Activity For CO2 Methanation Research Articles

Thermodynamic and experimental explorations of CO2 methanation over highly active metal-free fibrous silica-beta zeolite (FS@SiO2-BEA) of innovative morphology

CO2 methanation is a novel way for climate change mitigation by converting CO2 into substitute natural gas. In this study, a highly active fibrous silica-beta zeolite (FS@SiO2-BEA) catalyst was prepared for CO2 methanation by a microemulsion process, and examined by N2 adsorption–desorption, field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), and electron spin resonance (ESR) spectroscopy techniques. It was found that the FS@SiO2-BEA catalyst possessed a fibrous silica morphology, leading to high surface area (609 m2/g), oxygen vacancies, and basicity. A thermodynamic study was also carried out using Gibbs free energy minimization method, and it was found that low temperatures (25–350 °C) and high H2: CO2 ≥ 4 ratios have enhanced the CO2 methanation activity. The prepared FS@SiO2-BEA catalyst exhibited high CO2 conversion (65%), and CH4 selectivity (61%) with a space–time yield of 3.30 g gcat−1h−1. The obtained experimental results highly followed the thermodynamic calculations.

Synthesis of modified TiO2-based catalysts for the photocatalytic production of solar fuels from synthesis gas

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.

Effect of Fe and Co promoters on CO methanation activity of nickel catalyst prepared by impregnation – co-precipitation method

Abstract Ni based catalysts supported on γ-Al2O3 that was unpromoted (Ni/γAl2O3) or promoted (Ni–Fe/γAl2O3, Ni–Co/γAl2O3, and Ni–Fe–Co/γAl2O3) were prepared using by the impregnation – co-precipitation method. Their catalytic performances for CO methanation were studied at 3 atm with a weight hourly space velocity (WHSV) of 3000 ml/g/h of syngas with a molar ratio of H2/CO = 3 and in the temperature range between 130 and 350 °C. All promoters could improve nickel distribution, and decreased its particle sizes. It was found that the Ni–Co/γAl2O3 catalyst showed the highest catalytic performance for CO methanation in a low temperature range (<250 °C). The temperatures for the 20% CO conversion over Ni–Co/γAl2O3, Ni–Fe/γAl2O3, Ni–Fe–Co/γAl2O3 and Ni/γAl2O3 catalysts were 205, 253, 263 and 270 °C, respectively. The improved catalyst distribution by the addition of cobalt promoter caused the formation of β type nickel species which had an appropriate interacting strength with alumina support in the Ni–Co/γAl2O3. Though an addition of iron promoter improved catalyst distribution, the methane selectivity was lowered due to acceleration of both CO methanation and WGS reaction with the Ni–Fe/γAl2O3. Moreover, it was found that there was no synergetic effect from the binary Fe–Co promotors in the Ni–Fe–Co/γAl2O3 on catalytic activity for CO methanation.

La-enhanced Ni nanoparticles highly dispersed on SiC for low-temperature CO methanation performance

For better performances of Ni-based catalysts at low temperatures, Ni/SiC catalyst doped with a little amount of additive La was successfully prepared. The catalytic CO methanation activity tests showed that 3%La–Ni/SiC catalyst was excellent at a low reaction temperature (95.9% CO conversion and 85.1% CH4 selectivity at 250 °C) with a superior stability compared with Ni/SiC (3.4% CO conversion and 0% CH4 selectivity at 250 °C). This can be attributed to that the addition of La can markedly improve the dispersibility of active metal Ni and reduce the particle sizes of Ni nanoparticles or clusters, and can also regulate the interaction between active components and supports. Moreover, the high thermal conductivity and thermal stability could avoid the generation of hot spots in the catalyst bed. These results will promote the development of highly active Ni-based catalysts for the low-temperature methanation reaction.

A Study on CO2 Methanation and Steam Methane Reforming over Commercial Ni/Calcium Aluminate Catalysts

Three Ni-based natural gas steam reforming catalysts, i.e., commercial JM25-4Q and JM57-4Q, and a laboratory-made catalyst (26% Ni on a 5% SiO2–95% Al2O3), are tested in a laboratory reactor, under carbon dioxide methanation and methane steam reforming operating conditions. The laboratory catalyst is more active in both CO2 methanation (equilibrium is reached at 623 K with 100% selectivity) and methane steam reforming (92% hydrogen yield at 890 K) than the two commercial catalysts, likely due to its higher nickel loading. In any case, commercial steam reforming catalysts also show interesting activity in CO2 methanation, reduced by K-doping. The interpretation of the experimental results is supported by a one-dimensional (1D) pseudo-homogeneous packed-bed reactor model, embedding the Xu and Froment local kinetics, with appropriate kinetic parameters for each catalyst. In particular, the H2O adsorption coefficient adopted for the commercial catalysts is about two orders of magnitude higher than for the laboratory-made catalyst, and this is in line with the expectations, considering that the commercial catalysts have Ca and K added, which may promote water adsorption.

MOF-derived ceria-zirconia supported Co3O4 catalysts with enhanced activity in CO2 methanation

Recent research in catalyst development for CO2 methanation has been focussing on the design of nanostructures with high porosity and better redox properties. Herein, nanostructured Ce0.8Zr0.2O2 mixed oxide support was prepared by a metal organic framework (MOF)-template approach and its properties were well compared with a similar catalyst prepared by a conventional coprecipitation (CP) method. The MOF-template approach resulted in the production of a nanoporous Ce0.8Zr0.2O2 support with improved redox properties compared to the coprecipitated Ce0.8Zr0.2O2. The prepared support was then decorated with Co3O4 nanoparticles and tested in CO2 methanation reaction. At 320 °C, 1.5 MPa and GHSV = 15,000 mL g˗1 h˗1, the Co/Ce0.8Zr0.2O2 catalyst prepared by MOF-template method achieved far better CO2 conversion (81.2%) and improved CH4 selectivity (99%) than the catalyst prepared by CP method (48.7% CO2 conversion and 97% CH4 selectivity). The long-time presence of the MOF-derived Co/Ce0.8Zr0.2O2 catalyst on the stream proved its resistance towards sintering, which may be ascribed to the fine dispersion of Co3O4 nanoparticles as well as their excellent integration in the network of nanoporous Ce0.8Zr0.2O2.

Surface Iron Species in Palladium-Iron Intermetallic Nanocrystals that Promote and Stabilize CO2 Methanation.

It is of pivotal importance to develop efficient catalysts and investigate the intrinsic mechanism for CO2 methanation. Now, it is reported that PdFe intermetallic nanocrystals afforded high activity and stability for CO2 methanation. The mass activity of fct-PdFe nanocrystals reached 5.3 mmol g-1 h-1 , under 1 bar (CO2 :H2 =1:4) at 180 °C, being 6.6, 1.6, 3.3, and 5.3 times as high as that of fcc-PdFe nanocrystals, Ru/C, Ni/C, and Pd/C, respectively. After 20 rounds of successive reaction, 98 % of the original activity was retained for PdFe intermetallic nanocrystals. Further mechanistic studies revealed that PdFe intermetallic nanocrystals enabled the maintenance of metallic Fe species via a reversible oxidation-reduction process in CO2 methanation. The metallic Fe in PdFe intermetallic nanocrystals induced the direct conversion of CO2 into CO* as the intermediate, contributing to the enhanced activity.

Surface Iron Species in Palladium–Iron Intermetallic Nanocrystals that Promote and Stabilize CO2 Methanation

AbstractIt is of pivotal importance to develop efficient catalysts and investigate the intrinsic mechanism for CO2 methanation. Now, it is reported that PdFe intermetallic nanocrystals afforded high activity and stability for CO2 methanation. The mass activity of fct‐PdFe nanocrystals reached 5.3 mmol g−1 h−1, under 1 bar (CO2:H2=1:4) at 180 °C, being 6.6, 1.6, 3.3, and 5.3 times as high as that of fcc‐PdFe nanocrystals, Ru/C, Ni/C, and Pd/C, respectively. After 20 rounds of successive reaction, 98 % of the original activity was retained for PdFe intermetallic nanocrystals. Further mechanistic studies revealed that PdFe intermetallic nanocrystals enabled the maintenance of metallic Fe species via a reversible oxidation–reduction process in CO2 methanation. The metallic Fe in PdFe intermetallic nanocrystals induced the direct conversion of CO2 into CO* as the intermediate, contributing to the enhanced activity.

Enhancing CO2 Hydrogenation to Methane by Ni-Based Catalyst with V Species Using 3D-mesoporous KIT-6 as Support

Using renewable H2 for CO2 hydrogenation to methane not only achieves CO2 utilization, but also mitigates the greenhouse effect. In this work, several Ni-based catalysts with V species using 3D-mesoporous KIT-6 (Korea Advanced Institute of Science and Technology, KIT) as support were prepared at different contents of NiO and V2O5. Small Ni nanoparticles with high dispersibility on 20Ni-0.5V/KIT-6 were identified by X-ray diffraction (XRD), TEM and hydrogen temperature-programmed desorption (H2-TPD) analysis, which promoted the production of more Ni active sites for enhancing catalytic activity for CO2 methanation. Moreover, TEM and hydrogen temperature-programmed reduction (H2-TPR) characterizations confirmed that a proper amount of Ni and V species was favorable to preserve the 3D-mesoporous structure and strengthen the interaction between active Ni and KIT-6. The synergistic effect between Ni and V could strengthen surface basicity to elevate the ability of CO2 activity on the 20Ni-0.5V/KIT-6. In addition, a strong interaction with the 3D-mesoporous structure allowed active Ni to be firmly anchored onto the catalyst surface, which was accountable for improving catalytic activity and stability. These results revealed that 20Ni-0.5V/KIT-6 was a catalyst with superior catalytic activity and stability, which was considered as a promising candidate for CO2 hydrogenation to methane.

Effect of Support and Chelating Ligand on the Synthesis of Ni Catalysts with High Activity and Stability for CO2 Methanation

Carbon dioxide methanation was carried out over Ni-based catalysts on different supports and chelating ligands in microreactors. To investigate the influence of chelating ligands and supports, the Ni catalysts were prepared using different support such as CeO2, Al2O3, SiO2, and SBA-15 by a citric acid (CA)-assisted impregnation method. The properties of the developed catalysts were studied by X-ray diffraction (XRD), Transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS) measurement, and the results show that the addition of CA in the impregnation solution improved the dispersion, refines the particle size, and enhanced the interaction of nickel species. The catalytic performance of the developed Ni catalysts were evaluated by CO2 methanation in microreactors in the temperature range of 275 °C–375 °C under 12.5 bar pressure. All the catalysts exhibit high CO2 conversion and extremely high selectivity to methane. However, the catalysts prepared via CA-assisted method exhibited excellent activity and stability, compared with Ni catalysts prepared by a conventional impregnation method, which could be attributed to highly dispersed nickel particles with strong metal–support interaction. The activity of CO2 methanation followed the order of Ni/CeO2-CA > Ni/SBA-15-CA > Ni/Al2O3-CA > Ni/SiO2-CA > Ni/CeO2. The Ni/CeO2 catalysts have also been prepared using different chelating ligands such as ethylene glycol (EG), sucrose (S), oxalic acid (OA) and ethylene diamine tetra acidic acid (EDTA). Among the tested catalysts prepared with different support and chelating ligands, the Ni/CeO2 catalyst prepared via CA-assisted method gave superior catalytic performance and it could attain 98.6% of CO2 conversion and 99.7% methane selectivity at 325 °C. The partial reduction of the CeO2 support generates more surface oxygen vacancies and results in a high CO2 conversion and methane selectivity compared with other catalysts. The addition of CA as promoter favored the synergistic effect of Ni and support, which led to high dispersion, controls the size, and stabilizes the Ni nanoparticles. Furthermore, the Ni/CeO2-CA catalyst yields high CO2 conversion in a time-on-stream study due to the ability of preventing the carbon deposition and sintering of Ni particles under the applied reaction conditions. However, the Ni/Al2O3-CA and Ni/SBA-15-CA catalysts showed stable performance for 100 h of time on stream.

Influence of Nickel Loading on Reduced Graphene Oxide-Based Nickel Catalysts for the Hydrogenation of Carbon Dioxide to Methane

In this study, a series of novel nickel catalysts supported on reduced graphene oxide nanosheets (Ni/rGO) with Ni loadings of 10, 15 and 20 wt% were successfully synthesized via the incipient wetness impregnation method. The physicochemical properties of the catalysts and rGO support were thoroughly characterized by thermogravimetric analyser, X-ray diffraction, fourier-transform infrared spectroscopy, Raman spectroscopy, N2 adsorption-desorption, temperature programmed reduction, temperature programmed CO2 desorption and field emission scanning electron microscopy with energy dispersive X-ray spectroscopy. The properties of the catalysts are correlated to its catalytic activity for CO2 methanation which were investigated using three-phase slurry reactor at low temperature and pressure of 240 °C and 10 bar, respectively. Among the three catalysts of different Ni loading, Ni15/rGO shows the highest activity of 51% conversion of CO2 with total selectivity towards CH4. N2-physisorption and CO2-TPD analysis suggest that high catalytic performance of Ni15/rGO is attributed to the high surface area, strong basic sites and special support effect of rGO in anchoring the active metal.

COx co-methanation over coal combustion fly ash supported Ni-Re bimetallic catalyst: Transformation from hazardous to high value-added products

The hazardous industrial waste, coal combustion fly ash (CCFA), was creatively applied as Ni-Re bimetallic catalyst support. The expected catalyst was facilely prepared by co-impregnation method and further tested for COx co-methanation in a continuous fixed-bed reactor. The physico-chemical properties of the catalyst were examined by a series of techniques including XRF, ICP, XRD, N2 isothermal adsorption, H2-TPR, SEM and TEM. The results showed that compared to non-promoted monometallic Ni catalyst, the addition of Re promoter forming Ni-Re bimetallic catalyst was able to facilitate NiO reduction and increase Ni dispersion as well as inhibit carbon deposition and Ni sintering during reaction. The performance tests revealed that Ni15Re1.0 presented superior COx co-methanation activity over Ni15Re0, Ni15Re0.5 and Ni15Re1.5 due to its better anti-coking and anti-sintering ability. Based on in-situ DRIFTS analysis, a possible cycle reaction mechanism of COx co-methanation was reasonably proposed in the end. The reaction pathway for CO and CO2 methanation differed from each other, where CO was linearly adsorbed on Ni metals followed by stepwise hydrogenation while CO2 was first immobilized by the surface hydroxyl group and then gradually reacted with H2 to form CH4.

Low-temperature Conversion of Carbon Dioxide to Methane in an Electric Field

CO2 methanation was conducted at low temperatures with an electric field. Results show that 5 wt %Ru/CeO2 catalyst exhibited high and stable catalytic activity for CO2 methanation with the electric...

A viable system for carbon dioxide (CO2) methanation over fibrous silica ZSM-5 for substitute natural gas (SNG)

Catalytic CO2 methanation offers an attractive and sustainable way for the production of substituted natural gas (SNG), which may be used as a clean alternative energy source than fossil fuels. A metal-free fibrous silica ZSM-5 catalyst (FS@ZSM-5) was synthesized via the microemulsion technique to conduct catalytic CO2 methanation. The FESEM, BET, and FTIR characterization techniques were used to investigate the surface morphology, pore structure of the catalysts. It was noticed that the commercialized ZSM-5 showed 37% CH4 selectivity with a rate of methane formation 0.067 mmol m−2s−1. While FS@ZSM-5 exhibited high CH4 selectivity of 66 % with rate of methane formation 0.108 mmol m−2s−1 using same conditions (T = 500 °C and GHSV = 36,000 mL h−1 g−1). Therefore, the FS@ZSM-5 was proved an efficient and active catalyst for CO2 methanation activity.

Favored hydrogenation of linear carbon monoxide over cobalt loaded on fibrous silica KCC-1

In this study, the conversion of CO into CH4 was investigated utilizing a series of cobalt loaded on fibrous silica (KCC-1) catalysts (Co loading of 5–30 wt%), that were synthesized via microemulsion and impregnation techniques. FESEM-EDX and N2 physisorption demonstrated that the KCC-1 possessed a spherical structure with fibrous silica dendrimeric morphology with a superior surface area of 861 m2g-1. A significant decreased in the catalyst surface area was noticed upon the addition of Co, suggesting a possible occurrence of KCC-1 pore blockage. Inversely, the number of basic sites on KCC-1 was enhanced after the incorporation of Co, as observed by pyrrole adsorbed FTIR. At 523 K, bare KCC-1 exhibited a very low activity for CO methanation due to low basicity and the absence of surface active sites. The 20Co/KCC-1 demonstrated the best catalytic performance with 72.7% yield of CH4 and 6.8% of CO2. These results were plausibly attributed to the high intrinsic number of basic sites and high dispersion of Co on KCC-1 support. A detailed in-situ FTIR spectroscopy study revealed that both types of associative and dissociative mechanism pathways significantly contributed to the high catalytic methanation activity. In addition to the dissociative mechanism, the linear CO species adsorbed on the Co metal by associative mechanism was also further hydrogenated to obtain the final CH4 products.

Influences of Calcination Atmosphere on Nickel Catalyst Supported on Mesoporous Graphitic Carbon Nitride Thin Sheets for CO Methanation.

Nickel (Ni) catalysts supported on mesoporous graphitic carbon nitride (mpg-C3N4) were synthesized through simple impregnation method with air and nitrogen calcination atmosphere for CO methanation. The effects of pretreatment gas on catalyst structure, surface characteristics, and Ni species reducibility were investigated. Under air-calcination condition, the increase in specific surface area of the catalyst can be ascribed to the creation of mesopores and exfoliation of bulk mpg-C3N4 to form thin sheets. However, excessive Ni content on the catalyst accelerated the decomposition of the mpg-C3N4 support during calcination. The catalysts calcined in nitrogen showed lower surface area and fewer number of pores compared to air-treatment. The Ni/mpg-C3N4 catalyst calcined in air with Ni loading 10% exhibited enhanced medium-temperature activity for CO methanation with 79.7% CO conversion and 73.9% CH4 selectivity. This finding can be explained by the formation of mpg-C3N4 thin sheets, which increased the number of catalyst active sites. The CO methanation performance of Ni/mpg-C3N4 catalysts calcined in air was superior to those calcined in nitrogen. Interestingly, CO2 formed by water-gas shift reaction at 320 °C also contributed to the overall methane formation through CO2 methanation. Therefore, mpg-C3N4 thin sheets can be an interesting support for nickel catalyst for COx methanation.

Cockscomb-like fibrous silica beta zeolite (FSBEA) as a new engineered catalyst for enhanced CO methanation

This study focuses on the synthesis of cockscomb-like fibrous silica beta zeolite (FSBEA) and its application in CO methanation to produce substituted natural gas (SNG). FSBEA was synthesized by microemulsion technique using commercial beta zeolite-seeds and characterized by FESEM, XRD, N2 physisorption and FTIR spectroscopy. The results showed that the FSBEA had a unique cockscomb-like morphology with particle size 400-800 nm, enhanced interparticle porosity and high BET surface area of 532 m2/g, which offers more adsorption sites for the CO and H2 molecules to enhance CO methanation activity. Catalytic performance results revealed that FSBEA demonstrated higher CO conversion (71%), selectivity (64%), the yield of CH4 (46%) and the rate of CH4 formation (0.0375 μmol-CH4/m2s) than commercial based BEA. Besides, FSBEA expressed high thermal stability up to 45 h during CO methanation at 450 °C. Therefore, this study offers an attractive and sustainable route for SNG over FSBEA that may be used as a clean and alternate energy source for fossil fuels.

Ru nanoparticles supported on amorphous ZrO2for CO2methanation

The influence of support materials and preparation methods on CO2methanation activity was investigated using Ru nanoparticles supported on amorphous ZrO2(am-ZrO2), crystalline ZrO2(cr-ZrO2), and SiO2.

Preparation of highly dispersed supported Ni-Based catalysts and their catalytic performance in low temperature for CO methanation

The use of non-noble nickel-based catalysts for low temperature CO methanation has been a challenge in recent years. Herein, MgAl layered double oxides sample with high dispersion synthesized by a facile N-(2-Hydroxyethyl) ethylenediaminetriacetic acid assisted wetness impregnation approach, demonstrates much superior catalytic activity and exceptional stability for CO methanation in comparison with the classical Ni/MgAl-LDO catalyst prepared by the ordinary wetness impregnation method. HRTEM results showed that N-(2-Hydroxyethyl)ethylenediaminetriacetic acid played a positive role in the dispersion of Ni, as well as Ni-support interaction. Well-dispersed Ni particles with a size of about 5 nm were formed in the presence of N-(2-Hydroxyethyl) ethylenediaminetriacetic acid. Compared to the Ni/MgAl-LDO prepared by conventional impregnation method, the NH-Ni/MgAl-LDO exhibited superior catalytic performance, especially excellent thermal stability. The NH-Ni30/MgAl-LDO catalyst was found to keep a 70 % CO conversion even at 160 °C which demonstrates its good low temperature performance. From the in situ FTIR observations, this good performance at low temperatures may be linked to the delocalization of electrons around CO caused by surface hydroxyl groups.

Low Temperature Methanation of CO2 on High Ni Content Ni-Ce-ZrOδ Catalysts Prepared via One-Pot Hydrothermal Synthesis

Ni-Ce-Zr-Oδ catalysts were prepared via one-pot hydrothermal synthesis. It was found that Ni can be partially incorporated into the Ce-Zr lattice, increasing surface oxygen species. The catalysts possess high surface areas even at high Ni loadings. The catalyst with Ni content of 71.5 wt.% is able to activate CO2 methanation even at a low temperature (200 °C). Its CO2 conversion and methane selectivity were reported at 80% and 100%, respectively. The catalyst was stable for 48 h during the course of CO2 methanation at 300 °C. Catalysts with the addition of medium basic sites were found to have better catalytic activity for CO2 methanation.