用于合成聚对苯二甲酸乙二醇酯的Zn/Al复合氧化物催化剂

Synthesis of polyethylene terephthalate by esterification over Zn/Al composite oxides

以尿素为沉淀剂,采用沉淀法制备了不同n(Zn)∶n(Al)和不同焙烧温度的Zn/Al复合氧化物,通过XRD、TGDTA、CO2-TPD和N2吸附-脱附等方法对催化剂的结构和碱性进行了表征,并将其用于对苯二甲酸和乙二醇酯化合成聚对苯二甲酸乙二醇酯(PET)缩聚阶段的催化剂。采用FTTR,1H NMR,13C NMR方法对PET的结构进行了表征,研究了催化剂结构、碱度和碱量与催化活性的关系,同时考察了工艺条件对合成PET性能的影响。实验结果表明,n(Zn)∶n(Al)=1、焙烧温度为500℃的ZnAlOX-500催化剂的活性最高,在催化剂用量为0.25%(w)、缩聚第一阶段反应时间和温度为90 min和260℃、缩聚第二阶段反应时间和温度为90 min和280℃的工艺条件下,PET的特性黏数可达0.820 dL/g、端羧基值为44.19 mol/t、二甘醇含量为3.44%(w)。

A series of Zn/Al composite oxides were prepared by precipitation and applied to the synthesis of polyethylene terephthalate(PET)from terephthalic acid and ethylene glycol.The structure and basic strength of the catalysts were characterized by XRD,TG-DTA,CO2-TPD and N2 adsorption-desorption.The structure of PET was analyzed by FTTR,1H NMR and 13C NMR.The relationship between structure,basic strength and basicity of the catalysts and activity of synthesized PET were discussed.The results show that the activity of ZnAlOX-500(n(Zn)∶n(Al)1,calcination temperature 500℃)was the highest.The intrinsic viscosity of 0.820 dL/g,carboxyl end group value of 44.19 mol/t,diethylene glycol content of 3.44%(w)were obtained under 0.25%(w)catalyst content,the first stage polycondensation reaction time 90 min and the reaction temperature 260℃,the second stage polycondensation reaction time 90 min and the reaction temperature 280℃.