Catalytic dehydration of methanol to dimethyl ether (DME) is performed in an adiabatic fixed bed heterogeneous reactor by using acidic gamma-alumina. By changing the mean average temperature of the catalyst bed (or operating temperature of the reactor) from 233 up to 303 degrees C, changes in methanol conversion were monitored. The results showed that the conversion of methanol strongly depended on the reactor operating temperature. Also, conversion of pure methanol and mixture of methanol and water versus time were studied and the effect of water on deactivation of the catalyst was investigated. The results revealed that when pure methanol was used as the process feed, the catalyst deactivation occurred very slowly. But, by adding water to the feed methanol, the deactivation of the gamma-alumina was increased very rapidly; so much that, by increasing water content to 20 weight percent by weight, the catalyst lost its activity by about 12.5 folds more than in the process with pure methanol. Finally, a temperature dependent model developed to predict pure methanol conversion to DME correlates reasonably well with experimental data. (c) 2008 Elsevier Ltd. All rights reserved.