CO2 Methanation Reaction Research Articles

Trace CO elimination in H2-rich streams with a wide operation temperature window: Co deposited CuO-CeO2 catalysts.

This work provides a new strategy to eliminate trace CO in H2-rich gas in a wide operation temperature window for the application of hydrogen fuel cells. We engineered Co deposited CuO-CeO2 catalysts with a Co/(Cu + Ce) molar ratio of 1/1 that manages to maintain the CO level at below 100 ppm from 85 to 240 °C in the H2-rich reformate stream. CO-PROX and CO methanation reaction respectively occurred in the low and high temperature ranges. Multiple characterization techniques demonstrate that the molar ratio of Co/(Cu + Ce) significantly affects the synergistic interactions between the Cu, Co and Ce species, and ultimately the CO oxidation and CO methanation reactions. At low reaction temperatures, the Cu-Ce interaction mainly dominates the CO-PROX process, while at high reaction temperatures, CO methanation reaction takes place due to the reduction of Co3O4 to Co0 and the Co-Ce interaction takes charge of the CO methanation. Moreover, the increment of Co/(Cu + Ce) from 1/2 to 1 gives rise to the reprecipitation of the partially dissolved Cu species on Co3O4, which strengthens the Cu-Co interaction and stabilizes surface Cu+ and Co3+, thus promoting the low temperature CO-PROX catalytic performance.

The Effects of Ce and W Promoters on the Performance of Alumina-Supported Nickel Catalysts in CO2 Methanation Reaction

The influence of Ce and W promoters on the performance of alumina-supported nickel catalysts in the CO2 methanation reaction was investigated. The catalysts were obtained by the co-impregnation method. Nitrogen low-temperature adsorption, temperature-programmed reduction, hydrogen desorption, transmission electron microscopy, X-ray diffraction, and photoelectron spectroscopy studies were used for catalyst characterization. An introduction of Ce and W promoters (1–5 wt %) led to the decrease in mean Ni crystallite size. Gradual increase in the active surface area was observed only for Ce-promoted catalysts. The increase in CO2 conversion in methanation reaction at low-reaction temperatures carried out over Ce-promoted catalysts was attributed to the increase in the active surface area and changes in the redox properties. The introduction of small amounts of tungsten led to an increase in the activity of catalysts, although a decrease in the active surface area was observed. Quasi in situ XPS studies revealed changes in the oxidation state of tungsten under CO2 methanation reaction conditions, indicating the participation of redox promoter changes in the course of surface reactions, leading to an improvement in the activity of the catalyst.

Insight into the role of Fe on catalytic performance over the hydrotalcite-derived Ni-based catalysts for CO2 methanation reaction

A series of Fe modified hydrotalcite-derived Ni-based catalysts (Ni3Fex-calc) were synthesized to evaluate the effect of Fe on CO2 methanation performance over Ni3-calc catalyst. The results showed that Ni3–Fe0.5-calc had superior catalytic activity with 78% CO2 conversion rate at 200 °C. The addition of moderate amount of Fe can effectively improve the reducibility, enrich the medium basic sites of Ni3-calc catalyst, and further facilitate the adsorption and activation of CO2. This resulted in the outstanding low-temperature CO2 methanation activity, as well as the enhanced resistance of carbon deposition. In-situ DRIFTS results indicated that the CO2 methanation reaction mechanism involved a progressive hydrogenation of carbonate and formate species to methane route. The formate species was the main intermediates during CO2 methanation. The introduction of Fe could significantly accelerate the hydrogenation rate of carbonates and formate species.

Unraveling catalytic properties by yttrium promotion on mesoporous SBA-16 supported nickel catalysts towards CO2 methanation

The ordered mesoporous silica SBA-16 with high specific surface area and pore volume was synthesized and used to prepare Ni/SBA-16 catalysts promoted with yttrium. These promoted catalysts were tested in CO2 methanation reaction and characterized by N2 sorption, small-angle/wide-angle XRD, TEM, XPS, H2-TPR, CO2-TPD, and TGA/DSC-MS. The results revealed that Ni/Y/SBA-16 catalysts performed better catalytic performance in CO2 methanation compared to the non-promoted Ni/SBA-16 catalyst. The best catalytic activity was found for the catalyst promoted with 10 wt% Y. The improved performance of such catalysts was attributed to the increase of reducibility of nickel species, the increase in surface oxygen species, and the abundance of moderate basic sites caused by Y promotion. Furthermore, the CO2 reaction rate and turnover frequency of CO2 were well correlated with the number of moderate basic sites. Finally, all the tested catalysts are highly stable during the 8 h time-on-stream catalytic test.

Kinetic Study on CO-Selective Methanation over Nickel-Based Catalysts for Deep Removal of CO from Hydrogen-Rich Reformate

The CO-selective methanation process is considered as a promising CO removal process for compact fuel processors producing hydrogen, since the process selectively converts the trace of CO in the hydrogen-rich gas into methane without additional reactants. Two different types of efficient nickel-based catalysts, showing high activity and selectivity to the CO methanation reaction, were developed in our previous works; therefore, the kinetic models of the reactions over these nickel-based catalysts have been investigated adopting the mechanistic kinetic models based on the Langmuir chemisorption theory. In the methanation process, the product species can react with the reactant and also affect the adsorption/desorption of the molecules at the active sites. Thus, the kinetic parameter study should be carried out by global optimization handling all the rate equations for the plausible reactions at once. To estimate the kinetic parameters, an effective optimization algorithm combining both heuristic and deterministic methods is used due to the large solution space and the nonlinearity of the objective function. As a result, 14 kinetic parameters for each catalyst have been determined and the parameter sets for the catalysts have been compared to understand the catalytic characteristics.

Deep Understanding into the Effect of Fe on CO2 Methanation: A Support-Dependent Phenomenon

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 catalysts. In this research, CeO2 and Al2O3-supported Ni-based catalysts were prepared and evaluated for the CO2 methanation reaction. Interestingly, it was found that the addition of Fe into the CeO2-supported Ni catalyst lowered the CO2 methanation performance, while it greatly enhanced the performance of the Al2O3-supported Ni catalyst. A variety of factors over Fe-modified catalysts were explored, in which surface basicity along with oxygen vacancies could contribute to the adjustment of the CO2 methanation performance.

Solution plasma-assisted preparation of highly dispersed NiMnAl-LDO catalyst to enhance low-temperature activity of CO2 methanation

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.

Promoted Ni–Co–Al2O3 nanostructured catalysts for CO2 methanation

15 wt.%Ni-12.5 wt.%Co–Al2O3 catalysts promoted with Fe, Mn, Cu, Zr, La, Ce, and Ba were prepared by a novel solid-state synthesis method and employed in CO2 methanation reaction. BET, XRD, EDS, SEM, TPR, TGA, and FTIR analyses were conducted to identify the chemicophysical characteristics of the prepared samples. The addition of Fe, Mn, La, Ce, and Ba was effective to improve the catalytic performance of the 15 wt%Ni-12.5 wt%Co–Al2O3 due to the higher CO2 adsorption capacity of the promoted catalysts. Among the studied promoters, the Fe-promoted catalyst possessed the highest catalytic activity (XCO2 = 61.2% and SCH4 = 98.87% at 300 °C). Also, the effect of calcination temperature, feed composition, and GHSV on the performance of the 15 wt%Ni-12.5 wt%Co-5wt%Fe–Al2O3 catalyst in CO2 methanation reaction was assessed. The outcomes confirmed that the 15 wt%Ni-12.5 wt%Co-5wt%Fe–Al2O3 catalyst with the BET area of 122.4 m2/g and the highest pore volume and largest pore diameter had the highest catalytic activity. Also, the catalytic performance in the methanation of carbon monoxide was studied, and 100% conversion of carbon monoxide was observed at 250 °C.

K-Promoted Ni-Based Catalysts for Gas-Phase CO2 Conversion: Catalysts Design and Process Modelling Validation

The exponential growth of greenhouse gas emissions and their associated climate change problems have motivated the development of strategies to reduce CO2 levels via CO2 capture and conversion. Reverse water gas shift (RWGS) reaction has been targeted as a promising pathway to convert CO2 into syngas which is the primary reactive in several reactions to obtain high-value chemicals. Among the different catalysts reported for RWGS, the nickel-based catalyst has been proposed as an alternative to the expensive noble metal catalyst. However, Ni-based catalysts tend to be less active in RWGS reaction conditions due to preference to CO2 methanation reaction and to the sintering and coke formation. Due to this, the aim of this work is to study the effect of the potassium (K) in Ni/CeO2 catalyst seeking the optimal catalyst for low-temperature RWGS reaction. We synthesised Ni-based catalyst with different amounts of K:Ni ratio (0.5:10, 1:10, and 2:10) and fully characterised using different physicochemical techniques where was observed the modification on the surface characteristics as a function of the amount of K. Furthermore, it was observed an improvement in the CO selectivity at a lower temperature as a result of the K-Ni-support interactions but also a decrease on the CO2 conversion. The 1K catalyst presented the best compromise between CO2 conversion, suppression of CO2 methanation and enhancing CO selectivity. Finally, the experimental results were contrasted with the trends obtained from the thermodynamics process modelling observing that the result follows in good agreement with the modelling trends giving evidence of the promising behaviour of the designed catalysts in CO2 high-scale units.

Assessing the impact of textural properties in Ni–Fe catalysts for CO2 methanation performance

In heterogeneous catalysis, the benefits of employing adequate textural properties on the catalytic performances are usually stated. Nevertheless, the quantification of the extent of improvement is not an easy task since variations on the catalysts' specific areas and pore structures might involve modifications on a number of other surface catalytic features. This study establishes the impact of the catalyst textural properties on the CO2 methanation performance by investigating bimetallic Ni–Fe catalysts supported over carbon supports with different textural properties regarding surface area and pore structure. The comparable metal loading and dispersions attained for all systems enabled establishing forthright relationships between the catalyst textural properties and CO2 methanation rate. Once the influence of the external mass diffusions on the catalysts’ performance was experimentally discarded, the estimated Thiele modulus and internal effectiveness (φ and ηEff) values showed that the catalyst performance was majorly governed by the surface reaction rate whilst the pore size affected in no significant manner within the examined range (Dpore = 10.2 to 5.8 nm). Therefore, the rapport between the catalyst performance and surface area was quantified for the CO2 methanation reaction over Ni–Fe catalysts: increasing the surface area from 572 to 802 m2/g permit obtaining ca. 10% higher CO2 conversions.

Deactivation and Regeneration Method for Ni Catalysts by H2S Poisoning in CO2 Methanation Reaction

The carbon dioxide (CO2) methanation reaction is a process that produces methane (CH4) by reacting CO2 and H2. Many studies have been conducted on this process because it enables a reduction of greenhouse gases and the production of energy with carbon neutrality. Moreover, it also exhibits a higher efficiency at low temperatures due to its thermodynamic characteristics; thus, there have been many studies, particularly on the catalysts that are driven at low temperatures and have high durability. However, with regards to employing this process in actual industrial processes, studies on both toxic substances that can influence catalyst performance and regeneration are still insufficient. Therefore, in this paper, the activity of a Ni catalyst before and after hydrogen sulfide (H2S) exposure was compared and an in-depth analysis was conducted to reveal the activity performance through the regeneration treatment of the poisoned catalyst. This study observed the reaction activity changes when injecting H2S during the CO2 + H2 reaction to evaluate the toxic effect of H2S on the Ni-Ce-Zr catalyst, in which the results indicate that the reaction activity decreases rapidly at 220 °C. Next, this study also successfully conducted a regeneration of the Ni-Ce-Zr catalyst that was poisoned with H2S by applying H2 heat treatment. It is expected that the results of this study can be used as fundamental data in an alternative approach to performance recovery when a small amount of H2S is included in the reaction gas of industrial processes (landfill gas, fire extinguishing tank gas, etc.) that can be linked to CO2 methanation.

One-Pot Synthesis of Ni0.05Ce0.95O2−δ Catalysts with Nanocubes and Nanorods Morphology for CO2 Methanation Reaction and in Operando DRIFT Analysis of Intermediate Species

The valorization of CO2 via renewable energy sources allows one to obtain carbon-neutral fuels through its hydrogenation, like methane. In this study, Ni0.05Ce0.95O2−δ catalysts were prepared using a simple one-pot hydrothermal method yielding nanorod and nanocube particles to be used for the methanation reaction. Samples were characterized by XRD, BET, TEM, H2-TPR, and H2-TPD experiments. The catalytic activity tests revealed that the best performing catalyst was Ni0.05Ce0.95O2−δ, with nanorod morphology, which gave a CO2 conversion of 40% with a selectivity of CH4 as high as 93%, operating at 325 °C and a GHSV of 240,000 cm3 h−1 g−1. However, the lower activation energy was found for Ni0.05Ce0.95O2−δ catalysts with nanocube morphology. Furthermore, an in operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis was performed flowing CO2:H2 or CO:H2 mixture, showing that the main reaction pathway, for the CO2 methanation, is the direct hydrogenation of formate intermediate.

Alkali and Alkali-Earth Metals Incorporation to Ni/USY Catalysts for CO2 Methanation: The Effect of the Metal Nature

CO2 methanation is typically carried out using Ni-supported catalysts containing promoters such as alkali or alkali-earth metals to improve their properties. In this work, bimetallic Ni-based USY zeolite catalysts containing alkali (Li, K and Cs) and alkali-earth (Mg, Ca) metal compounds were prepared using the same conditions (15 wt% of metals; co-impregnation), characterized by N2 sorption, XRD, TGA, CO2 adsorption–desorption, DRS UV-Vis and H2-TPR, and finally applied in CO2 methanation reaction (86,100 mL h−1 g−1, PCO2 = 0.16 bar, H2:CO2 = 4:1). For each group, the effects of the second metal nature on the properties and performances were assessed. Alkali metals incorporation induced considerably low catalytic performances (CH4 yields < 26%), attributed to their negative impact on zeolite structure preservation. On the contrary, alkali-earth metal-containing catalysts exhibited lower structural damage. However, the formation of Ni-Mg mixed oxides in Ni-Mg/USY catalyst and CaCO3 during the reaction in Ni-Ca/USY sample could explain their performances, similar or lower than those obtained for Ni/USY catalyst. Among the studied metals, calcium was identified as the most interesting (CH4 yield of 65% at 415 °C), which was ascribed to the slight improvement of the Ni0 dispersion.

Effect of cobalt promotion on hydrotalcite-derived nickel catalyst for CO2 methanation

A series of cobalt-promoted Ni-Mg-Al hydrotalcite-derived catalysts were tested towards CO2 methanation reaction. The best among examined catalysts was the one with 1 wt% of cobalt in fresh hydrotalcite, obtaining 77% of CO2 conversion and 99% of CH4 selectivity at 300 °C. Above that temperature, the catalyst was working with-near-equilibrium parameters. It was also stable for up to 24 h on stream. Other cobalt-containing samples were likewise very active and selective during the time on stream. Due to the use of a low amount of cobalt (0.5–4 wt%) the Co-Ni alloy was not the subject of research – both materials formed probably solid solution of cobalt in the nickel matrix. Although the behavior of cobalt as a textural and electronic promoter was confirmed. Co was found to improve reducibility of nickel species, hydrogen uptake, and the acidic/basic properties by increasing the number of medium strength and strong basic sites. Tendency to sintering of nickel crystallites on cobalt-promoted catalysts was not confirmed in this study, however, with increased content of Co, bigger metal crystallites were formed under the reduction conditions.

Investigation on the Suitability of Engelhard Titanium Silicate as a Support for Ni-Catalysts in the Methanation Reaction

Methanation reaction of carbon dioxide is currently envisaged as a facile solution for the storage and transportation of low-grade energies, contributing at the same time to the mitigation of CO2 emissions. In this work, a nickel catalyst impregnated onto a new support, Engelhard Titanium Silicates (ETS), is proposed, and its catalytic performance was tested toward the CO2 methanation reaction. Two types of ETS material were investigated, ETS-4 and ETS-10, that differ from each other in the titanium content, with Si/Ti around 2 and 3% by weight, respectively. Catalysts, loaded with 5% of nickel, were tested in the CO2 methanation reaction in the temperature range of 300–500 °C and were characterized by XRD, SEM–EDX, N2 adsorption–desorption and H2-TPR. Results showed an interesting catalytic activity of the Ni/ETS catalysts. Particularly, the best catalytic performances are showed by Ni/ETS-10: 68% CO2 conversion and 98% CH4 selectivity at T = 400 °C. The comparison of catalytic performance of Ni/ETS-10 with those obtained by other Ni-zeolites catalysts confirms that Ni/ETS-10 catalyst is a promising one for the CO2 methanation reaction.

Fabrication of surface oxygen vacancies on NiMnAl-LDO catalyst by high-shear mixer-assisted preparation for low-temperature CO2 methanation

Low-temperature performance of non-noble metal Ni-based catalysts in CO2 methanation still faces great challenges. A series of NiMnAl-LDO (layered double oxides) catalysts with different processing conditions were prepared using the high-shear mixer-assisted method. The FH-C (80 °C) catalyst exhibited high activity in low-temperature CO2 methanation, and CO2 conversion and CH4 selectivity reached 85% and 97% at 200 °C. Characterization results show that the strong shear force of the high-shear mixer can improve the dispersion of the catalyst and reduce the particle size of the catalyst. The high-shear mixer treatment increases the CO2 chemisorption and the number of strongly basic sites on the catalyst. The main reason for the low-temperature activity of the catalyst is that the high-shear mixer increases the number of oxygen vacancies in the catalyst. In situ infrared probes into the surface species and intermediate products of the catalyst, confirming that formate is an intermediate product of the CO2 methanation reaction. Density functional theory calculations demonstrated that increasing the content of oxygen vacancies is beneficial for increasing the CO2 adsorption capacity of the catalyst and reducing the reaction energy barrier of CO2 → COOH*.

Ni Nanoparticles on Reducible Metal Oxides (Sm2O3, CeO2, ZnO) as Catalysts for CO2 Methanation

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).

Effect of Ru loading on Ru/CeO2 catalysts for CO2 methanation

The conversion of CO2 towards added valuable products is considered as a potential alternative to achieve the increase of the petrochemical industry while reducing the CO2 emissions. In the present work, the effect of Ru loading on CeO2 supports has been studied for the CO2 methanation reaction, and catalysts with different Ru loading in the 1–5 wt. % range have been prepared, characterized, and tested. The optimum Ru loading has been found to be 2.5 wt. %. Ruthenium cations are reduced at the lowest temperature for this optimum loading according to H2-TPR experiments (even at room temperature), and the highest proportion of ruthenium cations with strong interaction with ceria is achieved, as deduced from XPS. XRD characterization suggests partial insertion of ruthenium cations into the ceria lattice.In situ DRIFTS experiments evidenced that the balance between formation upon CO2 chemisorption and further hydrogenation of surface carbon intermediates is optimum for 2.5 wt. % Ru/CeO2. For low metal contents, the CO2 chemisorption is limited and no relevant, while as the metal content is increased, the hydrogenation of carbon species is less favourable. The 2.5 wt.% Ru/CeO2 catalyst comprises a balance between surface-carbon groups formation and further hydrogenation.

CO2 Hydrogenation to Synthetic Natural Gas over Ni, Fe and Co–Based CeO2–Cr2O3

CO2 methanation was studied over monometallic catalyst, i.e., Ni, Fe and Co; on CeO2-Cr2O3 support. The catalysts were prepared using one-pot hydrolysis of mixed metal nitrates and ammonium carbonate. Physicochemical properties of the pre- and post-exposure catalysts were characterized by X-Ray Powder Diffraction (XRD), Hydrogen Temperature Programmed Reduction (H2-TPR), and Field Emission Scanning Electron Microscope (FE-SEM). The screening of three dopants over CeO2-Cr2O3 for CO2 methanation was conducted in a milli-packed bed reactor. Ni-based catalyst was proven to be the most effective catalyst among all. Thus, a group of NiO/CeO2-Cr2O3 catalysts with Ni loading was investigated further. 40 % NiO/CeO2-Cr2O3 exhibited the highest CO2 conversion of 97.67% and CH4 selectivity of 100% at 290 °C. The catalytic stability of NiO/CeO2-Cr2O3 was tested towards the CO2 methanation reaction over 50 h of time-on-stream experiment, showing a good stability in term of catalytic activity.

Effect of micropores on the structure and CO2methanation performance of supported Ni/SiO2catalyst

AbstractTwo types of SiO2with different microporosities were evaluated as supports for the Ni/SiO2catalysts. The CO2methanation performance of the catalysts was evaluated, and the structure‐activity relationship was elucidated with thorough characterizations. For the Ni/SiO2catalyst with plenty of micropores, both ultrasmall Ni nanoclusters and larger Ni nanoparticles are present. In contrast, the one with fewer micropores only contains large Ni nanoparticles. During the CO2methanation reaction, CO2can be activated to CO on small Ni nanoclusters and further converted to CH4on larger Ni nanoparticles. Such a tandem catalysis behavior greatly improves the CO2methanation activity. The CH4yield reaches 33.5 μmol·g–1·s–1at 450 °C under 0.1 MPa with a feed H2/CO2mol ratio of 4:1 and a space velocity of 30 L·h–1·g–1. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.