*6.2.5 rPET material flow*

The collected feedstock for recycle is the result of manual or automated sorting to concentrate the PET fraction of a waste stream [61]. Post-consumer PET must be separated to reclaim the desired feed from contaminating non-PET. Items such as caps, lids, labels, adhesives, dirt, foreign plastics, and residual content reduce the quality of the final product and may significantly change the molar mass of the newly former polymer [61, 73]. Upon completion of the polymerization process, conversion to final product continues to the consumer and a new collection for recycle or disposal.

## **6.3 Pyrolytic and thermal processing**

Pyrolysis is a chemical process using heat and pressure to depolymerize longchain polymer molecules to form smaller, less complex molecules. Pyrolysis requires oxygen-free conditions for fast thermal degradation of plastic waste, which can be accomplished by using noncatalytic or catalytic conditions with zeolite, spent Fluid Catalytic Cracking catalyst, and MfO catalyst at temperatures varying from 300 to 800°C. Major products formed from the pyrolytic treatment of waste plastic feedstock are gas, oil, and char [23, 24]. Pyrolysis yields on average 45–50% of oil, 35–40% of gases, and 10–20% of tar. This conversion process can achieve up to 80% liquid oil at a moderate temperature of 500°C [27] and reaching 88 wt% liquid yields at 580°C. Plastics offer higher energy content mass than biofuels such as wood and coal.

A facility in Woodlands, Texas, USA initially was used to produce coal-derived products such as benzene, toluene, and xylene (BTX). It currently uses catalytic pyrolysis to convert post-consumer waste plastics into BTX. Similarly, a plastic-tofuel facility in Virginia converts scrap plastic into fuel or chemical products [23]. The commonly used catalysts for pyrolysis conversion involve cracking, oligomerization, cyclization, aromatization, and isomerization reactions. Catalysts used in these processes include ZSM-5, zeolite, Y-zeolite, FCC, and MCM-41 [15, 28]. Light oil recovered from pyrolysis can be used as a chemical feedstock to produce new plastics or chemicals, whereas medium and heavy oils are commonly used as diesel fuel and heavy oils are used for power generation. For example, a large plant in Sapporo, Japan has a novel flexible system that receives not only PET, and PP, but also PVC, which is considered contaminants for PET recycling (**Figure 9**) [29].
