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, gamma-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, N-2 adsorption, H-2-TPR, NH3-TPD and XRF techniques and tested in a mixed slurry bed reactor at the same operating conditions (T=240 degrees C, P=50 bar, H-2/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 degrees C), higher S-cu (39.1 m(2) g-cat(-1)) and Cu Dispersion (11.6%), showed higher Xco (84 mol%), yield of DME (Y-DME =55.5 mol%), DME selectivity (Select(DME)=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 umol/g-cat) which inhibits detrimental interactions with methanol synthesis catalyst and deep dehydration of methanol. (C) 2008 Elsevier B.V. All rights reserved.