Synergistic Pt/MgO/SBA-15 nanocatalysts for glycerol oxidation in base-free medium: Catalyst design and mechanistic study

Enhanced metal-support interaction is the key for selective oxidation of glycerol to value-added carboxylic acids. However, the rational control of interfacial properties still remains a significant challenge. In this work, we prepared hybrid Pt/MgO/SBA-15 catalysts for the facile oxidation of glycerol to glyceric acid in the absence of liquid alkalis. It was found that the confinement effect of SBA-15 leads to restricted Pt nanoparticles in the MgO/SBA-15 channel with a unique strip shape. Such a morphology and the strong electron coupling effect between Pt and MgO species synergistically enhanced glycerol oxidation over Pt-MgO sites. A volcanic-shaped relationship between Mg/Si ratio and catalytic performance was established experimentally, and the Pt/MgO/SBA-15 (0.1) catalyst showed excellent combined selectivity for C-3 products (glyceric acid, glyceraldehyde and dihydroxyacetone) with a remarkable turn over frequency (TOF) of 1671.2 h(-1) higher than the reported catalysts under base-free conditions. Furthermore, density functional theory (DFT) calculations confirmed that the oxidation reaction could be promoted by oxygen defects of MgO sites, resulting in a reduction of the energy barriers for C-H and O-H activation. These insights may provide a new way to the supported solid base catalyst design and mechanistic study. (C) 2019 Elsevier Inc. All rights reserved.