Provided is a continuous process for converting waste plastic into recycle for polyethylene polymerization. The process comprises selecting waste plastics containing polyethylene and/or polypropylene and preparing a blend of petroleum and the selected plastic. The amount of plastic in the blend comprises no more than 20 wt. % of the blend. The blend is passed to a refinery hydrocracking unit. A liquid petroleum gas C.sub.3-C.sub.4 olefin/paraffin mixture, and optionally naphtha, is recovered from the hydrocracking unit and passed to a steam cracker to make ethylene. A heavy fraction can also be recovered from the hydrocracking unit and passed to an isomerization dewaxing unit to prepare base oil.

Provided is a continuous process for converting waste plastic into recycle for polyethylene polymerization. The process comprises selecting waste plastics containing polyethylene and/or polypropylene and preparing a blend of petroleum and the selected plastic. The amount of plastic in the blend comprises no more than 20 wt. % of the blend. The blend is passed to a refinery hydrocracking unit. A liquid petroleum gas C.sub.3-C.sub.4 olefin/paraffin mixture, and optionally naphtha, is recovered from the hydrocracking unit and passed to a steam cracker to make ethylene. A heavy fraction can also be recovered from the hydrocracking unit and passed to an isomerization dewaxing unit to prepare base oil.

An olefin production method is provided involves a step of catalytically cracking a raw material containing at least a polyolefin and an organochlorine compound in the presence of a zeolite catalyst having a sodium atom content of less than 0.1% by mass. This method improves olefin yield.

An olefin production method is provided involves a step of catalytically cracking a raw material containing at least a polyolefin and an organochlorine compound in the presence of a zeolite catalyst having a sodium atom content of less than 0.1% by mass. This method improves olefin yield.

The invention relates to a process for depolymerization of polymer compositions with decomposition of halogen-containing organic compounds, wherein the polymer composition contains at least one styrene-containing polymer and at least one halogen-containing organic compound. The addition of one or more inorganic basic compounds in the depolymerization simultaneously promotes the decomposition of the halogen-containing organic compound and favors the depolymerization.

The invention relates to a process for depolymerization of polymer compositions with decomposition of halogen-containing organic compounds, wherein the polymer composition contains at least one styrene-containing polymer and at least one halogen-containing organic compound. The addition of one or more inorganic basic compounds in the depolymerization simultaneously promotes the decomposition of the halogen-containing organic compound and favors the depolymerization.

Systems and methods for recycling waste plastics are provided, including a system for recovering styrene monomer from waste polystyrene. The system includes a mixing, heating and compacting apparatus to receive a supply of waste polystyrene and to output a densified polystyrene containing melt; a pyrolysis reactor configured to receive the densified polystyrene containing melt and a supply of recycled oligomers, pyrolyze the densified polystyrene containing melt and the recycled oligomers, and output a hydrocarbon gas stream and a solids residue stream; a quenching apparatus configured to receive the hydrocarbon gas stream output from the pyrolysis reactor and condense out oligomers for routing upstream to the pyrolysis reactor to be combined as the supply of recycled oligomers with the densified polystyrene containing melt, and to discharge an altered hydrocarbon gas stream for further processing; and a condenser configured to receive the altered hydrocarbon gas stream from the quenching apparatus and condense out styrene to form a styrene monomer oil product.

Systems and methods for recycling waste plastics are provided, including a system for recovering styrene monomer from waste polystyrene. The system includes a mixing, heating and compacting apparatus to receive a supply of waste polystyrene and to output a densified polystyrene containing melt; a pyrolysis reactor configured to receive the densified polystyrene containing melt and a supply of recycled oligomers, pyrolyze the densified polystyrene containing melt and the recycled oligomers, and output a hydrocarbon gas stream and a solids residue stream; a quenching apparatus configured to receive the hydrocarbon gas stream output from the pyrolysis reactor and condense out oligomers for routing upstream to the pyrolysis reactor to be combined as the supply of recycled oligomers with the densified polystyrene containing melt, and to discharge an altered hydrocarbon gas stream for further processing; and a condenser configured to receive the altered hydrocarbon gas stream from the quenching apparatus and condense out styrene to form a styrene monomer oil product.

Systems and methods for recycling waste plastics are provided, including a system for recovering styrene monomer from waste polystyrene. The system includes a mixing, heating and compacting apparatus to receive a supply of waste polystyrene and to output a densified polystyrene containing melt; a pyrolysis reactor configured to receive the densified polystyrene containing melt and a supply of recycled oligomers, pyrolyze the densified polystyrene containing melt and the recycled oligomers, and output a hydrocarbon gas stream and a solids residue stream; a quenching apparatus configured to receive the hydrocarbon gas stream output from the pyrolysis reactor and condense out oligomers for routing upstream to the pyrolysis reactor to be combined as the supply of recycled oligomers with the densified polystyrene containing melt, and to discharge an altered hydrocarbon gas stream for further processing; and a condenser configured to receive the altered hydrocarbon gas stream from the quenching apparatus and condense out styrene to form a styrene monomer oil product.

The present disclosure relates to a method of decomposing a phenolic by-product, including: a step of feeding and thermally cracking a phenolic by-product stream to and in a decomposition apparatus, recovering an active ingredient from a top discharge stream, and discharging a high-boiling substance through a bottom discharge stream; a step of pressurizing each of a side discharge stream of the decomposition apparatus and a bottom discharge stream of the decomposition apparatus; a step of mixing the pressurized side discharge stream of the decomposition apparatus and the pressurized bottom discharge stream of the decomposition apparatus with each other to form a mixed stream; and a step of passing a part of the mixed stream through a reboiler, circulating the part of the mixed stream to the decomposition apparatus, and discharging a residual mixed stream.