Alcohol dehydrations over ZSM-5 type zeolites, montmorillonite clays and pillared montmorillonites

The reactions of aliphatic alcohols (ethanol, I-propanol and 2-propanol) we re studied at 1 atm and 150-300 degrees C by using ZSM-5 type zeolites, mon tmorillonites, and pillared montmorillonites. With H-ZSM-5 (X) Y zeolites, the total number of acid sites increases with a decrease of SiO2/Al2O3 mola r ratio (X) and calcining temperature (Y). In addition, apparent increase i n the ratio of strong to weak acid sites occurs with increasing X or decrea sing Y. The acidities of M-ZSM-5 (51) 600 zeolites follow the sequence: Li congruent to Na > K > Cs. Pillared clays exhibit both larger surface areas and more acid sites than the clays. The alcohol conversions decrease in the order of 2-propanol > 1-propanol > ethanol, in accordance with the relativ e stabilities of the corresponding carbenium ions. The catalytic activities are parallel to the total number of catalyst acid sites and the reaction t emperature. Favorable formations of ethers are observed at low reaction tem perature and small contact time on a catalyst with weak acid strength. Simp le consecutive reactions and combined pathway of parallel and consecutive r eactions are proposed, respectively, for the dehydration of ethanol and for those of 1-propanol and 2-propanol.