Synthesis of Dimethyl Ether over Modified H-Mordenite Zeolites and Bifunctional Catalysts Composed of Cu/ZnO/ZrO 2 and Modified H-Mordenite Zeolite in Slurry Phase Nahid Khandan Æ Mohammad Kazemeini Æ Mahmoud Aghaziarati Received: 18 September 2008 / Accepted: 10 November 2008 / Published online: 26 November 2008 Ó Springer Science+Business Media, LLC 2008 Abstract Synthesis of dimethyl ether (DME) via meth- anol dehydration were investigated over various catalysts, and via direct CO hydrogenation over hybrid catalysts composed of Al-modified H-Mordenite zeolite and Cu/ZnO/ZrO 2 . H-Mordenite zeolite exhibited the highest activity in dehydration of methanol. However, its selec- tivity toward dimethyl ether was rather low. For this reason, the H-Mordenite was modified. Modification of zeolites was performed by wet impregnation method and considered catalysts were characterized by AAS, XRD and NH 3 -TPD analyses. Results of catalytic tests indicated that H-Mordenite modified with 8 wt% aluminum oxide was the best catalyst for synthesis of dimethyl ether from methanol, in which methanol conversion and DME selec- tivity were 99.8 and 96.8%, respectively, without noticeable change in catalyst stability. For direct synthesis of dimethyl ether from synthesis gas, hybrid catalysts were prepared by coprecipitation sedimentation method. It was found that optimum ratio of methanol synthesis catalyst to methanol dehydration catalyst is 2:1. In this case, CO conversion and DME selectivity were 64 and 78.8%, respectively, with good catalyst stability. Ultimately, it was concluded that the hybrid catalyst composed of Cu/ZnO/ ZrO 2 and Al-modified H-Mordenite zeolite is an appropriate catalyst for direct synthesis of dimethyl ether from the synthesis gas. Keywords Methanol  Dimethyl ether  Synthesis gas  H-Mordenite zeolite  Cu/ZnO/ZrO 2 Abbreviations HM H-Mordenite DME Dimethyl ether MeOH Methanol 1 Introduction Dimethyl ether (DME) is a useful chemical intermediate for production of many important chemicals such as dimethyl sulfate, methyl acetate, and light olefins [1, 2]. DME is also used as an aerosol propellant because of its environmentally benign properties and the belief that chlorofluorocarbons (CFCs) destroy the ozone layer of the atmosphere [3]. Moreover, DME has recently been suggested as a clean alternative fuel for diesel engines with much lower NO x emission, near-zero smoke production, and less engine noise compared with traditional diesel fuels [4]. Several solid acid catalysts have been studied for the title reaction [5–14]. Dehydration of methanol, as shown in Eq. (1), involves a large amount of water as a by-product. During the reaction, both methanol and water compete with each other for the same sites on the catalyst [15–18]. 2CH 3 OH ! CH 3 OCH 3 þ H 2 O þ HCs ð1Þ Also, most of these solid-acid catalysts produce undesir- able side products such as hydrocarbons (and coke) due to the presence of strong acid sites and the high dehydration temperature [10, 11]. Thus, extensive research has been N. Khandan  M. Kazemeini (&) Department of Chemical and Petroleum Engineering, Sharif University of Technology, Azadi Ave., P.O. Box 11365-9465, Tehran, Iran e-mail: kazemini@sharif.edu; mkaz62@yahoo.com M. Aghaziarati Faculty of Materials, Department of Chemistry and Chemical Engineering, Malek Ashtar University of Technology, Lavizan, P.O. Box 15875-1774, Tehran, Iran e-mail: maziarati@mut.ac.ir 123 Catal Lett (2009) 129:111–118 DOI 10.1007/s10562-008-9779-8