DISPOSAL SYSTEM OF PLASTIC MATERIAL

PROBLEM TO BE SOLVED: To prevent a reaction vessel from corrosion by, prior to and/or after the decomposition treatment of a plastic material in a supercritical fluid as a solvent, subjecting the subject plastic material to a chemical reaction to control the mol.wt. and/or compsn. of decomposed compds., or to remove acids from the product in case the plastic material is halogen-contg. SOLUTION: A system to decompose a plastic material by liquefying, gasifying, oligomerizing or monomerizing the material wherein the subject material is subjected to one or more chemical reactions selected from the group consisting of hydrogenation, hydrogenation-decomposition, dehydrogenation, oxidation, dehalogenation and solvolysis prior to and/or after the treatment of the plastic material in a supercritical fluid. When necessary, a catalyst, pref. a heterogeneous catalyst is employed to accelerate the chemical reaction. The treatment in a supercritical fluid can enhance the decomposition ratio of a plastic material which is otherwise low.