Enhancement of dimethylether yield by reverse shift reaction in the direct dimethylether synthesis

The reverse shift reaction was used to mitigate CO₂ and to adjust H₂/CO. The key concept is to convert CO₂ to CO using excess hydrogen from a reformer and CO₂ from a DME reactor. Membrane process was selected for separating hydrogen from the reformer stream, where H₂/CO ratio can be adjusted to be 1∼2 for DME synthesis. The separated hydrogen was combined with CO₂ from the DME synthesis reactor, which is introduced into a reverse shift reactor to convert CO₂ into CO. The simulation result showed DME yield of above 97% based on feed carbon and could mitigate CO₂. The reverse water shift reaction temperature should be above 600°C to achieve 60% conversion of CO₂. The commercial shift reaction catalysts such as Cu/Zn/Al or Fe/Cr catalysts at the temperature above 600°C were rapidly deactivated at the high temperature in CO₂-H₂ stream. However, ZnO based catalyst showed the high activity and stability. This is an abstract of a paper presented at the AIChE Annual Meeting (San Francisco, CA 11/12-17/2006).