A process for dehydrating methanol to dimethyl ether product in the presence of a catalyst and a promoter, wherein the catalyst is at least one aluminosilicate zeolite, wherein: —the aluminosilicate zeolite is selected from: (i) a zeolite having a 2-dimensional framework structure comprising at least one channel having a 10-membered ring, and having a maximum free sphere diameter of at least 4.8 Angstroms; (ii) a zeolite having a 3-dimensional framework structure comprising at least one channel having a 10-membered ring; or (iii) a zeolite comprising at least one channel having a 12-membered ring; —the promoter is selected from one or more compounds of Formula I: (I) wherein Y is selected from a C1-C4 hydrocarbyl substituent, and wherein each of X and any or all of the Z's may independently be selected from hydrogen, halide, a substituted or unsubstituted hydrocarbyl substituent, or a compound of the formula —CHO, —CO2R, —COR, or —OR, where R is hydrogen or a substituted or unsubstituted hydrocarbyl substituent, and wherein the molar ratio of promoter to methanol is maintained at less than 1.