超/亚临界水中聚对苯二甲酸乙二醇酯的解聚

Depolymerization of Polyethylene Terephthalate in Sub-and Supercritical Water

采用间歇式高压反应装置研究了聚对苯二甲酸乙二醇酯（PET）在超，亚临界水中的解聚．考察了投料比、反应温度及反应时间对PET解聚率及主产物对苯二甲酸（TPA）和乙二醇（EG）产率的影响。固相产物采用傅里叶红外光谱（FT-IR）、液相色谱（HPLC）进行分析，液相产物采用气相色谱（GC）和气．质联谱（GC-MS）进行分析。实验结果表明，在压力2．2～31．5MPa、温度220--400℃和反应时间5—90min的条件下，在超，亚临界水中PET能有效地解聚，反应温度和反应时间是影响PET解聚的主要因素。在投料比（水的质量／PET质量）为8：1，反应温度320℃，反应时间15min条件下，PET解聚完全，产物TPA产率达93．23％，EG产率为39．90％。在实验基础上，探讨了PET水解反应机理。通过实验数据关联，得出解聚反应级数为一级，解聚反应活化能为90．47kJ．mol-1。实验结果为选择PET的解聚介质和工艺参数提供依据。

Depolymerization of polyethylene terephthalate （PET） in sub- and supercritical water was carried out in a batch autoclave. The influences of experimental parameters, such as reaction time, reaction temperature and the ratio of water to PET, on the depolymerization ratio and the yield of TPA （terephthalic acid） and EG （ethylene glycol） were investigated. The HPLC, FT-IR, GC and GC-MS were used to analyze the solid product （TPA） and liquid product （EG）, respectively. It was found that the depolymerization temperature and time are two critical factors for the depolymerization process, and the PET could be effectively depolymerized under the temperature of 220-400~C, pressure of 2.2-31.5 MPa and reaction time of 5-90 min. The optimal PET depolymerization conditions found are temperature of 320~C, reaction time of 15 min and the ratio （water to PET） of 8. Under these conditions, PET could be depolymerized totally and the yields of TPA and EG could reach 93.23% and 39.90%, respectively. In addition, a reaction mechanism of the hydrolysis of PET was proposed, and the kinetic analysis shows that the depolymerization reaction in sub- and supercritical water is a first-order reaction and its activation energy is 90.47 kJ.mol-1. The obtained results could enforce the basic knowledge of selecting PET depolymerization medium and the technological parameters for PET depolymerization.