双咪唑阳离子乙酸锌低共熔溶剂催化醇解PET

Alcoholysis of PET catalyzed by bimidazolium cationic zinc acetate deep eutectic solvent

本文设计合成了具有高热稳定性、多活性位点及低金属含量的双咪唑阳离子乙酸锌低共熔溶剂[C_(2)(Mim)_(2)][OAc]_(2)-2Zn(OAc)_(2),用于催化聚对苯二甲酸乙二醇酯(PET)的乙二醇(EG)醇解反应.通过红外光谱(FTIR)、核磁共振(NMR)和热重(TGA)表征分析了低共熔溶剂催化剂的结构和热稳定性.通过对催化反应参数进行优化发现,当催化剂的用量为PET质量的5%、PET:EG的质量比为1:4时,在190℃的条件下反应70 min后,PET转化率可达100%,对苯二甲酸双羟乙酯(BHET)的产率达85.2%.通过对比反应前后PET的扫描电子显微镜(SEM)图,并利用原位红外监测PET的EG醇解过程推测PET的降解过程,研究了PET的EG醇解反应动力学,结合双咪唑阳离子与乙酸锌和乙酸根与EG之间的氢键作用,推测出[C_(2)(Mim)_(2)][OAc]_(2)-2Zn(OAc)_(2)在EG中催化降解PET可能的反应机理.

The deep eutectic solvent catalyst[C_(2)(Mim)_(2)][OAc]_(2)-2Zn(OAc)_(2)with high thermal stability,multiple active sites and low metal content,was synthesized for the alcoholysis of poly(ethylene terephthalate)(PET)in ethylene glycol(EG).The structure and thermal stability of the deep eutectic solvent catalyst were analyzed by using FTIR,NMR and TGA.The catalytic reaction parameters of reaction time,reaction temperature,and quantity of catalyst and EG were investigated and the optimum reaction conditions were 5%of PET mass,1:4 PET:EG mass ratio,190℃,and 70 min reaction time,which resulted in 100%conversion of PET and 85.2%yield of ethylene terephthalate(BHET).Through comparing the SEM images of PET before and after the reaction,and monitoring the PET glycolysis process with in situ infrared spectroscopy,the degradation process of PET was speculated.The kinetics of PET ethylene glycol alcoholysis reaction were also investigated.The possible reaction mechanism for the catalytic degradation of PET by[C_(2)(Mim)_(2)][OAc]_(2)-2Zn(OAc)_(2)was proposed by combining the hydrogen bonding between bimidazolium cation and zinc acetate,and that between acetate anion and ethylene glycol.