Acta Phys. -Chim. Sin. ›› 2017, Vol. 33 ›› Issue (8): 1689-1698.doi: 10.3866/PKU.WHXB201704243

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Preparation and Characterization of Sinter-Resistant Rh-Sm2O3/SiO2 Catalyst and Its Performance for Partial Oxidation of Methane to Syngas

Fang-Fang ZHENG,Qian LI,Hong ZHANG,Wei-Zheng WENG*(),Xiao-Dong YI,Yan-Ping ZHENG,Chuan-Jing HUANG,Hui-Lin WAN*()   

  • Received:2017-02-21 Published:2017-06-14
  • Contact: Wei-Zheng WENG,Hui-Lin WAN E-mail:wzweng@xmu.edu.cn;hlwan@xmu.edu.cn
  • Supported by:
    The project was supported by the National Key Basic Research Program of China(2013CB933102);National Natural Science Foundation of China(21473144);National Natural Science Foundation of China(21373168);National Talent Development of Basic Research Program of China(J1310024);Program for Innovative Research Team in University, China(IRT_14R31)

Abstract:

Rh/SiO2 and Rh-Sm2O3/SiO2 catalysts were synthesized by the conventional impregnation method using rhodium acetylacetonate (Rh(acac)3) and samarium acetylacetonate (Sm(acac)3) as precursors. The preparation and catalytic properties, as well as the interaction between Rh and Sm2O3, were characterized in detail by in situ infrared spectroscopy (IR), thermogravimetric analysis (TG), N2 physisorption (Brunauer-Emmett-Teller (BET) method), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The performance of the catalysts for the partial oxidation of methane (POM) to syngas was also investigated. The results showed that a sinter-resistant Rh-Sm2O3/SiO2 catalyst with an average Rh particle size of ~2.3 nm could be synthesized using the conventional impregnation method with Rh(acac)3 and Sm(acac)3 as precursors. The surface silanol groups of SiO2 acted as the centers to interact with M(acac)3 (M=Rh, Sm) molecules when SiO2 was impregnated in the M(acac)3 solution, leading to the formation of a hydrogen-bonded M(acac)3 layer on the SiO2 surface. In this experiment, the monolayer coverage of Sm(acac)3 on the SiO2 surface was equal to a Sm(acac)3 loading (mass fraction) of approximately 31%, which in turn corresponded to a Sm2O3 loading of approximately 15%. When a Sm(acac)3/SiO2 sample with Sm(acac)3 loading below 31% was heated in air to approximately 360℃, the monolayer Sm(acac)3 species decomposed into highly dispersed Sm2O3 species on the SiO2 surface, which displayed superior stability against sintering at high temperature. No aggregation of the Sm2O3 species was observed even when the sample was heated to 800℃ in air. The strong interaction between the highly dispersed Sm2O3 and Rh plays a key role in increasing the dispersion of Rh species in the catalyst and preventing the Rh species from sintering under high temperature conditions. This factor should also be responsible for the superior activity and stability of the Rh-Sm2O3/SiO2 catalyst with extremely low Rh loading for the catalytic partial oxidation of methane to syngas.

Key words: Rh-Sm2O3/SiO2, Rh(acac)3, Sm(acac)3, Sinter-resistant, Partial oxidation of methane, Syngas

MSC2000: 

  • O643