Manganese(III) Tetraphenylporphyrin Encapsulated by Ion-Modified Hexagonal Mesoporous Silica With Unexpected Enhanced Epoxidation Selectivity

Abstract

Tetraphenylporphyrin manganese (III) chloride (Mn-TPP) was encapsulated into hexagonal mesoporous silica (HMS) modified by different Lewis acid ions Al, Ti, Zr, and W, which have been tested for selective oxidation of unsaturated olefins and more challenged fatty acid esters under mild condition. Pure W-HMS support displayed no epoxidation activity under the present condition; nonetheless, an unexpected enhanced selectivity for Mn-TPP/W-HMS (90%) with respect to the other samples, especially to homogenous Mn-TPP, indicated the promoted role of W ions over the support. In addition, TG analysis and wetting contact angle measurement were determined in order to reveal the hydrophobic nature of heterogeneous materials, which has been preliminarily scrutinized as the factor influencing catalytic selectivity. That is, Mn-TPP/W-HMS exhibited around 90% selectivity because of a better hydrophobic nature.