Process and apparatus for chemically treating a carbon-containing feedstock

Abstract

This disclosure relates to a process for chemically treating a carbon-containing feedstock (e.g., a polymer-based feedstock) comprising contacting (e.g., by a hydrocracking reaction) the carbon-containing feedstock and a hydrogen stream in the presence of a hydrocracking catalyst, at an elevated temperature, to produce an alkane-containing product stream. The catalyst comprises at least one transition metal or transition metal oxide and does not contain an acid site. This disclosure also relates to an alkane-containing mixture obtained by the process described herein and a system / apparatus for carrying out the processes described herein.

Description

PRIORITY CLAIM

[0001] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 63 / 750,834, filed Jan. 29, 2025, herein incorporated by reference in its entirety.FIELD OF INVENTION

[0002] This disclosure generally relates to processes and systems for chemically treating carbon-containing feedstocks.BACKGROUND OF THE INVENTION

[0003] Plastic waste has become a significant environmental concern worldwide, with millions of tons of plastic ending up in landfills or polluting natural ecosystems each year. Plastic waste is a diverse feedstock which may contain several different types of polymers, fillers, stabilizing agents, and / or contaminants. The inconsistent quality of the feedstock provides a technical challenge in the conversion of plastics to chemicals.

[0004] Chemical recycling has emerged as a promising approach for converting plastic waste into valuable chemicals. This process involves breaking down polymer chains into smaller molecules that can be used as raw materials for new products. Conventional catalytic processes for plastic conversion typically employ bifunctional catalysts containing both acid sites for cracking the plastic and metal sites for hydrogenating the cracked unsaturated products. While these catalysts can be effective under certain conditions, they may suffer from deactivation due to contaminants (e.g., various additives, fillers, and impurities) present in waste plastics. In particular, contaminants can negatively affect the catalyst's cracking functionality. During chemical recycling process, these contaminants can poison the active sites of the catalysts and reduce overall process efficiency, posing a challenge in catalytic chemical recycling of waste plastics.

[0005] As a result, current plastic recycling technologies often require extensive feedstock pre-treatment purification to remove or minimize contaminants contained in the waste plastics that can deactivate the catalyst, which increases process complexity and cost.

[0006] There thus remains a need in the art for developing a simplified, one-step conversion method and system to more efficiently crack the polymer feedstock, while increasing the yield and quality of the recovered liquid hydrocarbon product suitable for direct use or further processing in existing petrochemical infrastructure.SUMMARY OF THE INVENTION

[0007] According to an aspect of the disclosure, a process for chemically treating a carbon-containing feedstock is provided. The process comprises contacting the carbon-containing feedstock and a hydrogen stream in the presence of a hydrocracking catalyst, at an elevated temperature, to produce an alkane-containing product stream. The hydrocracking catalyst comprises at least one transition metal or transition metal oxide, and the hydrocracking catalyst does not contain an acid site.

[0008] According to another aspect of the disclosure, a process for depolymerizing a polymer-based feedstock is provided. The process comprises reacting a polymer-based feedstock with a hydrogen stream in the presence of a hydrocracking catalyst, at an elevated temperature, in a one-step, hydrocracking reaction, to depolymerize the polymer-based feedstock and form an alkane-containing product stream. The hydrocracking catalyst comprises at least one transition metal or transition metal oxide, and the hydrocracking catalyst does not contain an acid site.

[0009] Another aspect of the disclosure relates to an alkane-containing mixture obtained by the process described herein, according to the aspects of this disclosure.

[0010] Another aspect of the disclosure relates to a system / apparatus for chemically treating a carbon-containing feedstock (e.g., depolymerizing a polymer-based feedstock). The system comprises a reactor receiving the carbon-containing feedstock, a hydrogen stream, and at least one hydrocracking catalyst. The reactor is configured to provide an elevated temperature and to convert the carbon-containing feedstock into an alkane-containing product stream (e.g., to contact the carbon-containing feedstock and the hydrogen stream in the presence of the hydrocracking catalyst to produce an alkane-containing product stream, or to react the polymer-based feedstock with the hydrogen stream in the presence of the hydrocracking catalyst in a one-step, hydrocracking reaction, to depolymerize the polymer-based feedstock and form an alkane-containing product stream). The hydrocracking catalyst comprises at least one transition metal or transition metal oxide, and the hydrocracking catalyst does not contain an acid site.

[0011] According to yet another aspect of the disclosure, a method for selectively converting a polymer-based feedstock to a liquid naphtha or naphtha-like product is provided. The method comprises reacting a polymer-based feedstock with a hydrogen stream in the presence of a hydrocracking catalyst, at an elevated temperature, in a one-step, hydrocracking reaction, to depolymerize the polymer-based feedstock and form a liquid naphtha or naphtha-like product containing at least 50% (such as at least 55%) by weight of C4-C12 hydrocarbons based on the total weight of the product. The hydrocracking catalyst comprises at least one transition metal or transition metal oxide, which is optionally hydrotreated prior to the reacting step. The hydrocracking catalyst does not contain an acid site, and the reaction temperature ranges from about 400 to about 550° C. (such as from about 400 to about 500° C., or from about 430 to about 450° C.).

[0012] According to yet another aspect of the disclosure, a use of a catalyst comprising at least one transition metal or transition metal oxide for converting a carbon-containing feedstock into an alkane-containing product stream is provided.

[0013] Additional aspects, advantages and features of the disclosure are set forth in this specification, and in part will become apparent to those skilled in the art on examination of the following or may be learned by practice of the invention. The inventions disclosed in this application are not limited to any particular set of or combination of aspects, advantages, and features. It is contemplated that various combinations of the stated aspects, advantages and features make up the inventions disclosed in this application.BRIEF DESCRIPTION OF DRAWINGS

[0014] FIGS. 1A-1B show the possible contaminants contained in a polyethylene post-consumer recycled (PE-PCR) material. FIG. 1A presents a graph showing an X-ray fluorescence (XRF) elemental analysis on a PE-PCR material. FIG. 1A also lists possible origins of contaminants for each of the elements identified in the graph. FIG. 1B is a high-performance liquid chromatography (HPLC) chromatogram showing a chemical analysis on a PE-PCR material. A few peaks identified in FIG. 1B include Erucamide, which is used to lower the coefficient of friction, and AO-1010 and AO-168 both of which are antioxidants.

[0015] FIGS. 2A-2B show the results of an hydrocracking reaction conducted on a series of the polymer samples prepared by mixing a virgin HDPE with increasing percentages of PCR content ranging from virgin HDPE to 100% PCR material (virgin HDPE, HDPE+1% PCR, HDPE+5% PCR, HDPE+10% PCR, HDPE+20% PCR, HDPE+50% PCR, 100% PCR) to mimic various contaminants removed from a PCR material, using a bifunctional catalyst (NiMo / HUSY). FIG. 2A shows the relationship between the PCR weight percentage and the contaminant concentrations for various elements, characterized by the XRF) elemental analysis on the series of the polymer samples. FIG. 2B shows the relationship between the PCR content and the product composition. The x-axis represents PCR percentage from 0 to 100, while the y-axis shows product composition percentage from 0 to 100. Four product components are plotted: Gas (C1-C3), Naphtha (C4-C12), Kerosene (C13-C20), and Solids (C20+).

[0016] FIG. 3 is a bar graph comparing the yields of various components contained in the product resulted from the hydrocracking reaction of HDPE feedstock under three different catalyst conditions described in Example 2:2A (calcined Fe2O3, reduced Fe2O3), and 2C (without Fe2O3). For each of the three catalyst conditions, the graph displays four product components: gas (C1-C3), naphtha (C4-C12), kerosene (C13-C20), and solids (C20+). The y-axis on the left shows product composition percentage from 0 to 100%, while the y-axis on the right shows mass balance percentage. Error bars are included for some data points.

[0017] FIGS. 4A-4B are pie charts comparing the compositions of the product resulted from the hydrocracking reaction of HDPE feedstock under two different catalyst conditions described in Example 2:2A (reduced Fe2O3) and 2C (without Fe2O3). FIG. 4A compares the compositions (proportions of saturated, unsaturated, aromatic, and other products) in the liquid stream (C4-C12) of the products resulted from the reactions using the reduced Fe2O3 catalyst versus without using a Fe2O3 catalyst. FIG. 4B compares the compositions (proportions of saturated and unsaturated products) in the gas stream (C1-C3) of the products resulted from the reactions using reduced Fe2O3 catalyst versus without using a Fe2O3 catalyst.

[0018] FIG. 5 is a bar graph comparing the yields of various components contained in the products resulted from the hydrocracking reaction of HDPE feedstock using a reduced Fe2O3 catalyst under two different reaction conditions described in Example 2:2A (under H2) and 2B (under He). For each of the two conditions, the graph displays four product components: gas (C1-C3), naphtha (C4-C12), kerosene (C13-C20), and solids (C20+). The y-axis on the left shows product composition percentage from 0 to 100%, while the y-axis on the right shows mass balance percentage.

[0019] FIGS. 6A-6B are pie charts comparing the compositions of the products resulted from the hydrocracking reaction of HDPE feedstock under two different reaction conditions described in Example 2:2A (under H2) and 2B (under He). FIG. 6A compares the compositions (proportions of saturated, unsaturated, aromatic, and other products) in the liquid stream (C4-C12) of the products resulted from the reactions using the reduced Fe2O3 catalyst as described herein under H2 versus under He. FIG. 6B compares the compositions (proportions of saturated and unsaturated products) in the gas stream (C1-C3) of the products resulted from the reactions using the reduced Fe2O3 catalyst as described herein under H2 versus under He.

[0020] FIG. 7A is a bar graph comparing the yields of various components contained in the products resulted from the hydrocracking reaction of a virgin HDPE feedstock versus the products resulted from the hydrocracking reaction of a post-consumer recycled (PCR) material, using a metal zeolite catalyst under the reaction conditions described in Example 3A. FIG. 7B is a bar graph comparing the yields of various components contained in the products resulted from the hydrocracking reaction of a virgin HDPE feedstock versus the products resulted from the hydrocracking reaction of a post-consumer recycled (PCR) material, using an iron oxide catalyst under the reaction conditions described in Example 3B. For each feedstock in each bar graph, the graph displays four product components: gas (C1-C3), naphtha (C4-C12), kerosene (C13-C20), and solids (C20+). The y-axis on the left shows product composition percentage from 0 to 100%, while the y-axis on the right shows mass balance percentage.DETAILED DESCRIPTION OF THE INVENTION

[0021] The disclosure provides a novel process and apparatus / system for converting a carbon-containing feedstock (such as a polymer-based feedstock) into an alkane-containing product stream using catalysts comprising at least one transition metal or transition metal oxide and containing no acid sites. In this disclosure, the conventional two-step catalytic processes for plastic conversion has been simplified into one-step. For instance, the acid-site cracking in the conventional two-step catalytic processes is replaced with thermal cracking (cracking with only temperature) in the new process, and the catalyst used in the new process performs the hydrogenation function. Thus, the new process can be carried out in a single step or as a one-pot fashion, resulting in simplified operations and reduced costs. The use of the catalysts without acid sites provides improved tolerance to contaminants that are typically present in recycled materials and may be more cost effective, as compared to a typical bifunctional catalyst used in a hydrocracking process. The catalyst described herein may result in improved catalyst performance when processing contaminated feedstocks. This enhanced tolerance to impurities may be particularly beneficial when dealing with post-consumer or post-industrial recycled materials, which often contain various additives and contaminants.The Problems of Catalyst Deactivation by the Contaminants in the Feedstock

[0022] Many carbon-containing feedstocks can contain contaminants. In particular, plastic waste (such as a post-consumer resin (PCR) or a post-industrial resin (PIR)) often contain several different types of polymers, fillers, stabilizing agents, and / or contaminants. For instance, FIGS. 1A and 1B show examples of the diverse nature of the contaminants possibly contained in a polyethylene post-consumer recycled (PE-PCR) material by an X-ray fluorescence (XRF) elemental analysis and a high-performance liquid chromatography (HPLC) chromatogram.

[0023] The typical bifunctional catalyst may be sensitive to these contaminants contained in the plastic waste. To illustrate how the processing of a plastic waste material with a bifunctional catalyst can deactivate certain active sites of the catalyst, an experiment was conducted with a series of polymer samples prepared by mixing a virgin HDPE with increasing percentages of PCR content (virgin HDPE, HDPE+1% PCR, HDPE+5% PCR, HDPE+10% PCR, HDPE+20% PCR, HDPE+50% PCR, 100% PCR) to mimic various contaminants removed from a PCR material. In this experiment, the HDPE and PCT were mixed physically, the mixed polymer samples were extruded for homogeneity, and the extruded samples were cryo-milled to powder. As shown in the XRF analysis results in FIG. 2A, the primary contaminants were Al, Si, S, Cl, Ca, Ti, Fe, and Zn, with many of which overlapping with those identified in an XRF analysis of a typical PE-PCR material shown in FIG. 1A. In FIG. 2A, the increase of the contaminant concentrations is proportional to the PCR weight fraction. This series of polymer samples were then hydrocracked with a bifunctional catalyst, NiMo / H-USY catalyst, with the following reaction conditions: 400 mg of PCR, 100 mg of catalyst, at 310° C., 50 bar of H2, for 1 hour. As shown in the production compositional analysis in FIG. 2B, the catalyst activity was high in the absence of contaminants, resulting in a high yield of liquid product, particularly naphtha. As the contaminant concentration increased, the yield of liquid product, particularly naphtha, decreased, indicating the catalyst cracking functionality decreased during processing a high contaminant-containing PCR material. These results indicate that a typical bifunctional catalyst containing acid sites to crack a polymer feedstock can be deactivated in the presence of waste plastic due to contaminants. The higher concentration of contaminants, the more deactivation in the catalyst's activity.

[0024] This is why, in the hydrocracking reaction using a typical bifunctional catalyst containing acid sites to crack a polymer feedstock, a robust feedstock pre-treatment purification technology to clean the PCR and remove the contaminants in the PCR is typically necessary to ensure the catalyst's activities.The Novel Process

[0025] In this disclosure, the hydrocracking reaction in the novel process employs a catalyst that does not contain an acid site; the catalyst used in the new process performs the hydrogenation function. The catalyst does have a high tolerance of a high contaminant concentration without sacrificing the catalyst activity, and thus minimizes or eliminates the need for a feedstock pre-treatment purification step to remove contaminants in the feedstock.

[0026] Accordingly, in one aspect of the invention, provided herein is a process for chemically treating a carbon-containing feedstock. The process comprises contacting the carbon-containing feedstock and a hydrogen stream in the presence of a hydrocracking catalyst, at an elevated temperature, to produce an alkane-containing product stream. The hydrocracking catalyst comprises at least one transition metal or transition metal oxide, and the hydrocracking catalyst does not contain an acid site. In some embodiments, the contacting step may be a reacting step.

[0027] Another related aspect of the invention relates to a process for depolymerizing a polymer-based feedstock. The process comprises reacting a polymer-based feedstock with a hydrogen stream in the presence of a hydrocracking catalyst, at an elevated temperature, in a one-step, hydrocracking reaction, to depolymerize the polymer-based feedstock and form an alkane-containing product stream. The hydrocracking catalyst comprises at least one transition metal or transition metal oxide, and the hydrocracking catalyst does not contain an acid site.The Feedstock

[0028] The feedstock used in the processes described herein can be any carbon-containing feedstock (e.g., a polymer-based feedstock). The process described herein may demonstrate improved tolerance to feedstock variability. In some embodiments, the hydrocracking catalyst's performance may be less sensitive to changes in feedstock composition or quality compared to conventional catalysts. This robustness may enable the process to handle a wider range of carbon-containing feedstocks, including mixed plastic waste streams or materials with varying levels of contamination.

[0029] The carbon-containing feedstock (e.g., a polymer-based feedstock) may be a petroleum-based resin (e.g., petroleum-based virgin resin), bio-based resin, recycled resin, or combinations thereof. For instance, the carbon-containing feedstock (e.g., a polymer-based feedstock) may comprise a virgin resin, a recycled resin, or combinations thereof. In some embodiments, the carbon-containing feedstock (e.g., a polymer-based feedstock) may comprise a combination of a recycled resin, biobased resin, and optionally a petroleum-based resin such that the resulting composition achieves low or neutral carbon emission (or even a carbon uptake).

[0030] The recycled resin may comprise a post-consumer resin (PCR), a post-industrial resin (PIR), or combinations thereof, including regrind, scraps and defective articles. PCR refers to resins that are recycled after consumer use, whereas PIR refers to resins that are recycled from industrial materials and / or processes (for example, cuttings of materials used in making other articles). The recycled resin may include resins having been used in rigid applications (such as from blow molded articles, including 3D-shaped articles) as well as in flexible applications (such as from films). The recycled resin may be of any color, including, but not limited to, black, white, or grey, depending on the color used in the ultimate article. The form of the recycled resin is not particularly limited, and may be in pellets, flakes, and agglomerated films. In some embodiments, the recycled resin used is a PCR or PIR that comprises one or more polyolefins. In some embodiments, the recycled resin is a recycled material according to ISO 14021. In some embodiments, the carbon-containing feedstock (e.g., a polymer-based feedstock) is a post-consumer resin (PCR) or a post-industrial resin (PIR).

[0031] In some embodiments, the carbon-containing feedstock is a polymer-based feedstock. Exemplary polymer-based feedstocks are polyolefins, polyvinyl chlorides, polyesters, polystyrenes, polyacrylates, polymethacrylates, polyamides, polycarbonates, and mixtures thereof.

[0032] In some implementations, the polymer-based feedstock may be a petroleum-based virgin resin, bio-based resin, recycled resin, or combinations thereof. The polymer-based feedstock may also be a post-consumer resin (PCR) or a post-industrial resin (PIR).

[0033] Suitable polyolefins include those prepared from linear, branched, or cyclic olefin monomers having 2 to 20 carbon atoms, 2 to 16 carbon atoms, or 2 to 12 carbon atoms. Exemplary olefin monomers are α-olefins including but not limited to ethylene, propylene, 1-butene, 2-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 4,6-dimethyl-1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene, vinylcyclohexane, styrene, tetracyclododecene, norbornene, 5-ethylidene-2-norbornene (ENB), and combinations thereof. These olefins may each contain a heteroatom such as an oxygen, nitrogen, or silicon atom.

[0034] Exemplary polyolefins include a propylene-based polymer, an ethylene-based polymers, an ethylene-vinyl ester polymer, or a C4-C12 olefin-based polymer. The ethylene-based polymer contained can be low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), medium-density polyethylene (MDPE), polyethylene wax, ultrahigh-molecular weight polyethylene, ethylene copolymer, and combinations thereof.

[0035] Suitable polyolefins also include a copolymer prepared from two or more olefin comonomers, which include polyene comonomers (having 3 to 20 carbon atoms including but not limited to butadiene (e.g., 1,3-butadiene), isoprene, pentadiene (e.g., 1,3-pentadiene; 1,4-pentadiene; 3-methyl-1,4-pentadiene; 3,3-dimethyl-1,4-pentadiene), dimethylbutadiene, dimethylpentadiene, hexadiene (e.g., 1,3-hexadiene; 1,4-hexadiene; 1,5-hexadiene; 4-methyl-1,4-hexadiene; 5-methyl-1,4-hexadiene; 3-methyl-1,5-hexadiene; 3,4-dimethyl-1,5-hexadiene), heptadiene (e.g., 1,3-heptadiene; 1,4-heptadiene; 1,5-heptadiene; 1,6-heptadiene; 6-methyl-1,5-heptadiene), methylhexadiene, dimethylhexadiene, octadiene (e.g., 1,3-octadiene; 1,4-octadiene; 1,5-octadiene; 1,6-octadiene; 1,7-octadiene; 7-methyl-1,6-octadiene; 3,7-dimethyl-1,6-octadiene; 5,7-dimethyl-1,6-octadiene), nonadienes (e.g., 1,8-nonadiene), decadiene (e.g., 1,9-decadiene), undecadiene (e.g., 1,10-undecadiene), dicyclopentadienes, octatriene (e.g., 3,7,11-trimethyl-1,6,10 octatriene), 4-vinyl cyclohexene, dicyclopentadiene, vinyl comonomers (including but not limited to acrylonitrile and acrylamide, and their derivatives), and vinylaromatic comonomers (including but not limited to styrene and its derivatives, such as α-methylstyrene); any of which may each contain a heteroatom such as an oxygen, nitrogen, or silicon atom.

[0036] Suitable styrene-based polymers include but are not limited to polymers prepared from monomers such as styrene, α-methylstyrene, p-methylstyrene, vinylxylene, vinylnaphthalene, and mixtures thereof; and optionally a diene comonomer such as butadiene, isoprene, pentadiene, and mixtures thereof.

[0037] Suitable polyesters include but are not limited to polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, polycarbonate, copolymerization of polyesters with ethylene terephthalate as a main repeating unit (such as polyethylene(terephthalate / isophthalate), polyethylene(terephthalate / isophthalate), polyethylene(terephthalate / adipate), polyethylene(terephthalate / sodium sulfoisophthalate), polyethylene(terephthalate / sodium isophthalate), polyethylene (terephthalate / phenyl-dicarboxylate) and polyethylene(terephthalate / decane dicarboxylate)), and copolymerization of polyesters with a butylene terephthalate as a main repeating unit (such as polybutylene(terephthalate / isophthalate)), polybutylene(terephthalate / adipate), polybutylene(terephthalate / sebacate), polybutylene(terephthalate / decane dicarboxylate)).

[0038] Suitable polyamides include aliphatic polyamides such as nylon-6, nylon-66, nylon-10, nylon-12 and nylon-46; and aromatic polyamides produced from aromatic dicarboxylic acid and aliphatic diamine.

[0039] The carbon-containing feedstock (e.g., a polymer-based feedstock) may be plastic materials containing, but are not limited to, acrylonitrile butadiene styrene (ABS), polyacetal, acrylic, ionomer, polyamide in general, Nylon 6, Nylon 6 / 6, Nylon 6 / 9, Nylon 6 / 10, Nylon 6 / 12, Nylon 11, Nylon 12, polycarbonate, polyester (PBT), polyester (PET), polyether ether ketone, polyethylene, polyolefin in general, polyphenylene ether, polyphenylene sulfide, polypropylene, polystyrene, polysulfone, polyurethane, styrene acrylonitrile (SAN) and thermoplastic elastomer. In some embodiments, the carbon-containing feedstock contain intermediate thermoplastics, such as polymethyl methacrylate, acrylonitrile-butadiene-styrene, acrylonitrile / acrylate / styrene, acrylonitrile / ethylene-propylene-diene monomer (EPDM) / styrene, styrene / maleic anhydride copolymers and rubber blends, cellulose-acetate-butyral, thermoplastic olefin elastomer, and the like.The Hydrocracking Catalyst

[0040] The hydrocracking catalyst used in the process may comprise at least one transition metal or transition metal oxide. The metal of the at least one transition metal or transition metal oxide is typically a Group VI to Group X metal of the periodic table. The metal can be a noble metal (palladium or platinum) or non-noble metal of group VI-A (molybdenum or tungsten) and group VIII-A (cobalt or nickel) of the periodic table. For instance, the metal in the transition metal or transition metal oxide of the hydrocracking catalyst may be Fe, W, Ni, Mo, Co, Ir, Pd, Pt, and combinations thereof. For the transition metal oxide, all the oxidation states of the transition metal are included in the “oxide” definition.

[0041] In some embodiments, the hydrocracking catalyst comprises two or more of transition metals, transition metal oxides, and combinations thereof. The catalyst may be a blend of two or more different materials within the same type (e.g., two or more different transition metals) or two or more different materials with different types (e.g., one transition metal and one transition metal oxide). These transition metals or transition metal oxides are desirable to the hydrocracking reaction, as they provide reaction sites for hydrogenation.

[0042] In some embodiments, the hydrocracking catalyst comprises FeOx, WOx, NiMo, CoMo, MoOx, NiW, or a combination thereof. The “x” in the metal oxide represents the oxidation number of oxygen, which includes all possible values corresponding to all the oxidation states of the metals. In some implementations, the hydrocracking catalyst comprises FeOx (such as Fe2O3). In some embodiments, the hydrocracking catalyst comprises FeOx (such as Fe2O3) and another transition metal or transition metal oxide as co-catalyst, such as one of WOx, NiMo, CoMo, MoOx, and NiW.

[0043] A characteristic of this hydrocracking catalyst is that the hydrocracking catalyst may not contain an acid site. This characteristic may allow the catalyst to be more tolerant to contaminants that may be present in certain feedstocks, such as recycled materials. This is more advantageous over a typical bifunctional catalyst that contains acid sites by containing an acidic support (e.g., an oxide-containing support) or having transition metal(s) supported over an acidic support (e.g., oxide-containing support). As discussed herein, those typical bifunctional catalysts having acid sites can be sensitive to the contaminants contained in the plastic waste and thus requiring additional feedstock pre-treatment steps to remove the contaminants contained in the feedstock. Accordingly, in some embodiments, the hydrocracking catalyst does not comprise an acidic oxide-containing support such as an acid aluminosilicate in the form of an acidic zeolite. In some embodiments, the hydrocracking catalyst does not comprise a transition metal separately supported on an oxide-containing support (such as an aluminum oxide, silicon oxide, aluminosilicate, or combinations thereof; for instance, an aluminosilicate in the form of a zeolite). The hydrocracking catalyst described herein may have an enhanced catalyst stability and longevity. This improved stability may be particularly beneficial when processing feedstocks containing contaminants or impurities, such as those commonly found in post-consumer recycled materials.The One-Step or One-Pot Process

[0044] One of the characteristics of the disclosed process is that the process can be a one-step or one-pot process.

[0045] In some embodiments, the process does not involve a separate pyrolysis of the carbon-containing feedstock (e.g., the polymer-based feedstock). A separate step of thermal cracking (pyrolysis) can produce large amounts of unsaturated hydrocarbons and would require a further step of hydrogenation to convert unsaturated hydrocarbons to saturated hydrocarbons. On the other hand, the process may employ a single-stage, hydrocracking unit, i.e., the cracking and hydrogeneration of the carbon-containing feedstock (e.g., a polymer-based feedstock) are carried out in one-step and one-pot process.

[0046] In some embodiments, the process may not involve a step of pre-treating the carbon-containing feedstock (e.g., the polymer-based feedstock) with a solvent medium to remove any contaminant(s) in the feedstock, prior to the contacting or the reacting step. A contaminant-removal pre-treatment step for the feedstock may be required for a bifunctional catalyst that contains acid site(s) to remove any contaminants in the carbon-containing feedstock (e.g., the polymer-based feedstock) in order to avoid catalyst deactivation. On the other hand, the process employing the catalyst that does not contain acid sites can be carried out with high efficiency and high yield in one-step and one-pot process, without the pre-treatment purification of the feedstock to remove the contaminants.

[0047] The one-step or one-pot nature of the process may lead to increased efficiency and reduced operational complexity. By eliminating the need for separate pyrolysis or feedstock pre-treatment purification steps, the process may require less equipment and energy input, lowering overall costs and improving the economic viability of chemical recycling operations. Additionally, by combining the depolymerization and hydrogenation steps into a single reaction, the process may require less equipment and energy input compared to multi-step approaches. This streamlined operation may lower overall costs and improve the economic viability of polymer recycling operations.The Reaction Conditions and Reaction Products

[0048] In some embodiments, the process may further involve pre-mixing the carbon-containing feedstock (e.g., the polymer-based feedstock) with a solvent medium, optionally with the hydrocracking catalyst, prior to the contacting or reacting step. The pre-mixing step may be carried out by extrusion or agitation. The pre-mixing step may be carried out at a temperature ranging from about 100 to about 400° C. (such as from about 100 to about 300° C.). The solvent medium typically is a liquid that can act as a medium to transport the polymer-based feedstock (e.g., a hot, viscous plastic waste) to the reactor.

[0049] The solvent medium may comprise a liquid hydrocarbon, oil, waxes or a mixture thereof. In some embodiments, the solvent medium comprises a liquid hydrocarbon.

[0050] The liquid hydrocarbon used as the solvent medium may come from the liquid product stream that is produced and / or separated from the process described herein. For instance, the liquid product stream (e.g., C4-C20 hydrocarbons), formed from the process described herein and separated from the gas product stream and / or solid product stream as described herein, can be used as the solvent medium to mix with the polymer-based feedstock and transport the polymer-based feedstock to the reactor. As another example, diesel, kerosene or kerosene like product stream (e.g., C13-C20 hydrocarbons), formed from the process described herein and separated from the gas product stream, naphtha or naphtha like product stream, and / or solid product stream as described herein, can be used as the solvent medium to mix with the polymer-based feedstock and transport the polymer-based feedstock to the reactor. Thus, in some embodiments, the solvent medium comprises a liquid product stream (e.g., C4-C20 hydrocarbons), obtained from the depolymerization reaction. In some embodiments, the solvent medium comprises a diesel, kerosene or kerosene like product stream (e.g., C13-C20 hydrocarbons), obtained from the depolymerization reaction. In some embodiments, the solvent medium comprises a heavy-component stream (e.g., a C20+ product stream such as C20 to C50 product stream; and up to Mw 2000 Da) obtained from the depolymerization reaction. In some embodiments, the solvent medium comprises a mixture of these product streams.

[0051] The oil used as the solvent medium may be refinery oil, crude oil, vacuum gas oil (VGO), heavy mineral oil, residual oil, or a mixture thereof.

[0052] The weight ratio between the carbon-containing feedstock (e.g., the polymer-based feedstock) (including the solvent, if any) and the hydrocracking catalyst used in the process may range from about 1000:1 to about 1:10. For instance, the weight ratio between the feedstock mixture and the catalyst may range from about 500:1 to about 1:5, from about 300:1 to about 1:5, from about 200:1 to about 1:5, from about 100:1 to about 1:5, from about 50:1 to about 1:5, from about 10:1 to about 1:5, from about 5:1 to about 1:5, from about 3:1 to about 1:3, from about 300:1 to about 1:3, from about 200:1 to about 1:3, from about 100:1 to about 1:3, from about 50:1 to about 1:3, from about 10:1 to about 1:3, from about 5:1 to about 1:3, or from about 3:1 to about 1:3.

[0053] The catalyst containing the transition metal or transition metal oxide may be hydrotreated prior to the contacting or reacting step. In some embodiments, the hydrotreating of the catalyst may comprise calcining the transition metal or transition metal oxide at a temperature ranging from about 400° C. to about 600° C. In some embodiments, the hydrotreating of the catalyst may comprise exposing the transition metal or transition metal oxide to a hydrogen stream at a temperature ranging from about 400° C. to about 600° C. to reduce the transition metal or transition metal oxide. In some embodiments, the hydrotreating of the catalyst may comprise both the calcining step and the reducing step. The temperature of the calcining and / or reducing step may range from about 450° C. to 600° C., from about 500° C. to about 600° C., or from about 530° C. to about 570° C. In one embodiment, the temperature of the calcining and / or reducing step is at about 550° C. In one embodiment, the catalyst may be calcined at 550° C. for 4 hours under air. In one embodiment, the catalyst may be further reduced at 550° C. for 4 hours under H2. The significance of the reducing step is illustrated in the Examples, e.g., in Example 2A and FIG. 3, showing that under the same reaction conditions, using the reduced catalyst significantly promoted the production of liquid products, in particular the naphtha; whereas using the catalyst treated only with the calcining step without the reducing step produced more solids.

[0054] The hydrocracking reaction is carried out in the presence of hydrogen. Hydrogen is provided by a hydrogen stream, which may be a gas of pure hydrogen, or a mixture containing hydrogen and other gases such as CO2, CO, water, etc. The hydrogen stream may be fed into the reactor alone or may be fed to the reactor along with the carbon-containing feedstock (e.g., a polymer-based feedstock). The significance of hydrogen for the catalytic cracking of the carbon-containing feedstock (e.g., a polymer-based feedstock) is illustrated in the Examples, e.g., in comparing Example 2A to Example 2B illustrated in FIGS. 5-6, showing that the presence of H2 significantly improves the product stabilization as well as results in a high-yield and high-quality saturated, liquid product, particularly high-yield and high-quality of naphtha.

[0055] The reaction is typically performed at moderate temperatures, ranging from about 400° C. to 550° C. For instance, the reaction temperature may range from about 400° C. to 530° C., from about 400° C. to about 500° C., from about 400° C. to about 480° C., from about 400° C. to about 450° C., from about 410° C. to about 530° C., from about 410° C. to about 500° C., from about 410° C. to about 480° C., from about 410° C. to about 450° C., from about 430° C. to about 530° C., from about 430° C. to about 500° C., from about 430° C. to about 480° C., or from about 430° C. to about 450° C. In one embodiment, the reaction temperature is at about 440° C.

[0056] The reaction is typically performed at a hydrogen pressure ranging from about 10 bar to about 350 bar. For instance, the reaction hydrogen pressure may range from about 10 bar to about 200 bar, from about 10 bar to about 150 bar, from about 10 bar to about 100 bar, from about 10 bar to about 80 bar, from about 10 bar to about 60 bar, from about 20 bar to about 150 bar, from about 20 bar to 100 bar, from about 20 bar to 80 bar, from about 20 bar to about 60 bar, from about 30 bar to about 150 bar, from about 30 bar to about 100 bar, from about 30 bar to about 80 bar, from about 30 bar to about 60 bar, about 40 bar to about 150 bar, from about 40 bar to about 100 bar, from 40 bar to 80 bar, from 40 bar to 60 bar, or from about 45 bar to about 55 bar. In one embodiment, the reaction is carried out under a hydrogen pressure at about 50 bar.

[0057] The products obtained from the hydrocracking reaction include saturated hydrocarbons, such as alkanes, and optionally unsaturated hydrocarbons, such as unsaturated acyclic hydrocarbons (e.g., alkenes) and / or aromatics.

[0058] The product streams obtained from the hydrocracking reaction include a liquid product stream (primarily C4-C20 hydrocarbons, e.g., naphtha or naphtha like product, and / or diesel, kerosene or kerosene like product), an optional gas product stream (primarily C1-C3 hydrocarbons), and an optional solid product stream (primarily C20+ hydrocarbons).

[0059] In some embodiments, the process produces an alkane-containing product stream comprises C1-C20 hydrocarbons (e.g., C1-C20 alkanes).

[0060] By using the hydrocracking catalyst and hydrocracking reaction described herein, the process may exhibit high selectivity towards certain desired product fractions, such as saturated hydrocarbons and produce an alkane-containing product stream containing a reduced amount or minimized amount of unsaturated hydrocarbons. This selectivity may allow for the production of valuable chemical feedstocks or fuel components with minimal additional processing or separation steps. The ability to tune the product distribution by adjusting process parameters may provide flexibility in meeting varying market demands or product specifications.

[0061] The process can produce an alkane-containing product stream (e.g., a C1-C3 product stream, C4-C12 product stream, and / or C20+ product stream) containing more than 50% (e.g., more than 55%, more than 60%, more than 70%, or more than 80%) by weight of saturated hydrocarbons, based on the total weight of the product stream. In some embodiments, the process can produce an alkane-containing product stream containing more than 85% (such as more than 90%, more than 95%, or more than 99%) by weight of saturated hydrocarbons, based on the total weight of the product stream.

[0062] The process can produce an alkane-containing product stream (e.g., a C1-C3 product stream, C4-C12 product stream, and / or C20+ product stream) containing no more than 30% (e.g., no more than 25%, or no more than 20%) by weight of unsaturated hydrocarbons, based on the total weight of the product stream. In some embodiments, the process can produce an alkane-containing product stream containing no more than 15% (such as no more than 12%, no more than 10%, no more than 7%, no more than 5%, no more than 4%, no more than 3%, no more than 2%, no more than 1%, or no more than 0.5%, by weight, of unsaturated hydrocarbons, based on the total weight of the product stream.

[0063] The process can produce an alkane-containing product stream (e.g., a C1-C3 product stream, C4-C12 product stream, and / or C20+ product stream) containing no more than 20% (e.g., no more than 18%, no more than 16%, no more than 15%) by weight of aromatic compounds, based on the total weight of the product stream. In some embodiments, the process can produce an alkane-containing product stream containing no more than 10% (such as no more than 8%, no more than 5%, no more than 4%, no more than 3%, no more than 2%, no more than 1%, no more than 0.5%, no more than 0.3%, or no more than 0.1%) by weight of aromatic compounds, based on the total weight of the product stream.

[0064] In some embodiments, the process may further comprise hydrotreating the product stream generated in the reaction step. This hydrotreating may be carried out in a hydrotreating unit with a hydrogen stream in the presence of an aluminum supported catalyst (e.g., a catalyst containing one transition metal or transition metal oxide supported on an aluminum oxide). In some embodiments, the metal can be a Group VI to Group X metal of the periodic table, such as Fe, W, Ni, Mo, Co, Ir, Pd, Pt, and combinations thereof. In some embodiments, the catalyst for the hydrotreating step may be NiMo supported by alumina, CoMo supported by alumina, or NiW supported by alumina. The hydrotreating step is typically performed at moderate temperatures, ranging from about 400° C. to 450° C. (e.g., from about 410° C. to about 450° C., or from about 430° C. to about 450° C.), under a hydrogen pressure ranging from about 10 bar to about 350 bar (such as from about 10 to about 200 bar, from about 10 to about 100 bar, or from about 40 to about 60 bar). This hydrotreating step is optionally used to further reduce unsaturated hydrocarbon in the final product stream. In some embodiments, this additional hydrotreating step can further reduce the amounts of unsaturated hydrocarbons to no more than 5% (such as no more than 4%, no more than 3%, no more than 2%, no more than 1%, or no more than 0.5%), by weight, based on the total weight of the final product stream.

[0065] By using the hydrocracking catalyst and hydrocracking reaction described herein, the process may also exhibit high selectivity towards certain desired product fractions, such as C4-C12 hydrocarbons. This selectivity may allow for the production of valuable chemical feedstocks or fuel components with minimal additional processing or separation steps. The ability to tune the product distribution by adjusting process parameters may provide flexibility in meeting varying market demands or product specifications. In some embodiments, the process has a selectivity towards naphtha or naphtha-like product (e.g., C4-C12 hydrocarbons) of at least 50%, for instance, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 99%, at least 99%, or virtually 100%, by weight, based on the total weight of the product stream.

[0066] In some embodiments, the process may further comprise separating the alkane-containing product stream into two or more different product streams based on the molecular weight of the components. The separation may be based on the molecular weight of the components of the product stream from the hydrocracking reaction. Thus, the process may further comprise the step of separating the product stream from the hydrocracking reaction (e.g., the alkane-containing product stream) into two or more different product streams based on the molecular weight of the components of the product stream from the hydrocracking reaction (e.g., the alkane-containing product stream).

[0067] The different product streams may be a light-component stream (e.g., a gas stream, C1-C3 product stream), a naphtha or naphtha-like stream (e.g., a C4-C12 product stream), a diesel or kerosene product stream (e.g., a C13-C20 product stream), and / or a heavy-component stream (e.g., a C20+ product stream).

[0068] In some implementations, the process may exhibit high selectivity towards desired product fractions, such as C4-C12 hydrocarbons. This selectivity may allow for the production of valuable chemical feedstocks or fuel components with minimal additional processing or separation steps. The ability to adjust process parameters to tune the product distribution may provide flexibility in meeting varying market demands or product specifications.

[0069] Additional aspects of the invention relate to various products or product streams produced from the process described herein. Thus, one aspect of the invention relates to an alkane-containing mixture obtained from the processes described herein.

[0070] In some embodiments, the disclosure provides an alkane-containing mixture obtained from the process for chemically treating a carbon-containing feedstock, said process comprising contacting the carbon-containing feedstock and a hydrogen stream in the presence of a hydrocracking catalyst, at an elevated temperature, to produce an alkane-containing product stream. The hydrocracking catalyst comprises at least one transition metal or transition metal oxide, and the hydrocracking catalyst does not contain an acid site.

[0071] In some embodiments, the disclosure provides an alkane-containing mixture obtained from the process for depolymerizing a polymer-based feedstock, the process comprising reacting a polymer-based feedstock with a hydrogen stream in the presence of a hydrocracking catalyst, at an elevated temperature, in a one-step, hydrocracking reaction, to depolymerize the polymer-based feedstock and form an alkane-containing product stream. The hydrocracking catalyst comprises at least one transition metal or transition metal oxide, and the hydrocracking catalyst does not contain an acid site.

[0072] All above descriptions and all embodiments discussed in the above aspects relating to the process for chemically treating a carbon-containing feedstock and the process for depolymerizing a polymer-based feedstock, including various aspects of the feedstock, the hydrogen stream, the hydrocracking catalyst, and the hydrocracking reaction conditions are applicable to this aspect of the invention relating to an alkane-containing mixture obtained from the above processes.

[0073] In some embodiments, the alkane-containing mixture obtained from the process described herein may comprise C1-C20 hydrocarbons, particularly a C4-C12 hydrocarbon product stream. The processes described herein can produce a high-yield and high quality naphtha or naphtha-like product. In some embodiments, the C4-C12 hydrocarbon product stream comprises about 85-100% saturated hydrocarbons (e.g., n-paraffinic naphthalene or iso-paraffinic naphthalene); and / or no more than about 15% (such as no more than 12%, no more than 10%, no more than 7%, or no more than 5%) unsaturated hydrocarbons (e.g., olefins); and / or no more than 8% (such as no more than 5%, no more than 1%, no more than 0.5%, no more than 0.3%, or no more than 0.1%) aromatic hydrocarbons.The System for Carrying Out the Process

[0074] Another aspect of the disclosure relates to a system / apparatus for chemically treating a carbon-containing feedstock. The system comprises a reactor receiving the carbon-containing feedstock, a hydrogen stream, and at least one hydrocracking catalyst. The reactor is configured to provide an elevated temperature and to contact the carbon-containing feedstock and the hydrogen stream in the presence of the hydrocracking catalyst to produce an alkane-containing product stream. The hydrocracking catalyst comprises at least one transition metal or transition metal oxide, and the hydrocracking catalyst does not contain an acid site.

[0075] Another aspect of the disclosure relates to a system / apparatus for depolymerizing a polymer-based feedstock. The system / apparatus comprises a reactor receiving the polymer-based feedstock, a hydrogen stream, and at least one hydrocracking catalyst. The reactor is configured to provide an elevated temperature and to react the polymer-based feedstock with the hydrogen stream in the presence of the hydrocracking catalyst in a one-step, hydrocracking reaction, to depolymerize the polymer-based feedstock and form an alkane-containing product stream. The hydrocracking catalyst comprises at least one transition metal or transition metal oxide, and the hydrocracking catalyst does not contain an acid site.

[0076] All above descriptions and all embodiments discussed in the above aspects relating to the process for chemically treating a carbon-containing feedstock and the process for depolymerizing a polymer-based feedstock, including various aspects of the feedstock, the hydrogen stream, the hydrocracking catalyst, and the hydrocracking reaction conditions are applicable to this aspect of the invention relating to a system / apparatus for chemically treating a carbon-containing feedstock or a system / apparatus for depolymerizing a polymer-based feedstock.

[0077] The hydrocracking reaction can be carried out in a reactor, which can comprise one or more reactor inlets for receiving the carbon-containing feedstock can comprise one or more reactor inlets for receiving the carbon-containing feedstock (e.g., polymer-based feedstock), a hydrogen stream, and at least one hydrocracking catalyst; and one or more reactor outlets for outputting the product stream. The heterogeneous reactor can contain a catalytic bed for holding the hydrocracking catalyst. The reactor can further contain a heating module for controlling the reaction temperature. The reactor can further contain a pressure control module for controlling the hydrogen pressure during the reaction.

[0078] The reactor may be an ebullated reactor, a slurry reactor, a continuous flow reactor (such as a continuous stirred tank reactor (CSTR)), or a fixed bed reactor. The hydrocracking system may use a slurry, ebullated, CSTR, or fixed bed reactor configuration. The reaction may also be an adiabatic reactor, such as a microbomb batch reactor. The choice of the reactor for operating the process may be determined by the choice of the hydrocracking catalyst. The system's flexibility in reactor types may allow for adjustment based on specific feedstock characteristics and desired product outputs. This adaptability may enable the system to handle a wide range of carbon-containing feedstocks, from homogeneous materials to mixed waste streams.

[0079] In some embodiments, the system / apparatus may have a single reactor. The use of a single reactor configuration may simplify the overall process design and reduce capital costs. This streamlined approach may lead to improved operational efficiency and easier maintenance compared to multi-reactor systems.

[0080] As discussed above, the reaction herein employs a single-stage, hydrocracking unit, i.e., the cracking and hydrotreating of the carbon-containing feedstock (e.g., a polymer-based feedstock) are carried out in one-step. Thus, in some embodiments, the system / apparatus does not include a separate pyrolysis unit from the hydrocracking reactor, which may simplify the overall process and reduce energy consumption and equipment costs. This simplification may lead to lower operating costs and improved process economics, particularly for smaller-scale operations or distributed processing facilities.

[0081] In some embodiments, the system / apparatus may comprise a feed unit upstream to the reactor. In some implementations, the feed unit may pre-mix the carbon-containing feedstock or polymer-based feedstock with a solvent medium, and optionally with the catalyst, as described herein, prior to entering the reactor. The feed unit may comprise extrusion or agitated tank(s) for pre-mixing the carbon-containing feedstock or polymer-based feedstock with the solvent medium (and optionally with the catalyst). The inclusion of a feed unit upstream of the reactor may improve feedstock preparation and handling, by ensuring better contact between the feedstock and the catalyst.

[0082] In some embodiments, the system / apparatus may comprise a hydrotreating unit upstream to the reactor. The upstream hydrotreating unit may be used to hydrotreat the catalyst containing the transition metal or transition metal oxide used in the hydrocracking catalyst, based on the conditions described herein. The optional upstream hydrotreating unit may provide additional benefits in terms of catalyst performance and longevity. By hydrotreating the transition metal or transition metal oxide used in the hydrocracking catalyst, the system may achieve improved catalyst activity and stability, leading to higher conversion rates and extended catalyst lifetimes.

[0083] In some embodiments, the system / apparatus may comprise a hydrotreating unit downstream to the reactor. The downstream hydrotreating unit may hydrotreat the product stream generated in the reactor, based on the conditions described herein. The downstream hydrotreating system may comprise an ebullated or fixed bed reactor configuration.

[0084] In some embodiments, the system / apparatus may comprise a separator downstream of the reactor to separate the product stream (e.g., the alkane-containing product stream) into two or more different product streams. The separator may operate to separate different product streams from each other based on the molecular weight of the components of the product stream (e.g., the alkane-containing product stream). In some embodiments, the separator may be a gas separator, a cyclone, a flash vessel, or a distillation column.

[0085] The separated light-component stream (such as C1-C3 product stream or a C1-C4 product stream) can be used as a source of hydrogen stream, by using a steam reformer and shift reactor. The resulting hydrogen stream can be re-directed to the reactor for the hydrocracking reaction.

[0086] In some embodiments, the downstream units to the reactor may comprise a distillation unit and a gas separation unit, which may allow for further processing and separation of the product streams.

[0087] In some embodiments, the downstream units to the reactor may comprise a hydrotreating unit, a distillation unit, and a gas separation unit, which may allow for further processing and separation of the product streams.

[0088] The downstream components of the system, including the hydrotreating unit, separator, distillation unit, and gas separation unit, may allow for efficient product refinement and fractionation. This integrated approach to product processing may enable the production of high-quality alkane streams suitable for various applications in the chemical and fuel industries. The ability to separate and refine different product fractions within the same system may reduce the need for additional off-site processing, potentially improving overall process economics.Other Methods and Uses

[0089] Certain aspects of the invention relate to methods for controlling a carbon chain length distribution of a product stream obtained from depolymerizing a polymer-based feedstock, such as selectively converting the polymer-based feedstock to a liquid naphtha or naphtha-like product. Thus, according to one aspect of the invention, a method for selectively converting a polymer-based feedstock to a liquid naphtha or naphtha-like product is provided. The method comprises reacting a polymer-based feedstock with a hydrogen stream in the presence of a hydrocracking catalyst, at an elevated temperature, in a one-step, hydrocracking reaction, to depolymerize the polymer-based feedstock and form a liquid naphtha or naphtha-like product containing at least 50% by weight of C4-C12 hydrocarbons based on the total weight of the product. In some embodiments, the product may contain at least 55% (e.g., at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least 99%) by weight of C4-C12 hydrocarbons. The hydrocracking catalyst comprises at least one transition metal or transition metal oxide, which is optionally hydrotreated prior to the reacting step. The hydrocracking catalyst does not contain an acid site, and the reaction temperature ranges from about 400 to about 550° C. (such as from about 400 to about 500° C., from about 400 to about 450° C., or from about 430 to about 450° C.).

[0090] All above descriptions and all embodiments discussed in the above aspects relating to the process for chemically treating a carbon-containing feedstock and the process for depolymerizing a polymer-based feedstock, including various aspects of the feedstock, the hydrogen stream, the hydrocracking catalyst, and the hydrocracking reaction conditions are applicable to this aspect of the invention relating to a method for selectively converting a polymer-based feedstock to a liquid naphtha or naphtha-like product.

[0091] All above descriptions and all embodiments discussed in the above aspects relating to various products or product streams produced from the processes described herein, such as the alkane-containing mixture obtained from the processes described herein, are applicable to this aspect of the invention relating to a method for selectively converting a polymer-based feedstock to a liquid naphtha or naphtha-like product.

[0092] In some embodiments, the method does not involve a step of pre-treatment of the carbon-containing feedstock (e.g., the polymer-based feedstock) with a solvent medium to remove any contaminants contained in the feedstock prior to the reacting step. This may simplify the process and reduce the need for additional equipment or materials.

[0093] The method for selectively converting a polymer-based feedstock to a liquid naphtha or naphtha-like product may offer several advantages over conventional approaches. The one-step hydrocracking reaction may simplify the overall process by eliminating the need for separate depolymerization and hydrogenation steps. This streamlined approach may reduce equipment requirements and potentially lower energy consumption, which may lead to improved process economics and sustainability. The method described herein can be used for converting plastic waste into high quality naphtha.

[0094] Another aspect of the invention relates to a use of a catalyst comprising at least one transition metal or transition metal oxide for converting a carbon-containing feedstock (e.g., a polymer-based feedstock) into an alkane-containing product stream.

[0095] All above descriptions and all embodiments discussed in the above aspects relating to the process for chemically treating a carbon-containing feedstock and the process for depolymerizing a polymer-based feedstock, including various aspects of the feedstock, the hydrogen stream, the hydrocracking catalyst, and the hydrocracking reaction conditions are applicable to this aspect of the invention relating to a use of a catalyst comprising at least one transition metal or transition metal oxide for converting a carbon-containing feedstock (e.g., a polymer-based feedstock) into an alkane-containing product stream.

[0096] All above descriptions and all embodiments discussed in the above aspects relating to various products or product streams produced from the processes described herein, such as the alkane-containing mixture obtained from the processes described herein, are applicable to this aspect of the invention relating to a use of a catalyst comprising at least one transition metal or transition metal oxide for converting a carbon-containing feedstock (e.g., a polymer-based feedstock) into an alkane-containing product stream.

[0097] In some embodiments, the carbon-containing feedstock (e.g., a polymer-based feedstock) is converted into an alkane-containing product stream in a one-pot process. In some embodiments, the carbon-containing feedstock (e.g., a polymer-based feedstock) is not pre-treated with a solvent medium to remove any contaminant(s) in the feedstock, prior to a conversion reaction.

[0098] The alkane-containing mixture obtained from the process described herein can be further cracked to monomers, separated into various monomer components, and / or further fed to a polymerization unit for preparing polymers.

[0099] Thus, the process may further comprise a step of converting the alkane-containing mixture (e.g., the naphtha or naphtha-like product containing primarily C4-C12, hydrocarbons) obtained from the process described herein to produce olefins and / or aromatics. In some embodiments, the optional converting step comprises thermally cracking the alkane-containing mixture (e.g., the naphtha or naphtha-like product containing primarily C4-C12, hydrocarbons) obtained from the process described herein to obtain one or more lower hydrocarbons. In one embodiment, the alkane-containing mixture (e.g., the naphtha or naphtha-like product containing primarily C4-C12, hydrocarbons) obtained from the process described herein is mixed with high-pressure steam and fed through a furnace for the cracking step.

[0100] In some embodiments, the optional converting step results in a mixture of lower hydrocarbons comprising one or more of ethylene, propylene, butadiene, 1-butene, C5 crude (i.e., a mixture of C5 components), C5 dienes crude (i.e., a mixture of C5 components rich in cyclopentadiene, piperylene and isoprene), isoprene, and aromatics (e.g., benzene, toluene, xylenes, and cumene). In one embodiment, the optional converting step results in ethylene. In one embodiment, the optional converting step results in propylene. In one embodiment, the optional converting step results in ethylene and propylene.

[0101] In some embodiments, the process may further comprise a step for separating the monomer components produced from the converting step described above. In one embodiment, the process may further comprise a step for separating ethylene from other components produced from the converting step described above. In one embodiment, the process may further comprise a step for separating propylene from other components produced from the converting step described above. In one embodiment, the process may further comprise a step for separating ethylene and propylene from other components produced from the converting step described above.

[0102] In some embodiments, the process may further comprise a step of polymerizing the monomer components produced from the converting step and / or separating step described above, to form a polyolefin. In one embodiment, the process may further comprise a step of polymerizing ethylene produced from the converting step and / or separating step described above, to form a polyolefin. In one embodiment, the process may further comprise a step of polymerizing propylene produced from the converting step and / or separating step described above, to form a polyolefin. In one embodiment, the process may further comprise a step of polymerizing ethylene and propylene produced from the converting step and / or separating step described above, to form a polyolefin.EXAMPLES

[0103] The following examples are for illustrative purposes only and are not intended to limit, in any way, the scope of the present invention.Example 1—Preparation of an Exemplary Hydrocracking Catalyst

[0104] A commercial iron oxide catalyst obtained from Sigma Alderich was calcined at 550° C. for 4 hours under air (i.e., calcined iron oxide catalyst).

[0105] The calcined iron oxide catalyst was then reduced under the flow of hydrogen at 550 °C for 4 hours (i.e., reduced iron oxide catalyst under H2).

[0106] Example 2—Treating HDPE feedstock with exemplary hydrocracking catalysts2A. Activity test with a calcined / reduced iron oxide catalyst under H2:

[0107] About 400 mg of HDPE and 1200 mg of calcined iron oxide catalyst or reduced iron oxide catalyst, prepared according to Example 1, were loaded inside a microbomb batch reactor. The reactor was purged with He several times before being pressurized with H2 to 50 bar. The reactor was then immersed in a fluidized sand bath and held at 440° C. for 1 hour.2B. Activity Test With a Reduced Iron Oxide Catalyst Under He (a Control Experiment):

[0108] About 400 mg of HDPE and 1200 mg of reduced iron oxide catalyst prepared according to Example 1 was loaded inside a microbomb batch reactor. The reactor was purged with He several times before being pressurized with He to 50 bar. The reactor was then immersed in a fluidized sand bath and held at 440° C. for 1 hour.2C. Activity Test Without the Iron Oxide Catalyst (a Control Experiment):

[0109] About 400 mg of HDPE (without catalyst) was loaded inside a microbomb batch reactor. The reactor was purged with He several times before being pressurized with H2 to 50 bar. The reactor was then immersed in a fluidized sand bath and held at 440° C. for 1 hour.

[0110] The results of product compositions and product quality of various components contained in the reaction product comparing the above different catalytic reaction conditions are plotted in FIGS. 3-6.

[0111] FIG. 3 compares the yields of various components contained in the products resulted from the hydrocracking reaction of HDPE feedstock under three different catalyst conditions: without a Fe2O3 catalyst (2C), with calcined Fe2O3 (2A), and with reduced Fe2O3 (2A). As shown in FIG. 3, under the same reaction conditions, the liquid product (C4-C20, including both naphtha (C4-C12) and kerosene (C13-C20)) yield increased significantly in the product resulted from hydrocracking HDPE using the reduced Fe2O3 catalyst (2A), compared to the product resulted from the hydrocracking control experiment 2C (without Fe2O3 catalyst). In particular, the naphtha (C4-C12) yield using the reduced Fe2O3 catalyst increased by ~10% compared to that of the control experiment 2C, without Fe2O3 catalyst (reduced Fe2O3 catalyst vs. without Fe2O3 catalyst: ~54% vs. ~46%). Moreover, FIG. 3 also shows that the production of liquid products (C4-C20), in particular the naphtha (C4-C12), was significantly promoted by using the reduced Fe2O3 catalyst, whereas using the calcined Fe2O3 catalyst produced more solids (C20+).

[0112] FIGS. 4A-4B compare the compositions of the products resulted from the hydrocracking reaction of HDPE feedstock under two different catalyst conditions: using reduced Fe2O3 (2A) and without a Fe2O3 catalyst (2C). As shown in both FIGS. 4A and 4B, in both liquid stream (FIG. 4A) and gas stream (FIG. 4B), the percentage of the saturated products significantly increased in the product resulted from using the reduced Fe2O3 catalyst, compared to the product resulted from without a Fe2O3 catalyst (reduced Fe2O3 catalyst vs. without Fe2O3 catalyst: 87.9% vs. 80.2% for the liquid stream, and 93.3% vs. 85.2% for the gas stream). These results indicate the ability of the reduced Fe2O3 catalyst described herein to promote the hydrogenation to produce more saturated product. Thus, using the reduced Fe2O3 catalyst described herein can minimize the need of additional hydrogenation to convert unsaturated hydrocarbons to saturated hydrocarbons.

[0113] FIG. 5 compares the yields of various components contained in the products resulted from the hydrocracking reaction of HDPE feedstock using a reduced Fe2O3 catalyst under two different reaction conditions: under H2 versus under He. As shown in FIG. 5, using the same catalyst and under the otherwise same reaction conditions, the liquid product (C4-C20, including both naphtha (C4-C12) and kerosene (C13-C20)) yield as well as the gas product (C1-C3) yield have decreased in the product resulted from the reaction under He while the solid product (C20+) yield have increased in the product resulted from the reaction under He, compared to the products resulted from the reaction under H2. In particular, the naphtha (C4-C12) yield under He dropped significantly compared to the reaction under H2 (under He vs. under H2: ~30% vs. ~55%). The results indicate that although the reduced Fe2O3 catalyst was able to catalyze the hydrocracking reaction to produce an alkane-containing product stream under He stream, H2 stream was required for product stabilization as well as for obtaining a high-yield liquid product (e.g., containing high yield of naphtha) while reducing solid product.

[0114] FIGS. 6A-6B compare the compositions of the products resulted from the hydrocracking reaction of HDPE feedstock under two different reaction conditions under H2 versus under He. As shown in both FIGS. 6A and 6B, in both liquid stream (FIG. 6A) and gas stream (FIG. 6B), the percentage of the saturated products significantly decreased in the product resulted from the reaction under He while the percentage of the unsaturated products significantly increased in the product resulted from the reaction under He, compared to the product resulted from the reaction under H2 (under He vs. under H2: 60.4% vs. 87.9% for the liquid stream, and 75.6% vs. 93.3% for the gas stream). These results indicate that H2 stream was required for product stabilization as well as for obtaining a high-quality liquid product (e.g., containing high yield of saturated naphtha).Example 3—Treating Virgin HDPE and PCR Feedstock with Exemplary Hydrocracking Catalysts3A. Treating Virgin HDPE and PCR Feedstock with a Metal Zeolite Catalyst (a Comparative Experiment)

[0115] The NiMo-supported H-USY catalyst was used as a comparative metal zeolite catalyst in this example. NiMo / H-USY catalysts were synthesized using the sequential wetness impregnation method. Before synthesis, the H-USY zeolite (Zeolyst International), and the SiO2 catalyst supports were calcined at 550° C. for 4 hours under air. Prior to synthesis, the nickel nitrate and ammonium heptamolybdate metal precursors were dissolved separately in deionized water to make an aqueous solution. The molybdenum precursor solution was impregnated into the calcined support, followed by overnight drying at 110° C. After drying, the nickel precursor solution was impregnated, followed by overnight drying at 110° C. and calcination at 550° C. for 4 hours under air. The catalyst was then reduced under the flow of hydrogen at 450° C. for 4 hours.

[0116] HDPE feedstock: About 400 mg of virgin HDPE and 100 mg of NiMo / H-USY catalyst were loaded inside a microbomb batch reactor. The reactor was purged with He several times before being pressurized with H2 to 50 bar. The reactor was then immersed in a fluidized sand bath and held at 340° C. for 1 hour.

[0117] PCR feedstock: About 400 mg of post-consumer recycled (PCR) material and 100 mg of NiMo / H-USY catalyst were loaded inside a microbomb batch reactor. The reactor was purged with He several times before being pressurized with H2 to 50 bar. The reactor was then immersed in a fluidized sand bath and held at 340° C. for 1 hour.3B. Treating virgin HDPE and PCR feedstock with an iron oxide catalyst:

[0118] HDPE feedstock: About 400 mg of virgin HDPE and 1200 mg of reduced iron oxide catalyst, prepared according to Example 1, were loaded inside a microbomb batch reactor. The reactor was purged with He several times before being pressurized with H2 to 50 bar. The reactor was then immersed in a fluidized sand bath and held at 440° C. for 1 hour.

[0119] PCR feedstock: About 400 mg of post-consumer recycled (PCR) material and 1200 mg of reduced iron oxide catalyst, prepared according to Example 1, were loaded inside a microbomb batch reactor. The reactor was purged with He several times before being pressurized with H2 to 50 bar. The reactor was then immersed in a fluidized sand bath and held at 440° C. for 1 hour.

[0120] The results of product compositions and product quality of various components contained in the reaction product comparing the above different catalytic reaction conditions are plotted in FIGS. 7A-7B.

[0121] FIG. 7A compares the yields of various components contained in the products resulted from the hydrocracking reaction of a virgin HDPE feedstock versus the products resulted from the hydrocracking reaction of a post-consumer recycled (PCR) material, using a comparative catalyst, an acid-site containing bifunctional catalyst: NiMo / H-USY catalyst, under the reaction conditions described in Example 3A. As shown in FIG. 7A, the hydrocracking reaction of virgin HDPE provided a product with a high-yield and high-quality naphtha (C4-C12), with a naphtha yield at ~95%, and a high-quality naphtha, paraffinic, and naphthenic fractions of greater than 98 wt %. These results indicate that a bifunctional metal zeolite catalyst is able to produce high yields of high-quality naphtha from a clean feedstock, such as virgin HDPE feedstock used herein. On the other hand, under the same reaction conditions, the hydrocracking reaction of PCR, containing high concentrations of contaminants, produced a product with a low-yield liquid product, particularly low naphtha yield, while producing a large amount of solids (C20+). These results indicate that the acid-site containing, bifunctional metal zeolite was significantly deactivated by the presence of contaminants in the PCR polymer. Therefore, when using an acid-site containing, bifunctional metal zeolite as the hydrocracking catalyst, in order to obtain a high-yield, high-quality liquid product (such as naphtha) from a hydrocracking reaction, a PCR contaminant removal process would be desirable before the hydrocracking reaction.

[0122] FIG. 7B compares the yields of various components contained in the products resulted from the hydrocracking reaction of a virgin HDPE feedstock and the yields of various components contained in the products resulted from the hydrocracking reaction of a post-consumer recycled (PCR) material, using an iron oxide catalyst under the reaction conditions described in Example 3B. As shown in FIG. 7B, under the same reaction conditions, the iron oxide catalyst had similar performance whether the polymer being cracked was a virgin HDPE or a PCR sample. That is to say, by using the iron oxide catalyst, the yields of various components contained in the products resulted from the hydrocracking reaction of a virgin HDPE sample are very similar to the yields of corresponding components contained in the products resulted from the hydrocracking reaction of a PCR sample. For instance, the naphtha (C4-C12) yield by cracking a virgin HDPE polymer (~55%) is similar to the naphtha yield by cracking a PCR polymer (~58%). These results indicate that iron oxide catalyst is insensitive to the contaminants present in the feedstock. That is to say, removing contaminants are not needed when using an iron oxide catalyst, because the presence of contaminants in the PCR polymer did not affect the activity of the iron oxide catalyst and the yield of the products.

Claims

1. A process for chemically treating a carbon-containing feedstock, the process comprising:contacting the carbon-containing feedstock and a hydrogen stream in the presence of a hydrocracking catalyst, at an elevated temperature, to produce an alkane-containing product stream;wherein:the hydrocracking catalyst comprises at least one transition metal or transition metal oxide, andthe hydrocracking catalyst does not contain an acid site.

2. (canceled)3. A process for depolymerizing a polymer-based feedstock, comprising:reacting a polymer-based feedstock with a hydrogen stream in the presence of a hydrocracking catalyst, at an elevated temperature, in a one-step, hydrocracking reaction, to depolymerize the polymer-based feedstock and form an alkane-containing product stream,wherein:the hydrocracking catalyst comprises at least one transition metal or transition metal oxide, andthe hydrocracking catalyst does not contain an acid site.

4. The process of claim 3, wherein the process is a one-pot process.

5. (canceled)6. The process of claim 3, further comprising pre-mixing the polymer-based feedstock with a solvent medium, prior to the reacting step.7-9. (canceled)10. The process of claim 3, wherein the process does not involve a step of pre-treatment of the polymer-based feedstock with a solvent medium to remove any contaminant(s) in the feedstock, prior to the reacting step.

11. The process of claim 3, further comprising hydrotreating the transition metal or transition metal oxide, prior to the reacting step.

12. (canceled)13. The process of claim 3, wherein the hydrocracking catalyst does not comprise an acidic oxide-containing support, and / or does not comprise a transition metal separately supported on an oxide-containing support.

14. (canceled)15. The process of claim 3, wherein the metal in the transition metal or transition metal oxide is a Group VI to Group X metal, such as Mo, W, Fe, Co, Ir, Ni, Pd, Pt, or combinations thereof.

16. The process of claim 15, wherein the hydrocracking catalyst comprises FeOx, WOx, NiMo, CoMo, MoOx, NiW, or a combination thereof.17-18. (canceled)19. The process of claim 3, wherein the polymer-based feedstock is a petroleum-based virgin resin, bio-based resin, recycled resin, or combinations thereof.

20. (canceled)21. The process of claim 3, the reacting step is carried out:at a temperature ranging from about 400 to about 550° C.; and / orat a hydrogen pressure ranging from 10 to about 350 bar.

22. The process of claim 3, further comprising:hydrotreating the stream generated in the reaction step in a hydrotreating unit with a hydrogen stream in the presence of an aluminum-based catalyst.

23. The process of claim 3, wherein the alkane-containing product stream comprises C1-C20 hydrocarbons.

24. The process of claim 3, wherein the alkane-containing product stream contains:no more than 15% by weight of unsaturated hydrocarbons, based on the total weight of the product stream;no more than 10% by weight of aromatic compounds, based on the total weight of the product stream; and / ormore than 85% by weight of saturated hydrocarbons, based on the total weight of the product stream.25-26. (canceled)27. The process of claim 3, wherein the process has a selectivity towards C4-C12 hydrocarbons of at least 50%.

28. The process of claim 3, further comprising separating the alkane-containing product stream into two or more different product streams based on the molecular weight of the components of the alkane-containing product stream.

29. (canceled)30. An alkane-containing mixture obtained by the process of claim 3.

31. The alkane-containing mixture of claim 30, wherein the mixture is a C4-C12 hydrocarbon product stream, comprising:about 85-100% saturated hydrocarbons;no more than about 15% unsaturated hydrocarbons; andno more than 8% aromatic hydrocarbons.

32. A system for chemically treating a carbon-containing feedstock, the system comprising:a reactor receiving the carbon-containing feedstock, a hydrogen stream, and at least one hydrocracking catalyst, wherein the reactor is configured to provide an elevated temperature and to convert the carbon-containing feedstock into an alkane-containing product stream,wherein:the hydrocracking catalyst comprises at least one transition metal or transition metal oxide, andthe hydrocracking catalyst does not contain an acid site.33-40. (canceled)41. The process of claim 3,wherein the reaction temperature ranges from about 400 to about 550° C., andwherein the process selectively converts a polymer-based feedstock to a liquid naphtha or naphtha-like product containing at least 50% by weight of C4-C12 hydrocarbons based on the total weight of the product.42-45. (canceled)

Images