Chem. J. Chinese Universities ›› 2024, Vol. 45 ›› Issue (9): 20240174.doi: 10.7503/cjcu20240174

• Physical Chemistry • Previous Articles     Next Articles

Catalytic Behavior of Different Amounts of WO4 Active Sites on Na-W-Mn/SiO2 Catalysts for Oxidative Coupling of Methane

SONG Jiaxin1,2, FAN Xiaoqiang2(), LIU Baijun1(), ZHAO Zhen1,2()   

  1. 1.State Key Laboratory of Heavy Oil Processing,China University of Petroleum,Beijing 102249,China
    2.Institute of Catalysis for Energy and Environment,College of Chemistry and Chemical Engineering,Shenyang Normal University,Shenyang 110034,China
  • Received:2024-04-10 Online:2024-09-10 Published:2024-07-30
  • Contact: FAN Xiaoqiang, LIU Baijun, ZHAO Zhen E-mail:fanxiaoqiang1986@126.com;bjliu@cup.edu.cn;zhaozhen1586@163.com
  • Supported by:
    the National Natural Science Foundation of China(22172101);the Liaoning Province Applied Basic Research Program of China(2023JH2/101600059);the Science and Technology Planning Project of Shenyang of China(22-322-3-28);the Liaoning Xingliao Talented Youth Top Talent Program of China(XLYC2203138);the Major Incubation Program of Shenyang Normal University of China(ZD201901)

Abstract:

Oxidative coupling of methane(OCM) served as a direct pathway for producing C2(C2H6 and C2H4) has received widespread attention. Among the conventional catalysts, Mn/Na2WO4/SiO2(Na-W-Mn/SiO2) catalysts have many advantages like: high methane conversion, high C2 selectivity, and relatively high stability even at high temperature. In this work, a series of Na-nW-Mn/SiO2 catalysts with different W loadings were prepared using silicotungstic acid as the precursor. In order to further investigate the effects of W loadings on the structure and OCM performance of the catalysts, X-ray diffraction(XRD), transmission electron microscopy(TEM), hydrogen temperature programmed reduction(H2-TPR), oxygen temperature programmed desorption(O2-TPD), and X-ray photoelectron spectra(XPS) characterizations and the activity evaluation for oxidative coupling of methane were performed on all samples. The results demondtrated that there is a strong interaction among the crystal phases of Na2WO4, Mn2O3 and α-cristobalite, which enhances the OCM performance of these catalysts through synergistic catalysis. It is interesting that with the continuous increase of W loading, the W species maintained the form of tetrahedral WO4 on the surface of catalysts. Structure-activity relationship analysis shows that tetrahedral WO4 is the active center for the OCM reaction on this series of catalysts. Therefore, the Na-10.0%W-Mn/SiO2 catalyst with high tetrahedral WO4 content has a lower reduction temperature from W6+→W4+ and a higher proportion of surface lattice oxygen, which may be the main reason for its optimal methane conversion and C2 yield. When the temperature reached 775 ℃, the conversion of methane over Na-10.0%W-Mn/SiO2 catalyst is 44.2%, the yield of C2 is 24.1%, and the yield of ethylene is 18.7%.

Key words: Na-W-Mn/SiO2 catalyst, Oxidative coupling of methane, Different W contents, Yield of ethylene, C2

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