Chinese Journal of Catalysis ›› 2024, Vol. 61: 154-163.DOI: 10.1016/S1872-2067(24)60036-7

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Understanding the correlation between zinc speciation and coupling conversion of CO2 and n-butane on zinc/ZSM-5 catalysts

Xuke Suna,b, Rongsheng Liua, Gaili Fana,c, Yuhan Liua,d, Fangxiu Yea,b, Zhengxi Yua,*(), Zhongmin Liua,b,*()   

  1. aNational Engineering Research Center of Lower-Carbon Catalysis Technology, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China
    bUniversity of Chinese Academy of Sciences, Beijing 100049, China
    cSchool of Chemistry, Dalian University of Technology, Dalian 116024, Liaoning, China
    dCollege of Chemistry and Chemical Engineering, China University of Petroleum (East China), Qingdao 266580, Shandong, China
  • Received:2024-03-05 Accepted:2024-04-10 Online:2024-06-18 Published:2024-06-20
  • Contact: * E-mail: zhengxiyu@dicp.ac.cn (Z. Yu), liuzm@dicp.ac.cn (Z. Liu).
  • Supported by:
    National Natural Science Foundation of China(21991093);National Natural Science Foundation of China(21991092);National Natural Science Foundation of China(21991090);National Key Research and Development Program of China(2022YFE0116000);Strategic Priority Research Program of the Chinese Academy of Sciences(XDA29000000)

Abstract:

The coupling reaction of alkanes and CO2 into high value-added bulk chemical products is a promising way for CO2 utilization. The Zn-introduced ZSM-5 catalyst plays an essential role in this process; however, the correlation between the catalytic performance and Zn species of the catalyst has yet to be established. Herein, the structural properties, the acid sites, and the existence status of the Zn species in the Zn-introduced catalysts were systematically characterized by several techniques. And the influence of the state of Zn species in the coupling reaction was discussed. The results indicate that the Zn species exist in the form of ZnO cluster, Zn-OH+, and (Zn-O-Zn)2+ species, thereinto (Zn-O-Zn)2+ species are produced by the Zn-OH+ group with the increasing Zn loading. The decrease of Brønsted acid sites, the formation of newly active sites caused by Zn species, and the accumulation of coarse ZnO species, are responsible for the change of n-butane conversion. The Zn-OH+ group serves as the primary catalytic center for the conversion of CO2. Both the Zn-OH+ group and the (Zn-O-Zn)2+ species enhance the dehydrogenation performance of the Zn-introduced catalysts, thereby promoting the generation of aromatics. The Zn5%-ZSM-5 sample showed the most excellent catalytic performance; the n-butane conversion was 94.71%, the CO2 conversion was 30.43%, and the aromatics selectivity was 53.71%. Simultaneously, we propose a more specific mechanism for the coupling reaction.

Key words: Coupling reaction, CO2 utilization, Zn-introduced, Zn-OH+, (Zn-O-Zn)2+, ZSM-5