刘鹏程,牛汝月,李威,王爽,李晋平.碱性CeO2载体对Ru/CeO2催化剂氨合成活性的影响[J].分子催化,2018,32(4):349-358
碱性CeO2载体对Ru/CeO2催化剂氨合成活性的影响
Effect of CeO2 Support Basicity on the Catalytic Activity of Ru/CeO2 Catalyst for Ammonia Synthesis
投稿时间:2018-06-27  修订日期:2018-07-20
DOI:
中文关键词:  稀土氧化物  氨合成  多相催化  碱性影响  钌基催化剂
英文关键词:rare earth oxides  ammonia synthesis  heterogeneous catalysis  basicity effect  Ru-based catalyst
基金项目:This work are supported by the Natural Science Foundation of China (Grant No. 21671147), Scientific and Technologial Innovation Programs of Higher Education Institutions in Shanxi, State Key Laboratory of Coal and CBM Co-mining (Grant No. 2016012004).
作者单位E-mail
刘鹏程 气体能源高效清洁利用山西省重点实验室, 山西 太原 030024  
牛汝月 气体能源高效清洁利用山西省重点实验室, 山西 太原 030024  
李威 气体能源高效清洁利用山西省重点实验室, 山西 太原 030024  
王爽 气体能源高效清洁利用山西省重点实验室, 山西 太原 030024
太原理工大学 环境科学与工程学院, 山西 晋中 030600 
wangshuang@tyut.edu.cn 
李晋平 气体能源高效清洁利用山西省重点实验室, 山西 太原 030024 jpli211@hotmail.com 
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中文摘要:
      钌基催化剂因其在低温低压下具有比常规的铁基催化剂更具活性的特点成为合成氨催化剂的理想选择.我们研究了CeO2载体表面碱性对Ru基合成氨催化剂的影响.通过调节KOH沉淀剂的量来制备具有不同碱性位点的CeO2载体(pH=10/11/12),证明了催化剂适当碱性位点密度提高了合成氨催化活性.催化性能测试结果表明,1.25% Ru/CeO2-11催化剂在3.8 MPa,450℃,H2/N2=3(60 mL·min-1)下表现出优异的氨合成活性(7040 μmol·g-1·h-1).CeO2-11的碱性位点增强了载体的电子给予能力,这有利于电子向活性金属Ru转移,从而促进了N2的活化.碱金属和碱土金属的引入提高了活性金属Ru的还原能力.4% Cs-1.25% Ru/CeO2-11(12 000 μmol·g-1·h-1)催化剂具有更多的氧空位,这增加了Ru周围的电子密度并促进了N≡N的裂解.通过XRD,BET,SEM,CO2-TPD,H2-TPR和XPS分析了不同碱性CeO2载体对合成氨催化反应的影响.
英文摘要:
      The effect of surface basicity of CeO2 on the Ru-based catalyst for ammonia synthesis was studied. The CeO2 supports (pH=10/11/12) with different amount of basic site were prepared by adjusting the amount of KOH precipitating agent to prove that appropriate basic site density of the catalyst enhanced the ammonia synthesis activity. The results of catalytic performance showed that 1.25%Ru/CeO2-11 catalyst exhibited excellent ammonia synthesis activity(7040 μmol·g-1·h-1)at 3.8 MPa,450 ℃,H2/N2=3 (60 mL·min-1). The strong basicity of the 1.25%Ru/CeO2-11 catalyst greatly influences the ammonia synthesis performance on the Ru-based catalyst. The basic site of the CeO2-11 enhanced the electron donating ability of support, facilitating the transfer of electrons to Ru. Electron-rich active metal Ru promoted the cleavage of N≡N. After acquiring the optimal synthesis pH, various alkaline modifier (M=Ba, K and Cs) was added to further modulate the catalytic performance, which increased the reducing ability of the active metal Ru. The catalytic activity of 4%Cs-1.25%Ru/CeO2-11 catalyst reached 12 000 μmol·g-1·h-1. It can be seen from the H2-TPR and XPS characterization that the 4%Cs-1.25%Ru/CeO2-11 catalyst has more oxygen vacancies, which increases the electron density around Ru and promotes the cleavage of N≡N bond. The physicochemical properties of CeO2 supports were analyzed by XRD, BET, SEM, CO2-TPD, H2-TPR and XPS.
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