Chinese Journal of Catalysis ›› 2025, Vol. 74: 167-176.DOI: 10.1016/S1872-2067(25)64694-8

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A spatial-resolved online MS study on OCM reaction catalyzed by Mn-Na2WO4/SiO2 system for radicals coupling mechanistic insight

Ningxujin Dinga, Danyu Wanga, Shihui Zoub, Jie Fanb, Lyubov Alexandrovna Isupovac, Junyu Langa,*(), Yong Yanga,d,*()   

  1. aSchool of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
    bKey Laboratory of Applied Chemistry of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310036, Zhejiang, China
    cBoreskov Institute of Catalysis SB RAS, Lavrentiev Ave. 5, Novosibirsk 630090, Russia
    dShanghai Key Laboratory of High-resolution Electron Microscopy, ShanghaiTech University, Shanghai 201210, China
  • Received:2025-01-07 Accepted:2025-03-18 Online:2025-07-18 Published:2025-07-20
  • Contact: *E-mail: yangyong@shanghaitech.edu.cn (Y. Yang), langjy@shanghaitech.edu.cn (J. Lang).
  • Supported by:
    Ministry of Science and Technology of National Key R&D Program of China(2023YFB4005200);National Natural Science Foundation of China(22272107);National Natural Science Foundation of China(22072092);Analytical Instrumentation Center(SPST-AIC10112914);HPC Platform of ShanghaiTech University;Shanghai Key Laboratory of High-resolution Electron Microscopy (Shanghai Science and Technology Plan, No. 21DZ2260400), SPST, ShanghaiTech University

Abstract:

Oxidative coupling of methane (OCM) is a catalytic partial oxidation process that directly converts methane into C2 products. For this high temperature reaction, understanding the radical behavior through experimental investigation is important in correlating the catalytic activity and the products. In this work, a spatial resolution online mass spectrometry (MS) system was developed and applied to a Mn-Na2WO4/SiO2 catalyzed OCM system. In addition to the residue gas analysis, the system obtained the distribution information of the reactants and products in the reactor. At various setting temperatures, all species online MS signals were collected at different positions, mapping the reaction activity covering parameters including temperature, time and space. The distribution behavior of the catalytic activity, selectivity, and apparent activation energy were kinetically analyzed. Selectivity and additional carbon balance analysis strongly supported the radical coupling model of OCM and indicated that after the catalytic bed layer, there is a significant length in the reactor (> 2 mm) filled with radicals. Based on the result, a designed new method by tuning the temperature field in the reactor was found effectively to improve the catalytic activity, especially the C2 yield from 702 to 773 °C.

Key words: Oxidative coupling of methane, Mn-Na2WO4/SiO2 catalyst, Online mass spectrometry, Spatial-resolved kinetic analysis, Radical coupling model