Methanation Reaction Research Articles

Role of oxygen vacancies in CO2 methanation over zirconia: A mechanistic DFT and microkinetic study

The use of CO2 as a source of carbon for energy-storage through their transformation into methane represents an attractive approach in modern days. The development of stable and active catalysts as well as a deeper understanding of reaction mechanisms is essential in that field. Herein, the CO2 methanation reaction over zirconia was thoroughly investigated via DFT calculations and microkinetic modeling. The catalytic surface was represented by a monoclinic ZrO2 surface where CO2 adsorption and elementary hydrogenation steps have been systematically explored. It was demonstrated that the participation of an active oxygen vacancy (reduced surface) is crucial to activate the stable bonds of CO2 for further hydrogenation steps; the stoichiometric surface has a minor contribution to CH4 production. Two main reaction pathways were investigated: i) CO2 dissociation with later hydrogenations; (ii) H-assisted (early hydrogenation) mechanisms. It was demonstrated that the latter is kinetically favorable passing through a formate intermediate. Microkinetic simulations indicate that the initial adsorption configuration plays a central role to methane formation: more weakly adsorbed geometry happens to be more important. Thus, the present findings provide new insights and critical information on the role of oxygen vacancies to methanation mechanisms.

Synergistic effect of Ni and CeOx in NiCeOx/SSZ-13 catalyst for boosting activity and stability during dry reforming of methane

The stability of industrial catalysts for dry reforming of methane (DRM) reaction is still an urgent challenge. The multifunctional nanocatalyst of SSZ-13 supported Ni/CeOx bimetallic catalysts was successfully fabricated by the impregnation method. The Ni/CeOx species was dispersed highly in the microporous structure of SSZ-13, and the Ni active sites can activate the C-H bond dissociation of CH4, while the oxygen vacancy could promote the adsorption and activation of CO2. The NiCeOx/SSZ-13 catalyst showed excellent catalytic performance for dry reforming of methane, i.e., its conversion of CH4 and CO2 were 91 and 94%, and the ratio of H2/CO was about 0.88 at 750 °C after 50 h. Based on the results of CH4&CO2-TPSR and NH3-TPD, the synergy effect of NiCeOx species can promote the adsorption and activation of CH4 and CO2, and the coke on the surface during DRM is readily converted to CO by reacting with the surface oxygen from CeOx species, which effectively boost the elimination of carbon deposits. It highlights a new strategy for the fabrication of high-efficient zeolite catalysts for DRM to enhance the utilization of CH4 and CO2.

Internal dry reforming of methane in solid oxide fuel cells

In the context of global efforts to reduce greenhouse gas emissions and combat extreme global warming, the direct dry reforming of methane reaction in solid oxide fuel cells presents a promising avenue for clean energy production. This study delves into the influence of temperature, gas composition, and current density on the kinetics of dry methane reforming in solid oxide fuel cells. Power Law and Langmuir-Hinshelwood kinetic models were proposed to highlight the impact of operating conditions on dry methane reforming reactions. Results revealed that the feed gas composition strongly affects methane conversion, with higher methane contents resulting in lower conversions. Increasing the CH4/CO2 ratio increases reaction rates, and the effect decreases at a ratio of 1.25. The changes in methane concentration on dry methane reforming reaction rate are more significant than those for carbon dioxide. However, increasing carbon dioxide concentration enhances methane conversion. The exothermic nature of CO2 adsorption suggests that the adsorption process is thermodynamically favourable in dry reforming, and the elevated temperatures generally improve reaction rates and methane conversion by removing carbon deposits and providing the energy needed to break down the chemical bonds in methane which facilitating its transformation. A higher current density significantly enhances the CO2 adsorption equilibrium constant and further increases methane conversion, highlighting the positive role of electrochemical reactions on dry methane reforming. This study aims to fill the knowledge gap regarding the influence of electrochemical reactions on dry methane reforming behaviours in solid oxide fuel cells, offering critical insights for advancing anode design, thus contributing to the development of solid oxide fuel cell technologies to address global warming and reduce greenhouse gas emissions.

Study on the effect of promotors in CO2 utilization for syngas production via dry reforming of methane over Co-MOX/TiO2-Al2O3 (MOX = La, Ce, Mg, and K) catalysts

In this study, Co-based catalysts supported over Ti-Al oxide and promoted with La, Ce, Mg, and K metals were assessed for CO2 reforming of methane reaction to produce syngas. Titania-alumina mixed oxide supports were prepared using the template-assisted-solvothermal method, and then Co and promotors were co-impregnated over the as-prepared support. Different characterizations of catalysts showed that variation in promotor metal impacts these catalysts' physical and chemical properties. The Ti-Al oxide support possessed the perfect hexagonal morphology. Potassium-promoted catalysts possessed the highest number of basic sites, whereas the La-promoted catalyst possessed the highest number of acidic sites. La promotion improved the Co dispersion, while Mg promotion enhanced the metal support integration. La-promoted catalysts are deactivated because of active metal oxidation and the generation of hard carbon. The carbon was deposited in all catalysts; however, the activity of the Mg-promoted catalyst was unaffected. The intermediate surface basicity and strong metal support interaction improved the Mg-promoted catalyst's stability. The La and Mg-promoted catalysts possessed lower apparent activation energies.

Molybdenum-doping promoted surface oxygen vacancy of CeO2 for enhanced low-temperature CO2 methanation over Ni-CeO2 catalysts

It is challenging to improve the low-temperature activity of Ni-based catalyst for the CO2 methanation reaction. In this study, a molybdenum-doped cerium oxide supported Ni catalyst (Ni/MoCe) was constructed, and it showed remarkable CO2 methanation performance at low temperatures (<300 °C). Structural analysis revealed that the incorporation of Mo into the CeO2 lattice could enrich the surface oxygen vacancies, reduce the particle size of Ni species and enhance the metal-support interaction. The Ni/MoCe demonstrated a faster HCOO* pathway for the conversion of CO2 to CH4 compared with Ni/CeO2. Besides, the rich surface oxygen vacancies in Ni/MoCe facilitated the adsorption form of bidentate carbonates and the enhanced Ni-CeO2 interaction reduced the approach resistance of active H species from Ni for subsequent hydrogenation process. This work proves that Mo doping is an effective vacancy engineering strategy to design high-performance heterogeneous catalysts for CO2 hydrogenation.

Thermally stable Ni foam-supported inverse CeAlOx/Ni ensemble as an active structured catalyst for CO2 hydrogenation to methane

Nickel is the most widely used inexpensive active metal center of the heterogeneous catalysts for CO2 hydrogenation to methane. However, Ni-based catalysts suffer from severe deactivation in CO2 methanation reaction due to the irreversible sintering and coke deposition caused by the inevitable localized hotspots generated during the vigorously exothermic reaction. Herein, we demonstrate the inverse CeAlOx/Ni composite constructed on the Ni-foam structure support realizes remarkable CO2 methanation catalytic activity and stability in a wide operation temperature range from 240 to 600 °C. Significantly, CeAlOx/Ni/Ni-foam catalyst maintains its initial activity after seven drastic heating-cooling cycles from RT to 240 to 600 °C. Meanwhile, the structure catalyst also shows water resistance and long-term stability under reaction condition. The promising thermal stability and water-resistance of CeAlOx/Ni/Ni-foam originate from the excellent heat and mass transport efficiency which eliminates local hotspots and the formation of Ni-foam stabilized CeAlOx/Ni inverse composites which effectively anchored the active species and prevents carbon deposition from CH4 decomposition.

Effect of modified surface of Co/Al2O3 on properties and catalytic performance for CO2 reforming of methane

This work objective is to reveal the advantages of the 10 wt%Co/Al2O3 catalyst that the Co surface was constructed through the impregnation associated with the 6 h of ammonia vapor diffusion (10Co(T)/Al2O3). The modified surface catalyst was characterized and tested for CO2 reforming of methane reaction (CRM) that converts two main greenhouse gases into H2 fuel and syngas. Compared with the 10 wt%Co/Al2O3 catalyst that the Co surface formed by traditional impregnation (10Co/Al2O3), the characterization outcome examined the creation of high-dispersive Co species on the modified surface catalyst. The dispersion of cobalt oxide derived by this method provided more Co2+/Co3+ on the surface, collaborated with the stronger metal-support interaction, which generates more oxygen vacancies. Consequently, this modified Co surface on 10 wt%Co/Al2O3 catalyst demonstrated higher activities and prevented the deposition of the hardest removable coke type during the CRM reaction time-on-stream. Overall, the Co surface of 10 wt%Co/Al2O3 catalyst prepared by impregnation associated with the 6 h of ammonia vapor diffusion had formed a high dispersion of small Co2+/Co3+ connecting with the support that developed abilities of Co/Al2O3 catalyst into a more practical CRM catalyst.

Improved Structural Description of Different γ-Al2O3 Materials Using Disordered δ5-Al2O3 Phase via X-ray Pair Distribution Function Analysis

Extensive research has been conducted in the past on the crystallographic characteristics of γ-Al2O3 support materials due to their advantageous properties in heterogeneous catalysis. While their structure is most commonly described as spinel, their intrinsic disorder and nanostructure have prompted alternative models involving tetragonal space groups, supercells, or occupancy of non-spinel positions. X-ray pair distribution function (PDF) analysis has further postulated the existence of short-range order domains with structural remnants from boehmite precursors from which γ-Al2O3 is commonly prepared via calcination. In this PDF study, we now show that a recently theoretically found monoclinic δ5-Al2O3 phase is, in fact, best suited for describing the structure of different commercial Al2O3 supports, as well as a self-prepared and an industrial Ni/Al2O3 methanation catalyst. Furthermore, in situ experiments under catalytic cycling in the methanation reaction demonstrate that the nanoscale structure of this δ5 phase is preserved during cycling, pointing towards the high stability of the therein-represented disorder. A complete description of the disordered Al2O3 support structure is crucial in the field of heterogeneous catalysis in order to distinguish disorder within the bulk support from additional interfacial restructuring processes such as surface oxidation or spinel formation due to nanoparticle–support interactions during catalytic cycling in in situ scattering experiments.

Developing a numerical model for microbial methanation in a depleted hydrocarbon reservoir

Biological methanation is a promising option for CO2 utilization and energy storage. While the underground condition is not appropriate for a methanation reaction, microorganisms act as a catalyst and make the reaction possible. This study investigates the performance of biological methanation in depleted gas reservoirs using numerical simulation. To do this, a one-dimensional synthetic homogeneous depleted gas reservoir is modeled with the two-phase flow comprising components H2, CO2, CH4, and H2O. Then, the simultaneous injection of CO2 and H2 into the reservoir is numerically simulated to evaluate the methane production rate in MATLAB Reservoir Simulation Toolbox (MRST) open-source software. Long-term results show propagating composition waves and pressure profiles. Sensitivity analysis reveals that methane production is positively correlated with the initial reservoir pressure and the number of methanogenic microorganisms, but negatively correlated with the temperature and the bacterial decay rate. The bacterial growth rate has an insignificant effect on methane production in this model. The bacterial population is the most critical parameter, as 1e7 methanogenic microorganisms per cubic meter of aqueous phase can produce 96% pure methane after 12 years. Overall, the work demonstrates harnessing in-situ bio-reactions to utilize CO2 and recover depleted gas reservoirs.

Simulation of Underground Coal-Gasification Process Using Aspen Plus

In order to study the underground coal-gasification process, Aspen Plus software was used to simulate the lignite underground gasification process, and a variety of unit operation modules were selected and combined with the kinetic equations of coal underground gasification. The model can reflect the complete gasification process of the coal underground gasifier well, and the simulation results are more in line with the experimental results of the lignite underground gasification model test. The changes in the temperature and pressure of oxygen, gasification water, spray water, and syngas in pipelines were studied, and the effects of pipe diameters on pipeline conveying performance were investigated as well. The effects of the oxygen/water ratio, processing capacity, and spray-water volume on the components of syngas and components in different reaction zones were studied. In addition, the change tendency of gasification products under different conditions was researched. The results indicate that: (1) The depth of injection and the formation pressure at that depth need to be taken into account to determine a reasonable injection pressure. (2) The liquid-water injection process should select a lower injection pressure. (3) Increasing the oxygen/water ratio favors H2 production and decreasing the oxygen/water ratio favors CH4 production. (4) The content of CO2 is the highest in the oxidation zone, the lowest in the reduction zone, and then increases a little in the methanation reaction zone for the transform reaction. The content of CO is the lowest in the oxidation zone and the highest in the reduction zone. In the methanation reaction zone, CO partially converts into H2 and CO2, and the content of CO is reduced. (5) The injection of spray water does not affect the components of the gas but will increase the water vapor content in the gas; thus, this changes the molar fraction of the wet gas.

Dry reforming of methane over Ni–Mg–Al and Ni–Ca–Al type hydrotalcite-like catalysts: effects of synthesis route and Ru incorporation

Abstract Ni-incorporated Mg–Al type hydrotalcite-like catalytic materials were synthesized following impregnation and co-precipitation routes, and their catalytic performances were compared in the dry-reforming reaction of methane. The effects of Ru impregnation on the catalytic performance of Ni-incorporated Mg–Al were also investigated. Results showed that the catalytic performance of the Ni-incorporated Mg–Al type catalyst (NiMgAlO), which was prepared by the co-precipitation route, was highly stable during dry-reforming reaction tests performed at 600 °C, extending up to 24 h. The fractional conversion of CO2 (0.42) was higher than the fractional conversion of CH4 (0.29) due to the contribution of the reverse water gas shift reaction. However, the contribution of the reverse water gas shift reaction to the product distribution was much less with the catalyst prepared following the impregnation route (Ni@MgAlO). This difference was shown to be mainly due to the state of the nickel in the catalyst structures. Ni-impregnated Ca–Al type hydrotalcite-like catalyst (Ni@CaAlO) was also synthesized and tested in dry reforming of methane. Results obtained with the Ni-impregnated Ca–Al type catalyst showed some changes in its structure and the formation of some CaCO3 during the dry reforming reaction. The comparison of the performances of Ni-impregnated Mg–Al and Ca–Al type catalysts showed a higher amount of coke on the surface of Ni@CaAlO than Ni@MgAlO. It was also concluded that significant coke minimization and highly stable catalytic performance could be achieved by the impregnation of 1 % Ru to the NiMgAlO catalyst. The amount of coke deposited on the catalyst decreased from about 30 % to less than 5 %, by Ru impregnation. The decrease of the surface area of the Ru-impregnated catalyst was also only about 3 % after 240 min of reaction time.

Identification of the active sites for CO2 methanation over Re/TiO2 catalysts

CO2 methanation on heterogeneous catalysts holds great significance in achieving the net-zero emission target. However, understanding the atomic-scale relationship between reactivity and active site has been a subject of debate. The study investigated CO2 methanation reaction catalyzed by Re/TiO2 catalysts and identified the active site distribution and its relationship with reactivity. The low-coordinated edge sites of Re nanoparticle were found to be the active sites where CO2 dissociated into CO via a carbide pathway and subsequently hydrogenated to form methane. Furthermore, the study revealed that the size of Re nanoparticle influenced the distribution of active edge sites and affected the reactivity and stability of the CO intermediate, which was the rate-determining step in CO2 methanation reaction. Controlling the size and structure of Re nanoparticle can, therefore, enhanced the activity and efficiency of CO2 methanation reaction. The identification of these active sites and the insights gained from this study have significant implications for the mechanistic understanding and optimization of CO2 methanation over Re/TiO2 catalysts. It provides a basis for designing more effective catalysts to facilitate the conversion of CO2 to methane, thereby contributing to the goal of achieving net-zero emissions.

FUTURE RESEARCH DIRECTIONS IN THE PARTIAL OXIDATION OF METHANE TO METHANOL OVER COPPER‐CONTAINING ZEOLITES

The direct partial oxidation of methane to methanol is a potentially transformative approach to upgrading methane to higher value molecules. Copper‐exchanged zeolites show potential to achieve this aim and have been extensively reported and reviewed in the open literature. This concept paper highlights selected works that point to knowledge gaps in this space, which opens opportunities for further breakthroughs. Specifically, these literature reports highlight the need for 1) additional research exploring how reactor operating conditions (space velocity, feed composition, temperature) can be optimized to improve methanol selectivity, 2) developing a better understanding of how the zeolite topology impacts the reactivity of methane, and 3) how different methods of loading copper into the zeolite impact reactivity.

Ceria-supported Ni catalyst with high catalytic activity, selectivity and stability for CO2 conversion to CH4 by hydrogenation reaction investigated by X-ray absorption spectroscopy

x%Ni/CeO2 (x = 3, 6, 9, 12 and 18 wt%) catalysts were synthesized for CO2 methanation reaction. The catalysts were prepared via sol-gel method with co-adding of citric acid to improve Ni dispersion. 18 wt%Ni/CeO2 exhibited the highest catalytic performance. An in-situ experiment during CO2 methanation for monitoring the oxidation state changes of Ni and Ce was conducted by TRXAS. The oxidation states of Ni2+ and Ce4+ were reduced upon increasing the reduction temperature. Moreover, Nio and Ce3+ remained unchanged during reaction. The operando XAS experiment was performed to investigate the electronic state changes of Ni species during fluctuating conditions. The state of Nio remained unchanged upon H2 dropout and re-purging, which indicated that Ni species were completely re-reduced after H2 was added into the feed stream again. The completely reduced behavior of Ni active species was caused by highly dispersed Ni by the addition of citric acid.

Reactivities and Bohmian perspectives on pnictogen N-heterocyclic carbene analogues reactions with methane and ethene

The chemical reactions of monocationic pnictogen N-heterocyclic carbene (NHC) analogues [(tBu2DAB)M+, M = N, P, As, Sb, and Bi, and tBu2DAB =1,4-tert-butyl-1,4-diaza-1,3-butadiene] with methane and ethene are studied by the density functional theory. The activation energies and reaction enthalpies are analyzed by the natural energy decomposition analysis (NEDA) to understand the reactivities of the reactions. The activation energies and reaction enthalpies of the ethene reactions, and the activation energies of the methane reactions decrease with the atomic numbers of the pnictogen elements M. However, the reaction enthalpies of the methane reactions do not follow a monotonic trend because the size and geometry of the methane structure are better accommodated by the product states of (tBu2DAB)P+ than (tBu2DAB)N+. The NEDA also suggests that the carbene and hydrocarbon fragments are subject to singlet–singlet interactions for all reactions of this work. The electronic and energetic structures of the reactions involving the N-centered NHC reactant, (tBu2DAB)N+ characteristically differ from all other carbenic reactants, which is in agreement with the well-known fact that the 2s and 2p orbitals of the N atom are more amenable to hybridization than the higher s and p orbitals of other pnictogen elements. The Bohmian perspectives on the stationary states of the pnictogen NHC reactions are also explored. It is found that the Bohmian potentials may reveal some bonding informations of the complexes, but further investigations are still required for deeper understanding.

Exploring optimal total metal loading of Ni3Fe/Al2O3 catalyst for CO2 methanation and its kinetic model

A series of Al2O3-supported bimetallic Ni-Fe catalyst with Ni/Fe = 3 are prepared, characterized, and examined for CO2 methanation to identify the total metal loading (Ni+Fe) that yields the maximum activity. The XRD patterns of all catalysts exhibit a noticeable peak shift, which suggests alloy formation and XPS studies reveal that the near-surface concentration of the reduced catalysts possess Ni/Fe ratios similar to those targeted. Analysis of the particle size distribution from TEM and degree of reduction from TPR clearly shows that an increase in metal loading results in a gradual decrease in effective dispersion. However, the catalyst with 55% total metal loading of Ni+Fe, 55Ni3FeAl, possessed the maximum surface metal sites and effective surface metal area, which is reflected in the highest activity of this catalyst during CO2 methanation. Kinetic measurements of the CO2 methanation reaction are obtained on 55Ni3FeAl at temperatures ranging from 513 to 533 K and ambient pressure under differential reactor conditions and in the absence of heat and mass transfer resistance. Several kinetic models are then considered to fit the reaction data for CO2 methanation. The parameters of the models are determined by non-linear regression and analyzed for their thermodynamic consistency and statistical validity (R2, R2adj, NRMSE and F - test). The kinetic data of CO2 methanation on 55Ni3FeAl is adequately represented by a reaction model, where the surface reaction between molecularly adsorbed CO2 and adsorbed H2 appears to be the rate-determining step. The activation energy of this rate determining step was 136 kJ/mol. This kinetic model can then be used to design, analyze, and control different reactors where the most active Al2O3 supported Ni-Fe catalyst with Ni/Fe = 3, 55Ni3FeAl, is used for the CO2 methanation reaction.

Nano-crystalline NiO-MgO/NiAl2O4 catalyst for coking free low temperature partial oxidation of methane

Here, we report an ultra-small-sized nano-crystalline NiO-MgO/NiAl2O4 catalyst for coking-free partial oxidation of methane reaction at low temperature (450 °C). The catalyst was tested in a packed-bed reactor over a temperature range of 350 to 850 °C. The NiO-MgO/NiAl2O4 catalyst was optimized for calcination temperature and nickel content. The best-optimized sample was then tested for different gas hourly space velocities (GHSVs), resulting in 99 % CH4 conversion and varying H2/CO selectivities from 90 % to 70 % at 450 °C. A stability test was conducted at 500 °C for 100 h for stream on reaction conditions, resulting in 95 % CH4 conversion, 90 % H2 selectivity, and 60 % CO selectivity without any significant deactivation. The excellent catalytic activity and stable performance were attributed to the ultra-small size and nanocrystalline structure of NiO-MgO, as well as the presence of lattice oxygen reservoirs. Additionally, the synergistic interaction between the NiO-MgO solid solution and the support NiAl2O4 contributed to these properties.

Transforming CO2 to valuable feedstocks: Emerging catalytic and technological advances for the reverse water gas shift reaction

Current conditions suggest that to mitigate climate change, carbon neutrality must be achieved. Despite efforts to reduce carbon dioxide emissions, existing strategies remain inadequate. Thus, it is inevitable that carbon dioxide utilization will play a crucial role in the fight against climate change. Among the conversion routes available, the reverse water–gas shift reaction (RWGS) is promising as it allows the conversion of CO2 to CO, which can then be further converted to other valuable feedstocks while utilizing renewable H2. However, this route presents several challenges, as the RWGS reaction requires high energy input and is less favored over the methanation reaction at lower temperatures. Hence, the development of novel catalysts and advanced technologies is necessary to achieve high conversions and selectivity. This review summarizes the most recent progress and advances in heterogenous catalyst systems and emerging technologies explored for the RWGS reaction. Techniques to enhance catalyst performance, alter reaction mechanisms, and improve catalyst stability are discussed. Novel technologies and their recent developments to achieve equilibrium conversions and improve CO yield are also given focus and compared. This review thus provides insight into the possibilities available for improving the RWGS reaction as a practical carbon mitigation route.

NiGa nano-alloy for the dry reforming of methane: Influences of Ga alloying with Ni on the catalytic activity and stability

The massive emission of CO2 and CH4 has caused serious environmental and ecological problems, and dry reforming of methane reaction has received widespread attentions due to the fact that it can eliminate the two gas simultaneously. Herein, Ni60Ga40/Al2O3 (molar ratio of Ni:Ga was 60:40) catalyst was synthesized by mechanochemical synthesis method, offering 75 % CH4 conversion, 85 % CO2 conversion, and H2/CO ratio of 0.93 at 750 °C during 120 h test. Ni in Ni60Ga40/Al2O3 combines with Ga to form Ni3Ga intermetallic compound, which inhibits the sintering of Ni and rapid cracking of CH4. Moreover, the extra Ga species, existing in the form of Ga2O3-Al2O3 with abundant oxygen vacancy, boosts CO2 activation and prevents carbon development on catalyst surface. In contrast, for the pure Ni/Al2O3 and Ga/Al2O3 catalysts, the stability and catalytic activity couldn’t be obtained synchronously. This work particularly investigated the CH4 dissociation and CO2 activation for the NiGa/Al2O3 catalysts, establishing the foundation for rational design of low-cost performance catalysts for the dry reforming of methane reactions.

Carbon modified active pairs of Co-Co2C for CO2 hydrogenation to alcohols

The transformation process of CO2-to-alcohols can achieve the reduction in emissions of carbon dioxide and hydrogen storage, considered to be the up-and-coming way to realize the utilization of CO2. Co-based catalysts are promising, where Co0/Coδ+ is the critical active pair. The challenge is how to construct and tailor the active pair of Co0/Coδ+, to which a new scheme has been proposed in this work. Dual active sites of Co-Co2C were constructed and tailored by the carbon deposition via catalytic decomposition of methane reaction in this scheme. The formation of Co2C species promoted the non-dissociation of COx intermediates, which greatly contributed to the synthesis of alcohols. Not only the state of the Co active component changed with the addition of carbon species, but its own electron-donating effect increased the activation rate of CO2. The catalyst exhibited a CO2 turnover frequency of 7.4 × 10−3 s−1, 16.9 C-mol% and 29.5 C-mol% for ethanol and methanol selectivity at 270 °C and 3 MPa, respectively. This study provides a reference for catalyst design with the help of carbon species to modulate the state of active components.