Circular Economy of Waste Plastics to Polyethylene and Base Oil via Refinery & Hydrocracking Units

Abstract

Provided is a continuous process for converting waste plastics to recycle for polyethylene polymerization. The process includes the steps of selecting a waste plastic comprising polyethylene and / or polypropylene, and preparing a blend of petroleum and the selected plastic. The amount of plastic in the blend comprises less than 20 wt% of the blend. The blend is passed to a refinery / hydrocracking unit. Liquefied petroleum gas C 3 -C 4 The olefin / paraffin mixture, and optionally naphtha, is recovered from the hydrocracking unit and passed to a steam cracker for ethylene production. A heavy fraction is also recovered from the hydrocracking unit and may be passed to an isomerization dewaxing unit to prepare base oil.

Description

[Technical field]

[0001] (background) The world has witnessed a very 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, 359 million tonnes in 2018, and 367 million tonnes in 2020. According to McKinsey & Company, global plastic waste is estimated to be 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 this recycled and cleaned polymer pellets are pyrolyzed in pyrolysis units to produce fuels (naphtha, diesel), steam cracker feedstock, or slack wax. The vast majority (>80%) is incinerated, landfilled, or disposed of.

[0003] Current methods of chemical recycling via pyrolysis are not capable of making a significant impact on the plastics industry. Current pyrolysis operations produce poor quality fuel components (naphtha and diesel range products) but in small enough quantities that these products can be blended into the fuel supply. However, to recycle the very large quantities of waste polyethylene and waste polypropylene required to address environmental concerns, such simple blending cannot continue. The raw products from pyrolysis units are too poor quality to be blended in large quantities (e.g., 5-20 vol.% blends) into transportation fuels.

[0004] Processes for converting waste plastics into hydrocarbon lubricants are known. For example, US 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. US 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. US 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. US Patent No. 6,143,940 discloses a procedure for converting waste plastics into heavy wax compositions. US 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 lubricants 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 lubricants.

[0005] US Patent Application Publication No. 2021 / 0130699 discloses a process and system for producing recycle-containing hydrocarbons from recycled waste. The recycled waste is pyrolyzed to form a pyrolysis oil composition, at least a portion of which can be cracked to form a recycled olefin composition.

[0006] Other documents relating to processes for converting waste plastics into lubricants 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 aforementioned patent documents are incorporated herein by reference in their entirety.

[0007] Globally, recycling and upcycling of plastic waste has attracted great interest to save resources and the environment. Mechanical recycling of plastic waste is quite limited due to the different types, properties, additives, and contaminants of the collected plastics. Usually, recycled plastics are of reduced quality. Chemical recycling into starting materials or value-added chemicals has emerged as a more desirable method.

[0008] However, more robust processes are needed for industrial large-scale chemical recycling of single-use plastics to 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 or value-added chemical products or fuels. Summary of the Invention

[0009] Provided is a continuous process for converting waste plastics to recycle for polyethylene polymerization. The process includes selecting waste plastics that include polyethylene and / or polypropylene. These waste plastics are blended with a petroleum feedstock. The resulting blend is generally a stable blend and homogenous mixture, especially at temperatures below the melting point of the waste plastics. The blend contains up to about 20 wt% of the selected waste plastic. The blend is then co-fed to a hydrocracking unit of a refinery along with conventional refinery feedstocks such as VGO.

[0010] Integrating this process into oil refinery is an important aspect of the process and can achieve a circular economy with single-use waste plastics such as polyethylene. Thus, the blend is passed through a refinery hydrocracking unit. The blend is passed at a temperature above the pour point so that the blend can be pumped to the refinery hydrocracking unit. The blend is heated to a temperature above the melting point of the plastic before being injected into the hydrocracking unit. An LPG stream containing C3-C4 hydrocarbons and a naphtha stream containing C5-C8 hydrocarbons are recovered from the hydrocracking unit. The C3-C4 and naphtha streams can be sent to a steam cracker to produce ethylene. A heavy fraction is also recovered from the hydrocracking unit and this fraction is passed through an isomerization / dewaxing unit. Quality base oil is recovered from the dewaxing unit and sent to a hydrofinishing unit for further processing to produce truly premium base oils.

[0011] In another embodiment, the LPG and naphtha (C5-C8) fractions may be recovered from the isomerization / dewaxing unit and passed through a steam cracker to produce ethylene.

[0012] Refineries generally have their own supply of hydrocarbons that flows through the refinery units. A key aspect of this process is that it does not adversely affect the refinery's operations; the refinery must still produce valuable chemicals and fuels. Otherwise, integrating this process into an oil refinery would not be a viable solution. Therefore, the flow rates must be carefully monitored.

[0013] The volume of waste plastic / oil blend flow to the refinery unit can comprise any practical or accommodable volume percent (vol %) of the total flow to the refinery unit. In general, the blend flow rate can be up to about 100 vol.% of the total flow rate (i.e., at this maximum, the blend flow rate is the total flow rate not including the refinery flow rate). In one embodiment, the blend flow rate is up to about 50 vol.% of the total flow rate (i.e., the refinery flow rate and the blend flow rate).

[0014] Among other factors, it has been found that the addition of a refinery operation can efficiently and effectively recycle waste plastics while complementing the refinery operation in the preparation of high value products such as gasoline, jet fuel, base oil and diesel. However, it has also been found that the addition of a refinery operation can efficiently and effectively produce clean ethylene from waste plastics and the ultimate polyethylene polymer. Positive economics are realized throughout the process from recycled plastics to polyethylene products with product quality equivalent to virgin polymer. The process can also recycle waste plastics to prepare fine / premium base oils while also preparing polyethylene products. [Brief description of the drawings]

[0015] [Figure 1]Figure 1 shows the current practice of pyrolyzing waste plastic to produce fuel or wax.

[0016] [Diagram 2] Figure 2 illustrates the present process for preparing a homogenous liquid blend of plastic and petroleum feedstocks at high temperature and feeding the blend to a refining and conversion unit.

[0017] [Diagram 3] FIG. 3 shows the details of the stable blend preparation process and how the stable blend is fed to the purification and conversion unit.

[0018] [Figure 4] Figure 4 shows the classification of plastic types for recycling waste plastics.

[0019] [Diagram 5] Figure 5 shows the process where the prepared blend is passed through a refinery hydrocracking unit.

[0020] [Figure 6] FIG. 6 graphically illustrates the thermogravimetric analysis (TGA) of the thermal stability of polyethylene and polypropylene. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The process provides a method to recycle waste polyethylene and / or waste polypropylene into virgin polyethylene, establishing a circular economy by combining separate industrial processes. In one embodiment, the process and refinery integration can provide premium base oil. Most of the polyethylene and polypropylene polymers are used for single-use plastics and are discarded after use. This single-use plastic waste is becoming an increasingly important environmental issue. At present, there seem to be few options to recycle polyethylene and polypropylene waste plastics into value-added chemicals and fuel products. Currently, only a small amount of polyethylene / polypropylene is recycled via chemical recycling, and the recycled and cleaned polymer pellets are pyrolyzed in a pyrolysis unit to produce fuels (naphtha, diesel), steam cracker feedstock, or slack wax.

[0022] 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 decomposition process that takes place at very high temperatures, up to 850°C.

[0023] 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 main use is in packaging (polyethylene bags, plastic films, geomembranes, bottles and other containers). Polyethylene is produced in three main forms, 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, approx. 0.915-0.940g / cm-3 ), low density polyethylene (LDPE, <0.930g / cm -3 HDPE has low branching and short side chains, whereas LDPE has very high branching and long side chains. LLDPE is a substantially linear polymer with a significant number of short branches and is usually made by the copolymerization of ethylene with short chain alpha olefins.

[0024] 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 atm. This process uses small amounts of oxygen and / or organic peroxide initiators to produce polymers with about 4,000 to 40,000 carbon atoms per average polymer molecule and with a lot of branching. High density polyethylene (HDPE) is produced in the presence of a catalyst at relatively low pressures (10 to 80 atm) and temperatures between 80 and 150 °C. Ziegler-Natta organometallic catalysts (titanium(III) chloride with aluminum alkyls) and Phillips-type catalysts (chromium(IV) oxide supported on silica) are typically used, and the 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 chain length of the polymer. The production conditions for 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).

[0025] Today, due to the inefficiencies and ineffectiveness of the recycling efforts mentioned above, only a small percentage of post-consumer polyethylene products are collected for recycling.

[0026] FIG. 1 shows a diagram of waste plastic fuel or wax pyrolysis as commonly practiced in industry today. Typically, waste plastics are sorted together (1). The cleaned waste plastics 2 are converted to off-gas 4 and pyrolysis oil (liquid products) in a pyrolysis unit 3. The off-gas 4 from the pyrolysis unit is used as fuel to operate the pyrolysis unit. An on-site distillation unit 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 the pyrolysis unit 3 to maximize fuel yield. Char 7 is removed from the pyrolysis unit 3. The heavy fraction 6 is rich in long-chain linear hydrocarbons and is very 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.

[0027] However, in this process, waste plastics are not pyrolyzed. Rather, a stable mixture of petroleum feedstock and waste plastics is prepared. Thus, the pyrolysis step can be avoided, which is a significant energy saving.

[0028] The blend is prepared in a high temperature blend preparation unit with an operating temperature above the melting point of the plastic (approximately 150-250°C) to create a hot, homogeneous liquid blend of plastic and oil that can be fed directly to the refining unit.

[0029] Alternatively, the blend is prepared in a stable blend preparation unit and the hot homogenous liquid blend is cooled in a controlled manner to ambient temperature for easy storage and transport. Using this method, the stable blend can be prepared at a facility remote from the refinery and transported to the refining unit. The stable blend is then heated to a temperature above the melting point of the plastics and fed to the refining conversion unit. The stable blend is a physical mixture of microcrystalline plastic particles finely suspended in a petroleum-based oil. This mixture is stable and the plastic particles do not settle or agglomerate even when stored for long periods of time.

[0030] The significance of heating the blend above the melting point of the plastic is clear when a single plastic is used. However, when the waste plastic is composed of multiple waste plastics, the melting point of the plastic with the highest melting point will be exceeded. Thus, the melting points of all the plastics must be exceeded. Similarly, when the blend is cooled to a temperature below the melting point of the plastic, the temperature must be below the melting points of all the plastics that make up the blend.

[0031] Compared to pyrolysis units, these blend preparation units operate at much lower temperatures (approximately 500-600°C versus 120-250°C). Therefore, the process is a much more energy-efficient process for preparing refined feedstock from waste plastics than thermal decomposition processes such as pyrolysis.

[0032] The use of the waste plastic / petroleum blend of the present invention further increases the overall yield of hydrocarbons obtained from waste plastics. This increase in yield is significant. The hydrocarbon yield using the present blend can reach up to 98%. In contrast, pyrolysis produces a significant amount of light products from plastic waste, about 10-30 wt% and about 5-10 wt% char. These light hydrocarbons are used as fuel to run the pyrolysis plant, as mentioned above. Thus, the liquid hydrocarbon yield from the pyrolysis plant is up to 70-80%.

[0033] When the blend is passed through a refinery unit, such as a hydrocracking unit, only a small amount of off-gas is produced. Refinery units, such as hydrocracking units, use a (catalytic) catalytic cracking process that is different from the thermal cracking process used in thermal cracking. The catalytic process minimizes the production of undesirable light by-products such as methane and ethane. The refinery unit provides efficient product fractionation and allows efficient utilization of all hydrocarbon product streams to produce high value materials. Refinery co-feeds produce only about 2% off-gas (H2, methane, ethane, ethylene). C3 and C4 streams are captured to produce useful products such as cyclic polymer products, while other hydrocarbon streams are captured to produce high quality fuel products such as premium base oils. Thus, the use of the oil / plastic blend of the present invention not only leads to increased hydrocarbons from waste plastics, but also provides a more energy efficient recycling process compared to thermal processing processes such as pyrolysis.

[0034] The process converts single-use waste plastics on a large scale by blending them with petroleum product streams and integrating them into oil refinery operations. The resulting process produces polymer feedstocks (naphtha or C3 and C4, for ethylene crackers only), as well as high-quality gasoline, jet and diesel fuels, and / or high-quality base oils.

[0035] 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 C3 or C4 streams can be fed to the steam cracker. The ethylene is then polymerized to produce polyethylene.

[0036] By adding refining operations to upgrade waste plastics to higher value products (gasoline, jet fuel, diesel, and base oils) and to produce clean ethylene for the production of ultimate polyethylene polymer, positive economics are realized throughout the process from recycled plastics to a polyethylene product with qualities equivalent to virgin polymer. Also, by integrating the recycling process with an oil refining operation, a more energy efficient and effective process is achieved while avoiding the problems of refining operations.

[0037] The integration of refinery operations is also very important in another aspect. Waste plastics contain contaminants such as calcium, magnesium, chlorides, nitrogen, sulfur, dienes, and heavy components, and their products cannot be used in large quantities for blending transportation fuels. It has been found that by passing these products through a refinery unit, the contaminants can be captured in a pre-treatment unit and their negative impacts can be reduced. The fuel components can be further upgraded in a suitable refinery unit using chemical conversion processes, and the final transportation fuel produced by the integrated process can be of higher quality and meet the fuel quality requirements. The integrated process produces a much cleaner and purer ethylene stream for polyethylene production. The mass production of these specifications makes the "circular economy" of recycled plastics possible.

[0038] The carbon going in and out of the refinery is “transparent,” meaning that not all molecules from the waste plastics are cycled back to the polyolefin plant and become the exact olefin product, but it is nevertheless considered a “credit” since the net “green” carbon going in and out of the refinery is positive. These integrated processes result in a significant reduction in the amount of virgin feedstock required for a polyethylene plant.

[0039] In some cases, the energy required to convert waste plastics into clean fuels is less than the energy required to produce fuels and base oils from virgin petroleum feedstocks. Energy efficiency improvements will continue to improve as waste plastic collection and processing improves. Such fuels and base oils produced from blends of waste plastics and oils contain recycled content and have a lower carbon footprint than the corresponding fuels and base oils produced from pure petroleum feedstocks. The process allows the production of clean gasoline, jet fuel, diesel, and base oils from waste plastics that contain recycled content and have a lower CO2 footprint (low carbon footprint).

[0040] FIG. 2 shows a method for preparing a hot homogenous blend of plastics and oil feedstocks for use in the present process, which is injected directly into a refinery hydrocracking unit, in which a hot homogenous liquid blend of plastics and oil is prepared in a hot blend preparation unit. The preferred range of plastic composition in the blend is about 1-20 wt%. When high molecular weight polypropylene (average molecular weight 250,000 or more) waste plastics or high density polyethylene (density greater than 0.93 g / cc) are primarily used as waste plastics, for example at least 50 wt%, the amount of waste plastics used in the blend is more preferably about 10 wt%. This is because the pour point and viscosity of the blend will be higher.

[0041] Preferred conditions for the preparation of hot homogenous liquid blends include vigorously mixing the plastic with the petroleum feedstock while heating it to a temperature above the melting point of the plastic. Preferred process conditions include heating to a temperature of 250-550°F, a residence time at the final heating temperature of 5-240 minutes, and atmospheric pressure of 0-10 psig. This can be done in open air or preferably under an oxygen-free inert atmosphere.

[0042] Referring to FIG. 2 of the drawings, a step-by-step preparation process for preparing a hot homogenous liquid blend is shown. The mixed waste plastics are sorted to produce post-consumer waste plastics 21 including polyethylene and / or polypropylene. The waste plastics are cleaned (22) and then mixed with oil 24 in a hot blend preparation unit 23. After mixing in 23, a homogenous blend of plastics and oil is recovered (25). Optionally, a filtration device can be added (not shown) to remove undissolved plastic particles or solid impurities present in the hot liquid blend. The hot blend of plastics and oil can then be combined with a refinery feedstock such as vacuum gas oil (VGO) 20 to produce a mixture of plastic / oil blend and VGO 26, which can then be passed to a refining unit. In this process, in one embodiment, the refining unit is a hydrocracking unit.

[0043] FIG. 3 shows a method for preparing a stable blend of plastics and oil for use in the present process. The stable blend is made by a two-step process in a stable blend preparation unit. In the first step, a hot homogeneous liquid blend of plastic melt and oil feedstock is produced. This step is the same as the hot blend preparation described in FIG. 2. The preferred range of plastic composition in the blend is about 1-20 wt%. If high molecular weight polypropylene (average molecular weight ≧250,000) waste plastics or high density polyethylene (density above 0.93 g / cc) are mainly used as waste plastics, for example at least 50 wt%, the amount of waste plastic used in the blend is more preferably about 10 wt%. The reason is that the pour point and viscosity of the blend will be higher.

[0044] Preferred conditions for the preparation of hot homogenous liquid blends include vigorously mixing the plastic with the petroleum feedstock while heating it to a temperature above the melting point of the plastic. Preferred process conditions include heating to a temperature of 250-500°F, a residence time at the final heating temperature of 5-240 minutes, and atmospheric pressure of 0-10 psig. This can be done in open air or preferably under an oxygen-free inert atmosphere.

[0045] In the second step, the hot blend is cooled to a temperature below the melting point of the plastic while being continuously and vigorously mixed with the oil feedstock, and then further cooled to a lower temperature, preferably ambient temperature, to produce a stable blend of plastic and oil.

[0046] Stable blends are found to be an intimate physical mixture of plastics and petroleum feedstocks. The plastics are in a "deagglomerated" state. The plastics maintain a fine dispersion of solid particles in the petroleum feedstock at temperatures below the melting point of the plastics, especially at ambient temperatures. The blends are stable and easy to store and transport. At the refinery, the stable blend is heated in a preheater above the melting point of the plastics to produce a hot homogenous liquid blend of plastics and petroleum. This hot liquid blend can then be fed to the refinery / hydrocracking unit as a co-feed along with conventional refinery feedstocks.

[0047] Further details of the preparation of the stable blend are shown in FIG. 3. The stable blend is made by a two step process in the stable blend preparation unit 100. As shown, clean waste 22 is passed through the stable blend preparation unit 100. Selected plastic waste 22 is heated and mixed with refinery feedstock oil 24. The plastic waste is heated to a temperature above the melting point of the plastic to melt the plastic. The petroleum feedstock is mixed with the heated plastic at 23. The mixing is often very vigorous. The mixing and heating conditions can generally be heating at a temperature in the range of about 250-500°F with a residence time of 5-240 minutes at the final heating temperature. The heating and mixing can be done in open air or under an oxygen-free inert atmosphere. The result is a hot homogenous liquid blend of plastic and oil 25. Optionally, a filtration device can be added (not shown) to remove any undissolved plastic particles or solid impurities present in the hot homogenous blend.

[0048] The hot blend 25 is then cooled to a temperature below the melting point of the plastic while continuing to mix with the oil feedstock 101. Cooling is typically continued to ambient temperature to produce a stable blend of plastic and oil 102. At the refinery, the stable blend can be fed to a preheater 50, which heats the blend to a temperature above the melting point of the plastic to produce a mixture of plastic / oil blend and VGO 26, which is then fed to a refinery conversion unit, such as a hydrocracking unit.

[0049] The preferred plastic starting material for the process is sorted waste plastics containing mainly polyethylene and polypropylene (plastic recycling classification types 2, 4, and 5). The pre-sorted waste plastics are washed, shredded or pelletized, and fed to the blend preparation unit. Figure 4 shows the plastic type classification for waste plastics 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 the process. Polystyrene (class 6) can also be present in limited amounts.

[0050] Proper sorting of waste plastics is very important to minimize contaminants such as N, Cl, and S. Plastic waste including polyethylene terephthalate (Plastic Recycle Classification Type 1), polyvinyl chloride (Plastic Recycle Classification Type 3) and other polymers (Plastic Recycle 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 Recycle Classification Type 6). Waste polystyrene should be sorted to less than 20%, preferably less than 10%, and most preferably less than 5%.

[0051] Washing of waste plastics can remove metal contaminants such as sodium, calcium, magnesium, aluminum, and 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 fluorides, chlorides, iodides, etc. Residual metal, non-metallic contaminants, and halides should be removed to less than 50 ppm, preferentially less than 30 ppm, and most preferentially less than 5 ppm.

[0052] If washing does not adequately remove the metal, non-metallic contaminants, and halide impurities, a separate guard bed can be used to remove the metal and non-metallic contaminants.

[0053] The petroleum with which the waste plastics are blended is generally the petroleum feedstock for the refinery. The petroleum blend oil is preferably the same as the petroleum feedstock for the refinery. The petroleum may also include petroleum-derived oil or petroleum-based materials. In one embodiment, the petroleum feedstock may include atmospheric gas oil, vacuum gas oil (VGO), atmospheric resid, or heavies recovered from other refining operations. In one embodiment, the petroleum feedstock with which the waste plastics are blended includes VGO. In one embodiment, the petroleum feedstock with which the waste plastics are blended includes light cycle oil (LCO), heavy cycle oil (HCO), FCC naphtha, gasoline, diesel, toluene, and / or petroleum-derived aromatic solvents.

[0054] FIG. 5 illustrates one embodiment of the integrated process of the present invention where the blend is sent to a hydrocracking unit. Like numbers in FIG. 5 corresponding to FIG. 2 and FIG. 3 refer to the same items / units. As shown, selected waste 21 is cleaned (2) and then passed to a blend preparation unit 23 where plastics and refinery feedstocks 24 are blended to create a hot blend of plastics and oil 25. This blend can optionally have additional refinery feedstocks such as vacuum gas oil (VGO) 20 added to it. If the plastic / oil blend is still hot (25 in FIG. 2), it can be immediately mixed with the co-feed oil 20. However, if the stable blend of plastic / oil needs to be heated for storage or transportation (102 in FIG. 3), the blend is generally heated to above the melting point of the plastics using, for example, a preheater (preheater 50 in FIG. 3) before being mixed with the co-feed VGO oil. This homogenous plastic / oil blend and VGO oil 26 are then sent to the hydrocracking unit 27 of the refinery. In another embodiment, the heated blend and the refinery stock co-feed are each passed directly, but separately, to a hydrocracking unit.

[0055] Refineries generally have their own hydrocarbon feed that flows through the refinery unit. In this case, the hydrocarbon feed is VGO20, as shown in FIG. 5. The volume of the blend stream flowing to the refinery unit (here the hydrocracking unit) can constitute any practical or accommodable volume percent (vol%) of the overall stream (total flow) to the refinery unit. In general, the blend flow rate can be up to about 50 vol% of the total flow rate (i.e., refinery flow rate and blend flow rate) for practical reasons. In one embodiment, the blend flow rate is up to about 100 vol% of the total flow rate. In another embodiment, the blend volumetric flow rate is up to about 25 vol% of the total flow rate. About 50 vol% has been found to be a very practical amount in terms of impacts on the refinery, while at the same time providing good results and being accommodable. It is important to avoid adverse effects on the refinery and its products. If the amount of plastic in the final blend (including the plastic / oil blend and the co-feed oil) exceeds 20 wt% of the final blend, problems may arise in the operation of the refinery unit. Final blend means the plastic / oil blend and any co-feed petroleum. The plastic / oil blend may comprise up to 100% by volume of the feed to the refinery unit and as such may comprise the entire final blend.

[0056] Any suitable hydrocracking operation may be carried out. The catalyst in the hydrocracker may be selected from any known hydrocracking catalyst. Hydrocracking conditions generally include temperatures ranging from 175° C. to 485° C., hydrogen to hydrocarbon molar ratios ranging from 1 to 100, pressures ranging from 0.5 to 350 bar, and liquid hourly space velocities (LHSVs) ranging from 0.1 to 30. In the hydrocracking reactor, larger molecules are cracked into smaller molecules. Hydrocracking catalysts typically include various combinations of large pore zeolites, such as USY, and Group VI and Group VIII base metals, such as nickel, cobalt, molybdenum, and tungsten, finely dispersed on an alumina or oxide support.

[0057] From the hydrocracking unit 27, a C3-C4 stream 30 of LPG, a clean naphtha stream 31, and a heavy fraction 28 are recovered. The heavy fraction 28 is passed to an isomerization / dewaxing unit 29. Within the hydrocracking reactor, the feed may first be contacted with a hydrotreating catalyst under hydrotreating conditions in a hydrotreating zone or guard bed to provide a hydrotreated feed. Hydrotreating catalysts typically contain various combinations of Group VI and Group VIII base metals, such as nickel, cobalt, molybdenum, and tungsten, finely dispersed on an alumina or oxide support. Contacting the feed with the hydrotreating catalyst in the guard bed can effectively hydrogenate aromatics in the feed and remove N- and S-containing compounds from the feed to protect the hydroisomerization catalyst of the catalytic system. By "effectively hydrogenating aromatics," it is meant that the hydrotreating catalyst can reduce the aromatic content of the feed by at least about 20%. The hydrotreated feed generally contains C 10+ n-paraffins and slightly branched isoparaffins, and the wax content is typically at least about 20%.

[0058] Hydroisomerization catalysts useful in the present process typically contain catalytically active hydrogenation metals. The presence of catalytically active hydrogenation metals results in product improvements, particularly in VI and stability. Typical catalytically active hydrogenation metals include chromium, molybdenum, nickel, vanadium, cobalt, tungsten, zinc, platinum, and palladium. The metals platinum and palladium are particularly preferred, with platinum being most particularly preferred. When platinum and / or palladium are used, the total amount of active hydrogenation metals typically ranges from 0.1 wt% to 5 wt% of the total catalyst, usually 0.1 wt% to 2 wt%. Additionally, hydroisomerization catalysts typically contain a medium pore size zeolite, such as ZSM-23, ZSM-48, ZSM-35, SSZ-32, SSZ-91, etc., dispersed on an oxide support.

[0059] The refractory oxide support may be selected from oxide supports conventionally used in catalysts, including silica, alumina, silica-alumina, magnesia, titania, and combinations thereof.

[0060] Conditions within isomerization / dewaxing reactor unit 29 generally include a temperature range of about 390° F. to about 800° F. (199° C. to 427° C.). In one embodiment, the hydroisomerization dewaxing conditions include a temperature range of about 550° F. to about 700° F. (288° C. to 371° C.). In a further embodiment, the temperature may range from about 590° F. to about 675° F. (310° C. to 357° C.). The total pressure may range from about 500 to about 3000 psig (0.10 to 20.68 MPa), typically from about 750 to about 2500 psig (0.69 to 17.24 MPa).

[0061] From the isomerization / dewaxing unit 29, a dewaxed oil 33 can be recovered, which can be used as a base oil. The oil can also be passed to a hydrofinishing unit 34 to prepare a premium base oil 35. In the hydrofinishing unit 34, hydrofinishing can be carried out in the presence of a hydrofinishing catalyst, as known in the art. The hydrofinishing catalyst used in hydrofinishing can include, for example, platinum, palladium, or combinations thereof on an alumina support. Hydrofinishing can be carried out at temperatures ranging from about 350°F to about 650°F (176°C to about 343°C) and pressures ranging from about 400 psig to about 4000 psig (2.76 to 27.581 MPa). Hydrofinishing to produce lubricating oils is described, for example, in U.S. Pat. No. 3,852,207, the disclosure of which is incorporated herein by reference.

[0062] The LPG stream 30 and the clean naphtha stream 31 can be passed to a steam cracker 40 to produce ethylene 36. The naphtha stream 31 also contains clean gasoline, jet fuel, and diesel fuel fractions, and therefore can be passed in whole or in part to the steam cracker 40. At least a portion of the naphtha stream 31 can also be passed to a gasoline pool or upgrading process to upgrade the fuel fractions, particularly jet fuel. From the dewaxing unit 29, LPG and naphtha can also be recovered (32) and passed to the steam cracker 40 as feedstocks to produce ethylene 36. The ethylene is sent to an ethylene polymerization unit 41 to produce polyethylene, which is further processed to produce a variety of polyethylene products 42 tailored to consumer needs.

[0063] The steam cracker and ethylene polymerization unit are preferably located near the refinery so that the feedstock (propane, butane, naphtha, or ethylene) can be transported via pipeline. For petrochemical plants located remotely from the refinery, the feedstock can be delivered via truck, barge, rail car, or pipeline.

[0064] The benefits of a circular economy and effective and efficient recycling campaigns are realised through this integrated process.

[0065] The following examples are provided to further illustrate the present process and its advantages. These examples are intended to be illustrative and not limiting. EXAMPLES

[0066] [Example 1] Characteristics of plastic samples and raw materials used for blend preparation

[0067] Four plastic samples were purchased (low density polyethylene (LDPE, Plastic A), high density polyethylene (HDPE, Plastic B), and two polypropylene samples with average molecular weights of approximately 12,000 (PP, Plastic C) and approximately 250,000 (PP, Plastic D)) and their properties are summarized in Table 1. [Table 1]

[0068] The petroleum feedstocks used to prepare stable blends with plastics include hydrotreated vacuum gas oil (VGO), Aromatic 100 solvent, light cycle oil (LCO), and diesel, the properties of which are shown below in Table 2. Aromatic 100 is a commercially available aromatic solvent produced from petroleum-based materials and contains primarily C9-C10 di- and tri-alkylbenzenes. [Table 2]

[0069] Thermogravimetric analysis (TGA) was performed on Plastic A (LDPE) and Plastic C (polypropylene) to confirm that the plastic materials are thermally stable at temperatures well above the melt preparation temperature. The TGA results, shown in Figure 6, indicate that the LDPE sample is stable up to 800°F and the polypropylene sample is stable up to 700°F.

[0070] [Example 2] Feedstock for C3-C4 and / or naphtha production from co-feeding waste plastic / oil blends to refinery / hydrocracking units

[0071] By feeding the plastic / oil blend, with or without a co-feed, to a hydrocracking unit, the blend is converted and fractionated into components. The refinery / hydrocracking unit produces large amounts of clean propane, butane, and naphtha streams, as well as other streams for the refining and conversion units, as well as streams for polyethylene production.

[0072] [Example 3] Hydrocracking of plastic and petroleum blends to produce fuels and base oils with recycled content and a low CO2 footprint

[0073] Gasoline, jet fuel, diesel, and heavy cuts from the hydrocracker effluent distillation column are sent to corresponding blending pools and can be blended into finished gasoline, jet fuel, diesel, or marine oils with recycled content and low CO2 footprint. A portion of the heavy fraction can be further processed in an isomerization / dewaxing unit to prepare base oils or white oils with recycled content and low CO2 footprint (Figure 5).

[0074] [Example 4] Feeding recycled C3-C4 and / or naphtha to a steam cracker for the production of ethylene and subsequent production of polyethylene resins and polyethylene consumer products, and base oil production

[0075] According to Example 2, propane, butane, and naphtha streams are produced via co-feeding the plastic / oil blend to a hydrocracking unit, and these streams are suitable feedstocks to be co-fed to a steam cracker to produce ethylene containing recycled content. At least some, if not all, of these streams can be fed to a steam cracker. The ethylene can be processed in a polymerization unit to produce polyethylene resins containing recycled polyethylene / polypropylene derived materials, but the quality of the newly produced polyethylene is indistinguishable from virgin polyethylene made entirely from virgin petroleum resources. This polyethylene resin containing recycled materials can be further processed to produce a variety of polyethylene products to meet consumer product needs. These polyethylene consumer products contain chemically recycled circular polymers, but the quality of those products is indistinguishable from those made entirely from virgin polyethylene polymers. These chemically recycled polymer products are different from mechanically recycled polymer products, which are of inferior quality to polymer products made from virgin polymers (Figure 5).

[0076] The heavy fraction from the hydrocracking unit can also be passed to an isomerization / dewaxing unit. Dewaxed oil, or base oil, is recovered from the unit, which can be further passed to a hydrofinishing unit to prepare premium base oils or white oils (Figure 5).

[0077] 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 that are essential to the composition. The phrase "consisting of" or "consists of" is intended as a transitional phrase, meaning the exclusion of all other than the recited elements, except for only trace impurities.

[0078] All patents and publications referenced herein are incorporated herein by reference to the extent that they are not inconsistent therewith. It will be understood that the specific above-described 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 the exemplary embodiment or embodiments. It will be further 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. Thus, it will 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. A continuous process for converting waste plastics into recycling for polyethylene polymerization, comprising: (a) selecting waste plastics comprising polyethylene and / or polypropylene; (b) preparing a blend of petroleum and the selected waste plastic, the blend comprising no more than 20 wt.% of the selected waste plastic; (c) passing the blend through a refinery hydrocracking unit at a temperature above the melting point of the waste plastics in the blend; (d) extracting liquefied petroleum gas C from the hydrocracking unit. ３ -C ４ recovering the olefin / paraffin mixture; (e) The above C ３ -C ４ passing the mixture through a steam cracker to produce ethylene; The above process comprising:

2. 10. The process of claim 1, wherein a naphtha stream is also recovered from the hydrocracking unit and at least a portion is passed to a steam cracker as a feedstock for the production of ethylene.

3. 2. The process of claim 1, wherein the blend of (b) is a high temperature homogenous blend of waste plastic and petroleum.

4. 2. The process of claim 1, wherein the blend of (b) is a stable blend of waste plastic and petroleum.

5. 2. The process of claim 1 wherein ethylene is polymerized into polyethylene.

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

7. 10. The process of claim 1, wherein gasoline is recovered from a refinery hydrocracking unit and sent to a gasoline blending pool.

8. 3. The process of claim 2, wherein a portion of the naphtha stream is recovered from the hydrocracking unit and further processed in a refinery to obtain clean gasoline, diesel, or jet fuel.

9. 10. The process of claim 8, wherein jet fuel is recovered from further processing in a refinery.

10. 2. The process of claim 1, wherein the volumetric flow rate of the blend in (c) flowing to the refinery / hydrocracking unit comprises up to about 100 vol.% of the total hydrocarbon flow rate flowing to the hydrocracking unit.

11. 2. The process of claim 1, wherein the volumetric flow rate of the blend in (c) flowing to the refinery / hydrocracking unit comprises up to about 50 vol.% of the total hydrocarbon flow rate flowing to the hydrocracking unit.

12. 12. The process of claim 11, wherein the blended flow rate comprises up to about 25 vol.% of the total flow rate to the hydrocracking unit.

13. 2. The process of claim 1, wherein in (b) the blend of petroleum and selected waste plastic is prepared by heating the waste plastic to a temperature above the melting point of the plastic, mixing with petroleum, and then cooling the blend to a temperature below the melting point of the waste plastic.

14. 2. The process of claim 1, wherein the petroleum oils in the blend include atmospheric gas oils, vacuum gas oil (VGO) atmospheric resid, petroleum derived oils, petroleum based materials, and / or heavies recovered from refining operations.

15. 2. The process of claim 1, wherein the petroleum in the blend comprises light cycle oil (LCO), heavy cycle oil (HCO), FCC naphtha, gasoline, diesel, toluene, and / or petroleum derived aromatic solvents.

16. 10. The process of claim 1, wherein a heavy fraction is recovered from the hydrocracking unit and passed to an isomerization / dewaxing unit.

17. 17. The process of claim 16, wherein the base oil is recovered from an isomerization / dewaxing unit.

18. 20. The process of claim 17, wherein the recovered base oil is passed to a hydrofinishing unit.

19. 17. The process of claim 16, further comprising recovering a naphtha fraction from the isomerization / dewaxing unit and passing at least a portion of the naphtha fraction through a steam cracker to produce ethylene.

20. 1. A process for converting waste plastics into chemicals useful for the preparation of polyethylene, comprising: (a) selecting waste plastics comprising polyethylene and / or polypropylene; (b) preparing a blend of petroleum and the selected waste plastic, the blend comprising no more than 20 wt.% of the selected plastic; (c) passing the blend through a refinery hydrocracking unit; Including the above process.

21. A continuous process for converting waste plastics into recycling for the preparation of base oil, comprising: (a) selecting waste plastics comprising polyethylene and / or polypropylene; (b) preparing a blend of petroleum and the selected waste plastic, the blend comprising no more than 20 wt.% of the selected waste plastic; (c) passing the blend through a refinery hydrocracking unit at a temperature above the melting point of the plastics in the blend; (d) recovering a heavy fraction from said hydrocracking unit and passing said heavy fraction to a refinery and isomerization / dewaxing unit; (e) recovering a base oil from the isomerization / dewaxing unit; The above process comprising:

22. 22. The process of claim 21, wherein the base oil recovered in (e) is passed to a hydrofinishing unit from which a hydrofinished base oil is recovered.

23. A process for converting waste plastics into recycling for the preparation of low carbon footprint fuels, comprising: (a) selecting waste plastics comprising polyethylene and / or polypropylene; (b) preparing a blend of petroleum and the selected waste plastic, the blend comprising no more than 20 wt.% of the selected plastic; (c) passing the blend through a refinery hydrocracking unit at a temperature above the melting point of the plastics in the blend; (d) recovering a heavy fraction from said hydrocracking unit and passing said heavy fraction to a refinery and isomerization / dewaxing unit; (e) recovering a base oil from the isomerization / dewaxing unit; Including the above process.

24. 24. The process of claim 23, wherein the low carbon footprint fuel comprises gasoline, jet fuel, diesel, and / or marine oil.

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