Improved Stability of Ptsn for Propane Dehydrogenation By Boron-Modified ZrO2 Support

Improved stability of PtSn for propane dehydrogenation by boron-modified ZrO₂ support

Zhonghai Ji, Xiulian Pan, Xinhe Bao,

State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People’s Republic of China. Email: panxl@dicp.ac.cn; xhbao@dicp.ac.cn 

PtSn based catalysts are widely used in propane dehydrogenation (PDH)^[1-5]. Since it involves noble metal, it is highly desirable to reduce the usage of Pt without degrading the catalytic performance. However, the catalyst stability is apt to deterioration with decreasing Pt content ^[1]. In this contribution, we demonstrate that the B modified ZrO₂ as a support can enhance the stability of PtSn catalyst.

Boron modified ZrO₂ (B-ZrO₂) was prepared by co-precipitation. PtSn/B-ZrO₂ and PtSn/Al₂O₃ was prepared by the incipient-wetness impregnation method. Reaction was conducted under nonoxidative conditions at 550 ^oC, weight hourly space velocity (WHSV) of propane 3 h^-1. Results in Fig. 1 show that the initial propane conversion is 32.4% for PtSn/ZrO₂, 36.0% for PtSn/B-ZrO₂ and 42.2% for PtSn/Al₂O₃. However, the propylene selectivity is lowest on PtSn/Al₂O₃. The deactivation rate constant (k_d) is 0.08 h^-1 over PtSn/ZrO₂ and 0.04 h^-1 over PtSn/Al₂O₃ whereas it is only 0.01 h^-1 over PtSn/B-ZrO₂. The stability of PtSn/B-ZrO₂ is obviously better than that of 0.35wt% PtSn/Al₂O₃ and PtSn/ZrO₂. Characterization by NH₃-TPD and pyridine IR shows that Lewis acid is present on B-ZrO₂. XPS indicates that the presence of even a small amount of boron stabilizes the oxidation state of Sn, which may play an important role. More detailed discussions will be given in the presentation.

Fig. 1 Catalytic performance in propane dehydrogenation on various catalysts.

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Int. Ed.ion, 54 (2015). 13994-13998.