Process for Stable Blend of Waste Plastic with Petroleum Feed for Feeding to Oil Refinery Units and Process of Preparing Same

This application is a divisional application of U.S. application Ser. No. 18/349,343, filed Jul. 10, 2023, claims priority to U.S. Provisional Application Ser. No. 63/387,041 filed Dec. 12, 2022, the complete disclosures of which are incorporated herein by reference in their entirety.

The world has seen extremely rapid growth of plastics production. According to PlasticEurope Market Research Group, the world's plastics production was 335 million tons in 2016, 348 million tons in 2017 and 359 million tons in 2018. According to McKinsey & Company, the global plastics-waste volume was estimated about 260 million tons per year in 2016 and projected to be 460 million tons per year by 2030 if the current trajectory continues.

Single use plastic waste has become an increasingly important environmental issue. At the moment, there appear to be few options for recycling polyethylene and polypropylene waste plastics to value-added chemicals and fuel products. Currently, only a small amount of polyethylene/polypropylene is recycled via chemical recycling, where recycled and cleaned plastic pellets are pyrolyzed in a pyrolysis unit to make fuels (naphtha, diesel), steam cracker feed or slack wax. The majority, greater than 80%, is incinerated, land filled or discarded.

The current method of chemical recycling via pyrolysis cannot make a big impact for the plastics industry. The current pyrolysis operation produces poor quality fuel components (naphtha and diesel range products), but the quantity is small enough that these products can be blended into fuel supplies. However, this simple blending cannot continue if we have to recycle very large volumes of waste polyethylene and polypropylene to address the environmental issues. The products as produced from the pyrolysis unit have too poor quality to be blended in large amounts (for example 5-20 volume % blending) in transportation fuels.

Processes are known which convert waste plastic into hydrocarbon lubricants. For example, U.S. Pat. No. 3,845,157 discloses 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. Pat. No. 4,642,401 discloses the production of liquid hydrocarbons by heating pulverized polyolefin waste at temperatures of 150-500° C. and pressures of 20-300 bars. U.S. Pat. No. 5,849,964 discloses a process in which waste plastic materials are depolymerized into a volatile phase and a liquid phase. The volatile phase is separated into a gaseous phase and a condensate. The liquid phase, the condensate and the gaseous phase are refined into liquid fuel components using standard refining techniques. U.S. Pat. No. 6,143,940 discloses a procedure for converting waste plastics into heavy wax compositions. U.S. Pat. No. 6,150,577 discloses a process of converting waste plastics into lubricating oils. EP0620264 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 a hydrotreatment, then catalytically isomerizing and fractionating to recover a lubricating oil.

U.S. Publication No. 2021/0130699 discloses processes and systems for making recycle content hydrocarbons from recycled waste material. The recycle waste material is pyrolyzed to form a pyrolysis oil composition, at least a portion of which may then be cracked to form a recycle olefin composition.

Other documents which relate to processes for converting waste plastic into lubricating oils include U.S. Pat. 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 entirety.

Globally, recycling or upcycling of plastic waste has gained great interest to save resources and the environment. Mechanical recycling of plastic waste is rather limited due to different types, properties, additives, and contaminants in the collected plastics. Usually, the recycled plastics are of degraded quality. Chemical recycling to the starting material or value-added chemicals has emerged as a more desirous route.

However, in order to achieve chemical recycling of single use plastics in an industrially significant quantity to reduce their environmental impact, more robust processes are needed. Such a process may require unique handing and manipulation of the waste plastic. If the plastics are to be used in preparing a feed to a refinery, of particular concern is the presence of chloride. Refinery units have low chloride tolerances. Chlorides in a feed stream may cause corrosion of refinery equipment and vessels, and may produce poor quality fuels and chemicals.

In one embodiment, provided is a composition of a stable blend of waste plastic and a petroleum based feedstock for direct conversion of waste plastic in a refinery process unit. In one embodiment, the blend comprises less than 100 ppm chloride. In another embodiment, the blend comprises less than 10 ppm chloride. In another embodiment, the blend comprises less than 5 ppm chloride.

The stable blend comprises a petroleum based feedstock and 1-20 weight % of plastic. The plastic, in one embodiment, is comprised of mostly polyethylene and/or polypropylene. The plastic in the blend is present as finely dispersed microcrystalline particles having an average particle size of 10 micron to less than 100 microns, preferentially less than 80 microns. The blend can also comprise less than 5 ppm chloride.

Also provided in one embodiment is a process for preparing a blend of plastic and petroleum. The process comprises mixing a petroleum based feed or in one embodiment a bio-feed, and a plastic together, and heating the mixture at a temperature of about 600° to 800° F. (206° to 427° C.), preferentially 550° to 700° F. (288° to 371° C.) for a residence time of 5-240 minutes. The resulting blend is then filtered hot to remove any contaminants including glass, metals, PVC, or other plastics. The filtered liquid product is optionally treated further with a chloride removal guard bed catalyst. The resulting blend comprises less than 100 ppm chloride, and more preferably less than 10 ppm chloride. The blend can then be fed to a refinery unit or cooled for storage.

Among other factors, the present process prepares a blend of plastic and a petroleum based feedstock, which contains minimal, if any chloride, e.g., in one embodiment less than 10 ppm chloride, or even less an 5 ppm chloride. The blend is close to, if not essentially, free of chloride. The present process also executes chloride removal with a minimal number of steps.

This essentially chloride free blend of plastic and petroleum based feedstock provides a vehicle to efficiently and effectively feed waste plastic to refinery processes for conversion of the waste plastic to high volume products, with good yields. It has been found that by preparing the present blend and feeding the blend to refinery operations, one can efficiently, effectively, and safely recycle plastic waste while also complementing the operation of a refinery in the preparation of higher value products such as gasoline, jet fuel, base oil, and diesel fuel. Polyethylene and polypropylene can also be produced from the waste plastics efficiently and effectively. In fact, positive economics are realized for the overall recycling process with product quality identical to that of virgin polymer. The use of the present blend also saves energy and is more environmentally friendly than prior recycling processes. The minimal, if any, chloride contained in the blend allows the blend to be safely passed through a refinery without damaging the equipment and refinery units, as the present art discloses a process for reducing the chloride contents to levels that fall below unit operating limits. In one embodiment, the feedstock with which the plastic is mixed can comprise a bio-feed. The bio-feed can be used alone or in combination with the petroleum based feedstock.

Disclosed are a novel plastic and petroleum based feedstock blend, and a process to prepare a stable blend of a plastic and a petroleum based feedstock comprising minimal, if any, chloride, metals and other plastic contaminants for direct conversion of plastic in a refinery process unit. In one embodiment, the feedstock mixed with the plastic can comprise a bio-feed feedstock. The bio-feed can comprise the entire feedstock, or can be used in combination with a petroleum based feedstock.

In one embodiment, provided is a process for preparing a stable blend of plastic, preferably waste plastic, and petroleum for storage, transportation or feeding to a refinery unit with the blend comprising minimal, if any, chloride. By minimal, if any chloride, is meant that the amount of chloride present in the blend is less than 100 ppm chloride, or even less than 10 ppm chloride, and less than 5 ppm chloride. Minimal amounts of metals and other plastic contaminants are also desired and achieved. The process comprises first selecting plastics, preferably waste plastics, containing polyethylene and/or polypropylene. These waste plastics are then passed through a blend preparation unit to make a stable blend of waste plastic and petroleum comprising minimal, if any, chloride, metals and other plastic contaminants. The stable blend can then be safely fed to a refinery conversion unit for direct conversion of waste plastic to value-added chemicals and fuels.

The stable blend is made by a two or three-step process. The first step produces a hot, homogeneous liquid blend of plastic melt and petroleum feedstock. The preferred range of the plastic composition in the blend is about 1-20 wt. %. The preferred conditions for the hot liquid blend preparation include heating plastic above the melting point of the plastic while vigorously mixing with petroleum feedstock. The preferred process conditions include heating to a temperature in the range of about 500-800° F., preferentially in the range of about 550°-700° F., a residence time of 5-240 minutes at the final heating temperature, and 0-20 psig atmospheric pressure. The temperature used is one that will decompose PVC without substantially decomposing any of the other plastics. By keeping the temperature at about 550° to 700° F., only polyvinyl chloride decomposes to HCl and hydrocarbons. At this temperature range, polyethylene and polypropylene stay in the melted state but are not decomposed. By minimizing the decomposition of polyethylene and polypropylene, the amounts of olefins and dienes in the blend are limited, and this will minimize formation of organic chlorides which can be made by reaction of olefins and HCl. A stripping gas such as nitrogen, hydrogen, steam, or offgas from a conversion unit may be added to facilitate purging of HCl offgas from the decomposition of PVC or organic chlorides in the blend. Hydrogen may be a preferred stripping gas as it facilitates HCl formation and minimizes diene formation. The preferred conditions include heating to 550° to 700° F. temperature, a residence time of 5-240 minutes at the final heating temperature, and 0-200 psig pressure with 100-1500 scf/bbl of stripping gas. By keeping the temperature at about 550° to 700° F., only polyvinyl chloride decomposes to HCl and hydrocarbons. At this temperature range, polyethylene and polypropylene stay in the melted state but are not decomposed. By minimizing the decomposition of polyethylene and polypropylene, the amounts of olefins and dienes in the blend are limited, and this will minimize the formation of organic chlorides which can be made by reactions of olefins and HCl.

shows the thermal stability of polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC) plastics determined by thermal gravimetric analysis (TGA). PVC decomposes at the 450°-700° F. temperature range via dehydrochlorination to form polyene and HCl gas. At the temperature above 700° F., the polyene further decomposes to low-molecular weight compounds. Any offgas from the heating, which would contain hydrogen chloride, is treated with a scrubber. This can be done in the open atmosphere as well as preferably under an oxygen-free inert atmosphere.

Polyethylene is stable up to 800° F. and polypropylene is stable up to 700° F. Vacuum gas oil (VGO) is stable at all temperature range from ambient to 1200° F. The weight change of VGO shown inis due to the light components boils off from VGO as light hydrocarbon. To minimize the light hydrocarbon loss from the VGO, it is preferred to operate this chloride stripping process at an elevated pressure, for example above 10 psig, preferentially above 50 psig. Alternatively, an overhead condenser may be installed to condense the light hydrocarbon vapor back to liquid.

The second step involves hot filtering the blend mixture to remove any contaminants. The contaminants can include glass, metal, paper, PVC or other plastics with a low solubility such as PS and PETE and other Group 7 plastics, and inorganic filler materials used in plastic manufacturing. This filtration step allows most of the PVC, PETE, other plastics and bulk of inorganic impurities to be removed.

The last, or third step comprises optional treating of filtered liquid product recovered from the second step with a chloride removal guard bed catalyst. Such catalyst beds are known in the industry to be effective in reducing chlorides to low ppm levels. In one embodiment, the catalyst beds are based on oxides such as CaO or MgO or based on hydroxides, such as Fe(OH). Such catalyst guard beds are available, for example, from Dorf Ketal, BASF, Evonik, Johnson Matthey, Clariant and Axens. The preferred conditions include treating at 250° to 700° F. temperature, a residence time of 5-240 minutes, and 0-200 psig pressure. An appropriate temperature can be selected should any further decomposition of PVC be needed. The resulting blend can now be safely fed to a refinery directly or cooled and stored for subsequent use. The subsequent use can comprise being fed to a refinery or transported and fed to a refinery.

For storage, the hot blend is cooled down below the melting point of the plastic while continuously, vigorously mixing, and then further cooling down to a lower temperature, preferably ambient temperature, to produce a stable blend. The stable blend is either an oily liquid or in a waxy solid state at ambient temperature depending on the petroleum feedstock and plastic content and type. Since the blend is stable, it can be stored for lengthy time periods.

In one embodiment, the stable blend is made of a petroleum feedstock and 1-20 wt. % of waste plastic, wherein the plastic is in the form of finely dispersed micron-size particles with 10 microns to less than 100-microns average particle size. In one embodiment, the feedstock material in the blend can comprise a bio-feed material.

There are several advantages realized by the present blend and its use. For example, the stable blend of plastic and petroleum feedstock can be stored at ambient temperature and pressure for extended time periods. During the storage, no agglomeration, no settling of polymer particles and no chemical/physical degradation of the blend are observed. This allows easier handling of the waste plastic material for storage or transportation.

The stable blend can be handled easily by using standard pumps as are typically used in refineries or warehouses, or by using pumps equipped with transportation tanks. Depending on the blend, some heating of the blend above its pour point is required to pump the blend for transfer or for feeding to a conversion unit in a refinery. During the heating, no agglomeration of polymer is observed.

Another major advantage of the present blend, and the process of preparing the blend, is the removal of chloride to levels of less than 100 ppm, or even 10 ppm and less. Since refinery units have low chloride tolerance, the present blends can safely be provided to a refinery.

Another major advantage of the present blend, and the process of preparing the blend, is that it can be applied to multi-layer film plastic that is considered non-recyclable via current recycling processes. These multi-layer films comprise polyethylene and/or polypropylene layers, but also a thin metallic layer as a metallic barrier layer. This metallic layer often comprises aluminum as the metal. The polyethylene and polypropylene components in the multilayer film can be dissolved selectively in the petroleum feedstock, and the metals that formed the metallic layer of the multi-layer film can be removed via filtration.

For feeding to a refinery unit, the stable blend is further heated above the melting point of the plastic to produce a homogeneous liquid blend of petroleum and plastic. The hot homogeneous liquid blend is fed directly to the oil refinery process units for conversion of waste plastics to high value products with good yields.

Refinery conversion units such as a fluid catalytic cracking (FCC) unit, hydrocracking unit, and hydrotreating unit, convert the hot homogeneous liquid blend of the plastic and petroleum feedstock in the presence of catalysts with simultaneous conversion of the plastic and petroleum feedstock. The presence of catalysts in the conversion unit allows conversion of the waste plastics to higher value products at a lower operating temperature than the typical pyrolysis temperature. The yields of undesirable byproducts (offgas, tars, coke, char) are lower than the typical pyrolysis process. For the hydroprocessing units (hydrocracking and hydrotreating units), hydrogen is added to units to improve the conversion of the plastics. The blend may generate additional synergistic benefits coming from the interaction of the plastic and petroleum feedstock during the conversion process. Fluid catalytic cracking and hydrocracking processes are preferred modes of catalytic conversion of the stable blend.

In one embodiment, the stable blend of plastic and petroleum feedstock can be sent to a coker unit for thermal conversion of waste plastics. In this case, there are no substantial advantages in the reactor temperature or the product yield compared to a pyrolysis process. The advantage of the coker unit is its feed flexibility in that the unit can handle a blend with very high nitrogen, sulfur, and metals impurities.

The stable blend of plastic and petroleum feedstock allows more efficient recycling of waste plastics. The use of the present blend is far more energy efficient than the current pyrolysis process, and allows recycling with a lower carbon footprint. The improved processes would allow establishment of a circular economy on a much larger scale by efficiently converting waste plastics back to virgin quality polymers or value-added chemicals and fuels.

Proper sorting of waste plastics is very important in order to minimize contaminants such as N, Cl, and S. Plastics waste containing polyethylene terephthalate (plastics recycle classification type 1), polyvinyl chloride (plastics recycle classification type 3) and other polymers (plastics recycle classification type 7) need to be sorted out to less than 5%, preferably less than 1% and most preferably less than 0.1%. The present process can tolerate a moderate amount of polystyrene (plastics recycle classification type 6). Waste polystyrene needs to be sorted out to less than 20%, preferably less than 10% and most preferably less than 5%.depicts the plastic type classification for waste plastics recycling.

Washing of waste plastics can remove metal contaminants such as sodium, calcium, magnesium, aluminum, and non-metal contaminants coming from other waste sources. Non-metal contaminants include contaminants coming from the Periodic Table Group IV, 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. The residual metals, non-metal contaminants, and halides need to be removed to less than 50 ppm, preferentially less than 30 ppm and most preferentially to less than 5 ppm.

The petroleum with which the waste plastic is blended is generally a petroleum feedstock for the refinery. It is preferred that the petroleum blending oil is the same as the petroleum feedstock for the refinery. The petroleum can also comprise any petroleum derived oil or petroleum based material. In one embodiment, the petroleum feedstock oil can comprise atmospheric gas oil, vacuum gas oil (VGO), atmospheric residue, or heavy stocks recovered from other refinery operations. In one embodiment, the petroleum feedstock oil with which the waste plastic is blended comprises VGO. In one embodiment, the petroleum feedstock oil with which the waste plastic is blended comprises light cycle oil (LCO), heavy cycle oil (HCO), FCC naphtha, gasoline, diesel, toluene, and/or an aromatic solvent derived from petroleum.

In one embodiment, the petroleum feedstocks for the blend preparation include vacuum gas oil, atmospheric gas oil, reformate, light cycle oil, heavy fuel oil, refinery hydrocarbon streams containing toluene, xylene, heptane or benzene, or pure toluene, pure xylene, coker naphtha, C-Cisomerized paraffinic naphtha, FCC naphtha, hydrocracker bottom, gasoline, jet fuel, diesel or mixtures of some these.

The most preferred petroleum feedstocks are gas oil, heavy reformate, or various recycle streams that will be fed to a catalytic conversion unit. Then, the plastic and petroleum feedstock in the blend are converted together to a higher value product via catalytic conversion.

More than one petroleum feedstock can be used to optimize the blend properties. For example, the viscosity and pour point can be lowered by adding lighter petroleum feedstocks such as light cycle oil, gasoline, or diesel.

Optionally, solvents such as benzene, toluene, xylene or heptane may be added to the blend to reduce the viscosity or pour point of the blend of plastic and petroleum feedstock for easier handling.

In one embodiment, the feedstock with which the blend is prepared can comprise a bio-feed. The bio-fed can comprise the entire feedstock, or can be mixed with the petroleum feedstock.

In one embodiment, the petroleum feedstock is chosen for preferred dissolution of polyethylene and polypropylene. The petroleum feedstock exhibits high solubility of polyethylene and polypropylene plastics and exhibits low solubility of undesirable plastics, such as polyvinyl chloride, polystyrene, and other Group 7 plastics, as well as metal barrier films and inorganic impurities. These undesirable materials from waste plastic sources are removed by a filtration step. Examples of such suitable feedstocks include vacuum gas oil (VGO), light cycle gas oil (LCO), and diesel.

The term “bio” refers to biochemical and/or natural chemicals found in nature. Thus, a bio feedstock or bio oil would comprise such natural chemicals. The preferred starting bio feedstocks for the blend preparation include triglycerides and fatty acids, plant-derived oils such as palm oil, canola oil, corn oil, and soybean oil, as well as animal-derived fats and oils such as tallow, lard, schmaltz (e.g., chicken fat), and fish oil, and mixtures of these.

The present process with its two or three steps to prepare the present blend ensures that the amount of chloride remaining in the blend is so small that no damage will be inflicted on the refinery units and equipment. The presence of chloride can create HCl acid which will cause deterioration of the units. This is of major importance since the refinery also has a purpose of preparing chemicals, base oils and fuel oils, and the units and equipment in the refinery are chloride sensitive as noted. Further, the chloride can also impact the catalyst used in a refinery and the product quality. By using the present blend, prepared by the present process, one can efficiently, effectively, and safely recycle waste plastic while also complimenting the operation of a refinery in the preparation of higher value products such as gasoline, jet fuel, base oil, diesel fuel, and useful chemicals.

While not wanting to be bound by a theory, the present process prepares a stable blend comprising minimal, if any, chloride, metals and other plastic contaminants, that is an intimate physical mixture of plastic and petroleum feedstock for catalytic conversion in refinery units. The present process produces a stable blend of petroleum feedstock and plastic, wherein the plastic is in a “de-agglomerated” state. The plastic maintains its state as “finely dispersed” solid particles in the petroleum feedstock at ambient temperature. This blend is stable and allows easy storage and transportation. At a refinery, the stable blend can be preheated above the melting point of the plastic to produce a hot, homogeneous liquid blend of plastic and petroleum, and then the hot liquid blend is fed to a conversion unit. Then both the petroleum feed and plastic are simultaneously converted in the conversion unit with typical refinery catalysts containing zeolite(s) and other active components such as silica-alumina, alumina and clay.

Use of the present blend avoids the pyrolysis of waste plastic. Rather, a stable blend of petroleum feedstock and the waste plastic as prepared can be fed to the refinery units. Thus, the pyrolysis step can be avoided, which is a significant energy savings.

The stable blend is made by a two or three-step process. The first step produces a hot, homogenous liquid blend of plastic melt and petroleum feedstock. The preferred range of the plastic in the blend is about 1-20 wt %. The blend of feedstock and plastic is heated to a temperature sufficient to decompose residual PVC. The temperature can be about 500° F. or higher, although a temperature of about 550°-700° F. is generally found acceptable. The duration of the heating is sufficient to achieve decomposition of most, if not all of the remaining PVC. Any offgas from the heating, which would contain chloride, is treated with a scrubber.

The second step involves hot filtering the blend mixture to remove any contaminants. By hot filtering is meant the homogenous blend from the previous step is filtered while still hot. The contaminants can include glass, metal, PVC or other plastics with a low solubility such as PS and PET. This filtration step allows most of the PVC to be removed.

The last step is optionally treating liquid product recovered from the second step with a chloride removal guard bed catalyst. Such catalyst beds are known in the industry to be effective in reducing chlorides to low ppm levels. In one embodiment, the catalyst beds are based on oxides such as CaO and MgO or hydroxides such as Fe(OH). The resulting blend can now be fed to a refinery directly or cooled and stored for subsequent use. The subsequent use can comprise being fed to a refinery or transported and fed to a refinery.

In cooling and storing the blend, the hot homogeneous liquid blend is cooled to ambient temperature in a controlled manner to allow for easy storage and transportation. By using this method, a stable blend can be prepared at a facility away from a refinery and can be transported to a refinery unit. Then the stable blend is heated above the melting point of the plastic to feed to the refinery conversion unit. The stable blend is a physical mixture of micron-size plastic particles finely suspended in the petroleum-based oil, with the average particle size of the plastic particles of 10 micron to less than 100 microns. The mixture is stable, and the plastic particles do not settle or agglomerate upon storage for an extended period.

What is meant by heating the blend to a temperature above the melting point of the plastic is clear when a single plastic is used. However, if the waste plastic comprises more than one waste plastic, then the melting point of the plastic with the highest melting point is exceeded. Thus, the melting points of all plastics must be exceeded. Similarly, if the blend is cooled below the melting point of the plastic, the temperature must be cooled below the melting points of all plastics comprising the blend.

Compared with a pyrolysis unit, these blend preparation units operate at a lower temperature (˜500°-600° C. vs. 288°-371° C.). Thus, employing the present blend in conjunction with a refinery can provide a far more energy efficient process than a thermal cracking process such as pyrolysis.