Catalytic CO2 Methanation Research Articles

Container-Sized CO2 to Methane: Design, Construction and Catalytic Tests Using Raw Biogas to Biomethane

Direct catalytic methanation of CO2 (from CO2/CH4 biogas mixture) to produce biomethane was conducted in a pilot demonstration plant. In the demonstration project (MeGa-StoRE), a biogas desulfurization process and thermochemical methanation of biogas using hydrogen produced by water electrolysis were carried out at a fully operational biogas plant in Denmark. The main objective of this part of the project was to design and develop a reactor system for catalytic conversion of CO2 in biogas to methane and feed biomethane directly to the existing natural gas grid. A process was developed in a portable container with a 10 Nm3/h of biogas conversion capacity. A test campaign was run at a biogas plant for more than 6 months, and long-time operation revealed a stable steady-state conversion of more than 90% CO2 conversion to methane. A detailed catalytic study was performed to investigate the high activity and stability of the applied catalyst.

Tailoring Rh content on dendritic fibrous silica alumina catalyst for enhanced CO2 capture in catalytic CO2 methanation

Dendritic fibrous X%Rh/FSA catalysts were synthesized by the microwave-assisted microemulsion and wetness impregnation approaches. Catalytic CO2 methanation was performed at temperature ranging of 150‒500 °C and atmospheric pressure with stoichiometric feed composition. FESEM and TEM micrographs confirmed the spherical bicontinuous concentric lamellar morphology of FSA offering high accessibility of capturing CO2 to the active sites, thus promotion of heterogenous catalysis activity. H2-TPR and pyrrole adsorbed IR spectroscopy results reveals that the metal-support interaction and degree of basicity strength were enormously enhanced with the increasing Rh content. The 1%Rh appeared to be the optimal loading with respect to the CO2 conversion and CH4 formation rate as a function of temperature, accredited to its medium basicity strength and fibrous morphology. The in situ FTIR analyses showed that medium basic sites promoted the desired carbonate species that readily participate into hydrogenation compared to strong basic sites. In addition, CH4/CO2 ratio indicates that the rate of CO hydrogenation was superior to that of RWGS over Rh/FSA catalysts. The absence of graphitic carbon for all spent Rh/FSA catalysts in post-characterization analyses suggests that their excellent catalytic performance could be assigned to the preservation of most active sites owing to enhanced CO2 adsorption on catalyst surface which effectively remove amorphous carbon deposits via CO2 gasification process.

Working diagrams to identify the operating range of a bubbling fluidized bed reactor for the CO2 methanation

AbstractFluidized bed reactors for the catalytic CO2 methanation is a promising concept within the power‐to‐gas (methane) process. Due to the intermittency of renewable electricity generation and thus hydrogen production, the subsequent methanation reactor should also be able to operate at lower feed flow rates, while maintaining fluidized bed conditions. Bubbling fluidized bed reactors offer the required flexibility as shown with the new type of working diagrams. These working diagrams visualize a decision window for (a) determining the reactor diameter and (b) operating the fluidized bed reactor with a turndown ratio of 0.5‐1.1. Reducing the turndown ratio (ie, inlet flow rate) could lead to defluidization, thus increasing temperature or reducing the pressure are alternatives to maintain fluidization conditions. The former method is not desired, as a temperature increase would significantly reduce the CH4 yield due to thermodynamic constraints and therefore reduce the overall efficiency. An industrial CO2 methanation reactor, for example, that is designed for 10 bara (1 bara = 100 kPa) and 340°C with a total inlet flow rate of 5000 m3N · h−1 (H2/CO2 = 4) can be operated at a turndown ratio of 0.5 (2500 m3N · h−1) at the same temperature and the same u0/umf ratio by reducing the pressure to 5 bara with only a slight decrease in the CO2 equilibrium conversion from 96.7% to 94.6%.

Insights into the catalytic CO2 methanation of a boiling water cooled fixed-bed reactor: Simulation-based analysis

This article presents the simulation-based analysis of experimental results from a catalytic fixed-bed reactor for the methanation of CO2. During previously published experiments, temperature profiles inside bidisperse catalyst-silicon carbide fixed-beds were gathered and reactant conversions at the reactor outlet measured. On the basis of the temperature profiles along the fixed-bed length and outlet reactant conversions, a procedure for the numerical characterisation of these results was developed. Primary parameters like the inserted multipoint thermocouple and the heat transfer coefficient between reactor wall and surrounding boiling water cooling are systematically investigated. Concerning the binary bidisperse fixed-beds of porous catalyst cylinders and highly thermal conductive silicon carbide, a simple numerical method for the determination of the effective heat conductivity of the bed is presented. The modelling of effective reaction rates within an industrial sized catalyst and reactor is a non-trivial task, due to interlinking aspects like intrinsic reaction rate and internal and external transport limitations. Intrinsic reaction rate, internal and external transport limitations are linked, what makes a separate investigation challenging. Thus, a step by step analysis is presented and the single effects investigated in detail. From the results of the stepwise numerical characterisation, an excellent agreement between experiments and numerics was reached. Additionally, a novel partially resolved 3D fixed-bed reactor model is presented and selected results like particle overheating presented. Overall the present numerical investigations provided a deep insight into the methanation of CO2 in a cooled fixed-bed reactor.

A review of recent catalyst advances in CO2 methanation processes

This review focuses on various catalytic CO2 hydrogenation approaches for converting CO2 to fuels such as CH4. The catalytic CO2 methanation using thermal, catalytic-membrane, photo and plasma energy assisted processes were covered. The recent catalysts developments in thermo-catalytic systems for CO2 methanation in thermal process with respect to the nature of active catalytic centres and their performance were presented. Followed by the technological development of catalytic-membrane process and its advantages in overcoming thermodynamic equilibrium activities were also discussed. Additionally, the catalytic CO2 hydrogenation process assisted with plasma and photo energy were also covered with respect to the catalyst structures, CO2 conversion and selectivity towards various products. Several highly emerging in situ characterization techniques such as operando XAS and DRIFTS were used to understand the state of catalyst surface and reaction intermediates involved in CO2 methanation reaction. Furthermore, parameters affecting the selectivity towards desired products and methods to improve the performance are explained in greater details. Finally, a section for technological challenges of CO2 methanation in various processes are summarized and an outlook for future directions of the development of catalysts was provided to overcome the CO2 conversion and selectivity towards desired products limitations to eradicate the problems associated with global warming.

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.

Synthetic natural gas production from CO2 and renewable H2: Towards large-scale production of Ni–Fe alloy catalysts for commercialization

Synthetic natural gas (SNG) is one of the promising energy carriers for the excessive electricity generated from variable renewable energy sources. SNG production from renewable H2 and CO2 via catalytic CO2 methanation has gained much attention since CO2 emissions could be simultaneously reduced. In this study, Ni–Fe/(Mg,Al)Ox alloy catalysts for CO2 methanation were prepared via hydrotalcite precursors using a rapid coprecipitation method. The effect of total metal concentration on the physicochemical properties and catalytic behavior was investigated. Upon calcination, the catalysts showed high specific surface area of above 230 m2 g−1. Small particle sizes of about 5 nm were obtained for all catalysts, even though the produced catalyst amount was increased by 10 times. The catalysts exhibited excellent space-time yield under very high gas space velocity (34,000 h−1), irrespective of the metal concentration. The CO2 conversions reached 73–79% at 300 °C and CH4 selectivities were at 93–95%. Therefore, we demonstrated the potential of large-scale production of earth-abundant Ni–Fe based catalysts for CO2 methanation and the Power-to-Gas technology.

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.

Green Synthetic Fuels: Renewable Routes for the Conversion of Non-Fossil Feedstocks into Gaseous Fuels and Their End Uses

Innovative renewable routes are potentially able to sustain the transition to a decarbonized energy economy. Green synthetic fuels, including hydrogen and natural gas, are considered viable alternatives to fossil fuels. Indeed, they play a fundamental role in those sectors that are difficult to electrify (e.g., road mobility or high-heat industrial processes), are capable of mitigating problems related to flexibility and instantaneous balance of the electric grid, are suitable for large-size and long-term storage and can be transported through the gas network. This article is an overview of the overall supply chain, including production, transport, storage and end uses. Available fuel conversion technologies use renewable energy for the catalytic conversion of non-fossil feedstocks into hydrogen and syngas. We will show how relevant technologies involve thermochemical, electrochemical and photochemical processes. The syngas quality can be improved by catalytic CO and CO2 methanation reactions for the generation of synthetic natural gas. Finally, the produced gaseous fuels could follow several pathways for transport and lead to different final uses. Therefore, storage alternatives and gas interchangeability requirements for the safe injection of green fuels in the natural gas network and fuel cells are outlined. Nevertheless, the effects of gas quality on combustion emissions and safety are considered.

Catalytic methanation of CO2 in biogas: experimental results from a reactor at full scale

Methanation technology for direct catalytic upgrading of CO2 in biogas is proven ready for full scale implementation.

A Facile Method for Preparing UiO-66 Encapsulated Ru Catalyst and its Application in Plasma-Assisted CO2 Methanation.

With increasing applications of metal-organic frameworks (MOFs) in the field of gas separation and catalysis, the preparation and performance research of encapsulating metal nanoparticles (NPs) into MOFs (M@MOF) have attracted extensive attention recently. Herein, an Ru@UiO-66 catalyst is prepared by a one-step method. Ru NPs are encapsulated in situ in the UiO-66 skeleton structure during the synthesis of UiO-66 metal-organic framework via a solvothermal method, and its catalytic activity for CO2 methanation with the synergy of cold plasma is studied. The crystallinity and structural integrity of UiO-66 is maintained after encapsulating Ru NPs according to the X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). As illustrated by X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), and mapping analysis, the Ru species of the hydration ruthenium trichloride precursor are reduced to metallic Ru NPs without additional reducing processes during the synthesis of Ru@UiO-66, and the Ru NPs are uniformly distributed inside the Ru@UiO-66. Thermogravimetric analysis (TGA) and N2 sorption analysis show that the specific surface area and thermal stability of Ru@UiO-66 decrease slightly compared with that of UiO-66 and was ascribed to the encapsulation of Ru NPs in the UiO-66 skeleton. The results of plasma-assisted catalytic CO2 methanation indicate that Ru@UiO-66 exhibits excellent catalytic activity. CO2 conversion and CH4 selectivity over Ru@UiO-66 reached 72.2% and 95.4% under 13.0 W of discharge power and a 30 mL·min−1 gas flow rate (), respectively. Both values are significantly higher than pure UiO-66 with plasma and Ru/Al2O3 with plasma. The enhanced performance of Ru@UiO-66 is attributed to its unique framework structure and excellent dispersion of Ru NPs.

Nickel@Siloxene catalytic nanosheets for high-performance CO2 methanation

Two-dimensional (2D) materials are of considerable interest for catalyzing the heterogeneous conversion of CO2 to synthetic fuels. In this regard, 2D siloxene nanosheets, have escaped thorough exploration, despite being composed of earth-abundant elements. Herein we demonstrate the remarkable catalytic activity, selectivity, and stability of a nickel@siloxene nanocomposite; it is found that this promising catalytic performance is highly sensitive to the location of the nickel component, being on either the interior or the exterior of adjacent siloxene nanosheets. Control over the location of nickel is achieved by employing the terminal groups of siloxene and varying the solvent used during its nucleation and growth, which ultimately determines the distinct reaction intermediates and pathways for the catalytic CO2 methanation. Significantly, a CO2 methanation rate of 100 mmol gNi−1 h−1 is achieved with over 90% selectivity when nickel resides specifically between the sheets of siloxene.

Catalytic CO Methanation over Mesoporous ZSM5 with Different Metal Promoters

The carbon monoxide methanation has possessed huge potential as an effective method to produce synthetic natural gas (SNG). The basic requirements such as high catalytic activity at low temperatures (<500 °C) and high stability throughout all temperatures is needed for an ideal methanation catalysts. The ultimate goal of the study is to examine the influential of different metal promoters towards catalytic properties and catalytic CO methanation performance. A series of metal promoters (Rh, Co, Pd and Zn) mesoporous ZSM5 were synthesized using an incipient-wetness impregnation method and evaluated for catalytic CO methanation. XRD analysis showed that only metal oxides and no metallic phase of Rh, Co, Pd, and Zn were observed. The nitrogen physisorption analysis showed that mZSM5 possessed high surface area and micro-mesoporosity with intra- and interparticle pores. FESEM analysis illustrated that mZSM5 had typical coffin-type morphology and Rh metal dispersed on the surface of the support was confirmed by EDX analysis. Moreover, Rh (CO conversion = 95%, CH4 yield = 82%) and Co (CO conversion = 91%, CH4 yield = 71%) promoters showed significant improvement in CO methanation. On the other hand, Pd (CO conversion = 18%, CH4 yield = 12%) and Zn (CO conversion = 10%, CH4 yield = 9%) promoters had only low benefit to the CO methanation. This study affirmed that the catalytic activity of CO methanation was influenced by the variation in the type of metal loading due to different nature of metallic phases and their synergistic interaction with the supporting material.

Low-pressure glow discharge plasma-assisted catalytic CO2 hydrogenation—The effect of metal oxide support on the performance of the Ni-based catalyst

Abstract Low-pressure, glow discharge plasma catalytic CO2 methanation was investigated in the presence of Ni/Al2O3, Ni/SiO2 and Ni/CeO2-ZrO2 catalyst. The prepared samples were characterized by ICP, XRD, low-temperature N2 sorption, H2-TPR, dielectric constant measurement and FT-IR in-situ adsorption of NO, CO and CO2. The performed characterization allowed selecting the optimal conditions of catalyst preparation as well as explaining the results of plasma-catalytic tests. The application of various supports had a significant effect on plasma properties and thus dissociation of CO2 in the gas phase. It affected plasma stability as well, which decreased with the increasing values of the dielectric constant. Ni/Al2O3 sample showed the best performance in terms of CH4 production. The positive effect on the catalytic activity in thermal CO2 methanation was observed for Ni/Al2O3 and Ni/SiO2 samples. Adsorption of probe molecules (NO, CO and CO2) performed for fresh reduced and spent catalysts allowed to get insights into plasma-catalytic reaction mechanism and to explain the effect of plasma promotion on the performance of the catalysts in thermal CO2 methanation.

Process Modeling of an Innovative Power to LNG Demonstration Plant

The continuous increase in electricity production from renewable energy sources (RESs) introduces the intrinsic fluctuating characteristic of RESs in the electric power grid, causing nontrivial grid management issues (e.g., grid congestion). In this work, an innovative power to liquefied methane concept was developed, and process simulations for a 200 kWel demonstration plant were carried out. The proposed concept is based on water electrolysis to produce hydrogen, CO2 capture from air using solid adsorption materials, catalytic CO2 methanation, gas separation, and a single mixed refrigerant (SMR) liquefaction process. The gas separation unit produces an exhaust stream, rich in not only hydrogen and carbon dioxide but also methane, that is recycled to the methanation unit inlet. A thermodynamic analysis excluded the possibility of carbon deposition formation in the methanation reactor due to methane recirculation. The gas separation system was designed using a combination of temperature swing adsorption t...

Hydride‐Enhanced CO2 Methanation: Water‐Stable BaTiO2.4H0.6 as a New Support

AbstractCatalytic CO2 hydrogenation to CH4 provides a promising approach to producing natural gas, and reducing the emissions of global CO2. However, the efficiency of catalytic CO2 methanation is limited by slow kinetics at low temperatures. This study first demonstrates that an air‐ and water‐stable perovskite oxyhydride BaTiO2.4H0.6 could function as an active support material for Ni‐, Ru‐based catalysts for CO2 methanation at 300–350 °C, a relatively lower temperature. With the oxyhydride support, the activity for Ni and Ru increases by a factor of 2–7 when compared to the BaTiO3 oxide support. Kinetic analysis shows reduced H2 poisoning probably due to spillover, implying that the activity change is due to the kinetics being influenced by hydride. Furthermore, the oxyhydride‐supported Ni catalyst is also durable with its catalytic performance preserved for at least 10 h under a humid environment at elevated temperatures. It is anticipated that these perovskite oxyhydrides will shed new light on the design of high‐efficiency metal‐based catalysts for water‐involved catalytic reactions.

New Ni-based quaternary disk-shaped catalysts for low-temperature CO2 methanation: Fabrication, characterization, and performance

Ni-based quaternary disk catalysts were manufactured for low-temperature CO2 methanation reactions, and the reaction activity was examined with respect to the thermal treatment conditions. By applying varying reduction and combustion treatments, the same catalysts were compared, and the Ni oxidation conditions and physical features were confirmed through X-Ray diffraction, scanning electron microscopy, and energy dispersive X-ray analyses. In addition, oxygen adsorption/desorption changes were measured by temperature-programmed reduction after pre-treating with oxygen and hydrogen. The reduction treatment catalyst showed a conversion of 20% at 280 °C, and the 70% calcined catalyst did not form a NiO crystalloid. The activation of the catalyst increased because of NiO movement on the catalyst surface, which enabled easy transformation to metallic Ni. The prepared catalyst is a highly reactive, yet stable, candidate for practical catalytic CO2 methanation.

PAA/alumina composites prepared with different molecular weight polymers and utilized as support for nickel‐based catalyst

AbstractMesoporous alumina, as a porous, high specific surface area, high activity, and heat stable material, has been widely used as an industrial adsorbent, catalyst, and catalyst support. The modification of alumina with organic polymers has been widely investigated in recent years. In this study, we compared the dependence of the adsorption of a polyelectrolyte, poly(acrylic acid) (PAA) on γ‐alumina particles on polymer size via Fourier transform infrared spectroscopy, thermogravimetry, nitrogen adsorption–desorption isotherm analysis, and atomic absorption spectrophotometry. We found that PAA with a hydrodynamic diameter greater than the alumina pore size would only adsorb on the outer surface of the oxides. For polymers with hydrodynamic diameters smaller than the alumina pore size, PAA infiltration resulted in a monolayer coverage of both the outer and inner surfaces of the oxide. Among the three PAA that could infiltrate the alumina pores, the one with the smallest molecular weight showed the highest adsorbed amount on alumina. The temperature, pH, concentration, and ionic strength of the PAA solutions were varied to illustrate the physicochemical differences of the prepared polymer/oxide composite materials. The high PAA‐loaded composites were treated with a nickel ion solution, converted to Ni/alumina catalysts, and used in the methanation of carbon dioxide. The Ni/alumina catalysts were analyzed with X‐ray diffraction and temperature‐programmed reduction to illustrate the structural characteristics. The catalytic CO2 methanation of the catalyst samples revealed that a solution pH value higher than pKa of PAA favored the formation of catalysts with high catalytic activity.

Modifying surface properties of KIT-6 zeolite with Ni and V for enhancing catalytic CO methanation

The surface of the KIT-6 zeolite was modified with different amounts of Ni and V to promote the catalytic properties for CO methanation. A series of xNi-yV/KIT-6 with various Ni and V contents were prepared by the incipient-wetness impregnation method. The modified surfaces were characterized using N2 adsorption-desorption, Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), hydrogen temperature-programmed reduction (H2-TPR), Fourier transformed infrared spectroscopy (FT-IR), Raman, X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), and energy-dispersive X-ray spectroscopy (EDX), respectively. The characterization results illustrated that the modification of V species was able to significantly promote low-temperature catalytic performance below 350°C compared to that of unmodified Ni/KIT-6, which was likely due to an increase in the H2 uptake accompanied by enhanced CO dissociation derived from stronger electron transfer from V species to Ni0. Correspondingly, the xNi-yV/KIT-6 catalysts exhibited a distinct enhancement in CO conversion, CH4 selectivity and CH4 yield over unmodified Ni/KIT-6. Among all catalysts, 20Ni-2V/KIT-6 showed the best catalytic performance, corresponding to nearly 100% CO conversion and 85% CH4 yield at a low temperature of 300°C. Furthermore, 20Ni-2V/KIT-6 presented enhanced coking-resistant and anti-sintering properties during a 60h-lifetime test at 500°C and 1atm with a high weight hourly space velocity (WHSV) of 60000ml/g/h.

Catalytic methanation of CO2 with NH3

The catalytic methanation of CO2 with ammonia over Ni, Pt, and Ru catalysts impregnated on γ-alumina was carried out in a fixed-bed reactor under atmospheric pressure at 573–873K. The methanation of CO2 with NH3 is considered to occur in two stages –NH3 decomposition into H2/N2 followed by CO2 methanation with H2. 1wt% Pt/γ-Al2O3 exhibited low activity for NH3 decomposition and CO2 methanation with H2. Both 5wt% Ni/γ-Al2O3 and 1wt% Ru/γ-Al2O3 showed high activity for NH3 decomposition and CO2 methanation with H2, but Ru/γ-Al2O3 was much more active. For CO2 methanation with ammonia, only Ru/γ-Al2O3 was significantly active. The yield of CH4 increased with increased Ru loading and reaction temperature, but was limited by thermodynamic equilibrium at higher temperatures. Ammonia decomposition is more facile than CO2 methanation on the Ru/γ-Al2O3 catalyst and CO2 methanation is the rate limiting step.