Silicon nitride as a new support for copper catalyst to produce acrolein via selective oxidation of propene with very low CO2 release

Abstract

To obtain thermally stable copper-based catalysts with excellent catalytic performance in the selective propene (C3H6) oxidation reaction, amorphous silicon nitride (Si3N4) was selected to anchor active copper species using a deposition–precipitation approach followed by air calcination at different temperatures. We found that the thermal treatment temperature remarkably modified the reactivity of the copper catalyst, and the 800 °C-calcined 10 wt% Cu/Si3N4 showed superior catalytic activity with 24.0% propene conversion and 86.2% acrolein selectivity at 325 °C, featuring a turnover frequency as high as 80.6 h−1. With the help of transmission electron microscopy, X-ray absorption fine structure, and in situ X-ray diffraction, we have identified that the larger Cu2O species account for the highly efficient formation of acrolein at 325 °C. From the CO temperature-programmed reduction results, we have confirmed that the presence of surface copper hydroxyls (Cu–OH) was closely related to the acrolein selectivity, since they favored CO2 generation at the beginning of the reaction. Furthermore, surface copper hydroxyls can be effectively tuned by optimizing the air calcination temperature and thus improve the catalytic activity.