Abstract
Supercritical water, which has unique properties and is environment-friendly, attracts much attention as a medium for conducting chemical reactions. Decomposition of plastic waste in supercritical water has been studied as an innovative technology for recycling. This article shows an overview of fundamental investigations and processing consideration on the decomposition of plastics in supercritical water, including details regarding the effects of temperature and pressure. PET and Nylon 6, which are condensation polymerization plastics, were able to hydrolyze with high efficiency in supercritical water to respective monomers (terephthalic acid and ε-caprolactam). Decomposition in supercritical water is also a powerful-method for liquefaction of addition polymerization plastics such as polyethylene and polypropylene. Decomposition of thermosetting resins in supercritical water could afforded chemical raw materials, but in less satisfactory yields. Flow-reaction processing concepts, which are indispensable to put this method to practical use, were developed for recovery of monomer or oil conversion.
