Preparation of a Nanorod-like Mo-VOx Catalyst for Gas Phase Selective Oxidation of Methyl Lactate with Air

Abstract

Selective oxidation of higher alcohols to carbonyls is one of the most important chemical transformations in research and industrial chemistry. Gas phase selective oxidation of alcohols with air as oxidant is a “green chemistry” synthesis path, although it is a great challenge to maintain high conversion with high selectivity. In this work, we synthesized nanorod-like Mo-VOx catalysts through regulation of the Mo/V ratio via a solid-state reaction method, and the group of Mo promoted VOx catalysts exhibited the combination of high catalytic activity and selectivity. The methyl pyruvate (MP) selectivity over 0.17Mo-VOx catalysts reached 79.6% at a relatively lower reaction temperature of 180 °C with 90.1% methyl lactate conversion. The characterization results revealed that the 0.17Mo-VOx catalysts showed a nanorod-like morphology with larger specific surface area and smaller crystalline size, generated active MoV2O8 crystalline phase, and could give rise to active V4+/V5+ redox couples as well as surface oxygen species. In terms of structure–activity relationship, when Mo was initially introduced into VOx, the MoV2O8 phase was gradually formed, and MP yield over yMo-VOx catalysts increased significantly together with V4+ proportion. However, excessive Mo would not form more active MoV2O8 phases, and the MP yield decreased.