胺功能化MIL-101(Cr)@SiO_2@Fe_3O_4催化剂及其Knoevenagel反应性能

Catalytic performance of amines functionalized MIL-101(Cr)@SiO_2@Fe_3O_4 catalysts for Knoevenagel reaction

采用溶剂热法在纳米SiO_2@Fe_3O_4磁性颗粒表面原位合成MIL-101(Cr),制备磁性MIL-101(Cr)@SiO_2@Fe_3O_4催化剂。采用甲胺、乙二胺和丁二胺对制备的磁性催化剂进行功能化,得到胺功能化NH2-MIL-101(Cr)@SiO_2@Fe_3O_4催化剂。利用XRD、FT-IR、BET、SEM、TEM和VSM等对催化剂结构进行表征,评价胺功能化NH2-MIL-101(Cr)@SiO_2@Fe_3O_4催化剂对糠醛和氰乙酸乙酯Knoevenagel缩合反应性能和重复使用性能,考察反应条件与催化性能的关系。结果表明,制备的新型胺功能化NH2-MIL-101(Cr)@SiO_2@Fe_3O_4催化剂具有MIL-101(Cr)的结构特征和良好的超顺磁性能,对糠醛和氰乙酸乙酯Knoevenagel缩合反应表现出很好的催化性能,其中,乙二胺功能化30%MIL-101(Cr)@SiO_2@Fe_3O_4催化剂对Knoevenagel缩合反应的性能最佳,在反应温度40℃和反应时间1 h条件下,氰乙酸乙酯转化率为97. 0%,产物选择性接近100%。反应后磁性催化剂可以通过外磁场容易进行分离,重复使用5次,氰乙酸乙酯转化率仍大于93%。

The magnetically MIL-101(Cr)@SiO2@Fe3O4 catalysts with different MIL-101(Cr) contents were synthesized using in situ method of encapsulating MIL-101(Cr) on magneticSiO2@Fe3O4 nanoparticles surface. Then methylamine,ethylenediamine and butanediamine were used as functional groups for MIL-101(Cr)@SiO2@Fe3O4 and novel NH2-MIL-101(Cr)@ SiO2@Fe3O4 catalysts were prepared. Structure of the catalysts was characterized by XRD,FT-IR,BET,SEM,TEM and VSM techniques. Catalytic performance and recovery properties of the catalysts for the Knoevenagel reaction of furfural with ethyl cyanoacetate were evaluated. The relationship of reaction conditions and catalytic perform-ance were also investigated. The results showed that all three amines functionalized catalysts had the structure of MIL-101(Cr) and good superparamagnetism. The magnetic NH2-MIL-101(Cr)@ SiO2@Fe3O4 catalysts exhibited well catalytic performance for the Knoevenagel reaction of furfural with ethyl cyanoacetate. Among them,the 30% MIL-101(Cr)@SiO2@Fe3O4 catalyst was the best one. Conversion of ethyl cyanoacetate could reach 97. 0% and selectivity of product could reach ~ 100% at reaction temperature of40 ℃ and 1 h reaction time. After reaction,the catalysts could be easily separated from the reaction mixture by an external magnet. The recovery catalyst could be reused for five times,and conversion of ethyl cyanoacetate kept over 93%.