Driving selective upcycling of mixed polyethylene waste with table salt

Abstract

Advanced recycling offers a unique opportunity for the circular economy, especially for mixed and contaminated plastics that are difficult to recycle mechanically. However, advanced recycling has barriers such as poor selectivity, contaminant sensitivity, and the need for expensive catalysts. Reported herein is a simple yet scalable methodology for converting mixed polyethylene (high-density and low-density polyethylene recycled polyethylene) into upcycled waxes with up to 94% yield. This high yield was possible by performing the reaction at a mild temperature and was enabled by using inexpensive and reusable table salt. Without table salt, in otherwise identical conditions, the plastic remained essentially undegraded. These upcycled waxes were used as prototypes for applications such as water- and oil-resistant paper, as well as rheology modifiers for plastics. Their performance is similar to that of commercial wax as well as rheology modifiers. A preliminary economic analysis shows that the upcycled waxes obtained by this table salt-catalyzed approach offer three times more revenue than those reported in the literature. This pioneering discovery opens the door for a circular economy of plastics in general and polyolefins in particular.

Tailoring Olefin Contents Formation during Waste Plastic Pyrolysis

“…Among all of these, thermal pyrolysis is one of the most promising chemical recycling processes. During pyrolysis, plastic undergoes thermal degradation in the absence of oxygen to produce a liquid product that resembles oil 23 or wax 24,25 along with trace amounts of gaseous products and solid residues. 26−28 The product distribution and composition depend on the type of feedstock, heating rate, temperature, pressure, catalyst, and reactor type.…”