超临界流体解聚聚碳酸酯的研究
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摘要
超临界流体解聚废弃聚合物以获取化学单体或燃料是一种全新的处理固体废弃物的方法。本论文介绍了超临界流体的基本性质及其在废旧塑料化学循环回收中的应用，综述了聚碳酸酯塑料(PC)循环利用领域的研究现状以及目前国内外关于PC解聚的研究进展。
实验研究了不同条件(反应温度，反应压力，反应时间及投料比)下，聚碳酸酯塑料在超临界甲苯中的解聚反应，产物用傅立叶红外光谱(FT-IR)、气相色谱(GC)、气-质联谱(GC-MS)分析，分析表明，解聚主产物为双酚A(BPA)。在实验取值范围内，PC解聚率与主要产物双酚A在液相产物中的含量随温度的升高、反应时间的延长而增加，并得出在投料比为7、反应温度340℃、反应时间为30min的条件下，主产物双酚A在液相中的含量达到55.57％(最高)。通过数据拟合，确定解聚反应为一级反应，超临界甲苯中的反应活化能为61.41kJ／mol。
此外，以甲苯和乙醇混合物作为解聚溶剂，通过改变反应条件对聚碳酸酯颗粒进行解聚实验研究，其主产物为双酚A。当解聚条件控制在300℃、45min时，可以得到较高的解聚率(90.75％)，及较高含量的双酚A(95.98％)。因此，在甲苯溶剂中添加一定比例的乙醇(甲苯与乙醇质量比为6)有利于PC解聚反应的进行。
超临界流体解聚聚碳酸醋的研究
通过对PC超临界解聚的途径分析发现，解聚以链随机断裂为主要
解聚方式。解聚属于自由基反应类型，主要包括的自由基反应分别为:
链随机断裂、C一H裂解;分子间、分子内氢转移;自由基重组、自由
基歧化。
超临界流体优异的溶解能力和传质性能，增强了分子的流动性，提
高了氢原子自由转移并参加自由基反应的能力。
A new approach for polymer recycling is to depolymerize polymers into monomers, dimers, and useful hydrocarbon materials or liquid fuels in supercritical fluids. The paper introduces the basal characteristics of supercritical fluids and its application on chemical recycling of waste plastics. Recent studies progress on recycling of polycarbonate (PC), especially on chemical recycling, are summarized.
Depolymerization of polycarbonate (PC) in supercritical toluene was carried out in a stirred batch autoclave at different conditions such as reaction temperature, resistant time,reactor pressure and the weight ratio of toluene to PC and so on. The depolymerization products were examined by GC-MS, GC, FT-IR, respectively. The main reaction products were bisphenol A(BPA), PC Conversion and content of bisphenol A in the liquid products increases with the increase of temperature and the reaction time. The results of kinetic analysis showed that the depolymerization reaction rate was first order to the polycarbonate concentration. The dependence of the rate constant on the reaction temperature was correlated by the Arrhenius relation, which shows the activation energy of 61.41kJ·mol~(-1) in supercritical toluene.
Depolymerization of PC in supercritical toluene/alcohol co-solvent was also carried out at different tenperature range and at reaction time respectively. The main reaction products were bisphenol A by gas chromatography-mass spectrometry and gas chromatography respectively. Reaction temperature, resident time play a role on component contents of the liquid products. It is found out that the optimized conditions of the
reaction are at temperature of 300℃, reaction time of 45min.
By discussing mechanisms of depolymerization, Random scission is the
main depolymerization path in supercritical fluids. Studies show depolymerization path in supercritical fluid is a typical free radical reaction, which includes random scission, carbon-hydrogen bond fission, propagation H abstraction, intramolecular H abstraction and recombination, disproportionation reactions are the relevant reaction classes.
Excellent solubility and mass transfer of supercritical fluids improve greatly molecular fluidity, and enhance hydrogen transfer and engaging in free radical reaction.
实验研究了不同条件(反应温度，反应压力，反应时间及投料比)下，聚碳酸酯塑料在超临界甲苯中的解聚反应，产物用傅立叶红外光谱(FT-IR)、气相色谱(GC)、气-质联谱(GC-MS)分析，分析表明，解聚主产物为双酚A(BPA)。在实验取值范围内，PC解聚率与主要产物双酚A在液相产物中的含量随温度的升高、反应时间的延长而增加，并得出在投料比为7、反应温度340℃、反应时间为30min的条件下，主产物双酚A在液相中的含量达到55.57％(最高)。通过数据拟合，确定解聚反应为一级反应，超临界甲苯中的反应活化能为61.41kJ／mol。
此外，以甲苯和乙醇混合物作为解聚溶剂，通过改变反应条件对聚碳酸酯颗粒进行解聚实验研究，其主产物为双酚A。当解聚条件控制在300℃、45min时，可以得到较高的解聚率(90.75％)，及较高含量的双酚A(95.98％)。因此，在甲苯溶剂中添加一定比例的乙醇(甲苯与乙醇质量比为6)有利于PC解聚反应的进行。
超临界流体解聚聚碳酸醋的研究
通过对PC超临界解聚的途径分析发现，解聚以链随机断裂为主要
解聚方式。解聚属于自由基反应类型，主要包括的自由基反应分别为:
链随机断裂、C一H裂解;分子间、分子内氢转移;自由基重组、自由
基歧化。
超临界流体优异的溶解能力和传质性能，增强了分子的流动性，提
高了氢原子自由转移并参加自由基反应的能力。
A new approach for polymer recycling is to depolymerize polymers into monomers, dimers, and useful hydrocarbon materials or liquid fuels in supercritical fluids. The paper introduces the basal characteristics of supercritical fluids and its application on chemical recycling of waste plastics. Recent studies progress on recycling of polycarbonate (PC), especially on chemical recycling, are summarized.
Depolymerization of polycarbonate (PC) in supercritical toluene was carried out in a stirred batch autoclave at different conditions such as reaction temperature, resistant time,reactor pressure and the weight ratio of toluene to PC and so on. The depolymerization products were examined by GC-MS, GC, FT-IR, respectively. The main reaction products were bisphenol A(BPA), PC Conversion and content of bisphenol A in the liquid products increases with the increase of temperature and the reaction time. The results of kinetic analysis showed that the depolymerization reaction rate was first order to the polycarbonate concentration. The dependence of the rate constant on the reaction temperature was correlated by the Arrhenius relation, which shows the activation energy of 61.41kJ·mol~(-1) in supercritical toluene.
Depolymerization of PC in supercritical toluene/alcohol co-solvent was also carried out at different tenperature range and at reaction time respectively. The main reaction products were bisphenol A by gas chromatography-mass spectrometry and gas chromatography respectively. Reaction temperature, resident time play a role on component contents of the liquid products. It is found out that the optimized conditions of the
reaction are at temperature of 300℃, reaction time of 45min.
By discussing mechanisms of depolymerization, Random scission is the
main depolymerization path in supercritical fluids. Studies show depolymerization path in supercritical fluid is a typical free radical reaction, which includes random scission, carbon-hydrogen bond fission, propagation H abstraction, intramolecular H abstraction and recombination, disproportionation reactions are the relevant reaction classes.
Excellent solubility and mass transfer of supercritical fluids improve greatly molecular fluidity, and enhance hydrogen transfer and engaging in free radical reaction.
引文
[1] 苏庆平，周俊治，史征绥．“白色污染”及废旧塑料的回收利用[J]．四川环境，2000，19(4)：26-28，45．
[2] 欧育湘，唐小勇，王建荣．鉴别废旧塑料的先进红外技术[J]．化工进展，2003，22(3)：267-270．
[3] 焦书科．废弃高分子材料的处理[J]．合成橡胶工业，1996，19(2)：67-70．
[4] Werner H Hauthal. Advances with supercritical fluids [review] [J].Chemosphere, 2001(43): 123-135.
[5] Karmore Vishal, Madras Giridhar. Continuous distribution kinetics for the degradation of polystyrene in supercritical benzene[J]. Industrial & Engineering Chemistry Research, 2000,39(11): 4020-4023.
[6] Fang Z, Kozinski J A. A comparative study of polystyrene decomposition in supercritical water and air environments using diamond anvil cell[J]. Journal of Applied Polymer Science, 2001,81(14): 3565-3577.
[7] Toshiaki Y, Tsutomu M, Akitsugu. Kinetics of hydrolysis of polyethylene terephthalate powder in sulfuric by a modified shrinkig-core model[J]. Ind. Eng. Chem. Res., 2001,40:75-79.
[8] 孟令辉，白永平，冯立群．超临界方法在塑料分解回收中的应用研究[J]．中国塑料，1999，13(9)：76-82．
[2] 欧育湘，唐小勇，王建荣．鉴别废旧塑料的先进红外技术[J]．化工进展，2003，22(3)：267-270．
[3] 焦书科．废弃高分子材料的处理[J]．合成橡胶工业，1996，19(2)：67-70．
[4] Werner H Hauthal. Advances with supercritical fluids [review] [J].Chemosphere, 2001(43): 123-135.
[5] Karmore Vishal, Madras Giridhar. Continuous distribution kinetics for the degradation of polystyrene in supercritical benzene[J]. Industrial & Engineering Chemistry Research, 2000,39(11): 4020-4023.
[6] Fang Z, Kozinski J A. A comparative study of polystyrene decomposition in supercritical water and air environments using diamond anvil cell[J]. Journal of Applied Polymer Science, 2001,81(14): 3565-3577.
[7] Toshiaki Y, Tsutomu M, Akitsugu. Kinetics of hydrolysis of polyethylene terephthalate powder in sulfuric by a modified shrinkig-core model[J]. Ind. Eng. Chem. Res., 2001,40:75-79.
[8] 孟令辉，白永平，冯立群．超临界方法在塑料分解回收中的应用研究[J]．中国塑料，1999，13(9)：76-82．