A Study of V-Pillared Layered Double Hydroxides as Catalysts for the Epoxidation of Terpenic Unsaturated Alcohols

Mg,Al-Layered double hydroxides (LDHs) are pillared with vanadium under mildly acidic conditions. Via XRD, Raman, and IR characterization, it is confirmed that the material is a phase-pure LDH with decavanadate (V10O286−) anions between the brucite sheets. This V10-LDH has the highest activity for the epoxidation of geraniol when used with tert-butyl hydroperoxide as the oxidant in anhydrous toluene. In a series of tests, the possible release of catalytically active dissolved V from the catalyst is investigated. Under all conditions tested, V10-LDH behaves as a heterogeneous catalyst, in contrast with some other tested V-containing materials (e.g., VAPO-5, or V in a siliceous matrix). Regioselectivity in the epoxidation of geraniol evidences the coordination of the alcohol group of geraniol on the active V center. Finally, it is demonstrated that the V10-LDH catalyst can be applied to the epoxidation of a series of allylic and homoallylic alcohols, mostly of terpene origin.