Circular economy for waste plastics to polyethylene and lubricating oil via crude and isomerization dewaxing units

Abstract

To provide a continuous process for converting waste plastics for recycling for polyethylene polymerization.SOLUTION: In one embodiment, 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 naphtha / diesel fraction, a heavy fraction, and char. The naphtha / diesel fraction is passed to a crude unit distillation column in a refinery where a straight run naphtha (C5-C8) fraction or a propane / butane (C3-C4) fraction is recovered. The straight run naphtha fraction (C5-C8) or the propane / butane (C3-C4) fraction is passed to a steam cracker for ethylene production. The heavy fraction from the pyrolysis unit can also be passed to an isomerization dewaxing unit to produce a base oil.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] (background) The world has witnessed extremely rapid growth in plastic production. According to PlasticsEurope Market Research Group, global plastic production was 335 million tonnes in 2016, 348 million tonnes in 2017, and 359 million tonnes in 2018. According to McKinsey & Company, global plastic waste was estimated at approximately 260 million tonnes per year in 2016 and is projected to reach 460 million tonnes per year by 2030 if the current trajectory continues. [Background technology]

[0002] Single-use plastic waste is becoming an increasingly significant environmental issue. At present, there appear to be few options for recycling polyethylene and polypropylene waste plastics into value-added chemical and fuel products. Currently, only small amounts of polyethylene and polypropylene are recycled via chemical recycling, and the recycled and cleaned polymer pellets are thermally cracked in pyrolysis units to produce fuels (naphtha, diesel), steam cracker feedstock, or slack wax.

[0003] Processes for converting waste plastics into hydrocarbon lubricants are known. For example, U.S. Patent No. 3,845,157 discloses the cracking of waste or virgin polyolefins to form gaseous products, such as ethylene / olefin copolymers, which are further processed to produce synthetic hydrocarbon lubricants. U.S. Patent No. 4,642,401 discloses the heating of pulverized polyolefin waste at temperatures between 150 and 500°C and pressures between 20 and 300 bar to produce liquid hydrocarbons. U.S. Patent No. 5,849,964 discloses a process for depolymerizing waste plastic materials into volatile and liquid phases. The volatile phase is separated into a gas phase and a condensate. The liquid, condensate, and gas phases are refined into liquid fuel components using standard refining techniques. U.S. Patent No. 6,143,940 discloses a procedure for converting waste plastics into heavy wax compositions. U.S. Patent No. 6,150,577 discloses a process for converting waste plastics into lubricating oils. EP 0 620 264 A1 discloses a process for producing lubricating oils from waste or virgin polyolefins by thermally cracking the waste in a fluidized bed to form a waxy product, optionally using hydrotreating, followed by catalytic isomerization and fractionation to recover the lubricating oil.

[0004] Other documents relating to processes for converting waste plastics into lubricating oils include U.S. Patent Nos. 6,288,296, 6,774,272, 6,822,126, 7,834,226, 8,088,961, 8,404,912, and 8,696,994, and U.S. Patent Application Publication Nos. 2019 / 0161683, 2016 / 0362609, and 2016 / 0264885. The foregoing patent documents are incorporated herein by reference in their entireties.

[0005] Current methods of chemical recycling via pyrolysis are not likely to have a significant impact on the plastics industry. Current pyrolysis operations produce poor-quality fuel components (naphtha and diesel-range products), but the quantities are small enough that these products can be blended into the fuel supply. However, to address environmental concerns, recycling the very large amounts of waste polyethylene and waste polypropylene makes such simple blending unsustainable. The raw products from pyrolysis units are too poor in quality to be blended in large quantities (e.g., 5-20 vol% blends) into transportation fuels.

[0006] More robust processes are needed to industrially recycle single-use plastics on a large scale and reduce their environmental impact. These improved processes should establish a "circular economy" for waste polyethylene and polypropylene plastics, effectively recycling post-consumer waste plastics as starting material for polymers and high-value by-products. Summary of the Invention

[0007] Provided is a continuous process for converting waste plastics into polyethylene for recycling. The process includes 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 off-gas, a naphtha / diesel fraction, a heavy fraction, and a char.

[0008] Integrating this process into oil refineries is a key aspect of this process, enabling a circular economy with single-use waste plastics such as polyethylene. Thus, the naphtha / diesel fraction is passed to the crude unit of the refinery. The straight-run naphtha (C5-C8) fraction is recovered from the crude unit distillation column and passed to a steam cracker for ethylene production. The heavy fraction from the thermal cracking unit can be passed to an isomerization dewaxing unit to produce base oil.

[0009] In another embodiment, a continuous process for converting waste plastics, including polyethylene, into polyethylene for recycling for polymerization is provided. The process includes selecting waste plastics, including polyethylene and polypropylene, and passing the waste plastics through a pyrolysis reactor to thermally decompose at least a portion of the polyolefin waste and produce a pyrolysis effluent. The pyrolysis effluent is separated into off-gas, a naphtha / diesel fraction, a heavy fraction, and char. The naphtha / diesel fraction is passed to a crude refinery unit, from which a propane and butane (C3-C4) fraction is recovered. The (C3-C4) fraction is passed to a steam cracker for ethylene production. The heavy fraction from the pyrolysis unit can be passed to an isomerization dewaxing unit to produce lubricant base oil.

[0010] Refineries generally have their own hydrocarbon supply that flows through their refinery units. The volume of the naphtha / diesel or waxy heavy fraction stream produced from the pyrolysis of waste plastics and flowing to the refinery units can constitute any practical or accommodating volume percent (vol%) of the total flow (total flow) to the refinery units. Generally, the flow rate of the fractions produced from the pyrolysis of waste plastics can be up to about 50 vol% of the total flow (i.e., refinery flow rate and distillate flow rate) for practical reasons. In one embodiment, the naphtha / diesel flow rate is up to about 20 vol% of the total flow rate.

[0011] Among other factors, it has been shown that waste pyrolysis oil and waste pyrolysis wax can be upgraded to high-value products such as gasoline, jet, diesel, and base oils through the addition of refinery operations. It has also been shown that the addition of refinery operations can efficiently and effectively produce clean naphtha (C5-C8) or C3-C4 from the waste pyrolysis oil, leading to the production of ultimate polyethylene polymer. Positive economics are realized throughout the process, from recycled plastics to polyethylene products with product quality comparable to virgin polymers. [Brief explanation of the drawings]

[0012] [Figure 1] Figure 1 shows the current practice of pyrolyzing waste plastics to produce fuel or wax (base case).

[0013] [Figure 2] Figure 2 illustrates this process for establishing a circular economy for waste plastics.

[0014] [Figure 3] Figure 3 shows the classification of plastic types for recycling waste plastics. DETAILED DESCRIPTION OF THE INVENTION

[0015] This process provides a method for recycling waste polyethylene and / or waste polypropylene into virgin polyethylene, establishing a circular economy by combining separate industrial processes. The majority of polyethylene and polypropylene polymers are used in single-use plastics and are discarded after use. This single-use plastic waste is becoming an increasingly significant environmental issue. Currently, there appear to be few options for recycling polyethylene and polypropylene waste plastics into value-added chemical and fuel products. Currently, only a small amount of polyethylene / polypropylene is recycled via chemical recycling, and the recycled and purified polymer pellets are thermally cracked in a pyrolysis unit to produce fuels (naphtha, diesel), steam cracker feedstock, or slack wax.

[0016] Ethylene is the most produced petrochemical building block. Hundreds of millions of tons of ethylene are produced annually via steam cracking. Steam crackers use either gaseous feedstocks (ethane, propane, and / or butane) or liquid feedstocks (naphtha or gas oil). Steam cracking is a non-catalytic cracking process that takes place at very high temperatures, up to 850°C.

[0017] Polyethylene is widely used in a variety of consumer and industrial products. It is the most common plastic, with over 100 million tons of polyethylene resin produced annually. Its primary use is in packaging (plastic bags, plastic film, geomembranes, bottles, and other containers). Polyethylene is produced in three main forms, all of which have the same chemical formula (C2H4): n However, the molecular structure is different: high density polyethylene (HDPE, approximately 0.940-0.965 g / m -3 ), linear low-density polyethylene (LLDPE, approximately 0.915 to 0.940 g / cm -3 ), low-density polyethylene (LDPE, <0.930g / cm-3 HDPE has low branching and short side chains, while LDPE has very high branching and long side chains. LLDPE is a substantially linear polymer with a significant number of short branches, usually made by copolymerization of ethylene with short-chain alpha olefins.

[0018] Low-density polyethylene (LDPE) is produced by radical polymerization at temperatures between 150 and 300°C and very high pressures between 1,000 and 3,000 atmospheres. This process uses small amounts of oxygen and / or organic peroxide initiators to produce a polymer with approximately 4,000 to 40,000 carbon atoms per average polymer molecule and high branching. High-density polyethylene (HDPE) is produced at relatively low pressures (10 to 80 atmospheres) and temperatures between 80 and 150°C in the presence of a catalyst. Ziegler-Natta organometallic catalysts (titanium(III) chloride with aluminum alkyl) and Phillips-type catalysts (chromium(IV) oxide on silica) are typically used, and this production is carried out via a slurry process using a loop reactor or a gas-phase process using a fluidized-bed reactor. Hydrogen is mixed with the ethylene to control the polymer chain length. The conditions for producing linear low density polyethylene (LLDPE) are similar to those for HDPE, except for the copolymerization of ethylene with short chain alpha olefins (1-butene or 1-hexene).

[0019] Today, only a small fraction of post-consumer polyethylene products are collected for recycling due to the inefficiencies and ineffectiveness of recycling efforts mentioned above.

[0020] Figure 1 shows a diagram of waste plastic fuel or wax pyrolysis as practiced in industry today. As mentioned above, polyethylene and polypropylene waste are typically sorted together (1). The cleaned polyethylene / polypropylene waste 2 is converted to off-gas 4 and pyrolysis oil (liquid product) in pyrolysis unit 3. Off-gas 4 from the pyrolysis unit is used as fuel to operate pyrolysis unit 3, while only the pyrolysis unit is used for commercial purposes. An on-site distillation unit (not shown) separates the pyrolysis oil to produce naphtha and diesel 5 products, which are sold to the fuel market. The heavy pyrolysis oil fraction 6 is recycled to pyrolysis unit 3 to maximize fuel yield. Char 7 is removed from pyrolysis unit 3. The heavy fraction 6 is rich in long-chain linear hydrocarbons and is highly waxy (i.e., forms paraffinic wax when cooled to ambient temperature). Wax can be separated from the heavy fraction 6 and sold to the wax market.

[0021] The process converts large amounts of waste plastics into pyrolyzed polyethylene and / or polypropylene by integrating the waste polymer pyrolysis product stream into an oil refinery operation. The resulting process produces polymer feedstock (naphtha or C3-C4 for ethylene crackers) and high-quality gasoline and diesel fuels, and / or high-quality base oils.

[0022] In general, the process provides a circular economy for polyethylene plants. Polyethylene is produced through the polymerization of pure ethylene. Clean ethylene can be produced using a steam cracker. Either naphtha or a C3-C4 stream can be fed to the steam cracker. The ethylene is then polymerized to produce polyethylene.

[0023] By adding refining operations to upgrade the waste pyrolysis oil to higher value products (gasoline and diesel, base oils) and to produce clean LPG and naphtha for the steam cracker for the production of ultimate polyethylene polymer, positive economics can be generated throughout the process from recycled plastic to a polyethylene product with quality comparable to virgin polymer.

[0024] Pyrolysis units produce low-quality products containing contaminants such as calcium, magnesium, chlorides, nitrogen, sulfur, dienes, and heavy components, which cannot be used in large quantities for blending transportation fuels. It has been shown that passing these products through a refinery unit can capture the contaminants in a pretreatment unit and mitigate their negative impact. The fuel components can be further upgraded in an appropriate refinery unit equipped with chemical conversion processes, and the final transportation fuel produced by the integrated process can be of higher quality and meet fuel quality requirements. This process upgrades wax into valuable lubricating base oil. The integrated process produces a much cleaner naphtha stream for ethylene production and steam cracker feedstock for polyethylene production. Mass production on these specifications makes a "circular economy" of recycled plastics feasible.

[0025] The carbon entering and leaving the refinery operation is "transparent," meaning that not all molecules from the waste plastic are recycled back to the polyolefin plant and made into the exact olefin product, but it is nevertheless considered a "credit" because the net "green" carbon entering and leaving the refinery is positive. These integrated processes result in a significant reduction in the amount of virgin feedstock required for polypropylene plants.

[0026] Figure 2 illustrates this integrated process, integrating refining operations with recycling for efficient polyethylene production. In Figure 2, mixed waste plastics are sorted together (21). The cleaned waste plastics 22 are converted in a pyrolysis unit 23 into off-gas 24, pyrolysis oil (a liquid product), and optionally wax (a solid product at ambient temperatures). The off-gas 24 from the pyrolysis unit can be used as fuel to operate the pyrolysis unit 23. The pyrolysis oil is typically separated into a naphtha / diesel fraction 25 and a heavy fraction 26 by an on-site distillation unit. After the pyrolysis process is complete, char 27 is removed from the pyrolysis unit 23.

[0027] The pyrolysis unit can be located near a waste plastic collection site, which can be remote from the refinery, near the refinery, or within the refinery. If the pyrolysis unit is located remote from the refinery, the pyrolysis oil (naphtha / diesel and heavy oil) can be transported to the refinery by truck, barge, rail car, or pipeline. However, it is preferred that the pyrolysis unit be located within the waste plastic collection site or within the refinery.

[0028] The preferred starting material for this process is sorted waste plastics containing primarily polyethylene and polypropylene (plastic recycling classification types 2, 4, and 5). The pre-sorted waste plastics are washed, shredded or pelletized, and fed to a pyrolysis unit for pyrolysis. Figure 3 shows the plastic type classification for waste plastic recycling. Classification types 2, 4, and 5 are high-density polyethylene, low-density polyethylene, and polypropylene, respectively. Polyethylene and polypropylene waste plastics can be used in any combination. It is preferred to use at least some polyethylene waste plastic in this process.

[0029] Proper sorting of waste plastics is crucial to minimize contaminants such as N, Cl, and S. Plastic waste, including polyethylene terephthalate (Plastic Recycling Classification Type 1), polyvinyl chloride (Plastic Recycling Classification Type 3), and other polymers (Plastic Recycling Classification Type 7), should be sorted to less than 5%, preferably less than 1%, and most preferably less than 0.1%. The process can tolerate moderate amounts of polystyrene (Plastic Recycling Classification Type 6). Waste polystyrene should be sorted to less than 30%, preferably less than 20%, and most preferably less than 5%.

[0030] Washing waste plastics removes metallic contaminants, such as sodium, calcium, magnesium, and aluminum, as well as non-metallic contaminants from other waste sources. Non-metallic contaminants include contaminants from Group IV of the periodic table, such as silica; contaminants from Group V, such as phosphorus and nitrogen compounds; contaminants from Group VI, such as sulfur compounds; and halide contaminants from Group VII, such as fluoride, chloride, and iodide. Residual metal, non-metallic contaminants, and halides must be removed to less than 50 ppm, preferentially less than 30 ppm, and most preferentially less than 5 ppm.

[0031] If washing does not adequately remove metal, non-metallic contaminants, and halide impurities, a separate guard bed can be used to remove metal and non-metallic contaminants.

[0032] Pyrolysis is carried out by contacting the plastic material feedstock in a pyrolysis zone under pyrolysis conditions, where at least a portion of the feedstock is decomposed, thereby forming a pyrolysis zone effluent containing 1-olefins and n-paraffins. The pyrolysis conditions include temperatures of about 400°C to about 700°C, preferably about 450°C to about 650°C. Conventional pyrolysis techniques teach operating conditions at pressures above atmospheric pressure (see, e.g., U.S. Pat. No. 4,642,401). Furthermore, it has been found that the yield of desired products can be controlled by adjusting the pressure downward (see, e.g., U.S. Pat. No. 6,150,577). Accordingly, in some embodiments where such control is desired, the pyrolysis pressure is below atmospheric pressure.

[0033] Figure 2 illustrates this integrated process, in which only the naphtha / diesel fraction 25 from the thermal cracking unit 23 is sent to a crude unit desalter 28 to produce C5-C8 naphtha (29), preferentially C5-C7 naphtha, and most preferentially C5-C6 naphtha, for feed to a steam cracker 30. The steam cracker 30 produces ethylene 36. The ethylene is passed to a polymerization unit 40 to produce polyethylene. The polyethylene is used in polyethylene consumer products 41.

[0034] Refineries typically have their own supply of hydrocarbons that flow through the refinery units. The volume of the naphtha / diesel stream produced from the thermal cracking of waste plastics and flowing to the refinery unit (here, the crude unit) can constitute any practical or accommodating volume percent (vol%) of the overall flow (total flow) to the refinery unit. Generally, the flow rate of the naphtha / diesel fraction produced from the thermal cracking of waste plastics can be up to about 50 vol% of the total flow rate (i.e., refinery flow rate and naphtha / diesel flow rate) for practical reasons. In one embodiment, the naphtha / diesel flow rate is up to about 20 vol% of the total flow rate. In another embodiment, the naphtha / diesel flow rate is up to about 10 vol% of the total flow rate. About 20 vol% has been found to be a very practical amount in terms of refinery impact, while also providing excellent results and being an accommodating amount. Of course, the amount of naphtha / diesel produced from the thermal cracking can be controlled so that the fraction passed to the refinery unit provides the desired volume percent of the flow rate. The flow rate of the heavy fraction to the dewaxing unit can be similarly controlled and / or adjusted.

[0035] Refinery crude units separate crude oil into fractions, such as liquefied petroleum gas (LPG), naphtha, kerosene, diesel, and gas oil, for further processing into useful petroleum products. Refinery crude units include a crude oil processing section, commonly known as a desalter, and a crude oil distillation or fractionation section. The distillation section typically includes atmospheric and vacuum distillation units.

[0036] The naphtha / diesel fraction from the thermal cracking unit is fed to a desalter to remove salts and solids contained in the oil, protecting downstream equipment from the harmful effects of contaminants. To remove the salts, water is mixed with the oil and typically heated to a temperature of about 215°F to about 280°F, where it is separated in the desalter.

[0037] The desalted oil is sent to an atmospheric distillation unit, heated to approximately 340-372 °C (644-700 °F) at the bottom of the distillation tower, where liquids are removed at various points in the fractional distillation tower to produce various fuels. Fuel from the crude unit is sent to various upgrading units in the refinery to remove impurities (nitrogen, sulfur) and catalytically convert fractions to improve product properties such as octane and cetane. The bottoms from the atmospheric distillation tower (also known as atmospheric resid) are sent to a vacuum distillation tower to produce vacuum gas oil (650-1050 °F) and vacuum resid. Vacuum gas oil can be used to produce lubricating base oil or further cracked to produce gasoline, jet, and diesel fuel.

[0038] The steam cracker and ethylene polymerization unit are preferably located near the refinery so that the feedstocks (propane, butane, naphtha) can be transported via pipeline. For petrochemical plants located remotely from the refinery, the feedstocks can be delivered via truck, barge, railcar, or pipeline.

[0039] The heavy naphtha / diesel from the pyrolysis oil can be combined with hydrocarbons from the crude unit distillation and sent to a suitable refining unit 32 as a heavy naphtha, diesel, atmospheric gas oil stream 31 for upgrading to clean gasoline and diesel 33.

[0040] The heavy waxy pyrolysis oil 26 from the thermal cracking unit is sent to a base oil dewaxing unit 34 equipped with a precious metal-containing zeolite catalyst for isomerization dewaxing or hydroisomerization to produce a lubricating base oil 35 with excellent viscosity index and pour point. The flow rate of the heavy waxy fraction can be controlled and adjusted as needed based on the desired amount of storage.

[0041] An isomerization dewaxing unit converts paraffinic, waxy, heavy hydrocarbon material (typically boiling at about 650° F.) into high viscosity index (VI) lubricating oils. The unit typically includes a feed hydrotreating section, an isomerization dewaxing section, and a distillation section.

[0042] The feed to the dewaxing unit is preferably first subjected to hydrotreating in a hydrotreating step. This hydrotreating is carried out as part of the dewaxing unit. The feed to the hydrotreating step removes most of the nitrogen-, sulfur-, and / or oxygen-containing contaminants. The hydrotreating step also saturates a portion of the olefins, dienes, and aromatics, improving the quality of the feed to the dewaxing unit. Typical hydrotreating conditions used to remove contaminants while avoiding cracking include temperatures ranging from about 190°C (374°F) to about 340°C (644°F), pressures ranging from about 400 psig to about 3000 psig, and a pressure of about 0.1 hr. -1 ~approx. 20 hours -1 and hydrogen recycle rates ranging from about 400 to about 15,000 SCF / B. Hydrotreating catalysts include those conventionally used in hydrotreating units, including metals such as Ni, Mo, Co, and W, and porous supports such as alumina, silica, or silica-alumina.

[0043] The hydrotreated heavy hydrocarbons are fed to a dewaxing reactor equipped with an isomerization dewaxing catalyst containing a noble metal, an intermediate pore size molecular sieve, and a binder. The catalyst preferably contains an intermediate pore size (10-ring) molecular sieve such as ZSM-23, ZSM-35, ZSM-48, ZSM-5, SSZ-32, SSZ-91, SAPO-11, SAPO-31, and SAPO-41. The noble metal includes a Group VIII metal such as Pt, Pd, or a mixture of Pt and Pd. Porous alumina or silica is typically used to bind the materials together to produce catalyst pellets for a fixed-bed reactor. Typical reaction conditions for the dewaxing reactor include a temperature range of 200°C (392°F) to about 475°C (887°F), a pressure range of about 200 psig to about 3000 psig, and a reaction time of about 0.2 hr. -1 ~approx. 10 hours -1 and hydrogen recycle rates ranging from about 400 to about 15,000 SCF / B. The isomerization dewaxing catalyst converts n-paraffins to isoparaffins, thereby lowering the pour point of the resulting oil and forming a high VI lube oil.

[0044] The hydrocarbon effluent from the isomerization dewaxing section is sent to a distillation unit which separates the effluent into various oil fractions, such as a base oil fraction boiling above approximately 650° F., a diesel fraction boiling between about 300-700° F., and a gasoline fraction boiling between about 80-400° F. The boiling points of the gasoline, jet, and diesel fractions are adjusted according to seasonal and regional specifications.

[0045] In another embodiment, a C3-C4 fraction 37 is recovered from the refinery and crude unit 28. This stream can also be fed to a steam cracker 30 for the production of ethylene 36. The ethylene can then be polymerized (40) into consumer products 41.

[0046] The benefits of a circular economy and effective and efficient recycling campaigns are realized through this integrated process.

[0047] The following examples are provided to further illustrate the present process and its advantages. These examples are for illustrative purposes and are not intended to be limiting. [Example]

[0048] Example 1: Properties of pyrolysis oil and wax from commercial sources

[0049] Pyrolysis oil and wax samples were obtained from commercial sources. Their properties are summarized in Table 1. These pyrolysis samples were prepared from waste plastics, primarily polyethylene and polypropylene, via pyrolysis in a pyrolysis reactor at approximately 400–600 °C and near atmospheric pressure without the addition of gas or catalyst. Pyrolysis units typically produce gas, liquid oil products, optional wax products, and char. The overhead gas stream from the pyrolysis unit containing the thermally cracked hydrocarbons was cooled, and the condensate was collected as pyrolysis oil (liquid at ambient temperature) and / or pyrolysis wax (solid at ambient temperature). Pyrolysis oil is the primary product of the pyrolysis unit. Some pyrolysis units also produce pyrolysis wax as a separate product in addition to pyrolysis oil. [Table 1]

[0050] Specific gravity measurements were performed using ASTM D4052. Simulated boiling point distribution curves were obtained using ASTM D2887. Carlo-Erba analysis for carbon and hydrogen was performed according to ASTM D5291. Bromine number measurements were performed according to ASTM D1159. Hydrocarbon type analysis was performed using a high-resolution magnetic mass spectrometer, scanning the magnet from 40 to 500 daltons. Total sulfur was determined using XRF according to ASTM D2622. Nitrogen was determined using chemiluminescence detection according to a modified ASTM D5762 method. Total chloride content was measured using a combustion ion chromatography instrument according to a modified ASTM 7359 method. The oxygen content in the boiling range of naphtha and distillate was estimated using GC with an electron ionization detector in the m / Z range of 29 to 500. Trace metal and nonmetallic elements in the oil were determined using inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0051] Industrial pyrolysis processes of sorted plastics, primarily sourced from polyethylene and polypropylene waste, have produced high-quality hydrocarbon streams with specific gravities in the range of 0.7 to 0.9 and boiling points in the range of 18 to 1100°F, as in the case of pyrolysis oil or pyrolysis wax.

[0052] The pyrolysis products are fairly pure hydrocarbons composed primarily of carbon and hydrogen. The hydrogen-to-carbon molar ratio varies from 1.7 to nearly 2.0. The bromine numbers range from 14 to 60, indicating varying degrees of unsaturation due to olefins and aromatics. The aromatic content ranges from 5 to 23 vol%, with more severe pyrolysis units producing more aromatics. Depending on the process conditions of the pyrolysis unit, the pyrolysis products exhibit paraffin contents ranging from the mid-20s to mid-50s vol%. Significant amounts of olefins are also present in the pyrolysis products. Samples A and B are pyrolysis oils produced under more severe conditions, such as higher pyrolysis temperatures and / or longer residence times, resulting in higher aromatic and lower paraffin contents, with H / C molar ratios of approximately 1.7 and high bromine numbers of 50 to 60. Samples C and D were produced under less severe conditions and their pyrolysis oils are more paraffinic, resulting in H / C molar ratios closer to 2.0 and bromine numbers around 40. Sample E (pyrolysis wax) is mostly paraffinic saturated hydrocarbons with a significant amount of linear hydrocarbons (as opposed to branched hydrocarbons) and a bromine number of only 14.

[0053] The following Examples 2 to 5 show the evaluation of waste plastic pyrolysis oil as a transportation fuel.

[0054] [Example 2] Fractional distillation of pyrolysis oil for evaluation as a transportation fuel

[0055] Sample D was distilled to separate multiple fractions of hydrocarbons, namely, gasoline (350°F - ) fraction, jet (350-572°F) fraction, diesel (572-700°F) fraction, and heavy (700°F + ) fractions were produced. Table 2 summarizes the boiling point distribution and impurity distribution of each fraction of the distillation product. [Table 2]

[0056] [Example 3] Evaluation of pyrolysis oil fractions for gasoline fuel

[0057] Sample F (a fraction of pyrolysis oil with a boiling point range equivalent to that of gasoline fuel) was evaluated for its potential use as gasoline fuel. The carbon number range of Sample F is C5 to C12, which is typical for gasoline fuel.

[0058] Because pyrolysis oils are olefinic, oxidation stability (ASTM D525) and gum formation tendency (ASTM D381) were identified as the most important properties to investigate. Research octane number (RON) and motor octane number (MON) are also important properties for engine performance. RON and MON values were estimated from detailed GC analysis of the hydrocarbons. [Table 3]

[0059] Sample F (a fraction of pyrolysis oil in the boiling range of gasoline fuel) is of poor quality and cannot be used alone as a gasoline fuel for automobiles. The gasoline fraction from pyrolysis oil showed very low oxidation stability, with sample F failing after only 90 minutes, compared to a target stability of over 1440 minutes. The pyrolysis gasoline exceeded the wash gum target of 4 mg / 100 mL, indicating a strong tendency for gum formation. The pyrolysis gasoline has a lower octane number compared to the reference gasoline. Premium unleaded gasoline was used as the reference gasoline.

[0060] We also investigated the possibility of blending limited amounts of pyrolysis gasoline fractions into reference gasoline. Our studies showed that up to 15% by volume of sample F could be blended into refined gasoline while still achieving fuel property targets. By integrating pyrolysis gasoline products with refined fuels, the overall product quality can be maintained.

[0061] These results indicate that the as-produced gasoline fraction of pyrolysis oil has limited usefulness as a gasoline fuel. Upgrading in a refinery unit is preferred to convert this gasoline fraction of pyrolysis oil into hydrocarbons that meet gasoline fuel property targets.

[0062] Example 4: Evaluation of pyrolysis oil fractions for jet fuel

[0063] Sample G (a fraction of pyrolysis oil with a boiling point in the range of jet fuel) was evaluated for its potential use as jet fuel. The carbon number range of Sample G is C9 to C18, which is typical for jet fuel.

[0064] Because pyrolysis oil is olefinic, the jet fuel thermal oxidation test (D3241) was considered the most important test. Sample G, the pure jet fraction of pyrolysis oil, had an oxidation stability of only 36 minutes, indicating that pure pyrolysis jet fraction is unsuitable for use as jet fuel.

[0065] We prepared a 5% by volume blend of the pyrolysis jet fraction (Sample G) with refinery-produced jet fuel. This blend still failed the jet fuel oxidation test, as shown in Table 4. [Table 4]

[0066] These results indicate that the as-produced jet fraction of pyrolysis oil is completely unsuitable for jet fuel and that upgrading in a refining unit is necessary to convert this jet fraction of pyrolysis oil into hydrocarbons that meet the property targets for jet fuel.

[0067] Example 5: Evaluation of pyrolysis oil fractions for diesel fuel

[0068] Sample H (a fraction of pyrolysis oil with a boiling point range equivalent to that of diesel fuel) was evaluated for its potential use as diesel fuel. The carbon number range of Sample H is C14 to C24, which is typical for diesel fuel.

[0069] Sample H contains a significant amount of normal hydrocarbons, which tend to exhibit waxy properties, so cold flow properties such as pour point (ASTM D5950-14) and cloud point (ASTM D5773) were considered the most important tests.

[0070] We prepared two blends of Sample H at 10% and 20% by volume with refinery-produced diesel fuel, but both blends still failed the target pour point of less than -17.8°C (0°F). [Table 5]

[0071] These results indicate that pyrolysis oil as it is is completely unsuitable for diesel fuel and that upgrading in a refinery unit is necessary to convert the diesel fraction of pyrolysis oil into hydrocarbons that meet the property targets for diesel fuel.

[0072] Example 6: Co-processing of pyrolysis oil into a crude or desalination unit

[0073] The results in Table 1 show that industrial pyrolysis processes of sorted plastics, primarily sourced from polyethylene and polypropylene waste, produce high-quality pyrolysis oil composed primarily of carbon and hydrogen. With good sorting and efficient pyrolysis unit operation, nitrogen and sulfur impurities are at sufficiently low levels that modern refineries can process cofeeding of pyrolysis feedstock to processing units without detrimental effects.

[0074] However, some pyrolysis oils may still contain large amounts of metals (Ca, Fe, Mg) and other non-metals (N, S, P, Si, Cl, O), which can adversely affect the performance of the refinery's conversion units. In the case of pyrolysis oils, products with high impurity levels are preferentially fed to a desalter before the crude unit, which effectively removes the majority of the impurities.

[0075] By feeding the pyrolysis feedstock to a crude unit or a desalting unit prior to the crude unit, the pyrolysis oil is fractionated into multiple components, which are then further converted in subsequent conversion units, including a paraffin isomerization unit, a jet hydrotreater, a diesel hydrotreater, a fluid catalytic cracking (FCC) unit, an alkylation unit, a hydrocracking unit, and / or a coker unit, to produce gasoline, jet, and diesel fuels with satisfactory product properties. The conversion units (FCC or hydrocracking units) also convert the heavy fraction (corresponding to Sample I) into high-quality transportation fuels.

[0076] After the crude unit, the pyrolysis oil is further converted in a subsequent crude unit. Example 7 below demonstrates the conversion of waste plastic pyrolysis oil into high-quality transportation fuel in a refinery conversion unit (using an FCC unit as an example).

[0077] [Example 7] Conversion of pyrolysis oil in FCC

[0078] To study the effect of coprocessing waste plastic pyrolysis oil on FCC, a series of laboratory tests were conducted using Samples A and C. Vacuum gas oil (VGO) is a typical feedstock for FCC. The FCC performance of a 20% blend of pyrolysis oil with VGO and pure pyrolysis oil was compared with that of pure VGO feedstock.

[0079] FCC experiments were performed in a Kayser Technology Inc. Model C ACE (advanced cracking evaluation) unit using regenerated equilibrium catalyst (Ecat) from a refinery. The reactor was a fixed-flow reactor using N2 as the fluidizing gas. Catalytic cracking experiments were performed at atmospheric pressure and a reactor temperature of 900°F. The catalyst / oil ratio was varied between 5 and 8 by varying the amount of catalyst. Gas products were collected and analyzed using a refinery gas analysis unit (RGA) equipped with a GC with an FID detector. In-situ regeneration of spent catalyst was performed in the presence of air at 1300°F, and the regenerated flue gas was passed through a LECO to determine the coke yield. Liquid products were weighed and analyzed by GC for simulated distillation (D2887) and C5 - Composition analysis was performed. Mass balance revealed coke, dry gas components, LPG components, gasoline (C5, ~430°F), light cycle oil (LCO, 430-650°F), and heavy cycle oil (HCO, 650°F). + The yield of ) was determined. The results are summarized in Table 6 below. [Table 6]

[0080] The results in Table 6 show that co-feeding up to 20% pyrolysis oil by volume only slightly changes the performance of the FCC unit, indicating that co-processing up to 20% pyrolysis oil is readily feasible. Blending 20% by volume of Sample A or Sample C resulted in a very slight decrease in coke and dry gas yield, a slight increase in gasoline yield, and a slight decrease in LCO and HCO, which are favorable in most situations. Because pyrolysis oil is paraffinic, blending 20% of Sample A or Sample C resulted in a decrease in octane number of approximately 3-5. Depending on the refinery's operational flexibility, these octane losses can be offset by adjusting the blending or feed location.

[0081] The FCC unit cracks the pyrolysis oil into fuel-range hydrocarbons, reduces impurities, and isomerizes n-paraffins to isoparaffins. All of these chemical properties improve the fuel properties of the pyrolysis oil and wax. By co-feeding the pyrolysis oil through the FCC process unit with a zeolite catalyst, the fuel-range oxygen and nitrogen impurities were significantly reduced: nitrogen (N) from approximately 300-1400 ppm to approximately 30 ppm, and oxygen (O) from approximately 250-540 ppm to approximately 60-80 ppm. The hydrocarbon compositions of all these co-feed products are well within the range of typical FCC gasoline.

[0082] FCC operation of 100% pyrolysis oil showed a significant minus in octane number (minus about 13–14), indicating that co-processing of pyrolysis oil is preferable to processing of pure 100% pyrolysis oil.

[0083] [Example 8] Generation of C3-C4 and naphtha feedstocks for chemical production via co-feeding waste plastic pyrolysis products to refinery and crude units

[0084] The pyrolysis oil is fractionated into components by feeding it to a crude unit or by feeding it to a desalting unit prior to the crude unit. By co-feeding the pyrolysis oil, the refinery crude unit produces significant amounts of clean propane, butane, and naphtha streams, including recycle components, that can be fed to the steam cracker. At least some, if not all, of these streams are fed to the steam cracker.

[0085] Example 9: Feeding recycled C3-C4 and / or naphtha to a steam cracker for the production of ethylene and subsequent production of recycled polyethylene resin and polyethylene consumer products

[0086] Propane, butane, and naphtha streams are produced via co-feeding the pyrolysis products to a crude unit (Example 8). These streams are suitable feedstocks for co-feeding to a steam cracker to produce ethylene containing recycled content. The ethylene is then processed in a polymerization unit to produce polyethylene resin containing recycled polyethylene / polypropylene-derived materials. The quality of the newly produced polyethylene is indistinguishable from virgin polyethylene made entirely from virgin petroleum resources. This recycled polyethylene resin is further processed to produce a variety of polyethylene products to meet consumer product needs. While these polyethylene consumer products contain chemically recycled circular polymers, the quality of these products is indistinguishable from those made entirely from virgin polyethylene polymers. These chemically recycled polymer products differ from mechanically recycled polymer products, which are of lower quality than polymer products made from virgin polymers.

[0087] Example 10: Co-processing of pyrolysis wax in an isomerization dewaxing unit to produce lubricating base oils

[0088] The results in Table 1 show that industrial pyrolysis processes of selected plastics, primarily sourced from polyethylene and polypropylene waste, produce pyrolysis wax, which is primarily composed of carbon and hydrogen. Various process options were investigated to produce lubricating base oils from this pyrolysis wax via a hydroisomerization dewaxing process.

[0089] Pyrolysis wax still contains large amounts of nitrogen and sulfur impurities, metals (Ca, Fe, Mg) and other non-metals (P, Si, Cl, O), which adversely affect the performance of hydroisomerization dewaxing catalysts containing precious metals (Pt, Pd, or a combination of Pt and Pd) and zeolites such as ZSM-11, ZSM-23, ZSM-48, SSZ-32, SSZ-91, SAPO-11, SAPO-31, and SAPO-41.

[0090] As shown in Example 11 below, attempts to produce high-quality lubricating base oils by directly feeding pure pyrolysis oil with a dewaxing catalyst have been unsuccessful. Because pyrolysis wax is fed directly to a hydroisomerization dewaxing unit, co-feed levels must be limited to less than 10 vol%, preferably less than 5 vol%, to maintain catalyst activity. The volume percent limitation can be attributed to nitrogen impurities that are detrimental to zeolite activity. The nitrogen level of the combined feedstock must be maintained below 5 ppm nitrogen, preferentially below 1 ppm nitrogen.

[0091] Alternatively, the pyrolysis wax is co-fed to a hydrocracking unit to remove S, N, and other impurities. The hydrocracking unit hydrogenates the pyrolysis wax and removes impurities. The severity of the hydrocracking unit can be adjusted to maximize the base oil yield of the combined feedstocks. The co-feed level to the hydrocracking unit can be 50 vol%, preferentially 20 vol%. In this case, the volume percent limitation may be due to metal impurities or N or P impurities, depending on the unit configuration and catalyst selection. The bottoms fraction (650°F) containing the hydrocracked pyrolysis wax is then + ) is fed to a hydroisomerization dewaxing unit to produce lubricating base oil. Alternatively, the pyrolysis wax can be fed to a dedicated hydrogenation unit to remove S, N, and other impurities before being fed to a hydroisomerization dewaxing unit to produce base oil. As shown in Example 12 below, the hydrogenation step removes impurities very easily. The hydrotreated wax can be co-fed to the hydroisomerization dewaxing unit at any volume percent.

[0092] The following Examples 11 and 12 demonstrate unsuccessful and successful process routes to produce high quality base oils using waste plastic pyrolysis wax as a feedstock in refinery conversion units.

[0093] Example 11: Production of base oil from recycled pyrolysis wax via hydroisomerization dewaxing process only

[0094] To evaluate the feasibility of base oil production from recycled wax, Sample E (crude pyrolysis wax) was vacuum distilled and heated to 690°F. + A fraction (Sample J) was produced. 100% Sample J was hydroisomerized overnight in a batch autoclave unit using a Pt / SSZ-32 / alumina catalyst at an oil to catalyst weight ratio of 10:1 at 650°F under 800 psig H pressure. The resulting hydroisomer was vacuum distilled and had a boiling point of 690°F. + A clear oil (Sample K) of 1000 ppm was produced. The properties of these samples are summarized in the table. [Table 7]

[0095] Sample J (690°F from waste plastic pyrolysis) + The slack wax from this fraction is a low-viscosity wax with a viscosity of approximately 4.3 cSt at 100°C and an excellent viscosity index of 169. However, slack wax contains significant amounts of N (180 ppm) and P (32.5 ppm), which passivate the activity of zeolite catalysts in the hydroisomerization dewaxing process. Sample K, a dewaxed and distilled oil, exhibited a viscosity index of 162 and a pour point of 12°C. While this pour point was significantly lower than the 42°C of Sample E, a pour point of 12°C is still significantly lower than the industry target of -15°C or below. This oil cannot be used in high-performance modern lubricants because it loses its fluidity / oiliness properties at ambient temperatures below 12°C, becoming a thick or solid-like material.

[0096] This study shows that to produce acceptable base oils from waste plastic pyrolysis wax, the pyrolysis wax needs to be hydrotreated or hydrocracked to reduce N impurities and other impurities.

[0097] [Example 12] Production of high quality base oil containing recycled components by hydrotreating followed by hydroisomerization dewaxing process

[0098] Sample E (crude pyrolysis wax) was hydrogenated in a continuous fixed bed unit containing NiMo / alumina catalyst at a reactor temperature of 625°F and a pressure of 1200 psig. The catalyst bed volume was hydrogenated for 1.5 hours. -1 A liquid feed flow rate of 2500 scf / bbl and a H / hydrocarbon flow rate of 2500 scf / bbl were used to produce a mostly waxy hydroproduct, which was vacuum distilled and heated to 650°F as hydrocracked paraffin wax (Sample L). + fractions were produced.

[0099] Sample L (hydrogenated wax produced from the pyrolysis of waste plastics) was subjected to hydroisomerization dewaxing in a continuous fixed-bed unit containing a Pt / ZZS-91 / alumina catalyst at a reactor temperature of 625°F and a pressure of 400 psig. The catalyst bed volume was used for 1.0 hr -1 A liquid feed flow rate of 2500 scf / bbl and a H / hydrocarbon flow rate of 2500 scf / bbl was used to produce a dewaxed oil. The dewaxed oil was vacuum distilled and the final dewaxed base oil product (Sample M) was obtained at 690°F. + The results are summarized in Table 8. [Table 8]

[0100] Hydrogenation of pyrolysis wax (Sample E) produced a high-quality hydrogenated wax (Sample L). Sample L contained no measurable impurities that could harm the dewaxing catalyst, indicating that all trace impurities were completely removed during hydrogenation. This example demonstrates that high-quality, pure paraffinic wax can be effectively produced from waste plastics, primarily containing polyethylene and polypropylene, and that mild hydrogenation is a highly effective method for purifying waxes derived from waste plastics.

[0101] Hydroisomerization dewaxing of hydrogenated wax (Sample L) produced a very good quality 4 cSt base oil (Sample M) with a viscosity index of 135, a pour point of -35°C, and a cloud point of -17°C. Qualitatively, this base oil, derived from the pyrolysis of waste plastic, falls into the Group III base oil category. These positive results were quite surprising given the poor properties observed in Sample K. Low viscosity (4 cSt) base oils are highly desirable due to their widespread use as components in automotive lubricants.

[0102] Examples 11 and 12 clearly demonstrate that by carefully selecting the co-feed process configuration and process conditions, superior quality base oils can be produced from wax obtained from the pyrolysis of polyethylene and polypropylene waste. The results clearly demonstrate that the preferred method for producing base oils from waste plastic pyrolysis wax is by hydrogenation followed by a hydroisomerization dewaxing process. The final base oil contains recycled components, and the quality of this base oil is equivalent to or better than that produced by conventional refining processes using virgin crude oil.

[0103] The above examples clearly demonstrate a new and effective way to recycle large amounts of polyethylene and polypropylene derived waste plastics by chemical recycling via pyrolysis followed by co-feeding of the pyrolysis products to a refinery through efficient integration, which enables the production of high quality fuels, lubricant base oils and recycled polymers.

[0104] As used in this disclosure, the words "comprises" or "comprising" are intended as open-ended transitional phrases, meaning the inclusion of the indicated elements, but not necessarily the exclusion of other unspecified elements. The phrase "consists essentially of" or "consisting essentially of" is intended to mean excluding other elements of essential importance to the composition. The phrase "consisting of" or "consists of" is intended as a transitional phrase meaning the exclusion of all other than the stated elements, excepting only trace impurities.

[0105] All patents and publications referenced herein are incorporated by reference to the extent not inconsistent herewith. It will be understood that the specific structures, functions, and operations of the above-described embodiments are not necessary to practice the present invention, but are included in the description merely to complete an exemplary embodiment or embodiments. Furthermore, it will be understood that the specific structures, functions, and operations described in the above-referenced patents and publications can be practiced in combination with the present invention, but are not essential to its practice. Therefore, it should be understood that the present invention can be practiced as specifically described without actually departing from the spirit and scope of the present invention, as defined by the appended claims.

Claims

1. 1. A continuous process for converting waste plastics into recycling for polyethylene polymerization, comprising: (a) selecting waste plastics comprising polyethylene and / or polypropylene; (b) passing the waste plastic from (a) through a pyrolysis reactor to thermally decompose at least a portion of the polyolefin waste and produce a pyrolyzed effluent; (c) separating the pyrolyzed effluent into an off-gas, a naphtha / diesel fraction, a heavy fraction, and a char; (d) passing the naphtha / diesel fraction through a crude unit of a refinery; (e) straight run naphtha (C ５ -C ８ ) recovering the fraction; (f) the straight-run naphtha fraction (C ５ -C ８ ) through a steam cracker for the production of ethylene; (g) passing the heavy fraction through an isomerization dewaxing unit to produce a base oil; The above process, comprising:

2. 10. The process of claim 1, wherein the naphtha / diesel fraction of (c) is passed directly to a refinery crude unit and contaminants are removed in a crude unit desalter.

3. 10. The process of claim 1, wherein the contaminants are removed at a pyrolysis site.

4. 10. The process of claim 1, wherein the ethylene produced in (f) is subsequently polymerized.

5. 5. The process of claim 4, wherein a consumer polyethylene product is prepared from the polymerized ethylene.

6. 2. The process of claim 1, wherein the waste plastic selected in (a) is from plastic classification groups 2, 4, and / or 5.

7. 10. The process of claim 1, wherein heavy naphtha / diesel / atmospheric gas oil is recovered from the crude unit and further processed into clean gasoline, diesel, or jet fuel in a refinery.

8. 8. The process of claim 7, wherein the amount of virgin crude oil processed by the crude unit is reduced with recycled pyrolysis oil.

9. 10. The process of claim 1, wherein the amount of base oil produced by the isomerization dewaxing unit is augmented with recycled pyrolysis oil.

10. 10. The process of claim 1, wherein the heavy fraction in (g) is hydrotreated and then isomerized in a dewaxing unit.

11. 10. The process of claim 1, wherein the volumetric flow rate of the naphtha / diesel fraction flowing to the crude unit of the refinery comprises up to about 50 volume percent of the total hydrocarbon flow rate flowing to the crude.

12. 12. The process of claim 11, wherein the naphtha / diesel flow rate comprises up to 20% by volume.

13. 1. A continuous process for converting waste plastics into recycling for polyethylene polymerization, comprising: (a) selecting waste plastics comprising polyethylene and / or polypropylene; (b) passing the waste plastic from (a) through a pyrolysis reactor to thermally decompose at least a portion of the polyolefin waste and produce a pyrolyzed effluent; (c) separating the pyrolyzed effluent into an off-gas, a naphtha / diesel fraction, a heavy fraction, and a char; (d) passing the naphtha / diesel fraction through a crude unit of a refinery; (e) Propane and butane (C ３ -C ４ )) recovering the fraction; (f) The above (C ３ -C ４ ) passing the fraction through a steam cracker for the production of ethylene; (g) passing the heavy fraction through an isomerization dewaxing unit to produce a base oil; The above process, comprising:

14. 14. The process of claim 13, wherein the naphtha / diesel fraction of (c) is passed directly to a refinery crude unit and contaminants are removed in a crude unit desalter.

15. 14. The process of claim 13, wherein the contaminants are removed at a pyrolysis site.

16. 14. The process of claim 13, wherein the ethylene produced in (f) is then polymerized.

17. 17. The process of claim 16, wherein a consumer polyethylene product is prepared from the polymerized ethylene.

18. 14. The process of claim 13, wherein the waste plastic selected in (a) is from plastic classification groups 2, 4, and / or 5.

19. 14. The process of claim 13, wherein heavy naphtha / diesel / atmospheric gas oil is recovered from the crude unit and further processed into clean gasoline, diesel, or jet fuel in a refinery.

20. 20. The process of claim 19, wherein the amount of virgin crude oil processed by the crude unit is reduced with recycled pyrolysis oil.

21. 14. The process of claim 13, wherein the amount of base oil produced by the isomerization dewaxing unit is augmented with recycled pyrolysis oil.

22. 14. The process of claim 13, wherein the heavy fraction in (g) is hydrotreated and then isomerized in a dewaxing unit.

23. 14. The process of claim 13, wherein the volumetric flow rate of the naphtha / diesel fraction flowing to the crude unit of the refinery comprises up to about 50 volume percent of the total hydrocarbon flow rate flowing to the crude.

24. 24. The process of claim 23, wherein the naphtha / diesel flow rate comprises up to 20% by volume.

25. 1. A process for converting waste plastics into chemicals useful for the preparation of polyethylene and lubricating oils, comprising: (a) selecting waste plastics comprising polyethylene and / or polypropylene; (b) pyrolyzing the waste plastics to recover a naphtha / diesel fraction and a heavy fraction; (c) passing the naphtha / diesel fraction through a crude unit of a refinery; (d) passing the heavy fraction through an isomerization dewaxing unit; The above process, comprising:

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