聚对苯二甲酸乙二醇酯在超临界甲醇中解聚的研究

Depolymerization of Polyethylene Terephthalate in Supercritical Methanol

在间歇高压反应器中研究了聚对苯二甲酸乙二醇酯(PET)在超临界甲醇中的解聚反应特性, 通过扫描电镜观测了不同解聚条件下固相聚合物的内部结构,提出了解聚反应历程并得到了不同解聚条件下反应表观活化能。在甲醇的非临界区域,PET在甲醇中表现为溶胀过程,解聚程度低,反应在聚合物表面进行,反应表观活化能为27.19kJmol-1,解聚过程为传质、扩散控制;在甲醇的临界区域, PET完全溶于甲醇,解聚反应在均相中进行,反应表观活化能为89.79kJmol-1,为化学反应控制。

Depolymerization of polyethylene terephthalate (PET) in supercritical methanol was carried out by using a batch autoclave reactor. Internal structure of depolymerized PET obtained under different decomposition conditions was detected by scanning electron microscope (SEM). The depolymerization mechanism was proposed. In the sub-critical region of methanol, the depolymerization reaction primarily occurs on the surface of PET, which mainly shows a swelling process with the total depolymerization rate of PET less than 20% within 60 min at 200°C. In the super critical region of methanol, the depolymerization reaction occurs out in homogeneous phase, and PET solves quickly with the total depolymerization rate of PET increasing observably to 85.42% within 20 min at 265°C. A kinetic model to describe the depolymerization of PET was proposed, where the reaction activity energy was evaluated to be 89.79 kJ&middotmol-1 and 27.19 kJ&middotmol-1 in super critical and sub-critical methanol respectively. The controlling process of depolymerization changes from mass transfer and scatter process in sub-critical methanol to chemical reaction in supercritical methanol.