MSU Technologies

Process for Depolymerizing Recycled Polystyrenes

Executive Summary

Each year, billions of lbs of polystyrene and styrene copolymers are discarded as waste and very little is recycled. While some technologies have attempted pyrolysis in fluidized bed reactors or solvent processes to convert the polystyrene back to monomer, high costs, long process times and a myriad of reaction products have limited their commercial success. MSU researchers have recently developed a new technology for chemical recycling of polystyrenes that is fast and provides and economical route to monomer recovery.

Description of Technology

This invention is a novel process that involves melt processing of polystyrenes in the presence of inexpensive and non-toxic catalysts such as metal salts and metal oxides. High yield to styrene monomer is obtained in less than 45 minutes process time. Small scale experiments at 420*C have resulted in liquid yields of over 80% containing up to 83% styrene monomer and much lower levels of dimer/trimer and alpha methyl styrene compared to non-catalyzed samples.

Benefits

Rapid degradation back to monomer (up to 70% yield of styrene from original polymer)
High styrene concentrations in liquid stream (up to 83%)
Safe, inexpensive catalysts
Enables recycling of waste polystyrene foam, packaging, cups, plates, containers
Can be used for styrene containing copolymers and other vinyl polymers