Performance For CO Methanation Research Articles

Practical Application Study of Highly Active CO2 Methanation Catalysts Prepared Using the Polygonal Barrel-Sputtering Method: Immobilization of Catalyst Particles

This study investigated immobilization (without binders and high-temperature heating) of highly active CO2 methanation catalyst particles, prepared by the polygonal barrel-sputtering method, onto porous Al2O3 plates. The catalyst particles were fixed uniformly and firmly on the plates and retained their high CO2 methanation performance.

Methanation of CO2 and CO by (Ni,Mg,Al)-Hydrotalcite-Derived and Related Catalysts with Varied Magnesium and Aluminum Oxide Contents

In the present study, the influence of the composition of Lewis basic (Mg,Al)Ox mixed oxide supports on CO2 and CO methanation performance of (Ni,Mg,Al)-hydrotalcite-derived catalysts is investigated. The hydrotalcite-derived and related precursors are synthesized by pH-controlled coprecipitation, calcination, and subsequent reduction. The catalysts with different supports prove suitability for CO2 and for CO methanation but display significant differences in respect to the temperature sensitivity of the reactions. The influence of the systematically varied support composition was studied by kinetic measurements, X-ray photoelectron spectroscopy (XPS), and in situ diffuse reflectance infrared Fourier transform (DRIFTS). Performance differences between CO2 and CO methanation were investigated for three different catalyst compositions. Different adsorption patterns in the DRIFTS measurements for these catalysts allow us to assign the increase in performance in the presence of magnesium oxide primarily to the enhancement of CO2 adsorption on the catalyst support. Temperature-dependent DRIFTS measurements display a correlation between the ratio of formate to carbonyl species on the catalyst surface and the activity of the catalyst in the case of magnesium-containing catalysts. The result suggests the role of CO as a key intermediate for CO2 methanation for magnesium-containing nickel hydrotalcite-derived catalysts. XPS measurements demonstrate that the magnesium content significantly affects the reducibility in the precursor material to generate the active component.

Effect of Ni particle size on the production of renewable methane from CO2 over Ni/CeO2 catalyst

Production of ‘renewable Methane’ has attracted renewed research interest as a fundamental probe reaction and process for CO2 utilization through potential use in C1 fuel production and even for future space exploration technologies. CO2 methanation is a structure sensitive reaction on Ni/CeO2 catalysts. To precisely elucidate the size effect of the Ni metal center on the CO2 methanation performance, we prepared 2%Ni/CeO2 catalysts with pre-synthesized uniform Ni particles (2, 4 and 8 nm) on a high surface area CeO2 support. Transmission electron microscopy (TEM) and ambient pressure X-ray photo spectroscopy (AP-XPS) characterization have confirmed that the catalyst structure and chemical state was uniform and stable under reaction conditions. The 8 nm sized catalyst showed superior methanation selectivity over the 4 and 2 nm counterparts, and the methanation activity in term of TOF is 10 times and 70 times higher than for the 4 and 2 nm counterparts, respectively. The DRIFTS studies revealed that the larger Ni (8 nm particles) over CeO2 efficiently facilitated the hydrogenation of the surface formate intermediates, which is proposed as the rate determining step accounting for the excellent CO2 methanation performance.

Formation of perovskite-type LaNiO3 on La-Ni/Al2O3-ZrO2 catalysts and their performance for CO methanation

The carbon deposition and sintering of Ni-based catalysts, used in CO methanation, are the main problems to be solved. In this paper, supported LaNiO3/Al2O3-ZrO2 catalyst was prepared by neutralization hydrolysis-citric acid complexation method. The effects of La-Ni loading and calcination temperature of support on the structure and catalytic activity of the catalyst were investigated. The structural evolution of catalyst precursor before and after reduction was studied via XRD, H2-TPR, BET, XPS, TEM and other characterization methods. The results showed that the catalyst supported by homogeneous Al-Zr solid solution was beneficial to form the active component with LaNiO3 structure, and the Ni0 derived from LaNiO3 was the key factor for keeping the activity at high temperature. The La-Ni loading affected the formation of LaNiO3 and the reduction state of Ni. Among the catalysts studied, 30% of the La-Ni loading was more favorable for the formation of perovskite LaNiO3. The Ni0 and La2O3 reduced from LaNiO3 were highly dispersed on the surface of the support, and the Ni0 nanoparticles were anchored by the support and La2O3, which inhibited the migration and aggregation of Ni0 particles at high temperature and thus led to high thermal stability.

Ni/SiO2-Al2O3 catalysts for CO2 methanation: Effect of La2O3 addition

Ni-based catalysts, 13.5 Ni wt.%, with enhanced thermal stability and catalytic performance for CO2 methanation have been synthesized with different La2O3 loadings. Catalysts have been extensively characterised by: XRD, IR, H2-TPR, IPA-TPD, UV–vis-NIR, FE-SEM and tested in CO2 methanation. SiO2 addition to Al2O3 support decreases the activity for CO2 methanation, while lanthanum acts as suitable promoter by strongly increasing catalytic performances. Silica presence successfully inhibits the formation of crystalline perovskites phases, stabilizes support morphology, and allows the introduction of high La2O3 loadings, allowing a better control of acid-base properties. 37 % wt. La2O3 addition gives rise to even higher performances than those previously observed, i.e. 83 % CH4 yield at 573 K. Reaction orders for CO2 and H2 have been determined; La- addition is confirmed to be responsible for a reduction in the CO2 reaction order, suggesting a stronger CO2 adsorption and the possible role of these species as a reactant reservoirs.

Solid-state synthesis method for the preparation of cobalt doped Ni–Al2O3 mesoporous catalysts for CO2 methanation

In this study, a simple solid-state synthesis method was employed for the preparation of the Ni–Co–Al2O3 catalysts with various Co loadings, and the prepared catalysts were used in CO2 methanation reaction. The results demonstrated that the incorporation of cobalt in nickel-based catalysts enhanced the activity of the catalyst. The results showed that the 15 wt%Ni-12.5 wt%Co–Al2O3 sample with a specific surface area of 129.96 m2/g possessed the highest catalytic performance in CO2 methanation (76.2% CO2 conversion and 96.39% CH4 selectivity at 400 °C) and this catalyst presented high stability over 10 h time-on-stream. Also, CO methanation was investigated and the results showed a complete CO conversion at 300 °C.

Enhancing the formation of nickel catalysts (111) crystal plane and CO2 methanation reactivity by external magnetic field

Nickle catalysts with acicular nanostructures are prepared by chemical reduction under different external magnetic fields. The characteristics reveal by XRD and HR-TEM illustrated that the growth of the Ni (111) plane is enhanced with the increasing in external magnetic field intensity. The shape of the Ni catalyst changes from particle to wire when the external magnetic field was greater than 1000 G. The TOF of catalysts increases linearly as the ratio of the (111)/(200) crystal planes increases, according to TPR and CO chemisorption experiments. The Ni catalyst prepared under 500 G external magnetic field shows good catalytic performance for CO2 methanation below 200 °C. Up to 99% conversion and CH4 selectivity of CO2 is obtained at 200 °C with H2/CO2 = 4.5 and GHSV ~ 1,000 h−1. Furthermore, the catalysts remine unchanged after 120 h at 180 °C. The activation energy of CO2 methanation on Ni catalysts is 84.7 kJ/mol.

Aqueous Miscible Organic LDH Derived Ni-Based Catalysts for Efficient CO2 Methanation

Converting CO2 to methane via catalytic routes is an effective way to control the CO2 content released in the atmosphere while producing value-added fuels and chemicals. In this study, the CO2 methanation performance of highly dispersed Ni-based catalysts derived from aqueous miscible organic layered double hydroxides (AMO-LDHs) was investigated. The activity of the catalyst was found to be largely influenced by the chemical composition of Ni metal precursor and loading. A Ni-based catalyst derived from AMO-Ni3Al1-CO3 LDH exhibited a maximum CO2 conversion of 87.9% and 100% CH4 selectivity ascribed to both the lamellar catalyst structure and the high Ni metal dispersion achieved. Moreover, due to the strong Ni metal–support interactions and abundant oxygen vacancy concentration developed, this catalyst also showed excellent resistance to carbon deposition and metal sintering. In particular, high stability was observed after 19 h in CO2/H2 reaction at 360 °C.

Experimental Study on CO2 Methanation over Ni/Al2O3, Ru/Al2O3, and Ru-Ni/Al2O3 Catalysts

CO2 methanation is recognized as one of the best technologies for storing intermittent renewable energy in the form of CH4. In this study, CO2 methanation performance is investigated using Ni/Al2O3, Ru/Al2O3, and Ru-Ni/Al2O3 as the catalysts under conditions of atmospheric pressure, a molar ratio of H2/CO2 = 5, and a space velocity of 5835 h−1. For reaction temperatures ranging from 250 to 550 °C, it was found that the optimum reaction temperature is 400 °C for all catalysts studied. At this temperature, the maximum values of CO2 conversion, H2 efficiency, and CH4 yield and lowest CO yield can be obtained. With temperatures higher than 400 °C, reverse CO2 methanation results in CO2 conversion and CH4 yield decreases with increased temperature, while CO is formed due to reverse water-gas shift reaction. The experimental results showed that CO2 methanation performance at low temperatures can be enhanced greatly using the bimetallic Ru-Ni catalyst compared with the monometallic Ru or Ni catalyst. Under ascending-descending temperature changes between 250 °C and 550 °C, good thermal stability is obtained from Ru-Ni/Al2O3 catalyst. About a 3% decrease in CO2 conversion is found after three continuous cycles (74 h) test.

Enhanced performance and selectivity of CO2 methanation over phyllosilicate structure derived Ni-Mg/SBA-15 catalysts

Ni and Ni-Mg phyllosilicate mesoporous SBA-15 catalysts were successfully prepared via ammonia evaporation (AE) method as evidenced by XRD, H2-TPR, TEM, FTIR and EXAFS fitting results. The catalysts derived from phyllosilicate structure exhibit superior catalytic performance in CO2 methanation as compared to catalyst prepared via wetness impregnation (WI) method due to enhanced metal-support interaction and the presence of weakly basic sites provided by surface hydroxyl groups. Incorporation of Mg into phyllosilicate structure with optimum 5 wt% is also found to increase medium basic sites, which can promote monodentate formate formation as identified by DRIFTS analysis and improve CO2 methanation activity at lower temperatures. Additionally, the turnover frequency of CO2 conversion can be well correlated with the concentration of basic sites. The strong metal-support interaction derived from phyllosilicate structure along with confinement effect of SBA-15 can suppress metal sintering, resulting in good stability.

Effect of surface properties controlled by Ce addition on CO2 methanation over Ni/Ce/Al2O3 catalyst

Ce-promoted Ni/Al2O3 catalysts with Ce contents of 0, 5, 10, 15, and 20 wt% were investigated for CO2 methanation. Ni/15Ce/Al2O3 showed good selectivity and catalytic performance in CO2 methanation and remained stable at 350 °C for 80 h with minor fluctuations. Interactions between Ni and the Ce/Al2O3 support was characterized using X-ray diffraction, temperature-programmed reduction of H2, temperature-programmed desorption of CO2, X-ray photoelectron spectroscopy, Raman spectroscopy, and thermogravimetric analysis. Addition of Ce did not increase the catalytic surface area, which can significantly enhance the heterogeneous catalytic activity. However, XPS analysis showed that the Ce on the Ni/Al2O3 catalyst changed the surface electron states of Ni, Ce, and O. Additionally, CO2 adsorption/desorption was confirmed to be related to the amount of Ce present on Ni/Al2O3 by TGA and CO2-TPD. The Ce addition thus played an important role in determining the CO2 adsorption, desorption, and conversion.

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.

Enhanced active site extraction from perovskite LaCoO3 using encapsulated PdO for efficient CO2 methanation

The extraction of metallic nanoparticles from perovskite-type oxides (ABO3) under mild reducing conditions is a novel way to prepare well-dispersed supported catalysts (B/AOδ). Herein, we found that the encapsulated PdO in perovskite LaCoO3 ([email protected]3) could facilitate the phase transformation of the perovskite structure at a low temperature owing to both strong H2 spillover of Pd and intimate interaction between the encapsulated PdO and LaCoO3. The pure LaCoO3 without PdO was relatively inert to CO2 hydrogenation (CO2 conversion <4%). In contrast, [email protected]3 exhibited excellent CO2 methanation performance with 62.3% CO2 conversion and >99% CH4 selectivity. The characterization results demonstrated that the catalytically active Co2C was in-situ formed by carburization of the extracted Co0 during CO2 methanation for the [email protected]3 sample. Whereas, the LaCoO3 with surface supported PdO (PdO/LaCoO3) showed a weak interaction and remained a perovskite structure with few Co2C active centers after the catalytic reaction, which was similar to the parent LaCoO3. Accordingly, the PdO/LaCoO3 showed an inferior catalytic performance with 31.8% CO2 conversion and 87.4% CH4 selectivity. Therefore, the designed encapsulation structure of PdO within perovskite is critical to extract metallic NPs from perovskite-type oxides, which has the potential to prepare other integrated nanocatalysts based on perovskite-type oxides.

Transition Metals Modified Ni−M (M=Fe, Co, Cr and Mn) Catalysts Supported on Al2O3−ZrO2 for Low‐Temperature CO2 Methanation

AbstractAlthough considerable efforts have been made in transforming carbon dioxide into high value‐added products, it still remains a big challenge to convert CO2 to CH4 directly at low temperature. Here, we report transition metals (including Fe, Co, Cr and Mn) modified Ni catalysts supported on Al2O3−ZrO2 via a single‐step sol‐gel method for low temperature CO2 methanation. Specially, incorporation of Mn metal into the Ni/Al2O3−ZrO2 catalyst was the most beneficial to the reduction and dispersion of NiO particles on the surface of Al2O3−ZrO2 composite support in comparison to other transition metals such as Fe, Co and Cr, which promoted the formation of active metallic Ni sites. Furthermore, the addition of Mn promoter facilitated the formation of surface oxygen vacancies, which combined with more metallic Ni active sites, thus improving the low‐temperature CO2 methanation performance significantly. An optimized Ni−Mn/Al2O3−ZrO2‐1 catalyst exhibited a superior CO2 conversion of 78 % with CH4 selectivity almost 100 % at a lower temperature of 300 °C without any deactivation in the long term 100 h reaction, which presented a potential industrial application for CO2 methanation.

Three-Dimensional Mesoporous Ni-CeO2 Catalysts with Ni Embedded in the Pore Walls for CO2 Methanation

Mesoporous Ni-based catalysts with Ni confined in nanochannels are widely used in CO2 methanation. However, when Ni loadings are high, the nanochannels are easily blocked by nickel particles, which reduces the catalytic performance. In this work, three-dimensional mesoporous Ni-CeO2-CSC catalysts with high Ni loadings (20−80 wt %) were prepared using a colloidal solution combustion method, and characterized by nitrogen adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and H2 temperature programmed reduction (H2-TPR). Among the catalysts with different Ni loadings, the 50% Ni-CeO2-CSC with 50 wt % Ni loading exhibited the best catalytic performance in CO2 methanation. Furthermore, the 50% Ni-CeO2-CSC catalyst was stable for 50 h at 300° and 350 °C in CO2 methanation. The characterization results illustrate that the 50% Ni-CeO2-CSC catalyst has Ni particles smaller than 5 nm embedded in the pore walls, and the Ni particles interact with CeO2. On the contrary, the 50% Ni-CeO2-CP catalyst, prepared using the traditional coprecipitation method, is less active and selective for CO2 methanation due to the larger size of the Ni and CeO2 particles. The special three-dimensional mesoporous embedded structure in the 50% Ni-CeO2-CSC can provide more metal–oxide interface and stabilize small Ni particles in pore walls, which makes the catalyst more active and stable in CO2 methanation.

Effect of Ni content on CO2 methanation performance with tubular-structured Ni-YSZ catalysts and optimization of catalytic activity for temperature management in the reactor

This paper presents high-performance Ni-YSZ tubular catalysts for CO2 methanation prepared by the extrusion molding. We fabricated tubular-shaped Ni-YSZ catalysts with various Ni contents (25–100 wt% NiO) and investigated the effect of Ni content on CO2 methanation performance under various temperatures and gas flow rates. Catalysts with Ni contents >75 wt% showed CH4 yields >91% above 270 °C with high CH4 selectivities (>99%). High CH4 yields were also observed under high GHSVs at 300 °C: 93% and 92% at 8700 and 17,500 h−1, respectively. Investigation of methanation with the catalysts revealed that CO2 methanation was accelerated by a localized hotspot at the reactor inlet arising from the interaction between reaction kinetics and heat generation. Using a numerical simulation, we considered the optimum arrangement of catalytic activity in the reactor to avoid hotspot generation and realize a stable high CO2 methanation performance. We can simultaneously achieve high CH4 production and prevent hotspot formation by properly arranging catalysts with different activities.

Encapsulation of Ru nanoparticles: Modifying the reactivity toward CO and CO2 methanation on highly active Ru/TiO2 catalysts

Aiming at a better understanding of the complex interactions between metal nanoparticles (NPs) and oxide supports, ranging from purely electronic metal-support interactions (EMSIs) to structural modifications associated with strong metal-support interactions (SMSIs), we investigated the impact of a temperature programmed reduction treatment (TPR) of a highly active Ru/TiO2 catalyst on its physical properties and its CO and CO2 methanation performance by kinetic and spectroscopic techniques, in combination with structural characterization. XP, EPR and DRIFT spectra resolved a significant shift of the Ru 3d levels to lower binding energies, the formation of O-vacancy defects and a red-shift of COad related bands, respectively, after the TPR sequence. This indicates an increase of the local charge density in the Ru NPs, due to charge transfer from O-vacancy defects to the Ru NPs. Finally, from CO adsorption and XPS measurements we conclude on a partial encapsulation of the Ru NPs by a TiOx layer.

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.

Enhanced catalytic performance of CO methanation over VOx assisted Ni/MCF catalyst

A series of Ni–VOx/MCF catalysts with low-temperature catalytic activity and stability were prepared for CO methanation.