Comparison of intensified reactor systems for one–step conversion of CO2–containing syngas to DME

Abstract

Comparison is drawn among two intensified reactor systems proposed for meeting precise temperature regulation requirement of the direct conversion of syngas to dimethyl ether (DME). In the first (microchannel) system, reaction channels washcoated with physical mixture of catalysts for methanol synthesis (Cu–ZnO/Al2O3) and dehydration (HZSM–5) are accompanied by cooling channels. Decoupled catalytic reaction and cooling functions are conducted in interconnected adiabatic packed–bed reactors and microchannel heat exchangers, respectively, in the second (cascade) system. Both systems are compared under identical inlet conditions, catalyst types and residence times via computational modeling coupled with realistic constraints. Upon syngas (CO2/COx (COx:CO+CO2)=0.2 and H2/COx=2.0) feeding at 493 K, 50 bar and residence time of 1.05 kgcat.s/mol, conversions of CO and CO2, and DME yield are found as 27.4, 6.6 and 18.8%, respectively, for the microchannel, and 23.3, 4.6 and 13.8%, respectively, for the cascade system. At a pilot–scale gasifier syngas throughput of 0.77 mol/s, volumes of the microchannel and cascade systems, the latter being composed of five reactors and four heat exchangers, are computed as 104.5 and 56.2 liters, respectively. Productivity (molDME/m3.s) of the microchannel system (0.15) remains below that of the cascade (0.20), which, however, suffers from notable pressure drop.