High-pressure hydrothermal dope Ce into MoVTeNbOx for one-step oxidation of propylene to acrylic acid

Abstract

A high-pressure hydrothermal method was employed to introduce Ce element facilely into MoVTeNbO_x catalysts in 0.5 h. It was indicated that Ce atoms were doped into the framework of MoVTeNbO_x without changing the unique crystal structure of MoVTeNbO_x. The introduction of Ce could facilitate the formation of oxygen vacancies and improve the redox ability of surfacial V. However, it was worth noting that the doping amount of Ce was negatively related to the content of M1 active phase. Within a certain range, the catalytic performance could be improved by sacrificing an appropriate amount of M1 phase. In the conversion of propylene to acrylic acid, the highest yield of 58.2% was obtained under catalyst MoVTeNbCeO_x (V: Ce =1: 0.05) at 380 °C with the M1 phase content of 81.6%. The appropriate amount of Ce doping improved the propylene conversion by more than 20% compared to undoped. Moreover, the changes in Gibbs free energy of the rate-limiting step of direct oxidation of propylene before and after Ce doping were evaluated by Density functional theory (DFT). It is illustrated that the doping of Ce is thought to affect the main reason for the reduction of Gibbs free energy.