高朋召1,2,吴迪1,郑航博1,陈会会1,张佩1.有机胺改性对ZIF-8催化 Knoevenagel缩合反应活性的影响[J].湖南大学学报:自然科学版,2020,(8):124~132
有机胺改性对ZIF-8催化 Knoevenagel缩合反应活性的影响
Effect of Amine Modification on Catalytic Activity of ZIF-8 in Knoevenagel Condensation Reaction
  
DOI:
中文关键词:  ZIF-8  Knoevenagel缩合反应  胺改性  机理  催化
英文关键词:ZIF-8  Knoevenagel condensation reaction  amine modification  mechanism  catalysis
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作者单位
高朋召1,2,吴迪1,郑航博1,陈会会1,张佩1 (1. 湖南大学 材料科学与工程学院湖南 长沙 410082 2. 湖南大学 喷射沉积技术及应用湖南省重点实验室湖南 长沙 410082) 
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中文摘要:
      采用不同结构的有机胺改性溶剂热法合成ZIF-8催化剂,探讨胺结构特性对ZIF-8催化Knoevenagel缩合反应活性的影响. 结果表明,有机胺改性后ZIF-8保持菱形十二面体结构,形貌规则与未改性材料无明显差别,1,2丙二胺、二乙烯三胺和三乙烯四胺改性ZIF-8后的BET比表面积分别为1 893 m2·g-1、1 885 m2·g-1和1 861 m2·g-1,较改性前下降约6.5 %,这主要是由于接枝在ZIF-8表面的有机胺堵塞了其孔道;采用乙醇作溶剂,催化剂添加量(摩尔分数)为0.6%(相对于苯甲醛用量),反应温度80 ℃,210 min时,1,2丙二胺改性ZIF-8对Knoevenagel反应的催化活性最高,α-氰基肉桂酸乙酯的产率达97.8%,循环10次后,产率依旧保持90 %以上,较未改性催化剂产率提高35.3 %. 对胺改性ZIF-8的催化机理研究表明:有机胺改性ZIF-8可增加其催化活性位点,而1,2丙二胺因链短,空间位阻小,其N活性位点更易与反应物接触,与ZIF-8上原有的咪唑N位点一起通过孤对电子与反应物苯甲醛的亚甲基上的 -H配位,从而显著提高催化剂的活性.
英文摘要:
      In this paper, different kinds of organic amines were used to modify ZIF-8 catalysts prepared via solvothermal method,and the effects of organic amine structural characteristics on the catalytic activity of ZIF-8 for Knoevenagel condensation reaction were discussed. The results show that ZIF-8 modified by organic amine still maintains the rhombohedral dodecahedron structure and possesses regular morphology,without obvious difference from that of unmodified materials. The BET specific surface areas of ZIF-8 modified by 1,2-propylenediamine,diethylenetriamine and triethylenetetramine are 1 893 m2·g-1,1 885 m2·g-1 and 1 861 m2·g-1,respectively, decreased by about 6.5% compared with that of the unmodified materials, mainly due to the blockage of pores for ZIF-8 by organic amines. When ethanol works as solvent, the amount of catalyst is 0.6 mol%(molar ratio to benzaldehyde),the reaction temperature is 80 ℃. When the reaction time keeps for 210 min,1,2-propanediamine modified ZIF-8 exhibits the highest catalyst activity,and the yield of ethyl α-cyanocinnamate reaches 97.8 %. After 10 cycles,the yield of this reaction is still up to 90 %,an increase of 35.3 % higher than that of unmodified ZIF-8. The studies on the catalytic mechanism of amine-modified ZIF-8 indicate that amines modified ZIF-8 can improve the amount of activity site,while 1,2-propanediamine has a shorter chain and less steric hindrance, making its N sites easier contact with reactants. It combines with the original imidazole N site on ZIF-8 to coordinate with α-H on the methylene of benzaldehyde through lone pair electrons, therefore significantly improving the catalytic activity of the catalyst clearly.
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