Catalyst configuration for the direct synthesis of dimethyl ether from CO and CO2 hydrogenation on CuO–ZnO–MnO/SAPO-18 catalysts

Abstract

Three catalytic bed configurations for the direct DME synthesis have been studied using CuO–ZnO–MnO and SAPO-18 as metallic and acid functions, respectively. The runs have been carried out in a fixed bed reactor under the following conditions: Feed, H2 + CO + CO2; 275 °C; 30 bar; 5.02 gcat h mol C −1 ; H2/COx = 3. The results (COX conversion, DME yield and selectivity) show that a better contact between phases, thus, incorporating both functions in a bifunctional catalyst (CZMn/S-18) results in a mayor DME yield and selectivity than the other configurations. The effects of the fed CO2 content and reaction temperature have been assessed for the bifunctional catalyst. Although the production of DME decreases with co-feeding CO2 with syngas, for a CO2/(CO2 + CO) ratio in the feed higher than 0.5 this effect is attenuated, which is interesting for the conversion of CO2. The highest DME selectivity (> 94%) is obtained at 275 °C, with moderate deactivation by coke.