Effects of Gamma-Alumina Grain Size on Methanol Dehydration to Dimethyl Ether at Different Temperature and Weight Hourly Space Velocity

In this paper the effects of catalyst grain size, feed temperature and weight hourly space velocity on dimethyl ether production by dehydration of methanol are investigated. Commercial gamma alumina is used as dehydration catalyst in an adiabatic fixed bed reactor. Catalyst grain sizes are changed from 0.063 up to 2 mm, and the feed temperatures are changed from 200 up to 320 °C. Another parameter which is changed is weighthourly space velocity. This parameter is changed from 10 up to 90 h-1. Experimental design was optimized by the Taguchi method. The obtained results show that methanol conversion is increased by decreasing of catalyst grain sizes. But, the slip of changes converges to a fixed value, gradually. This phenomenon can be explained by mass transfer effects. Also, the experimental obtained results show that conversion values are increased by increasing feed temperature and decreased by increasing weight hourly space velocity. So that, by increasing temperature from 230°C to 320°C at 10h-1, the methanol conversion increased from 20 to 70%, and when weight hourly space velocity is changed from 10 to 90h-1 at 260°C the methanol conversion decreased from 65 to 15%.