Mechanistic study of propane selective oxidation with H2 and O2 on Au/TS-1

被引:53
作者
Bravo-Suarez, Juan J. [2 ]
Bando, Kyoko K. [2 ]
Fujitani, Tadahiro [2 ]
Oyama, S. Ted [1 ,2 ]
机构
[1] Virginia Polytech Inst & State Univ, Dept Chem Engn 0211, Environm Catalysis & Nanomat Lab, Blacksburg, VA 24061 USA
[2] Natl Inst Adv Ind Sci & Technol, Res Inst Innovat Sustainable Chem, Tsukuba, Ibaraki 3058569, Japan
基金
美国国家科学基金会; 日本学术振兴会;
关键词
gold; TS-1; propane; acetone; 2-propanol; kinetics; ultraviolet-visible spectroscopy; X-ray absorption near edge spectroscopy; true intermediate; oxidation;
D O I
10.1016/j.jcat.2008.04.004
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The selective oxidation of propane to acetone and 2-propanol with H-2 and O-2 was studied on Au/TS-1 by kinetic and spectroscopic analysis. A kinetic study using a factorial design at conditions where the catalyst was stable and gave propane conversions of < 6% and combined oxygenates selectivity of > 90%, resulted in a power-rate law expression of the form roxyg(center dot) = kroxyg(center dot)(H-2)(0.74)(O-2)(0.36)(C3H8)(0.29). In situ Au L-3-edge X-ray absorption near-edge spectroscopy (XANES) measurements showed activation of 02 on Au, whereas in situ ultraviolet-visible (UV-vis) spectroscopy evidenced the presence of Ti-hydroperoxo species. The role of the Ti-hydroperoxo species was probed by a transient technique in which changes in Ti K-edge XANES spectra were used to determine the evolution of coverage with time (d theta/dt). It was shown that the rate of reaction by XANES (6.7 x 10(-4) s(-1)) was close to the turnover rate measured in a catalytic flow reactor (5.6 x 10(-4) s(-1)), indicating that the hydroperoxci species were true intermediates in the reaction. A proposed reaction sequence in which H2O2 forms on Au sites and propane is partially oxidized on Ti centers accounts for the spectroscopic results and the reaction orders obtained experimentally for the power-rate law expression. (c) 2008 Elsevier Inc. All rights reserved.
引用
收藏
页码:32 / 42
页数:11
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