文献类型：期刊文献

英文题名：Kinetic Insights into the Tandem and Simultaneous Mechanisms of Propylene Epoxidation by H2 and O2 on Au-Ti Catalysts

作者：Du, Wei[1];Zhang, Zhihua[1];Tang, Yanqiang[1];Wang, Qianhong[1];Song, Nan[1];Duan, Xuezhi[1];Zhou, Xinggui[1]

机构：[1]East China Univ Sci & Technol, State Key Lab Chem Engn, Shanghai 200237, Peoples R China

年份：2023

卷号：13

期号：3

起止页码：2069

外文期刊名：ACS CATALYSIS

收录：;EI(收录号：20230513473953);WOS:【SCI-EXPANDED(收录号:WOS:000924794800001)】；

基金：This work was financially supported by the Ministry of Science and Technology of the People's Republic of China under the Research Fund for National Key R & D Program of China (2021YFA1501403) , the Natural Science Foundation of China (22038003, 21922803, 22178100, and 22208093) , the Innovation Program of the Shanghai Municipal Education Commission, the Program of Shanghai Academic/Technology Research Leader (21XD1421000) , and the Shanghai Science and Technology Innovation Action Plan (22JC1403800) .

语种：英文

外文关键词：tandem catalysis; kinetics; gold; TS-1; propylene epoxidation

摘要：Au-Ti proximity is thought to be responsible for propylene epoxidation by H2 and O2 to PO formation (HOPO). However, we find that the Ti sites intimate with Au accounts for small proportion relative to Ti sites remote from Au, based on the semi-quantification of the number of Au nanoparticles and Ti sites on the uncalcined TS-1-supported Au nanoparticle (Au/TS-1-B) catalysts. Whether those remote Ti sites are functioning in PO generation remains unclear. Herein, the abundant remote Ti sites are proposed to catalyze PO formation by the tandem mechanism with the help from the migration of active oxidant species. We isolated the Au sites and Ti sites by physically mixing uncalcined silicalite-1-supported Au (Au/S-1-B) and TS-1-B as a tandem catalyst with much less Au-Ti proximity sites. Comparable performance for HOPO of the mixed catalyst was observed relative to the Au/TS-1-B catalyst, suggesting that the tandem mechanism is also responsible for PO formation. The H2/D2 exchange experiment, in situ diffuse reflectance infrared Fourier transform spectroscopy, and kinetic modeling were combined to further elucidate the mechanism. Only the kinetic model including both the tandem mechanism on remote Ti sites and the simultaneous mechanism on the Au-Ti proximity can well describe the experimental results, and the tandem mechanisms have a larger contribution to PO formation than the simultaneous mechanism on the Au/TS-1-B catalyst with Au nanoparticles on the external surface. However, for the Au/TS-1 catalyst with intraporous tiny Au clusters, the PO formation proceeds by the simultaneous mechanism. This work unveils the function of remote Ti sites in PO formation. Moreover, the kinetic behaviors are connected with the catalyst structure (micropore volume and Au location), which can provide guidance for enhancing the catalytic performance by designing efficient tandem catalysts for the HOPO process.