PROCESSO E SISTEMA PARA A DESPOLIMERIZAÇÃO DE PLÁSTICO RESIDUAL

Abstract

PROCESS AND SYSTEM FOR THE DEPOLYMERIZATION OF RESIDUAL PLASTIC. A continuous flow process and system for the depolymerization of plastic. A heterogeneous mixture of plastic particles, a solvent, and a catalyst are continuously pumped through a heating zone at a flow rate high enough to maintain a particle velocity large enough to keep the plastic particles in suspension. The temperature of the heterogeneous mixture is raised in the heating zone and maintained in a holding zone to complete the depolymerization of the mixture into a homogeneous solution containing a liquefied reaction product. The homogeneous solution is cooled to solidify and precipitate a solid reaction product. The solid reaction product is separated from the solvent to be recycled. The solvent is recirculated to be reused as a constituent of the heterogeneous mixture.

Description

1 / 9 PROCESS AND SYSTEM FOR DEPOLYMERIZATION OF RESIDUAL PLASTIC CROSS-REFERENCE ON RELATED REQUEST

[001] This application claims priority to U.S. Provisional Application No. 62 / 964,948, filed January 23, 2020, which is incorporated herein by reference. FUNDAMENTALS

[002] The invention generally relates to the depolymerization of resin, plastic or polymer. More particularly, it relates to the depolymerization of residual plastic in a continuous process.

[003] Plastic is conventionally depolymerized in large reaction vessels usually equipped with a heating jacket and a stirrer. The depolymerization reaction is contained within the vessel until depolymerization is complete. After depolymerization, the vessel is emptied and then refilled. Each batch is heated to accelerate depolymerization and then cooled to produce viable feedstock for new polymers. The batch process typically takes between 20 min and 800 min. Continuous operation is simulated by sequentially emptying and refilling a group of reaction vessels in a rotating fashion. The constant need to fill, heat, cool, empty, and repeat wastes energy and requires additional equipment to maintain the appearance of a real continuous flow in a parallel batch process. SUMMARY

[004] A process embodying the features of the invention for plastic depolymerization comprises: Petition 870220064813, dated 07 / 22 / 2022, p. 17 / 38 2 / 9 (a) continuously flow a mixture containing solid plastic particles in a solvent through a line in a heating chamber at a particle velocity high enough to keep the plastic particles suspended in the solvent and prevent the plastic particles from clumping together and clogging the line; and (b) transfer heat through the line in the heating chamber to heat the mixture to a reaction temperature to initiate depolymerization of the plastic particles in the solvent into a homogeneous solution including a liquefied reaction product.

[005] A system embodying features of the invention for the continuous depolymerization of plastic comprises a pump operating at a pump flow rate and a line through which the pump continuously feeds a heterogeneous mixture including plastic particles in a solvent at a particle velocity. A heating zone raises the temperature of the heterogeneous mixture flowing through the line to a reaction temperature of at least 150°C. The conversion of the heterogeneous mixture containing the plastic particles into a homogeneous solution containing a liquefied reaction product, including monomer, dimer, oligomers and / or reaction by-products, is initiated in the heating zone. BRIEF DESCRIPTION OF THE DRAWINGS

[006] FIG. 1 is a block diagram of a system embodying features of the invention for plastic depolymerization.

[007] FIG. 2 is a flowchart showing the progression of a volume of plastic undergoing a process of Petition 870220064813, dated 07 / 22 / 2022, page 18 / 38 3 / 9 depolymerization in the system of FIG. 1. DETAILED DESCRIPTION

[008] A system and process for depolymerizing plastic are shown in FIGS. 1 and 2. The system and process can be used with various plastics such as, but not limited to, PET, modified PET, PET blends, PEN, PBT, PET-G, PLA, PGA, PLGA, PEF, copolyesters, polycarbonates, polyamides (Nylon), polyurethanes and combinations and blends. Depolymerization of plastics into the following, but not limited to: bis(2-hydroxyethyl) terephthalate (BHET), dimethyl terephthalate (DMT), terephthalic acid (TA), bis(2-hydroxyethyl) naphthalate (BHEN), bis(2-hydroxyethyl) furanoate (BHEF), their respective oligomers, acids, half-esters or mixed esters. Additionally, chemically useful compounds such as dioctyl terephthalate (DOTP), diisobutyl terephthalate (DITP), dibutyl terephthalate (DBTP), bisphenol A (BPA), lactates, bis(2-hydroxyethyl) terephthalamide (BHETA) and other terephthalamides.

[009] Solid plastic particles of residual polyester material, in the form of flakes, fines, grains, granules, granola, chunks, blocks and / or powder, are mixed with a solvent and a catalyst in a mixer 10 to produce a heterogeneous mixture 12. The mixer 10 may use an agitator, such as a propeller 13, stirrer, or other agitator or a recirculating solvent to make the mixture. Or the mixture may be premixed. Examples of solvents are, but not limited to, ethylene glycol (EG), diethylene glycol (DEG), glycol ethers, methanol, ethanol, propanol, butanol, 2-ethylhexanol, tetramethylcyclobutanediol (CBDM), cyclohexanedimethanol (CHDM), Petition 870220064813, dated 07 / 22 / 2022, page 19 / 38 4 / 9 alcohols, ethanol, amines, ionic liquids, polar protic solvents, polar aprotic solvents, and water. Examples of suitable catalysts include, but are not limited to: zinc salts, zinc acetate; zinc chloride; titanium salts; manganese salts; magnesium salts; sodium hydroxide; potassium hydroxide; 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD); 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU); magnesium acetate, 4-dimethylaminopyridine (DMAP); amines; trialkyl amines; and combinations of these catalysts. The heterogeneous mixture 12 is pumped through a series of connected lines, such as tubes or pipes, by a pump 14. In the agitator, drill, or extruder, it is necessary to advance the mixture through the system. Pump 14 operates at a flow rate high enough to move mixture 12 through the system with a particle velocity high enough to keep the particles suspended in the solvent and prevent the particles from clumping together and clogging the lines.By operating continuously without stopping, pump 14 flows the heterogeneous mixture through the system at a uniform rate, making the conversion of plastic into liquefied product a function of position within the system rather than a function of time – as in batch systems.

[0010] An optional preheating heat exchanger (preheater) 16 is used to preheat the heterogeneous mixture 12. The preheater 16 can heat the heterogeneous mixture 12 by a heat source such as a flame, steam, hot oil, or a circulated heat transfer fluid. Or the hot homogeneous solution, containing the liquefied product after the depolymerization reaction, can be used in the preheater 16 to transfer heat to the Petition 870220064813, dated 07 / 22 / 2022, page 20 / 38 5 / 9 heterogeneous mixture and, in the process, cool itself.

[0011] The preheated heterogeneous mixture 12' flows continuously into and through a downstream heating chamber 18, where depolymerization begins. The heating chamber 18 may be implemented as a reactor heat exchanger that raises the temperature of the heterogeneous mixture to a reaction temperature of at least 150°C. The heterogeneous mixture is heated in the reaction heat exchanger 18 by a heat source 20. The heat source 20 may directly heat the heterogeneous mixture with microwave radiation, direct flame, electrically heated tube, inductively heated tube, geothermal, magnon drag thermoelectricity, or ohmically, as some examples. Or the heat source 20 may indirectly heat the heterogeneous mixture by directly heating a heat transfer fluid external to the heating chamber 18. Examples of suitable transfer fluids are hot oil, a thermal fluid, a molten salt, and steam.The heated heat transfer fluid is then pumped past the line containing the heterogeneous mixture in heating chamber 18. Heat is transferred from the heat transfer fluid to the heterogeneous mixture to initiate depolymerization. The heterogeneous mixture flowing through heating chamber 18 is not directly contacted by the heat transfer fluid.

[0012] A holding tube 22, after the heating chamber 18, maintains the reaction temperature for at least one minute to complete the conversion of the heterogeneous mixture containing plastic into a homogeneous solution 24 Petition 870220064813, dated 07 / 22 / 2022, page 21 / 38 6 / 9 containing the liquefied product. The holding tube 22 can be made from an insulated drum or coil of tubing or pipe, or as a jacketed tube or container. Or the holding tube can be part of the heating chamber instead of being a separate component. The reaction is completed in the holding tube. The existing homogeneous solution contains the solvent, spent catalyst, and depolymerized plastic in the form of a liquefied reaction product that typically includes monomers, oligomers, and / or minor reaction byproducts (e.g., half-esters, half-amides, blended esters, blended amides).

[0013] The homogeneous solution 24 is continuously pumped through the optional preheating heat exchanger 16 to cool itself and preheat the incoming heterogeneous mixture 12. A backpressure regulator 26 maintains a system pressure, for example, 100 psi to 400 psi (689 kPa to 2757 kPa), above the vapor pressure of the solvent at the reaction temperature.

[0014] After flowing through the backpressure regulator 26, the homogeneous solution 24 flows through an optional cooling heat exchanger (cooler) 28 which uses cold water or other heat transfer fluid from the cooled reservoir 30 to remove any excess heat that the preheater 16 did not recover.

[0015] After the solution is cooled, it is poured into precipitation or crystallization tanks and cooled until the liquefied product precipitates as a solid reaction product 34. The solvent is then decanted, filtered, centrifuged, or distilled from the solid reaction product. The Petition 870220064813, dated 07 / 22 / 2022, page 22 / 38 7 / 9 The solid reaction product can be subsequently pressed through a filter to further separate it from any remaining solvent. Decantation, filtration, centrifugation, or distillation of the solvent, followed by pressing to separate the solid reaction product 34 in solution 24 from solvent 36, are represented in FIG. 1 by a separator 32.

[0016] The separated solvent 36 is recirculated back to the mixer 10 for reuse. An optional solvent cleaning, purification, or regeneration step may be required to remove reaction contaminants from the solvent feeding the subsequent heterogeneous mixture 12. Reaction contaminants may include particulate matter, ionic salts, cations, used catalysts, dyes, adhesives, blend components, fillers, and / or decomposed solvent. Contamination removal 42 may occur by passing the separated solvent 36 through filters and / or over sorbents such as activated carbon, ion exchange resin, diatomaceous earth, sand, zeolites, clay, silica, alumina, oxides, size exclusion, and / or tangential flow filtration. Contamination removal 42 from solvent 36 may be an in-line or out-of-line process. Contamination removal 42 may occur in the separated solvent step 36 or in the homogeneous solution step 24.

[0017] Thus, the system moves the heterogeneous mixture 12 through four zones: Z1 - a cold inlet zone where the mixture is fed into the system by pump 14; Z2 - a preheating zone where the mixture is heated in the preheater 16; Z3 - a heating zone where the mixture is heated to raise its temperature to Petition 870220064813, dated 07 / 22 / 2022, p. 23 / 38 8 / 9 reaction temperature; and Z4 - a holding zone where the mixture is maintained at the reaction temperature to complete the conversion of the heterogeneous mixture into the homogeneous solution 24. The homogeneous solution 24 is moved through a cooling zone Z5 where the homogeneous solution is cooled in the cooler 28 or by heat transfer to the heterogeneous mixture 12 entering the preheater 16. The pump 14 maintains a continuous flow through the system which ensures a particle velocity of the heterogeneous mixture high enough to keep the particles in suspension. In this way, the plastic particles do not settle in the lines and do not clog the system.

[0018] The sizes of plastic particles pumped through the system may vary, but are typically between 0.1 µm and 20,000 µm in at least one dimension. To keep the particles in suspension, the flow rate of pump 14 is adjusted to ensure a particle velocity of at least 20 cm / s through the system. Particle velocities above 20 cm / s or 30 cm / s provide a safety margin. A pump flow rate is adjusted equal to the product of the desired particle velocity and the cross-sectional area of ​​the lines (pipes or tubes) through which the mixture is pumped. If mixers are installed in the lines between pump 14 and regulator 26, lower particle velocities will be possible.

[0019] In the heating zone Z3, the heating chamber 18 raises the temperature to or higher than the reaction temperature to initiate the depolymerization reaction, which is completed in the retention zone Z4. The length L of the retention tube 22 in the retention zone Z4 depends on its area. Petition 870220064813, dated 07 / 22 / 2022, p. 24 / 38 9 / 9 of cross-sectional area A, the pump flow rate Q, and the retention time T required at the reaction temperature to complete the reaction: L = QT / A. The retention time can be in the range of 5 min to 10 min or even from 1 min to 60 min. The diameter of the lines running through the zones is from 1 cm to 10 cm, but can be as large as 100 cm. If jacketed piping is used, the jacket diameter can be in the range of 1.1 to 5.0 times the diameter of the inner pipe through which the mixture is pumped. Petition 870220064813, dated 07 / 22 / 2022, p. 25 / 38

Claims

1 / 8 CLAIMS 1. Continuous flow process for depolymerization of plastic, characterized in that it comprises: (a) continuously flowing a mixture containing solid plastic particles, a catalyst and a solvent through a preheating heat exchanger and then through a line into a heating chamber; wherein the mixture flows at a rate sufficient to ensure a particle velocity of at least 30 cm / s to maintain the suspension of the plastic particles in the solvent and to prevent the plastic particles from clumping together and clogging the line;wherein the plastic particles consist of polyethylene terephthalate, modified polyethylene terephthalate, mixtures of polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyethylene glycol terephthalate, polylactic acid, poly(glycolic acid), poly D,L-lactic-co-glycolic acid, polyethylene 2,5-furandicarboxylate, copolyesters, polycarbonates, polyamides, or any combination thereof; wherein the solvent consists of ethylene glycol, diethylene glycol, glycol ethers, 2-ethylhexanol, tetramethylcyclobutanediol, cyclohexanedimethanol, alcohols, ethanolamine, ionic liquids, polar protic solvents, polar aprotic solvents, or any combination thereof; (b) transfer heat through the line in the heating chamber to heat the mixture to a reaction temperature of at least 150°C to initiate the depolymerization of the plastic particles in the solvent into a homogeneous solution including a liquefied reaction product;c) maintain the mixture at the reaction temperature for at least one minute; and d) drain the homogeneous solution through a passage in the preheating heat exchanger after the homogeneous solution exits the heating chamber; wherein the homogeneous solution transfers heat to the mixture drained through the preheating heat exchanger to preheat the mixture.

2. Continuous flow process according to claim 1, characterized in that the liquefied reaction product includes monomers, dimers or oligomers.

3. Continuous flow process according to claim 1, characterized in that the liquefied reaction product includes bis(2-hydroxyethyl) terephthalate, dimethyl terephthalate, terephthalic acid, bis(2-hydroxyethyl) naphthalate, bis(2-hydroxyethyl) furanoate, their respective oligomers, acids, hemiesters, mixed esters, dioctyl terephthalate, diisobutyl terephthalate, dibutyl terephthalate, bisphenol A, lactates, bis(2-hydroxyethyl) terephthalamide, other terephthalamides, or any combination thereof.

4. Continuous flow process according to claim 1, characterized in that the reaction temperature is within 20°C of the melting point of the plastic particles in the mixture.

5. Continuous flow process according to claim 1, characterized in that the reaction temperature is at least 230°C.

6. Continuous flow process, according to claim 1, characterized in that it further comprises maintaining a system pressure above the vapor pressure of the solvent at the reaction temperature to prevent the solvent from evaporating.

7. Continuous flow process according to claim 1, characterized in that the catalyst consists of zinc salts, zinc acetate, zinc chloride, titanium salts, titanium(IV) isopropoxide, titanium(IV) n-butoxide, manganese salts, magnesium salts, sodium hydroxide, potassium hydroxide, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,8-diazabicyclo[5.4.0]undec-7-ene, magnesium acetate, 4-dimethylaminopyridine, amine, trialkylamine, or any combination thereof.

8. Continuous flow process according to claim 1, characterized in that it further comprises: (e) cooling the homogeneous solution in a cooling heat exchanger to a temperature below 50°C; (f) allowing the cooled homogeneous solution to settle at room temperature for a time between about 0.5 hours and 100 hours to allow the liquefied reaction product to solidify into a solid reaction product; (g) separating the solid reaction product from the solvent by one or more of decantation, filtration, centrifugation, pressing and distillation; and (h) reusing the solvent separated from the solid reaction product in the process.

9. Continuous flow process according to claim 1, characterized in that it further comprises: (e) separating the solvent from the reaction product; (f) removing contaminants from the solvent by filtration or Petition 870240098562, dated 11 / 19 / 2024, page 23 / 41 4 / 8 with sorbents; and (g) reusing the solvent in the process by mixing the solid plastic particles in the reused solvent to form the mixture.

10. Continuous flow process according to claim 1, characterized in that the plastic particles have a size between 0.1 μm and 20,000 μm in at least one dimension.

11. Continuous flow process, according to claim 1, characterized in that the process reaches a steady state when the temperature of the mixture at a predetermined point in the heating chamber is equal to the reaction temperature; and in that in the steady state the process consumes a smaller amount of non-renewable energy than during an initial heating state.

12. Continuous flow process, according to claim 11, characterized in that in the steady state the continuous process consumes less than 5 MJ of non-renewable energy to depolymerize 1 kilogram of solid plastic particles.

13. Continuous flow process, according to claim 11, characterized in that in the steady state the continuous process consumes less than 3 MJ of non-renewable energy to depolymerize 1 kilogram of solid plastic particles.

14. Continuous flow process, according to claim 1, characterized in that in a steady state, a maximum production rate of the liquefied reaction product is calculated using the equation Y=FM, where Y is a maximum production rate of the liquefied reaction product, F is the feed rate of the solid plastic particles, and M is the ratio of the molecular weight of the main product to the molecular weight of the repeating plastic unit.

15. Continuous flow process, according to claim 1, characterized in that the solid plastic particles comprise polyethylene terephthalate; and wherein the liquefied reaction product comprises: 85% to 98% bis(2-hydroxyethyl)terephthalate; less than 10% 2-hydroxyethyl terephthalic acid; less than 10% dimers; less than 6% mixed esters with diethylene glycol; less than 1% terephthalic acid; less than 1% trimers; and less than 1% larger oligomers.

16. System for continuous depolymerization of plastic characterized in that it comprises: a pump operating at a flow rate; a line through which the pump continuously feeds a heterogeneous mixture including solid plastic particles, a catalyst and a solvent at a flow rate; wherein the flow rate is sufficient to ensure a particle velocity of at least 30 cm / s; wherein the solid plastic particles consist of polyethylene terephthalate, modified polyethylene terephthalate, mixtures of polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyethylene glycol terephthalate, polylactic acid, poly(glycolic acid), poly D,L-lactic-co-glycolic acid, polyethylene 2,5 Petition 870240098562, dated 11 / 19 / 2024, p. 25 / 41 6 / 8 furandicarboxylate, copolyesters, polycarbonates, polyamides or any combination thereof;wherein the solvent consists of ethylene glycol, diethylene glycol, glycol ethers, 2-ethylhexanol, tetramethylcyclobutanediol, cyclohexanedimethanol, alcohols, ethanolamine, ionic liquids, polar protic solvents, polar aprotic solvents, or any combination thereof; a heating zone raising the temperature of the heterogeneous mixture flowing through the line to a reaction temperature of at least 150°C; wherein the conversion of the heterogeneous mixture containing the solid plastic particles into a homogeneous solution containing a liquefied reaction product is initiated in the heating zone; a holding tube receives the heated heterogeneous mixture from the heating zone to maintain the reaction temperature for a holding time of at least one minute at the flow rate to completely convert the heterogeneous mixture containing the solid plastic particles into the homogeneous solution containing the liquefied reaction product;and a preheating heat exchanger that preheats the heterogeneous mixture upstream of the heating zone; wherein the preheating heat exchanger indirectly preheats the heterogeneous mixture with the homogeneous solution containing the liquefied reaction product to cool the homogeneous solution.

17. System according to claim 16, characterized in that it further comprises: a mixer upstream of the heating zone using an agitator or solvent recirculation to agitate the heterogeneous mixture. Petition 870240098562, dated 11 / 19 / 2024, p. 26 / 41 7 / 8 18. System according to claim 17, characterized in that the holding tube is an insulated tube or pipe of sufficient length to ensure that the conversion of the heterogeneous mixture into a homogeneous solution containing liquefied reaction product is complete.

19. System according to claim 18, characterized in that the retention time in the retention tube is between 1 minute and 60 minutes.

20. System according to claim 16, characterized in that it further comprises a reactor heat exchanger in the heating zone that raises the temperature of the heterogeneous mixture to the reaction temperature; wherein a heat source is configured to heat a heat transfer fluid flowing past the heterogeneous mixture in the reactor heat exchanger to transfer heat to the heterogeneous mixture.

21. System according to claim 16, characterized in that it further comprises a contaminant removal zone downstream of the heating zone and includes a filter or sorbent, wherein the contaminant removal zone is configured to remove contaminants from the solvent.

22. System according to claim 16, characterized in that it further comprises a cooler downstream of the heating zone and including a cooling heat exchanger with the homogeneous solution on one side indirectly cooled by a cold liquid on the other side of the heat exchanger, wherein the cooler lowers the temperature of the homogeneous solution to below 50°C. Petition 870240098562, dated 11 / 19 / 2024, p. 27 / 41 8 / 8 23. System according to claim 16, characterized in that it further comprises a separator that includes a precipitation or crystallization tank, in which the liquefied reaction product in the homogeneous solution solidifies into a solid reaction product and precipitates.

24. System according to claim 16, characterized in that the heating zone includes a heat exchanger; wherein the heating zone heat exchanger and the preheating heat exchanger are each a shell-and-tube, shell-and-tube, coil-and-shell, tube-and-tube, jacketed pipe, plate-and-shell, sheet-and-frame or sheet-and-frame heat exchanger.

25. System according to claim 16, characterized in that the heating zone and the preheating heat exchanger each include multiple lengths of jacketed tubing having a jacket around an inner tube, wherein the jacketed tubing is connected.

26. System according to claim 25, characterized in that the inner diameter of the inner tube in the jacketed pipe is between 1 cm and 100 cm and the diameter of the jacket is between 1.1 and 5.0 times the diameter of the inner tube. Petition 870240098562, dated 11 / 19 / 2024, pp. 28 / 41

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