Improved Sustainability in Isocyanate and Polyurethane Production

Abstract

The present invention relates to a process for producing isocyanates and, optionally, polyurethanes, by at least synthesizing (1) phosgene (20) from carbon monoxide (21) and chlorine (22); reacting (2) phosgene (20) with a diamine (23) to produce a diisocyanate (24) and hydrogen chloride (25); providing a carbon dioxide gas stream (31); and cleaning (4) the carbon dioxide gas stream (31) with additional components, wherein the carbon dioxide is converted by a RWGS reaction (6) to produce carbon monoxide (21) and hydrogen (29), which are used as raw materials for polyurethane production, and optionally reacting (3) the diisocyanate (24) with a polyether polyol (35a) and / or polyester polyol (35b) to produce polyurethane (37).

Description

[Technical Field]

[0001] The present invention relates to a process for producing isocyanates and, optionally, polyurethanes, by synthesizing phosgene from carbon monoxide and chlorine, reacting the phosgene with a diamine to form a diisocyanate and hydrogen chloride, optionally reacting the diisocyanate with a polyether and / or polyester to form a polyurethane, providing a carbon dioxide gas stream, purifying the secondary component carbon dioxide gas stream, and subsequently reacting the carbon dioxide to produce carbon monoxide for use in the phosgene synthesis.

[0002] The present invention further relates to the use of polyurethane-containing waste materials (hereinafter also referred to as "waste polyurethane materials") for the production of isocyanates and optionally chemical raw materials for the subsequent production of polyurethanes, for example by pyrolysis, to produce carbon dioxide and hydrocarbons and possibly carbon monoxide and hydrogen, the carbon dioxide being reacted with hydrogen in a so-called reverse water gas shift reaction (hereinafter referred to as RWGS reaction) to produce carbon monoxide, which is converted via phosgene into isocyanates, which can then be further processed into new polyurethane materials.

[0003] The invention particularly relates to a low-emission process for the production of isocyanates using the RWGS reaction, as well as the provision of hydrogen from the electrolysis of water or from electrolysis for the production of chlorine, and the use of oxygen from the electrolysis of water for the combustion of polyurethane-containing materials to carbon dioxide and, optionally, for the combustion of pyrolysis residues obtained from the polyurethane-containing materials, and the use of the carbon dioxide obtained in each case as feedstock for the RWGS reaction. [Background technology]

[0004] Carbon monoxide, preferably produced from waste polyurethane materials, is reacted with chlorine to form phosgene, which is then reacted with amines to form isocyanates. These isocyanates can then be used to produce fresh polyurethane materials by reacting them with polyether polyols or polyester polyols. This completes one part of the value chain. Using CO2 and electricity from renewable energy for water electrolysis would enable the production of polyurethane raw materials more sustainably. This would significantly reduce the proportion of fossil carbon in polyurethanes.

[0005] Additionally, water electrolysis can produce the hydrogen needed to further hydrogenate nitro compounds to amines, which can then be converted to isocyanates with phosgene. Water electrolysis generates oxygen as a by-product at the anode. This oxygen can be used to burn polyurethane-containing waste and pyrolysis residues, which generates a high-concentration CO2 off-gas stream during combustion, making CO2 capture significantly more economical than burning polyurethane-containing waste with air. However, CO2 from other sources, such as the combustion of other wastes, can also be utilized. The CO2 is purified and fed to the RWGS reaction.

[0006] Polyurethanes, hereafter abbreviated as PU, are plastics obtained by the polyaddition reaction of polyols containing at least two hydroxyl groups with polyisocyanates. Linear polyurethanes are obtained by using diols and diisocyanates. 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 moieties used, thermosets, thermoplastics, or elastomers can be obtained. However, polyurethanes are also used as molding compounds for compression molding, as casting resins (isocyanate resins), for (textile) elastic fibers, as polyurethane coatings, and as polyurethane adhesives. It is also very easy to produce foams from polyurethanes.

[0007] Flexible PU foams are used for numerous purposes, especially as upholstery materials for furniture, car seats, etc., as mattress foam, as carpet backing, for textile lamination, as cleaning sponges, or as filter material.

[0008] Rigid PU foams are primarily used as thermal insulation materials, e.g. in buildings, refrigeration systems, hot and cold storage, and some piping systems (plastic jacketed composite pipes, flexible composite pipes).

[0009] Other relatively new applications of PU foam in automotive assembly include steering wheels, armrests, soft coatings on steering wheels, interior trim, dashboards, sound insulation, anti-rattle, seals and clear coatings on wood trim.

[0010] Once the use phase of products containing PU materials is over, 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 utilize the materials in an economically viable manner, i.e., to recover the polyols or polyisocyanates used from the PU materials in economical yields.

[0011] One approach to material recycling of PU is glycolysis, in which the urethane groups are reacted with glycols to produce carbamates and polyols. [ka]

[0012] The urethane groups can also be reacted with amines to form ureas and polyols. [ka] Summary of the Invention

[0013] The objective of the present invention was to find a more sustainable method for producing isocyanates, and ultimately polyurethanes, including recycling processes and completing the value chain. Until now, essential components for polyurethane production, such as carbon monoxide, hydrogen, or electricity for electrolysis operations such as water electrolysis and chloralkali electrolysis, have been produced from fossil fuels. For example, carbon monoxide and hydrogen are traditionally obtained from natural gas or coal by reforming processes, while chlorine is obtained by electrolysis using electricity produced using fossil fuels such as petroleum, coal, and natural gas.

[0014] The "sustainability" of a process is understood by those skilled in the art according to the definition of sustainability (sustainable development) established by the United Nations in the Brundtland Report of the World Commission on Environment and Development, which states that the current implementation of the process contributes little or nothing to impairing the ability of future generations to meet their own needs, particularly with regard to the use of resources such as fossil raw materials, and in particular with regard to the preservation of living space, for example the preservation of the Earth's atmosphere. It is therefore an object of the present invention to make the production of isocyanates and, optionally, polyurethanes, more sustainable than the production methods known from the prior art. The contribution of the production of isocyanates, and thus polyurethanes, to the reduction of the ability of future generations to meet their needs should be reduced or even avoided.

[0015] It is therefore an object of the present invention to reduce the use of fossil raw materials as reactants for isocyanate production, and potentially also for providing energy for isocyanate production, which in particular should further improve the carbon dioxide footprint of PU production in order to protect the Earth's atmosphere.

[0016] The present invention comprises at least the following steps: synthesizing phosgene from carbon monoxide and chlorine; reacting phosgene with a diamine to form a diisocyanate and hydrogen chloride; providing a CO2 gas stream; purifying the CO2 gas stream of secondary components, in particular nitrogen oxides, sulfur compounds, dust, water, oxygen and HCl, optionally by adsorption, gas scrubbing or catalytic treatment to obtain purified carbon dioxide; electrolyzing water into hydrogen and oxygen; providing a hydrogen stream and feeding it together with a purified CO gas stream to a RWGS reaction zone and reacting the reactants according to the principles of the RWGS reaction to form a product gas mixture comprising water vapor, CO and any by-products, particularly lower hydrocarbons, most preferably methane; separating the water vapor from the product gas mixture and recycling the water to the water electrolysis; separating unreacted carbon dioxide from the gas mixture of the RWGS reaction obtained from the separation, in particular by amine washing, and recycling the unreacted carbon dioxide to the RWGS reaction; separating the hydrogen that has not reacted in the RWGS reaction from the gas mixture of carbon monoxide and hydrogen obtained after the separation, in particular by using a cold box, and optionally recycling the hydrogen to the RWGS reaction or supplying it to the hydrogenation of dinitro compounds for the production of diamines as raw materials for diisocyanates, feeding the residual carbon monoxide from the separation to a phosgene synthesis; feeding hydrogen from water electrolysis, optionally together with unreacted hydrogen from the RWGS reaction, to the hydrogenation of nitro compounds for the production of diamines; Separation and purification of the hydrogen chloride produced in the isocyanate production, followed by oxidation of the hydrogen chloride in the form of reaction to chlorine and water in a thermal catalytic gas phase oxidation with oxygen and / or in the form of electrochemical oxidation of hydrogen chloride to chlorine and / or in the form of electrochemical oxidation of hydrogen chloride by HCl membrane electrolysis to chlorine and hydrogen, feeding the previously formed chlorine to the phosgene synthesis, optionally in parallel with a feed of fresh chlorine from the chloralkali electrolysis; The present invention relates to a method for producing isocyanates (and optionally polyurethanes) by

[0017] For the preparation of polyurethanes, the process of the present invention may additionally comprise the step of reacting a diisocyanate with a polyether polyol and / or a polyester polyol to form a polyurethane. Synthesis of phosgene (20) from carbon monoxide (21a) and chlorine (22) (1), reacting (2) phosgene (20) with diamine (23) to produce diisocyanate (24) and hydrogen chloride (25); reacting (3) a diisocyanate (24) with a polyether polyol (35a) and / or a polyester polyol (35b) to form a polyurethane (37); providing a CO2 gas stream (31); purifying (4) the CO gas stream (31) of secondary components, in particular nitrogen oxides, sulfur compounds, dust, water, oxygen and HCl, optionally by adsorption, gas scrubbing or catalytic treatment, to obtain purified carbon dioxide (31a); Electrolyzing (5) water (26) into hydrogen (29) and oxygen (27); providing a hydrogen stream (29a) and feeding it together with a purified CO gas stream (31a) to a RWGS reaction zone and reacting the reactants (6) according to RWGS principles to form a product gas mixture (39) comprising water vapor (26b), CO (21) and any by-products (32), particularly lower hydrocarbons, most preferably methane; separating (7) the water vapor (26b) from the product gas mixture (39) and recycling the water to the water electrolysis (5); Separating (8) the unreacted carbon dioxide (31b) from the gas mixture (39a) of the RWGS reaction (6) obtained from the separation (7), in particular by amine washing, and recycling the unreacted carbon dioxide (31b) to the RWGS reaction (6), separating (9) the hydrogen (29a) that did not react in the RWGS reaction (6) from the gas mixture (39b) of carbon monoxide (21a) and hydrogen (29c) obtained after the separation (8), in particular using a cold box, and optionally recycling the hydrogen (29c) to the RWGS reaction (6) or supplying the hydrogen (29c) to the hydrogenation (34) of dinitro compounds for the production of diamines (23) as raw materials for diisocyanates (24); feeding the residual carbon monoxide (21a) from the separation (9) to the phosgene synthesis (1); supplying hydrogen (29) from water electrolysis (5), optionally together with unreacted hydrogen (29c) from the RWGS reaction (6), to the hydrogenation of nitro compounds (34) for the production (2) of diamines (23); Separating and purifying (11) the hydrogen chloride (25) produced in the isocyanate production (2), followed by oxidation reactions (18) of the hydrogen chloride (25) in the form of a reaction in a thermal catalytic gas phase oxidation (16) with oxygen (27) to chlorine (22a) and water (26), and / or in the form of an electrochemical oxidation (12) of the hydrogen chloride (25) to chlorine (22b), and / or in the form of an electrochemical oxidation (17) of the hydrogen chloride (25) by HCl membrane electrolysis (17) to chlorine (22c) and hydrogen (29); Feeding the phosgene synthesis (1) with the previously formed chlorine (22a, 22b, 22c), optionally in parallel with the supply of fresh chlorine (22d) from the chloralkali electrolysis (14). is an embodiment of the method in the form of a method for producing isocyanates and polyurethanes by [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic diagram of the entire process including RWGS reaction, chlorine production, PU production, use and utilization of polyurethane material waste therefrom to obtain CO for RWGS reaction. [Figure 2] 1 is a schematic diagram of the entire process including RWGS reaction, hydrochloric acid electrolysis by diaphragm method (HCl-DIA) for chlorine production with optional PU production, use of polyurethane material, and utilization of polyurethane material waste therefrom to obtain CO for RWGS reaction. DETAILED DESCRIPTION OF THE INVENTION

[0019] All embodiments and definitions below apply equally to the above-described variants of the method of the invention.

[0020] "Lower hydrocarbons" is understood according to the invention to mean hydrocarbons having 1 to 8 carbon atoms.

[0021] "Amine scrubbing" of the product gases of the RWGS reaction is understood here to mean in particular the known scrubbing of gas mixtures according to the principle of chemisorption with amines such as monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA) or diglycolamine (DGA), whereby a purified gas mixture of high purity is achieved even at relatively low pressures in the absorption column.

[0022] "Renewable energy" is understood by those skilled in the art to mean energy from non-exhaustible sources such as wind energy, water energy or solar energy.

[0023] A preferred embodiment of the method of the present invention is characterized in that carbon dioxide formed from the utilization of waste polyurethane materials by combustion and / or pyrolysis is used for the synthesis of RWGS, and in this case, it is preferable if oxygen gas obtained from water electrolysis is used for combustion.

[0024] "Waste polyurethane material" may be generated from the use of commercially available polyurethanes, which polyurethanes have been produced from the diisocyanates provided by the method of the present invention. When waste polyurethane material of this nature is reused in the synthesis of the RWGS of the present invention, the process is said to be a "closed loop" process. However, it should be understood that waste polyurethane material from polyurethanes that were not produced from the diisocyanates from the method of the present invention can also be utilized in the synthesis of the RWGS of the present invention.

[0025] Very particularly preferred is a process in which the carbon dioxide used for the RWGS synthesis is formed from utilizing polyurethane material waste by burning it in the presence of a gas having a content of oxygen gas (O), said gas having an oxygen gas (O) content of at least 30% by volume, preferably at least 50% by volume, particularly preferably at least 95% by volume, very particularly preferably at least 99% by volume and most preferably at least 99.5% by volume.

[0026] The oxygen gas used for combustion can then preferably be obtained from water electrolysis.

[0027] For example, waste polyurethane materials are utilized by pyrolyzing them at high temperatures, optionally in the presence of a catalyst, to obtain carbon dioxide, optionally carbon monoxide, optionally hydrogen, optionally a mixture of aliphatic and aromatic low molecular weight hydrocarbons and nitrogen-containing hydrocarbons, and optionally a residue of higher molecular weight hydrocarbons. The mixture obtained by pyrolysis is then preferably purified to obtain a mixture of carbon dioxide, carbon monoxide, hydrogen gas, and other low molecular weight hydrocarbon compounds that are gaseous at normal conditions.

[0028] The combustion of the residue obtained in the pyrolysis and optionally other polyurethane material wastes can be carried out in particular with an oxygen-containing gas, in particular pure oxygen, to obtain a gas comprising carbon dioxide.

[0029] In a preferred embodiment of the novel process, RWGS synthesis uses carbon dioxide formed by burning waste polyurethane material with oxygen obtained from water electrolysis.

[0030] In a further preferred embodiment of the novel method, water electrolysis and / or electrochemical oxidation is carried out using electricity generated from renewable energy, in particular electricity optionally obtained by the use of wind, solar or hydroelectric power.

[0031] In another preferred embodiment of the novel method, water electrolysis and / or electrochemical oxidation is carried out using electricity from feedback energy obtained from the combustion of the used polyurethane material and / or the performance of the RWGS reaction.

[0032] A further alternative embodiment of the novel method is characterized in that the RWGS reaction is carried out using electricity generated from renewable energy sources, in particular electricity optionally obtained by using wind, solar or hydroelectric power.

[0033] In a further alternative embodiment of the novel process, the RWGS reaction is heated by feedback energy obtained from the combustion of waste polyurethane material. "Feedback energy" is understood by those skilled in the art to mean energy, in particular thermal energy, that is removed from a process step of the process of the invention (optionally converted into another form of energy, e.g., electricity) and reintroduced into another process step of the process of the invention.

[0034] In a preferred variant of the novel process, the RWGS reaction is heated by burning hydrocarbons from renewable hydrocarbon production, in particular by burning biomethane. Biomethane is understood here to mean methane obtained from biogas produced by fermentation of biomass. A further particularly preferred variant of the novel process is characterized in that the polyurethane material is recycled after use as polyurethane material waste, which is combusted to form carbon dioxide, which is used as feedstock for the purification stage.

[0035] The oxygen for combustion is preferably obtained from water electrolysis.

[0036] The use of electricity, preferably from renewable energy sources (preferably from wind, hydroelectric, or solar energy), further reduces CO2 emissions in the overall process. In a preferred new process, hydrogen produced in water electrolysis is optionally used in any purification step and / or in the hydrogenation of nitro compounds, where amines obtained in the hydrogenation of nitro compounds can be used in the production of isocyanates. Any abstracted hydrogen obtained in the new process is preferably used in the hydrogenation of nitro compounds, thereby obtaining amines as precursors of isocyanates.

[0037] The material cycle is further closed in a particularly preferred embodiment of the method of the present invention in recycling the polyurethane material after use as polyurethane material waste, and in combusting the polyurethane material waste to form carbon dioxide, which is used as feedstock in the purification step.

[0038] When PU materials are recycled at the end of their useful life, conventional separation processes are used to separate the composite materials in the waste. For example, the PU materials are subjected to automatic or manual coarse separation, followed by mechanical pulverization and, if necessary, further separation. The resulting PU materials are used as polyurethane waste feedstock for incineration or pyrolysis.

[0039] In the case of combustion, the polyurethane waste material is reacted with pure oxygen O2, which is released at the anode as a by-product of water electrolysis, for example. The heat of reaction generated during combustion can be used as feedback energy to generate steam and / or electricity. In particular, the heat can be used to drive the pyrolysis, and the generated electricity can be used for electrolysis. This further increases the overall efficiency of the novel process.

[0040] Additionally, the heat obtained during combustion can be used as feedback energy to heat the RWGS reaction, further improving the overall energy efficiency of the novel process compared to the prior art.

[0041] The CO2 derived from the combustion or pyrolysis of polyurethane material waste is obtained in a highly concentrated form and is fed to a purification stage before further use. In this stage, the by-products of combustion, such as sulfur compounds such as SO2, 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.

[0042] Combustion of polyurethane material waste with pure oxygen can be carried out, for example, in an atmosphere of pure oxygen and CO2 (recycled exhaust gas) according to a process known as oxy-fuel combustion. The resulting exhaust gas is not diluted with nitrogen from the air and consists essentially of CO2 and water vapor. The water vapor is easily condensed, producing highly concentrated CO2 (ideally approaching 100% concentration). The CO2 can then be purified, further processed, and optionally compressed and stored.

[0043] Additionally, a portion of the energy obtained from the pyrolysis or combustion of the polyurethane material can be converted into steam or electricity, which, as previously mentioned, can be used to operate the electrolysis, resulting in a more efficient process with less electrical energy consumption.

[0044] The purification of CO2 from combustion gases can be carried out using processes generally known from the prior art, which are explained below by way of example.

[0045] The first step here is, for example, the purification of combustion gas, the main component of which is CO2. The procedure for the purification of combustion gas is subdivided into different stages. The specific purpose of the purification is to provide CO2 for the downstream RWGS reaction free from interfering secondary components.

[0046] In the first stage, dust is removed from the combustion gas. This can be done using fabric or electrostatic filters. Acid gases, such as hydrogen chloride, formed from chlorine compounds present in the waste can then be removed. This is done, for example, using an off-gas scrubbing tower, which also cools the combustion gas and removes any additional dust or heavy metals present. Furthermore, the sulfur dioxide gas formed is also removed in a scrubbing circuit, for example by reacting it with hydrated lime to produce calcium sulfate. Nitrogen compounds can be removed from the combustion gas, for example, using zeolites containing catalysts or by adding urea or ammonia to convert nitrogen oxides back to nitrogen and water. To prevent the formation of ammonium salts, which can clog the catalyst pores, the catalyst is usually operated at temperatures above 320 °C. Similarly, N2 compounds can be removed by nitric acid washing or catalytic washing.

[0047] Drying and further purification of the CO can be carried out by known conventional methods, for example by treatment with concentrated sulfuric acid.

[0048] In the final purification step, activated carbon filters are used to remove any remaining organic matter and final metal residues still present in the flue gases. This can be done, for example, using activated carbon dust, which is metered into the flue gas or exhaust gas stream and then re-deposited together with the pollutants accumulated on the fiber filter. The spent carbon is then discharged and subjected to energy recovery (basically as described at https: / / www.ava-augsburg.de / umwelt / rauchgasreinigung / ).

[0049] The purification process performed on the combustion gas provides CO2 that can be used as a feedstock for the RWGS reaction.

[0050] In gas streams with relatively low CO2 concentrations, the CO2 can optionally be separated by an amine wash.

[0051] In the case of pyrolysis, it is not preferred to supply additional oxygen gas to the pyrolysis reaction space.The pyrolysis of the polyurethane material used can be preferably carried out as follows.

[0052] pyrolysis of the polyurethane material at an elevated temperature, optionally in the presence of a catalyst, to provide a mixture of optionally carbon dioxide, optionally carbon monoxide, optionally hydrogen, a mixture of aliphatic and aromatic low molecular weight hydrocarbons and nitrogen-containing hydrocarbons, and a residue of relatively high molecular weight hydrocarbon compounds; Optionally, purifying the resulting mixture of low molecular weight hydrocarbons 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 separating the resulting mixture by gas separation; The resulting residue and optionally further polyurethane material waste are combusted with an oxygen-containing gas, in particular pure oxygen, to obtain a gas comprising carbon dioxide.

[0053] The recycled and comminuted polyurethane waste material as described above can be fed to a pyrolysis step, which can be carried out with or without a catalyst.

[0054] The fractions produced during pyrolysis are gaseous, liquid, and solid, with the solid phase often consisting primarily of pyrolytic carbon. Liquid long-chain carbon compounds, including aromatic compounds such as toluene, benzene, and xylene, are preferably fed to a purification process, where they are separated or optionally further reacted with hydrogen, preferably hydrogen from water electrolysis, in a purification process, which also results in propene and ethene (as precursors for polyols and polyethers). The long-chain liquid hydrocarbon compounds can be separated and further processed. It is also possible to recycle aromatic compounds such as benzene or aniline, or, if present, isocyanates, as raw materials for appropriate syntheses.

[0055] Furthermore, the pyrolysis may be operated in such a way as to produce, in particular, larger amounts of carbon monoxide and possibly hydrogen, which can be separated off, for example, together with the short-chain hydrocarbon compounds in a purification step, or they can be separated off separately and then fed to a carbon monoxide-hydrogen separation for use.

[0056] The solid material obtained during pyrolysis consists mostly of carbon. This solid phase can be reacted with pure oxygen from water electrolysis. This also produces a highly concentrated stream of CO2, which is fed to the purification stage.

[0057] Another option for producing high-purity CO2 is to absorb CO2 in an alkaline solution, such as aqueous potassium hydroxide. This produces potassium bicarbonate, which can then be thermally decomposed back to CO2 and potassium hydroxide, using the heat generated by the thermal decomposition or combustion.

[0058] The purified CO2 is fed to the RWGS reaction.

[0059] The gas mixture removed from the RWGS reaction is cooled. Upon cooling, the reaction water is separated. This reaction water can be returned to the electrolysis of water as a raw material. After water separation, the gas is fed to CO2 separation.

[0060] CO2 separation is carried out, for example, by an amine scrubbing step, where CO2 is removed and the residual gas consisting of CO and H2 is fed to an H2 / CO gas separation unit. The resulting CO is then fed to phosgene synthesis, where it reacts with Cl2 to produce phosgene. The phosgene produced is fed to isocyanate production, where it reacts with amines to produce isocyanates and hydrogen chloride.

[0061] Either hydrogen obtained from water electrolysis or hydrogen obtained from H2 / CO separation can be fed to the hydrogenation of nitro compounds to amines and thus the production of isocyanates.

[0062] Therefore, an embodiment of the novel process in which at least a substream of carbon monoxide and / or hydrogen from the H2 / CO separation is fed to the RWGS reaction is preferred.

[0063] The isocyanate from the isocyanate production is reacted with a polyether polyol or polyester polyol to form a polyurethane material in a corresponding synthesis.

[0064] The novel process may also be preferably carried out so that a portion of the polyurethane material waste is fed directly to combustion rather than pyrolysis.

[0065] Hydrogen chloride (HCl) produced during isocyanate production can be fed to different HCl recycling units, such as HCl electrolysis using HCl membranes or gas diffusion electrodes or catalytic gas-phase oxidation. In the case of HCl electrolysis or gas-phase oxidation using gas diffusion electrodes, the required O2 can be obtained from water electrolysis.

[0066] The production of chlorine gas from electrochemical oxidation by the HCl-ODC electrolysis process (see US Pat. No. 6,022,634 A, WO 03 / 31690 A1 for suitable electrolysis cells), the production of chlorine gas from HCl membrane electrolysis (see EP 1,103,636 A1), the production of chlorine gas from thermal catalytic gas phase oxidation (see WO 2012 / 025483 A2), and the production of chlorine from chloralkali electrolysis (see WO 2009 / 007366 A2) are known to those skilled in the art. Reference is expressly and entirely made to the contents of the above cited documents in connection with the production of chlorine gas.

[0067] The isocyanate and polyether polyol, and optionally polyester polyol, can then be used to produce commercially required PU materials. The polyurethanes are then used in a variety of commercial applications. At the end of their useful life, the materials are fed to a recycling system where the PU materials are separated. The separated materials are then recycled for reuse as waste polyurethane materials in the form of pyrolysis and / or combustion.

[0068] This eliminates the need for additional fossil raw materials for isocyanate production, allowing polyurethane materials to be produced more sustainably.

[0069] The invention will now be explained in more detail by way of example with reference to the figures.

[0070] In the figure, Figure 1 is a schematic diagram of the entire process of RWGS reaction, chlorine production, PU production, use and utilization of polyurethane material waste from it to obtain CO2 for RWGS reaction.

[0071] In FIG. 1, the following reference numerals have the following meaning in each case: 1: Phosgene synthesis 2: Isocyanate production 3: Polyurethane manufacturing 4: CO2 gas purification 5: Water electrolysis 6: RWGS reaction (reverse water gas shift reaction) 7: Water separation 8:CO2 separation 9:H2 / CO separation 10: Utilization of polyurethane waste materials (38) by pyrolysis (10a) and / or combustion (10b) 10a: Pyrolysis 10b: Combustion 11: HCl gas separation / purification 12: Electrochemical oxidation of HCl by HCl-ODC electrolysis 13: Electricity and steam generation 14: Chloralkali electrolysis for the production of Cl2 15: Energy / Electricity from Steam (13) 16: Thermal catalytic gas-phase oxidation of HCl (Deacon) to produce Cl2 17: Cl2 production by electrochemical oxidation of hydrochloric acid using membrane electrolysis 18: Oxidative conversion of HCl to chlorine gas in the form of (12) and / or (16) and / or (17) 19: Fever 20: Phosgene 21: Carbon monoxide in the gas stream from the RWGS reaction 21a: Carbon monoxide from H2 / CO separation 22: Chlorine gas selected from 22a and / or 22b and / or 22c 22a: Chlorine gas from thermal catalytic gas-phase oxidation (16) 22b: Chlorine gas from electrochemical oxidation by HCl-ODC process (12) 22c: Chlorine gas from HCl membrane electrolysis (17) 22d: Chlorine from chloralkali electrolysis (14) (preferably using an oxygen depolarized cathode (ODC) with oxygen (27) supply) 23: Diamine 24: Diisocyanate 25: Hydrogen chloride 26:Water 26b:Water 27: Oxygen 27a: Oxygen 28: Optionally bio-natural gas and / or renewable energy for heating only 28a: Electricity from renewable sources 29: Hydrogen from water electrolysis 29a: Hydrogen from water electrolysis for RWGS reaction 29b: Unreacted hydrogen in the RWGS reaction 29c: Unreacted hydrogen from H2 / CO separation CO2 from 31:10 31a: Purified CO2 31b: Unreacted CO2 from CO2 separation 32: By-products from the RWGS reaction 33: CO2 from renewable sources 34: Hydrogenation of nitro compounds to produce diamines 35a: Polyether polyol 35b: Polyester polyol 37: Polyurethane material 38:10 Polyurethane material waste (Polyurethane material waste) 39: Product gas mixture from the RWGS reaction consisting of 21, 26b, CO2, 29b, and 32 The content of 39a:26b decreased. 39b:39a with reduced CO2 content 40: Nitro compounds Use of 80:37 and / or polyurethane materials from different commercial sources 90: Polyurethane materials - End-of-life recycling

[0072] FIG. 2 is a schematic diagram of the entire process including the RWGS reaction, hydrochloric acid electrolysis by diaphragm method (HCl-DIA) for chlorine production including optional PU production, the use of polyurethane material, and the utilization of polyurethane material waste therefrom to obtain CO for the RWGS reaction.

[0073] The reference numbering used in FIG. 2 is as defined in FIG.

[0074] 1 and 2 show a closed-loop variant of the process of the present invention. It should be appreciated that in one embodiment, the waste polyurethane material (38) feed can be made not from recycled polyurethane material (37) in the sense of a closed-loop process, but from polyurethane material produced from toluene-2,4-diisocyanate directly derived from raw materials from fossil sources without recycling. In this variant, steps (3), (35a), (35b) and (37) would be omitted in FIGS. 1 and 2. [Example]

[0075] Example 1 Low-emission production of toluene diisocyanate (TDI) according to the present invention, producing CO by RWGS, heating it with bionatural gas, recycling HCl by HCl gas-phase oxidation (Deacon), and providing H2 from water electrolysis. 17.84 t / h of CO2 and 0.81 t / h of H2 were introduced into the RWGS chamber (6), which was operated at a temperature of 802 °C. The product gas mixture (39) obtained from the RWGS reaction, consisting of CO (21), HO (26b), unreacted CO2, unreacted H2 (29a), and a small amount of by-products (32), mainly methane, was extracted and fed to water separation (7), yielding 7.3 t / h of water. This water (26b) was returned to water electrolysis (5). A total of 3.24 t / h of hydrogen was extracted from water electrolysis (5), which meant that an additional 21.86 t / h of water was added. The residual gas mixture (39a) from the RWGS was fed to CO2 separation (8). CO2 separation was performed by amine scrubbing, and the separated CO2 (31b) was recycled to the RWGS reaction. The energy required for CO2 separation from the resulting CO2-amine complex was obtained from the separation of water (7) from the RWGS gas (39). The CO2-free gas (39b) was fed to the H2 / CO separation (9). A so-called cold box was used for H2 / CO separation, in which the H2 / CO gas mixture was cooled and hydrogen and CO were separated. The separated hydrogen (29c) was returned to the RWGS (6). 11.35 t / h of CO from the H2 / CO separation (9) was fed to the phosgene synthesis (1). Here, CO reacted with 29.79 t / h of chlorine extracted from the HCl gas-phase oxidation (16). 40.15 t / h of phosgene was extracted from the phosgene synthesis (1) and reacted with 24.73 t / h of toluenediamine 23 in the isocyanate production stage (2) to produce 35.27 t / h of toluene diisocyanate (24). This resulted in 29.59 t / h of HCl gas (25), which, after purification by cryogenic distillation, was fed to the HCl gas-phase oxidation (16). In the HCl gas-phase oxidation (16), the HCl gas was reacted with oxygen (27) over a ruthenium oxide-based catalyst at approximately 300 °C to produce chlorine and HO. The required oxygen (27) was obtained from water electrolysis (5). For the closed-loop variant of the process of the invention, the resulting toluene diisocyanate (24) was reacted conventionally with a polyether polyol (35a) or polyester polyol (35b) to form a polyurethane material (37).

[0076] After the polyurethane material was used in various commercial applications (80), the resulting waste polyurethane material (38) could be recovered and recycled (90) for combustion (10b). Here, combustion was carried out using oxygen (27) from water electrolysis (5), thereby forming a highly concentrated CO2 off-gas stream (31). This CO2 stream (31) was fed to CO2 purification (4), where water, nitrogen oxides, and sulfur oxides from the combustion were removed. 17.84 t / h of CO2 was then fed to the RWGS (6). Of course, in one embodiment, the waste polyurethane material (38) feed could also be a polyurethane material produced from toluene-2,4-diisocyanate directly derived from fossil sources without recycling, rather than from recycled polyurethane material (37) in the sense of a closed-loop process. In this variant, steps (3), (35a), (35b), and (37) would be omitted in FIGS. 1 and 2. Hydrogen (29) was produced by water electrolysis using 45 MW of renewable energy. Water electrolysis (5) was performed at a current density of 8 kA / m 2 The alkaline water electrolysis was operated at a cell voltage of 2 V / electrolysis element. It was supplied with 45 MW and 21.86 t / h of water and 7.3 t / h of water from H2O separation (7). 3.24 t / h of H2 was extracted from the water electrolysis.

[0077] The RWGS reaction was operated at 802°C, a temperature generated by burning bio-natural gas.

[0078] Through the process of the present invention, 22% of the carbon present in TDI was replaced by non-fossil carbon sources. The use of renewable energy in water electrolysis made it possible to further reduce the CO2 footprint of phosgene produced from CO and Cl2.

[0079] Example 2 Low-emission production of toluene diisocyanate (TDI) according to the present invention, producing CO by RWGS, heating it with bionatural gas, recycling HCl by HCl membrane electrolysis, and providing H2 for the hydrogenation of dinitrotoluene from water electrolysis. 17.84 t / h of CO2 and 0.81 t / h of H2 were introduced into the RWGS chamber (6), operated at a temperature of 802 °C. The hydrogen was derived from HCl recycled by HCl membrane electrolysis. The product gas mixture (39) obtained from the RWGS reaction, consisting of CO (21), HO (26b), unreacted CO2, unreacted H2 (29a), and a small amount of by-products (32), mainly methane, was extracted and fed to water separation (7) to obtain 7.3 t / h of water. This water (26b) was returned to water electrolysis (5). A total of 2.43 t / h of hydrogen was extracted from the water electrolysis, which meant that an additional 14.56 t / h of water was added. The residual gas mixture (39a) from the RWGS was fed to CO2 separation (8). CO2 separation was performed by amine scrubbing, and the separated CO2 (31b) was recycled to the RWGS. The energy required for CO2 separation from the resulting CO2-amine complex was obtained from the separation of water (7) from the RWGS gas (39). The CO2-free gas (39b) was fed to the H2 / CO separation (9). A so-called cold box was used for H2 / CO separation, in which the H2 / CO gas mixture was cooled and hydrogen and CO were separated. The separated hydrogen (29c) was returned to the RWGS (6). 11.35 t / h of CO from the H2 / CO separation (9) was fed to the phosgene synthesis (1). Here, CO reacted with 29.79 t / h of chlorine extracted from the HCl membrane electrolysis (17). 40.15 t / h of phosgene was extracted from the phosgene synthesis (1) and reacted with 24.73 t / h of toluenediamine 23 in the isocyanate production stage (2) to produce 35.27 t / h of toluene diisocyanate (24). This resulted in 29.59 t / h of HCl gas (25), which was fed to the HCl membrane electrolysis (17) after purification by cryogenic distillation, absorption in water to produce 35% hydrochloric acid, and purification of the hydrochloric acid with activated carbon. Chlorine and hydrogen were extracted from the HCl membrane electrolysis. The hydrogen was purified and fed to the RWGS. The resulting toluene diisocyanate (24) was reacted conventionally with polyether polyol (35a) or polyester polyol (35b) to form polyurethane material (37).

[0080] After the polyurethane material has been used in various commercial applications (80), the resulting polyurethane material waste (38) can be recovered and recycled (90) for combustion (10b). Here, combustion was carried out using oxygen (27) from water electrolysis (5), thereby forming a highly concentrated CO2 off-gas stream (31). This CO2 stream (31) was fed to CO2 purification (4), where water, nitrogen oxides, and sulfur oxides from the combustion were removed. Then, 17.84 t / h of CO2 was fed to the RWGS (6).

[0081] Hydrogen (29) was produced by water electrolysis using 45 MW of renewable energy. Water electrolysis (5) was performed at a current density of 8 kA / m 2 The alkaline water electrolysis was operated at a cell voltage of 2 V / electrolysis element. It was supplied with 45 MW and 21.86 t / h of water and 7.3 t / h of water from H2O separation (7). 3.24 t / h of H2 was extracted from the water electrolysis.

[0082] The RWGS operates at 802°C, a temperature generated by burning bio-natural gas.

[0083] Through the process of the present invention, 22% of the carbon present in TDI was replaced by non-fossil carbon sources. The use of renewable energy in water electrolysis made it possible to further reduce the CO2 footprint of phosgene produced from CO and Cl2.

Claims

1. A method for producing an isocyanate and optionally a polyurethane, comprising at least the following steps: (1) synthesis of phosgene (20) from carbon monoxide (21a) and chlorine (22); reacting (2) phosgene (20) with diamine (23) to form diisocyanate (24) and hydrogen chloride (25); CO ２ providing a gas flow (31); Secondary component CO ２ purifying (4) the gas stream (31), optionally by adsorption, gas scrubbing or catalytic treatment, to obtain purified carbon dioxide (31a); Electrolysis (5) of water (26) into hydrogen (29) and oxygen (27), providing a hydrogen stream (29a) and ２ together with the gas stream (31 a) into a RWGS reaction zone and reacting the reactants (6) according to RWGS principles to form a product gas mixture (39) consisting of water vapor (26 b), CO (21) and any by-products (32); Separating (7) the water of steam (26b) from the product gas mixture (39) and recycling the water to the water electrolysis (5), Separating (8) unreacted carbon dioxide (31b) from the gas mixture (39a) of the RWGS reaction (6) obtained from the separation (7) and recycling said unreacted carbon dioxide (31b) to the RWGS reaction (6), separating (9) the hydrogen (29a) that has not reacted in the RWGS reaction (6) from the gas mixture (39b) of carbon monoxide (21a) and hydrogen (29c) obtained after the separation (8), and optionally recycling the hydrogen (29c) to the RWGS reaction (6) or supplying the hydrogen (29c) to the hydrogenation (34) of dinitro compounds for the production of diamines (23) as raw materials for diisocyanates (24); feeding the residual carbon monoxide (21a) from the separation (9) to a phosgene synthesis (1), feeding hydrogen (29) from water electrolysis (5), optionally together with unreacted hydrogen (29c) from the RWGS reaction (6), to the hydrogenation of nitro compounds (34) for the production (2) of diamines (23); Separation and purification (11) of the hydrogen chloride (25) produced in the isocyanate production (2), followed by oxidation reactions (18) of the hydrogen chloride (25) in the form of a reaction in a thermal catalytic gas phase oxidation (16) with oxygen (27) to chlorine (22a) and water (26) and / or in the form of an electrochemical oxidation (12) of the hydrogen chloride (25) to chlorine (22b) and / or in the form of an electrochemical oxidation (17) of the hydrogen chloride (25) by HCl membrane electrolysis (17) to chlorine (22c) and hydrogen (29), feeding the phosgene synthesis (1) with the previously formed chlorine (22a, 22b, 22c), optionally in parallel with the feeding of fresh chlorine (22d) from the chloralkali electrolysis (14), Method by.

2. Synthesis of phosgene (20) from carbon monoxide (21a) and chlorine (22) (1), reacting (2) phosgene (20) with diamine (23) to produce diisocyanate (24) and hydrogen chloride (25); reacting (3) a diisocyanate (24) with a polyether polyol (35a) and / or a polyester polyol (35b) to form a polyurethane (37); CO ２ Providing a gas flow (31); Secondary component CO ２ purifying (4) the gas stream (31), optionally by adsorption, gas scrubbing or catalytic treatment, to obtain purified carbon dioxide (31a); Electrolysis (5) of water (26) into hydrogen (29) and oxygen (27); providing a hydrogen stream (29a) and ２ feeding the reactants (6) together with the gas stream (31 a) into a RWGS reaction zone and reacting them according to RWGS principles to form a product gas mixture (39) consisting of water vapor (26 b), CO (21) and any by-products; separating (7) the water vapor (26b) from the product gas mixture (39) and recycling the water to the water electrolysis (5); Separating (8) unreacted carbon dioxide (31b) from the gas mixture (39a) of the RWGS reaction (6) obtained from the separation (7) and recycling the unreacted carbon dioxide (31b) to the RWGS reaction (6); separating (9) the hydrogen (29a) that did not react in the RWGS reaction (6) from the gas mixture (39b) of carbon monoxide (21a) and hydrogen (29c) obtained after the separation (8), and optionally recycling the hydrogen (29c) to the RWGS reaction (6) or supplying the hydrogen (29c) to the hydrogenation (34) of dinitro compounds for the production of diamines (23) as raw materials for diisocyanates (24); feeding the residual carbon monoxide (21a) from the separation (9) to a phosgene synthesis (1), Supplying hydrogen (29) from water electrolysis (5), optionally together with unreacted hydrogen (29c) from the RWGS reaction (6), to the hydrogenation of nitro compounds (34) for the production (2) of diamines (23), Separation and purification (11) of the hydrogen chloride (25) produced in the isocyanate production (2), followed by oxidation reactions (18) of the hydrogen chloride (25) in the form of a reaction in a thermal catalytic gas phase oxidation (16) with oxygen (27) to chlorine (22a) and water (26) and / or in the form of an electrochemical oxidation (12) of the hydrogen chloride (25) to chlorine (22b) and / or in the form of an electrochemical oxidation (17) of the hydrogen chloride (25) by HCl membrane electrolysis (17) to chlorine (22c) and hydrogen (29), Feeding the phosgene synthesis (1) with the previously formed chlorine (22a, 22b, 22c), optionally in parallel with the feeding of fresh chlorine (22d) from the chloralkali electrolysis (14).

10. The method of claim 1, wherein the method is for producing an isocyanate and a polyurethane by

3. 3. The method according to claim 1 or 2, wherein carbon dioxide (31) provided from the utilization (10) of waste polyurethane material (38) by combustion (10b) and / or pyrolysis (10a) is used in the RWGS synthesis (6).

4. Combustion (10b) is carried out with oxygen gas (O ２ 4. The method of claim 3, wherein the method is carried out using a gas having a hydroxyl group content of at least 30% by volume.

5. The gas used in the combustion (10b) contains at least 50% by volume of oxygen gas (O ２ 4. The method of claim 3, wherein the hydroxybenzoate has a hydroxybenzoate content of 1.

0.

6. 6. The method according to any one of claims 1 to 5, wherein the water electrolysis (5) and / or the electrochemical oxidation (12, 17) is carried out using electricity generated from renewable energy sources.

7. 7. The method according to any one of claims 1 to 6, wherein the water electrolysis (5) and / or electrochemical oxidation (12, 17) is carried out using electricity from feedback energy obtained from the combustion of waste polyurethane material and / or the performance of the RWGS reaction.

8. The method according to any one of claims 1 to 7, wherein the RWGS reaction (6) is carried out using electricity (28) generated from renewable energy.

9. The method according to any one of claims 1 to 8, wherein the RWGS reaction (6) is heated by feedback energy obtained from the combustion of waste polyurethane material (38).

10. 10. The method of any one of claims 1, 3 to 9, further comprising reacting (3) a diisocyanate (24) with a polyether polyol (35a) and / or a polyester polyol (35b) to form a polyurethane (37).

11. The method according to any one of claims 1 to 10, wherein the RWGS reaction (6) is heated by combustion of hydrocarbons from renewable sources.

12. 12. The method according to any one of claims 1 to 11, wherein the polyurethane material is recycled after use as waste polyurethane material (38), which is combusted to produce carbon dioxide (31), which is used as a feed material in the purification step (4).

13. The method according to any one of claims 1 to 12, wherein the CO 2 gas stream (31) is purified (4) by purification of secondary components including one or more selected from nitrogen oxides, sulfur compounds, dust, water, oxygen and HCl.

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