Frequency Response Analysis of the Unsteady-State CO/CO2 Methanation Reaction: An Experimental Study

The utilization of renewable electricity for power-to-gas (PtG) applications induces fluctuations in the H2 availability from water electrolysis. For subsequent methanation of CO or CO2 the unsteady-state operation of the respective reactor allows to minimize H2 storage capacities. However, the impact of temporal fluctuations in feed gas composition on the methanation reaction and the respective transient kinetics has not yet been fully understood. We investigated the methanation of various CO/CO2 (COx) feed gas mixtures under periodically changing gas compositions with emphasis on the effect of the frequency on the reactor response. We show that the frequency response of CH4 exhibits a characteristic hysteresis, which depends on the switching direction between COx-lean and COx-rich feeds and their composition. From the shape of the hysteresis we are able to conclude on the preferred COx species being hydrogenated to CH4 under respective conditions, which also provides mechanistic insights. By applying high cycling frequencies, the highly reactive species present under CO methanation conditions can even selectively be activated, which explains the higher reactivity compared to steady-state conditions reported, frequently.

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

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.

A CFD study on the performance of CO2 methanation in water-permeable membrane reactor system

CO2 hydrogenation is one of the important routes for CO2 utilization to address the global warming issue, which has aroused much attention in recent years. A novel water-permeable membrane reactor...