文献类型：期刊文献

英文题名：Beyond the Reverse Horiuti-Polanyi Mechanism in Propane Dehydrogenation over Pt Catalysts

作者：Xiao, Ling[1];Shan, Yu-Ling[1];Sui, Zhi-Jun[1];Chen, De[2];Zhou, Xing-Gui[1];Yuan, Wei-Kang[1];Zhu, Yi-An[1]

机构：[1]East China Univ Sci & Technol, Sch Chem Engn, State Key Lab Chem Engn, UNILAB, Shanghai 200237, Peoples R China;[2]Norwegian Univ Sci & Technol, Dept Chem Engn, N-7491 Trondheim, Norway

年份：2020

卷号：10

期号：24

起止页码：14887

外文期刊名：ACS CATALYSIS

收录：;EI(收录号：20205109651480);WOS:【SCI-EXPANDED(收录号:WOS:000608850500045)】；

基金：This work is supported by the Natural Science Foundation of China (nos. 91645122, 22073027, and U1663221), the Natural Science Foundation of Shanghai (no. 20ZR1415800), the National Key Research and Development Program of China (no. 2018YFB0604700), and the Fundamental Research Funds for the Central Universities (no. 222201718003). The computational time provided by the Notur project is highly acknowledged.

语种：英文

外文关键词：dehydrogenation mechanism; platinum; microkinetic analysis; DFT; adsorbate-adsorbate interactions

摘要：The catalytic dehydrogenation of light alkanes over Pt catalysts is generally accepted to follow a reverse Horiuti-Polanyi mechanism. Using a microkinetic analysis in combination with results from density functional theory calculations, we show that although propane dehydrogenation (PDH) occurs by two successive dehydrogenation steps on terraces, an unexpected non-reverse Horiuti-Polanyi mechanism accounts for more than half the propylene production at the under-coordinated active sites that dominate the kinetics of PDH. The main reaction is composed of three dehydrogenation steps that have two beta-H atoms and one alpha-H atom removed from propane, followed by the hydrogenation of CH3CCH2; starting from this species, the formation of propylene and byproducts proceed by way of two parallel competing reactions. The proposed mechanism has been verified by exploring several key and general aspects of the kinetic behavior observed in the dehydrogenation of light alkanes, and it is found that only when adsorbate-adsorbate interactions are taken into consideration can the experimentally determined kinetics be properly reproduced. Increasing the H-2 partial pressure from low values favors an increase in the coverage of free sites due to the gasification of adsorbed coke precursors, which in turn gives rise to lowered energy barriers for C-H bond breaking, thereby achieving an increased propane consumption rate. As the H-2/C3H8 ratio increases, the rate of propylene production first goes up and then declines, and a maximum is observed at a H-2/C3H8 ratio of 1.33, which occurs when the negative effect of the increased free 4-fold hollow sites that bring about deep dehydrogenation begins to dominate the positive effect of the increased free step sites that are responsible for activating propane. The mechanism formulated here proves to be valid even if the temperature, pressure, or the H-2/C3H8 ratio is varied and hence provides a foundation for the rational design of metal and alloy catalysts for light alkane dehydrogenation.