CIESC Journal ›› 2018, Vol. 69 ›› Issue (2): 690-698.DOI: 10.11949/j.issn.0438-1157.20170995

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Activation atmospheres on structure-performance relationship of K-promoted Fe catalysts for lower olefin synthesis from CO2 hydrogenation

ZHANG Yulong, SHAO Guangyin, ZHANG Zhengpai, LIU Xianglin, ZHANG Chao, XU Jing, HAN Yifan   

  1. Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
  • Received:2017-07-28 Revised:2017-10-11 Online:2018-02-05 Published:2018-02-05
  • Supported by:

    supported by the National Natural Science Foundation of China (21576084, 91534127).

活化气氛对CO2加氢制取低碳烯烃Fe-K催化剂构-效关系

张玉龙, 邵光印, 张征湃, 刘向林, 张超, 徐晶, 韩一帆   

  1. 化学工程联合国家重点实验室, 华东理工大学, 上海 200237
  • 通讯作者: 徐晶
  • 基金资助:

    国家自然科学基金项目(21576084,91534127)。

Abstract:

Lower olefins synthesis from direct CO2 hydrogenation over Fe-based catalysts is an important process of CO2 utilization. Iron catalysts with different K loading (1%, 3%, 5%, 7% and 9%) prepared by thermal decomposition were used in CO2 hydrogenation. Fe95-K5 (95%Fe-5%K,mass fraction) catalyst showed the highest activity and C2-C4 olefin selectivity. Further enhancement on Fe95-K5 catalytic performance was achieved by pre-treatment under three different activation atmospheres (10%H2/Ar, 10%CO/Ar, 5%CO/5%H2/Ar) prior to CO2 hydrogenation. 10%CO/Ar-activated catalyst showed the highest C2-C4 olefin selectivity (38.1%) and chain growth probability (α=0.644). In addition, the structure evolution of Fe95-K5 during activation and CO2 hydrogenation was characterized by X-rays diffraction (XRD), Raman and temperature-programmed hydrogenation (TPH) techniques. CO introduction in pretreat process accelerated formation of iron carbides. γ1-iron carbide was formed after pretreating in 10%CO/Ar and 5%CO/5%H2/Ar, while γ2-iron carbide was produced in the hydrogenation reaction after pretreating in 10%H2/Ar. Both carbides could promote CO2 dissociation on catalyst surface.

Key words: CO2 hydrogenation, Fe-K, activation atmospheres, lower olefins, structure-performance relationship

摘要:

CO2加氢直接制取低碳烯烃是实现其资源化利用的重要途径。通过热分解法制备了5种不同K含量(1%、3%、5%、7%、9%)的Fe-K催化剂用于CO2加氢反应,结果表明Fe95-K5(95% Fe-5% K,质量分数)催化剂具有最优的活性及C2~C4烯烃选择性;随后对Fe95-K5催化剂进行了10% H2/Ar、10% CO/Ar及5% CO/5% H2/Ar 3种不同气氛活化处理以及CO2加氢反应。结果发现,10% CO/Ar活化的催化剂具有最高的C2~C4烯烃选择性(38.1%)及链增长能力(α=0.644)。此外,还通过X射线衍射、Raman、程序升温等表征技术揭示了催化剂在不同活化气氛下的结构演变历程。研究发现,10% CO/Ar与5% CO/5% H2/Ar活化的催化剂会生成γ1型碳化铁结构,而10% H2/Ar活化的催化剂则会在反应过程中生成γ2型碳化铁结构,两种碳化铁结构对CO2解离均有促进作用。

关键词: CO2加氢, Fe-K催化剂, 活化气氛, 低碳烯烃, 构-效关系

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