Dimethyl Ether Synthesis with in situ H₂O Removal in Fixed-Bed Membrane Reactor: Model and Simulations

Abstract

The potential and limits of in situ removal of water under dimethyl ether (DME) synthesis conditions in a fixed-bed membrane reactor were studied numerically. The motivation for in situ H 2 O removal during DME synthesis by means of hydrophilic membranes is to displace the water−gas shift equilibrium to enhance conversion of CO 2 into methanol to improve DME productivity. In CO-rich feeds, methanol yield/selectivity increases/decreases slowly with increasing H 2 O permeance because only small amounts of water are removed from the system. Methanol dehydration is not inhibited by water, and DME selectivity is not improved significantly with increasing H 2 O permeance. When CO is gradually replaced with CO 2, with the increase of H 2 O membrane permeance and H 2 O removal, methanol yield and DME selectivity are favored and the fraction of unconverted methanol is reduced as the dehydration reaction is accelerated due to reduced kinetic inhibition by H 2 O.