Epoxidation of Allyl Chloride to Epichlorohydrin by a Reversible Supported Catalyst with H2O2 under Solvent-Free Conditions

Allyl chloride was epoxidized to epichlorohydrin with H2O2 under solvent-free conditions in 94% selectivity using a new reversible supported catalyst, heteropolyphosphatotungstate/silanized silica gel. By the action of H2O2 the heteropolyphosphatotungstate dissolves from the carrier surface and forms an active homogeneous reagent. When all H2O2 is consumed, the reduced catalyst redeposits on the support carrier. The supported catalyst retains the character of a homogeneous catalyst during reaction but exhibits heterogeneous properties upon work-up. The solid-supported catalyst is easily isolated and can be reused. The reaction system for synthesis of epichlorohydrin therefore avoids the serious pollution issues known from the commercialized chlorohydrin methods. Some other olefins can also be epoxidized by this catalytic system under neat conditions.