聚对苯二甲酸丁二醇酯在亚临界水中的催化解聚

Catalytic Depolymerization of Polybutylene Terephthalate in Subcritical Water

研究间歇高压反应釜中聚对苯二甲酸丁二醇酯(PBT)以醋酸铜为催化剂在亚临界水中的解聚反应。主要考察反应时间(10～50 min)和反应温度(493～553 K)对PBT解聚率以及产物产率的影响。反应产物分别采用气相色谱、气-质联用仪、傅里叶红外光谱、高效液相色谱和液-质联用仪进行分析,主产物为对苯二甲酸(TPA)和四氢呋喃(THF),产物中并未检测出1,4-丁二醇,与相关文献的研究结果不同。实验结果表明:PBT的解聚率随温度的升高、反应时间的延长而增加。在投料比8:1(24.0 g H2O/3.0 g PBT),催化剂醋酸铜0.03 g/3.0 g PBT,反应温度523 K,时间50 min条件下,PBT可完全解聚,TPA和THF的产率分别为99.3%和83.1%。根据PBT在亚临界水中催化解聚产物的分析,提出PBT催化水解反应机理。通过实验数据关联,得出催化解聚反应级数为一级,反应活化能为141.6 kJ mol 1。在微型毛细管反应器中结合显微镜研究了PBT在醋酸铜水溶液相态变化,温度上升至553 K停留19 min后PBT能完全溶解于水中,解聚反应在液相均相中进行。

Catalytic depolymerization of polybutylene terephthalate （PBT） in subcritical water with catalysis of cupric acetate was carried out in a batch high pressure autoclave. The effects of reaction temperature （493-553 K） and time （10-50 min） on PBT depolymerization were studied. The main depolymerization products, which are terephthalic acid （TPA） and tetrahydrofuran （THF）, were determined by the analyses of GC, GC-MS, FT-IR, HPLC and LC-MS, and the 1,4-butanediol was not detected, though this depolymerization product of PI3T is claimed to be found in some other relative literatures. It was found that the PBT depolymerization ratio increases with increasing reaction temperature and time. Under the conditions of temperature 523 K, reaction time 50 min, feeding ratio of 8：1 （24.0 g H20/3.0 g PBT） and 0.03 g cupric acetate, the PBT can be totally depolymerized and the yields of TPA and THF can reach 99.3% and 83.1%, respectively. Based on the analyses of the product species, the depolymerization reaction mechanism was proposed. The results of kinetic analyses show that the depolymerization follows a pseudo-first-order kinetics with the activation energy of 141.6 kJ.mo1-1. Phase behavior changes of PBT in aqueous cupric solution were observed and the images were recorded in fused silica capillary reactor under a microscope. The PBT can dissolve in water totally at 553 K after 19 min, and the depolymerization reaction occurs in homogeneous phase.