Dehydration of Alcohols over Zeolite Catalysts

Zeolites represent an interesting class of alcohol dehydration catalysts because their properties can be modified systematically by ion-exchange or chemically by replacement of silica, thus changing their acidity and therefore activity and selectivity. 

Mass-transfer Effects. - Zeolites possess a large internal surface area and are necessarily subject to mass-transfer effects, although there have been relatively few studies of these. Swabb and Gates observed that for H-mordenite at low temperatures (155°C), rate was independent of crystallite size for methanol dehydration, but at higher temperature rate variation was consistent with a Thiele model. 

Ignace and Gates examined t-butyl alcohol dehydration on H-mordenite and calculated that the largest molecules which can pass each other in the pores should possess critical diameters summing 13 A. 

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