高等学校化学学报 ›› 2019, Vol. 40 ›› Issue (7): 1510-1519.doi: 10.7503/cjcu20180790

• 物理化学 • 上一篇    下一篇

反应过程中Cu物种演变对其催化甲醇氧化羰基化反应活性的影响

尹娇, 张国强(), 阎立飞, 贾东森, 郑华艳, 李忠()   

  1. 太原理工大学煤科学与技术教育部和山西省重点实验室, 太原 030024
  • 收稿日期:2018-11-21 出版日期:2019-07-10 发布日期:2019-07-12
  • 作者简介:李 忠, 男, 博士, 教授, 博士生导师, 主要从事多相催化研究. E-mail: lizhong@tyut.edu.cn;张国强, 男, 博士, 讲师, 主要从事甲醇高效转化研究. E-mail: zgq198615@163.com
  • 基金资助:
    国家自然科学基金(批准号: U1510203, 21276169)和山西省自然科学基金(批准号: 201701D221043)资助.

Influence of Structure Evolution of CuY Catalyst During the Reaction Process on Its Catalytic Performance for Oxidative Carbonylation of Methanol

YIN Jiao, ZHANG Guoqiang*(), YAN Lifei, JIA Dongsen, ZHENG Huayan, LI Zhong*()   

  1. Key Laboratory of Coal Science and Technology, Ministry of Education and Shanxi Province,Taiyuan University of Technology, Taiyuan 030024, China
  • Received:2018-11-21 Online:2019-07-10 Published:2019-07-12
  • Contact: ZHANG Guoqiang,LI Zhong E-mail:zgq198615@163.com;lizhong@tyut.edu.cn
  • Supported by:
    † Supported by the National Natural Science Foundation of China(Nos.U1510203, 21276169) and the Natural Science Foundation for Shanxi Province, China(No.201701D221043).

摘要:

以NH4Y分子筛为载体、 乙酰丙酮铜为铜源, 采用固相反应法制备了无氯CuY催化剂, 并用于催化甲醇氧化羰基化合成碳酸二甲酯(DMC). 结合不同反应时间催化剂的X射线衍射(XRD)、 N2吸附-脱附、 热重(TG)、 程序升温脱附/还原(NH3-TPD/H2-TPR)、 透射电子显微镜(TEM)和X射线光电子能谱(XPS)等表征结果, 分析了反应过程中Cu物种演变对其催化活性的影响. 结果表明, 新鲜催化剂中铜物种主要以Cu+形式存在, 占铜物种的48%; 随着反应的进行, 活性中心Cu+逐渐被氧化为Cu2+, 进而生成CuO物种, 部分CuO逐渐迁移至催化剂外表面. 在反应100 h内, Cu+含量逐渐减小至36.7%, CuO含量增加, 导致DMC的时空收率及选择性不断下降, 副产物二甲氧基甲烷(DMM)和甲酸甲酯(MF)的选择性逐渐提高. 当反应时间延长至190 h时, Cu+含量为33.6%, 略有下降, DMC的时空收率和选择性趋于平稳. 继续延长反应时间至300 h, 催化剂中铜物种状态基本不变, 催化剂催化性能保持稳定.

关键词: 甲醇氧化羰基化, 碳酸二甲酯, CuY催化剂, 铜物种, 价态变化

Abstract:

Chloride-free CuY catalyst prepared by solid state reaction with NH4Y zeolites as support and copper acetylacetone as copper source was evaluated for oxidative carbonylation of methanol to dimethyl carbonate(DMC). Combining the results of X-ray diffraction(XRD), N2 adsorption-desorption isotherm, thermogravimetric(TG) analysis, NH3-temperature-programmed desorption(NH3-TPD), transmission electroon microscopy(TEM) and X-ray photoelectron spectroscopy(XPS) characterization, the influence of copper species evolution during the reaction process on its catalytic performance was disclosed. The results indicated that Cu+ was the dominant Cu species of fresh catalyst with the percentage of 48%. As the reaction proceeded, the active center Cu+ was gradually oxidized to Cu2+, and then formed CuO, part of which gradually migrated to the outer surface of the catalyst. With the reaction time extended to 100 h, the percentage of Cu+ gradually decreased to 36.7%, while the percentage of CuO continued to increase, accordingly resulting in the decrease of the space-time yield and selectivity of DMC and the increase of the selectivity of byproducts dimethoxymethane(DMM) and methyl formate(MF). With the reaction time extended to 190 h, the percentage of Cu+ decreased slowly to 33.6%, the space time yield and selectivity of DMC tended to be stable. When the reaction time extended to 300 h, the copper species in the catalyst remained unchanged, and the catalytic performance of the catalyst remained stable.

Key words: Oxidative carbonylation of methanol, Dimethyl carbonate, CuY catalyst, Copper species, Valence variation

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