The interaction effects of dehydration function on catalytic performance and properties of hybrid catalysts upon LPDME process

Three bi-functional catalysts have been prepared by physical mixing of a commercial methanol synthesis catalyst (CuO–ZnO–Al2O3) with three different methanol dehydration catalysts including: H-MFI90, γ-Al2O3 and H-Mordenite in order to investigate the role of interaction effects of dehydration component on characteristic properties and performance of these admixed catalysts. The bi-functional catalysts have been characterized by XRD, N2 adsorption, H2-TPR, NH3-TPD and XRF techniques and tested in a mixed slurry bed reactor at the same operating conditions (T = 240 °C, P = 50 bar, H2/CO = 2, SV = 1100 ml g-cat− 1 h− 1) for 60 h time on stream. Among the examined bi-functional catalysts, the physical mixture of KMT + HMFI-90, which had lower reducing peak temperature (T = 200 °C), higher SCu (39.1 m2 g-cat− 1) and Cu Dispersion (11.6%), showed higher XCO (84 mol%), yield of DME (YDME = 55.5 mol%), DME selectivity (SelectDME = 66.7 mol%) and also good stability over 60 h time on stream as compared to the other catalysts. This could be assigned, from NH3-TPD results, to more middle strength acidic sites of H-MFI90 zeolite (SiO2/Al2O3 = 90, total acid site density = 476 µmol/g-cat) which inhibits detrimental interactions with methanol synthesis catalyst and deep dehydration of methanol.