催化学报

催化学报 ›› 2019, Vol. 40 ›› Issue (4): 567-579.DOI: 10.1016/S1872-2067(19)63302-4

• 论文 • 上一篇    下一篇

Ni-Re/SiO2催化剂中Ni颗粒尺寸对乙醇胺催化胺化反应的影响

马雷a,b,d, 严丽a, 陆安慧b, 丁云杰a,c   

  1. a 中国科学院大连化学物理研究所, 洁净能源国家实验室(筹), 辽宁大连 116023;
    b 大连理工大学化工学院, 精细化工国家重点实验室, 辽宁大连 116024;
    c 中国科学院大连化学物理研究所, 催化基础国家重点实验室, 辽宁大连 116023;
    d 中国科学院大学, 北京 100049
  • 收稿日期:2018-10-24 修回日期:2019-01-08 出版日期:2019-04-18 发布日期:2019-03-14
  • 通讯作者: 丁云杰, 严丽
  • 基金资助:

    国家自然科学基金（21273227）；中国科学院战略性先导科技专项（XDB17000000）.

Effects of Ni particle size on amination of monoethanolamine over Ni-Re/SiO2 catalysts

Lei Maa,b,d, Li Yana, An-Hui Lub, Yunjie Dinga,c   

  1. a Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China;
    b State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, Liaoning, China;
    c State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China;
    d University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2018-10-24 Revised:2019-01-08 Online:2019-04-18 Published:2019-03-14
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21273227) and Strategic Priority Research Program of Chinese Academy of Sciences (XDB17000000).

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摘要：

以醇和氨/胺为原料采用催化胺化法合成有机胺长期以来广受关注，该工艺反应副产物只有水，符合现代绿色化工理念.作为工业应用的成功案例，乙醇胺（MEA）催化胺化法目前已成为生产乙撑胺（包括乙二胺（EDA），哌嗪（PIP）等）的主要工艺.MEA催化胺化通常在过渡金属催化剂上进行，如Ni基催化剂，反应过程遵循"借氢机理"，经历了"脱氢-缩合胺化-加氢"三个过程.
目前，关于MEA胺化催化剂的研究主要以专利为主，据我们所知，对于催化剂金属颗粒尺寸和胺化性能之间的构效关系的研究极少，特别是对于金属粒径对胺化产物分布的影响，目前还未见报道.因此，本文的目的是合成具有不同Ni颗粒尺寸的Ni-Re/SiO2催化剂，通过滴流床反应器评价，研究颗粒尺寸对MEA胺化活性和产物分布的影响.采用控制催化剂焙烧和还原条件的方法，制备了四种不同Ni粒径的Ni-Re/SiO2催化剂；随后采用N2物理吸附，H2程序升温还原，X射线衍射，H2化学吸附，光电子能谱，红外吸收光谱等对催化剂的孔结构、还原性、粒径分布、金属Ni活性比表面、分散度、表面Ni位点类型和电子性质进行研究.MEA催化胺化反应在滴流床反应器上进行，反应条件为170℃，8.0MPa，MEA液时空速0.5h-1，NH3：MEA摩尔比10：1，H2含量2.5 mol%.
表征结果证明，成功制备了具有不同Ni粒径，且尺寸分布集中的Ni-Re/SiO2催化剂，Ni粒径分别为4.5，10.5，14.6，18.0nm.评价结果表明，Ni颗粒4.5nm的Ni-Re/SiO2催化剂具有最高的活性，MEA转化率高达85.7%，EDA和PIP收率为66.4%，优于以往专利文献所报道的值.结合表征结果分析，这是由于Ni-Re/SiO2（4.5nm）上的Ni粒径小，分散度高，因此Ni活性比表面积大，为胺化反应提供了充足的催化位点.进一步深入研究了Ni颗粒尺寸对MEA胺化反应的影响，发现随着Ni粒径增加，底物MEA的转换频率（TOF）从193h-1增加到253h-1，表明大颗粒有利于胺化反应.此外，随着粒径增加，产物中伯胺和仲胺的摩尔比从1.0增加到2.0，产物EDA的TOFEDA值由63h-1增加到119h-1，表明Ni粒径变化影响了MEA胺化反应途径和产物分布，增大粒径有利于EDA的生成，从而提高了产物中的伯：仲胺之比.实验结果证明，Ni-Re/SiO2催化剂粒径影响了颗粒表面Ni的配位环境，从而改变了表面的电子结构.增大Ni粒径可提高面位点Ni的比例和表面电子云密度，导致中间产物容易从Ni表面脱附，从而有利于促进反应初始阶段MEA与NH3的胺化，提高EDA选择性.

关键词: 颗粒尺寸效应, 乙醇胺, 胺化反应, 镍-铼/氧化硅, 转换频率

Abstract:

Ni-Re/SiO2 catalysts with controllable Ni particle sizes (4.5-18.0 nm) were synthesized to investigate the effects of the particle size on the amination of monoethanolamine (MEA). The catalysts were characterized by various techniques and evaluated for the amination reaction in a trickle bed reactor at 170℃, 8.0 MPa, and 0.5 h-1 liquid hourly space velocity of MEA (LHSVMEA) in NH3/H2 atmosphere. The Ni-Re/SiO2 catalyst with the lowest Ni particle size (4.5 nm) exhibited the highest yield (66.4%) of the desired amines (ethylenediamine (EDA) and piperazine (PIP)). The results of the analysis show that the turnover frequency of MEA increased slightly (from 193 to 253 h-1) as the Ni particle sizes of the Ni-Re/SiO2 catalysts increased from 4.5 to 18.0 nm. Moreover, the product distribution could be adjusted by varying the Ni particle size. The ratio of primary to secondary amines increased from 1.0 to 2.0 upon increasing the Ni particle size from 4.5 to 18.0 nm. Further analyses reveal that the Ni particle size influenced the electronic properties of surface Ni, which in turn affected the adsorption of MEA and the reaction pathway of MEA amination. Compared to those of small Ni particles, large particles possessed a higher proportion of high-coordinated terrace Ni sites and a higher surface electron density, which favored the amination of MEA and NH3 to form EDA.

Key words: Particle size effects, Monoethanolamine, Amination reaction, Ni-Re/SiO2, Turn over frequency