Synthesis, modification and application of layered double hydroxides as catalysts for Baeyer-Villiger oxidation

Abstract

Baeyer-Villiger oxidation can be performed using both homogeneous and heterogeneous catalysts. This study deals with the preparation of tin-containing heterogeneous catalysts based on mixed oxides and their application in a model reaction, Baeyer-Villiger oxidation of citral to 2,6-dimethyl-1,5-dien-1-yl formate and subsequent hydrolysis to melonal. Hydrotalcites with different molar ratios of Mg:Al were prepared by co-precipitation method, calcined, and subsequently impregnated by SnCl2. Activity of such prepared catalysts was compared with Sn-mixed oxide catalysts in which SnO2 was already incorporated during coprecipitation and Sn-MCM-41 catalyst prepared by impregnation. The prepared catalysts were characterized. The catalytic activity of the prepared catalysts was tested in the model reaction using H2O2 as an oxidizing agent. Total conversion and almost 100% selectivity to the desired product was achieved at 80 °C after 2 h using mixed oxide modified with 5 wt% tin and 1.5 molar equivalents of a 50% H2O2 solution.