CO Hydrogenation Activity Research Articles

Effect of Cu incorporation on Fe-based catalysts for selective CO2 hydrogenation to olefins

The process of converting CO2 into sustainable chemical feedstock and fuels through reaction with renewable hydrogen has been regarded as a promising direction in energy research. The enhancement of CO2 hydrogenation efficiency to produce valuable hydrocarbons (specifically olefins) on Fe catalysts through Cu modification has been extensively researched. However, there is ongoing vigorous debate regarding the impact of these modifications on catalytic properties and the underlying mechanism. When compared to unprompted iron-based catalysts for CO2 hydrogenation, the choice of desired products, such as C2-C4 and C5+, is relatively low. So, promoters are frequently employed to customize and enhance product distribution. This study investigates how adding Cu to Fe-based supported catalysts affects their performance in converting CO2 to hydrocarbons, with a specific emphasis on the interaction between Fe and Cu. To achieve this goal, catalysts were created using co-precipitation methods, varying the distribution of Fe and Cu within them. A set of composite catalysts underwent testing in a fixed bed setup using a reactant gas mixture at 350 °C and 30 bar pressure. Analysis techniques such as XRD, SEM, TEM, NH3-TPD, H2-TPR, and N2 adsorption-desorption isotherms revealed the presence of iron-copper interaction within the composite catalysts. This interaction between the two components synergistically enhances the catalytic activity in CO2 hydrogenation.

CoCe composite catalyst for CO2 hydrogenation: Effect of pore structure

In order to realize the dual carbon goals of “carbon peaking” and “carbon neutrality”, the design and development CO2 hydrogenation catalyst with high performances is of great significance. In this study, the CoCe composite catalysts were prepared by different methods and used to CO2 catalytic hydrogenation. The physicochemical properties of the prepared catalysts were characterized by XRD, BET, TEM/HRTEM, and H2-TPD. The characterization results indicated that the studied CoCe composite catalytsts with different pore structure can be prepared by different preparation methods. The suitable preparation method can promote Co species to be dissolved into the CeO2 lattice to form Ce-O-Co solid solution, which can promote the corresponding Co species to be reduced by H2 to form active Co0 species. The large specific surface area and developed ordered mesoporous structure of the CoCe-HT catalyst precursor, which was prepared by hard-template method, are conducive to the formation of active Co0 species and activation of H2 to produce reactive H species. The CO2 hydrogenation activity of the studied CoCe composite catalysts follows the following order: CoCe-HT > CoCe-CP > CoCe-CA > CoCe-HY. The CoCe-HT catalyst showed high CO2 hydrogenation conversion of 53.9 % and good using stability at 360 °C for 600 min. However, the CoCe-CA prepared by complex method has a poor use stability.

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.

CO2 hydrogenation to methanol over Cu-CeO2-ZrO2 catalysts: The significant effect of metal-support interaction

CO2 hydrogenation to methanol is an important pathway to achieving carbon neutrality, with metal-support interaction (MSI) being crucial in the design and optimization of catalysts for this process. In this study, Cu-CeO2-ZrO2 catalysts (CuCe + Zr, CuZr + Ce, CeZr + Cu, and CuCeZr) with different interactions between metal Cu and supports were successfully prepared. We mainly address the problem that how the MSI affects the catalytic performance. The CuCeZr prepared by one step solid-phase method shows the optimal catalytic activity and stability for CO2 hydrogenation, even better than the benchmark commercial Cu-ZnO-Al2O3 catalyst for syngas to methanol. Based on the investigation of the structure-performance relationship of catalysts, we propose that the excellent catalytic activity of CuCeZr is mainly determined by its largest surface area of metallic Cu (SCu) and the most amount of Cu species at Cu-support interface, both resulting from the strongest MSI between metallic Cu and CeO2-ZrO2 support. Furthermore, in situ DRIFTS showed that the strong SMI in CuCeZr promotes the formation of formate and its rapid transfer to methoxy, thereby efficiently producing methanol. This work reveals the intrinsic active sites of Cu-CeO2-ZrO2 catalysts from a MSI perspective, providing useful insights for researchers to design highly efficient Cu-based catalysts.

Preparation of Sustainable Ni/SiO2 Catalysts from Rice Husk by Different Methods for CO2 Methanation.

Silicon dioxide (SiO2) from rice husk can be extracted and be used as support for Ni-based catalysts. The impregnation method (IM) is usually used for preparing Ni/SiO2 catalysts, but its catalytic activity in CO2 hydrogenation to CH4 remains unsatisfactory. In this work, we explored alternative preparation methods, using ammonia evaporation method (AEM) and hydrothermal method (HM) to prepare the catalysts. The results showed that the catalysts prepared by AEM and HM were significantly superior to that prepared by IM. Notably, the catalyst synthesized by AEM from sustainable silica exhibited the best performance, achieving 81.69% CO2 conversion and over 99% methane selectivity at low reaction temperature of 300 °C. The characterization techniques indicate that the Ni/SiO2-AEM catalyst can form nickel phyllosilicate with lamellar structure, leading to better Ni dispersion and higher specific surface area. Furthermore, the results of in-situ DRIFTS have revealed the potential catalytic mechanism over Ni/SiO2 catalysts, indicating that it involves pathways with both the CO* and HCOO* as the key intermediates.

Modulation of Selectivity and Activity of Ni/TiO2 Catalysts by Metal Dispersion in Photothermal CO2 Hydrogenation

Ni/TiO2 catalysts are efficient and cost‐effective for photothermal CO2 hydrogenation. However, the achieved CO/CH4 ratio strongly depends on the specific characteristics of these catalysts. To further ascertain the role of metal dispersion and photoactivation on selectivity, in this work we investigate the impact of Ni loading over high surface area anatase on the photothermal performance. Catalysts with 3 and 10 wt. % of Ni prepared by incipient wetness impregnation show initial good dispersion of the metal, although after activation in H2 metallic Ni nanoparticles are observed for 10%Ni/TiO2. This last catalyst demonstrates superior CO2 hydrogenation activity at high temperature, but below 200 ºC it is overpassed by the catalyst with 3 wt % Ni/TiO2. The selectivity varies remarkably with Ni loadings. Thus, at 350 °C about 93 % of methane is obtained over 10 wt.% Ni/TiO2, while 3%Ni/TiO2 yields about 97 % of CO. Low‐intensity UV irradiation enhances performance, particularly at temperatures below 200 ºC, where an increment in the production of methane of up to 75 % is observed for 3 wt.% Ni/TiO2 at 200 ºC. These results highlight the influence of metal dispersion, along with irradiation on modulating the selectivity of the photothermal CO2 hydrogenation

Tuning the CO2 hydrogenation activity and selectivity of TiO2 nanorods supported Rh catalyst via secondary‐metals addition

AbstractSecondary‐metals promotion is key to tune the CO2 hydrogenation performance of Rh‐based catalyst. We describe the addition of Cu or Co in TiO2 nanorods supported Rh catalyst (viz., RhMx/TiO2), showing significant impact on the CO2 hydrogenation activity and productivity. Cu addition can promote the partial hydrogenation to alcohols (methanol and ethanol), whereas Co led to the deep hydrogenation to alkanes (CH4, C2H6). Comparative time‐resolved in situ DRIFTS studies with H2/D2 isotopic exchange further reveal that both surface adsorbed CO* and formates could be the key reaction intermediates during the CO2 hydrogenation over RhMx/TiO2 (especially the RhCu2.5/TiO2), in which the interaction strength of CO* regulated by secondary‐metals addition was key to tune the reaction pathways and productivity. The findings suggested that rational design of active metal sites, for example the synergy between Rh and secondary‐metals, is highly needed to promote the CO insertion and CC coupling to produce ethanol.

Tailoring metal-support interactions via spatial confinement of Ni/CeO2 interfaces on h-BN for efficient CO2 methanation

Modulating metal-support interactions is critical for improving catalytic activity and product selectivity for CO2 hydrogenation. Such modulation can be achieved by modifying the metal nanoparticles as well as the supports. Here, we prepared a novel catalyst, in which Ni nanoparticles were dispersed on CeO2 and hexagonal boron nitride (h-BN) hybrid supports. The introduction of h-BN to Ni/CeO2-BN effectively improves the dispersion of Ni nanoparticles. More importantly, the abundant Ni-CeO2 interfacial sites with enriched oxygen vacancies are formed over h-BN edge sites. The dispersed Ni species are anchored on CeO2 via a unique interfacial structure, with electron-rich Ni (Niδ−) species. At the interfacial sites on Ni/CeO2-BN, the synergy between oxygen vacancies and Niδ−, which enhances CO2 activation and H2 dissociation, respectively, renders superior catalytic performance for CO2 methanation. In situ DRIFTS suggests formate as key rate-limiting intermediates on Ni-CeO2 sites, while the formation of B-H bonds further promotes hydrogen activation and subsequently the catalytic performance. The modulation of metal-support interactions by spatial confinement effect by BN offers a new paradigm for designing metal/oxide catalysts for chemical transformations that requires bifunctionality as CO2 hydrogenation.

Using phosphonic acid monolayers to control CO2 adsorption and hydrogenation onPt/Al2O3

Phosphonic acid (PA) self‐assembled monolayers (SAMs) were deposited onto Pt/Al2O3 catalysts to enable control over CO2 adsorption and CO2 hydrogenation activity. Significant differences in catalytic activity toward CO2 hydrogenation (reverse water‐gas shift, RWGS) were observed after coating Al2O3 with PAs, suggesting that the reaction was mediated by CO2adsorption on the support. Amine‐functionalized PAs were found to outperform their alkyl counterparts in terms of activity, however there was little effect of amine location in the SAM (i.e., spacing between the amine functional group and phosphonate attachment group). One amine‐PA and one alkyl‐PA, aminopropyl phosphonic acid (C3NH2PA) and methyl phosphonic acid (C1PA), respectively, were investigated in more detail. The C3NH2PA‐modified catalyst was found to bind CO2 as a combination of carbamate and bicarbonate. Additionally, at 30 °C, both PAs were found to reduce CO2 adsorption uptake by approximately 50% compared to unmodified 5%Pt/Al2O3. CO2 adsorption enthalpy was measured for the catalysts and found to be strongly correlated with hydrogenation activity, with the trend in binding enthalpy and CO2 hydrogen rate trending as uncoated > C3NH2PA > C1PA. PA SAMs were found to have weaker effects on CO binding and CO selectivity, consistent with selective modification of the Al2O3support by the PAs.

Recent Developments on CO2 Hydrogenation Performance over Structured Zeolites: A Review on Properties, Synthesis, and Characterization

This review focuses on an extensive synopsis of the recent improvements in CO2 hydrogenation over structured zeolites, including their properties, synthesis methods, and characterization. Key features such as bimodal mesoporous structures, surface oxygen vacancies, and the Si/Al ratio are explored for their roles in enhancing catalytic activity. Additionally, the impact of porosity, thermal stability, and structural integrity on the performance of zeolites, as well as their interactions with electrical and plasma environments, are discussed in detail. The synthesis of structured zeolites is analyzed by comparing the advantages and limitations of bottom-up methods, including hard templating, soft templating, and non-templating approaches, to top-down methods, such as dealumination, desilication, and recrystallization. The review addresses the challenges associated with these synthesis techniques, such as pore-induced diffusion limitations, morphological constraints, and maintaining crystal integrity, highlighting the need for innovative solutions and optimization strategies. Advanced characterization techniques are emphasized as essential for understanding the catalytic mechanisms and dynamic behaviors of zeolites, thereby facilitating further research into their efficient and effective use. The study concludes by underscoring the importance of continued research to refine synthesis and characterization methods, which is crucial for optimizing catalytic activity in CO2 hydrogenation. This effort is important for achieving selective catalysis and is paramount to the global initiative to reduce carbon emissions and address climate change.

Tuning Catalytic Activity of CO2 Hydrogenation to C1 Product via Metal Support Interaction Over Metal/Metal Oxide Supported Catalysts.

The metal supported catalysts are emerging catalysts that are receiving a lot of attention in CO2 hydrogenation to C1 products. Numerous experiments have demonstrated that the support (usually an oxide) is crucial for the catalytic performance. The support metal oxides are used to aid in the homogeneous dispersion of metal particles, prevent agglomeration, and control morphology owing to the metal support interaction (MSI). MSI can efficiently optimize the structural and electronic properties of catalysts and tune the conversion of key reaction intermediates involved in CO2 hydrogenation, thereby enhancing the catalytic performance. There is an increasing attention is being paid to the promotion effects in the catalytic CO2 hydrogenation process. However, a systematically understanding about the effects of MSI on CO2 hydrogenation to C1 products catalytic performance has not been fully studied yet due to the diversities in catalysts and reaction conditions. Hence, the characteristics and modes of MSI in CO2 hydrogenation to C1 products are elaborated in detail in our work.

Enhanced conversion of CO2 into C2H4 on single atom Cu-anchored graphitic carbon nitride: Synergistic diatomic active sites interaction

Single atom metal–nitrogen–carbon materials have emerged as remarkably potent catalysts, demonstrating unprecedented potential for the photo-driven reduction of CO2. Herein, a unique Cu@g-C3N5 catalyst obtained by cooperation of single atom Cu and nitrogen-rich g-C3N5 is proposed. The particular CuN diatomic active sites (DAS) in Cu@g-C3N5 contribute to the formation of highly stable CuOCN adsorption, a key configuration for CO2 activation and CC coupling. The synergistic diatomic active sites interaction is found responsible for the efficient photoreduction of CO2 to C2H4 which has been demonstrated in our Gibbs free energy calculation and COHP analysis. The CO2 activation mechanism was studied, the charge density difference and DOS analysis show that the low oxidation state Cu atom significantly affects the electronic structure of g-C3N5 and then enhance the catalytic activity of CO2 hydrogenation.

Reactivity Switch of Platinum with Gallium: From Reverse Water Gas Shift to Methanol Synthesis.

The development of efficient catalysts for the hydrogenation of CO2 to methanol using "green" H2 is foreseen to be a key step to close the carbon cycle. In this study, we show that small and narrowly distributed alloyed PtGa nanoparticles supported on silica, prepared via a surface organometallic chemistry (SOMC) approach, display notable activity for the hydrogenation of CO2 to methanol, reaching a 7.2 molCH3OH h-1 molPt-1 methanol formation rate with a 54% intrinsic CH3OH selectivity. This reactivity sharply contrasts with what is expected for Pt, which favors the reverse water gas shift reaction, albeit with poor activity (2.6 molCO2 h-1 molPt-1). In situ XAS studies indicate that ca. 50% of Ga is reduced to Ga0 yielding alloyed PtGa nanoparticles, while the remaining 50% persist as isolated GaIII sites. The PtGa catalyst slightly dealloys under CO2 hydrogenation conditions and displays redox dynamics with PtGa-GaOx interfaces responsible for promoting both the CO2 hydrogenation activity and methanol selectivity. Further tailoring the catalyst interface by using a carbon support in place of silica enables to improve the methanol formation rate by a factor of ∼5.

Effects of ZrO2 crystalline phase on oxygen vacancy of GaZr oxides and their properties for CO2 hydrogenation to light olefins

A bifunctional catalyst, comprising GaZr oxide and SAPO-34 zeolite, manifests enhanced catalytic activity in CO2 hydrogenation to light olefins; nonetheless, the comprehensive analysis of the pivotal role played by the underlying structure of ZrO2 in Ga-Zr oxide has not been investigated. Herein, different crystalline structures of ZrO2 were prepared by the co-precipitation method and adopted as a support to deposit Ga to obtain ZrO2 with different ratios of monoclinic ZrO2 (m-ZrO2) to tetragonal ZrO2 (t-ZrO2) in GaZr oxides for CO2 hydrogenation to light olefins. Various characterizations demonstrated that the interface between Ga and the mixed phase of (m-t) ZrO2 produces more oxygen vacancies which favors the adsorption and activation of CO2, and the larger specific surface area and stronger H2 adsorption and dissociation capacity promote CO2 conversion. Interestingly, the GaZr oxide with high m-ZrO2 content exhibits superior catalytic activity than the GaZr oxide with high content of t-ZrO2. The highest light olefins yield (9.0%) and selectivity (77.9%) (CO free) with 27.9% CO2 conversion was achieved. In-situ DRIFT spectra further elaborated that the GaZr oxides with different ZrO2 crystalline phases follow the same reaction pathway to hydrogenate CO2 first to HCOO* and then to CH3O* on GaZr oxide surface. While compared with sole ZrO2, the introduction of Ga significantly promotes the hydrogenation of HCOO* to CH3O*, acting as a crucial reaction intermediate that subsequently diffuses into SAPO-34 pores to enhance the desired light olefins selectivity.

Reduced Siderite Ore Combined with Magnesium Oxide as Support Material for Ni-Based Catalysts; An Experimental Study on CO2 Methanation

Ni-based catalysts play a fundamental role in catalytic CO2 methanation. In this study, the possibility of using siderite ore as a catalyst or catalytic support material for nickel-based catalysts was investigated, aiming at the exploitation of an abundant natural resource. The catalytic performance of Ni-based catalysts with reduced siderite ore as a support was evaluated and compared to MgO as a support material. MgO is known as an effective support material, as it provides access to bifunctional catalysts because of its basicity and high CO2 adsorption capacity. It was shown that undoped and Ni-doped reduced siderite ore have comparable catalytic activity for CO2 hydrogenation (20−23%) at 648 K, but show limited selectivity toward methane (<20% for sideritereduced and 60.2% for Ni/sideritereduced). When MgO was added to the support material (Ni/sideritereduced/MgO), both the CO2 conversion and the selectivity toward methane increased significantly. CO2 conversions were close to the thermodynamic equilibrium, and methane selectivities of ≥99% were achieved.

Performance of Cu-Mn-Zn/ZrO2 catalysts for methanol synthesis from CO2 hydrogenation: The effect of Zn content

A series of Cu-Mn-Zn/ZrO2 catalysts with different Zn contents were prepared by sol-gel method and characterized by XRD, BET, TPR, N2O-adsorption, XPS, TPD and in-situ DRIFTS. It was found that by increasing a certain amount of Zn, the catalytic activity for CO2 hydrogenation increased. Among all samples, Cu3MnZn0.5Zr0.5 (CMZZ-0.5) possessed the best CO2 conversion (6.5%) and methanol selectivity (73.7%) at 250 °C and 5 MPa. Characterization results showed that Zn entered the Cu1.5Mn1.5O4 spinel structure, forming ZnOx and thus more surface OH groups. This increased the content of Cu0 and Cuα, which improved the activation of H2 and CO2. The pathway of CO2 to methanol was also clarified through in-situ DRIFTS.

CO2 hydrogenation to synthetic natural gas with light hydrocarbons on Mn-promoted mesoporous Co3O4-Al2O3 metal oxides

Direct CO2 conversion into synthetic natural gas (SNG, CH4) with simultaneous small production of light paraffinic C2-C4 hydrocarbons to enhance a heating value of SNG was investigated with ordered mesoporous CoMnAl mixed metal oxides (denoted as m-CoMnAl). CO2 hydrogenation activity to form hydrocarbons with small CO byproduct formed by a reverse water gas shift reaction (RWGS) was strongly affected by the MnO2 promoter content in the ordered Co3O4-Al2O3 mesoporous structures. The m-CoMnAl structures with proper amount of Mn promoter were found to be effective to enhance CO2 conversion to methane with small amount of light hydrocarbons formation, which were mainly attributed to the presence of abundant oxygen vacant sites with a stable preservation of the partially oxidized cobalt nanoparticles in the ordered mesoporous Co3O4-Al2O3 structures even under a reductive hydrogenation condition. Selective methanation of CO2 was found to be more favorable on the highly reduced metallic cobalt nanoparticles formed with smaller amount of Mn promoter (m-CoMnAl(0.05)), however, excessive Mn content such as Mn/Co ratio > 1 (m-CoMnAl(1.0)) revealed less structural stability of ordered mesoporous structures with lower CO2 conversion with relatively higher CO selectivity of 1.4 % with lower olefin selectivity through severe phase segregations of the Co-Mn-Al mixed metal oxides with selective formations of MnCO3 phases.

Application of Intermetallic Compounds as Catalysts for the Selective Hydrogenation of CO2 to Methanol

AbstractDirect catalytic conversion of CO2 to methanol via renewable hydrogen has emerged as a promising technology among the various CO2 conversion techniques. However, efficient hydrogenation of CO2 using conventional Cu‐ZnO‐based catalysts, which are currently used for industrial methanol production from synthesis gas, remains a challenge due to inefficient energy conversion, poor stability and sluggish CO2 conversion kinetics. As the catalytic activity, stability and methanol selectivity of conventional Cu/ZnO catalysts are still insufficient for industrial applications, novel catalyst formulations using transition metals/metal oxides and supported noble metal nanostructures have emerged. Among them, intermetallic compounds are being explored for their unique electronic and crystalline structures, which can be tailored by controlled, precise, and seamless tuning of interatomic distances, specific arrangements and electronic structure to enhance their stability and activity for the selective hydrogenation of CO2 to methanol. In this context, intermetallic catalysts containing Pd, Cu and Ni combined with metal oxide nanoparticles (ZnO, Ga2O3, In2O3, etc.) have been shown to be more effective than the classical Cu‐ZnO‐Al2O3. This review analyses the progress made in the study of these intermetallic catalysts by analysing different aspects of their preparation, characterization, effects of promoters, support interactions, etc. Future research perspectives are discussed in the context of potential industrial applications of intermetallics for direct methanol production via CO2 hydrogenation.

Development of Silicalite-1 encapsulated Cu-ZnO catalysts for methanol synthesis by CO2 hydrogenation

Converting CO2 into fuels and valuable chemicals such as methanol has been gaining significant attention as a favorable solution for reducing greenhouse gas emissions. Although Cu-ZnO-based catalysts are promising candidates for this reaction since methanol is selectively produced at the Cu-ZnO interface, Cu are not stable at elevated temperatures (500–600 K), leading to decrease in the surface areas of Cu and Cu-ZnO interface due to thermal aggregation of Cu. Furthermore, the generation of H2O as a by-product in the CO2 hydrogenation does not only accelerate the aggregation of Cu, but also inhibits an intermediate (formate species) formation for methanol. This paper reports the development of a novel catalyst, annotated as CuPS@S-1 by immobilizing Cu phyllosilicate (CuPS) as the Cu source within hydrophobic zeolite of Silicalite-1 particles (S-1). Cu@S-1 was obtained after the reduction CuPS@S-1 and the size of the Cu particles was approximately 2.4 nm. Cu@S-1 exhibited a higher CO2 hydrogenation activity and methanol selectivity than Cu/S-1 prepared by an impregnation method. To further improve the methanol production activity, ZnO was loaded onto Cu@S-1 to form a Cu-ZnO interface. ZnO/Cu@S-1 was obtained by the impregnation of CuPS@S-1 powder with an ethanol solution containing zinc acetate, followed by calcination and reduction. The obtained catalyst exhibited a better methanol production yield where the space–time yield for methanol based on the Cu weight exceeded 1200 mgmethanol gCu−1h−1.

Mitigating Climate Change through Catalytic Conversions of CO2: A review

In the pursuit of a carbon-neutral economy, CO2 catalytic hydrogenation to methanol emerges as a pivotal technology for mitigating CO2 and addressing the manufacturing needs of future fuels, chemicals, and materials. The development of this technology not only offers solutions to environmental challenges, such as the greenhouse effect, but also facilitates the effective utilization of CO2 resources. The aims of this review is reveal intuitions into the structural and surface properties of heterogeneous catalysts, emphasizing the interface between metal and support. The exploration of these factors delves into their functions in reaction mechanisms, influencing catalytic activity, selectivity, and stability in CO2 hydrogenation to methanol.