Sabatier Reaction Research Articles

Electrocatalytic reduction of carbon dioxide under plasma DBD process

Carbon dioxide can be converted, by reaction with hydrogen, into fine chemicals and liquid fuels such as methanol and DME. Methane production by the Sabatier reaction opens the way of carbon recycling for a circular economy of carbon resources.The catalytic process of methanation of carbon dioxide produces two molecules of water as a by-product. A current limitation in the CO2 methanation is the ageing of catalysts, mainly due to water adsorption during the process. To avoid this adsorption, the process is operated at high temperature (300 °C–400 °C), leading to carbon deposition on the catalyst and its deactivation.To overcome this problem, a methanation plasma-catalytic process has been developed, which achieves high CO2 conversion rate (80%), and a selectivity close to 100%, working from room temperature to 150 °C, instead of 300 °C–400 °C for the thermal catalytic process.The main characteristics of this process are high-voltage pulses of few nanoseconds duration, activating the adsorption of CO2 in bent configuration and the polarization of the catalyst. The key step in this process is the desorption of water from the polarized catalyst.The high CO2 conversion at low temperature could be explained by the creation of a plasma inside the nanopores of the catalyst.

Thermal management of a Sabatier reactor for CO2 conversion into CH4: Simulation-based analysis

Converting CO2-rich waste streams such as raw biogas, landfill gas and power plant flue gas into synthetic fuels and chemicals will reduce greenhouse gas emissions, providing revenue at the same time. One option is to convert CO2 into CH4 by hydrogenation via Sabatier reaction. This synthetic methane will be renewable if the H2 required for the reaction is generated via water electrolysis using solar and wind energy or hydroelectricity. However, to realize the potential of this approach, a number of technological challenges related to the Sabatier reactor design have to be resolved, including thermal management. The high exothermicity of the Sabatier reaction can lead to reactor overheating. High temperatures are unfavorable to the exothermic and reversible methanation process, resulting in low CO2 conversions. A simulation-based study of a Sabatier reactor was performed in order to optimize the removal of heat, while maximizing CO2 conversion and CH4 production. The heat-exchanger type packed bed reactor with internal cooling by a molten salt was simulated using a transient, pseudo-homogeneous mathematical model. Reactor performance was evaluated in terms of CO2 conversion and CH4 yield. The simulation results show that feed temperature, feed flow rate, and molten salt flow rate are the crucial parameters affecting the reactor performance. For the optimized operating conditions, the model predicts CO2 conversions and CH4 yields above 90% at high reactor throughputs, with space velocities up to 10,000h−1. A preliminary techno-economic evaluation is provided: opportunities and challenges are outlined.

Methane and hydrogen in hyperalkaline groundwaters of the serpentinized Dinaride ophiolite belt, Bosnia and Herzegovina

Methane (CH4) in continental serpentinized peridotites (MSP) has been documented in numerous hyperalkaline (pH > 9) springs and gas seeps worldwide. With a dominantly abiotic origin, MSP is often associated with considerable amounts of hydrogen (H2), produced by serpentinization. Both gases may fuel microbial activity in igneous rocks and may have played roles in the origin of life. MSP is also a natural CH4 source for the atmosphere, not included in the global greenhouse-gas budget, yet. Here we document a new and major case of MSP, in the Dinaride ophiolite belt in Bosnia and Herzegovina. CH4 is dissolved (83–2706 μM) in low temperature (13–30 °C), hyperalkaline (pH 10 to 12.8) waters in six sites, sampled through springs and boreholes. Four sites (Slanac, Vlajići, Kulaši and Lješljani) show CH4 isotopic signatures typical of abiotic MSP (δ13C: −18.5 to −35.7‰; δ2H: −221 to −335.4‰); two sites (Vaićeva and Kiseljak) show a dominantly biotic signature (δ13C: −58.8 and −65.1‰; δ2H: −310.8 and −226.8‰), probably due to mixing with gas from coal-beds adjacent to the ultramafic rocks. H2 concentration is highly variable (up to 348 μM), ethane, propane and butane reach 0.13 vol.% in total, and helium isotopic composition (R/Ra: 0.12 to 0.48) reflects a dominant crustal signature. The Lješljani site features the highest pH (12.8) and CH4 emission (∼9 ton y−1) in peridotite-hosted hyperalkaline groundwater documented so far. Geological and geochemical data converge towards the hypothesis that, as proposed in similar cases, CH4 was mainly generated by Sabatier reaction between H2 (from serpentinization) and CO2 (from C-bearing rocks, in tectonic contact with the ophiolite, or other CO2 sources). CH4-H2-H2O disequilibria and Sabatier reaction constraints suggest that CH4 is not formed in the hyperalkaline water, but in water-free or unsaturated rocks hosting opportune metal catalysts (e.g., chromitites). The amount of methane released to the atmosphere from individual springs is comparable to that of conventional biotic gas seeps/springs in sedimentary basins.

Exergy Efficiency Analysis of a Power-to-Methane System Coupling Water Electrolysis and Sabatier Reaction

Power-to-methane (PtM) systems coupling solid oxide electrolysis cell (SOEC) and Sabatier reactors offers an efficient and promising pathway to integrate the renewable/nuclear power with the existing natural gas network. SOEC operates at a higher temperature and yet produce hydrogen or syngas with a controllable H2/CO ratio with higher efficiency compared to low temperature electrolyzers. Besides, with the coupling of the SOEC and the Sabatier reactor, methane can be synthesized in one reactor from renewable energy. In this study, we firstly compared the power-to-hydrogen processes using the alkaline electrolysis cell (AEC), the proton exchange membrane electrolysis cell (PEMEC) and the SOEC. A factor of 38% is used to convert electricity to primary energy for first law efficiency analysis. Exergy efficiency analysis is also carried out to distinguish the qualities of the heat, electricity and gaseous fuels. The results show the PtM system using SOEC is more efficient than those using the other electrolysis technologies due to lower overpotential and better heat coupling. Particularly, the intermediate temperate SOEC exhibits a better heat coupling with the Sabatier reactor rather than the high temperature SOEC to further improve the system efficiency. Figure 1

Heat removal and catalyst deactivation in a Sabatier reactor for chemical fixation of CO2: Simulation-based analysis

Thermo-catalytic hydrogenation of CO2 into synthetic CH4 via Sabatier reaction is an attractive route to reduce fossil fuels consumption and to limit greenhouse gas emissions, while potentially providing revenue. Hydrogen required for the reaction can be generated by water electrolysis using renewable or low carbon footprint electricity. With respect to CO2 methanation, a number of technological challenges have to be resolved in order to make this technology economically viable. The highly exothermic nature of the Sabatier reaction makes heat removal a challenging task. Another major problem is catalyst deactivation by coking caused by CH4 cracking at elevated temperatures. Maximizing CH4 production over extended periods of operation will require highly efficient heat removal to facilitate CH4 production, while minimizing catalyst deactivation. In this study, a heat-exchanger type, molten salt-cooled packed bed reactor is analyzed using a transient mathematical model. The model considers inter-compartment heat exchange and catalyst deactivation by coking, assuming the use of a Ni/Al2O3 catalyst. The reactor performance was investigated in terms of CO2 conversion and CH4 yield for the case of the feed containing CO2 and H2, and for the case of the reactor fed with biogas (40% CO2 and 60% CH4) and H2. The model predicts that, though the catalyst deactivation leads to a substantial decline in the reactor performance, CH4 yields and CO2 conversions over 80% are achievable after 10,000h of operation.

Experimental Investigation on CO2 Methanation Process for Solar Energy Storage Compared to CO2-Based Methanol Synthesis

The utilization of the captured CO2 as a carbon source for the production of energy storage media offers a technological solution for overcoming crucial issues in current energy systems. Solar energy production generally does not match with energy demand because of its intermittent and non-programmable nature, entailing the adoption of storage technologies. Hydrogen constitutes a chemical storage for renewable electricity if it is produced by water electrolysis and is also the key reactant for CO2 methanation (Sabatier reaction). The utilization of CO2 as a feedstock for producing methane contributes to alleviate global climate changes and sequestration related problems. The produced methane is a carbon neutral gas that fits into existing infrastructure and allows issues related to the aforementioned intermittency and non-programmability of solar energy to be overcome. In this paper, an experimental apparatus, composed of an electrolyzer and a tubular fixed bed reactor, is built and used to produce methane via Sabatier reaction. The objective of the experimental campaign is the evaluation of the process performance and a comparison with other CO2 valorization paths such as methanol production. The investigated pressure range was 2–20 bar, obtaining a methane volume fraction in outlet gaseous mixture of 64.75% at 8 bar and 97.24% at 20 bar, with conversion efficiencies of, respectively, 84.64% and 99.06%. The methanol and methane processes were compared on the basis of an energy parameter defined as the spent energy/stored energy. It is higher for the methanol process (0.45), with respect to the methane production process (0.41–0.43), which has a higher energy storage capability.

Catalytic Conversion of CO2 to CH4 with a Ru Catalyst: Application at Vehicle Exhaust

For the first time, catalytic conversion of CO2 to CH4 (Sabatier reaction) has been studied on real vehicle exhaust. Preliminary tests were carried out on model gas mixtures using as reactants a N2/CO2 gas mixture (CO2 = 9.5 vol% concentration similar to that of road vehicle exhaust) and pure hydrogen. Ruthenium powder (5 wt%) on alumina was used as catalyst, in a fixed bed cylindrical reactor. The operating conditions investigated are P = 1 atm, temperature in the range 160–320 °C, contact time 0.6–1.29 s, and H2/CO2 ratio 2.75–4.11. Experimental conditions were varied to study the effect of temperature, contact time, and H2/CO2 ratio on conversion, yield, and selectivity of the process. Once evaluated the performance of the catalytic process and identified the best operating conditions, real exhausts of a two-wheel motorcycle and a four-wheel gasoline vehicle were treated with the same experimental apparatus. Analyses of physical and chemical characterization of catalyst samples before and after the use were also performed. Results show that, even though best performances are generally obtained with model mixtures, high CO2 conversion together with high yield and selectivity in CH4 can be obtained with real vehicle exhausts too. Moreover, phenomena causing the deactivation of catalyst have not been observed. Results seem to indicate good opportunities for the development of the process.

Exergy Efficiency Analysis of a Power-to-Methane System Coupling Water Electrolysis and Sabatier Reaction

The seasonal and intermittent features result in the renewable power curtailment. Seasonal power storage is required to utilize the curtailed renewable power. Power-to-methane (PtM) systems coupling solid oxide electrolysis cell (SOEC) and Sabatier reactors offers an efficient and promising pathway to integrate the renewable power with the existing natural gas network. SOEC operates at a higher temperature and yet produce hydrogen or syngas with a controllable H2/CO ratio with higher efficiency compared to low temperature electrolyzers. Besides, with the coupling of the SOEC and the Sabatier reactor, methane can be synthesized in one reactor from renewable energy. In this study, we firstly compared the power-to-hydrogen processes using the alkaline electrolysis cell (AEC), the proton exchange membrane electrolysis cell (PEMEC) and the SOEC. Exergy efficiency analysis is also carried out to distinguish the qualities of the heat, electricity and gaseous fuels. The results show the PtM system using SOEC is more efficient than those using the other electrolysis technologies at high current density due to lower polarization and better heat coupling. For SOEC, H2O/CO2 co-electrolysis coupling with methanation reactor exhibits a slightly lower exergy efficiency at low current density than H2O electrolysis coupling Sabatier reactor, but exceeds at high current density. At the H2O flow rate of 0.036 mol s-1 m-2 and H/C ratio of 5.5, a peak exergy efficiency of 75.66% is achieved at the current density of -5500 A m-2.

Design and feasibility analysis of a Power-to-Gas plant in Germany

The Power-to-Gas process chain could play a significant role in the future energy system. Renewable electric energy (wind or solar) can be transformed into storable methane via electrolysis and subsequent methanation through Sabatier reaction. The aim of this research is a design and techno-economic analysis of a Power-to-Gas process. The plant is integrated with an anaerobic digester to have the carbon dioxide, by the up-grading of the biogas, for the Sabatier reaction. Electrical and thermal power are produced by a cogeneration system. A business to business analysis, not present in other literature works, is carried out for the process: it is then the main innovation of this research. Results show that to produce 1000 kWel, 10 kmol/h of methane are needed: in the Sabatier reaction, the flow rate of carbon dioxide and hydrogen are respectively equal to 4.6 kmol/h and 22 kmol/h. The power of the eolic park is 1980 kWel. In the business to business analysis, a swot analysis (strengths, weaknesses, opportunities and threats) is developed. Success critical factors and risks are found in addition to several strategies that must to be involved to be successful in the project. The success of the process is the use of 100% of renewable energy to produce a need for the society, enhancing a waste material as the carbon dioxide to produce methane. The techno-economic feasibility shows that the plant is economic feasible with VAN, PBP and LCOE equal to 8 million €,4 years and 260 €/MWh respectively. Economic incentives are also obtained.The future construction of the plant in Germany will verify the obtained results and future researches should realize the most sustainable process with the lower environmental impact.

A combination anaerobic digestion scheme for biogas production from dairy effluent—CSTR and ABR, and biogas upgrading

Anaerobic digestion of low-strength dairy waste water was used for the production of biogas which is aimed at serving as a concentrated carbon dioxide (CO2) source for further methanation. Using hydrogen (which can be produced via electrolysis using renewably sourced electricity), the CO2 fraction of the produced biogas can be used as a mechanism to store surplus electricity by the Sabatier process, which converts the CO2 fractions to methane (CH4), i. e. synthetic natural gas. This study investigates the use a combined reactor scheme for the anaerobic digestion of dairy waste water, and the further upgrading of the biogas products from the process. A combination pilot scale process was established with a 90 d start-up time using a 1 m3 continuous stirred tank reactor (CSTR) and a 0.2 m3 baffled reactor (ABR) in series. The system was fed at constant retention time in the ABR of 1.6 d and with varying substrate organic loading rates between 1.25 and 4.50 kg m−3 d−1. The average chemical oxygen demand (COD) removal was 82% with a biogas yield of 0.26 m3 kg−1. The use of the derived biogas for the Sabatier process to convert hydrogen into CH4 showed no disadvantages compared to synthetic gas mixtures. The combination of CSTR and ABR overcame the individual disadvantages of both reactor types. The investigated anaerobic digestion system can be further optimized and adopted to replace conventional waste water treatment systems.

Model‐based Optimal Sabatier Reactor Design for Power‐to‐Gas Applications

AbstractThe existing infrastructure for natural gas storage and transport made the Sabatier process an attractive step within the power‐to‐gas process chain for intermittent renewable energy storage. A model‐based optimal design for the methanation of carbon dioxide with hydrogen to methane under process‐wide constraints is presented. After inclusion of the downstream units into the analysis, the product methane fulfils the specifications for the natural gas grid. The optimization goal was to maximize the space–time yield by applying the systematic flux‐oriented elementary process function methodology. The optimum temperature and concentration profiles along the reaction coordinate were first determined, after which they were approximated using two reaction configurations: 1) a hydrophilic membrane reactor and 2) a cascade of polytropic reactors with interstage condensation. The results show that an optimized cascade of three polytropic fixed bed reactors (e.g., optimum temperature profile) and two intermediate condensation steps is the best technical approximation for maximizing the space–time yield.

Experimentation and CFD modelling of a microchannel reactor for carbon dioxide methanation

The methanation of carbon dioxide (CO2) via the Sabatier process is increasingly gaining interest for power-to-gas application. In this investigation, a microchannel reactor was evaluated for CO2 methanation at different operational pressures (atmospheric, 5bar, and 10bar), reaction temperatures (250–400°C) and space velocities (32.6–97.8L.gcat−1.h−1). The recommended operation point was identified at reactor conditions corresponding to 5bar, 400°C, and 97.8L.gcat−1.h−1. At this condition, the microchannel reactor yielded good CO2 conversion (83.4%) and high methane (CH4) productivity (16.9L.gcat−1.h−1). The microchannel reactor also demonstrated good long-term performance at demanding operation conditions relating to high space velocity and high temperature. Subsequently, a CFD model was developed to describe the reaction-coupled transport phenomena within the microchannel reactor. Kinetic rate expressions were developed and validated for all reaction conditions to provide reaction source terms for the CFD modelling. Velocity and concentration profiles were discussed at different reaction conditions to interpret experimental results and provide insight into reactor operation. Overall, the results reported in this paper could give fundamental design and operational insight to the further development of microchannel reactors for CO2 methanation in power-to-gas applications.

Renewable Energy Storage System Based on a Power-to-Gas Conversion Process

The increasing penetration of renewable energy generation in the electric energy market is currently posing new critical issues, related to the generation prediction and scheduling, due to the mismatch between power production and utilization. In order to cope with these issues, the implementation of new large scale storage units on the electric network is foreseen as a key mitigation strategy.Among large scale technologies for the electric energy storage, the Power-to-Gas solution can be regarded as a long-term viable option, provided that the conversion efficiency is improved and aligned with other more conventional storage alternatives.In this study, a Power-to-Gas storage system is investigated, including as main components a high-temperature electrolyzer for hydrogen generation and a Sabatier reactor for methane production. The high-temperature Solide Oxide Electrolyser Cell (SOEC) technology, currently under development, is considered as a promising solution for hydrogen generation, due to the expected higher efficiency values, in comparison with conventional low-temperature electrolysis technologies. In order to evaluate the performance of the system and the energy efficiency, in this study a numerical model of the SOEC integrated with the Sabatier reactor has been implemented, including also the necessary additional auxiliaries, which can significantly affect the energy conversion performance. The whole energy conversion and storage system has been analyzed, taking into account different layout variants, by means of Aspen HysysTM numerical tool, based on a lumped modelling approach.The various Power-to-Gas storage configurations have been compared, with the aim to optimize both the system's efficiency and the composition of the produced gas stream.

An Alumina-Supported Ni-La-Based Catalyst for Producing Synthetic Natural Gas

LaNi5, known for its hydrogen storage capability, was adapted to the form of a metal oxide-supported (γ-Al2O3) catalyst and its performance for the Sabatier reaction assessed. The 20 wt % La-Ni/γ-Al2O3 particles were prepared via solution combustion synthesis (SCS) and exhibited good catalytic activity, achieving a CO2 conversion of 75% with a high CH4 selectivity (98%) at 1 atm and 300 °C. Characteristics of the La-Ni/γ-Al2O3 catalyst were identified at various stages of the catalytic process (as-prepared, activated, and post-reaction) and in-situ DRIFTS was used to probe the reaction mechanism. The as-prepared catalyst contained amorphous surface La–Ni spinels with particle sizes <6 nm. The reduction process altered the catalyst make-up where, despite the reducing conditions, Ni2+-based particles with diameters between 4 and 20 nm decorated with LaOx moieties were produced. However, the post-reaction catalyst had particle sizes of 4–9 nm and comprised metallic Ni, with the LaOx decoration reverting to a form akin to the as-prepared catalyst. DRIFTS analysis indicated that formates and adsorbed CO species were present on the catalyst surface during the reaction, implying the reaction proceeded via a H2-assisted and sequential CO2 dissociation to C and O. These were then rapidly hydrogenated into CH4 and H2O.

CO2 methanation: Optimal start‐up control of a fixed‐bed reactor for power‐to‐gas applications

Utilizing volatile renewable energy sources (e.g., solar, wind) for chemical production systems requires a deeper understanding of their dynamic operation modes. Taking the example of a methanation reactor in the context of power‐to‐gas applications, a dynamic optimization approach is used to identify control trajectories for a time optimal reactor start‐up avoiding distinct hot spot formation. For the optimization, we develop a dynamic, two‐dimensional model of a fixed‐bed tube reactor for carbon dioxide methanation which is based on the reaction scheme of the underlying exothermic Sabatier reaction mechanism. While controlling dynamic hot spot formation inside the catalyst bed, we prove the applicability of our methodology and investigate the feasibility of dynamic carbon dioxide methanation. © 2016 American Institute of Chemical Engineers AIChE J, 63: 23–31, 2017

Life Cycle Assessment of Power-to-Gas: Syngas vs Methane

Power-to-Gas enables the integration of renewable electricity and carbon into the chemical industry. The electricity is used to produce hydrogen, which is subsequently converted with CO2 as the renewable carbon source. The resulting products can be used as feedstock for the chemical industry replacing current fossil-based feedstock. Because the integration of renewable electricity and carbon into the chemical industry is mainly environmentally motivated, we identify the conditions under which Power-to-Gas pathways are environmentally beneficial. The conditions are expressed as environmental threshold values for electricity supply. The threshold values are derived by a comparative life cycle assessment (LCA) of Power-to-Gas pathways to fossil-based processes. We analyze Power-to-Gas pathways to synthetic natural gas (Power-to-SNG) and to syngas (Power-to-Syngas). SNG is produced by the Sabatier reaction; syngas by reverse water gas shift (rWGS) and dry reforming of methane (DRM). The threshold values for e...

Storing renewable energies in a substitute of natural gas

This paper proposes a way to obtain valuable electric power and valuable fuel starting from renewable variable electric power plus biomass and/or waste products.Biomass/biofuel can be oxyburned using electrolytic oxygen to generate electric power. Gas turbines or internal combustion engines are suitable to such a task, but there is the problem of very high temperatures connected to oxycombustion. In the case of gas turbine the inlet temperature could be controlled by adding steam and/or carbon dioxide, while in the case of internal combustion engines only carbon dioxide could be used. In such a way the exhaust gas continues to be formed by carbon dioxide and steam which can be easily separated by condensation. Carbon dioxide is fed to a Sabatier process together with electrolytic hydrogen to generate a gas with characteristics similar to natural gas.Although electrolytic hydrogen could be used directly both in internal combustion engines and fuel cells, significant problems to hydrogen distribution and on-board storing still exists. Therefore the substitute of natural gas could be a real bridge solution for the short/medium term. A simulation has been carried out and the resulting efficiencies range from 0.52 to 0.58.

Temperature Dependence of Solar Light Assisted CO2 Reduction on Ni Based Photocatalyst

Methanation of CO2 by H2 can be in the future an important reaction to store the surplus of renewable electricity during production peaks. The catalytic thermal CO2 methanation (the Sabatier reaction) can be carried out at temperatures above 250 °C using Ni supported on silica-alumina (Ni/SiO2–Al2O3). Recently it has been observed that this exothermic reaction can be promoted by solar light irradiation of Ni/SiO2–Al2O3 at initial near ambient temperatures. In the present work we provide a study of the influence of the initial temperature on the photoassisted Ni/SiO2–Al2O3 methanation of CO2, under conditions in which the dark reaction is not observed. An increase of the photoassisted methanation rate with the initial temperature in the range from ambient to 150 °C has been observed. The reaction kinetics for lower initial temperatures exhibited an induction period not observed for reactions performed at higher temperatures. The results are discussed in terms of the operation of plasmon photo activation in which the energy of photons is thermalised in a confined space of the active nanoparticles leading to locally high temperatures and the simultaneous photogeneration of electrons and positive holes.

Optimization and simulation of the Sabatier reaction process in a packed bed

The Sabatier reaction in a testing packed bed was investigated experimentally and theoretically, and was used to convert waste carbon dioxide and hydrogen to provide needed water for closing the life‐support loop on orbit in space. A three‐dimensional model including fluid flow, gas dispersion, heat and mass transfer, and chemical reaction was developed by coupling some semi‐empirical correlated equations in chemical engineering science into computational fluid dynamics theory. Good agreements between the simulating results and experimental data for the effect of some parameters on reaction verified this model, for example, heat exchange between reactor and atmosphere, the material property of reactor, the catalyst deactivated and gas mass flux and so on. By using this model as the designing tools, an optimized packed bed is proposed. Compared with the testing packed bed, the relevant reactor length can be reduced from 220 to 150 mm with the same hydrogen conversion and lower pressure drop. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2879–2892, 2016

Use of membranes in the implementation of the "Power to gas" concept

This paper presents the possibility of membrane use in the Power to Gas concept. Power to Gas is a concept of electrical energy conversion into the gaseous methane by well known Sabatier reaction. This reaction needs pure reagents such as carbon dioxide and hydrogen. The polymeric dense membranes could be used to obtain pure carbon dioxide from the stream of biogas or flue gas. The products of this reaction are methane and water. For methane dewatering one could also use polymeric membranes. The paper presents literature data as well as the Author’s own research results.