Co-Processing Plastic Waste in Cokers for Jet Fuel Production

This application claims the benefit of and priority to U.S. Provisional Application No. 63/338,062 filed May 4, 2022, the disclosure of which is incorporated herein by reference.

Systems and methods are provided for production of jet fuel from feeds derived at least in part from co-processing of plastic waste in a coking environment.

There is increasing interest in finding ways to recycle plastic waste so that the carbon from the underlying polymers can be recovered and incorporated into another cycle of products. This can include incorporation of plastic waste as part of the input flows for production of additional polymers, production of other products from chemical plants, and or for production of refinery products (such as fuels and/or lubricants).

One of the difficulties with incorporation of plastic waste as part of the input flows for a refinery is that plastic waste tends to correspond to a mixture of different types of plastic waste. Plastic waste can commonly include a variety of types of polymers, including polyolefins (e.g., low density polyethylene, high density polyethylene, polypropylene), polystyrene, nitrogen-containing polymers (such as nylon 6 and/or other polyamides), polyesters, polyethylene terephthalate, other oxygen-containing polymers, and chlorine-containing polymers (e.g., polyvinyl chloride (PVC) or polyvinylidene chloride (PVDC)).

Another difficulty with incorporation of plastic waste into refinery processes is that refineries typically make an integrated slate of products. Introduction of plastic waste into one refinery process can often result in production of molecules that are incorporated across a variety of the products generated at the refinery. For example, the outputs from a delayed coker and/or fluidized coker can potentially be distributed across naphtha, kerosene (jet), diesel, lubricant, and/or fuel oil products in an integrated refinery setting. Thus, in order to introduce plastic waste into such a refinery, either a) the process train where the plastic waste is introduced needs to be isolated, or the feed and/or refinery processes need to be adapted so that the introduction of the plastic waste is compatible with all of the products that are generated as part of the refinery product slate. Having to isolate a portion of a refinery can incur substantial capital costs as well as potentially disrupting production of the full product slate at a refinery. Therefore, it would be desirable to identify systems and methods that can enable use of plastic waste as part of refinery input streams during integrated refinery processing.

International Publication WO2021/091724 describes co-processing of plastic waste in a fluidized coking environment or a delayed coking environment.

U.S. Patent Application Publication 2021/0087473 describes using delayed coking for co-processing of plastic waste with heavy oils. The plastic waste can include plastics that have been additized with metals. The additized metals can be concentrated in the coke produced during the delayed coking.

International Publication WO1995/014069 describes dissolution of waste plastic in an aromatic solvent prior to combining the dissolved plastic with a feed for a delayed coking process.

U.S. Pat. No. 4,851,601 describes co-processing of plastic waste in a delayed coker followed by exposing the coker products to a second cracking stage where the coker products are exposed to zeolitic catalysts at elevated temperature.

Chinese Patent CN101230284 describes methods for coking of plastic waste. The plastic waste is pulverized to form small particles. The resulting particles are fluidized using a screw extrusion conveyor, followed by heating and extrusion to convert the plastic waste into a semi-fluid state. The heated and extruded plastic waste is then stored at a temperature of 290° C. to 320° C. to maintain the plastic in a liquid state. The liquid plastic waste is then pumped into the coker furnace, optionally along with a co-feed.

U.S. Pat. No. 9,920,255 describes methods for depolymerization of plastic material. The methods include melting and degassing a plastic feed to form molten plastic. A liquid crude fraction is then added to the molten plastic to reduce the viscosity prior to introducing the mixture of molten plastic and liquid crude into the pyrolysis reactor. It is noted that the plastic is melted and degassed prior to combining the plastic with any conventional co-feed, thus increasing the number of separate reactor vessels needed for integrating the plastic waste with a conventional co-feed.

U.S. Pat. No. 6,861,568 describes a method for performing radical-initiated pyrolysis on plastic waste dissolved in an oil medium. After mixing the plastic waste with oil, the mixture is delivered to a pyrolysis vessel. The pyrolysis temperature is generally described as 300° C.-375° C., although an example is provided of partial reaction at 275° C. Based on the pyrolysis conditions, one of the two primary products is a reactor overhead stream that includes a desired distillate product and a non-condensible overhead gas product. After condensing out the desired distillate product, the remaining overhead gas product can be treated with a water wash in an effort to remove any HCl that may be present. Thus, HCl removal is accomplished using a separate, additional water wash stage.

In an aspect, a method for co-processing a plastic feedstock is provided. The method includes mixing a plastic feedstock with one or more additional feedstocks to form a feedstock mixture. The plastic feedstock can contain 25 wt % or less of at least one nitrogen-containing polymer relative to a weight of the plastic feedstock. The feedstock mixture can contain 0.5 wt % to 30 wt % of the plastic feedstock relative to a weight of the feedstock mixture. The method further includes exposing at least a portion of the feedstock mixture to coking conditions to form a conversion effluent comprising one or more amides, one or more amines, or a combination thereof. The method further includes separating the conversion effluent to form at least one liquid product fraction having a T10 distillation point of 300° C. or less and a T90 distillation point of 170° C. or more. The at least one liquid product fraction can have a basic nitrogen content of 100 wppm or more relative to a weight of the at least one liquid product fraction. Additionally, the method includes exposing at least a portion of the at least one liquid product fraction to hydroprocessing conditions to form a hydroprocessed effluent that contains a jet boiling range fraction having a total nitrogen content of 10 wppm or less relative to a weight of the jet boiling range fraction.

Optionally, the basic nitrogen content of the at least one liquid product fraction can correspond to 20 wt % or more of the total nitrogen content of the at least one liquid product fraction, or 40 wt % or more. Optionally, the at least one liquid product fraction can have a basic nitrogen content of 150 wppm or more, or 300 wppm or more, prior to the hydroprocessing.

All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

In various aspects, systems and methods are provided for co-processing plastic waste in a coker as part of an integrated refinery environment that produces kerosene, jet fuel, and/or jet fuel blending components as a product. The co-processing can be performed in a fluidized coker, a delayed coker, or a combination of fluidized cokers and delayed cokers. After coking, hydroprocessing can be performed on one or more portions of the coker effluent that contribute to formation of the kerosene, jet fuel, and/or jet fuel blending component product(s). The hydroprocessing can be used, for example, to reduce or minimize the presence of unexpected nitrogen contaminants in the resulting kerosene, jet fuel, and/orjet fuel blending component product(s).

Plastic waste generally corresponds to a mixture of multiple types of polymers. Some types of polymers, such as polyethylene, polypropylene, or polystyrene, correspond to hydrocarbons. As a result, to the degree that coking of such polymers forms liquid phase products, such liquid phase products also typically correspond to hydrocarbons.

Other types of polymers can include heteroatoms different from carbon and hydrogen as part of the monomers used for forming the polymer. As an example, polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC) include one or more chlorines per repeat unit in the polymer. Such chlorine-containing polymers can potentially evolve chlorine compounds that may contaminate the eventual products and/or that can cause damage to the processing environment.

Another group of polymers corresponds to nitrogen-containing polymers, such as polyamides. Nylon 6 is an example of a commonly encountered polyamide. In a coking environment, polyamides (and/or other nitrogen-containing polymers) can form nitrogen-containing products with boiling points in the kerosene/jet boiling range. For example, introducing a plastic feedstock including Nylon 6 into a coking environment can result in formation of caprolactam, which is a kerosene/jet boiling range amide. This can pose several difficulties. First, the presence of substantial amounts of amides in a kerosone/jet boiling range fraction is unexpected relative to the types of compounds present in kerosene/jet fuel/jet fuel blending component fractions derived from mineral feeds. Second, because decomposition of polyamides in a coking environment results in direct formation of kerosene/jet boiling range compounds that contain nitrogen (such as caprolactam), co-processing of a plastic feedstock in a coking environment can result in unexpectedly high total nitrogen contents in the kerosene/jet boiling range fraction, relative to the total nitrogen content of the mineral portion of the feed and/or relative to the nitrogen content of other fractions derived from the co-processing.

In various aspects, systems and methods are provided for co-processing plastic waste in a coking environment while reducing, minimizing, or otherwise mitigating the impact of contaminants on the resulting kerosene/jet fuel boiling fraction generated from the coking process. First, the type of plastic waste used for co-processing can be controlled in order to avoid excessive quantities of chlorine and/or nitrogen compounds in the coker effluent and/or in the kerosene/jet boiling range portions of the coker effluent. This can include limiting the amount of nitrogen-containing polymers and/or chlorine-containing polymers that are present in the plastic waste.

Optionally, a thermal dehalogenation stage can be used to reduce or minimize the chlorine content of the plastic feedstock prior to exposing the plastic feedstock to the coking environment. After mixing the plastic feedstock with one or more additional feedstocks to form a combined feed that corresponds to a solution or slurry, the combined feed can exposed to a temperature of 150° C. to 300° C. in the presence of purge gas to remove chlorine from the combined feed.

In addition to selecting plastic waste with an appropriate composition for use as a co-feed, hydroprocessing can be used to reduce or minimize the nitrogen content (such as the amide content) of any kerosene/jet boiling range fractions that are formed from the coker effluent. Due to increased selectivity for formation of nitrogen compounds in the kerosene/jet boiling range, the presence of nitrogen-containing polymers in the combined feed can lead to unexpectedly high nitrogen contents in the kerosene/jet boiling range fraction. Additionally, other nitrogen-containing compounds may be present in other (higher boiling) portions of the coker effluent. Such compounds in other portions of the coker effluent can also be exposed to hydroprocessing conditions. To the degree that feed conversion occurs during hydroprocessing that results in additional formation of kerosene/jet boiling range components, such additional kerosene/jet boiling range components can be added to the total kerosene/jet boiling range product.

Coking can provide a flexible reaction system for co-processing of plastic waste. Even though the type of polymers in plastic waste can vary widely, coking can be performed to generate a liquid product slate. In aspects where Flexicoking™ is used for coking, synthesis gas can also be generated while reducing or minimizing net coke yield when co-processing a conventional coker feed with plastic waste.

The co-processing of plastic waste in a coking environment (or other thermal conversion environment) can be performed by performing four types of processes on the plastic waste. First, the plastic waste can be conditioned by classifying and sizing of the plastic waste to improve the suitability of the plastic waste for co-processing. Second, the conditioned plastic waste particles can be entrained and/or dissolved into a solvent and/or the base feed. In aspects where a solvent is used, the solvent can preferably correspond to a refinery stream, such as a refinery stream formed by the co-processing of the plastic waste in the coking environment. Optionally, in aspects where the plastic waste feed is mixed with a solvent and/or base feed, a stripping gas can be added to remove HCl or other gases that may evolve as the plastic waste is heated. Third, the solution and/or slurry of plastic waste can be passed into a coking environment, such as a fluidized coking environment or a delayed coking environment. The solution and/or slurry of plastic waste can be introduced as a separate stream, or the solution and/or slurry can be mixed with a conventional coker feedstock prior to entering the coking environment. Fourth, the plastic waste can then be co-processed in the coking environment to generate liquid products.

In some aspects, co-processing of plastic waste in a coking environment can provide advantages relative to coking of a conventional feed. Conventional coker feeds are often selected for coking based on having a relatively low molar ratio of hydrogen atoms to carbon atoms in the feed. In comparison with such a conventional coker feed, many types of plastic waste include a higher molar ratio of hydrogen atoms to carbon atoms. This additional hydrogen content in plastic waste can reduce the amount of coke that is formed in favor of increased production of liquid products.

In some aspects, a plastic waste feedstock can be co-processed with a coker feedstock in a fluidized coking environment, such as a Flexicoking™ coking environment. By sufficiently reducing or minimizing the particle size of the particles in a plastic waste feedstock, the plastic waste can be unexpectedly incorporated into a fluidized coking environment. Further additional benefits can be realized in a Flexicoking environment, where plastic waste can be co-processed while increasing the amount of production of synthesis gas.

In this discussion, a reference to a “C” fraction, stream, portion, feed, or other quantity is defined as a fraction (or other quantity) where 50 wt % or more of the fraction corresponds to hydrocarbons having “x” number of carbons. When a range is specified, such as “C-C”, 50 wt % or more of the fraction corresponds to hydrocarbons having a number of carbons between “x” and “y”. A specification of “C” (or “C”) corresponds to a fraction where 50 wt % or more of the fraction corresponds to hydrocarbons having the specified number of carbons or more (or the specified number of carbons or less).

In this discussion, the naphtha boiling range is defined as roughly the boiling point of a Calkane (roughly 30° C.) to 177° C. A naphtha boiling range fraction is defined as a fraction having a T10 distillation point of 30° C. or higher and a T90 distillation point of 177° C. or less. A heavy naphtha boiling range fraction is defined as a fraction having a T10 distillation point of 30° C. or higher and a T90 distillation point of 204° C. or less. The kerosene or jet boiling range is defined as 125° C. to 300° C. A kerosene or jet boiling range fraction is defined as a fraction having a T10 distillation point of 129° C. or more and a T90 distillation point of 300° C. or less. The distillate boiling range is defined as 177° C. to 343° C. A distillate boiling range fraction is defined as a fraction having a T10 distillation point of 177° C. or higher and a T90 distillation point of 343° C. or less. The gas oil boiling range is defined as 343° C. to 566° C. A distillate boiling range fraction is defined as a fraction having a T10 distillation point of 343° C. or higher and a T90 distillation point of 566° C. or less. The vacuum resid boiling range corresponds to temperatures greater than 566° C. In this discussion, distillation points can be determined according to ASTM D86. In the event that ASTM D86 is unsuitable for characterization of a sample, ASTM 2887 may be used instead.

In some aspects, a fraction can be referred to as a jet/kerosene containing fraction. This can correspond to an input flow, an intermediate effluent or fraction, or an end product that includes a portion corresponding to the jet/kerosene boiling range. In this discussion, one way of identifying such a fraction can be based on the fraction having both a T90 distillation point of 129° C. or more and a T10 distillation point of 300° C. or less. In other words, the fraction can be “heavy” enough that at least a portion of the fraction boils above the naphtha range (T90 is greater than 129° C.), and the fraction can be “light” enough that at least a portion of the fraction boils below the distillate range (T10 is less than 300° C.). As an example, a light naphtha fraction can have a T10 of 30° C. or more and a T90 of 120° C. or less. Such a naphtha fraction would satisfy the requirement of having a T10 of less than 300° C., but would not satisfy the requirement of having a T90 of 129° C. or more. As another example, a fraction containing both kerosene and distillate could have a T10 of 200° C. and a T90 of 343° C. Such a fraction satisfies the definition of including jet or kerosene, as the T10 is less than 300° C., and the T90 is greater than 129° C.

In this discussion, a liquid product/liquid portion is defined as a product/portion that is in the liquid state at 25° C. and 100 kPa-a. A gas or vapor product/gas or vapor portion is defined as a product/portion that is in the gas phase at 25° C. and 100 kPa-a. It is noted that at some points during processing, a liquid product/portion may be present in a gaseous phase due to an increased temperature (and/or the combination of temperature and pressure) within the reaction system. Similarly, depending on the nature of the full configuration used, a vapor product/portion may be in a liquid phase due to the combination of temperature and pressure at a location within the reaction system.

In this discussion, total nitrogen in a sample can be measured according to ASTM D4629. In this discussion, the basic nitrogen content of a feed, fraction, or product can be determined according to the following method by performing measurements on two samples of the feed, fraction, or product. First, the total nitrogen of a sample is characterized according to ASTM D4629. Next, a sample can be acid washed by adding 1 ml of 1 N sulfuric acid to a 10 ml sample. This mixture can be formed in a suitable vessel, such as a 20 ml vial. The mixture of the sample and the sulfur acid is shaken vigorously, and then allowed to settle for 5 minutes. After settling, the sulfuric acid should be at the bottom of the vessel. The acid washed sample is removed from the top of the vessel, such as by using a pipette to remove the acid washed sample while not including any of the sulfuric acid. The acid washed sample can then be characterized according to ASTM D4629. The difference in nitrogen content between the untreated sample and the acid washed sample corresponds to the nitrogen that is removed by acid treatment. In this discussion, the nitrogen removed by acid treatment is defined as the basic nitrogen content. Amides and amines present in a sample correspond to basic nitrogen, so the presence of excess amides and amines in a sample due to decomposition of nitrogen-containing polymers will result in a corresponding increase in the basic nitrogen content of a sample.

In some aspects, a plastic feedstock for co-processing can include or consist essentially of one or more types of polymers, such as polymers corresponding to plastic waste. The systems and methods described herein can be suitable for processing plastic waste corresponding to a single type of olefinic polymer and/or plastic waste corresponding to a plurality of olefinic polymers. In aspects where the plastic feedstock consists essentially of polymers, the feedstock can include one or more types of polymers as well as any additives, modifiers, packaging dyes, and/or other components typically added to a polymer during and/or after formulation. The feedstock can further include any components typically found in polymer waste.

In various aspects, the plastic feedstock can include one or more nitrogen-containing polymers. Examples of nitrogen-containing polymers include polyamides (such as Nylon 6), polyurethanes, and polynitriles. The nitrogen-containing polymers can correspond to 0.1 wt % to 25 wt % of the plastic feedstock (relative to the weight of the plastic feedstock), or 1.0 wt % to 25 wt %, or 5.0 wt % to 25 wt %, or 10 wt % to 25 wt %, or 1.0 wt % to 15 wt %, or 5.0 wt % to 15 wt %, or 1.0 wt % to 10 wt %.

In some aspects, the plastic feedstock can include one or more chlorine-containing polymers. Examples of chlorine-containing polymers including PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride). In some aspects, the chlorine-containing polymers can correspond to as 0.001 wt % to 15 wt % of the plastic feedstock (relative to the weight of the plastic feedstock), or 0.1 wt % to 15 wt %, or 1.0 wt % to 15 wt %, or 0.001 wt % to 10 wt %, or 0.1 wt % to 10 wt %, or 1.0 wt % to 10 wt %, or 0.001 wt % to 5.0 wt %, or 0.001 wt % to 1.0 wt %.

In some aspects, the polymer feedstock can include at least one of polyethylene and polypropylene. The polyethylene can correspond to any convenient type of polyethylene, such as high density or low density versions of polyethylene. Similarly, any convenient type of polypropylene can be used. Additionally or alternately, the plastic feedstock can include one or more of polystyrene, polyamide (e.g., nylon), polyethylene terephthalate, and ethylene vinyl acetate. Still other polyolefins can correspond to polymers (including co-polymers) of butadiene, isoprene, and isobutylene. In some aspects, the polyethylene and polypropylene can be present in the mixture as a co-polymer of ethylene and propylene. More generally, the polyolefins can include co-polymers of various olefins, such as ethylene, propylene, butenes, hexenes, and/or any other olefins suitable for polymerization.

In this discussion, unless otherwise specified, weights of polymers in a feedstock correspond to weights relative to the total polymer content in the feedstock. Any additives and/or modifiers and/or other components included in a formulated polymer are included in this weight. However, the weight percentages described herein exclude any solvents or carriers that might optionally be used to facilitate transport of the polymer into the initial pyrolysis stage.

In some aspects, the plastic feedstock can include 0.01 wt % to 35 wt % of polystyrene, or 0.1 wt % to 35 wt %, or 1.0 wt % to 35 wt %, or 0.01 wt % to 20 wt %, or 0.1 wt % to 20 wt %, or 1.0 wt % to 20 wt %, or 10 wt % to 35 wt %, or 5 wt % to 20 wt %. In some aspects, the plastic feedstock can also include oxygen-containing polymers, such as polyterephthalates. It is noted that polyamides also contain oxygen as part of the polymer structure. In this discussion, a polymer that includes both oxygen and nitrogen as part of the repeat unit for forming the polymer is defined as a nitrogen-containing polymer for purposes of characterizing the plastic feedstock.

A plastic feedstock can be combined with one or more additional feedstocks to form a combined feed for co-processing in a coking environment. In various aspects, the plastic feedstock can correspond to 0.1 wt % to 30 wt % of the combined feed for coking (relative to a weight of the combined feed), or 0.1 wt % to 20 wt %, or 0.1 wt % to 10 wt %, or 0.1 wt % to 5.0 wt %, or 1.0 wt % to 30 wt %, or 1.0 wt % to 20 wt %, or 1.0 wt % to 10 wt %, or 1.0 wt % to 5.0 wt %, or 5.0 wt % to 30 wt %, or 5.0 wt % to 20 wt %. In some aspects, 50 wt % or more of the combined feed can correspond to feedstock with a boiling point of 343° C. or higher.

It is noted that some types of plastic waste can also include bio-derived components. For example, some types of plastic labels can include biogenic waste in the form of paper compounds. In some aspects, 1.0 wt % to 25 wt % of the plastic feedstock can correspond to bio-derived material. Such bio-derived material can also potentially contribute to the nitrogen content of a plastic feedstock.

In some aspects, the coker feedstock for co-processing with the plastic waste feedstock can correspond to a relatively high boiling fraction, such as a heavy oil feed. For example, the coker feedstock portion of the feed can have a T10 distillation point of 343° C. or more, or 371° C. or more. Examples of suitable heavy oils for inclusion in the coker feedstock include, but are not limited to, reduced petroleum crude; petroleum atmospheric distillation bottoms; petroleum vacuum distillation bottoms, or residuum; pitch; asphalt; bitumen; other heavy hydrocarbon residues; tar sand oil; shale oil; or even a coal slurry or coal liquefaction product such as coal liquefaction bottoms. Such feeds will typically have a Conradson Carbon Residue (ASTM D189-165) of at least 5 wt %, generally from 5 to 50 wt %. In some preferred aspects, the feed is a petroleum vacuum residuum.

Some examples of conventional petroleum charge stock suitable for processing in a delayed coker or fluidized bed coker can have a composition and properties within the ranges set forth below in Table 1.

In addition to petroleum charge stocks, renewable feedstocks derived from biomass having a suitable boiling range can also be used as part of the coker feed. Such renewable feedstocks include feedstocks with a T10 boiling point of 340° C. or more and a T90 boiling point of 600° C. or less. An example of a suitable renewable feedstock derived from biomass can be a pyrolysis oil feedstock derived at least in part from biomass.

In various aspects, the plastic waste can be prepared for introduction as a plastic feedstock for co-processing by using one or more physical processes to convert the plastic feedstock into particles and/or to reduce the particle size of the plastic particles.

For a plastic feedstock that is not initially in the form of particles, a first processing step can be a step to convert the plastic feedstock into particles and/or to reduce the particle size. This can be accomplished using any convenient type of physical processing, such as chopping, crushing, grinding, shredding or another type of physical conversion of plastic solids into particles. It is noted that it may be desirable to convert plastic into particles of a first average and/or median size, followed by additional physical processing to reduce the size of the particles.

Having a small particle size can facilitate solvation of the plastic particles in the one or more additional feedstocks and/or distribution of plastic particles within a slurry of the one or more additional feedstocks in a desirable time frame. Thus, physical processing can optionally be performed to reduce the median particle size of the plastic particles to 10 cm or less, or 3.0 cm or less, or 2.5 cm or less, or 2.0 cm or less, or 1.0 cm or less, such as down to 0.01 cm or possibly still smaller. For determining a median particle size, the particle size is defined as the diameter of the smallest bounding sphere that contains the particle.

Optionally, an additional solvent can be added to the plastic particles and/or the combined feed to further facilitate dissolution of the plastic particles. Aromatic solvents are examples of potential additional solvents.

As noted above, a plastic feedstock can include 0.1 wt % to 25 wt % of nitrogen-containing polymers, relative to a weight of the plastic feedstock. For a typical nitrogen-containing polymer, such as a nylon or another type of polyamide, nitrogen atoms correspond to 5.0 wt % to 20 wt % of the weight of the nitrogen-containing polymer. Thus, the initial nitrogen content of the plastic feedstock can potentially range from 50 wppm to 50,000 wppm (5.0 wt %).

After exposure to a coking environment, it is believed that the nitrogen content from the plastic feedstock is not evenly distributed across the boiling range of the coker effluent. Instead, the jet/kerosene boiling range components of the coker effluent can have an unexpectedly high share of the nitrogen derived from the plastic feedstock. This can occur based on several mechanisms during coking.

First, for polymers such as Nylon 6, caprolactam is a common decomposition product during pyrolysis. When exposing Nylon 6 to coking conditions, roughly 5.0 wt % to 10 wt % of the coking products derived from Nylon 6 can correspond to caprolactam. Because caprolactam is a jet boiling range compound, the production of caprolactam results in a concentration of nitrogen from the plastic feedstock in the jet boiling range portion of the coker effluent. More generally, to the degree that larger chain fragments are formed during coking of a polyamide, such larger chain fragments will also correspond to amides.