A series of H-MFI zeolites at different Si/Al ratio were prepared and characterised in terms of physical and chemical properties and morphology. The zeolites were tested in the methanol dehydration reaction to Dimethyl Ether (DME), aiming at investigate the catalyst stability as a function of the reaction temperature. According to literature the temperature interval was set in the way of keeping a DME selectivity close to one and this required a lower temperature when increasing the catalyst acidity. Conversion data were measured at different catalyst amount/reactant flow rate ratios and the initial rate was extrapolated from the early points. Arrhenius plot of these initial rates as a function of temperature allowed to estimate the (apparent) activation energy as a function of the catalyst acidity (from 50 to 70 kJ/mop. Main findings were the confirmation that the catalyst performance is favoured by the higher acidity, but also samples at the lower is the Si/Al ratio exhibited the higher activation energy, revealing as the more sensitive to temperature variation. (C) 2013 Elsevier B.V. All rights reserved.