Water distribution in a sorption enhanced methanation reactor by time resolved neutron imaging

Abstract

Water adsorption enhanced catalysis has been recently shown to greatly increase the conversion yield of CO₂ methanation. However, the joint catalysis and adsorption process requires new reactor concepts. We measured the spatial water distribution in a model fixed bed reactor using time resolved neutron imaging. Due to the high neutron attenuation coefficient of hydrogen, the absorbed water in the sorption catalyst gives a high contrast allowing us to follow its formation and map its distribution. At the same time, the product gas was analysed by FTIR-gas analysis. The measurements provided crucial insights into the future design of sorption reactors: during the sorption enhanced reaction, a reaction front runs through the reactor. Once the extension of the reaction front reaches the exhaust, the conversion rate of sorption enhanced methanation decreases. The existence of a reaction front running through the reactor is prerequisite for a high conversion rate. We give a simple model of the experimental results, in particular the conditions, under which a reaction front is established. In particular the latter effect must be taken into account for the dimensions of a large scale reactor.