Process for preparing polymers from waste plastic feedstocks

Abstract

The invention relates to a method for producing a polymer from a waste plastic feedstock, comprising the following steps in sequence: (a) providing a hydrocarbon stream A obtained by processing the waste plastic feedstock; (b) optionally providing a hydrocarbon stream B; (c) supplying a feed C comprising a portion of the hydrocarbon stream A and a portion of the hydrocarbon stream B to a thermal cracking furnace comprising a cracking coil; (d) performing a thermal cracking operation in the presence of steam to obtain a cracked hydrocarbon stream D; (e) feeding the cracked hydrocarbon stream D to a separation unit; (f) carrying out a separation operation in a separation unit to obtain a product stream E comprising monomers; (g) supplying the product stream E to the polymerization reactor; and (h) performing a polymerization reaction in the polymerization reactor to obtain a polymer. The method of the present invention allows optimization of the amount of waste plastic material that can be returned to the polymer produced as a result of the method.

Description

[0001] This application is a divisional application of Chinese patent application No. 202080010581.0, filed on January 24, 2020, entitled "Method for preparing polymers from waste plastic raw materials".

[0002] This invention relates to a method for preparing polymers from products derived from waste plastic raw materials. Specifically, this invention relates to the production of polymers from products derived from waste plastic raw materials that have improved carbon efficiency for such polymers.

[0003] Currently, the disposal of plastic materials as waste is causing growing environmental problems. With the increasing global population and per capita plastic consumption, the amount of plastic materials generated as waste, whether from industrial applications or consumer use, has reached a level where profound changes in disposal methods are rapidly becoming necessary. Specifically, it is very encouraging that such changes will also help reduce harmful environmental problems, such as fossil carbon utilization and carbon emissions into the atmosphere.

[0004] Currently, in many cases, waste plastics are disposed of through incineration, which leads to atmospheric carbon emissions, dumping in landfills, or even littering on land and at sea. Such undesirable waste disposal is increasingly facing public opposition. Therefore, one goal of industrial development is to find ways to address these objections by processing these waste plastics.

[0005] One way to achieve this goal is to process waste plastics into feedstock via chemical conversion methods, which can then be reused in the production of recycled plastics. This approach not only allows for the reuse of waste, addressing the aforementioned issues, but it can also serve as a substitute for conventional feedstocks used in plastics production.

[0006] As the most common route to date, a specific route for producing plastics involves first processing petroleum or gas derivatives into the building blocks of plastics, and then further converting these building blocks into plastics via polymerization. A typical example involves preparing these building blocks (also called monomers) via the steam cracking of petroleum derivatives in the naphtha range. These monomers include particularly low-grade mono- and diene compounds such as ethylene and propylene, followed by other valuable chemical building blocks such as aromatics and oxygen-containing products. These olefin compounds are polymerized on a very large scale into polyolefin materials, particularly polyethylene and polypropylene.

[0007] Because polymer production via this route represents a major portion of global plastics production, and production capacity continues to grow annually, this route is particularly well-suited for utilizing waste plastic-based feedstreams to convert them into new polymeric materials. Such a route would allow for the provision of a means to transform plastics into plastics, also known as circular plastics processing.

[0008] In order to process waste plastics as feed for steam pyrolysis operations, it must be supplied to the steam pyrolysis unit in such a way that the pyrolysis process can operate under conditions of maximum efficiency and sustainability.

[0009] In the context of this paper, high pyrolysis efficiency refers to pyrolysis occurring under conditions that maximize the production of monomers for polymers that are part of the range of products generated in a steam pyrolysis unit. Steam pyrolysis involves subjecting a feed stream of hydrocarbons with mixed chemical structures to high temperatures at high flow rates for a period of time. As a result of these conditions, compounds in the feed stream undergo thermal degradation, yielding a range of desired compounds that can be chemically applied directly or via other chemical conversion methods.

[0010] In the context of this invention, sustainable steam pyrolysis conditions refer to steam pyrolysis carried out under such processing conditions and feed stream composition that the operating duration of the pyrolysis method (which is a continuous method in commercial operations) is as long as possible before contamination, such as coke (which deposits on the inside of tubes typically used in steam pyrolysis units, requiring forced shutdown and cleaning of reactor tubes according to the prior art). This operating duration depends primarily on the feed composition and pyrolysis conditions and is ideally as long as possible to make facility operation economical.

[0011] The monomers obtained as part of the product composition formed in the steam cracking process are separated to the desired purity by a separation step and then converted into polymer products by a polymerization process.

[0012] Now, one objective of the present invention is to provide a method that can utilize carbon from waste plastic streams to produce polymers with maximum efficiency.

[0013] According to the present invention, this is now achieved by a method for producing polymers from waste plastic raw materials, the method comprising the following steps in sequence:

[0014] (a) Provide hydrocarbon stream A obtained by processing waste plastic raw materials;

[0015] (b) Optionally provide hydrocarbon stream B;

[0016] (c) Feed C, which includes a portion of hydrocarbon stream A and a portion of hydrocarbon stream B, is supplied to a thermal cracking furnace containing a cracking coil.

[0017] (d) To obtain a cracked hydrocarbon stream D by performing a thermal cracking operation in the presence of steam;

[0018] (e) Supply the pyrolyzed hydrocarbon stream D to the separation unit;

[0019] (f) A separation operation is performed in the separation unit to obtain a product stream E containing monomers;

[0020] (g) Supplying product stream E to the polymerization reactor; and

[0021] (h) Polymerization reaction is carried out in a polymerization reactor to obtain a polymer.

[0022] The method of this invention allows for the optimization of the amount of waste plastic material that can be returned as a result of the method to the polymer produced. The higher the amount, i.e., the higher the amount of chemical building blocks present in the waste plastic material to be converted into the polymer produced, the better the sustainability footprint of the method.

[0023] Preferably, in step (c), the feed C contains ≤50.0 wt%, preferably ≥0.1 and ≤25.0 wt%, more preferably ≥5.0 and ≤25.0 wt%, and even more preferably ≥10.0 and ≤25.0 wt% of hydrocarbon stream A, wherein the hydrocarbon stream A is obtained as a liquid stream from the pyrolysis unit.

[0024] The method of the present invention allows waste plastic materials to be converted into polymer products.

[0025] The waste plastic raw material used to produce hydrocarbon stream A in the method of the present invention may, for example, contain polyolefins, polyesters, thermoplastic elastomers, polyvinyl chloride, polystyrene, or polycarbonate.

[0026] The waste plastic raw material that can be used to produce hydrocarbon stream A can be a mixture comprising polyolefins, polyesters, thermoplastic elastomers, polyvinyl chloride, polystyrene, or polycarbonate. Specifically, the waste plastic raw material that can be used to produce hydrocarbon stream A can be a mixture comprising >25.0 wt% polyolefins relative to the total weight of the waste plastic raw material. Preferably, the waste plastic raw material can contain >40.0 wt% polyolefins, more preferably >50.0 wt%, even more preferably >60.0 wt%, or >70.0 wt%. The waste plastic raw material can contain a portion of non-thermoplastic materials. Such non-thermoplastic materials can be, for example, hydrocarbon-based materials such as rubber materials, but can also be materials including paper, sand, and soil. An advantage of the present invention is that waste plastic raw materials containing up to 10 wt%, preferably up to 5.0 wt%, more preferably up to 2.0 wt% of materials selected from paper, sand, and soil, and combinations thereof, can be used in methods for preparing polyethylene. This allows such raw materials to be processed without a cleaning process (which would require the use of solvents or cleaning agents).

[0027] For example, waste plastic raw materials may contain the following components in a total weight of ≤10.0 wt% relative to the total weight of waste plastic raw materials: glass, paper, metal, cardboard, compostable waste, wood, stone, textiles, rubber materials and superabsorbent sanitary products.

[0028] Waste plastic raw materials may, for example, contain ≥90.0 wt% polymeric material relative to the total weight of the waste plastic raw materials.

[0029] Waste plastic raw materials may, for example, contain a certain amount of polyester. For example, the waste plastic raw material may contain <20.0 wt% polyester, preferably <15.0 wt%, more preferably <10.0 wt%, even more preferably <5.0 wt%, and even more preferably <2.0 wt%. In some embodiments, the waste plastic raw material may be polyester-free.

[0030] One specific type of polyester (which can typically be present in waste plastic feedstock used in the method of the present invention, for example, for preparing hydrocarbon stream A) is polyethylene terephthalate (also referred to as PET). The waste plastic feedstock may, for example, contain a certain amount of PET. For example, the waste plastic feedstock may contain <20.0 wt% PET, preferably <15.0 wt%, more preferably <10.0 wt%, even more preferably <5.0 wt%, and even more preferably <2.0 wt%. In some embodiments, the waste plastic feedstock may be PET-free.

[0031] Polyesters such as PET contain oxygen atoms in their polymer chains. The presence of compounds containing oxygen atoms in hydrocarbon stream A is somewhat limited because excessive oxygen atoms in the compounds supplied to the pyrolysis furnace can lead to problems including scaling and corrosion in the downstream processing of the pyrolyzed hydrocarbon stream D leaving the furnace. Therefore, it is desirable to control or even minimize the amount of oxygen-containing polymers in the waste plastic feedstock used to prepare hydrocarbon stream A.

[0032] Waste plastic raw materials may, for example, contain a certain amount of polyamide. For example, waste plastic raw materials may contain <20.0 wt% polyamide, preferably <15.0 wt%, more preferably <10.0 wt%, even more preferably <5.0 wt%, and even more preferably <2.0 wt%. In some embodiments, waste plastic raw materials may not contain polyamide.

[0033] Specific types of polyamides (which can typically be present in waste plastic feedstocks used in the method of the present invention, for example, for preparing hydrocarbon stream A) are polyamide 6 and polyamide 6,6 (which can be referred to as PA6 and PA66, respectively). The waste plastic feedstock may, for example, contain a certain amount of PA6 or PA66. For example, the waste plastic feedstock may contain a total of <20.0 wt% PA6 and PA66, preferably <15.0 wt%, more preferably <10.0 wt%, even more preferably <5.0 wt%, and even more preferably <2.0 wt%. In some embodiments, the waste plastic feedstock may be free of PA6 and / or PA66.

[0034] Waste plastic raw materials may, for example, contain a certain amount of polyvinyl chloride, which can also be referred to as PVC. For example, waste plastic raw materials may contain <5.0 wt% PVC, preferably <2.0 wt%, more preferably <1.0 wt%, even more preferably <0.5 wt%, and even more preferably <0.1 wt%. In some embodiments, waste plastic raw materials may be PVC-free.

[0035] Waste plastic materials may include, for example:

[0036] • <20.0 wt%, preferably <10.0 wt% polyester; and / or

[0037] • <20.0 wt%, preferably <10.0 wt% polyamide; and / or

[0038] • <2.0wt%, preferably <1.0wt% polyvinyl chloride,

[0039] This is relative to the total weight of the polymeric materials in the waste plastic raw material.

[0040] The percentages of polyester, polyamide, and PVC in the given waste plastic raw materials are understood as the weight percentage of the total weight of the polymeric materials present in the waste plastic raw materials.

[0041] Waste plastic raw materials may further contain a certain amount of moisture, for example, waste plastic raw materials may contain up to 20.0 wt% moisture, preferably up to 10.0 wt%, more preferably up to 5.0 wt%.

[0042] Preferably, the initial boiling point of hydrocarbon stream A is >25°C and the final boiling point is <350°C, wherein the initial boiling point and the final boiling point are determined according to ASTM D86 (2012).

[0043] The initial boiling point of hydrocarbon stream A can be, for example, >25°C, preferably >30°C, more preferably >35°C, and even more preferably >40°C. The initial boiling point of hydrocarbon stream A can be, for example, <100°C, preferably <90°C, more preferably <80°C, and even more preferably <70°C, or <60°C, or <50°C. The initial boiling point of hydrocarbon stream A can be, for example, >25°C and <100°C, preferably >35°C and <80°C.

[0044] The final boiling point of hydrocarbon stream A can be, for example, <350°C, preferably <325°C, more preferably <300°C, even more preferably <275°C, even more preferably <250°C, or <225°C, or <200°C. The final boiling point of hydrocarbon stream A can be, for example, >150°C, preferably >175°C, more preferably >200°C, even more preferably >250°C, or >275°C, or >300°C. The final boiling point of hydrocarbon stream A can be, for example, >150°C and <350°C, preferably >200°C and <325°C, more preferably >200°C and <300°C.

[0045] Hydrocarbon stream A is a material stream obtained by processing waste plastic feedstock. For example, hydrocarbon stream A can be obtained by processing waste plastic stream in a pyrolysis unit.

[0046] Such a pyrolysis unit can be a continuously operating unit, wherein a stream of waste plastic is continuously supplied to the unit, and a liquid stream containing at least pyrolysis products is continuously obtained from the unit. Alternatively, the pyrolysis unit can be operated intermittently, wherein a certain amount of waste plastic is introduced into the unit, subjected to pyrolysis conditions, and subsequently a liquid stream containing at least pyrolysis products is obtained from the unit.

[0047] The pyrolysis process in the pyrolysis unit can be a low-severity pyrolysis process or a high-severity pyrolysis process. In a low-severity pyrolysis process, pyrolysis can be carried out at a temperature of ≥250℃ and ≤450℃, preferably ≥275℃ and ≤425℃, and more preferably ≥300℃ and ≤400℃. Optionally, the pyrolysis process can be a high-severity process, carried out at a temperature of ≥450℃ and ≤750℃, preferably ≥500℃ and ≤700℃, and more preferably ≥550℃ and ≤650℃.

[0048] The pyrolysis process can be a catalytic process. In such a pyrolysis process, for example, a certain amount of zeolite catalyst, such as ZSM-5 zeolite catalyst, can be used. In such a pyrolysis process, for example, a certain amount of spent FCC catalyst can be used. Specifically, a composition containing a certain amount of ZSM-5 catalyst and a certain amount of spent FCC catalyst can be used. For example, a composition containing a certain amount of ZSM-5 and a certain amount of spent FCC catalyst can be used, wherein the weight ratio of spent FCC catalyst to ZSM-5 catalyst is 0.5-5.0, for example 1.0-3.0.

[0049] A liquid hydrocarbon stream can be obtained from the pyrolysis process. The liquid hydrocarbon stream may, for example, contain a certain amount of n-chain alkanes, a certain amount of iso-chain alkanes, a certain amount of alkenes, a certain amount of cycloalkanes, and / or a certain amount of aromatics.

[0050] Hydrocarbon stream A may, for example, contain ≥25.0 and ≤80.0 wt% of n-chain alkanes relative to the total weight of hydrocarbon stream A. Preferably, hydrocarbon stream A contains ≥25.0 and ≤70.0 wt% of n-chain alkanes, more preferably ≥25.0 and ≤50.0 wt%.

[0051] Hydrocarbon stream A may, for example, contain ≥5.0 and ≤40.0 wt% of isoparaffins relative to the total weight of hydrocarbon stream A. Preferably, hydrocarbon stream A contains ≥5.0 and ≤30.0 wt% of isoparaffins, more preferably ≥7.5 wt% and ≤25.0 wt%.

[0052] Hydrocarbon stream A may, for example, contain ≤50.0 wt% olefins relative to the total weight of hydrocarbon stream A. Preferably, hydrocarbon stream A contains ≤40.0 wt% olefins, more preferably ≤35.0 wt%, and even more preferably ≤30.0 wt%.

[0053] Hydrocarbon stream A may, for example, contain ≥25.0 and ≤50.0 wt% of olefins relative to the total weight of hydrocarbon stream A. Preferably, hydrocarbon stream A contains ≥25.0 and ≤40.0 wt% of olefins, more preferably ≥25.0 and ≤35.0 wt%.

[0054] Hydrocarbon stream A may, for example, contain ≥5.0 and ≤20.0 wt% cycloalkanes relative to the total weight of hydrocarbon stream A. Preferably, hydrocarbon stream A contains ≥5.0 and ≤15.0 wt% cycloalkanes, more preferably ≥7.5 wt% and ≤15.0 wt%.

[0055] Hydrocarbon stream A may, for example, contain ≥5.0 and ≤15.0 wt% aromatics relative to the total weight of hydrocarbon stream A. Preferably, hydrocarbon stream A contains ≥5.0 and ≤12.5 wt% aromatics, more preferably ≥7.5 wt% and ≤12.5 wt%.

[0056] Hydrocarbon stream A may include, for example:

[0057] • ≥25.0 and ≤50.0 wt%, preferably ≥25.0 and ≤40.0 wt%, more preferably ≥25.0 and ≤35.0 wt% of n-chain alkanes; and / or

[0058] • ≥5.0 and ≤20.0 wt%, preferably ≥5.0 and ≤15.0 wt%, more preferably ≥7.5 and ≤15.0 wt% of isoparaffins; and / or

[0059] • ≥25.0 and ≤50.0 wt%, preferably ≥25.0 and ≤40.0 wt%, more preferably ≥25.0 and ≤35.0 wt% of olefins; and / or

[0060] • ≥5.0 and ≤20.0 wt%, preferably ≥5.0 and ≤15.0 wt%, more preferably ≥7.5 and ≤15.0 wt% of cycloalkanes; and / or

[0061] • ≥5.0 and ≤15.0 wt%, preferably ≥5.0 and ≤12.5 wt%, more preferably ≥7.5 and ≤12.5 wt% of aromatics.

[0062] Relative to the total weight of hydrocarbon stream A.

[0063] In the context of this invention, chlorine atom content is understood as the total weight of chlorine atoms present in the molecules of the hydrocarbon stream, as a fraction of the total weight of the hydrocarbon stream. Similarly, nitrogen atom content is understood as the total weight of nitrogen atoms present in the molecules of the hydrocarbon stream, as a fraction of the total weight of the hydrocarbon stream.

[0064] Hydrocarbon stream A may, for example, contain a certain amount of contaminants. For instance, hydrocarbon stream A may contain a certain amount of compounds containing chlorine atoms. The amount of compounds containing chlorine atoms can be expressed as the chlorine atom content of hydrocarbon stream A. For example, the chlorine atom content of hydrocarbon stream A may be <800 ppm by weight, as determined according to ASTM UOP 779-08, preferably <700 ppm, more preferably <600 ppm, even more preferably <500 ppm, even more preferably <400 ppm.

[0065] Hydrocarbon stream A may contain a certain amount of compounds containing nitrogen atoms. The amount of compounds containing nitrogen atoms can be expressed as the nitrogen atom content of hydrocarbon stream A. For example, the nitrogen atom content of hydrocarbon stream A may be <1600 ppm by weight, as determined according to ASTM D5762 (2012), preferably <1500 ppm, more preferably <1400 ppm, even more preferably <1300 ppm, even more preferably <1200 ppm, or <1100 ppm, or <1000 ppm. For example, the nitrogen atom content of hydrocarbon stream A may be <100 ppm by weight, as determined according to ASTM D4629 (2017).

[0066] Hydrocarbon stream A may contain a certain amount of compounds with olefinic unsaturation. The amount of olefinic unsaturation is indicated by the bromine value of the hydrocarbon stream. The bromine value represents the amount of bromine reacting with 100g of hydrocarbon sample when tested under the conditions of ASTM D1159-07 (2012), in grams. For example, the bromine value of hydrocarbon stream A used in the method of the present invention may be <100, preferably <95, more preferably <90, and even more preferably <85.

[0067] Preferably, the initial boiling point of hydrocarbon stream B is >25°C and the final boiling point is <350°C, wherein the initial boiling point and the final boiling point are determined according to ASTM D86 (2012).

[0068] The initial boiling point of hydrocarbon stream B can be, for example, >25°C, preferably >30°C, more preferably >35°C, and even more preferably >40°C. The initial boiling point of hydrocarbon stream B can be, for example, <100°C, preferably <90°C, more preferably <80°C, and even more preferably <70°C, or <60°C, or <50°C.

[0069] The final boiling point of hydrocarbon stream B can be, for example, <350°C, preferably <325°C, more preferably <300°C, even more preferably <275°C, even more preferably <250°C, or <225°C, or <200°C. The final boiling point of hydrocarbon stream B can be, for example, >150°C, preferably >175°C, more preferably >200°C, even more preferably >250°C, or >275°C, or >300°C.

[0070] Hydrocarbon stream B may, for example, contain ≥25.0 and ≤80.0 wt% of n-chain alkanes relative to the total weight of hydrocarbon stream B. Preferably, hydrocarbon stream B contains ≥25.0 and ≤70.0 wt% of n-chain alkanes, more preferably ≥25.0 and ≤50.0 wt%.

[0071] Hydrocarbon stream B may, for example, contain ≥5.0 and ≤40.0 wt% of isoparaffins relative to the total weight of hydrocarbon stream B. Preferably, hydrocarbon stream B contains ≥5.0 and ≤30.0 wt% of isoparaffins, more preferably ≥7.5 wt% and ≤25.0 wt%.

[0072] Hydrocarbon stream B may, for example, contain ≤2.0 wt% olefins relative to the total weight of hydrocarbon stream B. Preferably, hydrocarbon stream B contains ≤1.5 wt% olefins, more preferably ≤1.0 wt%, and even more preferably ≤0.5 wt%.

[0073] Hydrocarbon stream B may, for example, contain ≥0.01 and ≤2.0 wt% of olefins relative to the total weight of hydrocarbon stream B. Preferably, hydrocarbon stream B contains ≥0.01 and ≤1.5 wt% of olefins, more preferably ≥0.01 and ≤1.0 wt%.

[0074] Hydrocarbon stream B may, for example, contain ≥5.0 and ≤40.0 wt% cycloalkanes relative to the total weight of hydrocarbon stream B. Preferably, hydrocarbon stream B contains ≥5.0 and ≤30.0 wt% cycloalkanes, more preferably ≥7.5 wt% and ≤25.0 wt%.

[0075] Hydrocarbon stream B may, for example, contain ≥5.0 and ≤15.0 wt% aromatics relative to the total weight of hydrocarbon stream B. Preferably, hydrocarbon stream B contains ≥5.0 and ≤12.5 wt% aromatics, more preferably ≥7.5 wt% and ≤12.5 wt%.

[0076] Hydrocarbon stream B may include, for example:

[0077] • ≥25.0 and ≤80.0 wt%, preferably ≥25.0 and ≤70.0 wt%, more preferably ≥25.0 and ≤50.0 wt% of n-chain alkanes; and / or

[0078] • ≥5.0 and ≤40.0 wt%, preferably ≥5.0 and ≤30.0 wt%, more preferably ≥7.5 and ≤25.0 wt% of isoparaffins; and / or

[0079] • ≥0.01 and ≤2.0 wt%, preferably ≥0.01 and ≤1.5 wt%, more preferably ≥0.01 and ≤1.0 wt% of olefins; and / or

[0080] • ≥5.0 and ≤40.0 wt%, preferably ≥5.0 and ≤30.0 wt%, more preferably ≥7.5 and ≤25.0 wt% of cycloalkanes; and / or

[0081] • ≥5.0 and ≤15.0 wt%, preferably ≥5.0 and ≤12.5 wt%, more preferably ≥7.5 and ≤12.5 wt% of aromatics.

[0082] Relative to the total weight of hydrocarbon stream B.

[0083] Olefin fraction F in feed C O,C The calculation can be performed as follows:

[0084] F O,C =F O,A *FA,C +F O,B *F B,C

[0085] in:

[0086] ·F O,C It is the olefin weight fraction in feed C, expressed in wt%, relative to the total weight of feed C;

[0087] ·F O,A It is the olefin weight fraction in hydrocarbon stream A, expressed in wt%, relative to the total weight of hydrocarbon stream A;

[0088] ·F O,B It is the olefin weight fraction in hydrocarbon stream B, expressed in wt%, relative to the total weight of hydrocarbon stream B;

[0089] ·F A,C It is the weight fraction of hydrocarbon stream A in feed C, relative to the total weight of feed C; and

[0090] ·F B,C It is the weight fraction of hydrocarbon stream B in feed C, relative to the total weight of feed C.

[0091] Preferably, the olefin fraction F in feed C is [missing information]. O,C ≤2.0wt%, preferably ≤1.8wt%, more preferably ≤1.6wt%, and even more preferably ≤1.5wt%, relative to the total weight of feed C.

[0092] The feed C supplied to the pyrolysis furnace comprises a portion of hydrocarbon stream A and optionally a portion of hydrocarbon stream B.

[0093] Feed C can be supplied to the pyrolysis furnace via one or more inlets, wherein a portion of hydrocarbon stream A and a portion of hydrocarbon stream B are combined before entering the pyrolysis furnace. Alternatively, feed C can be supplied to the pyrolysis furnace in such a manner that a portion of hydrocarbon stream A and a portion of hydrocarbon stream B enter the furnace via separate inlets.

[0094] Feed C can be, for example, a premixed composition comprising a portion of hydrocarbon stream A and a portion of hydrocarbon stream B, wherein feed C is supplied to the pyrolysis furnace as a mixture via one or more inlets, or alternatively, the total amount of hydrocarbon streams A and B, wherein feed C is supplied to the pyrolysis furnace as separate streams A and B, for each stream via one or more inlets.

[0095] In some embodiments of the invention, the hydrocarbon stream A may be a liquid stream from a pyrolysis unit. Such a liquid stream from a pyrolysis unit may, for example, be heat-treated before the method of the invention is introduced.

[0096] In the method according to the invention, the pyrolysis step (d) can be carried out using a feed C comprising a smaller portion of hydrocarbon stream A. For example, the feed C supplied to the pyrolysis furnace may contain hydrocarbon stream A at a weight percentage of <95.0 wt%, or <90.0 wt%, or <75.0 wt%, or <50.0 wt%, or <25.0 wt%, or <20.0 wt%, or <15.0 wt%, or <10.0 wt%, or <5.0 wt% relative to the total weight of feed C. For example, the feed C supplied to the pyrolysis furnace may contain hydrocarbon stream A at a weight percentage of >2.0 wt%, or >3.0 wt%, or >4.0 wt%, or >5.0 wt%, or >10.0 wt%, or >20.0 wt%, or >30.0 wt%, or >40.0 wt%, or >50.0 wt%, or >75.0 wt% relative to the total weight of feed C. Optionally, feed C may consist of hydrocarbon stream A.

[0097] For example, feed C may contain >5.0 wt% of hydrocarbon stream B relative to the total weight of feed C, preferably >15.0 wt%, or >25.0 wt%, or >50.0 wt%, or >75.0 wt%, or >80.0 wt%, or >90.0 wt%.

[0098] The operation of this method is advantageous because it allows the use of hydrocarbon stream A, obtained directly from the pyrolysis unit as a liquid stream, without further treatment before supplying it to the pyrolysis furnace. This allows waste plastics to be converted as a proportionate feed to the pyrolysis furnace without subjecting the liquid products of the pyrolysis unit to processing steps, thereby contributing to the economic efficiency of the method for converting waste plastics into new virgin polymers.

[0099] Following the pyrolysis operation (d), a pyrolyzed hydrocarbon stream D is obtained from the pyrolysis furnace. The composition of the pyrolyzed hydrocarbon stream D depends on the composition of the feed stream C. Typically, the pyrolyzed hydrocarbon stream contains monoolefins such as ethylene, propylene, butene, dienes such as butadiene, and aromatics. Due to the use of optimized methods, a high monomer content in the pyrolyzed hydrocarbon stream D is desirable.

[0100] After leaving the pyrolysis furnace, the pyrolyzed hydrocarbon stream D is supplied to the separation unit. In the separation unit, separation operations are performed to obtain a product stream E containing the desired monomers.

[0101] Following the separation operation (f), the resulting product stream E is supplied to a polymerization reactor. In this reactor, a polymerization reaction (h) is carried out to obtain a polymer.

[0102] In one embodiment, the present invention also relates to a method for converting waste plastic raw materials, which includes the following steps in sequence:

[0103] (a) Provide hydrocarbon stream A obtained by processing waste plastic raw materials;

[0104] (b) Provide hydrocarbon stream B;

[0105] (c) Feed C, which includes a portion of hydrocarbon stream A and a portion of hydrocarbon stream B, is supplied to a thermal cracking furnace containing a cracking coil.

[0106] (d) A thermal cracking operation is performed in the presence of steam to obtain a cracked hydrocarbon stream D.

[0107] In another embodiment, the method further includes the following steps after step (d):

[0108] (e) The cracked hydrocarbon stream D is supplied to the separation unit.

[0109] In another embodiment, the method further includes the following steps after step (e):

[0110] (f) A separation operation is performed in the separation unit to obtain a product stream E containing monomers.

[0111] In another embodiment, the method further includes the following steps in sequence after step (f):

[0112] (g) Supplying product stream E to the polymerization reactor; and

[0113] (h) Polymerization reaction is carried out in a polymerization reactor to obtain a polymer.

Claims

1. A method for producing polymers from waste plastic raw materials, the method comprising the following steps in sequence: (a) Provide hydrocarbon stream A obtained by processing waste plastic raw materials; (b) Provide hydrocarbon stream B; (c) Feed C, which includes a portion of hydrocarbon stream A and a portion of hydrocarbon stream B, is supplied to a thermal cracking furnace containing a cracking coil. (d) To obtain a cracked hydrocarbon stream D by performing a thermal cracking operation in the presence of steam; (e) Supply the pyrolyzed hydrocarbon stream D to the separation unit; (f) A separation operation is performed in the separation unit to obtain a product stream E containing monomers; (g) Supply the product stream E to the polymerization reactor; and (h) A polymerization reaction is carried out in the polymerization reactor to obtain a polymer.

2. The method according to claim 1, wherein the initial boiling point of hydrocarbon stream A is >25°C and the final boiling point is <350°C, wherein the initial boiling point and the final boiling point are determined according to ASTM D86 (2012).

3. The method according to any one of claims 1-2, wherein the chlorine atom content of hydrocarbon stream A is <800 ppm by weight as determined by ASTM UOP779-08.

4. The method according to any one of claims 1-3, wherein the nitrogen atom content of hydrocarbon stream A is <1600 ppm by weight as determined according to ASTM D5762 (2012), preferably <100 ppm by weight as determined according to ASTM D4629 (2017).

5. The method according to any one of claims 1-4, wherein the bromine value of hydrocarbon stream A is <100 as determined by ASTM D1159-07(2012).

6. The method according to any one of claims 1-5, wherein in step (c), the feed C comprises ≤50.0 wt%, preferably ≥0.1 and ≤25.0 wt% of hydrocarbon stream A, preferably wherein the hydrocarbon stream A is obtained as a liquid stream from the pyrolysis unit.

7. The method according to any one of claims 1-6, wherein processing the waste plastic raw material to obtain hydrocarbon stream A includes pyrolysis treatment.

8. The method according to any one of claims 1-7, wherein the waste plastic raw material comprises ≥90.0 wt% polymeric material relative to the total weight of the waste plastic raw material.

9. The method according to any one of claims 1-8, wherein the waste plastic raw material comprises: • <20.0 wt%, preferably <10.0 wt% polyester; and / or • <20.0 wt%, preferably <10.0 wt% polyamide; and / or • <2.0wt%, preferably <1.0wt% polyvinyl chloride, Relative to the total weight of polymeric materials in the waste plastic raw material.

10. The method according to any one of claims 1-9, wherein the waste plastic raw material comprises, in a total weight of ≤10.0 wt% of the following components: glass, paper, metal, cardboard, compostable waste, wood, stone, textiles, rubber materials and superabsorbent sanitary products.

11. The method according to any one of claims 1-10, wherein the hydrocarbon stream A comprises: • ≥25.0 and ≤50.0 wt%, preferably ≥25.0 and ≤40.0 wt%, more preferably ≥25.0 and ≤35.0 wt% of n-chain alkanes; and / or • ≥5.0 and ≤20.0 wt%, preferably ≥5.0 and ≤15.0 wt%, more preferably ≥7.5 and ≤15.0 wt% of isoparaffins; and / or • ≥25.0 and ≤50.0 wt%, preferably ≥25.0 and ≤40.0 wt%, more preferably ≥25.0 and ≤35.0 wt% of olefins; and / or • ≥5.0 and ≤20.0 wt%, preferably ≥5.0 and ≤15.0 wt%, more preferably ≥7.5 and ≤15.0 wt% of cycloalkanes; and / or • ≥5.0 and ≤15.0 wt%, preferably ≥5.0 and ≤12.5 wt%, more preferably ≥7.5 and ≤12.5 wt% of aromatics. Relative to the total weight of hydrocarbon stream A.

12. The method according to any one of claims 1-11, wherein the hydrocarbon stream B comprises: • ≥25.0 and ≤80.0 wt%, preferably ≥25.0 and ≤70.0 wt%, more preferably ≥25.0 and ≤50.0 wt% of n-chain alkanes; and / or • ≥5.0 and ≤40.0 wt%, preferably ≥5.0 and ≤30.0 wt%, more preferably ≥7.5 and ≤25.0 wt% of isoparaffins; and / or • ≥0.01 and ≤2.0 wt%, preferably ≥0.01 and ≤1.5 wt%, more preferably ≥0.01 and ≤1.0 wt% of olefins; and / or • ≥5.0 and ≤40.0 wt%, preferably ≥5.0 and ≤30.0 wt%, more preferably ≥7.5 and ≤25.0 wt% of cycloalkanes; and / or • ≥5.0 and ≤15.0 wt%, preferably ≥5.0 and ≤12.5 wt%, more preferably ≥7.5 and ≤12.5 wt% of aromatics. Relative to the total weight of hydrocarbon stream B.

13. The method according to any one of claims 1-12, wherein the feed C comprises an olefin fraction F relative to the total weight of the feed C. O,C ≤2.0wt%, preferably ≤1.5wt%.