Depolymerization mechanism of poly(ethylene terephthalate) in supercritical methanol
Depolymerization mechanism of poly(ethylene terephthalate) in supercritical methanol
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DOI：
10.1021/ie0488187
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发表时间：
2005-05-25
影响因子：
4.2
通讯作者：
Hirose, T
中科院分区：
文献类型：
--
作者：
Genta, M;Iwaya, T;Hirose, T
研究了聚对苯二甲酸乙二酯（PET）在超临界甲醇中的解聚动力学，以开发废旧PET瓶的化学回收工艺。具有高分子量（TV值（特性粘度）= 0.84）的PET在间歇式反应器中在543和573 K之间的温度下在0.1-15 MPa的估计压力下解聚。除了具有高分子量的PET之外，具有低分子量的PET，例如其低聚物（三聚体）、对苯二甲酸双羟乙酯（BHET）和对苯二甲酸甲酯-（2-羟乙基）酯（MHET），被用作模型反应物以澄清聚（对苯二甲酸乙二醇酯）在超临界甲醇中的解聚途径。采用分子排阻色谱法、高效液相色谱法和高效液相色谱-质谱法对反应产物进行分析。各反应的主要产物为单体对苯二甲酸二甲酯（DMT）和乙二醇（EG）。高分子量PET解聚成低聚物的速度比低聚物解聚成单体的速度快。通过MHET将PET解聚为DMT和EG。动力学研究表明，PET的解聚过程是连续进行的，其中低聚物转化为单体的步骤是一个速率控制步骤。MHET是解聚反应中相对稳定的中间体。速率常数用简单的反应模型估算。提出了PET在超临界甲醇中解聚的动力学模型。
The kinetics of poly(ethylene terephthalate) (PET) depolymerization in supercritical methanol was investigated to develop a chemical recycling process for postconsumer PET bottles. PET with a high molecular weight (TV value (intrinsic viscosity) = 0.84) was depolymerized in a batch reactor at temperatures between 543 and 573 K under estimated pressures of 0.1-15 MPa. In addition to PET with high molecular weight, PET with low molecular weight, such as its oligomer (trimer), bis-hydroxyethyl tereplithalate (BHET), and methyl-(2-hydroxyethyl) terephthalate (MHET), was used as a model reactant to clarify the depolymerization pathway of poly(ethylene terephthalate) in supercritical methanol. The reaction products were analyzed with size-exclusion chromatography, high-performance liquid chromatography, and high-performance liquid chromatography-mass spectrometry. The main products of each reaction were the monomers, dimethyl terephthalate (DMT) and ethylene glycol (EG). The depolymerization of high molecular weight PET to its oligomer was faster than that of the oligomer to its monomer. PET was depolymerized into DMT and EG through MHET. The kinetics study showed that the depolymerization of PET proceeds consecutively, where the step of the oligomer to its monomer would be a rate-determining step. MHET is a relatively stable intermediate in the depolymerization. The rate constants were estimated with simple reaction models. This kinetic model of PET depolymerization in supercritical methanol was proposed.