NOVELTY - A polyolefin group plastic (GRP) and plastic of other than GRP are separated from waste plastic. GRP is vaporized by thermal decomposition (II). The thermal decomposition gas (5) obtained is thermally decomposed in presence of catalyst. A high boiling point component is separated from gas (13) obtained. The gas is further subjected to vapor liquid separation (V) to separate gaseous and liquid phases.    USE - For recycling waste plastic such as city refuse and for recovering aromatic hydrocarbons such as 2-4C olefin gas used as plastic raw material, hydrogen used as fuel for fuel cells and as raw material for hydrogenation and desulfurization, benzene, xylene and toluene which are used as chemical and pharmaceutical raw materials.    ADVANTAGE - Olefin gas, hydrogen and xylene are effectively recovered from the waste plastic. Thus the waste plastic is recycled effectively and efficiently. Since the waste plastic is heated at the dechlorination process, the waste plastic is in molten state. Thus the handleability of the waste plastic is improved. Since a primary catalyst is supplied to the thermal decomposition process, the reaction rate of the thermal decomposition is increased. Thus subsequent catalyst decomposition is performed rapidly and chemical recycle is also performed efficiently. By adjusting the flow rate ratio of the thermal decomposition gas supplied to the catalyst decomposition portions through the distribution controlling valve, the formation ratio of 2-4C olefin, xylene and hydrogen can be adjusted arbitrarily. Thus the formation rate of the aromatic hydrocarbons is improved. Since the chemical recycle apparatus has simple components, the installation cost is reduced.    DETAILED DESCRIPTION - Waste plastic is subjected to pretreatment (I) to separate polyolefin group plastic and plastic of other than polyolefin group plastic from waste plastic. The polyolefin group plastic is vaporized by thermal decomposition. The thermal decomposition gas obtained is thermally decomposed in a catalyst decomposition portion (I) (8) in the presence of a boron containing silicate catalyst (7) to obtain 2-4C olefin. The gas is again thermally decomposed in a catalyst decomposition portion (II) (10) in the presence of a gallium-containing silicate catalyst (9) to obtain benzene, toluene, xylene and hydrogen. A high boiling point component is separated from gas obtained from catalyst decomposition process. The gas obtained is further subjected to vapor liquid separation process which cools the gas to separate the gaseous phase comprising 2-4C olefin gas as main component and hydrogen, and liquid phase comprising benzene, toluene and xylene as main component.    An INDEPENDENT CLAIM is included for a chemical recycle apparatus of waste plastic, which has a preprocessor (1), a thermal decomposition tank (2), catalyst decomposition portions (I,II) arranged serially, reflux device (14), and condenser (15). The preprocessor has at least a selector (1a) which separates a waste plastic to a polyolefin group plastic and other plastic. The thermal decomposition tank vaporizes the polyolefin group plastic by thermal decomposition. The reflux device separates high boiling point component from the gas obtained from catalyst decomposition portion (II). The condenser cools the gas introduced from the reflux device to separate the gas into gaseous phase and liquid phase.    DESCRIPTION OF DRAWING(S) - The figure shows the flowchart of the chemical recycle apparatus used for chemical recycle of waste plastic. (Drawing includes non-English language text).    Preprocessor (1)    Selector (1a)    Thermal decomposition tank (2)    Decomposition gas (5)    Boron containing silicate catalyst (7)    Catalyst decomposition portion (I) (8)    Gallium containing silicate catalyst (9)    Catalyst decomposition portion (II) (10)    Gas (13)    Reflux device (14)    Condenser (15)    Gaseous phase (16)    Liquid phase (17)    Distillation column (18)    Primary catalyst (21)    Gas separator (24)    Pretreatment process (I)    Heat decomposition (II)    Vapor liquid separation (V)