Small-sized cuprous oxide species on silica boost acrolein formation via selective oxidation of propylene
AUTHORS: Guo, LL; Yu, J; Wang, WW; Liu, JX; Guo, HC; Ma, C; Jia, CJ; Chen, JX; Si, R
Oxide-supported copper-containing materials have attracted considerable research attention as promising candidates for acrolein formation. Nevertheless, the elucidation of the structure-performance relationships for these systems remains a scientific challenge. In this work, copper oxide clusters deposited on a high-surface-area silica support were synthesized via a deposition-precipitation approach and exhibited remarkable catalytic reactivity (up to 25.5% conversion and 66.8% selectivity) in the propylene-selective oxidation of acrolein at 300 degrees C. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy combined with X-ray absorption fine structure measurements of the catalyst before and after the reaction confirmed the transformation of the small-sized copper oxide (CuO) clusters into cuprous oxide (Cu2O) clusters. With the aid of in situ X-ray diffraction and in situ dual beam Fourier transform infrared spectroscopy (DB-FTIR), the allyl intermediate (CH2=CHCH2*) was clearly observed, along with the as-formed Cu2O species. The intermediate can react with oxygen atoms from neighboring Cu2O species to form acrolein during the catalytic process, and the small-sized Cu2O clusters play a crucial role in the generation of acrolein via the selective oxidation of propylene. (C) 2021, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.