Chinese Journal of Catalysis ›› 2016, Vol. 37 ›› Issue (8): 1413-1422.DOI: 10.1016/S1872-2067(16)62466-X

• Articles • Previous Articles     Next Articles

Changing the balance of the MTO reaction dual-cycle mechanism: Reactions over ZSM-5 with varying contact times

Mozhi Zhanga,c, Shutao Xua, Yingxu Weia, Jinzhe Lia, Jinbang Wanga, Wenna Zhanga,c, Shushu Gaoa,c, Zhongmin Liua,b   

  1. a. National Engineering Laboratory for Methanol to Olefins, Dalian National Laboratory for Clean Energy, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China;
    b. State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China;
    c. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2016-05-04 Revised:2016-05-17 Online:2016-07-29 Published:2016-08-01
  • Contact: Zhongmin Liu, Yingxu Wei
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (91545104, 21576256, 21473182, 21273230, 21273005) and the Youth Innovation Promotion Association of the Chinese Academy of Sciences.

Abstract:

The methanol to olefins (MTO) reaction was performed over ZSM-5 zeolite at 300 ℃ under various methanol weight hourly space velocity (WHSV) values. During these trials, the catalytic performance was assessed, in addition to the formation and function of organic compounds retained in the zeolite. Analysis of reaction effluents and confined organics demonstrated a dual-cycle reaction mechanism when employing ZSM-5. The extent of the hydrogen transfer reaction, a secondary reaction in the MTO process, varied as the catalyst-methanol contact time was changed. In addition, 12C/13C-methanol switch experiments indicated a relationship between the dual-cycle mechanism and the extent of the hydrogen transfer reaction. Reactions employing a low methanol WHSV in conjunction with a long contact time favored the hydrogen transfer reaction to give alkene products and promoted the generation and accumulation of retained organic species, such as aromatics and methylcyclopentadienes, which enhance the aromatic cycle. When using higher WHSV values, the reduced contact times lessened the extent of the hydrogen transfer reaction and limited the generation of methylcyclopentadienes and aromatic species. This suppressed the aromatic cycle, such that the alkene cycle became the dominant route during the MTO reaction.

Key words: Methanol to olefins, Dual-cycle mechanism, ZSM-5, Contact time, Hydrogen transfer reaction