Preparation of Silica Catalysts with Sulfo Groups and Their Acid Catalysis

Abstract

Three types of silica catalysts with sulfo groups were prepared. Silica was heated under reflux with 1, 3-propanesultone in toluene (type A). Silica was heated under reflux with sodium O, O'-diethyl(3-sulfonatepropyl)phosphonate in ethanol and then ion-exchanged Na for H (type B). Silica was heated under reflux with trichloro(phenethyl)silane in dioxane, and then heated under reflux with chlorosulfouric acid in chloroform (type C). These compounds were used as catalysts for 2-propanol dehydration and methyl t-butyl ether (MTBE) from methanol and isobutene. The activity, life, thermal stability of these catalysts were investigated.
On both react ions, the order of the catalytic activity were as follows; type C>type A>type B (Table 4 and 6). The rate constants of 2-propanol dehydration per acid site with type C and Amberlyst 15 were larger than these of type A and type B (Table 5). The rate difference may depend on the nature of their acid sites.
Type B catalyst was the most stable in thermal treat ment among the prepared catalysts (Fig.2, Table 3 and 4).
All of the prepared catalysts were active for MTBE synthesis. No deactivation was observed at 82°C for 6 h, When type A and type B were used. MTBE was synthesized with 100% selectivity (Table 6).