Method and system of depolymerizing a polyolefin
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- DOW GLOBAL TECHNOLOGIES LLC
- Filing Date
- 2024-08-26
- Publication Date
- 2026-07-08
AI Technical Summary
Polyolefins such as polyethylene and polypropylene are difficult to recycle due to their stability and the limited effectiveness of existing recycling methods, which are often energy-intensive and result in low recycling rates.
A mechanocatalysis approach is used to depolymerize polyolefins, involving a ball mill that combines mechanical forces with catalytic processes. The method includes grinding polyolefins with a heterogeneous catalyst in a hydrogen atmosphere at controlled temperatures to reduce molecular weights and facilitate recycling.
This method effectively reduces the number and peak average molecular weights of polyolefins, enhancing their recyclability and potentially increasing the percentage of recycled polymers, while being more energy-efficient compared to traditional methods.
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Abstract
Description
Method and System of Depolymerizing a PolyolefinField of Disclosure
[0001] Embodiments of the present disclosure are directed to polyolefins and more specifically to a method and system of depolymerizing a polyolefin.Background
[0002] Polymers such as polyethylene and polypropylene are very stable materials that are not easily broken down or recycled. To add to this problem, the global production of these polymers is increasing year by year, which leads to environmental concerns. Recycling of these polymers is a possible option to reduce the production of new polymers, but polymer recycling still has many hurdles. This is reflected in the fact that less than 10 percent of polymers are believed to have been recycled. Of the various options, mechanical recycling has been suggested as a way to increase this percentage. Mechanical recycling however remains very limited due to the quality and type of polymer required for such recycling. As such, there remains a need for effective polymer recycling, including polymer recycling back to the monomer level..Summary
[0003] The present disclosure provides various embodiments for addressing the needs for effective mechanocatalysis polymer recycling. The embodiments of the present disclosure provide for, among other things, a method and system of depolymerizing a polyolefin using a mechanocatalysis approach. This mechanocatalysis approach combines mechanical forces with catalytic processes to drive the polymer recycling process of the present disclosure. For the various embodiments, the mechanocatalysis approach of the present disclosure provides for chemical recycling of the polyolefin in which mechanical forces initiate the reaction. For the embodiments, the method of depolymerizing the polyolefin includes the use of a ball mill, where a polyolefin (e.g., a polyethylene or polypropylene) and a heterogeneous catalyst are supplied to a cylindrical shell of the ball mill. The ball mill includes a grinding media that during the operation of the cylindrical shell of the ball mill act to comminute the polyolefin in the cylindrical shell to produce a ground polyolefin. The method and system further include maintaining the ground polyolefin in the cylindrical shell of ball mill in a hydrogen (H2) based atmosphere at a temperature of 0 degrees Celsius (°C) to 200 °C to produce a depolymerized polyolefin structure that has a reduced number average molecular weight (Mn) as compared to the Mn of the polyolefin supplied to the cylindrical shell of the ball mill.
[0004] For the various embodiments, the depolymerized polyolefin structure can also have in addition to the reduction in the Mn, a reduced peak average molecular weight (Mp) as compared to the Mp of the polyolefin supplied to the cylindrical shell of ball mill. For example, the Mn and Mp of the depolymerized polyolefin structure can each independently be 20% to 99.99% smaller than the Mn and Mp, respectively, of the polyolefin supplied to the cylindrical shell of the ball mill. For the various embodiments, the polyolefin is selected from the group consisting of a polyethylene and a polypropylene. For the various embodiments, the polyolefin supplied to the cylindrical shell has a mean particle size of 0.001 millimeter (mm) to 3 mm.
[0005] For the various embodiments, the heterogeneous catalyst can be selected from the group consisting of a supported platinum-based heterogeneous catalyst, a supported palladium-based heterogeneous catalyst, a supported nickel-based heterogeneous catalyst, a supported cobalt-based heterogeneous catalyst, a supported rhodium-based heterogeneous catalyst, a supported iron-based heterogeneous catalyst, a supported ruthenium-based heterogeneous catalyst, a supported iridium-based heterogeneous catalyst and a combination thereof. In a specific embodiment, the heterogeneous catalyst can be the platinum-based heterogeneous catalyst that comprises 0.01 weight percent (wt.%) to 10 wt.% of platinum on a zeolite Y, where the wt.% is based on the total weight of the platinum-based heterogeneous catalyst. In an additional specific embodiment, the heterogeneous catalyst can be the nickel- based heterogeneous catalyst that comprises 0.01 wt.% to 10 wt.% of nickel on a zeolite Y, where the wt.% is based on the total weight of the nickel-based heterogeneous catalyst. In additional embodiments, the grinding media supplied to the cylindrical shell of the ball mill can include the heterogeneous catalyst. For example, the grinding media can be formed with a metal selected from the group consisting of platinum, palladium, rhodium, iridium, zirconium, nickel, iron, cobalt, ruthenium, or combinations thereof, where the metal helps to form the heterogeneous catalyst. In additional embodiments, the cylindrical shell of the ball mill can include a nickel-based material (e.g., the cylindrical shell of the ball mill can be at least partially formed from nickel-based material).
[0006] For the various embodiments, supplying the polyolefin and the heterogeneous catalyst to the cylindrical shell of the ball mill can further include supplying the heterogeneous catalyst in a mass-volume percentage of 0.01 to 50 determined from the mass of the heterogeneous catalyst and the total volume of the polyolefin and the heterogeneous catalyst being supplied to the cylindrical shell of the ball mill. The hydrogen (H2) based atmosphere comprises an atmosphere of 1 volume percent (vol. %) to 100 vol. % hydrogen, where nitrogen(Nz) constitutes a remainder of the hydrogen (H2) based atmosphere when less than 100 vol. % hydrogen.
[0007] The present disclosure also provides for a system of depolymerizing the polyolefin, that includes the ball mill having the grinding media formed with a metal selected from the group consisting of platinum, palladium, rhodium, iridium, zirconium, nickel, iron, cobalt, ruthenium, or combinations thereof, where the metal helps to form the heterogeneous catalyst, and the polyolefin for depolymerization contained within the ball mill. In addition to the grinding media, at least a portion of the ball mill can be formed of a metal selected from the group consisting of platinum, palladium, rhodium, iridium, zirconium, nickel, iron, cobalt, ruthenium, or combinations thereof. For the various embodiments, the presence of the metal in the ball mill can potentially add catalytic aspects to the depolymerization of the polyolefin to the cylindrical shell of the ball mill.Detailed Description
[0008] The present disclosure provides various embodiments that address the depolymerization of a polyolefin. Embodiments of the present disclosure provide a method and system of depolymerizing a polyolefin. Depolymerizing polyolefins are inherently challenging due to the properties of the polyolefins. Polyolefins are very stable materials, which results in great difficulties in breaking their carbon-carbon bonds. In addition,, polyolefins such as polyethylenes and polypropylenes come in a variety of types (e.g., linear low density polyethylene, high density polyethylene, homopolymer versus copolymers of polypropylene) each with their unique properties and additives that can influence their recycling. Attempting to use the same process to depolymerize these different types of polyolefins may result in inconsistencies in the depolymerized polyolefin, making the depolymerized polyolefin unusable. In addition, available techniques for polyolefin depolymerization (e.g., pyrolysis) are very energy intensive. However, mechanocatalytically depolymerizing polyolefins, as described here, may provide an effective approach to recycling and depolymerizing polyolefins. The present disclosure provides various embodiments for addressing the needs for effective mechanocatalysis polymer recycling. The embodiments of the present disclosure provide for, among other things, a method and system of depolymerizing a polyolefin using a mechanocatalysis approach. This mechanocatalysis approach combines mechanical forces with catalytic processes to drive the polymer recycling process of the present disclosure. For the various embodiments, the mechanocatalysis approach of the present disclosure provides for chemical recycling of the polyolefin in which mechanical forces provided in the ball mill initiate the reaction.
[0009] Unless stated to the contrary, implicit from the context, or customary in the art, all parts and percentages herein are based on the total weight of the material or composition that is being discussed. All temperatures discussed herein are in degree Celsius (°C), and all test methods are current as of the filing date of this disclosure.
[0010] The terms "comprising," "including," "having," and their derivatives, are not intended to exclude the presence of any additional component, step or procedure, whether or not the same is specifically disclosed. To avoid any doubt, all claims using of the term "comprising" may include any additional elements, unless stated to the contrary. In contrast, the term, "consisting essentially of" excludes from the scope of any succeeding recitation any other component, step or procedure, excepting those that are not essential to operability. The term "consisting of" excludes any component, step or procedure not specifically delineated or listed.
[0011] The terms "polyolefin" shall mean polymers produced from an olefin or alkene as a monomer. As generally known in the art, common forms of polyolefin include polyethylene and polypropylene as well as copolymers of ethylene and other alpha olefins..
[0012] The term "polyethylene" as used herein means a polymer comprising greater than 50% by weight of units which have been derived from ethylene (ethylene monomers). This includes polyethylene homopolymers or copolymers in which one or more different olefinic monomers, as are known in the art, are polymerized with ethylene. Common forms of polyethylene known in the art include, but are not limited to, high density polyethylene (HDPE), low density polyethylene (LDPE); linear low density polyethylene (LLDPE).
[0013] The term "polypropylene" as used herein means a polymer comprising greater than 50% by weight of units which have been derived from propylene (propylene monomers). This includes polypropylene homopolymers or copolymers in which one or more different olefinic monomers, as are known in the art, are polymerized with ethylene. Common forms of polypropylene known in the art include high density polypropylene (HDPP), homopolymer polypropylene and random copolymer polypropylene, as are known in the art.
[0014] For the various embodiments, the polyolefin undergoing the depolymerization according to the present disclosure is selected from the group consisting of a polypropylene and a polyethylene, as provided herein. For instance, the polyolefin can be a high density polyethylene, where such polyolefins are characterized by a density typically in a range of about 0.94 to 0.97 g / cm3. Other examples include, but are not limited to, low density polyethylene (e.g., density typically in a range of about 0.91 to 0.925 g / cm3), linear low density polyethylene and the various types of polypropylene as are known in the art. For the present disclosure, the term polyolefin willmostly be used, where it is understood that any one of the polyethylene or polypropylene provided herein or as are known in the art can be substituted therefor.
[0015] For the various embodiments, the present disclosure provides a method and system of depolymerizing a polyolefin using a ball mill, as discussed herein. For the various embodiments, the method of depolymerizing polyolefins, as described herein, can include supplying a polyolefin, as provided herein, and a heterogeneous catalyst to a cylindrical shell of the ball mill. In various embodiments, the polyolefin can be ground to a predetermined mean particle size before being placed in the cylindrical shell of the ball mill. For instance, the polyolefin supplied to the cylindrical shell can have a mean particle size of 0.001 millimeter (mm) to 3 mm. Other ranges for the mean particle size are also possible. For example, the ground polyolefin can have a mean particle size with a lower limit of 0.001 , 0.01 , 0.1 , 0.5, 1 , or 1 .25 millimeter (mm), to an upper limit of 1 .5, 1 .75, 2, 2.25, 2.5, or 3 mm. As used herein, the mean particle size refers to the average size of the polyolefin particles within a population of polyolefin particles.Measurement of the mean particle size can be done using an arithmetic mean (average) particle size in which the size of all particles in a representative sample of the polymer particles is summed and then divided by the total number of particles.
[0016] For various embodiments, the heterogeneous catalyst can be added to the cylindrical shell before, after and / or with the polyolefin. For the various embodiments, the heterogeneous catalyst assists with the depolymerization process. For the various embodiments, the heterogeneous catalyst is selected from the group consisting of a supported platinum-based heterogeneous catalyst, a supported palladium-based heterogeneous catalyst, a supported nickel-based heterogeneous catalyst, a supported cobalt-based heterogeneous catalyst, a supported rhodium-based heterogeneous catalyst, a supported iron-based heterogeneous catalyst, a supported ruthenium-based heterogeneous catalyst, a supported iridium-based heterogeneous catalyst and a combination thereof. Specific examples of the heterogeneous catalyst of the present disclosure can include, but are not limited to, the platinum-based heterogeneous catalyst that comprises 0.01 weight percent (wt.%) to 10 wt.% of platinum on a zeolite Y, where the wt.% is based on the total weight of the heterogeneous catalyst. In one embodiment, the heterogeneous catalyst can be the platinum-based heterogeneous catalyst that comprises 1 wt.% of platinum on the zeolite Y, where the wt.% is based on the total weight of the platinum-based heterogeneous catalyst. In an additional embodiment, the heterogeneous catalyst of the present disclosure can include, but are not limited to, the nickel-based heterogeneous catalyst that comprises 0.01 wt.% to 10 wt.% of nickel on a zeolite Y, where the wt.% is based on the total weight of the heterogeneous catalyst. In one embodiment, theheterogeneous catalyst can be the nickel-based heterogeneous catalyst that comprises 1 wt.% of nickel on the zeolite Y, where the wt.% is based on the total weight of the nickel-based heterogeneous catalyst.
[0017] The heterogeneous catalyst of the present disclosure may also be a zeolite without a transition metal, such as, but not limited to ZSM-5, Zeolite Y, ZSM-22 and Mordenite, among others, or other material with a Lewis or Bronsted acidity with or without a transition metal as provided herein.
[0018] Examples of other heterogeneous catalysts can include those having a transition metal found in any one of groups 3 through 12 of the periodic table of the elements (2016 IUPAC Periodic Table of the Elements). In a specific embodiment, examples of other heterogeneous catalysts can include those having a transition metal from Groups 3, 4, 5, 6, 7 and 8 of the period table of the elements (2016 IUPAC Periodic Table of the Elements). Such heterogeneous catalysts can be formed from nickel, palladium, platinum, cobalt, rhodium, Iridium, iron, ruthenium, molybdenum, tungsten, titanium, chromium, vanadium, zirconium, or combinations thereof. In some embodiments, the heterogeneous catalyst can be a supported catalyst on an amorphous mineral from a group comprising alumina, silica, silica-aluminas, magnesia, ceria, zirconia, zinc oxide, clays, carbon (e.g., carbon nanotubes) or a combination thereof. In various embodiments, the heterogeneous catalyst can include a zeolite support, such as SI02, A1203, AIPO4, or a combination thereof.
[0019] For the various embodiments, the cylindrical shell of the ball mill further includes grinding media to comminute the polyolefin in the cylindrical shell. For the various embodiments, the grinding media placed in the cylindrical shell can be used to comminute the polyolefin as the cylindrical shell rotates. For instance, the grinding media placed in the cylindrical shell can collide with the polyolefin, causing mechanical stress that not only comminute the polyolefin but also assists in the depolymerization of the polymer chains. The amount, shape, size, and material of the grinding media can affect the final properties of the comminuted polyolefin. Examples of such grinding media include ceramic particles (e.g., zirconia, etc.), metal particles (e.g., steel, chrome, iron, etc.) and glass particles, where the particles can include ball or rod shapes. For the various embodiments, the selection of the specific grinding media can be a function of the type and physical properties of the polyolefin (e.g., hardness, particle size, etc.) undergoing depolymerization according to the present disclosure.
[0020] In additional embodiments, the grinding media can also include and / or form the heterogenous catalyst of the present disclosure. For example, the grinding media can include the heterogenous catalyst as provided herein. For the various embodiments, the heterogenouscatalyst can be provided as a coating on and / or integrated into the structure of the grinding media. The grinding media, therefore, can act as the heterogeneous catalyst as the polyolefin is comminuted. The grinding media can also be formed with a metal selected from the group consisting of platinum, palladium, rhodium, iridium, zirconium, nickel, iron, cobalt, ruthenium, or combinations thereof. The presence of such metals with the grinding media may help with the depolymerization of the polyolefin.
[0021] For the various embodiments, supplying the polyolefin and the heterogeneous catalyst to the cylindrical shell of the ball mill can further include supplying the heterogeneous catalyst in a mass-volume percentage of 0.01 to 50 (mass-volume %) determined from the mass of the heterogeneous catalyst and the total volume of the polyolefin and the heterogeneous catalyst being supplied to the cylindrical shell of the ball mill. All individual values and subranges from 0.01 mass-volume % to 50 mass-volume % are included; for example, the mass-volume % can comprise a lower limit of 0.01 , 0.1 , 1 .0, 5 or 10 vol. % to an upper limit of 50, 45, 40, 30 or 20 vol. %. Specific ranges include 0.01 to 20 mass-volume % and 1 to 40 mass-volume %. As appreciated by one skilled in the art, the mass-volume percentage represents the proportion of the mass and volume of each component (e.g., the heterogeneous catalyst or the polyolefin) in the cylindrical shell of the ball mill.
[0022] For various embodiments, the grinding media along with the heterogeneous catalyst inside the cylindrical shell of the ball mill comminute the polyolefin to produce a ground polyolefin. The ground polyolefin will have a mean particle size that is smaller than the mean particle size of the polyolefin supplied to the cylindrical shell of the ball mill. This reduction in mean particle size helps to both increase the surface area of the polyolefin so as to all better access by the heterogeneous catalyst and to create localized area of increased temperature of the polyolefin as the shearing and / or grinding occurs. Such an increase in temperature along with the presence of the heterogeneous catalyst (either supplied to the cylindrical shell neat and / or as a part of the grinding media as discussed herein) helps to promote depolymerizing the polyolefin.
[0023] For the various embodiments, the method further includes maintaining the ground polyolefin in the cylindrical shell of ball mill in a hydrogen (H2) based atmosphere at a temperature of 0 degrees Celsius (°C) to 200 °C to produce the depolymerized polyolefin structure. For the various embodiments, the depolymerized polyolefin structure can have a reduced number average molecular weight (Mn) as compared to the Mn of the polyolefin supplied to the cylindrical shell of the ball mill. In addition, the depolymerized polyolefin structure can also have a reduced peak average molecular weight (Mp) as compared to the Mp of the polyolefin supplied to the cylindrical shell of ball mill. For the various embodiments, the Mn and Mp of the depolymerizedpolyolefin structure can each independently be 20% to 99.99% smaller than the Mn and Mp, respectively, of the polyolefin supplied to the cylindrical shell of the ball mill. In an additional embodiment, the Mn and Mp of the depolymerized polyolefin structure can each independently be 20% to 95% smaller or 20% to 35% smaller than the Mn and Mp, respectively, of the polyolefin supplied to the cylindrical shell of the ball mill. Values for Mn and Mp can be measured using gel permeation chromatography (GPC) or size exclusion chromatography (SEC) with known standards and techniques.
[0024] Maintaining the ground polyolefin in the cylindrical shell of ball mill in the hydrogen (H2gas) based atmosphere can comprise an atmosphere of 1 volume percent (vol. %) to 100 vol. % hydrogen. All individual values and subranges from 1 vol. % to 100 vol. % hydrogen are included; for example, the hydrogen based atmosphere can comprise a lower limit of 1 , 5, 10, 15 or 20 vol. % to an upper limit of 80, 85, 90, 95 or 100 vol. %. For the various embodiments, nitrogen (N2) constitutes a remainder of the hydrogen (H2) based atmosphere when less than 100 vol. % hydrogen is present in the cylindrical shell.
[0025] Maintaining the ground polyolefin in the cylindrical shell of ball mill at a temperature of 0 °C to 200 °C to produce the depolymerized polyolefin structure. All individual values and subranges from 0 °C to 200 °C are included; for example, the temperature can comprise a lower limit of 0, 5, 10, 15, 20 or 30 °C to an upper limit of 60, 70, 80, 100, 140 or 200 °C. In one embodiment, the ground polyolefin in the cylindrical shell of ball mill is maintained at a temperature of 0 °C to 80 °C to produce the depolymerized polyolefin structure.
[0026] Embodiments of the present disclosure also include a system of depolymerizing the polyolefin, as discussed herein. The system includes the ball mill, as are generally known in the art, which include, among other things, the cylindrical shell that rotates through rotational torque applied by one or more of a motor to a girth gear joined to the cylindrical shell and under the control of a control unit as are known in the art. As discussed herein, the polyolefin and the heterogeneous catalyst are supplied to the cylindrical shell of the ball mill, where the ball mill includes the grinding media to comminute and depolymerize the polyolefin as the ball mill operates (e.g., the cylindrical shell rotates) under the conditions provided herein. For the various embodiments, the heterogeneous catalyst can be as provided herein. In additional embodiments, the cylindrical shell of the ball mill can include a grinding media that is formed with a metal selected from the group consisting of platinum, palladium, rhodium, iridium, zirconium, nickel, iron, cobalt, ruthenium, or combinations thereof so as to form the heterogeneous catalyst. Other coatings and / or compositions for the heterogeneous catalyst and / or the grinding media, as provided herein, can also be included in the cylindrical shell of the ball mill. For the variousembodiments, it is also possible for at least a portion of the ball mill to be formed of a catalytic metal as provided herein. For example, at least a portion of the ball mill can be formed with a metal selected from the group consisting of platinum, palladium, rhodium, iridium, zirconium, nickel, iron, cobalt, ruthenium, or combinations thereof. Examples include where the cylindrical shell of the ball mill includes a nickel-based material (e.g., at least a portion of one or more of the interior surfaces of the cylindrical shell is formed with a catalytic metal as provided herein, such as the nickel-based material).EXAMPLES
[0027] Inventive Examples (IE) and Comparative Examples (CE) were made using the following materials (Table 1 ) and methods. IE 1 , IE 2 and CE A used an attritor system ball mill equipped with 5-millimeter (mm) zirconia grinding media.TABLE 1Experimental Procedures
[0028] IE 1 was prepared by pre-grinding the HDPE resin to a mean particle size of less than 3 millimeter (mm). 35 grams (g) of the pre-ground HDPE containing 10 weight percent (wt.%) of platinum catalyst along with 1750 g of the Zirconia Media was added to the jar, which was then attached to the ball mill using a mill jar holder. Water at ambient temperature is passedthrough the cooling jacket of the ball mill at a rate of approximately 100 milliliter a minute (mL / min) was used to control the temperature of the jar's contents. The ball mill jar with its contents was allowed to rotate at 400 revolutions per minute (RPM) for 10 hours at atmospheric pressure with a 20 cc / min 5 vol.% hydrogen in nitrogen purge.
[0029] IE 2 was prepared as IE 1 provided above, except the HDPE resin was not preground to the mean particle size of less than 3 mm.
[0030] CE A was prepared the same as IE 2 provided above, except the platinum catalyst was not added to the jar.
[0031] During the rotation of the above experiments, the temperature of the contents of the jar increased 5 degrees Celsius (°C), from about 22.4 °C to about 27.5 °C (measured with handheld IR sensor), plateauing at about 27.5°C after 2 hours of run time. After the 10 hrs, the media and the processed HDPE resin of IE 1 -2 and CE A-B were separated through a sieve. The metrics of the processed HDPE resin for IE 1 -2 and CE A-B were measured and are seen in Table 2.Results
[0032] The metrics for the pre-processed high-density polyethylene is shown in Table 2.TABLE 2Testin MethodsTABLE 3
[0033] The molecular weight was calculated as follows. The standard test injects 1 .5 mg / ml solutions through a 200 pL injection loop to 4 20-pm Agilent "Mixed A" GPC columns (Agilent Technologies, CA, USA) at 1 m1 / min and 150 °C. Sample preparation was done using the PolymerChar autosampler with a 1 -hour sample dissolution time in an oven at 160 °C in combination with gentle shaking. Detector alignment and calibration along with column calibration and data processing were performed using a PolymerChAR "GPC One" software (using custom in-house written and verified processing methods). The GPC column set was calibrated using Easical GPC / SEC calibration standards from Agilent. The set consists of twenty narrow molecular weight distribution polystyrene standards with molecular weights ranging from 500 to 5,500,000 g / mol arranged in 4 mixtures. The narrow standards mixtures were run using the same method as used for polyethylene. The polystyrene standard peak molecular weights were converted to polyethylene molecular weights (Mw) using equation 1 in which M is the molecular weight, A equals 0.43 and B equal 1 .0.Mpolyethylene = A x (Mpolystyrene)BEquation 1
Claims
What is claimed is:1 . A method of depolymerizing a polyolefin, comprising: supplying the polyolefin and a heterogeneous catalyst to a cylindrical shell of a ball mill, wherein the ball mill includes grinding media; comminuting the polyolefin in the cylindrical shell of the ball mill using the grinding media to produce a ground polyolefin; and maintaining the ground polyolefin in the cylindrical shell of ball mill in a hydrogen (H2) based atmosphere at a temperature of 0 degrees Celsius (°C) to 200 °C to produce a depolymerized polyolefin structure having a reduced number average molecular weight (Mn) as compared to the Mn of the polyolefin supplied to the cylindrical shell of the ball mill.
2. The method of claim 1 , wherein the depolymerized polyolefin structure has a reduced peak average molecular weight (Mp) as compared to the Mp of the polyolefin supplied to the cylindrical shell of ball mill.
3. The method of claim 2, wherein the Mn and Mp of the depolymerized polyolefin structure are each independently 20% to 99.99% smaller than the Mn and Mp, respectively, of the polyolefin supplied to the cylindrical shell of the ball mill.
4. The method of any one of claims 1-3, wherein the grinding media includes the heterogeneous catalyst.
5. The method of any one of claims 1-4, wherein the grinding media is formed with a metal selected from the group consisting of platinum, palladium, rhodium, iridium, zirconium, nickel, iron, cobalt, ruthenium, or combinations thereof.
6. The method of any one of claims 1-5, wherein the heterogeneous catalyst is selected from the group consisting of a supported platinum-based heterogeneous catalyst, a supported palladium-based heterogeneous catalyst, a supported nickel-based heterogeneous catalyst, a supported cobalt-based heterogeneous catalyst, a supported rhodium-based heterogeneous catalyst, a supported iron-based heterogeneous catalyst, a supported ruthenium-based heterogeneous catalyst, a supported iridium-based heterogeneous catalyst and a combination thereof.
7. The method of claim 6, wherein the platinum-based heterogeneous catalyst comprises 0.01 weight percent (wt.%) to 10 wt.% of platinum on a zeolite Y.
8. The method of claim 6, wherein the nickel-based heterogeneous catalyst comprises 0.01 wt.% to 10 wt.% of nickel on a zeolite Y.
9. The method of any one of claims 1 -8, wherein supplying the polyolefin and the heterogeneous catalyst to the cylindrical shell further includes supplying the heterogeneous catalyst in a mass-volume percentage of 0.01 to 50 determined from the mass of the heterogeneous catalyst and the total volume of the polyolefin and the heterogeneous catalyst being supplied to the cylindrical shell of the ball mill.
10. The method of any one of claims 1 -9, wherein the cylindrical shell of the ball mill includes a nickel-based material.11 . The method of any one of claims 1 -10, wherein the hydrogen (H2) based atmosphere comprises an atmosphere of 1 volume percent (vol. %) to 100 vol. % hydrogen, wherein nitrogen (N2) constitutes a remainder of the hydrogen (H2) based atmosphere when less than 100 vol. % hydrogen.
12. The method of any one of claims 1 -11 , wherein the polyolefin is selected from the group consisting of a polyethylene and a polypropylene.
13. The method of any one of claims 1 -12, wherein the polyolefin supplied to the cylindrical shell has a mean particle size of 0.001 millimeter (mm) to 3 mm.
14. A system of depolymerizing a polyolefin, comprising; a ball mill having a grinding media formed with a metal selected from the group consisting of platinum, palladium, rhodium, iridium, zirconium, nickel, iron, cobalt, ruthenium, or combinations thereof, to form a heterogeneous catalyst; and the polyolefin for depolymerization contained within the ball mill.
15. The system of claim 14, wherein at least a portion of the ball mill is formed of a metal selected from the group consisting of platinum, palladium, rhodium, iridium, zirconium, nickel, iron, cobalt, ruthenium, or combinations thereof.