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

本研究的目的是按照我们的基本概念“所有塑料部分完全化学回收”（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。目标塑料为聚碳酸酯（PC），通过在碳水化合物多元醇中溶剂解聚，回收得到双酚A （BPA）和碳水化合物的环状碳酸盐。这两种产品都是PC的单体，从而实现了PC对PC树脂的完全回收。首先，在PC使用之前，以碳酸二苯酯（DPC）为PC的模型，优化了甘油（GLY）（最小碳水化合物多元醇）处理PC的条件。事实上，GLY对DPC的碱催化处理几乎可以定量地产生羟甲基二氧庚烷（HMDO）和苯酚。用GLY处理PC采用同样的条件，同样定量地产生了BPA和HMDO。其次，用葡萄糖（GLU）代替GLY。用GLU在DMF水溶液中处理DPC。主要产物为苯酚和二碳酸酯（GLU- dc），收率为40-55%。然后，将PC与GLU进行类似处理，得到双酚a和碳酸酯GLU- dc。通过光谱分析，确定了GLU-DC的化学结构为1,2；GLU的4,6-二环碳酸盐留下3位羟基完整。综上所述，PC在GLY和GLU的溶剂解聚作用下解聚生成BPA和相应的碳水化合物环碳酸酯。旋回碳酸盐是一种碳单元（即CO）的储层，它们可以重复用于原生PC的再生。

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.