Chinese Journal of Magnetic Resonance ›› 2022, Vol. 39 ›› Issue (2): 133-143.doi: 10.11938/cjmr20212952

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1, 3-Butadienen Hydrogenation on Supported Pd-Sn Bimetallic Catalysts Investigated by Parahydrogen-induced Polarization

Han HU1,2,Wei-yu WANG1,Jun XU1,*(),Feng DENG1   

  1. 1. State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
    2. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2021-10-29 Online:2022-06-05 Published:2022-05-28
  • Contact: Jun XU E-mail:xujun@wipm.ac.cn

Abstract:

The selective hydrogenation of 1, 3-butadiene over Pd-Sn/Al2O3 bimetallic catalysts was investigated by heterogeneous parahydrogen-induced polarization (PHIP). A series of Pd1-Snx/Al2O3 bimetallic catalysts with different Pd/Sn ratios were synthesized by incipient wetness co-impregnation method. It was observed that the Pd/Sn ratios of the catalysts had a significant effect on the reaction activity of 1, 3-butadiene and the selectivity to butene. A monotonic decrease of reaction conversion was observed as the Pd/Sn ratio decreased, while the selectivity to butene showed an opposite trend. This can be attributed to the ensemble effect and the ligand effect caused by the increasing tin component content: as the Pd/Sn ratio decreases, less palladium component was exposed on the surface, leading to low activity. The electronic properties of the Pd atoms were altered, which led to a weaker adsorption strength of the semi-hydrogenation product butene and an increased selectivity. Smaller Pd ensembles were exposed on Sn-rich catalysts surface, which favored a higher ratio of pairwise addition process, leading to a stronger PHIP effect. The isomerization measurements by PASADENA (parahydrogen and synthesis allow for dramatically enhanced nuclear alignment) showed that the isomerization process between 1-butene and 2-butene decreased with the increase of Sn content. This can be accounted for by the easier desorption of 1-butene on Sn-rich catalysts.

Key words: 1,3-butadiene hydrogenation, bimetallic catalyst, nuclear magnetic resonance (NMR), isomerization process, parahydrogen-induced polarization (PHIP)

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