Polystyrene recycling is becoming a strong focus in South Africa and last week, we reported on an initiative in Pretoria East for kerbside collections of this waste, along with the Polystyrene Packaging Council. Now it seems that chemists in the United States have discovered a way to convert unwanted polystyrene back to styrene monomer. The results were published by Prof. Lanny Schmidt from the University of Minnesota in the sustainable chemistry journal ChemSusChem.
The process has the potential to render polystyrene recycling more economical by creating high-quality new materials instead of merely melting and remoulding contaminated plastics into low-value goods. The aim of Schmidt’s team was to re-establish the original monomer to allow it to be reprocessed into either virgin plastic or other products. The process relies on a platinum or rhodium catalyst combined with cerium and supported on alumina spheres. As a result of the heat given off by the reaction of the particles as they pyrolyse into styrene, running costs are significantly reduced because no other heat input is necessary.
“To our surprise, we got up to 80% styrene monomer,” Schmidt said, adding that the lab-scale reactor using 1g of catalyst is capable of processing up to 1 kg of polystyrene daily.
