CONVERSION OF SYNTHESIS GAS TO DIMETHYL ETHER OVER BIFUNCTIONAL CATALYTIC-SYSTEMS

The conversion of syngas to hydrocarbon synfuels via methanol (MeOH) involves dimethyl ether (DME) as a key intermediate stage. An attractive option would involve direct production of a mixture of oxygenates (MeOH + DME). Microreactor studies have been used to investigate the oxygenate synthesis over bifunctional multicomposite catalysts comprising a methanol synthesis component and a dehydration partner such as alumina, amorphous silica-alumina, Y zeolite, mordenite, or ZSM-5 zeolites. By directing the syngas conversion toward DME in a single-step reaction, the overall chemical equilibrium was changed in favor of the production of DME/MeOH. The synergistic combination of MeOH synthesis, hydrocondensation to DME, and the concurrent water gas shift (WGS) reaction, which provides the necessary CO2, gives high CO conversions and oxygenate yields far greater than the conventional MeOH synthesis. Of all the dehydration components tested, gamma-alumina provided the best conversions of CO and the highest DME/MeOH yields.