Cyclodehydration of diethylene glycol (DEG) catalyzed by clay mineral sepiolite

Clay mineral sepiolite exhibited high selectivity for the catalytic convers ion of diethylene glycol (DEG) into 1,4-dioxane. The selectivity for the 1, 4-dioxane formation depended on weight hourly space velocity (WHSV) and the tunnel structure of sepiolite. When an excess DEG was supplied over the ad sorption capacity of the tunnels in sepiolite, the selectivity for 1,4-diox ane formation from DEG decreased and by-products formation increased. These results indicate that cyclodehydration of DEG takes place in the internal space of the intracrystalline tunnels of sepiolite and by-products formatio n occurs on the outer surface of sepiolite. The Mg(II) ion along the tunnel wall of sepiolite acts as an active site for the cyclodehydration. (C) 199 9 Elsevier Science B.V. All rights reserved.