Taking PET recycling to the next level

Chains become smaller molecules

Evonik is building a platform ­technology for ­recycling of various polymers. Mechanical recycling is usually the first choice, supported by Evonik´s range of process chemicals. To date, the plastic polyethylene terephthalate (PET) has a very successful tradition of being mechanically recycled. The collected bottle grade PET is shredded, cleaned, melted down, and once again moulded into bottles. However, this process cannot be used with other PET grades, which are dirty, carry complex additives, or simply are at their life cycle end with regard to mechanical recycling.

Evonik is working to develop processes for these PET grades — and is thus making it possible to recycle entirely new material flows. The process development for these PET grades has already made good progress. In terms of the chemistry involved, this process is a transesterification with alkoxide catalysts: The PET raw material is combined with an alcohol and the catalyst and is then treated thermally. The resulting reaction produces a terephthalic ester and ethylene glycol. These compounds can be then used later for repolymerization and for the production of specialty chemicals. 

Evonik´s next step is the development of efficient and scalable industrial processes for exploiting the economic potential of chemical recycling. The idea is to create a platform technology which can be used to recycle other classes of polymers, and for multiple raw material grades which currently are not accessible for mechanical recycling.