Study on the Monomer Recycling of Plastic Wastes to Feedstock Chemicals.

本研究的目的是根据我们的基本概念“所有塑料部分的完全化学回收”（C_2RAP_2），在不损失任何化学成分的情况下，将常规塑料废物化学回收为原料单体。目标塑料是聚（碳酸酯）（PC），其通过在碳水化合物多元醇中的溶剂分解解聚，被回收为双酚A（BPA）和碳水化合物的环状碳酸酯。首先，在使用PC之前，以碳酸二苯酯（DPC）作为PC的模型，优化用甘油（GLY）处理PC的条件，即，最小的碳水化合物多元醇。事实上，DPC与GLY的碱催化处理几乎定量地产生羟甲基二氧戊环（HMDO）和苯酚。在相同的条件下，用GLY处理PC，再次定量产生BPA和HMDO。在DMF水溶液中，用GLU处理DPC。主要产物为苯酚和葡萄糖二甲醚（GLU-DC），产率为40- 55%。然后，用GLU类似地处理PC，以产生BPA和二乙醇GLU-DC。GLU-DC的化学结构经光谱鉴定为GLU的1，2; 4，6-双环碳酸酯，在3-位保留完整的OH基团。环状碳酸盐是一个碳单元的储集层，即，CO，并且它们可以被重新用于原始PC的再生产。

The aim of the present study was the chemical recycling of conventional plastic wastes to the feedstock monomers in accordance to our basic concept "Complete Chemical Recycling of All Plastic Portions" (C_2RAP_2) without loosing any chemical component. The target plastic was poly(carbonate) (PC) which, by means of solvolytic depolymerization in carbohydrate polyols, was recycled to bisphenol A (BPA) and cyclic carbonates of carbohydrates. Both the products are the monomers of PC and, thus, the complete reclamation of PC to the virgin PC resin can be realized.First, in advance to the use of PC, diphenyl carbonate (DPC) was used as the model of PC to optimize the conditions in the treatment with glycerol (GLY), i.e., the smallest carbohydrate polyol. Indeed, the base-catalyzed treatment of DPC with GLY produced hydroxymethyldioxorane (HMDO) and phenol almost quantitatively. The same conditions were adopted in the treatment of PC with GLY and, again, BPA and HMDO were quantitatively produced.Second, glucose (GLU) was used instead of GLY. The treatment of DPC with GLU was carried out in aqueous solvent of DMF. Phenol and dicarbonate of GLU (GLU-DC) were the major products obtained in the yields of 40-55%. Then, PC was analogously treated with GLU to produce BPA and dicarbonate GLU-DC. The chemical structure of GLU-DC was elucidated spectroscopically to be 1,2;4,6-dicyclic carbonate of GLU leaving the OH group at 3-position intact.To summarize, PC was depolymerized by the solvolytic action of both GLY and GLU to produce BPA and corresponding cyclic carbonate of carbohydrates. The cyclic carbonates are the reservoir of one carbon unit, i.e., CO, and they can be reused for the reproduction of virgin PC.