Selective oxidation of methacrolein to methacrylic acid over CsH3PMo11VO40 with structural defects

Abstract

A novel synthetic strategy using microwave-assisted precipitation was proposed to prepare defective CsH3PMo11VO40 for the oxidation of methacrolein (MAL) to methacrylic acid (MAA). A systematic comparison of catalysts synthesized using different heating methods and preparation conditions was conducted. Microwave treatment was found to accelerate the crystallization rate of the catalyst and increase vanadyl species (VO2+) content on its surface, yielding the formation of defective Keggin structures. A moderate degree of defective Keggin units improves the oxidation capacity of active Mo species and facilitates the activation of oxygen into lattice oxygen, enhancing the oxidation of MAL. Therefore, the catalyst obtained through microwave heating demonstrates significantly improved catalytic performance compared to the one prepared via conventional heating. The defective Keggin structure plays a key role in catalytic enhancing. Under optimal conditions, the 70MH-40 catalyst exhibits the highest MAL conversion of 90.3% and MAA selectivity of 87.2%.