The conversion of syngas into dimethyl ether has been studied over physical mixtures of a Cu/ZnO based catalyst and a zeolite. Theta-1, ZSM-23, ferrierite, ZSM-5 and mordenite were used. The zeolites were separated after reaction and characterised by temperature programmed oxidation, XRD, and GC–MS of the entrained hydrocarbons. Theta-1 and ferrierite were found to have the most stable performance and the highest selectivity to DME. Deactivation is shown to be faster for structures with enough space to accommodate bulky carbonaceous deposits such as mordenite and ZSM-5. Longer diffusion paths associated with larger crystallites also contributed to rapid loss of activity for ZSM-23. The zeolite topology was found to influence the nature of the entrained alkylbenzenes.