Method and apparatus for producing hydrogen

Abstract

The present disclosure provides a method and apparatus for producing hydrogen. The method includes: (a) contacting a plastic with a catalyst and a gas feed; and (b) applying microwaves at a first temperature. The apparatus includes a reactor for mixing the plastic with the catalyst to form a mixture; an inlet for introducing the gas feed; a microwave generator; an optional temperature sensor; and an outlet configured to vent product hydrogen formed in the reactor.

Description

[Technical field]

[0001] 1. Government Rights This invention was made under CRADA AGMT-1146 between Cecilia Energy, LLC and the National Energy Technology Laboratory administered by the U.S. Department of Energy. The Government has certain rights in this invention. [Background technology]

[0002] 2. Background of the Invention In recent years, we have been in the midst of another intensifying epidemic of waste plastic pollution, one that is set to grow exponentially over time unless there is a fundamental shift in the definition of recycling. Global production of man-made plastics currently exceeds 330 million tons per year, and plastic waste production is expected to grow at an estimated 3.9% per year. (Fivga, A. & Dimitriou, I. Energy 149, 865-874 2018). Given the current rate of production and use of plastics, it is estimated that there will be approximately 12 trillion tons of plastic waste requiring disposal by 2050. (Geyer, R., Jambeck, JR & Law, KL Sci. Adv. 3, 2017).

[0003] Currently, the majority of plastics are landfilled or incinerated, with only a small percentage being recycled. (Chen, X., Wang, Y. & Zhang, L. ChemSusChem 14, 4137-4151 2021). Landfilling is not sustainable at the current rate of plastic waste generation, and no energy or useful products can be extracted from this feedstock. Incineration is a very inefficient method of energy extraction that causes pollution and produces carbon dioxide, which can exacerbate climate change.

[0004] Plastic recycling is only available for some thermoplastics, mainly the polyolefins polyethylene and polypropylene. (Chen, X., Wang, Y. & Zhang, L. ChemSusChem 14, 4137-4151 2021;Solis, M. & Silveira, S. Waste Manag. 105, 128-138, 2020). However, recycling thermoplastics leads to a loss of strength and elasticity, resulting in downcycling of products that are more costly to produce than virgin plastics. (Ibid.).

[0005] Due to the limitations of current recycling methods, research has turned to plastic upcycling technologies. Plastic upcycling strategies broadly fall into one of two categories: (1) thermochemical decomposition, which produces gases and / or petroleum-like oils, or (2) polymer decomposition, which produces monomers that then undergo polymerization to produce plastics with similar mechanical and structural properties as virgin plastics. Most thermochemical decomposition methods are classified as either pyrolysis or gasification techniques. (Nanda, S. & Berruti, F. Environ. Chem. Lett. 2020 191 19, 123-148 2020).

[0006] Pyrolysis techniques generally have higher conversion efficiencies and lower costs compared to gasification, but the choice depends on what the desired products are. Hydrocarbons are produced in both pyrolysis and gasification techniques and can then be used to synthesize a wide range of desired chemicals and fuels.

[0007] Microwave (MW)-assisted thermocatalytic decomposition of plastics is much more energy efficient than current thermal and thermocatalytic technologies. However, to date, MW-assisted thermocatalytic decomposition has only been used to produce pyrolysis oils.

[0008] MW-assisted thermal catalysis has been applied to produce hydrogen and carbon from plastics, achieving approximately 90% yield of H2. (Jie, X. et al., "Microwave-initiated catalytic deconstruction of plastic waste into hydrogen and high-value carbons", Nat Catal 3, 902-912, 2020). However, this method relies on continuous re-decomposition of liquids and gases under high MW power to achieve these yields. These conditions require high energy consumption, thus preventing economical scaling. Moreover, it is a batch process, requiring long processing times.

[0009] In view of the above, there is a need to reduce the amount of waste plastic worldwide.

[0010] Citation of any reference in this section should not be construed as an admission that such reference is prior art to the present disclosure. Summary of the Invention

[0011] 2. Overview of this Disclosure The present disclosure provides methods and apparatus to achieve an economically viable, commercially scalable, and sustainable recycling solution for plastics and other waste materials via catalytic thermochemical decomposition of waste plastics into the clean fuel hydrogen (H2) by microwave exposure.

[0012] Advantageously, the disclosed method and apparatus can recycle a wide range of waste plastics, including those that are currently not available as post-consumer products due to pre-processing challenges such as sanitation and contaminants. In the disclosed method, mixed waste plastics become a feedstock for making hydrogen. A hydrogen energy society has been hampered for decades by the cost and inefficiency of its production, which requires an energy-intensive multi-step process. The disclosed method can significantly reduce the energy cost of making hydrogen fuel, while at the same time converting plastic waste into a valuable product rather than a costly by-product for cleanup.

[0013] The disclosed method uses high temperature non-oxidative reactions under microwaves. Under the reaction conditions described herein, the disclosed method produces mainly hydrogen and solid carbon, while producing negligible amounts of carbon monoxide (CO) and carbon dioxide (CO2). In addition, the reaction conditions described herein prevent the pyrolysis of plastics, which maximizes hydrogen recovery from waste while minimizing liquid yield. The catalyst is also abundant on earth and can be recycled and reused by the system.

[0014] Thus, in one embodiment, the present disclosure provides a method for producing hydrogen. The method includes: (a) contacting a plastic with a catalyst and a gas feed; and (b) applying microwaves to heat the catalyst to a first temperature. In some aspects, the method includes: (a) contacting a plastic with a catalyst and a gas feed; and (b) applying microwaves to heat the catalyst to a first temperature in the range of about 500° C. to about 2000° C., thereby producing hydrogen.

[0015] In a second embodiment, the present disclosure provides an apparatus for producing hydrogen, the apparatus comprising: a reactor for mixing a plastic with a catalyst to form a mixture; an inlet for introducing a gas feed; a microwave generator; an optional temperature sensor; and an outlet configured to exhaust product hydrogen formed in the reactor. [Brief description of the drawings]

[0016] [Figure 1] 1 is a flow chart illustrating steps of a method for producing hydrogen according to an embodiment of the present disclosure. [Diagram 2] FIG. 1 is a schematic diagram illustrating an apparatus for producing hydrogen according to an embodiment of the present disclosure. [Diagram 3] FIG. 1 is a schematic diagram illustrating an apparatus for producing hydrogen according to an embodiment of the present disclosure. [Figure 4] FIG. 1 is a schematic diagram illustrating a reactor according to an embodiment of the present disclosure. [Diagram 5] FIG. 1 illustrates the evaluation of different catalysts for converting mixed plastic waste to hydrogen. The measured data includes the percent yields of carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), methane (CH4), and ethylene (C2H4) for each tested catalyst. [Figure 6] FIG. 1 shows an evaluation of various different catalysts for converting mixed plastic waste to hydrogen. The measured data includes the combined char, tar and gas yields for each tested catalyst. [Figure 7] FIG. 1 illustrates an evaluation of various catalysts for converting mixed plastic waste to hydrogen. The measured data includes absorbed energy utilization for each tested catalyst. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] 4. Detailed Description The present invention includes the following: (1.) A method for producing hydrogen, comprising: (a) contacting a plastic with a catalyst and a gas feed; and (b) applying microwaves to heat the catalyst to a first temperature. (2.) The method according to (1) above, wherein the first temperature is in the range of about 200°C to about 1200°C. (3.) The method according to (1.) or (2.) above, wherein the first temperature is in the range of about 500°C to about 900°C. (4.) The method according to any one of (1.) to (3.) above, wherein the first temperature is in the range of about 700°C to about 800°C. (5.) The method according to (1.) to (4.) above, wherein the microwaves are applied at a frequency in the range of about 100 MHz to about 8 GHz. (6.) The method according to (1.) to (4.) above, wherein the microwaves are applied at a frequency in the range of about 1 gigahertz to about 8 GHz. (7.) The method according to (1.) to (4.) above, wherein the microwaves are applied at a frequency of about 2.45 GHz. (8.) The method according to (1.) to (4.) above, wherein the microwaves are applied at a frequency of about 915 MHz. (9.) The method of (1.) to (8.) above, wherein the microwaves are applied for a duration in the range of about 20 seconds to about 120 seconds. (10.) The method according to any one of (1.) to (9.) above, wherein the pressure in step (a) is in the range of about 0 psi to about 500 psi. (11.) The method according to any one of (1.) to (10.) above, wherein the pressure in step (b) is in the range of about 0 psi to about 500 psi. (12.) The method according to any one of (1.) to (11.) above, wherein the plastic is selected from the group consisting of polypropylene (PP), polycarbonate (PC), polystyrene (PS), polyethylene (PE) (e.g., low-density polyethylene (LDPE) and high-density polyethylene (HDPE)), polyvinyl chloride (PVC), acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET), nylon, and polyamide, as well as combinations thereof. (13.) The method according to any one of (1.) to (11.) above, wherein the plastic is mixed plastic waste. (14.) The method according to (1.) to (13.) above, wherein the catalyst is an Earth-abundant catalyst. (15.) The method according to any one of (1.) to (13.) above, wherein the catalyst is an oxide of a metal selected from the group consisting of Ni, Co, Fe, Cu, Ce, Zr, Al, Pt, Pd, Rh, Ru, Si and Mg, and combinations thereof. (16.) The method according to any one of (1.) to (13.) above, wherein the catalyst is an oxide of a metal selected from the group consisting of Ni, Co, Fe, Cu, Ce, Zr and Al, and combinations thereof. (17.) The method according to any one of (1.) to (13.) above, wherein the oxide is an oxide of a metal selected from the group consisting of Pt, Pd, Rh, and Ru, and combinations thereof. (18.) The method according to (17.) above, further comprising supporting an oxide selected from the group consisting of SiO2, MgO, and ZrO2. (19.) The process according to any one of (1.) to (13) above, wherein the catalyst is selected from iron oxide, supported iron, supported nickel, carbon, and iron carbide, and combinations thereof. (20.) The method according to any one of (1.) to (19.) above, wherein the gas supply comprises a gas selected from the group consisting of nitrogen, argon, water vapor, carbon dioxide, and air, and combinations thereof. (21.) The method according to any one of (1.) to (20.) above, wherein the gas supply comprises a gas selected from nitrogen, argon, and helium, and combinations thereof. (22.) The method according to (1.) to (21.) above, wherein step (a) includes a substep of pretreating plastic. (23.) The method according to (22.) above, wherein the pretreatment step comprises applying microwaves at a second temperature. (24.) The method according to (23.) above, wherein step (a) further comprises the substep of removing waste materials from the pretreated plastic. (25.) The method according to (1.) or (24.) above, wherein step (a) includes the substep of crushing the plastic. (26.) The method according to any one of (1.) to (25.) above, further comprising a step (c) of removing hydrogen produced in step (b). (27.) An apparatus for producing hydrogen comprising: a reactor for mixing a plastic with a catalyst to form a mixture; an inlet for introducing a gas feed; a microwave generator; an optional temperature sensor; and an outlet configured to exhaust product hydrogen formed in the reactor. (28.) The apparatus of (27.) further comprising a gas storage vessel. (29.) The apparatus according to (27.) or (28.), further comprising a vessel for separating the produced hydrogen from by-products. (30.) A method for producing hydrogen, comprising: (a) contacting a plastic with a catalyst and a gas feed; and (b) applying microwaves to heat the catalyst to a first temperature in the range of about 500° C. to about 2000° C.; thereby producing hydrogen. (31.) The method according to (30.) above, wherein the first temperature is in the range of about 500°C to about 900°C. (32.) The method according to (30.) or (31.), wherein the microwaves are applied at a frequency in the range of about 100 MHz to about 8 GHz. (33.) The method according to (30.) to (32.) above, wherein microwaves are applied at a frequency of about 2.45 GHz. (34.) The method according to (30.) to (33.) above, in which microwaves are applied continuously. (35.) The method according to (30.) to (34.) above, wherein the plastic is treated for a period ranging from 30 seconds to 10 minutes. (36.) The method according to (30.) to (35.) above, wherein the pressure in step (a) is in the range of about 0 psi to about 500 psi. (37.) The method according to any one of (30.) to (36.) above, wherein the pressure in step (b) is in the range of about 0 psi to about 500 psi. (38.) The method according to any one of (30.) to (37.) above, wherein the plastic is selected from the group consisting of polypropylene (PP), polycarbonate (PC), polystyrene (PS), polyethylene (PE), polyvinyl chloride (PVC), acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET), nylon, and polyamide, as well as combinations thereof. (39.) The method according to (30.) to (38.) above, wherein the plastic is mixed plastic waste. (40.) The method according to any one of (30.) to (39.) above, wherein the catalyst comprises an oxide of a metal selected from the group consisting of Ni, Co, Fe, Cu, Ce, Zr, Al, Si and Mg, and combinations thereof. (41.) The method according to (30.) to (40.) above, further comprising supporting an oxide selected from the group consisting of SiO2, MgO, and ZrO2. (42.) The method according to any one of (30.) to (39.) above, wherein the catalyst is an oxide of a metal selected from the group consisting of Mn, Fe, Co, Ni, Cu, Ti, V, Cr, Zr, Nb and W, and combinations thereof. (43.) The method according to any one of (30.) to (39.) above, wherein the catalyst is selected from iron oxide, supported iron, supported nickel, carbon, and iron carbide, and combinations thereof. (44.) The method according to any one of (30.) to (39.) above, wherein the catalyst contains magnetite. (45.) The method according to any one of (30.) to (44.) above, wherein the gas supply comprises a gas selected from the group consisting of nitrogen, argon, and combinations thereof. (46.) The method according to (30.) to (45.) above, wherein step (a) includes contacting a plastic with a porous medium. (47.) The method according to (46.) above, wherein the porous medium comprises a material selected from the group consisting of silica, alumina, zeolite, and dolomite, and combinations thereof. (48.) The method according to any one of (30.) to (47.) above, further comprising a step (c) of removing hydrogen produced in step (b). (49.) An apparatus for producing hydrogen, comprising: a reactor for producing hydrogen; an inlet for introducing a gas feed; a microwave generator; an optional temperature sensor; and an outlet configured to vent product hydrogen formed in the reactor. (50.) The apparatus according to (49.) above, wherein the reactor is a two-stage reactor. (51.) The apparatus according to (49.) or (50.), further comprising a fluidized bed. (52.) The apparatus according to (49.) to (51.) above, further comprising an inlet for introducing a catalyst. (53.) The apparatus according to (49.) to (52.) above, further comprising an inlet for introducing plastic. (54.) The apparatus according to (49.) to (53.) above, further comprising inlets for introducing plastic and catalyst. (55.) The apparatus according to (49.) to (54.) above, further comprising a gas storage vessel. (56.) The apparatus according to any one of (49.) to (55.) above, further comprising a vessel for separating the produced hydrogen from by-products.

[0018] 4.1 Definition Unless expressly indicated otherwise, the following terms used herein have the meanings indicated below.

[0019] Throughout this specification, the word "comprise" or variations such as "comprises" or "comprising" are understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers.

[0020] The terms "a" or "an" may refer to more than one item.

[0021] The terms "and" and "or" can refer to either the conjunctive or disjunctive, meaning "and / or."

[0022] The term "about" means within plus or minus 10% of the stated value. For example, "about 100" refers to any number between 90 and 110.

[0023] The term "effective amount" of catalyst refers to an amount of catalyst sufficient to achieve a desired level of waste plastic conversion and / or a desired product selectivity. The specified amount of catalyst in weight percent in the reaction mixture required as an "effective amount" depends on a variety of factors, including the particular catalyst selected, catalyst particle size, amount and type of plastic, plastic particle size, amount and type of porous media, microwave power, reaction temperature and pressure, and the desired products.

[0024] The term "plastic feedstock" refers to any raw plastic material used in the methods of the present disclosure. The plastic feedstock may be fractionated or unfractionated and / or cleaned or uncleaned plastic material.

[0025] The term "feedstock heterogeneity" refers to the heterogeneity of the plastic mixture used in the methods of the present disclosure. That is, feedstock heterogeneity refers to the similarity or dissimilarity of the plastic materials in the plastic feedstock.

[0026] The term "substantially pure plastic feedstock" refers to a plastic feedstock having a purity of greater than about 75%. In some embodiments, the purity is greater than 80%. In some embodiments, the purity is greater than 85%. In some embodiments, the purity is greater than 85%. In some embodiments, the purity is greater than 90%. In some embodiments, the purity is greater than 95%. In some embodiments, the purity is greater than 96%. In some embodiments, the purity is greater than 97%. In some embodiments, the purity is greater than 98%. In some embodiments, the purity is greater than 99%.

[0027] The term "mixed plastic waste" refers to unsorted and / or uncleaned plastic waste from hospitals, industrial facilities, recycling plants, oceans or canals, residential, and retail outlets, among others, including municipal solid waste. Exemplary mixed plastic waste includes, but is not limited to, plastic and styrofoam packaging, plastic bottles, plastic trays, plastic furniture, electronic shells, plastic pipes, fishing nets, and plastic crates.

[0028] The term "municipal solid waste" refers to waste collected by a municipality or disposed of at a municipal dump, and includes household waste, industrial waste, institutional waste, commercial waste, municipal solid waste, construction and demolition waste.

[0029] The term "pyrolysis" in relation to plastics refers to the thermochemical decomposition of plastics under inert gas to produce liquids (e.g., pyrolysis oils) as the primary product.

[0030] The term "gasification" in relation to plastics refers to the decomposition of plastics, which occurs at higher temperatures in the presence of oxygen to produce primarily gases, which are called "synthesis gas or syngas." "Syngas" refers to a mixture of gases, primarily H2 and CO, with smaller amounts of nitrogen (N2), CO2, methane (CH4), and water vapor (H2O).

[0031] The term "microwave heating" refers to a method of heating a material by application of microwaves, in which the material is heated in the absence of a plasma and no sustained non-thermal or thermal plasma is intentionally generated.

[0032] The term "first temperature" refers to the temperature of the catalyst used in the method of the present disclosure. In one variation, the term "first temperature" refers to the temperature of both the catalyst and the porous material used in the method of the present disclosure. The term "first temperature" also refers to the reaction temperature.

[0033] The term "second temperature" refers to the temperature during a secondary processing step, either before or after the method for producing hydrogen of the present disclosure. In one embodiment, the second temperature refers to the temperature during a pre-processing step. In another embodiment, the second temperature refers to the temperature during a post-processing step.

[0034] The term "Earth-abundant catalyst" refers to catalysts that contain earth-abundant transition metals, such as Mn, Fe, Co, Ni, Cu, Ti, V, Cr, Zr, Nb, and W. Examples of earth-abundant catalysts include magnetite and bauxite.

[0035] The term "designer catalyst" refers to a catalyst that does not exist in nature or must be synthesized and can be used to convert plastics to hydrogen. Examples of designer catalysts include, but are not limited to, FeAlO x , FeMgO, FeZSM-5, NiAl2O3, and FeAl2O3.

[0036] The term "unstructured catalyst" refers to a catalyst that is not formed into a particular shape, such as a monolith. Unstructured catalysts can be used to increase the surface area of ​​the catalyst.

[0037] The term "supported" catalyst refers to any material capable of supporting catalytically active sites. Exemplary supports for catalysts used in the methods of the present disclosure include, but are not limited to, polymers, silica (SiO2), alumina (Al2O3), olivine, zirconium oxide (ZrO2), titanium oxide (TiO2), cesium oxide (CeO2), and magnesium oxide (MgO), and combinations thereof.

[0038] The term "substantially solvent-starved" refers to reaction conditions where the reaction mixture contains less than 1% solvent by weight. In some embodiments, the reaction mixture contains less than 0.5% solvent by weight. In some embodiments, the reaction mixture contains less than 0.25% solvent by weight. In some embodiments, the reaction mixture contains less than 0.1% solvent by weight. In some embodiments, the reaction mixture contains less than 0.05% solvent by weight.

[0039] The term "low dielectric metal oxide" refers to a metal oxide having a low dielectric constant (κ, kappa). Examples of low dielectric metal oxides are metal oxides with a loss tangent in the range of 0 to about 0.5. Other examples are materials classified as insulators or semiconductors.

[0040] The term "batch process" for producing hydrogen refers to a method of producing hydrogen where all reagents are reacted in a vessel under suitable reaction conditions for a suitable length of time and converted to products. The method is terminated and the reaction mixture including the products is collected. After the method is started, no more reactants are added to the reaction vessel and no more products are removed until the method is terminated.

[0041] The term "continuous process" for producing hydrogen refers to a method of producing hydrogen in which additional reagents may be added to the vessel and product may be removed during the course of the process without terminating the process.

[0042] The term "semi-continuous process" for producing hydrogen refers to a process that is neither a batch nor a continuous process, during which reagents are added periodically and product is removed periodically.

[0043] The term "treatment time" refers to the amount of time that plastic is converted to hydrogen when in contact with the catalyst.

[0044] In order to provide a thorough understanding of the invention described herein, the following detailed description is set forth.

[0045] 4.2 How to produce hydrogen The present disclosure provides a method for producing hydrogen. The method includes: (a) contacting a plastic with a catalyst and a gas feed; and (b) applying microwaves to heat the catalyst to a first temperature. In some embodiments, the method includes: (a) contacting a plastic with a catalyst and a gas feed; and (b) applying microwaves to heat the catalyst to a first temperature in a range of about 500° C. to about 2000° C., thereby producing hydrogen.

[0046] Step (a) includes contacting plastics with a catalyst and a gas feed. The plastics used in step (a) are mixed plastic waste in the first embodiment. In some aspects of this embodiment, the mixed plastics are from hospitals. In other aspects, the mixed plastics are from oceans or canals.

[0047] The plastic used in step (a) in the second embodiment is selected from the group consisting of polypropylene (PP), polycarbonate (PC), polystyrene (PS), polyethylene (PE) (e.g., low density polyethylene (LDPE) and high density polyethylene (HDPE)), polyvinyl chloride (PVC), acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET), nylon, and polyamide, and combinations thereof. In some aspects of this embodiment, the plastic is one or more materials selected from the group consisting of HDPE, PP, PET, PS, and LDPE. In some aspects of this embodiment, the plastic is two or more materials selected from the group consisting of HDPE, PP, PET, PS, and LDPE. In some aspects of this embodiment, the plastic is three or more materials selected from the group consisting of HDPE, PP, PET, PS, and LDPE. In some aspects of this embodiment, the plastic is four or more materials selected from the group consisting of HDPE, PP, PET, PS, and LDPE. In some embodiments, the plastic used in step (a) is a combination of HDPE, PP, PET, PS, and LDPE.

[0048] The plastics used in step (a) can be unsorted, sorted, treated or untreated. Methods for treating plastics are described below.

[0049] In another aspect of this embodiment, the plastic used in step (a) may be shredded, ground, pelletized, beaded, or otherwise modified in size or form from its original form as mixed plastic waste.

[0050] The catalyst used in step (a) may include any catalyst that converts plastics to hydrogen, including earth-abundant catalysts and designer catalysts. In one embodiment, the catalyst is an earth-abundant catalyst. In one aspect of this embodiment, the earth-abundant catalyst is an unstructured catalyst. In another aspect, the earth-abundant catalyst is a structured catalyst. In one embodiment, the catalyst is an earth-abundant transition metal-containing catalyst, such as Mn, Fe, Co, Ni, Cu, Ti, V, Cr, Zr, Nb, and W.

[0051] In another embodiment, the catalyst is an oxide of a metal selected from the group consisting of Ni, Co, Fe, Cu, Ce, Zr, Al, Pt, Pd, Rh, Ru, Si, and Mg, and combinations thereof. In some embodiments, the catalyst is an oxide of a metal selected from the group consisting of Ni, Co, Fe, Cu, Ce, Zr, Al, Si, and Mg, and combinations thereof. In some embodiments, the catalyst is an oxide of a metal selected from the group consisting of Ni, Co, Fe, Cu, Ce, Zr, and Al, and combinations thereof. In other embodiments, the catalyst is an oxide of a metal selected from the group consisting of Pt, Pd, Rh, and Ru, and combinations thereof. In still other embodiments, the catalyst is selected from iron oxide, supported iron, supported nickel, carbon, and iron carbide, and combinations thereof.

[0052] In another embodiment, the catalyst comprises iron. In some aspects of this embodiment, the catalyst is selected from magnetite, bauxite, bauxite residue (also known as "red mud"), Fe, Fe3C, FeO, Fe2O3, Fe3O4, and combinations thereof. In some aspects of this embodiment, the iron-containing catalyst may be recovered from the previous methods of the present disclosure, recycled, and used again. Recycling and reusing the catalyst advantageously reduces the mining and processing of natural resources, and reduces material and operating costs.

[0053] In various embodiments, the method further comprises a natural mineral catalyst, such as dolomite or olivine. In other embodiments, the method further comprises supporting an oxide selected from the group consisting of SiO2, MgO, and ZrO2.

[0054] In one embodiment of the disclosed method, the catalyst comprises Ni / Al2O3 and / or Ni-Mg-Al. In some aspects of this embodiment, the method further comprises using one or more natural mineral catalysts, such as dolomite or olivine.

[0055] In another embodiment of the method of the present disclosure, the catalyst comprises a compound selected from the group consisting of Al(NO3)39H2O, Ce(NO3)36H2O, ZrO(NO3)2xH2O, NH4HCO3, and Ni(NO3)26H2O.

[0056] In another embodiment of the method of the present disclosure, the catalyst is not NiFe2O4. In another embodiment, the catalyst is not nanosized NiFe2O4. In another embodiment, the catalyst is not nanosized NiFe2O4 prepared by a sol-gel method.

[0057] In another embodiment, the catalyst is not Ti3AlC2.

[0058] It should be understood that the particle size and surface area of ​​any particulate catalyst will depend on a variety of factors, including the type of catalyst, the amount of catalyst used, the catalyst to plastic ratio, the presence of porous media, the ratio of porous media to plastic feedstock, reaction conditions, temperature, gas flow rates, and equipment design.

[0059] The amount of catalyst used in step (a) is an effective amount. In some embodiments, the catalyst is present in an amount ranging from about 20 wt% to about 50 wt%, about 25 wt% to about 45 wt%, about 30 wt% to about 40 wt%, about 20 to about 45 wt%, about 20 wt% to about 40 wt%, about 20 wt% to about 35 wt%, about 20 wt% to about 30 wt%, about 25 wt% to about 50 wt%, about 30 wt% to about 50 wt%, about 35 wt% to about 50 wt%, or about 40 wt% to about 50 wt%. In certain embodiments, the catalyst is present in an amount of about 20 wt%, about 25 wt%, about 30 wt%, about 35 wt%, about 40 wt%, about 45 wt%, or about 50 wt%.

[0060] In embodiments of the methods of the present disclosure, the catalyst to plastic ratio ranges from about 1:9 to about 3:4. In some embodiments, the catalyst to plastic ratio ranges from about 1:4 to about 3:4. In some embodiments, the catalyst to plastic ratio ranges from about 1:3 to about 3:1. In some embodiments, the catalyst to plastic ratio is about 1:1, about 1:2, about 1:3, about 1:4, about 1:5, about 1:6, about 1:7, about 1:8, about 1:9, or about 1:10. In some embodiments, the catalyst to plastic ratio is about 1:1.

[0061] The gas feed used in step (a) comprises a gas selected from the group consisting of nitrogen, argon, helium, water vapor, carbon dioxide, and air, and combinations thereof. In some embodiments, the gas feed used in step (a) comprises a gas selected from the group consisting of nitrogen, argon, water vapor, carbon dioxide, and air, and combinations thereof. In some embodiments, the gas feed used in step (a) comprises a gas selected from the group consisting of nitrogen, argon, and helium, and combinations thereof. In some embodiments, the gas feed used in step (a) is obtained according to the previous method of the present disclosure and comprises recycled hydrocarbons. The gas used in step (a) can be referred to as a "fluidizing gas". The gas used in step (a) is not heated (substantially at room temperature).

[0062] It should be understood that the flow rate of the gas feed used in step (a) will depend on a variety of factors including the type of catalyst, the particle size of the catalyst used, the uniformity of the particle size of the catalyst used, the mass of catalyst used, the size and density of the plastic used, the ratio of catalyst to plastic feed, the size of the reactor, and the reaction conditions.

[0063] The flow rate of the gas used in step (a) can range from about 10 SCCM to about 1000 SCCM (standard cubic centimeters per minute). In some embodiments, the gas flow rate is from about 20 SCCM to about 1000 SCCM, from about 30 SCCM to about 1000 SCCM, from about 40 SCCM to about 1000 SCCM, from about 50 SCCM to about 1000 SCCM, from about 60 SCCM to about 1000 SCCM, from about 70 SCCM to about 1000 SCCM, from about 80 SCCM to about 1000 SCCM, from about 90 SCCM to about 1000 SCCM, from about 100 SCCM to about 1000 SCCM, from about 150 SCCM to about 1000 SCCM, or from about The viscosity may be in the range of 200 SCCM to about 1000 SCCM, about 250 SCCM to about 1000 SCCM, about 300 SCCM to about 1000 SCCM, about 350 SCCM to about 1000 SCCM, about 400 SCCM to about 1000 SCCM, about 500 SCCM to about 1000 SCCM, about 600 SCCM to about 1000 SCCM, about 700 SCCM to about 1000 SCCM, about 800 SCCM to about 1000 SCCM, or about 900 SCCM to about 1000 SCCM. In some embodiments, the gas flow rate can range from about 10 SCCM to about 900 SCCM, from about 10 SCCM to about 800 SCCM, from about 10 SCCM to about 700 SCCM, from about 10 SCCM to about 600 SCCM, from about 10 SCCM to about 500 SCCM, from about 10 SCCM to about 450 SCCM, from about 10 SCCM to about 400 SCCM, from about 10 SCCM to about 350 SCCM, from about 10 SCCM to about 300 SCCM, from about 10 SCCM to about 250 SCCM, from about 10 SCCM to about 200 SCCM, from about 10 SCCM to about 150 SCCM, or from about 10 SCCM to about 100 SCCM.In some embodiments, the gas flow rate can be about 10 SCCM, about 20 SCCM, about 30 SCCM, about 40 SCCM, about 50 SCCM, about 60 SCCM, about 70 SCCM, about 80 SCCM, about 90 SCCM, about 100 SCCM, about 125 SCCM, about 150 SCCM, about 175 SCCM, about 200 SCCM, about 225 SCCM, about 250 SCCM, about 275 SCCM, about 300 SCCM, about 325 SCCM, about 350 SCCM, about 375 SCCM, about 400 SCCM, about 425 SCCM, about 450 SCCM, about 475 SCCM, about 500 SCCM, about 525 SCCM, about 550 SCCM, about 575 SCCM, about 600 SCCM, about 625 SCCM, about 650 SCCM, or about 675 SCCM.

[0064] When the size of the reactor is increased, for example to one suitable for an industrial process, the flow rate is increased to be sufficient to fluidize the catalyst bed.

[0065] The gas flow in step (a) is continuous or substantially continuous. Substantially continuous flow means that the gas flows for a period of time during the course of step (a) and may be temporarily shut off during that period, as opposed to purging, in which gas is flowed briefly as a means of removing undesirable gases, moisture and other impurities.

[0066] In some embodiments, step (a) comprises mechanically mixing the catalyst with the plastic and porous media, if present, hi other embodiments, step (a) comprises applying a solution comprising the catalyst onto the plastic and porous media, if present, to form a mixture, and optionally drying the mixture.

[0067] In some embodiments, step (a) further comprises a solvent, hi other embodiments, step (a) is substantially devoid of solvent.

[0068] In some embodiments, step (a) further comprises contacting the plastic with a porous medium. The porous medium used in step (a) is a material that is inert to the microwaves applied in step (b) or inert to microwave absorption. Examples of porous media that can be used in step (a) include low dielectric oxides (e.g., alumina, silica, zeolites, dolomite), and high surface area porous mineral-based materials.

[0069] In embodiments where the porous medium is a low dielectric oxide, the dielectric constant is in the range of about 0.5 to about 10. In some aspects of this embodiment, the dielectric constant of the porous medium is in the range of about 0.5 to about 9, about 0.5 to about 8, about 0.5 to about 7, about 0.5 to about 6, about 0.5 to about 5, about 0.5 to about 4, about 0.5 to about 3, about 0.5 to about 2, about 0.5 to about 1, about 1 to about 10, about 1.5 to about 10, about 2 to about 10, about 2.5 to about 10, about 3 to about 10, about 3.5 to about 10, about 4 to about 10, about 4.5 to about 10, about 5 to about 10, about 5.5 to about 10, about 6 to about 10, about 6.5 to about 10, about 7 to about 10, about 7.5 to about 10, about 8 to about 10, about 8.5 to about 10, about 9 to about 10, or about 9.5 to about 10.

[0070] High surface area porous materials have a surface area of ​​approximately 10 m 2 / g~about 1000m 2 / g and a pore size ranging from about 10 nm to about 50 nm. In some embodiments, the porous media comprises a material selected from the group consisting of silica, alumina, and zeolites, and combinations thereof.

[0071] In some aspects of this embodiment, the particular porous medium is about 10 m 2 / g ~ approx. 900m 2 / g, approx. 10m 2 / g~about 800m 2 / g, approx. 10m 2 / g~about 700m 2 / g, approx. 10m 2 / g~about 600m 2 / g, approx. 10m 2 / g~about 500m 2 / g, approx. 10m2 / g~about 400m 2 / g, approx. 10m 2 / g~about 300m 2 / g, approx. 10m 2 / g~about 200m 2 / g, approx. 10m 2 / g~about 100m 2 / g, approx. 50m 2 / g ~ approx. 900m 2 / g, about 100m 2 / g ~ approx. 900m 2 / g, approx. 150m 2 / g ~ approx. 900m 2 / g, approx. 200m 2 / g ~ approx. 900m 2 / g, approx. 250m 2 / g ~ approx. 900m 2 / g, approx. 300m 2 / g ~ approx. 900m 2 / g, approx. 350m 2 / g ~ approx. 900m 2 / g, approx. 400m 2 / g ~ approx. 900m 2 / g, approx. 450m 2 / g ~ approx. 900m 2 / g, approx. 500m 2 / g ~ approx. 900m 2 / g, approx. 600m 2 / g ~ approx. 900m 2 / g, approx. 700m 2 / g ~ approx. 900m 2 / g, or approximately 800m 2 / g ~ approx. 900m 2 / g range of surface area.

[0072] In some aspects of this embodiment where a porous medium is present, the particular porous medium has a pore size in the range of about 10 nm to about 40 nm, about 10 nm to about 30 nm, about 10 nm to about 20 nm, about 20 nm to about 50 nm, about 30 nm to about 50 nm, or about 40 nm to about 50 nm.

[0073] In some aspects of this embodiment where a porous medium is present, the particular porous medium is about 100 m 2 / g and pore size greater than about 10 nm,2 / g surface area and pore size greater than about 10 nm, 2 / g surface area and pore size greater than about 10 nm, 2 / g surface area and pore size greater than about 10 nm, 2 / g surface area and pore size of about 10 nm, about 600 m 2 / g surface area and pore size greater than about 10 nm, 2 / g surface area and pore size greater than about 10 nm, 2 / g surface area and pore size greater than about 10 nm, 2 / g surface area and pore size greater than about 10 nm, 2 / g surface area and pore size greater than about 10 nm, 2 / g surface area and pore size of about 20 nm, about 100 m 2 / g surface area and pore size of about 30 nm, about 100 m 2 / g surface area and a pore size of about 40 nm, or about 100 m 2 / g surface area and a pore size of approximately 50 nm.

[0074] In embodiments of the disclosed method, the ratio of porous media to plastic feedstock is about 1:1, about 1:2, about 1:3, about 1:4, about 1:5, about 1:6, about 1:7, about 1:8, about 1:9, or about 1:10.

[0075] In embodiments of the disclosed method, the ratio of porous media to catalyst is about 1:1, about 1:2, about 1:3, about 1:4, about 1:5, about 1:6, about 1:7, about 1:8, about 1:9, or about 1:10.

[0076] It should be understood that the porosity and surface area of ​​any particular porous media will depend on a variety of factors, including the type of porous media used, the reaction conditions, the size and density of the plastic feedstock, and the heterogeneity of the feedstock.

[0077] The pressure in step (a) ranges from about 0 psi to about 500 psi. In some embodiments, the pressure in step (a) ranges from about 100 psi to about 400 psi. In some embodiments, the pressure in step (a) ranges from about 200 psi to about 300 psi. In some embodiments, the pressure in step (a) is about 0 psi, about 50 psi, about 100 psi, about 150 psi, about 200 psi, about 250 psi, about 300 psi, about 400 psi, about 450 psi, or about 500 psi.

[0078] The contacting step (a) can occur in a fixed bed or a fluidized bed. In embodiments where the contacting step is in a fixed bed, the fixed bed comprises two layers. The first layer comprises the plastic and the porous media, if present, and the second layer is located on top of the first layer and comprises the catalyst.

[0079] In embodiments where the contacting step is in a fluidized bed, the plastic and porous media, if present, are fluidized with a catalyst. In this embodiment, as the catalyst is heated, it transfers heat to the plastic. The fluidized bed can be upflow, circulating, or bubbling.

[0080] In some embodiments, step (a) includes sub-step (i) of placing the porous media and plastic in a fluidized bed, which can be upflow, circulating, or bubbling.

[0081] In some embodiments, step (a) includes substep (i) of contacting a plastic with a catalyst and, if present, a porous medium to form a mixture, and substep (ii) of introducing the mixture into a reactor.

[0082] In some embodiments, step (a) includes substep (i) of introducing the plastic into a mixture of the catalyst and, if present, the porous medium. The catalyst and, if present, the porous medium may be on a fluidized bed. The fluidized bed may be upflow, circulating, or bubbling.

[0083] Step (b) of the method of the present disclosure includes applying microwaves to heat the catalyst to a first temperature. The applied microwaves are sufficient to provide microwave heating of the catalyst in one embodiment, and of a mixture of both the catalyst and the porous media in another embodiment.

[0084] In various embodiments, microwaves are applied at a frequency ranging from about 100 MHz to about 8 GHz, in some embodiments, microwaves are applied at a frequency ranging from about 1 GHz to about 8 GHz, from about 1 GHz to about 7 GHz, from about 1 GHz to about 6 GHz, from about 1 GHz to about 5 GHz, from about 1 GHz to about 4 GHz, or from about 1 GHz to about 3 GHz. In some embodiments, microwaves are applied at a frequency in the range of about 100 MHz to about 3 GHz, about 200 MHz to about 3 GHz, about 300 MHz to about 3 GHz, about 400 MHz to about 3 GHz, about 500 MHz to about 3 GHz, about 600 MHz to about 3 GHz, about 700 MHz to about 3 GHz, about 800 MHz to about 3 GHz, about 900 MHz to about 3 GHz, about 900 MHz to about 2.5 GHz, about 900 MHz to about 2 GHz, about 900 MHz to about 1.5 GHz, or about 900 MHz to about 1 GHz. In some embodiments, microwaves are applied at a frequency of about 2.45 GHz. In other embodiments, microwaves are applied at a frequency of about 915 MHz.

[0085] The microwaves are applied for a time ranging from about 20 seconds to about 120 seconds. In some embodiments, the microwaves are applied for a time ranging from about 20 seconds to about 110 seconds. In some embodiments, the microwaves are applied for a time ranging from about 20 seconds to about 100 seconds. In some embodiments, the microwaves are applied for a time ranging from about 20 seconds to about 90 seconds. In some embodiments, the microwaves are applied for a time ranging from about 30 seconds to about 80 seconds. In some embodiments, the microwaves are applied for a time ranging from about 40 seconds to about 70 seconds. In some embodiments, the microwaves are applied for a time ranging from about 50 seconds to about 60 seconds.

[0086] In one embodiment, the microwaves may be applied under continuous conditions with the power varied to maintain the first temperature, hi another embodiment, the microwaves are pulsed.

[0087] In embodiments where microwaves are applied continuously, the treatment time for the plastic ranges from about 30 seconds to about 20 minutes. In some embodiments, the treatment time ranges from about 1 minute to about 10 minutes, about 2 minutes to about 10 minutes, about 3 minutes to about 10 minutes, about 4 minutes to about 10 minutes, about 5 minutes to about 10 minutes, about 6 minutes to about 10 minutes, about 7 minutes to about 10 minutes, about 8 minutes to about 10 minutes, about 9 minutes to about 10 minutes, about 30 seconds to about 10 minutes, about 30 seconds to about 9 minutes, about 30 seconds to about 8 minutes, about 30 seconds to about 7 minutes, about 30 seconds to about 6 minutes, about 30 seconds to about 5 minutes, about 30 seconds to about 4 minutes, about 30 seconds to about 3 minutes, or about 30 seconds to about 2 minutes. In some embodiments, the treatment time is about 30 seconds, about 1 minute, about 2 minutes, about 3 minutes, about 4 minutes, about 5 minutes, about 6 minutes, about 7 minutes, about 8 minutes, about 9 minutes, about 10 minutes, about 11 minutes, about 12 minutes, about 13 minutes, about 14 minutes, or about 15 minutes.

[0088] The microwave power used in step (b) depends on the scale of the method of the present disclosure (e.g., the amount of catalyst used). For example, if the scale of the method is larger (e.g., industrial scale), the microwave power is higher. Conversely, if the scale of the method is smaller, the microwave power is lower. In some embodiments, the microwave power is about 400W per gram of catalyst used, about 350W per gram of catalyst used, about 300W per gram of catalyst used, about 250W per gram of catalyst used, about 200W per gram of catalyst used, about 150W per gram of catalyst used, or about 100W per gram of catalyst used.

[0089] The first temperature is a temperature in the range of about 200° C. to about 1200° C. In some embodiments, the first temperature is a temperature in the range of about 400° C. to about 1100° C.

[0090] In some embodiments, the first temperature is a temperature in the range of about 600°C to about 1000°C. In some embodiments, the first temperature is a temperature in the range of about 500°C to about 900°C. In some embodiments, the first temperature is a temperature in the range of about 500°C to about 800°C. In some embodiments, the first temperature is a temperature in the range of about 500°C to about 700°C. In some embodiments, the first temperature is a temperature in the range of about 700°C to about 800°C.

[0091] In some embodiments, the first temperature is a temperature in the range of about 500°C to about 2000°C, in the range of about 500°C to about 1900°C, in the range of about 500°C to about 1800°C, in the range of about 500°C to about 1700°C, in the range of about 500°C to about 1600°C, in the range of about 500°C to about 1500°C, in the range of about 500°C to about 1400°C, in the range of about 500°C to about 1300°C, in the range of about 500°C to about 1200°C, in the range of about 500°C to about 1100°C, in the range of about 500°C to about 1000°C, or in the range of about 500°C to about 900°C.

[0092] In some embodiments, the first temperature is a temperature in the range of about 400° C. to about 1100° C., about 400° C. to about 1000° C., about 400° C. to about 900° C., about 400° C. to about 800° C., or about 400° C. to about 700° C. In other embodiments, the first temperature is a temperature in the range of about 450° C. to about 1100° C., about 450° C. to about 1000° C., about 450° C. to about 900° C., about 450° C. to about 800° C., or about 450° C. to about 750° C.

[0093] In certain embodiments, the first temperature is about 450°C, about 475°C, about 500°C, about 525°C, about 550°C, about 575°C, about 600°C, about 625°C, about 650°C, about 675°C, about 700°C, about 725°C, about 750°C, about 775°C, about 800°C, about 825°C, about 850°C, about 875°C, about 900°C, about 925°C, about 950°C, about 1000°C, about 1025°C, The temperature is greater than about 1050°C, about 1075°C, about 1100°C, about 1125°C, about 1150°C, about 1200°C, about 1250°C, about 1300°C, about 1350°C, about 1400°C, about 1450°C, about 1500°C, about 1550°C, about 1600°C, about 1650°C, about 1700°C, about 1750°C, about 1800°C, about 1850°C, about 1900°C, or about 1950°C.

[0094] Without being bound by theory, it is believed that when the first temperature is in the range of about 450°C to about 2000°C, the method of the present disclosure produces greater amounts of hydrogen.

[0095] The pressure in step (b) ranges from about 0 psi to about 500 psi. In some embodiments, the pressure in step (b) ranges from about 100 psi to about 400 psi. In some embodiments, the pressure in step (b) ranges from about 200 psi to about 300 psi. In some embodiments, the pressure in step (a) is about 0 psi, about 50 psi, about 100 psi, about 150 psi, about 200 psi, about 250 psi, about 300 psi, about 400 psi, about 450 psi, or about 500 psi.

[0096] Without being bound by theory, it is believed that the presence of the porous media in step (a) increases the residence time of the plastics in the reactor, which allows for substantially complete decomposition of the plastics, tars and hydrocarbons into hydrogen and carbon.

[0097] It is also believed that the porous media is microwave inert and can be used to control the rate of pyrolysis of plastics, thereby achieving better results.

[0098] The presence of porous media also alters the carbon output, the type of carbon solids produced, and the amount of a particular solid that can be produced.

[0099] Optionally, prior to contacting the plastic with the catalyst and gas feed in step (a), the plastic is (i) pre-treated and / or (ii) ground.

[0100] In another embodiment, in the pre-treating step, the plastic is cleaned or sanitized to remove impurities or waste materials, including organic residues, malodorous components, adhesives, inks, and plastic additives (plasticizers, antioxidants, acid scavengers, light and heat stabilizers, lubricants, pigments, antistatic agents, slip compounds, and thermal stabilizers).

[0101] Methods for pre-treating plastics are known in the art. See, for example, Kol et al., "Recent Advances in Pre-Treatment of Plastic Packaging Waste," August 13, available on the World Wide Web at intechopen.com / online-first / 77840. Exemplary methods for pre-treating plastics include chemical cleaning, odor removal, deinking, delamination, extraction methods, dissolution-based pre-treatment (dissolution-precipitation method and solid-liquid extraction method). Solid-liquid extraction methods include ultrasonic extraction, supercritical fluid extraction, microwave-assisted extraction, and accelerated solvent extraction. Any of these methods may be used for the pre-treatment step, either alone or in combination.

[0102] In some embodiments, the pre-treating step comprises applying microwaves at a second temperature, which is less than about 150°C, less than about 140°C, less than about 130°C, less than about 120°C, less than about 110°C, less than about 100°C, less than about 90°C, less than about 80°C, less than about 70°C, less than about 60°C, or less than about 50°C.

[0103] After the pre-treatment step, waste materials are removed from the pre-treated plastic. By removing the waste materials, a substantially pure feedstock is prepared.

[0104] In the grinding step, the plastic is ground into plastic particles. Grinding can be accomplished by methods known in the art, such as using a mortar and pestle for small amounts of plastic, or using a grinder, such as a mining grinder, for large amounts of plastic.

[0105] In some embodiments, the grinding step is performed at a second temperature. The second temperature is a temperature less than about 150°C, less than about 140°C, less than about 130°C, less than about 120°C, less than about 110°C, less than about 100°C, less than about 90°C, less than about 80°C, less than about 70°C, less than about 60°C, or less than about 50°C. The size of the resulting plastic particles ranges from about 1 mm to about 10 mm. In some embodiments, the size of the resulting plastic particles ranges from about 1 mm to about 8 mm. In some embodiments, the size of the resulting plastic particles ranges from about 1 mm to about 7 mm. In some embodiments, the size of the resulting plastic particles ranges from about 1 mm to about 6 mm. In some embodiments, the size of the resulting plastic particles ranges from about 1 mm to about 5 mm. In some embodiments, the size of the resulting plastic particles ranges from about 1 mm to about 4 mm. In some embodiments, the size of the resulting plastic particles ranges from about 1 mm to about 3 mm.

[0106] It should be appreciated that plastic particles may need to be ground more than once to obtain the desired particle size. In some embodiments, particles having the desired size can be removed from larger sized particles. This allows the larger sized particles to be ground again. This process can be repeated until all particles have the desired size. Continuous throughput methods for grinding and removal are known in the art. In one example, a vacuum eductor method is used.

[0107] The method of the present disclosure may further include a step (c) of removing the hydrogen produced in step (b). In this step, the hydrogen produced is removed from the reactor. In this removing step, the hydrogen produced may be removed together with non-hydrogen by-products, such as hydrocarbons (e.g., methane and ethylene), carbon dioxide, tars, carbon products, etc. Alternatively, the hydrogen produced may be separated from the non-hydrogen by-products.

[0108] Optionally, the removing step includes the substep of purifying the produced hydrogen, in which the produced hydrogen is filtered from non-hydrogen by-products.

[0109] Alternatively, the removing step includes the substeps of (i) purifying the produced hydrogen, and (ii) purifying the produced carbon product.

[0110] Methods for separating solids from gases are well known in the art. Suitable devices for carrying out this separation include cyclone separators, filtration (e.g., membrane filtration), and pressure swing adsorption devices.

[0111] In embodiments where the hydrocarbons are separated from the produced hydrogen, the hydrocarbons may be recycled back to the fluidization gas.

[0112] In embodiments where the carbon products are separated from the produced hydrogen, the carbon products may be recycled back to the reactor and used as nucleation sites for carbon growth.

[0113] The process of the present disclosure may optionally further comprise a step (d) of removing the catalyst used in step (b). By removing the catalyst after step (b), the catalyst may be recycled / recirculated and used again.

[0114] Advantageously, the disclosed method converts waste plastics into valuable H2 and solid carbon, thus extracting useful energy from the waste plastics while closing the carbon loop. The method provides beneficial reuse of the plastic portion of municipal solid waste for both energy and carbon sequestration, thus helping to combat climate change and reducing atmospheric carbon. The disclosed method is carried out semi-continuously and can be scaled up to a continuous mode.

[0115] 4.3 Devices for producing hydrogen The present disclosure provides an apparatus for producing hydrogen, the apparatus comprising: a reactor for reacting a plastic with a catalyst to form a mixture; an inlet for introducing a gas feed; a microwave generator; an optional temperature sensor; and an outlet configured to exhaust product hydrogen formed in the reactor.

[0116] Referring to Figure 2, an apparatus for producing hydrogen is provided. The apparatus 10 includes a reactor 12 and a microwave generator 14. The apparatus also includes a gas supply 16 in flow communication with the reactor 12 via a gas supply line 18. The gas supply line 18 contains a shutoff valve 22. In the exemplary embodiment, the apparatus contains a single gas supply 16. However, it is understood that the apparatus 10 can be modified to contain additional gas supplies, each in flow communication with the reactor 12 via a gas supply line, which in turn contains a shutoff valve. The reactor 12 includes an inlet 20 in flow communication with the gas supply line 18. The gas supply includes an inert gas, such as nitrogen, argon, or helium.

[0117] Reactor 12 also includes an outlet 24. Outlet 24 is configured to exhaust product hydrogen formed in reactor 12. Outlet 24 may be in flow communication with a hydrogen gas storage vessel 26 configured to store the product hydrogen for future use.

[0118] The microwave generator 14 is configured to irradiate the reactor 12 directly with microwaves.

[0119] The apparatus 10 also includes a temperature sensor (not shown) configured to measure the temperature of the reactor. The temperature sensor detects the temperature of the catalyst so that the catalyst temperature can be optimized. In some operations, it may be desirable to have multiple temperature sensors at different locations within the apparatus 10.

[0120] Apparatus 10 can be configured to include additional components. For example, in some embodiments, the apparatus includes a mechanical mixer or other device that promotes mixing of the catalyst, plastic, and porous media, if present. Apparatus 10 can also include a vessel for separating the product hydrogen from the by-products. The separation vessel can be in flow communication with outlet 24 and hydrogen storage vessel 26.

[0121] In embodiments where plastics are pre-treated, the apparatus 10 may include a waste vessel 34 (not shown). The waste vessel may be in flow communication with an outlet 28 (not shown) of the reactor 12. The waste vessel serves to separate the pre-treated plastics from waste materials.

[0122] The apparatus may further include a grinder 30 (not shown) that grinds either the pretreated or untreated plastic to a desired particle size. Particles of the desired size are introduced into the reactor 12. The grinder 30 may be connected to a vacuum eductor 32 so that the ground particles can be continuously ground until the desired size is reached.

[0123] 3 shows an embodiment of the present disclosure where the apparatus includes a vessel for separating product hydrogen from by-products. As shown, the apparatus 200 includes a reactor 212 and a microwave generator 214. The reactor includes an inlet 234 for introducing plastic, catalyst, and porous media into the reactor 212.

[0124] Reactor 212 also includes an inlet 220 in flow communication with a gas supply 218 (not shown) through a shut-off valve 222 (not shown). Depending on the size of reactor 220 and the reaction conditions, apparatus 200 can be modified to contain two or more gas feeds.

[0125] Reactor 212 includes outlet 236. Outlet 236 is configured to exhaust the reaction mixture hydrogen formed in reactor 212. Outlet 236 may be in flow communication with a separation vessel 238 configured to separate the reaction products from the catalyst. Separation vessel 238 contains outlets 224, 240, and 242. Outlet 224 is in flow communication with a hydrogen gas storage vessel 226 configured to store the product hydrogen for future use. Outlet 240 is in flow communication with reactor 212 and is configured to recycle the catalyst to reactor 212. Outlet 242 is in flow communication with a vessel 244 configured to store the carbon by-product.

[0126] 4 shows a reactor according to an embodiment of the present disclosure. The reactor 312 includes an inlet 334a for introducing the plastic 350, an inlet 334b ​​for introducing the catalyst 352, and an inlet (not shown) for introducing the porous media 358. The catalyst 352 may be a virgin catalyst or a recycled catalyst. The recycled catalyst may be intermixed with the hydrocarbons. The reactor 312 also includes an inlet 320 in flow communication with a gas supply 318 (not shown) via a shutoff valve 322 (not shown). A microwave generator (not shown) is configured to irradiate the reactor 212 directly with microwaves.

[0127] The reactor 312 includes an outlet 336. The outlet 336 is configured to exhaust a reaction mixture 354 of hydrogen and carbon products formed in the reactor 312.

[0128] The reactor described herein is a two-stage reactor, comprising either a fixed bed or a fluidized bed. In a fixed bed configuration, the reactor comprises (a) a bed for holding plastic and, if present, a porous medium, and (b) a bed for holding a catalyst, where the bed for holding the catalyst is placed on top of the bed for holding plastic and, if present, a porous medium. The two beds are in contact at their interface. Such a bed configuration creates a secondary reactor.

[0129] In a fluidized configuration, the reactor comprises a fluidized bed containing the plastic, porous media if present, and catalyst. The fluidized bed can be upflow, circulating, or bubbling. Here, the catalyst is fluidized by the plastic, which is selectively heated by microwaves. The heated catalyst transfers heat to the plastic.

[0130] Returning to Figure 4, reactor 312 includes a fluidized bed 356 and a distribution plate 348. The distribution plate contains holes sized and spaced to allow gas to enter the fluidized bed and prevent channeling of the gas through the catalyst.

[0131] Advantageously, the use of a two-stage reactor allows for selective microwave heating. The catalyst can be heated to a different temperature than the plastic and the porous media, if present. The plastic does not absorb microwave energy, preventing melting of the plastic before the catalyst reacts at the bond-breaking reaction temperature. Another advantage is that the temperature of the catalyst can be maintained above the pyrolysis temperature.

[0132] The devices described herein can optionally be connected to one or more analytical instruments that monitor, detect, or measure the reaction products at specific time intervals. Analytical instruments include, but are not limited to, gas chromatography instruments and mass spectrometers.

[0133] The apparatus of the present disclosure is capable of producing hydrogen semi-continuously and can be scaled up to continuous hydrogen production. EXAMPLES

[0134] 5. Working Example The following examples are presented for illustrative purposes and are not to be construed as limiting the scope of the presently disclosed subject matter.

[0135] [Example 1] Materials and equipment Granular mixed plastic waste (MPW) with a nominal diameter of approximately 3 mm was used as the polymer for catalytic conversion screening. The MPW consisted of approximately 31 wt% LDPE, 25 wt% HDPE, 19 wt% PP, 12 wt% PS, and 13 wt% PET, which is typical of the plastic composition in municipal solid waste streams. For non-catalytic testing, silicon carbide (SiC) was mixed with the MPW as a microwave absorber. For catalytic testing, various Fe-based catalysts were used: 50% Fe / Al2O3, FeAlOx-5, magnetite, 50% Fe / MgO, 50% Fe / ZSM-5, and iron powder.

[0136] The conversion tests were carried out in an h-field 2.45 GHz microwave reactor supplied by Malachite technologies.

[0137] [Example 2] General method Before each test, a sample of MPW, as well as SiC and / or catalyst, was loaded into a quartz reactor tube, which was placed in the center of the microwave applicator. The sample temperature was measured by an infrared pyrometer through a sight glass the size of the waveguide applicator, which detects the temperature of the sample surface just inside the quartz tube. The temperature settings were controlled by a PID. In a typical test, the reactor was purged with N2(g) before the microwave generator was started and the sample was heated under a continuous flow of N2 (300 SCCM). Volatiles exiting the reactor were flushed through a filter and cold trapped to condense the tar, while non-condensable gases were analyzed by micro-gas chromatography (micro-GC) and mass spectrometry (MS) for compositional analysis. Test times varied as each test was run until gas production was no longer detected in the MS and N2(g) concentration was 100%. At the end of the test, the spent sample and tar were weighed to quantify the char and tar yields. "Char" is the solid material remaining after light gases (e.g., coal gas) and tars are expelled or released from the carbonaceous material during the initial stages of the reactor, and "tars" are complex hydrocarbons in liquid form produced along with the primary gas products during the conversion reaction.

[0138] [Example 3] Non-catalytic and catalytic conversion tests were carried out in the HPMWR according to the experimental conditions outlined in Table 1 below. For non-catalytic and catalytic tests with SiC, SiC or catalyst was added to the MPW at a 3:1 MPW / catalyst ratio. For catalytic tests, each of the catalysts reached the processing temperature without the addition of SiC. The microwave sensitivity of these catalysts can be attributed to their high Fe loading (Fe 50% wt%, higher for magnetite and Fe powder).

[0139] Due to the high temperature, the plastic was converted into hydrogen, hydrocarbons, and carbon products.

[0140] [Table 1]

[0141] The alumina served as a porous bed packing material to prevent the MPW from melting below the center of the reactor. Each test catalyst was evaluated for its ability to convert MPW to hydrogen. The results are shown in Figures 5-7.

[0142] FIG. 5 shows the evaluation during the conversion reaction of the measured percent yields of hydrogen, liquid hydrocarbons, carbon monoxide (CO), and carbon dioxide (CO2). FIG. 5 shows that of all the tested catalysts, magnetite (6) produced the highest yield of hydrogen (about 70%) and the lowest yield of liquid hydrocarbons (about 10%). FeAlO x (5) produced the lowest yield of hydrogen (less than 20%) and about 5% yield of liquid hydrocarbons.

[0143] FIG. 5 also shows that magnetite (6) produced the least amount of CO, CO2, and CH4 by-product gases, indicating that magnetite is a highly active catalyst that produces the greatest yield of hydrogen from plastics under these reaction conditions.

[0144] Figure 6 shows the evaluation during conversion of char, tar, and gas yields for catalysts SiC (700°C), SiC (850°C), 50% FeAl2O3, FeAlOx, magnetite, FeMgO, FeXSM5, and Fe powder. As shown in Figure 6, the Fe-based catalyst produced the highest amount of gas products while the tar production was minimal. This in turn minimizes the cost in the separation unit since the higher the gas production, the easier it is to separate the gas from the solid and liquid residues (e.g., char and tar).

[0145] The amount of char produced was higher with magnetite compared to the designer catalysts FeAlOx, Fe / MgO, Fe / Al2O3, and FeMgOx, indicating higher carbon formation and decomposition of plastics.

[0146] Figure 7 shows the evaluation of the test catalysts listed in Table 1 during the conversion reaction in terms of absorbed energy (x) per kg of MPW used and absorbed energy (●) per kg of hydrogen produced. Figure 7 shows that magnetite (6) used the least amount of energy for the reaction compared to the designer catalysts Fe / Al2O3 (4), FeAlOx (5), and Fe / MgO (7). This result suggests that the system is less energy consuming when using magnetite as a catalyst under microwave heating. The reduced energy consumption seen with magnetite further reduces the costs involved in the conversion of plastics to hydrogen.

[0147] It will be apparent to those skilled in the art that certain embodiments of the presently disclosed subject matter may be directed to one or more of the embodiments set forth above and below in any combination.

[0148] Although the present invention has been disclosed in some detail by way of illustration and example for purposes of clarity of understanding, it will be apparent to those skilled in the art that various modifications may be made and equivalents may be substituted without departing from the true spirit and scope of the invention. Accordingly, the description should not be construed as limiting the scope of the invention.

[0149] All references, publications, patents, and patent applications disclosed herein are incorporated by reference in their entirety. [Explanation of symbols]

[0150] 10, 200 devices 12, 212, 312 Reactor 14, 214 Microwave Generator 16 Gas supplies 18, 218, 318 Gas supply pipe 20, 220, 234, 320, 334a, 334b ​​entrance 22, 222, 322 Shut-off valve 24, 28, 236, 224, 240, 242, 336 exit 26, 226 Hydrogen gas storage vessel 30 Crusher 32 Vacuum Eductor 34 Waste Vessel 238 Separation Vessel 244 Vessel 348 Distribution Plate 350 Plastic 352 Catalyst 354 Reaction Mixture 356 Fluidized Bed 358 Porous media

Claims

1. 1. A method for producing hydrogen, comprising: (a) contacting plastic with a catalyst and a gas feed in a fluidized bed; and (b) applying microwaves to heat the catalyst to a first temperature in the range of 500°C to 2000°C; thereby producing hydrogen.

2. The method of claim 1 , wherein the microwaves are applied at a frequency in the range of 100 MHz to 8 GHz.

3. The method of claim 1 , wherein the microwaves are applied continuously.

4. The method of claim 1, wherein the plastic is treated for a time ranging from 30 seconds to 10 minutes.

5. 2. The method of claim 1, wherein the plastic is selected from the group consisting of polypropylene (PP), polycarbonate (PC), polystyrene (PS), polyethylene (PE), polyvinyl chloride (PVC), acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET), nylon, and polyamide, and combinations thereof.

6. The method of claim 1 , wherein the plastic is mixed plastic waste.

7. 10. The method of claim 1, wherein the catalyst comprises an oxide of a metal selected from the group consisting of Ni, Co, Fe, Cu, Ce, Zr, Al, Si, Mg, Mn, Ti, V, Cr, Zr, Nb, and W, and combinations thereof.

8. The method of claim 1 , wherein the catalyst comprises magnetite.

9. 10. The method of claim 1, wherein the gas supply comprises a gas selected from the group consisting of nitrogen, argon, and combinations thereof.

10. The method of claim 1, wherein the gas feed comprises a hydrocarbon.

11. The method of claim 1, wherein the gas supply comprises carbon dioxide.

12. The method of claim 1 , wherein step (a) comprises contacting the plastic with a porous medium.

13. 13. The method of claim 12, wherein the porous media comprises a material selected from the group consisting of silica, alumina, zeolite, and dolomite, and combinations thereof.

14. 10. The method of claim 1, further comprising the step (c) of removing hydrogen produced in step (b).

15. 1. An apparatus for producing hydrogen, comprising: a reactor for producing hydrogen; a fluidized bed; an inlet for introducing a gas feed; a microwave generator; an optional temperature sensor; and an outlet configured to exhaust product hydrogen formed in the reactor.

16. 16. The apparatus of claim 15, wherein the reactor is a two-stage reactor.

17. 16. The apparatus of claim 15, further comprising an inlet for introducing a catalyst.

18. 16. The apparatus of claim 15, further comprising an inlet for introducing plastic.

19. 16. The apparatus of claim 15, further comprising an inlet for introducing the plastic and catalyst.

20. 16. The apparatus of claim 15, further comprising a gas storage vessel.

21. 16. The apparatus of claim 15, further comprising a vessel for separating the produced hydrogen from by-products.

22. The apparatus described in claim 21, wherein the vessel for separating the produced hydrogen includes an outlet configured to recycle catalyst to the reactor, the outlet being in flow communication with the reactor.

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