Dependence of CO 2 Conversion to CH 4 on the CO 2 Flow Rate in a Helicon Discharge Plasma

Kamataki

et al. 2023

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This study aimed to realize in-situ resource utilization in deep-space missions. The Sabatier reaction is used to generate CH4 from CO2, which accounts for 95% of the Martian atmosphere, and H2 from H2O on Mars. In general, thermal catalysis at temperatures above 250 °C drives the process. This high-temperature process, however, causes catalyst deactivation due to overheating. Plasma catalysis drives low-temperature reactions by excitation and decomposition of source gases via electron impact. We investigated the effect of removing H2O from gas phase in the reaction with Cu and Ni catalysts using molecular sieves in this study. The reverse reaction can be aided by OH radicals derived from H2O. Therefore, CO2 conversion increased from 49.4 to 69.1% for Cu catalysts with molecular sieves, and CH4 selectivity increased from 3.49 to 6.33%. These findings imply that removing H2O can suppress the reverse reactions.

Section: Introductionmentioning

confidence: 99%

Improving the efficiency of Sabatier reaction through H₂O removal with low-pressure plasma catalysis

Kamataki

et al. 2023

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“…We achieved 90% conversion of CO 2 and 35% CH 4 selectivity at RT using a helicon plasma with high electron density and electron temperature. 33) In the experiments, no catalyst was employed. The reaction rate constant for CO 2 conversion by electron impact was derived.…”

Section: Introductionmentioning

confidence: 99%

Contribution of active species generated in plasma to CO₂ methanation

Okumura

et al. 2023

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CO2 methanation is an effective technology for CO2 reduction. Generally, methanation reactions are accelerated using thermal catalysts. However, the temperature control is difficult because CO2 methanation is an exothermic reaction, and the catalyst is deactivated by overheating. Plasma catalysis can solve this problem by driving this reaction at lower temperatures. Therefore, in this study, we investigated the contribution of the active species generated in the plasma to CO2 methanation. We found that the density of active species is linearly related to the power density, and in particular, the CH4 generation rate is determined by the CO-derived active species, not the H-derived active species. Furthermore, with an increase in the catalyst temperature, a new reaction pathway for CH4 production is added. The results of this study contribute to the understanding of the relationship between the active species produced in plasma and CO2 methanation.

“…19) In our previous research, we achieved a CH 4 selectivity of 35% and a CO 2 conversion of 90% at room-temperature, using pulse-modulated helicon plasma. 27) This indicates that the generation of active species by plasma control is important for realizing high-rate methane production at lowertemperatures.…”

Section: Introductionmentioning

confidence: 99%

Effect of gas flow rate and discharge volume on CO₂ methanation with plasma catalysis

Ideguchi

et al. 2022

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CO2 methanation can be a key technology for realizing a sustainable society. CH4 is used as an energy carrier and raw material for chemical products, thereby contributing to the reduction of CO2 emissions. Methanation with plasma catalysis lower the process temperature, which can improve the throughput and stability. In this study, we investigated the effect of the gas flow rate and the discharge volume on CO2 methanation, using a low- pressure CCP reactor. Higher gas flow rates can increase the rate of CO2 throughput, but the CH4 selectivity decreases owing to the reduced transportation rate of the reactants to the catalyst surface. Increasing the discharge volume is effective in improving the transportation rate. This study suggested that the structure of the reactor significantly affect the CH4 generation rate.