METHOD FOR THE RECYCLING OF POLYURETHANE MATERIAL WASTE FOR PRODUCING CHEMICAL FEEDSTOCK FOR THE PRODUCTION OF ISOCYANATES AND POLYURETHANES

Abstract

The invention relates to a method for recycling polyurethane material waste (18a) for producing chemical feedstock for the production of isocyanates (10a) and then polyurethanes (16a), in which method, proceeding from polyurethane material waste (18a), carbon dioxide (1a) and hydrocarbons (1c) are generated by pyrolysis (1), the carbon dioxide (1a; 4a) is converted by electrolysis (5) into carbon monoxide (7b) and hydrogen (7a), as appropriate, the carbon monoxide (7b; 7c) obtained is converted via phosgene to isocyanate (10a) and the isocyanate (10a) can be further processed into new polyurethane material (16a).

Claims

1.-16. (canceled)

17. A method for recycling waste containing polyurethane material for producing chemical feedstock for the production of isocyanates and polyurethanes by a) pyrolysis of the 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 nitrogenous hydrocarbons, with or without carbon dioxide, with or without carbon monoxide, with or without hydrogen, and a residue of higher molecular weight carbon compounds, b) optionally refining 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 and carbon monoxide, hydrogen and other gaseous hydrocarbon compounds, and separation of the resulting mixtures in a gas separation; c) incinerating the residue obtained in step a) and optionally further polyurethane material waste with oxygen-containing gas, in particular with pure oxygen, to obtain gas containing carbon dioxide, d) purifying the carbon dioxide, obtained from step c) and possibly from step a), of secondary constituents, in particular nitrogen oxides, sulfur compounds, dust, water, oxygen and HCl, optionally by means of adsorption, gas scrubbing or catalytic treatment to obtain purified carbon dioxide, e) electrolysis of the purified carbon dioxide obtained in step d), in particular electrochemical conversion of the carbon dioxide at a gas diffusion electrode, to obtain a mixture of at least carbon monoxide, unconverted carbon dioxide and possibly hydrogen, f) separating the unconverted carbon dioxide from the mixture obtained in step e) to obtain a mixture of at least carbon monoxide and possibly hydrogen and recycling the unconverted carbon dioxide to the electrolysis, g) optionally separating the hydrogen optionally obtained from the mixture of carbon monoxide and possibly hydrogen obtained in step f), h) reacting the carbon monoxide obtained from step g) or f) with chlorine to form phosgene in a process for producing isocyanate, i) optionally reacting the isocyanate obtained from step h) with polyethers and optionally additionally with polyester to give a finished polyurethane material.

18. The method as claimed in claim 17, wherein the oxygen for the incineration in step c) is obtained from water electrolysis or the CO.sub.2 electrolysis.

19. The method as claimed in claim 18, wherein the hydrogen formed in the water electrolysis is optionally used in the refining and/or in a hydrogenation of nitroaromatics, wherein the amines obtained in the hydrogenation of nitroaromatics are used in the isocyanate production.

20. The method as claimed in claim 17, wherein the separated hydrogen possibly obtained in step g) is used in the hydrogenation of nitroaromatics.

21. The method as claimed in claim 17, wherein 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).

22. The method as claimed in claim 17, wherein the mixture of carbon monoxide, possibly carbon dioxide and possibly hydrogen obtained in step e) and f) is fed to a methanol synthesis.

23. The method as claimed in claim 17, wherein at least partial streams of the carbon monoxide and/or of the hydrogen from the gas separation or the water electrolysis are fed to a methanol synthesis.

24. The method as claimed in claim 22, wherein the methanol from the methanol synthesis is fed to a methanol to olefin process and the alkenes obtained therefrom are then fed to a process for producing alkylene oxides.

25. The method as claimed in claim 24, wherein the propylene oxide and/or the ethylene oxide from the propylene oxide production or from the ethylene oxide production are fed to a polyether production and the polyether obtained therefrom is used in the production process for producing new polyurethane material.

26. The method as claimed in claim 17, wherein the gas mixture of carbon dioxide, carbon monoxide and gaseous hydrocarbons and possibly hydrogen obtained in the refining in step b) is fed to the incineration in step c).

27. The method as claimed in claim 17, wherein the gas mixture obtained in the refining in step b) is separated in a gas separation into the components: carbon dioxide, carbon monoxide and hydrocarbons and the components are reused individually, in particular in that the carbon dioxide is fed to the purification in step d).

28. The method as claimed in claim 27, wherein the carbon monoxide from the gas separation is fed to the isocyanate production.

29. The method as claimed in claim 17, wherein part of the polyurethane material is fed directly to the incineration in step c).

30. The method as claimed in claim 17, wherein at least part of the mixture of carbon dioxide, carbon monoxide and possibly hydrogen obtained in step e) from the electrolysis is fed directly to the methanol synthesis.

31. The method as claimed in claim 17, wherein oxygen is formed during the electrolysis of carbon dioxide in step e), which is at least partially fed to the incineration in step c).

32. The method as claimed in claim 17, wherein part of the carbon dioxide obtained in the separation in step f) is optionally fed into the input stream of the electrolysis in step e) and/or to the optional methanol synthesis.

Description

[0072] In the FIGURES below:

[0073] FIG. 1 shows a schematic overview of the overall method including PU production, use and recycling

[0074] In FIG. 1, the following reference numbers have the meaning on the right in each case: [0075] 1 pyrolysis unit [0076] 1a CO.sub.2 from pyrolysis (optionally, the gaseous components are fed to a CO.sub.2 separation (potassium hydroxide, KHCO.sub.3 formation and decomposition thereof—not shown) [0077] 1b residual solid from the pyrolysis [0078] 1c gaseous and liquid components from the pyrolysis [0079] 1d CO-hydrogen mixture from the pyrolysis [0080] 2 incineration of PU material with pure oxygen [0081] 2a CO.sub.2 gas stream from incineration 2 [0082] 3 optional water electrolysis [0083] 3a oxygen from water electrolysis, anode space [0084] 3b hydrogen from water electrolysis, cathode space [0085] 4 CO.sub.2 purification [0086] 4a CO.sub.2 purified gas stream [0087] 5 CO.sub.2 electrolysis [0088] 5a O.sub.2 from the CO.sub.2 electrolysis, anode space [0089] 6 CO.sub.2 removal from CO, Hz, CO.sub.2 gas mixture [0090] 6a CO.sub.2 gas stream from CO.sub.2 separation [0091] 6b CO/Hz separated from CO.sub.2 separation [0092] 7 CO.sub.2—H.sub.2 gas separation [0093] 7a hydrogen from gas separation CO—H2 7 [0094] 7b carbon monoxide from gas separation CO—H2 7 [0095] 7c carbon monoxide from gas separation 30 [0096] 8 hydrogenation of nitroaromatics [0097] 8a amines [0098] 8b nitroaromatics [0099] 9 HCl recycling [0100] 9a chlorine from HCl recycling [0101] 10 isocyanate production [0102] 10 a isocyanates [0103] 11 methanol synthesis [0104] 11a methanol [0105] 12 methanol to olefin process (MTO) [0106] 12a propene [0107] 12b ethene [0108] 13 propylene oxide production [0109] 13a propylene oxide [0110] 14 ethylene oxide production [0111] 14a ethylene oxide [0112] 15 polyether production [0113] 15a polyether [0114] 16 polyurethane material production [0115] 16a PU material [0116] 17 market—use of polyurethane materials until end of use [0117] 17a PU material used [0118] 18 recycling of used polyurethane material with isolation of the polyurethane component [0119] 18a polyurethane material for pyrolysis or incineration [0120] 19 refining [0121] 19a products from refining [0122] 19b CO.sub.2/CO and non-separated gaseous compounds [0123] 20 CO.sub.2 from CO.sub.2 purification 4 or CO.sub.2 removal 6 for methanol synthesis 11 [0124] 21 hydrogen from CO—H.sub.2 gas separation 7 or water electrolysis 3 [0125] 22 CO from the CO—H.sub.2 gas separation 7 (optionally from pyrolysis, not shown in FIG. 1) [0126] 23 CO, CO.sub.2, H.sub.2 gas mixture from the low-temperature or high-temperature CO.sub.2 electrolysis [0127] 30 gas separation for CO.sub.2, CO, hydrocarbons from refining 19 [0128] 30a hydrocarbons from gas separation 30

EXAMPLE

Example 1 Pyrolysis with Catalyst, Incineration of the Gaseous Fraction According to FIG. 1

[0129] A PU material having an elemental composition of 66.5% by weight carbon, 6.6% by weight hydrogen, 7.2% by weight nitrogen and 18.8% by weight oxygen was used and treated in a catalytic pyrolysis 1. The PU material was previously cut into small pieces in a cutting mill, then the material was hot-pressed and shredded again so that all the particles had a diameter of less than 4 mm. This material 18a was mixed with a zeolite-based catalyst HZSM-5 in a ratio by weight of 1:1 and fed to a fluidized bed. The fluidized bed already contained pre-filled catalyst HZSM-5. The fluidized bed was operated at 600° C.

[0130] From pyrolysis 1, 25.0% by weight of the material fed in was obtained as solid residue 1b (predominantly carbon). Furthermore, 37% of the mass used was removed as gaseous products and 35% as liquid materials 1c. The gaseous compounds consisting of CO.sub.2, CO, methane, ethene, ethane, propene, propane were fed directly to incineration 2 with pure oxygen without refining 19.

[0131] 2838 t/a PU material from the recycling of PU insulation material from refrigerators are used. 1516 t/a are fed to pyrolysis 1 and 1322 t/a to incineration 2. From pyrolysis 1 and incineration 2, 5580 t/a CO.sub.2 1a; 2a are fed to electrolysis 5 after purification 4 of the CO.sub.2. A gas mixture 23 of 3505 t/a CO and 135 t/a H.sub.2 can be extracted from electrolysis 5. Furthermore, 3081 t/a O.sub.2 5a are removed from the anode space of the electrolysis and fed to the incineration 2 of the PU material 18a or the residue 1b.

[0132] The electrolysis 5 is expediently operated in accordance with the European patent application number 18195279.7, example 1. 160 elements of 2.5 m.sup.2 electrode area each (CO.sub.2 GDE) are required, which are connected together to form an electrolyser. The operating time is 8500 hours per year. The electrolysis is operated at a cell voltage of 3.17 V with a current yield with respect to CO of 68%. 32 722 MWh of renewable energy, especially wind power, are used.

[0133] The gaseous compounds 19b from pyrolysis 1 are fed to incineration 2. The solid compounds 1b from pyrolysis 1 are also fed to an incineration 2.

[0134] From the liquid fraction of pyrolysis 1, 182 t/a heterocycles, 139 t/a benzene/toluene mixture, 27 t/a xylene and naphthalene mixture and 182 t/a aniline can be obtained with an additional refining 19.

[0135] The gas mixture 23 produced from the low-temperature electrolysis 5 is fed to an amine scrubber and the unreacted CO.sub.2 is separated from the mixture 23 and returned to the electrolysis 5. The gas 6b freed of CO.sub.2 consisting of CO and H.sub.2 is fed to a CO—H.sub.2 separation in the form of a cold box 7 in which CO and H.sub.2 are separated. The CO 7b is reacted with the Cl.sub.2 9a originating from the HCl recycling 9 to form phosgene and this is reacted with aniline to form isocyanate 10a.

[0136] A partial stream of the gas mixture 23a from the electrolysis 5 consisting of CO.sub.2, CO and H.sub.2 is fed to the methanol synthesis after drying and the hydrogen 3b required for the reaction is also obtained from the water electrolysis 3. The methanol 11a is then converted to propylene 12a and the by-product ethylene 12b by means of the MTO process, which are further converted into propylene oxide 13a and ethylene oxide 14a in stages 13 and 14 respectively. Any missing amounts of propylene/ethylene are supplied from other manufacturing processes. In the polyether production 15, the polyols 15a required for the PU material production are produced from the alkyl oxides. New PU material 16a is produced from the isocyanates 10a and the polyols 14a. After use as used PU material 17a, this can be fed to recycling 18 for the production of PU raw material 18a for incineration 1/pyrolysis 2, thus closing the value-added cycle.