Split feed strategy for low-permselective membrane reactors: A simulation study for enhancing CO2 methanation

Abstract

A non-isothermal membrane reactor (MR) was simulated to study the production of methane through CO2 hydrogenation. The reaction kinetics of a commercial catalyst and the extrapolated properties of a steam-selective sodalite (SOD) membrane were considered. A traditional fixed-bed reactor (TR) was also simulated and its performance compared with that obtained with a MR in the temperature and pressure range of 250−410 °C and 1−7 atm, respectively. The results indicate that at higher temperatures the SOD membrane removes not only water but also a significant amount of reactants from the reaction medium. It was demonstrated that this can be solved splitting the feed between both chambers (retentate and permeate), reducing the reactants loss due to a lower driving force. However, the methane permeation through the SOD membrane limits the process performance. The simulation of an ideal MR (i.e. membrane with infinite selectivity to water), with the perspective of assessing its potential, allowed reaching a conversion of 89.5 % (at 390 °C and 1 atm), being able not only to improve the catalytic bed conversion of a TR in the same conditions (82.7 %), but also to surpass the chemical equilibrium conversion (85.4 %), showing that the full potential of the MR technology for this application still depends on the development of adequate membranes.