kinetic phenomena: at lower temperature and higher pressure, the conversion of CO* + H* to HCO* significantly impacted the overall reaction rate. Conversely, at higher temperature, the step from CH2O* + H* to CH3O* was dominate.

Metal-organic framework (MOF) integrated Ti3C2 MXene composites for CO2 reduction and hydrogen production applications: a review on recent advances and future perspectives.

Titanium carbide (Ti3C2) MXenes due to their structural and optical characteristics rapidly emerged as the preferred material, particularly in catalysis and energy applications. On the other hand, because of its enormous surface/volume ratio and porosity, Metal-organic Frameworks (MOFs) show promise in several areas, including catalysis, delivery, and storage. The potential to increase the applicability of these magic compounds might be achieved by taking advantage of the inherent flexibility in design and synthesis, and optical characteristics of MXenes. Thus, coupling MOF with Ti3C2 MXenes to construct hybrid composites is considered promising in a variety of applications, including energy conversion and storage. This paper presents a systematic discussion of current developments in Ti3C2 MXenes/MOF composites for photocatalytic reduction of CO2, and production of hydrogen through water splitting. Initially, the overview and characteristics of MXenes and MOFs are independently discussed and then a detailed investigation of efficiency enhancement is examined. Different strategies such as engineering aspects, construction of binary and ternary composites and their efficiency enhancement mechanism are deliberated. Finally, different strategies to explore further in various other applications are suggested. Although Ti3C2 MXenes/MOF composites have not yet been thoroughly investigated, they are potential photocatalysts for the production of solar fuel and ought to be looked into further for a range of applications.

Microwave-powered integrated carbon capture and utilisation (ICCU) for methane production with rapid temperature response from minimal thermal inertia

Integrated CO2 capture and utilisation (ICCU), emerging as an effective approach for achieving global carbon neutrality goals, demonstrates its potential through the transformation of captured CO2 into valuable methane and the concurrent hydrogen storage via methanation reaction. However, traditional ICCU strategies are heavily reliant on conventional thermal conduction heating, and the in-situ methanation process is constrained by reaction thermodynamics, posing significant challenges. In this study, we introduce for the first time a novel microwave-powered system, employing a clean and efficient energy source that offers rapid heating and on-demand operation and acts as an external field enhancement method in the ICCU-methanation procedure. The designed blend of Ni-loaded CaO and carbon nanotubes (CNTs) integrates the functions of CO2 adsorption, hydrogenation catalysis, and microwave absorbing ability. This novel approach achieved a CO2 capture capacity of 3.31 mmol gDFM-1 with CO2 conversion and CH4 selectivity reaching 71.01 % and 98.17 %, respectively, at a nickel loading of 20 wt%. We also propose a possible rate enhancement mechanism for the microwave-powered ICCU-methanation cyclic process compared to conventional methods. The microwave-powered system can substantially enhance overall efficiency by swiftly responding to temperature swings, thus reducing processing time in ICCU-methanation cycles.

Promoting proximity to enhance Fe-Ca interaction for efficient integrated CO2 capture and hydrogenation

Integrated CO2 capture and utilization (ICCU) using “capture-conversion” dual functional materials (DFMs) paves a cost-effective path for restricting CO2 emissions by eliminating the energy-intensive intermediate processes. The interactions between catalysts and absorbents are believed pivotal in ICCU; however, there is a lack of environment-friendly strategy to fabricate the interaction for industrial applications. Here, we propose a solvent-free mechanochemical approach to promote the interaction by improving the proximity between natural calcium and iron sources. The interaction was systemically investigated and confirmed using XRD, XPS, TEM, TPR, etc. As a result, the mechanochemical approach derived DFM achieved 5.5 mmol/g CO2 capacity, 87 % CO2 conversion, and 100 % CO selectivity at 650 °C, significantly outperforming the CaO-alone benchmark (CO2 capacity < 4.5mmol/g, CO2 conversion < 73 %). Further incorporating MgO would alleviate the sintering and promote the CO2 capture stability (< 15 % decrease after 20 cycles) by acting as a thermal-stable barrier. Based on in situ XRD, it is further confirmed that Fe-Ca interaction exhibits a dynamic looping mechanism in ICCU. The techno-economic analysis strongly supports the superiority of ICCU catalyzed by naturally sourced DFMs on eliminating the energy and H2 consumption for CO2 capture and upgradation. As a result, producing CO via ICCU using mechanochemical derived DFMs exhibits 20 % and 10 % cost decrease compared to the conventional CCU and ICCU using CaO alone scenarios, pointing out the potential of ICCU technology in industrial applications.

3D printed steel monoliths for CO2 methanation: A feasibility study

Steel honeycomb monoliths have been manufactured by Fused Deposition Modelling-FDM 3D printing technology using 90 % 17–4 PH steel nanoparticles-loaded polymer filament. Pure steel monoliths were obtained after thermal removal of the polymer and steel sintering. NiO-CeO2 active phase nanoparticles were loaded on powder steel and on the steel monoliths, and the supported catalysts were tested in the hydrogenation of CO2 to CH4, paying special attention to the steel pretreatment before active phase loading. The catalytic experiments confirm that totally functional catalysts have been prepared, showing 100 % selective conversion of CO2 to CH4 above 225 ºC and stability in long-term experiments (18 hours at 325 ºC). The catalytic behaviour is improved by H2O2-pretreatment of the steel honeycomb monoliths before the active phase loading. XPS characterization confirms that the surface of the catalysts is oxidised on the fresh catalysts and gets even more oxidised after the catalytic tests. The H2O2-pretreatment of the steel support partially avoids the additional oxidation under reaction conditions, keeping chromium and cerium cations less oxidised than on the catalyst prepared with untreated steel. In addition, evidence about the electronic interaction between the steel support and the NiO-CeO2 (np) active phase are obtained.

Strong metal-support interaction between Ni and BaCO3 boosts CO2 hydrogenation

Strong metal-support interaction between Ni and BaCO3 boosts CO2 hydrogenation

Insights into the physicochemical property modification on the product distribution of CO2 hydrogenation over heteroatom doped Na-Fe/ZrO2 catalysts

Insights into the physicochemical property modification on the product distribution of CO2 hydrogenation over heteroatom doped Na-Fe/ZrO2 catalysts

Synergistic effect of carbon molecular sieve and alkali metal nitrate on promoting intermediate-temperature adsorption of CO2 over MgAl-layered double hydroxide

The development of intermediate-temperature adsorbents with high CO2 adsorption capacity is crucial for the tandem integration with CO2 hydrogenation catalyst, aimed at enhancing economy viability and minimizing energy consumption in Carbon capture, utilization and storage (CCUS). Although certain porous carbon materials (PCM) have been employed to enhance CO2 adsorption capability of layered double hydroxide (LDH), there remains an urgent necessity to identify more cost-effective and efficient PCM alternatives. Herein, alkali metal nitrates ((Li0.3Na0.18K0.52)NO3, hereafter referred to as LiNaK) modified layered double hydroxide (LDH)/carbon molecular sieve (CMS) composite (LiNaK-LDH/CMS) as promising adsorbents for CO2 capture was reported. The effects of CMS addition and nitrate loading, the calcination and adsorption temperature, as well as the cycling stability were investigated systematically. The results revealed that the CO2 capture capacity of the LiNaK-modified layered double oxide (LDO)/CMS composite (30 mol%LiNaK-LDO/CMS15%)-incorporating with 15 wt% CMS addition and 30 mol% nitrate loading-achieved a remarkable CO2 adsorption capacity of 1.32 mmol/g at 300 °C due to the synergetic interactions between CMS and nitrate; this represents nearly a sevenfold enhancement compared to initial LDO performance. Moreover, the 30 mol%LiNaK-LDO/CMS15% adsorbent also demonstrated commendable cyclic stability after ten adsorption cycles, retaining over 85 % of its initial adsorption capacity. Based on both obtained adsorption performance and characterization data from the adsorbents, a pre-adsorption enhancing CO2 intermediate-temperature adsorption mechanism over LiNaK-LDH/CMS composite through air calcination processes. This study significantly advances LDH-based adsorbent for future research into CO2 intermediate-temperature adsorption.