Provided is a continuous process for converting waste plastic into recycle for polyethylene polymerization or for normal alpha olefins. The process comprises selecting waste plastics containing polyethylene and/or polypropylene and then passing the waste plastics through a pyrolysis reactor to thermally crack at least a portion of the polyolefin waste and produce a pyrolyzed effluent. The pyrolyzed effluent is separated into offgas, a naphtha/diesel fraction, a heavy fraction, and char. The naphtha/diesel fraction is passed to a crude unit in a refinery from which is recovered a straight run naphtha fraction (C.sub.5-C.sub.8) or a propane/butane (C.sub.3-C.sub.4) fraction. The straight run naphtha fraction, or propane and butane (C.sub.3-C.sub.4) fraction, is passed to a steam cracker for ethylene production. The ethylene is converted to normal alpha olefin and/or polyethylene. Also, a heavy fraction from the pyrolysis reactor can be combined with a heavy fraction of normal alpha olefin stream recovered from the steam cracker. The combined heavy fraction and heavy fraction of normal alpha olefin stream can be passed to a wax hydrogenation zone to produce wax.

Processes for producing olefins include integration of steam cracking with a dual catalyst metathesis process. The processes include steam cracking a hydrocarbon feed to form a cracking reaction effluent containing butenes, separating the cracking reaction effluent to produce a cracking C4 effluent including normal butenes, isobutene, and 1,3-butadiene, subjecting the cracking C4 effluent to selective hydrogenation to convert 1,3-butadiene in the cracking C4 effluent to normal butenes, removing isobutene from a hydrogenation effluent to produce a metathesis feed containing normal butenes, and contacting the metathesis feed with a metathesis catalyst and a cracking catalyst directly downstream of the metathesis catalyst to produce a metathesis reaction effluent. Contacting with the metathesis catalyst causes metathesis of normal butenes to produce ethylene, propene, and C5+ olefins, and contacting with the cracking catalyst causes C5+ olefins produced through metathesis to undergo cracking reactions to produce additional propene, ethylene, or both.

Processes for producing olefins include integration of steam cracking with a dual catalyst metathesis process. The processes include steam cracking a hydrocarbon feed to form a cracking reaction effluent containing butenes, separating the cracking reaction effluent to produce a cracking C4 effluent including normal butenes, isobutene, and 1,3-butadiene, subjecting the cracking C4 effluent to selective hydrogenation to convert 1,3-butadiene in the cracking C4 effluent to normal butenes, removing isobutene from a hydrogenation effluent to produce a metathesis feed containing normal butenes, and contacting the metathesis feed with a metathesis catalyst and a cracking catalyst directly downstream of the metathesis catalyst to produce a metathesis reaction effluent. Contacting with the metathesis catalyst causes metathesis of normal butenes to produce ethylene, propene, and C5+ olefins, and contacting with the cracking catalyst causes C5+ olefins produced through metathesis to undergo cracking reactions to produce additional propene, ethylene, or both.

Processes, systems, and apparatus are provided for using a common working fluid for one or more turbines for processing a process gas and for the furnace for the pyrolysis process used to produce the process gas. The turbine(s) are operated based on a modified Allam cycle to produce power for operating one or more compressors and/or refrigerators involved in processing of the process gas while producing a reduced or minimized amount of CO.sub.2 that is released as a low-pressure gas phase product. Integrating the pyrolysis furnace with the working fluid loop can provide further benefits.

Processes, systems, and apparatus are provided for using a common working fluid for one or more turbines for processing a process gas and for the furnace for the pyrolysis process used to produce the process gas. The turbine(s) are operated based on a modified Allam cycle to produce power for operating one or more compressors and/or refrigerators involved in processing of the process gas while producing a reduced or minimized amount of CO.sub.2 that is released as a low-pressure gas phase product. Integrating the pyrolysis furnace with the working fluid loop can provide further benefits.

Processes for using pyrolysis gas as a feedstock or a co-feedstock for making a variety of chemicals, for example, circular ethylene, circular ethylene polymers and copolymers, and other circular products. In these processes, pyrolysis reactor conditions can be selected to increase or optimized the production of pyrolysis gas over pyrolysis oil, and the pyrolysis gas which is usually used as fuel or flared can be fed downstream of the steam cracker furnace for economic use to form circular chemicals. Operating parameters of the pyrolysis unit may be adjusted to increase or decrease the proportion of pyrolysis gas relative to pyrolysis liquid as a function of their relative economic values.

Processes for using pyrolysis gas as a feedstock or a co-feedstock for making a variety of chemicals, for example, circular ethylene, circular ethylene polymers and copolymers, and other circular products. In these processes, pyrolysis reactor conditions can be selected to increase or optimized the production of pyrolysis gas over pyrolysis oil, and the pyrolysis gas which is usually used as fuel or flared can be fed downstream of the steam cracker furnace for economic use to form circular chemicals. Operating parameters of the pyrolysis unit may be adjusted to increase or decrease the proportion of pyrolysis gas relative to pyrolysis liquid as a function of their relative economic values.

Provided in one embodiment 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 passing the waste plastics through a pyrolysis reactor to thermally crack at least a portion of the polyolefin waste and produce a pyrolyzed effluent. The pyrolyzed effluent is separated into offgas, a pyrolysis oil and optionally wax comprising a naphtha/diesel and heavy fraction, and char. The pyrolysis oil and wax is passed to a refinery FCC unit from which a liquid petroleum gas C.sub.3-C.sub.5 olefin/paraffin mixture fraction is recovered. The liquid petroleum gas C.sub.3-C.sub.5 olefin/paraffin mixture fraction is passed to a refinery alkylation unit, with a propane and butane fraction recovered from the alkylation unit. The propane and butane fraction is then passed to a steam cracker for ethylene production. In another embodiment, a naphtha fraction (C.sub.5-C.sub.8) is recovered from the alkylation unit and passed to the steam cracker. In another embodiment, a propane/propylene fraction (C.sub.3-C.sub.3) is recovered from the FCC and passed to the steam cracker.

Provided in one embodiment 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 passing the waste plastics through a pyrolysis reactor to thermally crack at least a portion of the polyolefin waste and produce a pyrolyzed effluent. The pyrolyzed effluent is separated into offgas, a pyrolysis oil and optionally wax comprising a naphtha/diesel and heavy fraction, and char. The pyrolysis oil and wax is passed to a refinery FCC unit from which a liquid petroleum gas C.sub.3-C.sub.5 olefin/paraffin mixture fraction is recovered. The liquid petroleum gas C.sub.3-C.sub.5 olefin/paraffin mixture fraction is passed to a refinery alkylation unit, with a propane and butane fraction recovered from the alkylation unit. The propane and butane fraction is then passed to a steam cracker for ethylene production. In another embodiment, a naphtha fraction (C.sub.5-C.sub.8) is recovered from the alkylation unit and passed to the steam cracker. In another embodiment, a propane/propylene fraction (C.sub.3-C.sub.3) is recovered from the FCC and passed to the steam cracker.

A continuous process for converting waste plastic into recycle for polypropylene polymerization is provided. The process integrates refinery operations to provide an effective and efficient recycle process. The process comprises selecting waste plastics containing polyethylene and polypropylene and then passing the waste plastics through a pyrolysis reactor to thermally crack at least a portion of the polyolefin waste and produce a pyrolyzed effluent. The pyrolyzed effluent is separated into offgas, a naphtha/diesel fraction, a heavy fraction, and char. The naphtha/diesel fraction is passed to a refinery FCC unit, from which is recovered a liquid petroleum gas C.sub.3 olefin/paraffin mixture. The C.sub.3 paraffins and C.sub.3 olefins are separated into different fractions with a propane/propylene splitter. The C.sub.3 olefin fraction is passed to a propylene polymerization reactor. The C.sub.3 paraffin fraction is optionally passed to a dehydrogenation unit to produce additional propylene and then the resulting C.sub.3 olefin is passed to a propylene polymerization reactor. The heavy fraction of pyrolyzed oil is passed to an isomerization dewaxing unit to produce a lubricating base oil.