Method and system for isolating at least one compound from polymer-containing waste
A chemically reducing atmosphere with gaseous nitrogen compounds in the pyrolysis of polymer waste addresses the inefficiencies of current methods, achieving high yields and low emissions in the isolation of valuable compounds from plastics like PC, PA, PU, PES, and PET.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV
- Filing Date
- 2025-05-08
- Publication Date
- 2026-05-21
Smart Images
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Abstract
Description
[0001] Fraunhofer Society...eV
[0002] 259PCT 0746
[0003] Method and apparatus for isolating at least one compound from polymer-containing waste
[0004] A process and a system for isolating at least one compound from polymer-containing waste are provided. This process comprises a chamber containing a chemically reducing atmosphere and heated to a temperature in the range of 300 °C to 800 °C. Polymer-containing waste is placed in the chamber, and a chemically reducing gas stream containing an inert gas is introduced into the chamber via a gas line to react components of the gas stream with the polymer-containing waste to form a gaseous product. The gaseous product is then directed out of the chamber via another gas line and into at least one condensation device to isolate the at least one compound from the gaseous product by condensation and to obtain the resulting gaseous product as the product gas.The gas stream contains a gaseous basic nitrogen compound and / or a source of a gaseous basic nitrogen compound suitable for releasing a gaseous basic nitrogen compound in the heated chamber. Alternatively or additionally, the polymer-containing waste provided in the chamber is mixed with a source of a gaseous basic nitrogen compound suitable for releasing a gaseous basic nitrogen compound in the heated chamber.
[0005] Not all plastics can be recycled mechanically. These include polycarbonate (PC) and polyurethanes (PU), which can only be mechanically recycled in certain cases (compositions). Furthermore, there are plastics such as polyamides (PA) and polyesters that can be partially mechanically recycled, but for which waste fractions are also generated for which this option is no longer viable. Alternative processes are being sought for the underlying polymers of these plastics and waste fractions, aiming to preserve the greatest possible structural integrity.
[0006] PC, for example, is an engineering thermoplastic. It is used in numerous applications with specific mechanical or optical requirements, such as housings for electronic devices, various components of motor vehicles, or as transparent glass. PC cannot be mechanically recycled from waste streams because the thermal stress of repeated extrusion causes it to lose the required properties. The associated loss of material quality and usability of the recycled material is significant and therefore not economically viable. As a result, PC is primarily thermally recycled (incineration), which generates CO2 emissions, or it is disposed of in landfills, which release harmful microplastics into the environment over the long term. This also applies to other plastics to varying degrees.
[0007] According to the waste hierarchy, alternative processes are therefore being sought to preserve the structures synthesized at the cost of energy and resources, thereby avoiding CO2 and other emissions and byproducts. These processes belong to the methods of chemical recycling. They primarily involve solvolysis, pyrolysis, or gasification. Pyrolysis, the thermal decomposition in the absence of oxygen, breaks the chemical bonds in polymers. In condensation polymers, such as PC, the bond breaks preferentially occur at functional groups, producing mixtures of the original monomers or structurally closely related molecules. With suitable process control, sufficiently simple mixtures with high yields of these valuable molecules are obtained, which can be used for the synthesis of new plastics or for other chemical syntheses.Therefore, a recycling process that uses pyrolysis is particularly promising for plastics with functional groups such as PC, PA, PU, PES or PET.
[0008] One problem with pyrolytic processes, however, is their lack of selectivity. Generally, various reactions occur simultaneously during pyrolysis. The intermediates from these parallel reactions can, in turn, undergo different reactions. Depending on the feedstock and conditions, certain reaction pathways are favored, leading to the formation of desired or undesired products. In the pyrolysis of polycarbonates, for example, an undesired side reaction is the formation of macromolecules through rearrangements, crosslinking, and aromatization reactions, with these macromolecules ultimately leading to the formation of coke. Another problem is that the primary target products should not be converted into smaller compounds through secondary reactions, as this would eliminate the polymer structures that could potentially be transformed into target products (e.g., polymer monomers).
[0009] The chemical recycling of plastics with functional groups (e.g., PC, PA, PU, PES, or PET) has not been technically implemented to date due to a lack of necessity. While research on the pyrolysis of plastics, including PC, has been conducted in recent decades, no technical or commercially viable plant exists that converts PC or PC-containing input materials into recyclable raw materials (basic chemicals) based on the principles of solvolysis or pyrolysis.
[0010] WO 2022 / 174963 discloses a process for the pyrolysis of polycarbonate-containing material for the recovery of raw materials, carried out in an inert atmosphere at temperatures between 300 and 700 °C. Possible reactive gases to be added include gaseous water, hydrogen gas, or methane.
[0011] WO 2023 / 118104 Al also discloses a process for the pyrolysis of polycarbonate-containing material for the recovery of raw materials, wherein the polycarbonate-containing material may also contain a phosphorus-containing additive.
[0012] Xie et al. (Journal of Cleaner Production, 343:140204) describe a catalytic pyrolysis of the polyester polyethylene terephthalate (PET) in the presence of urea, using Y-Al₂O₃ as the catalyst. The reaction mechanism postulated is a nucleophilic attack of ammonia, generated during the thermal decomposition of urea, on the ester group of PET.
[0013] When a solid catalyst (e.g., Y-Al₂O₃, Ca(OH)₂, and / or zeolites) is used in known processes, the disadvantage is that the process is more expensive, even if the catalyst is recovered. Catalyst recovery, i.e., separating the catalyst (e.g., from the coke residue), is time-consuming and energy-intensive. Furthermore, the solid catalysts themselves can become coked, deactivated, and / or poisoned during the process, causing them to lose their catalytic effect and requiring either disposal as waste or time-consuming and energy-intensive regeneration, which is uneconomical. In the case of halogenated catalysts, there is the additional disadvantage that halogens can be released during the process, which can corrode the components used, further reducing the economic viability of the processes.
[0014] When purge gases such as H2 and / or CH4 are used in known processes, the process is cost-intensive, but the beneficial effect on product yield is minimal. Therefore, there is a need in the prior art to provide a process and a plant that enables a more cost-effective, faster, and more energy-efficient isolation of at least one compound (e.g., monomers and structurally related compounds of a polymer) from polymer-containing waste with a high yield. In particular, the process and plant should ideally not generate any additional gas that cannot be used for the new synthesis and / or should generate as little coke as possible, since coke can only be thermally utilized and thus leads to CCh emissions (i.e., CCh emissions should be kept especially low to make the process more environmentally friendly).
[0015] The problem is solved by the method with the features of claim 1 and the system with the features of claim 10. The dependent claims describe advantageous further developments.
[0016] According to the invention, a method for isolating at least one compound from a polymer-containing waste is provided, comprising or consisting of:
[0017] a) Providing a chamber that has a chemically reducing atmosphere and heating the chamber to a temperature in the range of 300 °C to 800 °C;
[0018] b) Placing a polymer-containing waste, which contains or consists of a polymer, in the chamber;
[0019] c) Directing a gas stream into the chamber via a gas line to react the polymer-containing waste with the help of the gas stream to form a gaseous product, wherein the gas stream contains an inert gas and is chemically reducing; and
[0020] d) Discharge of the gaseous product from the chamber via a further gas line and into at least one condensation device in order to isolate at least one compound from the gaseous product by condensation and to obtain the resulting gaseous product as product gas;
[0021] characterized by the fact that
[0022] i) the gas stream further contains a gaseous basic nitrogen compound and / or a source of a gaseous basic nitrogen compound capable of releasing a gaseous basic nitrogen compound in the heated chamber; and / or
[0023] (ii) the polymer-containing waste provided in the chamber is treated with a source of a gaseous basic nitrogen compound suitable for releasing a gaseous basic nitrogen compound in the heated chamber (e.g., the source of the gaseous basic nitrogen compound is added to and / or mixed with the polymer-containing waste, and / or the polymer-containing waste is sprayed with the source of the gaseous basic nitrogen compound); wherein none of the following catalysts are used in the process: aluminum oxide, calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, tin chloride, zinc chloride, aluminum chloride, and zeolite.
[0024] In a preferred embodiment of the process, none of the following catalysts are used: metal oxide, metal hydroxide, metal chloride, and zeolite. It is particularly preferred that the process also does not use a phosphorus-containing catalyst.
[0025] Polymer-containing waste is understood to mean, in particular, waste that contains or consists of at least one polymer, i.e., it may also contain other substances besides at least one polymer (e.g., reinforcing fibers). According to the invention, the term "waste" does not include virgin polymer-containing materials. However, the term "waste" preferably also includes post-industrial waste (i.e., so-called "PL waste"), which arises, for example, during the manufacture of plastic products and represents polymer-containing rejects (i.e., polymer-containing waste).
[0026] A "chemically reducing atmosphere" is understood to mean, in particular, that the atmosphere in the chamber is suitable for allowing only minimal or no oxidation of the polymer-containing waste. For example, if the chamber contains up to 2% oxygen by volume, it must contain a sufficiently high quantity of chemically reducing substances to achieve this suitability. The same applies, in particular, to the gas stream, which must be chemically reducing; that is, the gas stream must be suitable for allowing only minimal or no oxidation of the polymer-containing waste. The chemically reducing substance may contain or consist of the gaseous basic nitrogen compound and / or the source of the gaseous basic nitrogen compound.
[0027] The process according to the invention enables the rapid and energy-efficient isolation of at least one compound (e.g., monomers or structurally related compounds of a polymer) from polymer-containing waste with a high yield. In particular, the process does not generate any additional gas that cannot be used for the subsequent synthesis, and little coke is formed as an undesirable byproduct (i.e., CO2 emissions remain low). In the case of polycarbonate-containing waste, higher yields of bisphenol-A and structurally related compounds (e.g., phenol and / or styrene) can be achieved, with low coke formation and reduced product gas formation (permanent gas formation) (e.g., formation of CO, CO2, and CH4). The reduction in coke and permanent gas formation has the advantage of lowering greenhouse gas emissions, thus making the process more environmentally friendly.
[0028] In a preferred embodiment, the process is carried out continuously. In particular, a polymer-containing waste, which contains or consists of a polymer, is continuously supplied to the chamber, which has a chemically reducing atmosphere and is heated to a temperature in the range of 300 °C to 800 °C, and steps c) and d) of the process are carried out. This allows for a particularly economical implementation of the process.
[0029] The polymer-containing waste used in the process can contain or consist of a polycondensed polymer, wherein the polycondensed polymer is preferably selected from the group consisting of polycarbonate, polyamide, polyester, polylactide, and combinations thereof. The polycondensed polymer particularly preferably contains or consists of polycarbonate, especially polycarbonate containing bisphenol A monomers. Furthermore, the polymer-containing waste used in the process can contain or consist of a polyadduct, wherein the polyadduct is preferably a polyurethane.
[0030] Apart from that, the polymer-containing waste used in the process may contain or consist of a polymer produced by chain polymerization, wherein the polymer produced by chain polymerization is preferably selected from the group consisting of acrylonitrile butadiene styrene copolymer, styrene acrylonitrile copolymer, polystyrene, polyethylene, polypropylene and combinations and copolymers thereof.
[0031] Furthermore, the polymer-containing waste used in the process can contain or consist of a naturally occurring polymer, the naturally occurring polymer preferably being selected from the group consisting of cellulose, hemicellulose, lignin, and combinations thereof. The use of such waste makes the process particularly environmentally friendly, as it can be carried out in a carbon-neutral manner.
[0032] Furthermore, the polymer-containing waste used in the process can contain urea, the urea being preferably added to the polymer-containing waste before it is placed in the chamber. The urea is particularly preferably added in granular form.
[0033] Furthermore, the polymer-containing waste used in the process can contain NH3-containing water, the NH3-containing water being preferably sprayed onto the polymer-containing waste before it is placed in the chamber.
[0034] The chamber can be heated in the process to a temperature in the range of 320 °C to 750 °C, preferably 340 °C to 700 °C, particularly preferably 360 °C to 600 °C, most preferably 380 °C to 580 °C, and particularly 400 to 550 °C.
[0035] Furthermore, the chamber can contain a heating element and the chamber can be heated via the heating element, wherein the heating element is preferably selected from the group consisting of electric resistance heating, infrared radiators, microwave radiators and combinations thereof.
[0036] In addition, the chamber may contain a device for generating an ionized gas and / or a plasma, and the chamber may be heated via this device.
[0037] Furthermore, the chamber can include a combustion device suitable for burning ammonia in the gas stream with oxygen, the combustion device preferably being located upstream of an inlet point of the gas stream into the chamber. The combustion is substoichiometric, meaning the amount of chlorine is less than the amount required for complete oxidation of the NH3. This achieves a heating effect, but an excess of NH3 remains for depolymerization of the polymers in the polymer-containing waste. The advantage here is that the gas stream is heated directly (in situ) and therefore very efficiently, and the oxygen content in the gas stream can be reduced via combustion. Moreover, ammonia produced in a climate-neutral manner from H2 via water electrolysis and N2 via air separation using renewable electricity (e.g., from a photovoltaic system) can be used for this purpose.Consequently, the process can be operated in a very environmentally friendly manner.
[0038] The gas stream used in the process can contain the gaseous basic nitrogen compound in a concentration in the range of 1 to 50 vol.%, preferably in the range of 2 to 45 wt.%, particularly preferably in the range of 3 to 40 wt.%, most preferably in the range of 4 to 35 wt.%, and especially in the range of 5 to 30 wt.%, in relation to the total volume of the gas stream.
[0039] Furthermore, the gas stream used in the process can contain the source of the gaseous basic nitrogen compound in an amount suitable to establish a concentration of the gaseous nitrogen compound in the chamber of the pyrolysis reactor in the range of 1 to 50 vol.%, preferably in the range of 2 to 45 wt.%, particularly preferably in the range of 3 to 40 wt.%, most preferably in the range of 4 to 35 wt.%, and especially in the range of 5 to 30 wt.%, with respect to the total volume of the chamber.
[0040] The gas stream used in the process may contain or consist of an inert gas selected from the group consisting of nitrogen, technical nitrogen, noble gases and combinations thereof.
[0041] Furthermore, the gas stream used in the process may contain water vapor. The presence of water vapor in the gas stream can increase the yield of at least one compound.
[0042] Furthermore, the gas stream used in the process may or may not contain hydrogen. The absence of hydrogen in the gas stream allows for a more cost-effective implementation of the process without significant losses in the yield of the at least one compound and the product gas.
[0043] Apart from this, the product gas obtained in step d) can be returned to the chamber via a gas line as a gas stream, or as part of the gas stream, wherein the product gas preferably contains a gas selected from the group consisting of CO, CO2, CH4, H2, N2, C2 hydrocarbons, C3 hydrocarbons, or combinations thereof. In this process, the product gas can therefore be added to the gas stream being introduced into the chamber or replace the original gas stream, preferably via a further fluid line. This embodiment allows for a particularly economical implementation of the process.
[0044] In a preferred embodiment, the gas stream used in the process contains ammonia. Ammonia has proven to be a particularly effective gaseous basic nitrogen compound. The ammonia is preferably produced in a CO2-neutral manner. The advantage of using CO2-neutrally produced ammonia is that the process can be carried out more environmentally friendly.
[0045] In a further preferred embodiment, the gas stream used in the process contains a solid as a source of a gaseous basic nitrogen compound, wherein the solid is preferably urea. Urea has proven to be a particularly effective solid source of a gaseous basic nitrogen compound. The gas stream can, in particular, be an aerosol in which urea particles are dispersed. It is advantageous if the gas stream also contains water (e.g., as an aerosol) and / or water vapor, since this allows for the more efficient formation of gaseous basic nitrogen compounds (e.g., NH3) from urea and results in fewer byproducts that do not represent gaseous basic nitrogen compounds.
[0046] In a further preferred embodiment, the gas stream used in the process contains a liquid as a source of a gaseous basic nitrogen compound, wherein the liquid is preferably NH3-containing water. NH3-containing water has proven to be a particularly effective liquid source of a gaseous basic nitrogen compound. The gas stream can, in particular, be an aerosol in which NH3-containing water is dispersed.
[0047] In the chamber, an internal pressure in the range of 0.1 to 20 bar, preferably 0.2 to 10 bar, particularly preferably 0.4 to 5 bar, most preferably 0.6 to 2 bar, and in particular 0.8 to 1.2 bar, can be set using this method.
[0048] The condensation device used in the process can contain or consist of at least one cold trap, preferably at least two cold traps, wherein preferably the at least one cold trap, and more preferably the at least two cold traps, are each temperature-controlled to a temperature in the range of < 0 °C, preferably < -5 °C, more preferably < -10 °C, and most preferably < -15 °C, particularly < -18 °C. The at least two cold traps can be temperature-controlled to different temperatures.
[0049] In a preferred embodiment, the product gas, which is generated from the gaseous product after isolation from the at least one compound, is mixed with the gas stream that is directed into the chamber, preferably via a further fluid line. This embodiment allows for a particularly economical implementation of the process.
[0050] According to the invention, a system for isolating at least one compound from polymer-containing waste is further provided, comprising or consisting of:
[0051] a) a chamber suitable for receiving polymer-containing waste that contains or consists of a polymer;
[0052] b) a gas source for generating a gas stream, wherein the gas source contains an inert gas;
[0053] c) a gas line which is fluidly connected to the gas source and the chamber;
[0054] d) a condensation device;
[0055] e) a further gas line which is fluidly connected to the chamber and the condensing device; and
[0056] f) a control unit;
[0057] where the control unit is configured to cause,
[0058] to create a chemically reducing atmosphere in the chamber and to heat the chamber to a temperature in the range of 300 °C to 800 °C,
[0059] to direct a gas stream containing an inert gas and chemically reducing agent from the gas source into the chamber via the gas line, in order to react the polymer-containing waste with the help of the gas stream to form a gaseous product, and
[0060] to direct the gaseous product from the chamber via the further gas line and into at least one condensation device in order to isolate the at least one compound from the gaseous product by condensation and to obtain the resulting gaseous product as product gas,
[0061] characterized by the fact that the control unit is configured to cause the system to operate,
[0062] i) to introduce a gas stream into the chamber via the gas line, containing a gaseous basic nitrogen compound and / or a source of a gaseous basic nitrogen compound capable of releasing a gaseous basic nitrogen compound in the heated chamber; and / or ii) before or after the provision of polymer-containing waste in the chamber, to mix the polymer-containing waste with a (solid or liquid) source of a gaseous basic nitrogen compound capable of releasing a gaseous basic nitrogen compound in the heated chamber (e.g., the control unit is configured to cause the plant to dose and / or mix the source of the gaseous basic nitrogen compound with the polymer-containing waste, and / or to spray the polymer-containing waste with the source of the gaseous basic nitrogen compound).
[0063] the plant does not contain any of the following catalysts: aluminium oxide, calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, tin chloride, zinc chloride, aluminium chloride and zeolite (i.e., for example, neither the chamber of the plant contains such a catalyst (e.g., as a catalyst bed or in a mixture with the polymer-containing waste) nor does the gas source for generating the gas stream of the plant contain such a catalyst).
[0064] In a preferred embodiment of the plant, the plant contains none of the following catalysts: metal oxide, metal hydroxide, metal chloride, and zeolite. For example, neither the plant chamber contains such a catalyst (e.g., as a catalyst bed or in a mixture with the polymer-containing waste), nor does the gas source for generating the plant's gas stream contain such a catalyst. Particularly preferably, the plant also contains no phosphorus-containing catalyst. For example, neither the plant chamber contains such a catalyst (e.g., as a catalyst bed or in a mixture with the polymer-containing waste), nor does the gas source for generating the plant's gas stream contain such a catalyst.
[0065] The system according to the invention enables the rapid and energy-efficient isolation of at least one compound (e.g., monomers and structurally related compounds of a polymer) from polymer-containing waste with a high yield. In particular, no additional gas is formed during operation of the system that cannot be used for further synthesis, and little coke is formed as an undesirable byproduct (i.e., CO2 emissions remain low). In the case of polycarbonate-containing waste, higher yields of bisphenol-A and structurally related compounds (e.g., phenol) can be achieved, with low coke formation and reduced permanent gas formation (e.g., formation of CO, CO2, and CH4). The reduction in coke and permanent gas formation has the advantage of lowering greenhouse gas emissions, thus making the operation of the system more environmentally friendly.
[0066] In a preferred configuration, the system is set up for continuous operation.In particular, the system includes a conveying device and the system's control unit is configured to cause the conveying device to continuously convey polymer-containing waste, which contains or consists of a polymer, into the chamber, which has a chemically reducing atmosphere and is heated to a temperature in the range of 300 °C to 800 °C. The control unit is further configured to continuously cause a gas stream containing an inert gas and chemically reducing gas to be directed into the chamber via the gas line from the gas source, in order to react the polymer-containing waste with the help of the gas stream to form a gaseous product, and to direct the gaseous product out of the chamber via the further gas line and into at least one condensation device in order to isolate the at least one compound from the gaseous product by condensation.
[0067] The system may (already) contain polymer-containing waste in the chamber.
[0068] The polymer-containing waste may contain or consist of a polycondensed polymer, wherein the polycondensed polymer is preferably selected from the group consisting of polycarbonate, polyamide, polyester, polylactide, and combinations thereof. The polycondensed polymer particularly preferably contains or consists of polycarbonate, especially polycarbonate having bisphenol A monomers.
[0069] Furthermore, the polymer-containing waste may contain or consist of a polyadduct, the polyadduct preferably being a polyurethane.
[0070] Furthermore, the polymer-containing waste may contain or consist of a polymer produced by chain polymerization, wherein the polymer produced by chain polymerization is preferably selected from the group consisting of acrylonitrile butadiene styrene copolymer, styrene acrylonitrile copolymer, polystyrene, polyethylene, polypropylene and combinations and copolymers thereof.
[0071] Apart from that, the polymer-containing waste may contain or consist of a naturally occurring polymer, wherein the naturally occurring polymer is preferably selected from the group consisting of cellulose, hemicellulose, lignin and combinations thereof.
[0072] Furthermore, the polymer-containing waste can contain urea, wherein the urea is preferably added to the polymer-containing waste, and the urea is particularly preferably added in the form of granules.
[0073] Furthermore, the polymer-containing waste can contain NH3-containing water, wherein the NH3-containing water is preferably sprayed onto the polymer-containing waste.
[0074] The control unit of the system can be configured to cause the chamber to be heated to a temperature in the range of 320 °C to 750 °C, preferably 340 °C to 700 °C, particularly preferably 360 °C to 600 °C, most preferably 380 °C to 580 °C, and particularly 400 °C to 550 °C.
[0075] The gas source of the plant for generating the gas stream can contain the gaseous basic nitrogen compound in a concentration in the range of 1 to 50 vol.%, preferably in the range of 2 to 45 wt.%, particularly preferably in the range of 3 to 40 wt.%, most preferably in the range of 4 to 35 wt.%, and especially in the range of 5 to 30 wt.%, with respect to the total volume of the gas stream.
[0076] Furthermore, the gas source of the plant for generating the gas stream can contain the source of the gaseous basic nitrogen compound in an amount suitable for establishing a concentration of the gaseous nitrogen compound in the chamber of the pyrolysis reactor in the range of 1 to 50 vol.%, preferably in the range of 2 to 45 wt.%, particularly preferably in the range of 3 to 40 wt.%, most preferably in the range of 4 to 35 wt.%, in particular in the range of 5 to 30 wt.%, with respect to the total volume of the chamber.
[0077] Furthermore, the gas source of the plant for generating the gas stream may contain an inert gas selected from the group consisting of nitrogen, technical nitrogen, noble gas and combinations thereof.
[0078] Furthermore, the gas source of the plant for generating the gas flow may contain water vapor.
[0079] Furthermore, the gas source of the plant for generating the gas stream may or may not contain hydrogen.
[0080] The control unit of the system can be configured to cause the system to return recovered product gas to the chamber via a gas line, either as a gas stream or as part of the gas stream. The product gas preferably contains a gas selected from the group consisting of CO, CO2, CH4, H2, N2, C2 hydrocarbons, Cä hydrocarbons, or combinations thereof. The control unit of the system can thus be configured to cause the system to add a product gas generated from the gaseous product after isolation of the at least one compound to the gas stream being fed into the chamber, or to replace the original gas stream, preferably via another fluid line of the system.
[0081] In a preferred embodiment, the gas source for generating the gas stream contains ammonia, wherein the ammonia is preferably produced in a CO2-neutral manner.
[0082] In a further preferred embodiment, the gas source of the system for generating the gas stream contains a solid, preferably urea. The control unit of the system is preferably configured to generate a gas stream from the gas source that is an aerosol in which urea particles are dispersed. It is advantageous if the gas source of the system also contains water (e.g., as an aerosol) and / or water vapor, since this allows for the more efficient formation of gaseous basic nitrogen compounds (e.g., NH3) from the urea and results in the formation of fewer byproducts that are not gaseous basic nitrogen compounds.
[0083] In a further preferred embodiment, the gas source of the system for generating the gas stream contains a liquid, wherein the liquid is preferably water containing NFh. The control unit of the system is preferably configured to cause a gas stream to be generated from the gas source, which is an aerosol in which NFh-containing water is dispersed in the gas stream.
[0084] The control unit of the system can be configured to cause the system to introduce the gas flow into the chamber in such a way that an internal pressure in the chamber is set in the range of 0.1 to 20 bar, preferably 0.2 to 10 bar, particularly preferably 0.4 to 5 bar, most preferably 0.6 to 2 bar, and in particular 0.8 to 1.2 bar.
[0085] The condensation device of the system can contain or consist of at least one cold trap, preferably at least two cold traps, wherein the control unit of the system is preferably configured to cause the system to temper the at least one cold trap, preferably the at least two cold traps, to a temperature in the range of < 0 °C, preferably < -5 °C, particularly preferably < -10 °C, most preferably < -15 °C, in particular < -18 °C.
[0086] The control unit of the system can be configured to cause the system to add a product gas, which is generated from the gaseous product after isolating the at least one compound, to the gas stream being directed into the chamber, preferably via another fluid line of the system.
[0087] The following figures and example will be used to explain the subject matter of the invention in more detail, without limiting it to the specific embodiments shown here.
[0088] Figure 1 schematically shows a method according to the invention for isolating at least one compound from a polymer-containing waste. First, a chamber 1 is provided, which has a chemically reducing atmosphere and is heated to a temperature in the range of 300 °C to 800 °C. Then, a polymer-containing waste containing or consisting of a polymer (e.g., polycarbonate-containing waste) is provided (e.g., continuously) in the chamber 1, and a gas stream is introduced into the chamber via a gas line 2 to react the polymer-containing waste with the gas stream to form a gaseous product. The gas stream contains an inert gas 4 (e.g., N2, Ar, recycled product gas), as well as a) a gaseous basic nitrogen compound 6 (e.g., NH3) and / or b) a source 6 of a gaseous basic nitrogen compound suitable for releasing a gaseous basic nitrogen compound in the heated chamber (e.g.,Urea and / or NH3-containing water), wherein the gas stream is chemically reducing. Alternatively or additionally, the polymer-containing waste provided in chamber 1 is mixed with a source of a gaseous basic nitrogen compound suitable for releasing a gaseous basic nitrogen compound in the heated chamber. The gaseous product is then continuously discharged from chamber 1 via a further gas line 3 and into at least two condensation devices 5, 5' to continuously isolate the at least one compound from the gaseous product by condensation and to obtain the resulting gaseous product as the product gas (permanent gas). A solid residue (coke) remaining in chamber 1 can be (continuously) discharged from chamber 1 via a solid residue discharge channel 8.The at least one connection from the at least two condensation devices 5, 5' can be continuously discharged via a channel 9 for the discharge of the at least one connection.
[0089] Figure 2 shows the yields of the target compounds phenol, styrene, and bisphenol A after a process according to the invention, as described in the example, in which the polymer-containing waste consisted of a mixture of polycarbonate and acrylonitrile butadiene styrene copolymer. It can be seen that the yields of bisphenol A are up to 40% higher, depending on the partial pressure of the nitrogen compound (ammonia), compared to pyrolysis in an inert atmosphere (e.g., argon or nitrogen) or an H₂-containing atmosphere without the nitrogen compound (ammonia).
[0090] Figure 3 shows the yields of the three product fractions, gas, liquid (condensate), and solid (residue), for the process described in the example and above in relation to Figure 2. It can be seen that with an increasing volume fraction of NH3 in the gas stream (i.e., an increasing NFh partial pressure in the gas stream), the liquid yield (i.e., of liquid reaction product) increases, while the yield of product gas (i.e., permanent gas) and solid (i.e., coke) decreases. This simplifies the separation and purification of the product mixture and makes the process more economical.
[0091] Example - Implementation of a method according to the invention
[0092] A polymer-containing waste consisting of 70 wt% polycarbonate and 30 wt% acrylonitrile butadiene styrene copolymer was placed as a fixed bed in a chamber (reactor tube).
[0093] The chamber was heated from ambient temperature to the target temperature of 500 °C using an external electric heater and held at that temperature for 30 minutes after reaching the target temperature.
[0094] The chamber was then perfused with a gas consisting of argon and ammonia in different volume ratios (i.e., 0 vol%, 4 vol%, 8 vol%, 17 vol%, 30 vol%, or 40 vol% ammonia in argon) at a total volume flow rate of 836 mL / min. The resulting empty tube velocity was 11.1 cm / s.
[0095] The gaseous mixture exiting the reactor was passed through two cold traps (both cooled to -18 °C) to separate condensable compounds.
[0096] The product gas (permanent gas) escaping from the cold traps was collected in gas bags and analyzed at-line by gas chromatography.
[0097] A condensate remaining in the cold traps (containing at least one compound to be isolated) was obtained after the experiment by rinsing the cold traps with acetone. The acetone was removed by distillation. The components of the condensate were quantified by determining the residual solvent content (acetone) using headspace GC (HS-GC) and by further analysis of the contained compounds using gas chromatography with flame ionization detection (GC-FID) after calibration of the target components.
[0098] The mass of the residue (coke) remaining in the chamber was determined by weighing after the chamber had cooled.
[0099] The results are shown in Figures 2 and 3.
[0100]
[0101] 1: Chamber containing polymer-containing waste;
[0102] 2: Gas pipeline;
[0103] 3: further gas pipeline;
[0104] 4: Inert gas;
[0105] 5, 5': Condensation device;
[0106] 6: gaseous basic nitrogen compound and / or a source of a gaseous basic nitrogen compound;
[0107] 7: Product gas (permanent gas);
[0108] 8: Channel for the removal of a solid residue;
[0109] 9: Channel for the discharge of at least one connection.
Claims
Fraunhofer Society...eV 259PCT 0746 Patent claims 1. Method for isolating at least one compound from a polymer-containing waste, comprising or consisting of: a) providing a chamber having a chemically reducing atmosphere and heating the chamber to a temperature in the range of 300 °C to 800 °C; b) Providing polymer-containing waste, which contains or consists of a polymer, in the chamber; c) Directing a gas stream into the chamber via a gas line to react the polymer-containing waste with the help of the gas stream to form a gaseous product, wherein the gas stream contains an inert gas and is chemically reducing; and d) Discharge of the gaseous product from the chamber via a further gas line and into at least one condensation device in order to isolate at least one compound from the gaseous product by condensation and to obtain the resulting gaseous product as product gas; characterized by the fact that i) the gas stream further contains a gaseous basic nitrogen compound and / or a source of a gaseous basic nitrogen compound capable of releasing a gaseous basic nitrogen compound in the heated chamber; and / or ii) the polymer-containing waste provided in the chamber is mixed with a source of a gaseous basic nitrogen compound suitable for releasing a gaseous basic nitrogen compound in the heated chamber; the process does not use any of the following catalysts: aluminium oxide, calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, zinc chloride, aluminium chloride and zeolite.
2. Method according to the preceding claim, characterized in that the polymer-containing waste i) contains or consists of a polycondensed polymer, wherein the polycondensed polymer is preferably selected from the group consisting of polycarbonate, polyamide, polyester, polylactide and combinations thereof, wherein the polycondensed polymer particularly preferably contains or consists of polycarbonate, in particular polycarbonate having bisphenol A monomers; and / or ii) contains or consists of a polyadduct, wherein the polyadduct is preferably a polyurethane; and / or iii) contains or consists of a polymer produced by chain polymerization, wherein the polymer produced by chain polymerization is preferably selected from the group consisting of acrylonitrile butadiene styrene copolymer, styrene acrylonitrile copolymer, polystyrene, polyethylene, polypropylene and combinations and copolymers thereof; and / or iv) contains or consists of a naturally occurring polymer, wherein the naturally occurring polymer is preferably selected from the group consisting of cellulose, hemicellulose, lignin and combinations thereof; and / or v) contains urea, wherein the urea is preferably added to the polymer-containing waste before it is placed in the chamber, wherein the urea is particularly preferably added in granular form; and / or vi) contains an NH3-containing water, wherein the NH3-containing water is preferably sprayed onto the polymer-containing waste before it is placed in the chamber.
3. Method according to one of the preceding claims, characterized in that the chamber i) is heated to a temperature in the range of 320 °C to 750 °C, preferably 340 °C to 700 °C, particularly preferably 360 °C to 600 °C, most preferably 380 °C to 580 °C, particularly 400 °C to 550 °C; and / or ii) contains a heating element and the chamber is heated via the heating element, wherein the heating element is preferably selected from the group consisting of electric resistance heating, infrared radiators, microwave radiators and combinations thereof; and / or iii) contains a device for generating an ionized gas and / or a plasma and the chamber is heated via this device; and / or iv) comprising a combustion device suitable for burning ammonia in the gas stream with oxygen, wherein the combustion device is preferably arranged upstream of an entry point of the gas stream into the chamber.
4. Method according to one of the preceding claims, characterized in that the gas flow i) the gaseous basic nitrogen compound in a concentration in the range of 1 to 50 vol.%, preferably in the range of 2 to 45 wt.%, particularly preferably in the range of 3 to 40 wt.%, most preferably in the range of 4 to 35 wt.%, and especially in the range of 5 to 30 wt.%, with respect to the total volume of the gas stream; and / or ii) the source of the gaseous basic nitrogen compound contains in an amount suitable for achieving a concentration of the gaseous nitrogen compound in the chamber of the pyrolysis reactor in the range of 1 to 50 vol.%, preferably in the range of 2 to 45 wt.%, particularly preferably in the range of 3 to 40 wt.%, most preferably in the range of 4 to 35 wt.%, in particular especially in the range of 5 to 30 wt.%, in relation to the total volume of the chamber; and / or iii) contains or consists of an inert gas selected from the group consisting of nitrogen, technical nitrogen, noble gases and combinations thereof; and / or iv) contains water vapor; and / or v) contains hydrogen or does not contain hydrogen.
5. Method according to one of the preceding claims, characterized in that the product gas obtained in step d) is returned to the chamber via a gas line as a gas stream, or as part of the gas stream, wherein the product gas preferably contains a gas selected from the group consisting of CO, CO2, CH4, H2, N2, C2 hydrocarbon, Cä hydrocarbon or combinations thereof.
6. Method according to one of the preceding claims, characterized in that the gas flow i) contains ammonia, wherein the ammonia was preferably produced in a CO2-neutral manner; and / or ii) contains a solid as a source of a gaseous basic nitrogen compound, wherein the solid is preferably urea, wherein the gas stream is in particular an aerosol in which particles of urea are dispersed in the gas stream; and / or iii) contains a liquid as a source of a gaseous basic nitrogen compound, wherein the liquid is preferably N-he-containing water, wherein the gas stream is in particular an aerosol in which N-he-containing water is dispersed in the gas stream.
7. Method according to one of the preceding claims, characterized in that an internal pressure in the chamber is set in the range of 0.1 to 20 bar, preferably 0.2 to 10 bar, particularly preferably 0.4 to 5 bar, most preferably 0.6 to 2 bar, in particular 0.8 to 1.2 bar.
8. Method according to one of the preceding claims, characterized in that the condensation device contains or consists of at least one cold trap, preferably at least two cold traps, wherein preferably the at least one cold trap, more preferably the at least two cold traps, are each tempered to a temperature in the range of < 0 °C, preferably < -5 °C, more preferably < -10 °C, most preferably < -15 °C, more preferably < -18 °C.
9. Method according to one of the preceding claims, characterized in that the product gas which is formed from the gaseous product after isolation from the at least one compound is mixed with the gas stream which is directed into the chamber, preferably via a further fluid line.
10. Equipment for isolating at least one compound from polymer-containing waste, containing or consisting of: a) a chamber suitable for receiving polymer-containing waste that contains or consists of a polymer; b) a gas source for generating a gas stream, wherein the gas source contains a gas that contains an inert gas; c) a gas line which is fluidly connected to the gas source and the chamber; d) a condensation device; e) a further gas line which is fluidly connected to the chamber and the condensing device; and f) a control unit; where the control unit is configured to cause, - to create a chemically reducing atmosphere in the chamber and to heat the chamber to a temperature in the range of 300 °C to 800 °C, - to direct a gas stream containing an inert gas and chemically reducing agent from the gas source into the chamber via the gas line, in order to react the polymer-containing waste with the help of the gas stream to form a gaseous product, and - to direct the gaseous product from the chamber via the further gas line and into at least one condensation device in order to isolate the at least one compound from the gaseous product by condensation and to obtain the resulting gaseous product as product gas, characterized by the fact that the control unit is configured to cause the system to operate, i) to introduce a gas stream into the chamber via the gas line, containing a gaseous basic nitrogen compound and / or a source of a gaseous basic nitrogen compound capable of releasing a gaseous basic nitrogen compound in the heated chamber; and / or ii) before or after the introduction of polymer-containing waste into the chamber, to add a source of a gaseous basic nitrogen compound capable of releasing a gaseous basic nitrogen compound in the heated chamber, the system does not contain any of the following catalysts: aluminium oxide, calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, tin chloride, zinc chloride, aluminium chloride and zeolite.
11. System according to claim 10, characterized in that the chamber contains a polymer-containing waste, which preferably i) contains or consists of a polycondensed polymer, wherein the polycondensed polymer is preferably selected from the group consisting of polycarbonate, polyamide, polyester, polylactide and combinations thereof, wherein the polycondensed polymer is particularly preferably polycarbonate, in particular polycarbonate borate, which contains, has, or consists of bisphenol A monomers; and / or ii) contains or consists of a polyadduct, wherein the polyadduct is preferably a polyurethane; and / or iii) a polymer produced by chain polymerization comprising a cider, wherein the polymer produced by chain polymerization is preferably selected from the group consisting of acrylonitrile-butadiene-styrene copolymer, styrene-acrylonitrile copolymer, polystyrene, polyethylene, polypropylene and combinations and copolymers thereof; and / or iv) contains or consists of a naturally occurring polymer, wherein the naturally occurring polymer is preferably selected from the group consisting of cellulose, hemicellulose, lignin and combinations thereof; and / or v) contains urea, wherein the urea is preferably added to the polymer-containing waste, wherein the urea is particularly preferably added in the form of granules; and / or vi) contains an NH3-containing water, wherein the NH3-containing water is preferably sprayed onto the polymer-containing waste.
12. System according to one of claims 10 or 11, characterized in that the control unit of the system is configured to cause the chamber to be heated to a temperature in the range of 320 °C to 750 °C, preferably 340 °C to 700 °C, particularly preferably 360 °C to 600 °C, most preferably 380 °C to 580 °C, in particular 400 to 550 °C.
13. Plant according to one of claims 10 to 12, characterized in that the gas source for generating the gas flow i) the gaseous basic nitrogen compound in a concentration in the range of 1 to 50 vol.%, preferably in the range of 2 to 45 wt.%, particularly preferably in the range of 3 to 40 wt.%, most preferably in the range of 4 to 35 wt.%, in particular- especially in the range of 5 to 30 wt.%, in relation to the total volume of the gas flow; and / or ii) the source of the gaseous basic nitrogen compound contains an amount suitable for establishing in the chamber of the pyrolysis reactor a concentration of the gaseous nitrogen compound in the range of 1 to 50 vol.%, preferably in the range of 2 to 45 wt.%, particularly preferably in the range of 3 to 40 wt.%, most preferably in the range of 4 to 35 wt.%, and especially in the range of 5 to 30 wt.%, with respect to the total volume of the chamber; and / or iii) contains an inert gas selected from the group consisting of nitrogen, technical nitrogen, noble gases and combinations thereof; and / or iv) contains water vapor; and / or v) contains hydrogen or does not contain hydrogen.
14. Plant according to one of claims 10 to 13, characterized in that the control unit of the plant is configured to cause the plant to return recovered product gas to the chamber via a gas line as a gas stream, or as part of the gas stream, wherein the product gas preferably contains a gas selected from the group consisting of CO, CO2, CH4, H2, N2, C2 hydrocarbon, C3 hydrocarbon or combinations thereof.
15. Plant according to one of claims 10 to 14, wherein the gas source is used to generate the gas flow i) contains ammonia, wherein the ammonia is preferably produced in a CO2-neutral manner; and / or ii) contains a solid, wherein the solid is preferably urea, wherein the control unit of the plant is preferably configured to cause a gas stream from the gas source to be generated which is an aerosol in which particles of urea are dispersed in the gas stream; and / or iii) contains a liquid, wherein the liquid is preferably NH3-containing water, wherein the control unit of the plant is preferably configured to cause a gas stream to be generated from the gas source which is an aerosol in which NPh-containing water is dispersed in the gas stream.
16. System according to one of claims 10 to 15, characterized in that the control unit of the system is configured to cause the system to introduce the gas flow into the chamber in such a way that an internal pressure in the chamber is set in the range of 0.1 to 20 bar, preferably 0.2 to 10 bar, particularly preferably 0.4 to 5 bar, most preferably 0.6 to 2 bar, in particular 0.8 to 1.2 bar.
17. System according to one of claims 10 to 16, characterized in that the condensation device contains or consists of at least one cold trap, preferably at least two cold traps, wherein the control unit of the system is preferably configured to cause the system to temper the at least one cold trap, preferably the at least two cold traps, to a temperature in the range of < 0 °C, preferably < -5 °C, particularly preferably < -10 °C, most preferably < -15 °C, in particular < -18 °C.
18. Plant according to one of claims 10 to 17, characterized in that the control unit of the plant is configured to cause the plant to add a product gas, which is formed from the gaseous product after isolating the at least one compound, to the gas stream which is directed into the chamber, preferably via a further fluid line of the plant.