Search

CO methanation has arisen as an attractive research area due to its ability to transform syngas into substituted natural gas. Current monometallic catalysts have a severe problem; quickly deactivated. It is generally known that by introducing another metal to create a bimetallic catalyst, synergistic interaction between both metals considerably enhances catalyst effectiveness. This paper provides a detailed overview of bimetallic catalysts for CO methanation, covering its synthesis method and effect on physicochemical characteristics. The bimetallic catalyst can both reinforce or weaken the metal-support and metal-metal interaction, which weakening it favors reducibility while reinforcing it favors stability. Particle size and dispersion also improve, whereas adding lanthanides can increases the basicity. We also present the mechanism of CO methanation over the bimetallic catalyst, which modifies the mechanism's energy and rate value. This review provides insights on how reaction effectiveness is enhanced, enabling catalyst development with the highest possible performance.

A new catalyst composition comprised of Ni, Ru, and MgO was investigated with a focus on improving methanation performance for sub-stoichiometric H2/CO-ratio producer gas from biomass gasification. The catalyst was loaded on an alumina support by wet impregnation for testing the catalytic methanation activity for syngas (CO/H2) and producer gas (CO/CO2/H2) in a fixed-bed reactor. The optimum addition of promoters Ru and MgO to the main Ni catalyst was determined by maximizing the CO conversion and CH4 yield in the methanation reactions. The optimization experiments were conducted on a low-surface-area alumina support. With 10% Ni loading, the highest activity and stability was achieved with the addition of 1.5%MgO and 0.5-1.0% Ru as promoters. X-ray Photoelectron Spectroscopy (XPS) of Ni in pretreated Mg-Ni and Ni-Ru-Mg catalysts indicated the presence of approximately 30% of Ni in metallic state on the Al2O3 support. Bulk reduction, measured by TPR, was nearly 40% in the Mg-Ni-Ru catalysts. The MgO promoter enhanced the methanation activity, while the Ru component was mainly responsible for improvement in catalytic stability in the low H2/CO-ratio (1.82) feed gas. The effect of the presence of H2O in the feed gas showed no significant change in the methanation activity of the catalyst. The Ni-Ru-Mg catalyst showed much higher stability in comparison to a promoted Ni-based commercial catalyst. The CO in the low H2/CO-ratio feed gas was primarily responsible for catalyst deactivation due to coke formation. Experiments with high-surface-area commercial alumina supports with the Ni-Ru-Mg catalyst demonstrated CO conversion activity comparable to a commercial catalyst but eliminated deactivation due to coke formation at the low H2/CO-ratio producer gas commonly found in the gasification of biomass.

Ni-Al mixed metal oxides have been successfully prepared by high shear mixer (HSM) and coprecipitation (CP) methods for low temperature CO methanation. In this work, Ni-Al (HSM-CP) catalyst presented small Ni crystallite size and high surface area, which all contribute to the methanation reaction at low temperature conditions. The obtained Ni-Al (HSM-CP) sample exhibited a mass of defective oxygen, thereby accelerating the dissociation of CO and ultimately increasing the activity of the catalyst. Ni-Al (HSM-CP) catalyst offered the best activity with CO conversion=100 % and CH4 selectivity=93 % at 300 ℃, and the CH4 selectivity can reach 81.8 % at 200 °C. In situ Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) show that CHO and COH intermediates with lower activation energy barriers are produced during the reaction, and hydrogen-assisted carbon-oxygen bond scission is more favorable.

Exfoliated 2D MAX Ti3AlC2 conductive cocatalyst anchored with g-C3N4/TiO2 to construct 2D/0D/2D heterojunction has been explored for enhanced CO2 photoreduction in a fixed-bed and monolith photoreactor. The TiO2 particle sizes (NPs and MPs) were systematically investigated to determine effective metal-support interaction with faster charge carrier separation among the composite materials. When TiO2 NPs were anchored with 2D Ti3AlC2 MAX structure, 10.44 folds higher CH4 production was observed compared to anchoring TiO2 MPs. Maximum CH4 yield rate of 2103.5 µmol g−1 h−1 achieved at selectivity 96.59% using ternary g-C3N4/TiO2/Ti3AlC2 2D/0D/2D composite which is 2.73 and 7.45 folds higher than using binary g-C3N4/Ti3AlC2 MAX and TiO2 NPs/Ti3AlC2 samples, respectively. A step-scheme (S-scheme) photocatalytic mechanism operates in this composite, suppressed the recombination of useful electron and holes and provides higher reduction potential for efficient CO2 conversion to CO and CH4. More importantly, when light intensity was increased by 5 folds, CH4 production rate was increased by 3.59 folds under visible light. The performance of composite catalyst was further investigated in a fixed-bed and monolith photoreactor and found monolithic support increased CO production by 2.64 folds, whereas, 53.99 times lower CH4 production was noticed. The lower photocatalytic activity in a monolith photoreactor was due to lower visible light penetration into the microchannels. Thus, 2D MAX Ti3AlC2 composite catalyst can be constructed for selective photocatalytic CO2 methanation under visible light in a fixed-bed photoreactor.

In this paper, we present a parallelized microfluidic device with improved ladder–tree distributors for the scaled-up production of monodisperse microspheres. Owing to the improved distribution form comprising a ladder distributor in the center and tree distributors around the circumference, the uniformity of the generated droplets for our device was improved by 32.9% and 86.1% compared to those achieved in devices with conventional tree and ladder distributors, respectively, in the final production stage with 32 droplet generators, indicating the potential of our device for further scale-up while maintaining the monodispersity of the generated droplets. The effect of the 2D scale-up of our device was investigated by varying the continuous-phase flow rate and viscosity. Using our device, γ-Al2O3 microspheres with a diameter of 598.1 μm and a CV of 2.58%, as catalyst support for microreactors, were continuously synthesized at high production rate. The nickel-based catalyst prepared from γ-Al2O3 microspheres with large specific surface area and pore volume had an average NiO size of 14 nm, which was 60.9% of that supported on industrial support. The CO methanation conversion of the Ni@Al2O3 microspheres was 1.7 times larger than Ni@Al2O3 industrial support at 140 °C.

Active and selective structured RuO/AlO catalysts for CO methanation using a flow simulating CO-rich reformate gases from WGS and PROX units (H excess, CO presence and 300 ppm CO concentration) were prepared. Both, the RuO/AlO powder and the slurry prepared from it for its structuration by washcoating of the metallic micromonolithic structure, were also active and selective. Both the slurry (S-RuAl) and micromonoliths (M-RuAl) were able to completely and selectively methanate CO at much lower temperatures than the parent RuAl powder. The optimal working temperature in which the CO conversion is maximum and the CO conversion is minimized was determined to be from 149 °C to 239 °C for S-RuAl and from 165 °C to 232 °C for M-RuAl, whilst it was from 217 °C to 226 °C for RuAl powder. TPR, XRD and TEM measurements confirmed that the changes in the activity and selectivity for CO methanation among the considered catalysts can be related with modifications in the surface particle size of ruthenium and its reducibility. These were ascribed to the metallic substrate, the presence of PVA and colloidal alumina in the slurry preparation, the aqueous and acidic media and the thermal treatment used, resulting in a more active and selective catalysts than the parent powder.

CO2 methanation is the catalytic reduction of CO2 to methane, which is accompanied by side reactions that produce CO. Being an equilibrium-limited exothermic reaction, thermal management is essential for good reactor performance. We analyze efficient thermal coupling by transferring the heat of reaction from outlet to the inlet stream in a single thermally-integrated microreactor with counter-current flow. We use CFD simulations to compare two modes of heat removal, viz. external cooling and feed dilution, over a wide range of operating conditions. In one mode of operation, undiluted feed is processed with external cooling using air in counter flow (air-cooled reactor) and in the other, diluted reactant mixtures in alternate channels exchange heat counter-currently as the reaction proceeds (counter-current reactor). Depending on the inlet temperature, a favorable temperature profile that improves conversion to methane forms in each reactor. For the base case, 67 % CO2 conversion is obtained, with CH4 selectivity of 88 % and 91 % in air-cooled and counter-current reactors, respectively. Counter-current reactor shows autothermal operation with feed at ambient temperature while air-cooled reactor gives good performance at higher inlet temperatures. It is possible to attain high selectivity to methane through appropriate choice of operating conditions.

In this work, the solution plasma-assisted method was used to prepare NiMnAl-LDO (layered double oxides) catalysts with different treatment times, which were used for the CO2 methanation reaction. Solution plasma treatment can enhance the dispersibility of the catalyst, create oxygen defects and improve the chemical adsorption capacity of the catalyst. The results show that the low-temperature activity of the catalyst has been improved after the solution plasma treatment. We demonstrate that the NiMnAl-LDO-P(20) catalyst with high dispersion has the highest catalytic activity in CO2 methanation (81.3% CO2 conversion and 96.7% CH4 selectivity at 200 °C). Even though working for 70 h, the catalyst is still highly stable. This work provides a great promise for improving the low-temperature activity of Ni-based catalysts.

In recent years, CO2 conversion reactions such as CO2 reforming of CH4 and CO2 methanation have devoted significant attention on account of their advantages in utilizing greenhouse gases (CO2 and CH4). The development of an excellent catalyst with great properties is a crucial strategy in the catalytic reaction, as it could enhance the efficiency of reaction. Additionally, the tunable characteristics of support materials may influence the distribution of active metal sites, strength of metal-supporting interactions, and amount of oxygen vacancies. To improve metal dispersion on a support, the production of support materials with fibrous morphology and dendrimeric structures is becoming an exciting approach. This short review highlighted recent developments in the preparation of fibrous catalysts and their relation with the physical and chemical properties of catalyst. This article also discussed the governing factor of fibrous morphology in CO2 conversions. Owing to the fascinating physicochemical properties of fibrous catalyst, further research is needed to explore its potential in various applications.

The aim of this work was to prepare and examine the catalytic activity of nanometric CeO2 decorated with transition metal oxides – Ni, Co, Cu, Fe and Mn – towards a high-temperature methanation process under SOEC CO2/H2O simulated co-electrolysis conditions. Samples were prepared using the wet impregnation method via the conventional process and with the addition of native cyclodextrin. The influence of β-cyclodextrin (βCD) onto the size, dispersion and integration of the obtained metal nanoparticles was investigated. The differences between the catalysts’ reducibility revealed that samples prepared from βCD-containing solutions, in most cases, resulted in the creation of smaller MexOy NPs on the surface of the substrate material compared to those prepared using traditional nitrate solutions. The samples containing Ni and Co were the only ones that observably catalysed methane synthesis. The high dispersion and integration of NPs prepared via the proposed synthesis route resulted in increased catalytic activity and enhanced stability, which was most pronounced for the Co-impregnated sample. The methane production peak for Ni-βCD/CeO2 at 375℃ was characterised by nearly 99% CO conversion and 80% selectivity towards CH4 production. Co-βCD/CeO2 reached 84% CO conversion and almost 60% methane selectivity at 450℃. The usage of CeO2 coupled with βCD for the preparation of catalysts for high-temperature methane synthesis for use in SOECs gave promising results for further application.

The present manuscript presents for the first time the structuring of a Ru/TiO2 catalyst that was achieved by means of the washcoating procedure using homemade metal micromonoliths (Fecralloy®) of 1330 cpsi. For this, an optimized formulation of the slurried catalyst as well as a reproducible protocol for the coating of the micromonoliths were successfully achieved. The obtained structured systems were tested in the selective CO methanation reaction and the effect of different variables over the catalytic performance were analyzed such as the amount of loaded catalyst in the micromonoliths, the temperature of reaction, the space velocity, and the amount of CO and H2 within the feed-stream. The study of all of these parameters allowed to establish optimal conditions to maximize the performance of the structured Ru/TiO2 catalyst and subsequently, this was tested under those cited conditions in long-term tests (∼375 h), including shut-down/start-up cycles, aiming to evaluate its catalytic stability. The system presented a considerable stability along the different test without loss of catalytic activity, being specially remarkable its resistance to the inclusion of shut-down/start-up cycles. Therefore, this study lays the foundations for future development of more sophisticated structured systems for the selective CO methanation based on the structuring strategy proposed.

A water-permeable membrane reactor is proposed to promote CO2 methanation with in situ removal of H2O. A two-dimensional CFD simulation model is built up and the effects of GHSV, H2O permeance and CO2/H2 permeation selectivity are investigated.

International audience; A series of nickel-cerium-promoted mesoporous silica (SBA-15) catalysts modified with different loadings of yttrium were synthesized by cetyltrimethylammonium bromide (CTAB)-assisted impregnation. The catalysts were tested in CO2 methanation reaction and characterized by N2 sorption, X-ray fluorescence (XRF), small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (XRD), H2 chemisorption, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR), CO2 temperature-programmed desorption (CO2-TPD), and thermogravimetric analysis coupled with mass spectrometry (TGA-MS). The best catalytic performance in CO2 methanation was found for Y-modified NiCe/SBA-15 catalysts compared to the unpromoted sample. The modification with 10 wt% of yttrium gave the highest CO2 conversion of 61% ± 2% at 350 °C. We attribute this increase to an improved dispersion of Ni, increased reducibility of Ni species, higher ratio of Ce3+/(Ce3+ + Ce4+), and increased moderate basicity found for 15Ni10Ce10Y/SBA-15. This paper shows that 10 wt% of Y loading not only improves the catalytic activity in CO2 methanation, but also gives stable performance. The tested 15Ni10Ce10Y/SBA-15 catalyst did not exhibit activity loss during 26 h of time-on-stream (TOS) experiment at 350 °C. Moreover, carbon deposits and sintered nickel particles could hardly be found in 15Ni10Ce10Y/SBA-15 catalyst used for 7 h.

A fundamental understanding of the effects of catalyst pellet structures and operation conditions on catalytic performance is crucial for the reactions limited by diffusion mass transfer. In this work, a numerical investigation has been carried out to understand the effect of catalyst pellet shapes (sphere, cylinder, trilobe and tetralobe) on the reaction-diffusion behaviors of CO methanation. The results reveal that the poly-lobe pellets with larger external specific surface area have shorter diffusion path, and thus result in higher effectiveness factors and CO conversion rates in comparison with the spherical and cylindrical pellets. The effects of operating conditions and pore structures on the trilobular catalyst pellet with high performance are further probed. Though lower temperature can contribute to larger effectiveness factors of pellets, it also brings about lower reaction rates, and pressure has little impact on the effectiveness factors of the pellets. The increase in porosity can reduce the pellet internal diffusion limitations effectively and there exists an optimal porosity for the methanation reaction. Finally, the height of the trilobular pellet is optimized under the given geometric volume, and the results demonstrate that the higher the trilobular catalyst, the better the reaction performance within the allowable mechanical strength range. © 2020 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd.. All rights reserved.

Methanation of CO2 using H2 obtained by renewable energy sources has been gaining attention as one of the promising options for utilizing captured CO2 and surplus power obtained when intermittent p...

An in-depth understanding of the influence mechanism of the nonprecious metal Fe promoter on CO2 methanation is of great significance to the optimal design of high-efficiency CO2 methanation cataly...

The century of urbanisation and industrialisation had a great impact on the environment due to the rapid growth of the flue gas sectors. Thus, green technology is enforced to convert carbon dioxide (CO2) gas into methane (CH4) gas as an alternative fuel in electricity generation, particularly coal and natural gas sources. Cerium (Ce) was recognised as one of the most basic and unique redox characteristics utilised in the promising methanation reaction among catalysts used. The trimetallic catalyst used in this work was prepared with Ce as the based catalyst and ruthenium/magnesium (Ru/Mg) as the impregnated metal. Response surface methodology projected the CO2 conversion to be less than 0.3% of the experimental value of 78.82% using the indicated parameters of 593 °C calcination temperature and 61 wt.% ratios. Ru/Mg/Ce/Al2O3 catalyst with 60 wt.% of Ce loading calcined at 600 °C produced 58.08% of CH4. The characterisation results revealed that CeO2, Mg(Al2O4), and RuO2 species were the active species for CO2 methanation selectivity, as observed in XRD and XPS analyses. The mesoporous structure and particle agglomeration resulted in a surface area of 147 m2/g.

Funding for this work was provided by King Abdullah University of Science and Technology (KAUST). The authors wish to thank and acknowledge to Dr. Serhii Vasylevskyi from KAUST-Core labs for his support during the Raman spectroscopy measurements, Dr. Natalia Morlanes for her assistance for the flow-reactor configuration, and Sandra Ramirez for the art work.

In the current work, a circulating fluidized-bed reactor for methanation was proposed and studied numerically. A three-dimensional (3D) model was built, and the model was validated with measurement...

High surface area alumina-supported cobalt oxides and carbides were synthesized using a one-pot reverse microemulsion method (followed by carburization for carbides). Two reverse microemulsion synthesis variations gave fine powders having specific surface areas ranging from 178−272 m2/g, consisting of cobalt oxide or cobalt carbide nanoparticles (5−10 nm) dispersed on γ-alumina (10−13 wt% cobalt loadings). The resulted materials were tested for CO2 hydrogenation. Although all materials (two oxides and two carbides) were catalytically active, only cobalt carbides showed high selectivity to CH4 formation (up to 99 %), while also being significantly more active and stable than corresponding cobalt oxides (up to 89 % CO2 conversion for carbides). Investigation by in situ FTIR has shown significant differences in the reaction intermediates indicating different reaction mechanisms of CO2 hydrogenation on cobalt oxide and cobalt carbide surfaces.

New alternative routes to traditional Fischer-Tropsch Synthesis (FTS) must be established to get a more efficient process from the point of view of energy and sustainability. Solar photocatalytic-assisted FTS is a promising new path to obtain fuels from renewable resources. However, proper photocatalysts must be designed to enhance the photocatalytic activity under solar/visible radiation. In this work, Fe and Co-doped TiO2 catalysts were synthesized by a traditional impregnated method and by a hydrothermal route. The oxygen vacancies generation on TiO2 photocatalysts was studied by Raman, XPS and Diffuse Reflectance Spectroscopy (DRS) and correlated with the decrease of the band gap and the photoactivity in the syngas conversion into solar fuels under solar radiation. Metal doping and H2 reduction treatment favour the oxygen vacancies generation that decreases the band gap from 3.3 eV for P25 to values as low as 2.2 and 2.5 eV for Fe- and Co-doped TiO2. This lower band gap increases the methanation activity under solar radiation. Moreover, this metal doping does not only affect the band gap and CO methanation activity under solar radiation but also the CC coupling, favouring the production of ethanol. Thus, in presence of P25, only CO2 and CH4 are obtained whereas the addition of Fe and Co enhances the CH4 generation and favours ethanol production. Therefore, the present work opens new opportunities for the photocatalytic Fischer-Tropsch conversion (PFTS) of crude syngas, which can be obtained from biomass or MSW gasification, into fuels under solar light.

In this study, we present a detailed investigation of a commercial iron-based high temperature water gas shift (HTWGS) catalyst (Johnson Matthey KATALCOTM 71-6) in a new application: the production of hydrogen from blast furnace gas (BFG), which originates from iron and steel manufacturing. During the lab-scale catalytic testing under BFG conditions the catalyst demonstrated: 1) high water gas shift activity and stability; 2) minimal methanation at reduced steam to CO ratios; 3) high resistance towards H2S impurities present in the feed. The results of post-characterization of the discharged samples confirm the robustness of KATALCO 71-6 towards BFG process conditions: no over-reduction of the catalytically active Fe3O4 phase and no formation of a less active FeS phase. An in situ X-ray absorption spectroscopy study revealed no over-reduction of the iron phase under BFG conditions and the stabilization of the iron phase by diffusion of chromium into the iron oxide matrix. The findings of this study demonstrate the suitability of the iron-based HTWGS catalyst KATALCO 71-6 for the production of hydrogen from BFG streams. Knowledge gained in this study is an essential step in the development and scale up of carbon capture and storage as well as carbon capture and utilization technologies, such as the sorption enhanced water gas shift (SEWGS) technology, aimed at reducing the CO2 footprint during steel manufacturing.

In this study, hydrogen and carbon nanotubes (CNTs) are simultaneously produced via a synergistic combined process of CO2 methanation (METH) and chemical vapor deposition (CVD) processes using biogas as a feedstock. METH process could upgrade CO2 containing biogas into CH4-rich gas which then decomposed into H2 and forming CNTs over CoMo/MgO catalyst by CVD process. The effects of Ce addition to CoMo/MgO were investigated. Comprehensive characterization confirms that all as-synthesized samples composed of well-aligned multi-walled carbon nanotubes (MWCNTs) with a narrow size distribution. The Ce addition improved CoMo dispersion on MgO, resulting in smaller and uniform CNTs. The small addition of Ce into CoMo/MgO catalyst could enhance the production CNTs yield. The higher Ce addition would, however, result in the CNTs yield decreased, attributed to a high basicity of CeO2 surface and a large coverage of CeO2 on the catalyst surface. The IG/ID increased with increased Ce addition, while the surface area monotonically decreased, attributed to a decrease in defects of nanotubes. In addition, this wisely combined process could result in a remarkable 100%CO2 elimination, while high CH4 conversion of 90% was obtained. The H2 production yield could gain more than 30 vol% with respect to H2 in the feed stream. The H2 yield and purity in the effluent gas stream were approximately 90%.

In order to investigate effects of morphology and crystalline phase of different Ni-phyllosilicate catalysts on the catalytic performance for CO2 methanation, nanotubular Ni-phyllosilicate and MCM-41 supported Ni-phyllosilicate were synthesized through hydrothermal reaction of sodium silicate or MCM-41 with nickel nitrate. On one hand, nanosheets attributing to 2:1 type nickel phyllosilicate (Ni3Si4O10(OH)2·5H2O) were uniformly grown on the surface of MCM-41 spheres to form the MCM-41 supported Ni-phyllosilicate (Ni/M). On the other hand, 1:1 type Ni-phyllosilicate with nanotubular morphology (Ni/N) was synthesized through the reaction of Na2SiO3 and nickel nitrate. After a series of tests and characterizations, it was found that Ni/N exhibited low thermal stability and poor anti-sintering property, leading to poor catalytic activity for CO2 methanation. On the contrary, Ni/M was very stable, which obtained unchanged morphology and fine Ni particles after 750oC-reduction, resulting in high catalytic activity and long-term stability for CO2 methanation. In all, morphology and crystalline phase of Ni-phyllosilicate obviously affected catalytic performance, and the supported Ni-phyllosilicate catalyst was much better than the nanotubular Ni-phyllosilicate for CO2 methanation in this work.

It has been well established that carbon dioxide (CO2) is one of the main greenhouse gasses and a leading driver of climate change. The chemical conversion of CO2 to substitute natural gas (SNG) in the presence of renewable hydrogen is one of the most promising solutions by a well-known process called CO2 methanation. There have been comprehensive efforts in developing effective and efficient CO2 methanation catalytic systems. However, the choice of competitive and stable catalysts is still a monumental obstruction and a great challenge towards the commercialization and industrialization of CO2 methanation. It is necessary to emphasize the critical understandings of intrinsic and extrinsic interactions of catalyst components (active metal, support, promoter, etc.) for enhanced catalytic performance and stability during CO2 methanation. This study reviews the up-to-date developments on CO2 methanation catalysts and the optimal synergistic relationship between active metals, support, and promoters during the catalytic activity. The existing catalysts and their novel properties for enhanced CO2 methanation were elucidated using the state-of-the-art experimental and theoretical techniques. The selection of an appropriate synthesis method, catalytic activity for CO2 methanation, deactivation of the catalysts, and reaction mechanisms studies, have been explicitly compared and explained. Therefore, future efforts should be directed towards the sustainable developments of catalytic configurations for successful industrial applications of CO2 utilization to SNG using CO2 methanation.

The efficiency of CO2 methanation was estimated through gas chromatography in the presence of Co–Fe catalysts. Scanning electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and Mossbauer spectroscopy were applied for ex-situ analysis of the catalysts after their test in the methanation reaction. Thermal programmed desorption mass spectroscopy experiments were performed to identify gaseous species adsorbed at the catalyst surface. Based on the experimental results, surface reaction model of CO2 methanation on Co–Fe catalysts was proposed to specify active ensemble of metallic atoms at the catalyst surface, orientation of adsorbed CO2 molecule on the ensemble and detailed reaction mechanism of CO2→CH4 conversion. The reaction step when OH group in the FeOOH complex recombined with the H atom adsorbed at the active ensemble to form H2O molecule was considered as the rate-limiting step.

In catalysis science, the electronic structure of the active site determines the structure-activity relationship of the catalyst to a large extent. Therefore, modulating the electronic structure has become a main route for the rational design of metal-based catalyst materials. In this work, we prepared a LaCoSiHx material that has more electronegativity and a lower workfunction than traditional supported Co-based catalysts. Using CO2 methanation as a model catalytic reaction, the facile dissociation of CO2 and CO (a key reaction intermediate) on the surface of the LaCoSiHx catalyst is observed by various experimental methods (e.g., in situ Raman and FTIR) at room temperature. Moreover, theoretical calculation results further show that LaCoSiHx has a much stronger capacity for carbon-oxygen bond activation than the Co surface. The intrinsic mechanism is attributed to the marked electron transfer from catalysts into the antibonding orbital of CO2 and CO.

A novel mixed oxide material, Fe-Ce0.1Zr0.9O2-Ag, has been tested as cathode, for the very first time, for one-step methane synthesis in a single temperature solid oxide electrolyser by electrolysing a H2/CO2 (4:1 v/v) mixture at 500 °C. Maximum methane selectivity and yield were 6.67 % and 2.66 %, respectively, at an applied potential of 1.6 V (corresponding to a current density of 3.94 mAcm-2). CO2 conversion (~ 40 %) was independent of the applied voltage. However, upon increasing the potential, CO% dropped monotonically with a commensurate increase in methane%. Calculations based on oxide ion removal as a function of current density confirmed that under loaded conditions steam generated in situ (via reverse water gas shift and methanation reactions) got electrolysed to H2, which reacted with CO producing more methane. Such excess methane produced purely electrolytically under loaded conditions matched well with the values predicted theoretically assuming that the decrease in CO% was solely due to enhanced methanation.

International audience

Solar-powered CO2 conversion represents a promising green and sustainable approach for achieving a carbon-neutral economy. However, the rational design of a wide-spectrum sunlight-driven catalysis system for effective CO2 reduction is an ongoing challenge. Herein, we report the preparation of a rhodium/aluminum (Rh/Al) nanoantenna photothermal catalyst that can utilize a broad range of sunlight (from ultraviolet to the near-infrared region) for highly efficient CO2 methanation, achieving a high CH4 selectivity of nearly 100% and an unprecedented CH4 productivity of 550 mmol·g-1·h-1 under concentrated simulated solar irradiation (11.3 W·cm-2). Detailed control experiment results verified that the CO2 methanation process was facilitated by the localized surface plasmonic resonance and nanoantenna effects of the Rh/Al nanostructure under light irradiation. In operando temperature-programmed Fourier transform infrared spectroscopy confirmed that CO2 methanation on the Rh/Al nanoantenna catalyst was a multistep reaction with CO as a key intermediate. The design of a wide-spectrum solar-driven photothermal catalyst provides a feasible strategy for boosting CO2-to-fuel conversion.

Integrated carbon capture and conversion of CO2 into materials (IC3 M) is an attractive solution to meet global energy demand, reduce our dependence on fossil fuels, and lower CO2 emissions. Herein, using a water-lean post-combustion capture solvent, [N-(2-ethoxyethyl)-3-morpholinopropan-1-amine] (2-EEMPA), >90 % conversion of captured CO2 to hydrocarbons, mostly methane, is achieved in the presence of a heterogenous Ru catalyst under relatively mild reaction conditions (170 °C and

Background The power-to-gas (PtG) method has significant potential as a strategy for storing excess renewable energy in the form of synthetic natural gas. PtG involves the hydrogenation of CO2 to CH4 from H2 obtained from renewable energy. Methods In this study, Ni–Fe catalysts with different Ni/Fe ratios were prepared for high-efficiency CO2 methanation using chemical reduction with an external magnetic field. The Ni–Fe catalysts were characterized by XRD, inductively coupled plasma, and SEM-EDS measurements, and their performance and chemical properties were measured by H2 temperature programmed reduction experiments. Significant findings The catalyst with the best performance for CO2 methanation had a ratio of Ni to Fe of 8/2 (Ni8Fe2). The Ni8Fe2 catalyst could convert over 80% of CO2 to methane at 150 °C. In addition, the CH4 selectivity of CO2 methanation was 95% when the reaction conditions were controlled at H2/CO2 = 4 and GHSV ∼1000 h−1. The low cost and simple preparation of these Ni–Fe catalysts have high potential for future commercialization.

CO2 methanation is a significant route to decrease carbon emission as well as realize carbon neutrality and has gained considerable concerns from experts in the environment and energy field currently. Herein, highly dispersed ruthenium nanoparticles entrapped in TiO2 nanotubes, labeled as Ru-in/TNT, were constructed and adopted for photo-thermal driven CO2 methanation. The Ru nanoparticles confined in the nanotube exhibited an enhanced CO2 methanation activity, especially under light irradiation. Multiple characterization techniques (XRD, XPS, UV–vis DRS, HRTEM, Raman, etc.) were conducted to reveal the effect of confinement synergy on photo-thermal catalytic performance. A boosted photo-generated electron-hole separation efficiency is achieved as a result of the confinement effect, yielding more hot electrons to accelerate methanation activity. This photo-assisted confinement synergy can be expected for constructing an efficient photo-thermal catalytic system.

In this study, a series of Ni catalysts supported on CeO2 with different morphologies including nanopolyhedrons (PH), nanorods (NR), nanoparticles (NP) and nanocubes (NC) was prepared via hydrothermal / wet impregnation method. The catalytic performance of as-prepared catalysts was evaluated for low-temperature CO2 methanation. The Ni/CeO2 catalysts exhibited a superior CO2 conversion and CH4 selectivity over METH®134, a commercial methanation catalyst. The following order of activity was experimentally found : Ni/CeO2-PH > Ni/CeO2-NR > Ni/CeO2-NP > Ni/CeO2-NC > METH®134. Among different CeO2 morphologies, the Ni/CeO2-NR catalyst exhibited the largest surface area and the highest reducibility, providing the high oxygen vacancies/oxygen storage capacity (OSC). Nevertheless, the strong metal-support interaction (SMSI) between Ni and Ce of the Ni/CeO2-NR catalyst determined by H2-TPR posed a negative impact on the CO2 conversion at low temperature. Unexpectedly, the Ni/CeO2-PH catalyst possessed a single crystalline CeO2 nanostructure of ca. 7.4 nm with relatively high surface area and high reducibility especially at low reduction temperature. Therefore, the Ni/CeO2-PH catalyst was found to be the optimum catalyst for low-temperature CO2 methanation.

Conversion of CO2 into chemicals is a promising strategy for CO2 utilization, but its intricate transformation pathways and insufficient product selectivity still pose challenges. Exploiting new catalysts for tuning product selectivity in CO2 hydrogenation is important to improve the viability of this technology, where reverse water-gas shift (RWGS) and methanation as competitive reactions play key roles in controlling product selectivity in CO2 hydrogenation. So far, a series of metal-based catalysts with adjustable strong metal–support interactions, metal surface structure, and local environment of active sites have been developed, significantly tuning the product selectivity in CO2 hydrogenation. Herein, we describe the recent advances in the fundamental understanding of the two reactions in CO2 hydrogenation, in terms of emerging new catalysts which regulate the catalytic structure and switch reaction pathways, where the strong metal–support interactions, metal surface structure, and local environment of the active sites are particularly discussed. They are expected to enable efficient catalyst design for minimizing the deep hydrogenation and controlling the reaction towards the RWGS reaction. Finally, the potential utilization of these strategies for improving the performance of industrial catalysts is examined., A series of metal oxide, phosphate, alloy, and carbide-based catalysts for selective CO2 hydrogenation are summarized, showing their abilities to switch CO2 methanation to RWGS.

The activity of reducible metal oxide Sm2O3, CeO2, and ZnO as Ni nanoparticles support was investigated for CO2 methanation reaction. CO2 methanation was carried out between 200 °C to 450 °C with the optimum catalytic activity was observed at 450 °C. The reducibility of the catalysts has been comparatively studied using H2-Temperature Reduction Temperature (TPR) method. The H2-TPR analysis also elucidated the formation of surface oxygen vacancies at temperature above 600 °C for 5Ni/Sm2O3 and 5Ni/CeO2. The Sm2O3 showed superior activity than CeO2 presumably due to the transition of the crystalline phases under reducing environment. However, the formation of NiZn alloy in 5Ni/ZnO reduced the ability of Ni to catalyze methanation reaction. A highly dispersed Ni on Sm2O3 created a large metal/support interfacial interaction to give 69% of CO2 conversion with 100% selectivity at 450 °C. The 5Ni/Sm2O3 exhibited superior catalytic performances with an apparent phase transition from cubic to a mixture of cubic and monoclinic phases over a long reaction, presumably responsible for the enhanced conversion after 10 h of reaction. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

In order to achieve green synthesis of MCM-41 and address the sintering problem of Ni-based catalyst supported on silica material, MCM-41 with regular spherical morphology was prepared using sodium silicate extracted from renewable equisetum fluviatile as silicon source, and then a group of nickel phyllosilicates were synthesized via the reaction of MCM-41 sphere and nickel nitrate under hydrothermal condition. Much denser nanosheets corresponding to lamellar nickel phyllosilicate were formed on the surface of MCM-41 sphere with the raise of hydrothermal temperature in the range of 180–220 °C, resulting in the nickel content varying from 17.2 to 41.8 wt%. Fine Ni particles with size smaller than 6 nm could be obtained on the 750oC-reduced catalyst owing to the strong nickel-silica interaction derived from Ni-phyllosilicate. After the addition of V2O5 promoter, Ni particle size was further reduced to around 4.5 nm at high Ni loading above 30 wt%. Vanadium species was in the mixed valence state of V(III), V(IV) and V(V) after reduction, which increased the electron cloud density of Ni0, resulting in high catalytic activity of the VOx-modified Ni-phyllosilicate catalyst for CO2 methanation. In a 100 h-400oC-lifetime test and 600 °C-steam hydrothermal treatment, the VOx-modified Ni-phyllosilicate catalyst also showed high long-term stability, excellent sintering resistance of metallic nickel particles and high hydrothermal stability due to the strong surface confinement effect of nickel phyllosilicate and promotion of VOx species. In all, this work provided a green synthesis of MCM-41 as well as an efficient Ni/SiO2 catalyst derived from nickel phyllosilicate for CO2 methanation.