Method for recycling polyurethane material waste to produce chemical raw materials for the production of isocyanates and polyurethanes

Abstract

The present invention relates to a method for recycling polyurethane material waste (18a) for producing isocyanates (10a) and subsequently chemical raw materials for producing polyurethanes (16a), in which the method proceeds from the polyurethane material waste (18a) by pyrolysis (1) to generate carbon dioxide (1a) and hydrocarbons (1c), optionally converting the carbon dioxide (1a; 4a) to carbon monoxide (7b) and hydrogen (7a) by electrolysis (5), converting the carbon monoxide (7b; 7c) obtained via phosgene into isocyanates (10a), which can then be further processed into new polyurethane materials (16a).

Description

[Technical Field]

[0001] The present invention relates to a method for recycling polyurethane material waste to produce chemical raw materials for the production of isocyanates and subsequent polyurethanes, starting from polyurethane material waste, in which carbon dioxide and hydrocarbons and optionally carbon monoxide and hydrogen are produced by pyrolysis, the carbon dioxide is converted into carbon monoxide and optionally hydrogen by electrolysis, and the carbon monoxide obtained is converted via phosgene into isocyanates, which can be further processed into new polyurethane materials.

[0002] The present invention relates in particular to a method for the low-emission production of isocyanates and polyols, which involves the electrochemical conversion of carbon dioxide to carbon monoxide and optionally hydrogen, the production of oxygen, and the use of oxygen to incinerate a polyurethane-containing material to obtain carbon dioxide, and optionally to incinerate pyrolysis residues obtained from the polyurethane-containing material, and the use of the carbon dioxide obtained as a raw material for electrochemical CO reduction. The carbon monoxide produced is used for the production of isocyanates and, optionally, for the production of methanol as a precursor to polyalkylene oxides.

[0003] The resulting carbon monoxide and any CO2 produced are then optionally converted to methanol using hydrogen, which is further converted via a methanol-to-olefins (MTO) process, or specifically a methanol-to-propene (MTP) process, to obtain propene as the primary component. The propene is converted to propylene oxide, which is then converted to polyethers. Another portion of the carbon monoxide is reacted with chlorine to form phosgene, which is then reacted with amines to form isocyanates. Polyurethane materials can be produced again from the isocyanates and polyethers, meaning a large portion of the value chain is closed. When CO2 and renewable energy are used for electrolysis, polyurethane materials can be produced sustainably.

[0004] Furthermore, by integrating water electrolysis, the additional hydrogen needed for the hydrogenation of nitro compounds to amines can be generated, which can then be converted to isocyanates with phosgene. In both electrochemical CO2 reduction and water electrolysis, oxygen is produced as a by-product at the anode. This oxygen can be used to incinerate polyurethane-containing waste and pyrolysis residues, resulting in a highly concentrated CO2 off-gas stream during incineration, making CO2 capture significantly more economical than atmospheric incineration of polyurethane-containing waste. [Background technology]

[0005] Polyurethanes (hereinafter referred to as PUs) are plastics resulting from the polyaddition reaction of dialcohols or polyols with polyisocyanates. Diols and diisocyanates result in linear polyurethanes, while crosslinked polyurethanes can be produced by reacting triisocyanate-diisocyanate mixtures with triol-diol mixtures. The properties of PUs can vary widely. Depending on the degree of crosslinking and / or the isocyanate or OH components used, thermosets, thermoplastics, or elastomers can be obtained. However, polyurethanes are also used as molding compositions for compression molding, as casting resins (isocyanate resins), in elastic fibers (textiles), as polyurethane varnishes, and as polyurethane adhesives. It is also very easy to produce foams from polyurethanes.

[0006] Flexible PU foams are used for a wide variety of purposes, in particular as upholstery materials for furniture and automobile seats, as mattress foams, as carpet backing materials, for textile lamination, as cleaning sponges or as filter materials, for example.

[0007] PU rigid foam is mainly used for insulation in buildings, refrigeration equipment, hot and cold storage and some pipe systems (plastic jacketed composite pipes, flexible composite pipes), etc.

[0008] Other relatively new application areas for PU foams in vehicle construction include steering wheels, armrests, soft coatings for steering wheels, interior trim, dashboards, sound insulation, rattle protection, seals and clear coatings for wood trim.

[0009] At the end of the use phase of PU-containing products, they are usually disposed of, i.e., stored in landfills or incinerated in waste incineration plants. To date, it has not yet been possible to economically utilize the materials, i.e., to recover the polyols or isocyanates used from the PU materials in economical yields.

[0010] One approach to material recycling is glycolysis, in which urethane groups are reacted with glycols to form carbamates and polyols. [ka]

[0011] The urethane groups can also be reacted with amines to form ureas and polyols. [ka] Summary of the Invention

[0012] The objective of this invention was to find a sustainable alternative for isocyanate production, and ultimately for polyurethane production, including recycling processes and closing the value chain. To date, essential components for polyurethane production, such as carbon monoxide, hydrogen, and propene or ethene or their oxides for polyol production, have been produced from fossil fuels. For example, carbon monoxide and hydrogen are typically produced from natural gas and coal by reforming processes, while propene and ethene are produced from petroleum fractions.

[0013] Therefore, one object of the present invention is to reduce the material use of fossil raw materials for isocyanate production, and potentially also the energy use of fossil raw materials, with the intention of further improving the carbon footprint of PU production.

[0014] The present invention relates to a method for recycling waste containing polyurethane materials to produce chemical raw materials for the production of isocyanates and polyurethanes, which comprises: a) pyrolyzing a polyurethane material at elevated temperature, optionally in the presence of a catalyst, to obtain a mixture of aliphatic and aromatic low molecular weight hydrocarbons and nitrogen-containing hydrocarbons, with or without carbon dioxide, with or without carbon monoxide, with or without hydrogen, and a residue of high molecular weight hydrocarbons; b) optionally purifying the mixture of low molecular weight hydrocarbons obtained in step a) to obtain a mixture of gaseous and liquid hydrocarbons and a mixture of carbon dioxide, carbon monoxide and other gaseous low molecular weight hydrocarbon compounds, and separating the mixture obtained; and c) incinerating the residue obtained in step a) and optionally further incinerating the polyurethane material waste with an oxygen-containing gas, in particular pure oxygen, to obtain a carbon dioxide-containing gas; d) purifying the carbon dioxide obtained from step c) and optionally step a) from secondary components, in particular nitrogen oxides, sulfur compounds, dust, water, oxygen and hydrogen chloride, optionally by means of adsorption, membrane processes or gas scrubbing, or catalytic treatment, to obtain purified carbon dioxide; e) electrolyzing the purified carbon dioxide obtained in step d) to electrochemically convert the carbon dioxide, in particular at a gas diffusion electrode, to obtain a mixture of at least carbon monoxide, unconverted carbon dioxide and optionally hydrogen, f) separating unconverted carbon dioxide from the mixture obtained in step e) to obtain a mixture of at least carbon monoxide and optionally hydrogen and recycling the unconverted carbon dioxide to the electrolysis; g) optionally separating hydrogen that may be obtained from the mixture of carbon monoxide and optionally hydrogen obtained in step f), h) reacting the carbon monoxide obtained from step g) or f) with chlorine to form phosgene in the process for producing isocyanates; i) optionally reacting the isocyanate obtained from step h) with a polyether and optionally further with a polyester to obtain the finished polyurethane material. by.

[0015] The oxygen for the incineration in step c) is preferably obtained from water electrolysis.

[0016] The use of electricity from sustainable energy generation (wind, hydroelectric, solar) further reduces CO2 emissions in an integrated manner. In a preferred novel process, the hydrogen formed in the water electrolysis may optionally be used for the optional purification and / or hydrogenation of nitroaromatics, where the amines obtained in the hydrogenation of nitroaromatics can be used to produce isocyanates. The separated hydrogen obtainable in step g) of the novel process is preferably used for the hydrogenation of nitroaromatics. This allows the use of amines as precursors to isocyanates.

[0017] In a particularly preferred embodiment of the method according to the invention, the resource cycle is further closed in that the polyurethane material is recycled after its use to form polyurethane waste material, and the isolated polyurethane waste is used as feed material in step a) of the overall method.

[0018] In the purification according to step b), further gaseous low molecular weight hydrocarbon compounds are understood here to mean in particular optionally nitrogen-containing C1-C4 hydrocarbons.

[0019] When recycling PU materials after their useful life has ended, conventional separation processes are used to separate the composite materials in the waste stream. The PU materials are then roughly separated, either automatically or manually, and then mechanically shredded and, if necessary, further separated. The resulting PU materials are then used as feedstock for incineration or pyrolysis.

[0020] During incineration in step c), the PU material is reacted with pure oxygen O2, which is generated at the anode as a by-product of, for example, CO2 electrolysis or any water electrolysis. The reaction heat resulting from incineration in step c) can be used to generate steam and / or electric current. In particular, the heat can be used to power the pyrolysis in step a), and the generated electric current can be used in the electrolysis in step e). This further improves the efficiency of the novel overall process.

[0021] The CO resulting from the incineration in step c) is obtained in a highly concentrated form and is fed to purification in step d) before further use. In this process, the by-products of incineration, such as sulfur compounds such as SO, NO X Nitrogen compounds such as ammonium nitrate and residual organic matter, as well as dust and other compounds formed from components present in the PU material, are separated.

[0022] The incineration of PU materials with pure oxygen according to step c) can be carried out, for example, according to the process known as the oxyfuel combustion process in an atmosphere of pure oxygen and CO2 (recirculated flue gas). The resulting exhaust gas is not diluted with nitrogen present in the atmosphere and essentially consists of CO2 and water vapor. The water vapor can easily condense, resulting in the formation of a highly concentrated CO2 stream (ideally close to 100%). The CO2 can then be purified, further processed, optionally compressed, and stored.

[0023] Furthermore, part of the energy obtained from the pyrolysis of polyurethane material in step a) or from its incineration in step c) can be converted into steam or electricity, which can be used to power the electrolysis in step e), resulting in a more efficient process with less electrical energy consumption.

[0024] The purification of CO2 from combustion gases can in principle be carried out using methods known from the prior art, which are explained below by way of example.

[0025] First, the combustion gas, which is primarily composed of, for example, CO2, is purified. The assembly of a combustion gas purification system is divided into various stages. A particular challenge in the purification is to provide CO2 free from secondary components that would interfere with the subsequent successful electrochemical reduction of CO2 at a gas diffusion electrode, as described below.

[0026] In the first stage, dust is removed from the combustion gas. This can be done using fabric or electrostatic filters. Any acid gases present, such as hydrogen chloride formed from chlorine compounds present in the waste, can then be removed. Here, for example, an off-gas scrubber is used. The combustion gas is again cooled, and further dust and possibly heavy metals are removed. Furthermore, the formed sulfur dioxide gas is also separated in a scrubbing circuit and converted to gypsum, for example, using lime hydrate. Nitrogen compounds can be removed from the combustion gas, for example, over catalyst-containing zeolites or by adding urea or ammonia, which converts the nitrogen oxides back into nitrogen and water. To prevent the formation of ammonium salts that clog the catalyst pores, the catalyst is usually operated at temperatures above 320 °C (the principles are described, for example, at https: / / de.wikipedia.org / wiki / Rauchgasreinigung). Similarly, N2 compounds can be removed by scrubbing with nitric acid or a catalyst.

[0027] The CO2 can be dried and further purified by known conventional methods, for example, by treatment with concentrated sulfuric acid.

[0028] In the final purification stage, activated carbon filters are used to remove residual organic matter and final metal residues from the combustion gases. For this purpose, activated carbon in the form of dust can be metered into the combustion gas or flue gas stream and then deposited again on a fabric filter together with the accumulated pollutants. The spent carbon is then discharged and sent to energy recovery (as described in principle at https: / / www.ava-augsburg.de / umwelt / rauchgasreinigung / ).

[0029] After the purification process of the combustion gas has been carried out, CO2 is available which can be used as a feedstock in step e).

[0030] Optionally, CO2 can also be removed from gas streams containing low concentrations of CO2 by amine scrubbing.

[0031] The PU material recycled and ground as described above can be fed to pyrolysis in step a), which can be carried out either in the presence or absence of a catalyst.

[0032] The fractions produced during pyrolysis are gas, liquid, and solid, with the solid phase mainly consisting of pyrolytic carbon. Liquid long-chain carbon compounds containing aromatics, such as toluene, benzene, and xylene, are preferably fed to a purification process in step c). Here, the compounds can be separated or, if appropriate, further reacted with hydrogen, preferably hydrogen from water electrolysis, in the purification process, resulting in the production of propene and ethene (as precursors for polyols and polyethers). The long-chain liquid hydrocarbon compounds can be separated and further processed. Aromatic compounds, such as benzene or aniline, or isocyanates, if present, can also be reused as feedstocks in the appropriate synthesis.

[0033] Furthermore, the pyrolysis in step a) can optionally be operated in particular so as to produce larger amounts of carbon monoxide and possibly hydrogen, which can be separated together with the short-chain hydrocarbon compounds or separated separately and then fed to a carbon monoxide-hydrogen separation (7) and used, for example in a purification step.

[0034] The solid material obtained during pyrolysis in step a) consists mostly of carbon. This solid phase can be reacted with pure oxygen from CO2 electrolysis or the preferred water electrolysis. This also forms a highly concentrated CO2 stream, which is fed to the purification process.

[0035] Another possibility for producing high-purity CO2 is to absorb CO2 in an alkaline solution, such as aqueous potassium hydroxide. Here, potassium bicarbonate is formed, which can then be thermally decomposed back to CO2 and potassium hydroxide. Here, the heat generated from pyrolysis or incineration can be used.

[0036] The purified CO2 is preferably fed to the cathode space of the CO2 electrolysis according to step e).

[0037] Here, CO2 electrolysis may be high-temperature electrolysis, which is operated, for example, at temperatures above 600°C, optionally with the addition of water, for the production of synthesis gas. High-temperature electrolysis is known in principle and commercially available, for example, eCOs™ from Haldor Topsoe (https: / / www.topsoe.com / processes / carbon-monoxide / site-carbon-monoxide). During high-temperature electrolysis, oxygen is also produced at the anode. A disadvantage of known high-temperature electrolysis is its poor scalability, so for larger amounts of CO, for example, above 1 t / h, low-temperature electrolysis is currently still preferred.

[0038] When CO2 electrolysis is operated as low-temperature electrolysis, the electrolysis is carried out at a temperature below 150°C.

[0039] For all CO2 electrolyses, purified CO2 gas is fed to the cathode space.

[0040] In low-temperature electrolysis, CO2 is converted at a gas diffusion electrode, in particular to carbon monoxide and possibly hydrogen, while O2 or possibly chlorine can also be generated at the anode.

[0041] According to known principles, the MEA (membrane electrode assembly) concept can also be used in low-temperature electrolysis. In this case, a catalyst is applied to the membrane. A gas diffusion layer in front of it regulates the transport of gases and liquids. This can be done on both the anode and cathode sides. It is also possible to have the gas diffusion electrodes in direct contact with the membrane.

[0042] If chlorine is produced at the anode, this chlorine can be fed to the phosgene synthesis and thus to the isocyanate production as a further feedstock.

[0043] A gas diffusion electrode is placed, for example, in the cathode space. As in chlor-alkali electrolysis, this can be done in zero-gap as well as finite-gap configurations (COV Patent Application COV 101 186).

[0044] The cathode space, where the gas diffusion electrode operates, can be supplied with excess CO. Excess means introducing more CO than is required for stoichiometric conversion by the current flow. A gas mixture consisting of unreacted CO, CO, and H escapes from the cathode space. The entire gas mixture can be fed, for example, directly to a methanol synthesis stream (stream 23). Here, CO is converted to methanol with the aid of additional hydrogen, if necessary, and CO is converted to methanol with the aid of H. In this case, the additional hydrogen required can optionally be obtained from the above-mentioned water electrolysis. In a preferred embodiment of the novel process, the mixture of carbon monoxide and optionally hydrogen (6b) obtained in step f) is fed to a methanol synthesis stream (11). In this case, methanol 11a is also a precursor for polyether production.

[0045] If carbon monoxide is to be separated from the gas mixture removed from the cathode space during CO electrolysis, excess unconverted CO is first removed in step f) by gas separation (6), for example by amine scrubbing, and in step g) the residual gas consisting of CO and H is fed to a gas separation unit (7). The CO obtained in step g) is then fed to an isocyanate production (10), which reacts with chlorine, for example from the HCl recycle process (9), to form phosgene, which reacts with amines (8a), in particular with diamines, to form isocyanates, in particular diisocyanates, in the isocyanate production (10).

[0046] The hydrogen obtained from the water electrolysis 3 or from the gas separation (7) in step g) can be fed to the hydrogenation of nitroaromatics to amines (8a) and thus to the production of isocyanates (10) or to the production of methanol (11).

[0047] Therefore, one preferred embodiment of the novel process provides for feeding at least a partial stream of carbon monoxide (22) and / or hydrogen (21) from the gas separation (7) to the methanol synthesis (11).

[0048] In a further preferred embodiment of the novel process, the methanol 11a formed in the preferably used methanol synthesis is fed to a methanol to olefins (MTO) process (12), and the alkenes obtained therefrom are then fed to processes (13) or (14) for producing alkylene oxides, in particular propylene oxide (13a) and / or ethylene oxide (14a).

[0049] In a particularly preferred embodiment of the novel process, following this preferred production of alkylene oxides, propylene oxide (13a) and / or ethylene oxide (14a) from propylene oxide production (13) or ethylene oxide production (14) is fed to polyether production (15), and the polyethers (15a) obtained therefrom are used in a production process (16) for producing novel polyurethane materials.

[0050] This also makes the other raw material required for polyurethane production, the polyether, available in a particularly resource-saving manner.

[0051] In a preferred variant of the novel process, the gas mixture (19b) of gaseous hydrocarbons, carbon dioxide and carbon monoxide obtainable in the purification of step b) is also fed to the incineration (2) of step c).

[0052] Alternatively, in a preferred further variant of this novel process, the gas mixture (19b) of gaseous hydrocarbons, carbon dioxide and carbon monoxide obtainable in the purification of step b) is separated in a gas separation (30) into the components carbon dioxide (2b), carbon monoxide (7c) and hydrocarbons (30a), and the separated components (2b; 7c; 30a) are individually reused; in particular, the separated carbon dioxide (2b) is fed to the purification (4) of step d).

[0053] In a particularly preferred embodiment, carbon monoxide (7c) obtained from any gas separation 30 described above is fed to an isocyanate production (10), for example to an amine production as described above.

[0054] The novel process can also preferably be operated in such a way that part of the polyurethane material is fed directly to the incineration (2) in step c) instead of to the pyrolysis (1) in step a).

[0055] Also preferred is an embodiment of the novel process, in which at least a portion of the mixture (23) of carbon dioxide, carbon monoxide and optionally hydrogen obtained in step e) from the electrolysis (5) is fed directly to the above-mentioned methanol synthesis (11).

[0056] In a preferred variant of the novel process, the oxygen formed in the reaction by electrolysis (5) of carbon dioxide (4a) in step e) is at least partially supplied to the incineration (2) in step c).

[0057] In one preferred novel process, the overall mass balance is further improved by optionally feeding part of the carbon dioxide (6a) obtained in the separation (6) in step f) to the input stream (4a) of the electrolysis (5) in step e) and / or to the optional methanol synthesis (11).

[0058] Hydrogen chloride (HCl) produced during isocyanate production can be fed to low-temperature CO electrolysis (5) (not shown in Figure 1) or to a separate HCl recycle unit (9), such as HCl electrolysis with gas diffusion electrodes or catalytic gas-phase oxidation or an HCl diaphragm. For HCl electrolysis with gas diffusion electrodes or gas-phase oxidation, the required O can be obtained from low-temperature or high-temperature CO electrolysis (5) and / or water electrolysis (3) (not shown in Figure 1).

[0059] The methanol produced in a preferred embodiment of the novel process is converted to propene or ethene, for example, by the fundamentally known MTO (methanol to olefins) process (12). The by-products formed in this case can be fed to optional purification (19) in step b) and thus become available for further useful recycling. Propene and ethene from the MTO process (12) can be produced via known processes to produce propylene oxide (13a) and ethylene oxide (14a), from which, for example, polyethers (15a) can be produced. Subsequently, commercially required PU materials (16a) can be produced using isocyanates and polyethers, and optionally further polyesters. The polyurethanes are used in various applications (17). At the end of their useful life, the materials are fed to recycling (18), where the PU materials are separated. The separated materials are then fed again to pyrolysis (1) and / or incineration (2).

[0060] This means that no additional fossil raw materials are required to produce the isocyanates and the polyurethane material can be produced in a sustainable manner.

[0061] The present invention will now be described in detail by way of example with reference to the drawings. [Brief explanation of the drawings]

[0062] [Figure 1] Figure 1 shows an overview of the entire process including PU production, use and recycling.

[0063] In FIG. 1, the following reference numerals have the meaning indicated in each case: 1 Pyrolysis equipment 1a CO2 from pyrolysis (optionally, gas components are fed to CO2 separation) (Potassium hydroxide, KHCO3 production and its decomposition - not shown) 1b Residual solids from pyrolysis 1c Gas and liquid components from pyrolysis 1d CO-hydrogen mixture by thermal decomposition 2. Incineration of PU raw materials with pure oxygen 2a CO2 gas stream from incineration 2 3. Optional water electrolysis 3a Oxygen from water electrolysis, anode space 3b Hydrogen from water electrolysis, cathode space 4 CO2 purification 4a Purified CO2 gas stream 5. CO2 electrolysis 5a O2 from CO2 electrolysis, anode space 6. Removal of CO2 from CO, H2, and CO2 gas mixtures 6a CO2 gas stream from CO2 separation 6b CO / H2 separated from CO2 separation 7. CO2-H2 gas separation 7a Gas separation CO-H2 Hydrogen from 7 7b Gas Separation CO-H2 Carbon Monoxide from 7 7c Carbon monoxide from gas separation 30 8. Hydrogenation of nitroaromatic compounds 8a Amines 8b Nitroaromatics 9. HCl Recycling 9a Chlorine from HCl recycle 10 Isocyanate production 10a Isocyanate 11 Methanol synthesis 11a Methanol 12 Methanol to Olefins Process (MTO) 12a Propene 12b Ethene 13 Propylene oxide production 13a Propylene oxide 14 Ethylene oxide production 14a Ethylene oxide 15 Polyether Production 15a Polyether 16 Polyurethane material manufacturing 16a PU material 17 Market - Use of polyurethane materials until end of life 17a PU material used 18 Recycling of used polyurethane materials by isolating polyurethane components 18a Polyurethane materials for pyrolysis or incineration 19 Refining 19a Products from Refining 19b CO2 / CO and non-separated gaseous compounds 20 CO2 from CO2 purification 4 or CO2 removal 6 for methanol synthesis 11 21 Hydrogen from CO-H gas separation 7 or water electrolysis 3 22 CO from CO-H gas separation 7 (optionally from pyrolysis, not shown in FIG. 1) 23 CO, CO2, and H2 gas mixtures from low- or high-temperature CO2 electrolysis 30 Gas separation of CO2, hydrocarbons and hydrocarbons from refinery 19 30a Hydrocarbons from gas separation 30 [Example]

[0064] Example 1 Catalytic pyrolysis according to Figure 1, incineration of gas fraction A PU material with an elemental composition of 66.5 wt% carbon, 6.6 wt% hydrogen, 7.2 wt% nitrogen, and 18.8 wt% oxygen was used and subjected to catalytic pyrolysis 1. The PU material was pre-cut into small pieces using a cutting mill, and then the material was hot-pressed and chopped again so that all particles had a diameter of less than 4 mm. This material 18a was mixed with the zeolite catalyst HZSM-5 in a 1:1 weight ratio and fed to a fluidized bed. The fluidized bed already contained pre-packed catalyst HZSM-5. The fluidized bed was operated at 600 °C.

[0065] From pyrolysis 1, 25.0 wt.% of the material fed was obtained as solid residue 1b (mainly carbon). Furthermore, 37% of the mass used was removed as gaseous products, and 35% was removed as liquid material 1c. The gaseous compounds consisting of CO2, CO, methane, ethene, ethane, propene, and propane were fed directly to incineration 2 with pure oxygen without purification 19.

[0066] 2,838 t / a of PU material is recycled from refrigerator PU insulation. 1,516 t / a is fed to pyrolysis 1 and 1,322 t / a to incineration 2. From pyrolysis 1 and incineration 2, 5,580 t / a of CO2 1a; 2a is fed to electrolysis 5 after CO2 purification 4. A gas mixture 23 of 3,505 t / a of CO and 135 t / a of H2 can be extracted from electrolysis 5. Furthermore, 3,081 t / a of O2 5a is removed from the anode space of the electrolysis and fed to incineration 2 as PU material 18a or residue 1b.

[0067] The electrolysis 5 is conveniently operated in accordance with European Patent Application No. 18195279.7, Example 1, and each contains 2.5 m 2 160 elements (CO2GDE) with an electrode area of ​​1.5 m are required, which are connected together to form the electrolyzer. The operating time is 8500 h per year. The electrolysis operates at a cell voltage of 3.17 V, with a current yield of 68% for CO2. 32.722 MWh of renewable energy, specifically wind power, is utilized.

[0068] Gaseous compounds 19b from pyrolysis 1 are fed to incineration 2. Solid compounds 1b from pyrolysis 1 are also fed to incineration 2.

[0069] From the liquid fraction of pyrolysis 1, 182 t / a of heterocycles, 139 t / a of a benzene / toluene mixture, 27 t / a of a xylene and naphthalene mixture and 182 t / a of aniline can be obtained by further purification 19.

[0070] The gas mixture 23 produced from the low temperature electrolysis 5 is fed to an amine wash, and unreacted CO2 is separated from the mixture 23 and returned to the electrolysis 5. The CO2-depleted gas 6b, consisting of CO and H2, is fed to a CO-H2 separation in the form of a cold box 7, where CO and H2 are separated. CO2 7b reacts with Cl2 9a coming from the HCl recycle 9 to form phosgene, which reacts with aniline to form isocyanate 10a.

[0071] A partial stream of the gas mixture 23a from electrolysis 5, consisting of CO2, CO, and H2, is fed to methanol synthesis after drying; the hydrogen required for the reaction, 3b, is also obtained from water electrolysis 3. Next, methanol 11a is converted by MTO process to propylene 12a and by-product ethylene 12b, which are further converted to propylene oxide 13a and ethylene oxide 14a, respectively, in stages 13 and 14. The missing propylene and ethylene are supplied from other production processes. In polyether production 15, polyol 15a required for PU material production is produced from alkyl oxides. New PU material 16a is produced from isocyanates 10a and polyol 14a. After use as used PU material 17a, it can be fed to recycling 18 for the production of PU feedstock 18a for incineration 1 / pyrolysis 2, thus closing the value-added cycle.

Claims

1. 1. A method for recycling waste containing polyurethane materials (18a) for producing chemical raw materials for the production of isocyanates and polyurethanes, comprising: a) pyrolysis (1) of a polyurethane material (18a) at high temperature, optionally in the presence of a catalyst, to obtain a mixture (1c) of low molecular weight aliphatic and aromatic hydrocarbons and nitrogen-containing hydrocarbons, with or without carbon dioxide (1a), with or without carbon monoxide, with or without hydrogen (1d), and to obtain a residue (1b) of high molecular weight carbon compounds; b) optionally purifying (19) the mixture of low molecular weight hydrocarbons (1c) obtained in step a) to obtain a mixture of gaseous and liquid hydrocarbons (19a) and a mixture of carbon dioxide and carbon monoxide, hydrogen and other gaseous hydrocarbon compounds (19b), and separating the mixture (19b) obtained in a gas separation 30; c) incinerating (2) the residue (1b) obtained in step a) and optionally also the polyurethane material waste (18a) with an oxygen-containing gas (3a) to obtain a gas (2a) containing carbon dioxide; d) purifying (4) the carbon dioxide (1a) and (2a) obtained from step c) and optionally step a) from secondary components, optionally by means of adsorption, gas scrubbing or catalytic treatment, to obtain purified carbon dioxide (4a); e) electrolysis (5) of the purified carbon dioxide (4a) obtained in step d) to obtain a mixture (23) of at least carbon monoxide, unconverted carbon dioxide and optionally hydrogen, f) separating (6) the unconverted carbon dioxide (6a) from the mixture (23) obtained in step e) to obtain a mixture (6b) of at least carbon monoxide and optionally hydrogen, and recycling the unconverted carbon dioxide (6a) to the electrolysis (5); g) optionally separating (7) hydrogen (7a) obtainable from the mixture of carbon monoxide and optionally hydrogen (6b) obtained in step f), h) reacting carbon monoxide (7b) or (6b) obtained from step g) or f) with chlorine (9a) to form phosgene in a process (10) for producing isocyanates (10a), i) optionally reacting (16) the isocyanate (10a) obtained from step h) with a polyether (15a) and optionally further with a polyester to obtain the finished polyurethane material (16a); The method according to claim 1.

2. Oxygen (3a) for incineration (2) in step c) is obtained by water electrolysis (3) or CO ２ 2. The method according to claim 1, characterized in that it is obtained from electrolysis (5).

3. 3. The method according to claim 2, characterized in that the hydrogen (3b) formed in the water electrolysis (3) can be used in the purification (19) and / or hydrogenation (8) of nitroaromatic compounds, wherein the amines (8a) obtained in the hydrogenation of nitroaromatic compounds (8) are used in the isocyanate production (10).

4. 4. The process according to claim 1, wherein the separated hydrogen (7a) obtainable in step g) is used for the hydrogenation of nitroaromatic compounds (8).

5. 5. The method according to any one of claims 1 to 4, characterized in that the polyurethane material (16a) is recycled after its use (17) to form a polyurethane waste material (17a), and the isolated polyurethane waste is used as feed material (18a) in step a).

6. 6. The process according to claim 1, wherein the mixture (6b) of carbon monoxide, optionally carbon dioxide and optionally hydrogen obtained in steps e) and f) is fed to a methanol synthesis (11).

7. 7. The method according to claim 1, wherein at least a partial stream of carbon monoxide (22) and / or hydrogen (21) from the gas separation (7) or the water electrolysis (3) is fed to the methanol synthesis (11).

8. 8. A process according to claim 6 or 7, characterized in that the methanol (11a) from the methanol synthesis (11) is fed to a methanol to olefins (MTO) process (12) and the alkenes obtained therefrom are then fed to a process (13) or (14) for producing alkylene oxides.

9. The method according to claim 8, characterized in that the alkylene oxide is propylene oxide (13a) and / or ethylene oxide (14a) from propylene oxide production (13) or ethylene oxide production (14), and the alkylene oxide is supplied to polyether production (15), and the polyether (15a) obtained therefrom is used in a production method (16) for producing the polyurethane material (16a).

10. 10. The method according to claim 1, wherein the gas mixture (19b) of carbon dioxide, carbon monoxide and gaseous hydrocarbons and optionally hydrogen obtained in the purification (19) of step b) is fed to incineration (2) in step c).

11. 10. The process according to claim 1, wherein the gas mixture (19b) obtained in the purification (19) of step b) is separated in a gas separation (30) into the components carbon dioxide (2b), carbon monoxide (7c) and hydrocarbons (30a), and the components (2b; 7c; 30a) are individually reused, and optionally carbon dioxide (2b) is fed to the purification (4) of step d).

12. 12. The method according to claim 11, characterized in that carbon monoxide (7c) from the gas separation (30) is fed to the isocyanate production (10).

13. 13. The method according to any one of claims 1 to 12, characterized in that part of the polyurethane material (18a) is fed directly to the incineration (2) in step c).

14. 14. The method according to claim 1, wherein at least a portion of the mixture (23) of carbon dioxide, carbon monoxide and optionally hydrogen obtained in step e) from the electrolysis (5) is fed directly to the methanol synthesis (11).

15. 15. The method according to any one of claims 1 to 14, characterized in that during the electrolysis (5) of carbon dioxide (4a) in step e), oxygen (5a) is formed, which is at least partly supplied to the incineration (2) in step c).

16. 16. The method according to any one of claims 1 to 15, characterized in that part of the carbon dioxide (6a) obtained in the separation (6) of step f) may be fed to the input stream (4a) of the electrolysis (5) of step e) and / or to the optional methanol synthesis (11).

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