Method for producing at least one polyisocyanate from CO2

Abstract

The invention relates to a method for producing polyisocyanates from CO2 and to a production unit for carrying out the method. Furthermore, the invention relates to a polyisocyanate and a polyisocyanate obtained according to the method of the invention.

Description

[0001] The present invention relates to a process for preparing polyisocyanates from CO2 and a production unit for carrying out this process. Furthermore, the present invention relates to a polyisocyanate and a polyisocyanate obtained by the process according to the invention.

[0002] Diisocyanates and polyisocyanates are used in particular for the production of polyurethanes and coatings. The most widely used are aromatic diisocyanates and polyisocyanates, such as TDI and PMDI. In addition, diisocyanates and polyisocyanates of both aliphatic and cycloaliphatic nature are also known. Their preparation is usually carried out by phosgenation of the corresponding amines. Phosgene-free routes (for example via reductive or oxidative carbonylation) are also known, but play only a minor role technically. The preparation of phosgene is usually carried out from chlorine and CO in a heterogeneous catalytic gas-phase reaction. In the phosgenation of amines, HCl is formed as a by-product. In addition to its use in other processes (such as oxychlorination), processes for recovering chlorine from HCl are also known (electrolysis or Deacon process).

[0003] In the course of developing sustainable preparation processes, efforts are being made to use renewable raw materials, recycled materials or CO2 itself. For example, WO 2021 / 089737 discloses a process for preparing isocyanates by phosgenation of the corresponding amines, in which phosgene is produced from CO and chlorine and the CO is obtained from CO2 by the reverse water gas shift (RWGS) reaction. The hydrogen required for this is provided by water electrolysis, whereby the excess hydrogen can also be used for amine production by hydrogenation of nitro components.

[0004] WO 2020 / 239716 discloses the pyrolysis of polyurethane waste, in which synthesis gas (CO / H2), CO2, low molecular weight hydrocarbons and residues are obtained. The CO2 is converted to CO and oxygen in electrolysis, whereby the oxygen is used to combust the above-mentioned residues and possibly an additional amount of polyurethane waste. The resulting CO2 is also fed into the above-mentioned CO2 electrolysis. The resulting CO is used again for the synthesis of phosgene for the production of isocyanates. However, there is still a need to provide increasingly sustainable processes for preparing polyisocyanates.

[0005] Accordingly, it is an object of the present invention to provide an improved process for preparing polyisocyanates which exhibits good performance while showing improved sustainability compared to processes already known in the art. In fact, it is an object of the present invention to provide a process for preparing polyisocyanates which has a reduced environmental impact while being cost-effective.

[0006] Accordingly, the present invention relates to a process for preparing at least one polyisocyanate R(-NCO)x from CO2, the process comprising

[0007] (i) Provide a stream S1 containing CO2;

[0008] (ii) Provide a stream S2 containing H2;

[0009] (iii) Pass a portion of S1 obtained according to (i) and a portion of S2 obtained according to (ii) into a reaction unit RU RWGS and bring them into contact to carry out the reverse water gas shift reaction, thereby obtaining a stream S3 containing CO and H2 and a stream SH containing H2O;

[0010] (iv) Prepare at least one polyamine R(-NH2)x, where x = 2 or greater, and this preparation includes

[0011] (iv.1) Pass a portion of S3 obtained according to (iii), or a portion of S1 and a portion of S2 obtained respectively according to (i) and (ii) into an alcohol production unit PU1 and bring the CO and H2 contained in the said portion of S3 into contact in PU1, or bring S1 and S2 into contact in PU1, thereby obtaining a stream SM containing an alcohol having 1 to 4 carbon atoms; or

[0012] (iv.1’) Pass a portion of S1 and a portion of S2 obtained respectively according to (i) and (ii) into an alkane production unit PU2 and bring the said portion of S1 into contact with the said portion of S2 in PU2, thereby obtaining a stream SM’ containing C1-C4 alkanes;

[0013] (iv.2) Pass a portion of SM obtained according to (iv.1), or a portion of SM’ obtained according to (iv.1’) into an aromatic production unit PU MTA and cause the alcohol having 1 to 4 carbon atoms contained in SM, or the C1-C4 alkanes contained in SM’ to react in PU MTA thereby obtaining a stream SA containing at least one aromatic compound;

[0014] (iv.3) React SA obtained according to (iv.2) with nitric acid in a nitration reaction unit RU N thereby obtaining a stream SN containing the corresponding at least one nitrated aromatic compound;

[0015] (iv.4) Pass SN obtained according to (iv.3) into an amine production unit APU and cause the at least one nitrated aromatic compound contained in SN to react in APU, thereby obtaining a stream S4 containing at least one polyamine R(-NH2)x;

[0016] (v) Prepare phosgene, and this preparation includes

[0017] (v.1) Provide a stream S5 containing Cl2;

[0018] (v.2) Pass a part of S3 into a purification unit to obtain a stream S CO containing CO and a stream S CH containing H2 that is CO - lean compared to this part of S3;

[0019] (v.3) Pass at least a part of S CO obtained according to (v.2) into a reaction unit RU P for phosgene preparation and bring the said at least part of S CO into contact with S5 obtained according to (v.1) in RU P to obtain a stream S6 containing phosgene;

[0020] (vi) Pass S4 containing at least one polyamine R(-NH2)x obtained according to (iv.4) into the reaction unit RU and react S4 with the phosgene contained in S6 obtained according to (v.3) to obtain a stream SP containing the at least one polyisocyanate R(-NCO)x.

[0021] In the context of the present invention, the CO2 provided in (i) can be obtained from any method known to the person skilled in the art. For example, at least a part of the CO2 provided as S1 in (i) can be obtained from the combustion of methane and / or from the recycling of waste.

[0022] In this regard, the waste can contain one or more of polyurethane, polyurethane - urea, polyethylene, polypropylene, polystyrene, polyamine. For example, the waste contains polyurethane. For example, at least a part of the CO2 contained in S1 can be obtained from the pyrolysis of waste (such as waste polyurethane and / or waste polyurethane - urea).

[0023] Preferably, at least a part of the CO2 contained in S1 is obtained by hydrolysis, hydroglycolysis, hydroaminolysis or hydroammonolysis of one or more of polyurethane and polyurethane - urea.

[0024] Preferably, the reverse water - gas shift reaction carried out in RU RWGS according to (iii) is carried out at a temperature in the range of 500 °C to 1200 °C, more preferably in the range of 700 °C to 1100 °C, more preferably in the range of 800 °C to 1000 °C, more preferably in the range of 850 °C to 1000 °C, more preferably in the range of 900 °C to 1000 °C.

[0025] Preferably, according to (iii) in RURWGS The reverse water-gas shift reaction carried out in [RU] is carried out at a pressure in the range of 0.5 to 20 bar (absolute pressure), more preferably in the range of 2 to 18 bar (absolute pressure), even more preferably in the range of 2 to 15 bar (absolute pressure).

[0026] Preferably, according to (iii) in RU RWGS The molar ratio of H2 to CO2 in the reverse water-gas shift reaction carried out in [RU] is in the range of 0.5:1 to 10:1, more preferably in the range of 0.8:1 to 5:1, even more preferably in the range of 1:1 to 3:1, even more preferably in the range of 1.5:1 to 3:1, even more preferably in the range of 2:1 to 3:1.

[0027] The reverse water-gas shift reaction is preferably carried out according to methods known in the art, such as those defined in the following documents: E. Rezaei, S. Dzuryk “Techno-economic comparison of reverse watergas shift reaction to steam and dry methane reforming reactions for syngas production [Reverse water-gas shift reaction and steam and dry methane reforming reactions for syngas production of technical and economic comparison]”, Chemical Engineering Research and Design [Chemical Engineering Research and Design], Volume 144 (2019), S. 354-369, EP 2175986, CN 103183346 and US 8946308.

[0028] Preferably, (iii) includes

[0029] (iii.1) Passing a part of S1 obtained according to (i) and a part of S2 obtained according to (ii) into the reaction unit RU RWGS and bringing them into contact to carry out the reverse water-gas shift reaction, thereby obtaining a stream S13 containing CO, CO2, H2 and H2O;

[0030] (iii.2) Cooling the stream S13 obtained according to (iii.1) in the condensation unit CU, thereby obtaining a gaseous stream S3 containing CO and H2 that is leaner in water than S13, and a liquid stream SH containing H2O; or

[0031] (iii.2’) includes

[0032] (iii.2’.1) Cool the stream S13 obtained according to (iii.1) in the condensation unit CU to obtain a gaseous stream S23 containing CO and H2 that is lean in water compared to S13, and a liquid stream SH containing H2O;

[0033] (iii.2’.2) Feed the S23 obtained according to (iii.2’.1) into an amine scrubbing unit to remove CO2, thereby obtaining a gaseous stream S3 containing CO and H2 that is lean in CO2 compared to S23.

[0034] Preferably, (iii) includes

[0035] (iii.1) Feed at least a portion of S1 obtained according to (i) and at least a portion of S2 obtained according to (ii) into the reaction unit RU RWGS and bring them into contact to carry out the reverse water gas shift reaction, thereby obtaining a stream S13 containing CO, CO2, H2 and H2O;

[0036] (iii.2) Cool the stream S13 obtained according to (iii.1) in the condensation unit CU to obtain a gaseous stream S3 containing CO and H2 that is lean in water compared to S13, and a liquid stream SH containing H2O.

[0037] Alternatively, preferably (iii) includes

[0038] (iii.1) Feed at least a portion of S1 obtained according to (i) and at least a portion of S2 obtained according to (ii) into the reaction unit RU RWGS and bring them into contact to carry out the reverse water gas shift reaction, thereby obtaining a stream S13 containing CO, CO2, H2 and H2O;

[0039] (iii.2’) includes

[0040] (iii.2’.1) Cool the stream S13 obtained according to (iii.1) in the condensation unit CU to obtain a gaseous stream S23 containing CO and H2 that is lean in water compared to S13, and a liquid stream SH containing H2O;

[0041] (iii.2’.2) Feed the S23 obtained according to (iii.2’.1) into an amine scrubbing unit to remove CO2, thereby obtaining a gaseous stream S3 containing CO and H2 that is lean in CO2 compared to S23.

[0042] Preferably, the condensation unit includes condensation means and one or more heat exchangers suitable for cooling and condensation, such as plate type, shell and tube type and air coolers.

[0043] Preferably, the removal of CO2 in the amine scrubbing unit is carried out in the presence of any suitable material that selectively chemisorbs CO2. Preferably, such a material is one or more of NaOH and amines such as monoethanolamine (MEA), diethanolamine (DEA), or methyldiethanolamine (MDEA).

[0044] Preferably, the amine scrubbing unit includes an absorption column and a desorption column.

[0045] Preferably, at least a portion of the CO2 removed from S13 or S23 by the amine scrubbing unit, more preferably the CO2, is recycled as part of S1.

[0046] Preferably, the weight ratio of CO to H2 in S3 is in the range of 1:1 to 30:1, preferably in the range of 2:1 to 20:1, more preferably in the range of 5:1 to 15:1.

[0047] Preferably, 25 to 100 weight-% of S3 consists of CO and H2.

[0048] When S3 is obtained from (iii.2’.2), more preferably 85 to 100 weight-%, more preferably 90 to 100 weight-%, more preferably 95 to 100 weight-%, more preferably 98 to 100 weight-% of S3 consists of CO and H2.

[0049] Alternatively, when S3 is obtained from (iii.2), more preferably 30 to 95 weight-%, more preferably 40 to 85 weight-% of S3 consists of CO and H2.

[0050] Preferably, according to (iv.1), 75 to 95 weight-%, preferably 85 to 93 weight-% of S3 is fed into the alcohol production unit PU1.

[0051] Preferably, PU1 includes an alcohol production reactor, wherein (iv.1) includes feeding a portion of S3 into PU1 and contacting the CO and H2 contained in said portion of S3 with a catalyst in the alcohol production reactor at a temperature in the range of 150 °C to 500 °C, more preferably in the range of 180 °C to 320 °C, more preferably in the range of 200 °C to 300 °C, more preferably in the range of 205 °C to 280 °C, thereby obtaining a stream SM containing alcohols having 1 to 4 carbon atoms.

[0052] Preferably, the contact of CO and H2 with the catalyst in the alcohol production reactor according to (iv.1) is carried out at a pressure up to 380 bar (absolute), more preferably up to 300 bar (absolute), more preferably in the range of 30 to 120 bar (absolute), more preferably in the range of 50 to 100 bar (absolute).

[0053] Preferably, the catalyst contained in the alcohol production reactor comprises at least copper, zinc oxide and alumina.

[0054] In the context of the present invention, the alcohol having 1 to 4 atoms is selected from the group consisting of ethanol, methanol, propanol and butanol.

[0055] Preferably, in the SM, the alcohol having 1 to 4 atoms is methanol or ethanol, more preferably methanol.

[0056] Preferably, the stream SM is further purified, more preferably by passing the stream into a purification unit. Such processes are well known in the art and are disclosed in the documents listed below.

[0057] Preferably, in (iv.1), methanol is produced from a part of S3 according to methods known in the art, such as those disclosed in the following documents: DE 69808983, EP 3901126, EP 3441381, EP 0336378, EP2100869, EP 2281792, EP 0128400 and J. Ott et al. "Methanol" in "Ullmann's Encyclopedia of industrial chemistry", Wiley-VCH Verlag GmbH & Co KGaA, Weinheim, 2012.

[0058] Alternatively, preferably, in (iv.1), methanol is produced from a part of S1 and a part of S2 according to methods known in the art, such as those disclosed in the following documents: Sofiane Arab: “Development of a process for methanol synthesis from CO2”. PhD, Université Nancy, 2014, Laetitia Angelo “Development of catalysts for the carbon dioxide hydrogenation into methanol”, PhD Laboratoire des matériaux, surfaces et procédés pour la catalyse, 2014, EP 0011150 and J. Ott et al. “Methanol” in “Ullmann’s Encyclopedia of industrial chemistry”, Wiley-VCH Verlag GmbH & Co KGaA, Weinheim, 2016, section 5.3.1.

[0059] Preferably, PU2 includes an alkane production reactor, wherein (iv.1’) includes introducing a part of S1 and a part of S2 into PU2 and bringing the CO2 contained in the part of S1 and the H2 contained in the part of S2 into contact in the alkane production reactor PU2 at a temperature in the range of 250 °C to 600 °C, more preferably in the range of 280 °C to 500 °C, even more preferably in the range of 300 °C to 400 °C, thereby obtaining a stream SM’ containing C1-C4 alkanes.

[0060] Preferably, the weight ratio of CO2 to H2 in (iv.1’) is in the range of 1:1 to 1:20, preferably in the range of 1:1.5 to 1:10, more preferably in the range of 1:2 to 1:5.

[0061] In the context of the present invention, the C1-C4 alkanes are selected from the group consisting of ethane, methane, propane and butane.

[0062] Preferably, in SM’, the C1-C4 alkanes are methane or ethane, more preferably methane.

[0063] Preferably, the stream SM' containing C1-C4 alkanes is obtained via the Sabatier reaction.

[0064] Preferably, (iv.2) includes

[0065] introducing a portion of SM obtained according to (iv.1) or a portion of SM' obtained according to (iv.1') into the aromatic production unit PU MTA and bringing it into contact with the catalyst in the aromatic production unit to obtain a stream SA containing at least one aromatic compound, where the aromatic compound is selected from the group consisting of benzene, toluene, and xylene, more preferably benzene or toluene.

[0066] Preferably, PU MTA includes at least one aromatic conversion reactor, preferably any reactor suitable for heterogeneous gas-phase reactions, such as a fixed-bed reactor and a fluidized-bed reactor.

[0067] Preferably, when performing (iv.1), (iv.2) includes

[0068] (iv.2.1) introducing a portion of SM obtained according to (iv.1) into the at least one aromatic conversion reactor, more preferably into at least one methanol-to-aromatic compound conversion reactor;

[0069] (iv.2.2) bringing the stream SM into contact with the catalyst in the at least one reactor, more preferably at a temperature in the range of 250°C to 750°C, more preferably in the range of 300°C to 600°C, to obtain a stream SA1 containing a mixture of water and aromatic compounds, and these aromatic compounds are benzene, toluene, and xylene;

[0070] (iv.2.3) introducing the stream SA1 obtained according to (iv.2.2) into the separation unit SU to obtain a stream SA containing benzene or toluene.

[0071] Optionally, SA1 further contains C1-C4 alkanes, more preferably methane or ethane. Preferably, the method further includes introducing the alkanes into a second aromatic conversion unit after separating them from the aromatic compounds obtained according to (iv.2.2) to obtain aromatic compounds.

[0072] Preferably, the pressure in the reactor in (iv.2.2) is in the range of 0.5 to 30 bar (absolute pressure), more preferably in the range of 0.75 to 10 bar (absolute pressure), more preferably in the range of 0.8 to 6 bar (absolute pressure).

[0073] Preferably, the separation unit SU used in (iv.2.3) is one or more of a distillation column, an adsorption column, and phase separation.

[0074] Optionally, the method further comprises demethylating the xylene separated from SA1 to obtain benzene or toluene. Such processes are known to those skilled in the art, as disclosed, for example, in US 2786876.

[0075] Preferably, the stream SA comprising at least one aromatic compound is obtained by methods well known in the art, such as those disclosed in EP 0090284, CN 104496743, CN 104549481, EP 2188234, W.O. Haag, R.M. Lago and P.G. Rodewald, J. Mol. Catal. [Journal of Molecular Catalysis] 17, 161 (1982), R. Le Van Mao, P. Levesque, B. Sjariel and D.T. Nguyen, Can. J. Chem. Eng. [Canadian Journal of Chemical Engineering] 64, 462 (1986) and G. Pop and co-workers, Ind. Eng. Chem. Prod. Res. Dev. [Industrial and Engineering Chemistry Product Research and Development] 25, 208 - 213 (1986); or such as those disclosed in US11084764, EP 2595943, US 2011060176 and Ismagilov, Z.R. et al., “Direct Conversion of Methane on Mo / ZSM-5 Catalysts to Produce Benzene and Hydrogen: Achievements and Perspectives [Direct conversion of methane on Mo / ZSM-5 catalysts to produce benzene and hydrogen: achievements and perspectives],” Energy & Environmental Science [Energy and Environmental Science] 1, 5 (2008), 526 - 541.

[0076] Preferably, when performing (iv.1’), (iv.2) comprises

[0077] (iv.2.1’) passing a portion of SM’ obtained according to (iv.1’) into the at least one aromatic conversion reactor, more preferably at least one methane to aromatic compound conversion reactor;

[0078] (iv.2.2’) contacting the stream SM’ with the catalyst in the reactor, more preferably at a temperature in the range of 600 °C to 1000 °C, more preferably in the range of 625 °C to 900 °C, more preferably in the range of 650 °C to 850 °C, to obtain a stream SA1’ comprising a mixture of aromatic compounds, which aromatic compounds are benzene, toluene and xylene;

[0079] (iv.2.3’) The material flow SA1’ obtained according to (iv.2.2’) is introduced into the separation unit SU’ to obtain a material flow SA containing benzene or toluene.

[0080] Preferably, (iv.2.2’) is carried out at a pressure in the range of 1 to 20 bar (absolute pressure), more preferably in the range of 2 to 10 bar (absolute pressure), and even more preferably in the range of 2 to 6 bar (absolute pressure).

[0081] Preferably, (iv.3) includes

[0082] reacting SA obtained according to (iv.2) with nitric acid in the nitration reaction unit RU N to obtain a material flow SN containing the corresponding at least one nitrated aromatic compound, wherein more preferably, the at least one nitrated aromatic compound is selected from the group consisting of nitrobenzene and dinitrotoluene.

[0083] Preferably, (iv.3) includes reacting SA containing benzene obtained according to (iv.2) with nitric acid, more preferably with a mixture of nitric acid and sulfuric acid, in the nitration reaction unit RU N to obtain a material flow SN containing nitrobenzene.

[0084] Preferably, the nitration reaction for preparing nitrobenzene operating in RU N is an adiabatic reaction, more preferably at a temperature in the range of 50 °C to 150 °C.

[0085] Preferably, the nitration reaction operates in RU N with an excess of benzene to prepare nitrobenzene.

[0086] Preferably, the nitration reaction for preparing dinitrotoluene operating in RU N is carried out in two steps. In the first step, the nitration reaction is an isothermal or adiabatic reaction to obtain mononitrotoluene, and in the second step, the nitration reaction is an isothermal reaction to obtain dinitrotoluene.

[0087] Preferably, the nitration reaction operates in RU N at a temperature in the range of 30 °C to 120 °C to prepare dinitrosotoluene.

[0088] For example, nitration can be carried out by methods known in the art, such as those disclosed in the following: G. Booth “Nitro compounds, Aromatic [Nitro compounds, aromatic]” Volume 24 in _“Ullmann’s Encyclopedia of industrial chemistry [Ullmann's Encyclopedia of Industrial Chemistry]”, Wiley-VCH Verlag GmbH & Co KGaA [Wiley-VCH Verlag GmbH & Co KGaA], Weinheim [Weinheim], 2012, H. Hermanns et al. “Chapter 21 - Industrial nitration of toluene to dinitrotoluene [Industrial nitration of toluene to dinitrotoluene]” in L.F. Albright (ed.) and “Nitration - Recent Laboratory and Industrial Developments [Nitration - Recent Laboratory and Industrial Developments]”, ACS Symposium Series 623 [ACS Symposium Series 623], American Chemical Society [American Chemical Society], Washington [Washington], DC [District of Columbia] 1996.

[0089] Preferably, (iv.4) comprises

[0090] feeding the SN obtained according to (iv.3) into an amine production unit APU serving as a hydrogenation unit and bringing the at least one nitrated aromatic compound comprised in the SN into contact with H2 in the hydrogenation unit, thereby obtaining a stream S4 comprising at least one corresponding aromatic polyamine R(-NH2)x.

[0091] Preferably, the at least one polyamine R(-NH2)x is selected from the group consisting of monomeric methylene diphenyl diamine, polymethylene polyphenylene polyamine, a mixture of methylene diphenyl diamine and polymethylene polyphenylene polyamine, toluene diamine (TDA), isomers of xylene diamine (XDA), isomers of diaminobenzene, 2,6-dimethylaniline, naphthalene-1,5-diamine (1,5-NDA), 1,4-diaminobutane, 1,5-diaminopentane (PDA), 1,6-diaminohexane (HDA), 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 2,2-dimethyl-1,5-diaminopentane, 2-methyl-1,5-pentanediamine (MPDA), 2,4,4(or 2,2,4)-trimethyl-1,6-diaminohexane (TMDA), 1,3- and 1,4-diaminocyclohexane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane (IPDA), 2,4- or 2,6-diamino-1-methylcyclohexane (H6-TDA), 1-amino-1-methyl-4(3)-aminomethylcyclohexane (AMCA), 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, bis(aminomethyl)norbornane (NBDA), 4,4′-diaminodicyclohexylmethane, 2,4′-diaminodicyclohexylmethane, triaminocyclohexane, tris(aminomethyl)cyclohexane, triaminomethylcyclohexane, 1,8-diamino-4-(aminomethyl)octane, undecane-1,6,11-triamine, 1,7-diamino-4-(3-aminopropyl)heptane, 1,6-diamino-3-(aminomethyl)hexane, and 1,3,5-tris(aminomethyl)cyclohexane. More preferably, the at least one polyamine R(-NH2)x is selected from the group consisting of monomeric methylene diphenyl diamine, polymethylene polyphenylene polyamine, a mixture of monomeric methylene diphenyl diamine and polymethylene polyphenylene polyamine, and toluene diamine (TDA).

[0092] Preferably, the at least one polyamine R(-NH2)x is toluene diamine (TDA), preferably, TDA comprises a mixture of 2,4-TDA (80 wt.-%) and 2,6-TDA (20 wt.-%).

[0093] Preferably, (iv.4) comprises

[0094] (iv.4.1) Passing the SN containing dinitrotoluene obtained according to (iv.3) into a hydrogenation unit HU under hydrogenation conditions to obtain a stream S4 containing toluene diamine (TDA).

[0095] Preferably, the hydrogenation unit used in (iv.4.1) is a three-phase reactor.

[0096] Alternatively, preferably, the at least one polyamine R(-NH2)x is selected from the group consisting of monomeric methylene diphenyl diamine, polymethylene polyphenylene polyamine, and mixtures of monomeric methylene diphenyl diamine and polymethylene polyphenylene polyamine, more preferably selected from the group consisting of monomeric methylene diphenyl diamine and mixtures of monomeric methylene diphenyl diamine (mMDA) and polymethylene polyphenylene polyamine (PMDA).

[0097] Preferably, the monomeric methylene diphenyl diamine comprises, more preferably consists of, one or more of 4,4'-diaminodiphenylmethane, 2,2'-diaminodiphenylmethane, and 2,4'-diaminodiphenylmethane. More preferably, the at least one polyamine R(-NH2)x is 4,4'-diaminodiphenylmethane.

[0098] In the context of the present invention, when the term "diaminodiphenylmethane" or "MDA" is used, it encompasses all isomers, monomers, and polymethylene polyphenylene polyamines.

[0099] According to the alternative, preferably, (iv.4) comprises

[0100] (iv.4.1’) preparing an aqueous stream SF comprising formaldehyde;

[0101] (iv.4.2’) passing SN obtained according to (iv.3) into a hydrogenation unit included in an amine production unit APU under hydrogenation conditions to obtain a stream S14 comprising aniline;

[0102] (iv.4.3’) contacting S14 obtained according to (iv.4.2’) with SF obtained according to (iv.4.1’) in a condensation reactor R included in APU C in the presence of a catalyst, more preferably an acidic catalyst, more preferably an acidic catalyst as hydrochloric acid, to obtain a stream S4 comprising one or more of monomeric methylene diphenyl diisocyanate and polymethylene polyphenylene polyisocyanate.

[0103] Preferably, (iv.4.2’) comprises passing SN obtained according to (iv.3) into a hydrogenation unit included in an amine production unit APU and contacting SN with a catalyst in the hydrogenation unit in the gas phase to obtain a stream S14 comprising aniline.

[0104] It is also conceivable that the catalyst used in (iv.4.3’) is a heterogeneous catalyst.

[0105] Preferably, the method further comprises passing S14 into a purification unit, more preferably one or more distillation columns, even more preferably at least two distillation columns, to obtain a purified stream S14 containing aniline.

[0106] Preferably, aniline is obtained by methods known in the art, such as those disclosed in the following documents: T. Kahl et al. “Aniline” Volume 3 in “Ullmanns' Encyclopedia of industrial chemistry”, Wiley-VCH Verlag GmbH & Co KGaA, Weinheim, 2012.

[0107] Preferably, the hydrogenation unit used in (iv.4.2’) is a fluidized bed reactor.

[0108] Preferably, (iv.4.1’) comprises

[0109] Passing a portion of the SM obtained according to (iv.1) into a reactor for preparing formaldehyde in the presence of H2O and O2 to obtain an aqueous stream SF containing formaldehyde.

[0110] The preparation of formaldehyde is preferably carried out by methods known in the art, such as those disclosed in the following documents: A. W. Franz et al. “Formaldehyde” in “Ullmanns' Encyclopedia of industrial chemistry”, Wiley-VCH Verlag GmbH & Co KGaA, Weinheim, 2016.

[0111] Preferably, (v.1) comprises

[0112] Contacting and reacting a stream containing HCl with a stream containing O2 in the presence of a catalyst to obtain a stream S5 containing Cl2.

[0113] For the preparation of Cl2 according to the present invention, methods well-known in the art can be used. For example, Cl2 can be prepared according to the Deacon process, as exemplified and disclosed in WO 2007 / 134771 A1, WO 2011 / 111351 A1, WO 2013 / 004651 A1, WO 2013 / 060628 A1, US 2418930, WO 2012 / 025483, WO 2007137685; or via HCl electrolysis, as disclosed in US 6022634, WO 2003 / 31690, WO 1999031297, EP 1103636 and US 3236760; or via NaCl electrolysis, as in EP0004903.

[0114] Preferably, the purification unit according to (v.2) is the CO-H2 separation cold box CB.

[0115] Preferably, the method further comprises recycling at least a portion of the S CH obtained according to (v.2) in R RWGS therein.

[0116] Preferably, when carrying out (iv.1), 5 to 25 wt.-%, more preferably 7 to 20 wt.-%, of S3 is fed to the purification unit according to (v.2), more preferably fed into the CO-H2 separation cold box.

[0117] Alternatively, preferably, when carrying out (iv.1’), 95 to 100 wt.-%, more preferably 98 to 100 wt.-%, more preferably 99 to 100 wt.-%, of S3 is fed to the purification unit according to (v.2), more preferably fed into the CO-H2 separation cold box CB.

[0118] Preferably, (v.2) comprises

[0119] passing a portion of the S3 obtained according to (iii), more preferably (iii.2’), into the CO-H2 separation cold box, thereby obtaining a stream S CO comprising CO and a stream S CH comprising H2 that is CO-lean compared to said portion of S3.

[0120] Preferably, 99 to 100 wt.-%, more preferably 99.9 to 100 wt.-%, more preferably 99.99 to 100 wt.-%, of S CO consists of CO.

[0121] Preferably, S CO is substantially free of H2, more preferably free of H2. In other words, preferably at most 0.1 wt.-% of S COConsisting of H2, more preferably at most 0.01 wt-% S CO Consisting of H2, more preferably at most 0.001 wt-% S CO Consisting of H2.

[0122] Preferably, (v.3) comprises

[0123] A part of S3 obtained according to (iii), more preferably (iii.2’), or S obtained according to (v.2) CO 、more preferably S obtained according to (v.2) CO Is introduced into the reaction unit RU for phosgene preparation P And the said part of S3 is contacted with S5 obtained according to (v.1) in RU P In the presence of a catalyst, more preferably activated carbon, to obtain a stream S6 containing phosgene.

[0124] Preferably, RU P Is a tube bundle reactor.

[0125] Preferably, the preparation of phosgene is a heterogeneous gas-phase catalysis on activated carbon.

[0126] Phosgene is preferably prepared by methods known in the art, such as those disclosed in: Ullmann's Encyclopedia of industrial chemistry, chapter, phosgene, 5th edition, volume A19, pages 413 ff., VCH Verlagsgesellschaft mbH, Weinheim, 1991 and C. Ryan et al. "Phosgene and related carbonylhalides", Elsevier Science, 1996, ISBN 978-0-08-053880-8.

[0127] Preferably, (vi) comprises

[0128] (vi.1) S4 containing at least one polyamine R(-NH2)x obtained according to (iv.4), S6 obtained according to (v), and optionally a solvent are introduced into a mixing device, more preferably a mixing nozzle, included in the reaction unit RU, where the solvent is an aromatic solvent, more preferably a halogenated aromatic solvent, more preferably monochlorobenzene or dichlorobenzene, to obtain a reaction mixture;

[0129] (vi.2) The reaction mixture obtained according to (vi.1) is passed into one or more reactors included in RU, thereby obtaining a stream SP comprising the at least one polyisocyanate R(-NCO)x.

[0130] Preferably, the method further comprises passing SP into a work-up unit, preferably a distillation unit, for removing the solvent (if any).

[0131] Preferably, the material stream SP contains the at least one polyisocyanate R(-NCO)x selected from the group consisting of: monomeric methylenediphenylene diisocyanate, polymethylene polyphenylene polyisocyanate, a mixture of monomeric methylenediphenylene diisocyanate and polymethylene polyphenylene polyisocyanate, toluene diisocyanate (TDI), isomers of xylene diisocyanate (XDI), isomers of diisocyanatobenzene, xylene 2,6 - diisocyanate, naphthalene 1,5 - diisocyanate (1,5 - NDI), 1,4 - diisocyanate, pentane 1,5 - diisocyanate (PDI), hexane 1,6 - diisocyanate (HDI), octane 1,8 - diisocyanate, nonane 1,9 - diisocyanate, decane 1,10 - diisocyanate, 2,2 - dimethylpentane 1,5 - diisocyanate, 2 - methylpentane 1,5 - diisocyanate (MPDI), 2,4,4(or 2,2,4) - trimethylhexane 1,6 - diisocyanate (TMDI), cyclohexane 1,3 - and 1,4 - diisocyanate, 1 - isocyanato - 3,3,5 - trimethyl - 5 - isocyanatomethylcyclohexane (IPDI), 2,4 - or 2,6 - diisocyanato - 1 - methylcyclohexane (H6 - TDI), 1 - isocyanato - 1 - methyl - 4(3) - isocyanatomethylcyclohexane (AMCI), 1,3 - bis(isocyanatomethyl)cyclohexane, 1,4 - bis(isocyanatomethyl)cyclohexane, bis(isocyanatomethyl)norbornane (NBDI), 4,4′ - diisocyanatodicyclohexylmethane, 2,4′ - diisocyanatodicyclohexylmethane, triisocyanatocyclohexane, tris(isocyanatomethyl)cyclohexane, triisocyanatomethylcyclohexane, 1,8 - diisocyanato - 4 - (isocyanatomethyl)octane, undecane 1,6,11 - triisocyanate, 1,7 - diisocyanato - 4 - (3 - isocyanatopropyl)heptane, 1,6 - diisocyanato - 3 - (isocyanatomethyl)hexane and 1,3,5 - tris(isocyanatomethyl)cyclohexane, more preferably selected from the group consisting of: monomeric methylenediphenylene diisocyanate, polymethylene polyphenylene polyisocyanate, a mixture of monomeric methylenediphenylene diisocyanate and polymethylene polyphenylene polyisocyanate, toluene diisocyanate (TDI) and isomers of xylene diisocyanate (XDI), even more preferably selected from the group consisting of: monomeric methylenediphenylene diisocyanate, polymethylene polyphenylene polyisocyanate, a mixture of monomeric methylenediphenylene diisocyanate and polymethylene polyphenylene polyisocyanate, and toluene diisocyanate (TDI).

[0132] Preferably, in SP, the at least one polyisocyanate R(-NCO)x is TDI, more preferably a mixture of 2,4 - TDI and 2,6 - TDI.

[0133] Preferably, the TDI is a mixture of 2,4-TDI (80 wt.-%) and 2,6-TDI (20 wt.-%).

[0134] Preferably, in the SP, the at least one polyisocyanate R(-NCO)x is selected from the group consisting of monomeric methylene diphenylene diisocyanate, polymethylene polyphenylene polyisocyanate, and a mixture of monomeric methylene diphenylene diisocyanate and polymethylene polyphenylene polyisocyanate.

[0135] Preferably, the monomeric methylene diphenylene diisocyanate (mMDI) comprises, more preferably consists of, one or more of 4,4'-methylene(diphenyl diisocyanate) (4,4'-MDI), 2,2'-methylene(diphenyl diisocyanate) (2,2'-MDI), and 2,4'-methylene(diphenyl diisocyanate) (2,4'-MDI), more preferably 4,4'-methylene(diphenyl diisocyanate) (4,4'-MDI).

[0136] Preferably, the method further comprises separating the monomeric methylene diphenylene diisocyanate and the polymethylene polyphenylene polyisocyanate comprised in the SP by one or more of a distillation step and a crystallization step, thereby obtaining one or more mixtures M1 of 2,4'- and 4,4'-MDI and a mixture M2 of monomeric methylene diphenylene diisocyanate and polymethylene polyphenylene polyisocyanate.

[0137] Preferably, at least 22.5%, more preferably at least 30%, more preferably at least 50% of the carbon atoms in the at least one polyisocyanate R(-NCO)x are derived from CO2.

[0138] The present invention further relates to a production unit for carrying out the method according to the present invention, the production unit comprising:

[0139] - a reaction unit R RWGS which is used for the reverse water gas shift reaction to obtain S3 comprising CO and H2;

[0140] - means for introducing CO2 into R RWGS ;

[0141] - means for introducing H2 into R RWGS ;

[0142] - means for removing S3 from R RWGS ;

[0143] - an alcohol production unit PU1 for obtaining SM or an alkane production unit PU2 for obtaining SM';

[0144] - Device for introducing a portion of S3 into PU1;

[0145] - Device for introducing a portion of S1 into PU2;

[0146] - Device for removing SM from PU1 or for removing SM' from PU2;

[0147] - Aromatic production unit PU MTA that is used to obtain a stream SA containing at least one aromatic compound;

[0148] - Device for introducing SM or SM' into PU MTA ;

[0149] - Nitration reaction unit RU N that is used to obtain a stream SN containing at least one nitrated aromatic compound;

[0150] - Device for removing SN from RU N ;

[0151] - Amine production unit APU that is used to obtain a stream S4 containing at least one polyamine R(-NH2)x, where x = 2 or greater;

[0152] - Device for introducing SN into APU;

[0153] - Reaction unit RU P that is used to prepare phosgene as stream S6;

[0154] - Device for introducing S5 into RU P ;

[0155] - Purification unit, preferably CO-H2 separation cold box CB, that is used to obtain stream S CO ;

[0156] - Device for introducing S CO into RU P ;

[0157] - Device for removing S CO from the purification unit;

[0158] - Device for removing S CH from the purification unit;

[0159] - Device for introducing a portion of S3 into the purification or R UP ;

[0160] - Device for removing S6 from R UP ;

[0161] - A reaction unit RU for obtaining a stream SP comprising at least one corresponding polyisocyanate R(-NCO)x;

[0162] - A device for introducing S4 into RU;

[0163] - A device for introducing S6 into RU;

[0164] - A device for removing SP from RU.

[0165] Preferably, the amine production unit APU includes one or more of a hydrogenation unit and a condensation reaction unit.

[0166] Preferably, APU includes a hydrogenation unit. Alternatively, APU includes a hydrogenation unit and a condensation unit.

[0167] Preferably, the production unit further includes a reactor for preparing formaldehyde from a part of SM.

[0168] Preferably, the production unit further includes one or more purification units, such as one or more distillation columns, one or more flash tanks, one or more liquid-liquid separation units, one or more solid-liquid separation units (such as filters, sieves), one or more evaporators, one or more dryers, one or more crystallization units, and one or more extraction units.

[0169] Preferably, the production unit further includes one or more heat exchangers.

[0170] The present invention further relates to a polyisocyanate R(-NCO)x, characterized in that at least 22.5%, preferably at least 30%, more preferably at least 50% of its carbon atoms are obtained from CO2. Preferably, the polyisocyanate R(-NCO)x is MDI. Alternatively, preferably, the polyisocyanate R(-NCO)x is TDI.

[0171] The present invention further relates to a polyisocyanate R(-NCO)x obtainable or obtained by the method according to any one of Examples 1 to 28, wherein at least 22.5%, preferably at least 30%, more preferably at least 50% of its carbon atoms are obtained from CO2. Preferably, the polyisocyanate R(-NCO)x is MDI. Alternatively, preferably, the polyisocyanate R(-NCO)x is TDI.

[0172] The present invention further relates to the use of the polyisocyanate R(-NCO)x according to the present invention for preparing polyurethanes or polyurethane ureas.

[0173] The present invention is further illustrated by the following groups of examples and combinations of examples obtained from the dependencies and backward references as shown. In particular, it should be noted that in each case where a series of examples is mentioned, for example, in the context of a term such as "a method as described in any one of Examples 1 to 3", each example in this series is intended to be clearly disclosed to a person skilled in the art, that is, the wording of this term should be understood by a person skilled in the art as being synonymous with "a method as described in any one of Examples 1, 2, and 3". Furthermore, it should be clearly stated that the following groups of examples represent suitable structural parts of a general description of the preferred aspects of the present invention and thus appropriately support but do not represent the claims of the present invention.

[0174] 1. A method for preparing at least one polyisocyanate R(-NCO)x from CO2, the method comprising

[0175] (i) providing a stream S1 containing CO2;

[0176] (ii) providing a stream S2 containing H2;

[0177] (iii) introducing a portion of S1 obtained according to (i) and a portion of S2 obtained according to (ii) into a reaction unit RU RWGS and bringing them into contact to carry out the reverse water gas shift reaction, thereby obtaining a stream S3 containing CO and H2 and a stream SH containing H2O;

[0178] (iv) preparing at least one polyamine R(-NH2)x, where x = 2 or greater, the preparation comprising

[0179] (iv.1) introducing a portion of S3 obtained according to (iii), or a portion of S1 and a portion of S2 obtained respectively according to (i) and (ii), into an alcohol production unit PU1 and bringing the CO and H2 contained in the said portion of S3 into contact in PU1, or bringing S1 and S2 into contact in PU1, thereby obtaining a stream SM containing an alcohol having 1 to 4 carbon atoms; or

[0180] (iv.1’) introducing a portion of S1 and a portion of S2 obtained respectively according to (i) and (ii) into an alkane production unit PU2 and bringing the said portion of S1 into contact with the said portion of S2 in PU2, thereby obtaining a stream SM’ containing C1-C4 alkanes;

[0181] (iv.2) introducing a portion of SM obtained according to (iv.1), or a portion of SM’ obtained according to (iv.1’), into an aromatic production unit PU MTA and bringing the alcohol having 1 to 4 carbon atoms contained in SM, or the C1-C4 alkanes contained in SM’, into contact in PU MTAReact in the middle to obtain a stream SA containing at least one aromatic compound;

[0182] (iv.3) React SA obtained according to (iv.2) with nitric acid in the nitration reaction unit RU N in the middle to obtain a stream SN containing the corresponding at least one nitrated aromatic compound;

[0183] (iv.4) Pass SN obtained according to (iv.3) into the amine production unit APU and react the at least one nitrated aromatic compound contained in SN in APU to obtain a stream S4 containing at least one polyamine R(-NH2)x;

[0184] (v) Prepare phosgene, and this preparation includes

[0185] (v.1) Provide a stream S5 containing Cl2;

[0186] (v.2) Pass a part of S3 into the purification unit to obtain a stream S containing CO CO and a stream S containing H2 that is poor in CO compared to this part of S3 CH ;

[0187] (v.3) Pass at least a part of S obtained according to (v.2) CO into the reaction unit RU for preparing phosgene P in the middle and contact the at least part of S CO with S5 obtained according to (v.1) in RU P in the middle to obtain a stream S6 containing phosgene;

[0188] (vi) Pass S4 containing at least one polyamine R(-NH2)x obtained according to (iv.4) into the reaction unit RU and react S4 with the phosgene contained in S6 obtained according to (v.3) in RU to obtain a stream SP containing the at least one polyisocyanate R(-NCO)x.

[0189] 2. The method according to Example 1, wherein the reverse water gas shift reaction carried out in RU according to (iii) RWGS is carried out at a temperature in the range of 500 °C to 1200 °C, preferably in the range of 700 °C to 1100 °C, more preferably in the range of 800 °C to 1000 °C, more preferably in the range of 850 °C to 1000 °C, more preferably in the range of 900 °C to 1000 °C.

[0190] 3. The method according to Example 1 or 2, wherein the reverse water gas shift reaction carried out in RU according to (iii) RWGSThe reverse water gas shift reaction carried out therein is carried out at a pressure in the range of 0.5 to 20 (absolute pressure), preferably in the range of 2 to 18 bar (absolute pressure), more preferably in the range of 2 to 15 bar (absolute pressure).

[0191] 4. The method according to any one of Examples 1 to 3, wherein, according to (iii) in RU RWGS The molar ratio of H2 to CO2 in the reverse water gas shift reaction carried out therein is in the range of 0.5:1 to 10:1, more preferably in the range of 0.8:1 to 5:1, more preferably in the range of 1:1 to 3:1, more preferably in the range of 1.5:1 to 3:1, more preferably in the range of 2:1 to 3:1.

[0192] 5. The method according to any one of Examples 1 to 4, wherein, (iii) comprises

[0193] (iii.1) Passing a part of S1 obtained according to (i) and a part of S2 obtained according to (ii) into the reaction unit RU RWGS therein and bringing them into contact to carry out the reverse water gas shift reaction, thereby obtaining a stream S13 containing CO, CO2, H2 and H2O;

[0194] (iii.2) Cooling the stream S13 obtained according to (iii.1) in a condensation unit CU, thereby obtaining a gaseous stream S3 containing CO and H2 that is lean in water compared to S13, and a liquid stream SH containing H2O.

[0195] 6. The method according to any one of Examples 1 to 4, wherein, (iii) comprises

[0196] (iii.1) Passing a part of S1 obtained according to (i) and a part of S2 obtained according to (ii) into the reaction unit RU RWGS therein and bringing them into contact to carry out the reverse water gas shift reaction, thereby obtaining a stream S13 containing CO, CO2, H2 and H2O;

[0197] (iii.2’) comprises

[0198] (iii.2’.1) Cooling the stream S13 obtained according to (iii.1) in a condensation unit CU, thereby obtaining a gaseous stream S23 containing CO and H2 that is lean in water compared to S13, and a liquid stream SH containing H2O;

[0199] (iii.2’.2) Passing the S23 obtained according to (iii.2’.1) into an amine scrubbing unit to remove CO2, thereby obtaining a gaseous stream S3 containing CO and H2 that is lean in CO2 compared to S23.

[0200] 7. The method according to embodiment 5 or 6, wherein the condensation unit comprises a condensation means and one or more heat exchangers.

[0201] 8. The method according to any one of embodiments 1 to 7, wherein the weight ratio of CO to H2 in S3 is in the range of 1:1 to 30:1, preferably in the range of 2:1 to 20:1, more preferably in the range of 5:1 to 15:1.

[0202] 9. The method according to any one of embodiments 1 to 8, wherein 25 to 100 weight-% of S3 consists of CO and H2.

[0203] 10. The method according to any one of embodiments 1 to 9, wherein according to (iv.1), 75 to 95 weight-%, preferably 85 to 93 weight-% of S3 is fed into the alcohol production unit PU1.

[0204] 11. The method according to any one of embodiments 1 to 10, wherein PU1 comprises an alcohol production reactor, wherein (iv.1) comprises feeding a part of S3 into PU1 and bringing the CO and H2 contained in said part of S3 into contact with the catalyst in the alcohol production reactor at a temperature in the range of 150°C to 500°C, preferably in the range of 180°C to 320°C, preferably in the range of 200°C to 300°C, more preferably in the range of 205°C to 280°C, thereby obtaining a stream SM containing alcohols having 1 to 4 carbon atoms.

[0205] 12. The method according to any one of embodiments 1 to 10, wherein PU2 comprises an alkane production reactor, wherein (iv.1’) comprises

[0206] feeding a part of S1 and a part of S2 into PU2 and bringing the CO2 contained in said part of S1 and the H2 contained in said part of S2 into contact in the alkane production reactor PU2 at a temperature in the range of 250°C to 600°C, preferably in the range of 280°C to 500°C, more preferably in the range of 300°C to 400°C, thereby obtaining a stream SM’ containing C1-C4 alkanes.

[0207] 13. The method according to any one of embodiments 1 to 12, wherein (iv.2) comprises

[0208] feeding a part of SM obtained according to (iv.1) or a part of SM’ obtained according to (iv.1’) into the aromatic production unit PU MTA and bringing it into contact with the catalyst in the aromatic production unit, thereby obtaining a stream SA containing at least one aromatic compound, wherein the aromatic compound is selected from the group consisting of benzene, toluene and xylene, more preferably benzene or toluene.

[0209] 14. The method according to any one of Embodiments 1 to 13, wherein the PU MTA comprises at least one aromatic conversion reactor, preferably one or more of a fixed bed reactor and a fluidized bed reactor.

[0210] 15. The method according to Embodiment 14, insofar as Embodiment 14 is subordinate to Embodiment 13, wherein when (iv.1) is carried out, (iv.2) comprises

[0211] (iv.2.1) feeding a part of the SM obtained according to (iv.1) into the at least one aromatic conversion reactor, preferably into at least one methanol-to-aromatic compound conversion reactor;

[0212] (iv.2.2) contacting the stream SM with the catalyst in the at least one reactor, preferably at a temperature in the range of 250 °C to 750 °C, more preferably in the range of 300 °C to 600 °C, to obtain a stream SA1 comprising a mixture of water and aromatic compounds, these aromatic compounds being benzene, toluene and xylene;

[0213] (iv.2.3) feeding the stream SA1 obtained according to (iv.2.2) into a separation unit SU to obtain a stream SA comprising benzene or toluene; or

[0214] wherein when (iv.1’) is carried out, (iv.2) comprises

[0215] (iv.2.1’) feeding a part of the SM’ obtained according to (iv.1’) into the at least one aromatic conversion reactor, more preferably into at least one methane-to-aromatic compound conversion reactor;

[0216] (iv.2.2’) contacting the stream SM’ with the catalyst in the at least one reactor, more preferably at a temperature in the range of 600 °C to 1000 °C, more preferably in the range of 625 °C to 900 °C, even more preferably in the range of 650 °C to 850 °C, to obtain a stream SA1' comprising a mixture of aromatic compounds, these aromatic compounds being benzene, toluene and xylene;

[0217] (iv.2.3’) feeding the stream SA1’ obtained according to (iv.2.2’) into a separation unit SU’ to obtain a stream SA comprising benzene or toluene.

[0218] 16. The method according to any one of Embodiments 1 to 15, wherein (iv.3) comprises

[0219] contacting the SA obtained according to (iv.2) with nitric acid in a nitration reaction unit RU NReact in the middle to obtain a stream SN containing the corresponding at least one nitrated aromatic compound, wherein preferably, the at least one nitrated aromatic compound is selected from the group consisting of nitrobenzene and dinitrotoluene.

[0220] 17. The method according to any one of embodiments 1 to 16, wherein (iv.4) comprises

[0221] Pass the SN obtained according to (iv.3) into an amine production unit APU as a hydrogenation unit and bring the at least one nitrated aromatic compound contained in SN into contact with H2 in the hydrogenation unit, thereby obtaining a stream S4 containing at least one corresponding aromatic polyamine R(-NH2)x.

[0222] 18. The method according to embodiment 17, wherein (iv.4) comprises

[0223] (iv.4.1) Pass the SN containing dinitrotoluene obtained according to (iv.3) into a hydrogenation unit HU under hydrogenation conditions, thereby obtaining a stream S4 containing toluenediamine (TDA).

[0224] 19. The method according to any one of embodiments 1 to 16, wherein (iv.4) comprises

[0225] (iv.4.1’) Prepare an aqueous stream SF containing formaldehyde;

[0226] (iv.4.2’) Pass the SN obtained according to (iv.3) into a hydrogenation unit included in the amine production unit APU under hydrogenation conditions, thereby obtaining a stream S14 containing aniline;

[0227] (iv.4.3’) Bring the S14 obtained according to (iv.4.2’) into contact with the SF obtained according to (iv.4.1’) in a condensation reactor R included in the APU C in the presence of a catalyst, preferably an acidic catalyst, more preferably hydrochloric acid, thereby obtaining a stream S4 containing one or more of monomeric methylene diphenyl diisocyanate and polymethylene polyphenyl polyisocyanate.

[0228] 20. The method according to embodiment 19, wherein (iv.4.1’) comprises

[0229] Pass a part of the SM obtained according to (iv.1) into a reactor for preparing formaldehyde in the presence of H2O and O2, thereby obtaining an aqueous stream SF containing formaldehyde.

[0230] 21. The method according to any one of embodiments 1 to 20, wherein (v.1) comprises

[0231] Contact a stream containing HCl with a stream containing O2 in the presence of a catalyst to obtain a stream S5 containing Cl2.

[0232] 22. The method according to any one of Examples 1 to 21, wherein the purification unit according to (v.2) is a CO-H2 separation cold box CB.

[0233] 23. The method according to any one of Examples 1 to 22, wherein (v.3) comprises

[0234] Pass at least a portion of S obtained according to (v.2), more preferably S obtained according to (v.2) CO into a reaction unit RU for preparing phosgene CO and contact the said portion of S3 with S5 obtained according to (v.1) in RU P in the presence of a catalyst, preferably activated carbon, to obtain a stream S6 containing phosgene. P

[0235] 24. The method according to any one of Examples 1 to 23, wherein (vi) comprises

[0236] (vi.1) Introduce S4 containing at least one polyamine R(-NH2)x obtained according to (iv.4), S6 obtained according to (v), and optionally a solvent into a mixing device, preferably a mixing nozzle, included in the reaction unit RU, wherein the solvent is preferably an aromatic solvent, more preferably a halogenated aromatic solvent, more preferably monochlorobenzene or dichlorobenzene, to obtain a reaction mixture; (vi.2) Pass the reaction mixture obtained according to (vi.1) into one or more reactors included in RU to obtain a stream SP containing the at least one polyisocyanate R(-NCO)x.

[0237]

[0238] 25. The method according to any one of Examples 1 to 24, wherein in SP, the at least one polyisocyanate R(-NCO)x is TDI, preferably a mixture of 2,4-TDI and 2,6-TDI.

[0239] 26. The method according to any one of Examples 1 to 24, wherein in SP, the at least one polyisocyanate R(-NCO)x is selected from the group consisting of monomeric methylene diphenyl diisocyanate, polymethylene polyphenylene polyisocyanate, and a mixture of monomeric methylene diphenyl diisocyanate and polymethylene polyphenylene polyisocyanate.

[0240] ​27. The method according to any one of embodiments 1 to 26, wherein at least 22.5%, preferably at least 30%, more preferably at least 50% of the carbon atoms in the at least one polyisocyanate R(-NCO)x are derived from CO2.

[0241] 28. A production unit for carrying out the method according to any one of embodiments 1 to 27, the production unit comprising:

[0242] - Reaction unit R RWGS , which is used for the reverse water gas shift reaction to obtain S3 containing CO and H2;

[0243] - Device for introducing CO2 into R RWGS ;

[0244] - Device for introducing H2 into R RWGS ;

[0245] - Device for removing S3 from R RWGS ;

[0246] - Alcohol production unit PU1 for obtaining SM or alkane production unit PU2 for obtaining SM';

[0247] - Device for passing a part of S3 into PU1;

[0248] - Device for passing a part of S1 into PU2;

[0249] - Device for removing SM from PU1 or for removing SM' from PU2;

[0250] - Aromatic production unit PU MTA , which is used to obtain a stream SA containing at least one aromatic compound;

[0251] - Device for passing SM or SM' into PU MTA ;

[0252] - Nitration reaction unit RU N , which is used to obtain a stream SN containing at least one nitrated aromatic compound;

[0253] - Device for removing SN from RU N ;

[0254] - Amine production unit APU, which is used to obtain a stream S4 containing at least one polyamine R(-NH2)x, where x = 2 or greater;

[0255] - Device for passing SN into APU;

[0256] - Reaction unit RU P, which is used for preparing phosgene as the stream S6;

[0257] - A device for introducing S5 into RU P ;

[0258] - A purification unit, preferably a CO-H2 separation cold box, which is used for obtaining the stream S CO ;

[0259] - A device for introducing S CO into RU P ;

[0260] - A device for removing S CO from this purification unit;

[0261] - A device for removing S CH from this purification unit;

[0262] - A device for introducing a part of S3 into this purification or R UP ;

[0263] - A device for removing S6 from R UP ;

[0264] - A reaction unit RU, which is used for obtaining a stream SP containing at least one corresponding polyisocyanate R(-NCO)x;

[0265] - A device for introducing S4 into RU;

[0266] - A device for introducing S6 into RU;

[0267] - A device for removing SP from RU.

[0268] 29. The production unit according to embodiment 28, wherein the amine production unit APU comprises a hydrogenation unit and optionally a condensation reaction unit.

[0269] 30. The production unit according to embodiment 29, wherein APU comprises a hydrogenation unit.

[0270] 31. The production unit according to embodiment 29, wherein APU comprises a hydrogenation unit and a condensation unit.

[0271] 32. The production unit according to any one of embodiments 28 to 31, which further comprises a reactor for preparing formaldehyde from a part of SM.

[0272] 33. A polyisocyanate R(-NCO)x, characterized in that at least 22.5%, preferably at least 30%, more preferably at least 50% of its carbon atoms are obtained from CO2.

[0273] 34. A polyisocyanate R(-NCO)x obtainable or obtained by a method according to any one of Examples 1 to 27, wherein at least 22.5%, preferably at least 30%, more preferably at least 50% of its carbon atoms are obtained from CO2.

[0274] 35. The polyisocyanate according to Example 33 or 34, which is MDI.

[0275] 36. The polyisocyanate according to Example 33 or 34, which is TDI.

[0276] In the context of the present invention, the term "gas stream" or "gaseous stream" refers to a stream in the gas phase or gaseous phase. Similarly, the term "liquid stream" refers to a stream in the liquid phase.

[0277] It should be expressly noted that the above groups of examples represent suitable structural parts of the general description of the preferred aspects of the present invention and thus suitably support but do not represent the claims of the present invention.

[0278] In the context of the present invention, the term "X is one or more of A, B and C", where X is a given feature and each of A, B and C represents a specific implementation of said feature, should be understood to disclose that X is A, or B, or C, or A and B, or A and C, or B and C, or A and B and C. In this regard, it should be noted that a person skilled in the art can translate the above abstract terms into specific examples, for example, where X is a chemical element and A, B and C are specific elements such as Li, Na and K, or X is a temperature and A, B and C are specific temperatures such as 10 °C, 20 °C and 30 °C. In this regard, it should further be noted that a person skilled in the art can extend the above terms to less specific implementations of said feature, such as "X is one or more of A and B", which discloses that X is A, or B, or A and B, or to more specific implementations of said feature, such as "X is one or more of A, B, C and D", which discloses that X is A, or B, or C, or D, or A and B, or A and C, or A and D, or B and C, or B and D, or C and D, or A and B and C, or A and B and D, or B and C and D, or A and B and C and D.

[0279] The present invention is further illustrated by the following examples.

[0280] Examples

[0281] Example 1 Method for preparing MDI from CO2 according to the present invention

[0282] The method is based on Figure 3Flow chart. Feed 4451 kg / h of purified CO2 stream into the RWGS unit and mix it with approximately 2150 kg / h of CO2 recycle stream. These two streams form stream S1. Mix CO2 with stream S2 of 620 kg / h of hydrogen, and then partially convert it to CO and water in reactor R RWGS at a pressure of 900 °C and 5 bar (absolute pressure). The conversion rate of CO2 to CO is approximately 67%. Cool the reaction mixture (stream S13) via a condensation unit, and condense out approximately 1720 kg / h of water with approximately 1.7 wt.-% dissolved CO2. Feed the remaining gas phase (stream S23) into an amine scrubbing unit, where CO2 (approximately 2150 kg / h) is separated, then thermally released from the amine solution and fed back into the reaction as part of S1. There remains approximately 3232 kg / h of gas mixture (stream S3), which contains approximately 87 wt.-% of CO, 13 wt.-% of H2, and trace amounts of methane.

[0283] Feed approximately 17% of the stream S3 into a CO-H2 separation cold box, where a purified CO-stream S CO is produced at approximately 371 kg / h. Feed the remaining gas stream S CH with approximately 42 wt.-% H2 and 58% CO at 165 kg / h back into R RWGS .

[0284] Feed the remaining 83% of the stream S3 obtained from R RWGS into a methanol production unit PU1, where approximately 2971 kg / h of MeOH (stream SM) is produced.

[0285] A part of the stream SM containing methanol (2567 kg / h) is converted to light hydrocarbons (<= C4) in the first stage of the MTA production unit, and then after separating water and light-boiling compounds in the second stage of the MTA production unit, it is mostly converted to benzene, toluene, and xylene (BTX). In the method for obtaining BTX, an LPG fraction of approximately 282 kg / h, a wastewater fraction of approximately 1476 kg / h, and a heavy-boiling aromatic compound fraction of approximately 796 kg / h are obtained. Further distill this fraction to obtain a gasoline-like fraction of approximately 160 kg / h, 51 kg / h of benzene, 280 kg / h of toluene, and 305 kg / h of xylene isomers.

[0286] Mix the benzene stream with approximately 934 kg / h of benzene and a recycle stream of approximately 100 kg / h of benzene from different sources to obtain stream SA. Then pass stream SA through a nitration reaction unit RU N, i.e., fed into an adiabatic nitration reactor and then converted to nitrobenzene with about 20386 kg / h of nitrating acid (4.2 wt.-% HNO3, 64.8 wt.-% H2SO4, and 31 wt.-% water) at a stoichiometric benzene excess of about 10% relative to HNO3. The reaction mixture is phase-separated, and the dilute sulfuric acid is concentrated in a flash system and recycled back to the nitration reaction unit RU. N In it. The organic phase is washed, and the excess benzene is separated to obtain a stream SN containing about 1552 kg / h of nitrobenzene.

[0287] A portion (about 224 kg / h) of the methanol stream SM from the methanol production unit that is not fed into the MTA production unit is catalytically reacted with air and water under oxidative dehydrogenation adiabatically in R. F to obtain an aqueous solution of 50 wt.-% formaldehyde (stream SF) of about 378 kg / h and used for the condensation of aniline cooled to MDA in APU.

[0288] Then the stream SN containing nitrobenzene is catalytically hydrogenated in the gas phase in a hydrogenation unit (i.e., a fluidized bed) included in the amine production unit APU to aniline. Water (about 454 kg / h) is separated, and the aniline is purified by distillation to obtain about 1174 kg / h of aniline.

[0289] The aniline is mixed with about 587 kg / h of a recycled aniline stream and about 345 kg / h of 30 wt.-% HCl, and then about 378 kg / h of an aqueous solution of 50 wt.-% formaldehyde (stream SF) is used in a reactor included in APU to partially convert it to MDA in a continuous process. The reaction mixture is neutralized with about 238 kg / h of 50 wt.-% NaOH and separated into an aqueous phase and an organic phase in a subsequent separation. The organic phase is washed with water to remove remaining traces of NaOH or NaCl, and then the dissolved water and excess aniline (the source of the recycled aniline stream) are evaporated. In this way, a stream S4 of about 1250 kg / h of MDA is obtained.

[0290] The material stream S4 is mixed with approximately 1875 kg / h of monochlorobenzene (MCB), and in a reaction mixing nozzle, it is mixed with a phosgene-containing stream S6 (70 wt.-% phosgene, 30 wt.-% monochlorobenzene) at 4460 kg / h (phosgene in molar excess of 150%). Thereby, the amine groups of MDA are converted into intermediate compounds carbamoyl chloride and amine hydrochloride. These are partially converted into isocyanate (MDI) in the reaction unit RU. In particular, they are converted in the mixing nozzle and partially (almost completely) converted in the downstream reactor cascade and the final reaction column. In the reaction column included in RU, 920 kg / h of HCl, approximately 1872 kg / h of excess phosgene, and some solvent (approx. 532 kg / h) are also discharged in gaseous form at the top of the column. In a distillation storage tank, an approximately 37 wt.-% solution of MDI in MCB at approximately 4258 kg / h is obtained. In a multi-stage distillation, the solvent is removed and the MDI is dechlorinated by heating, and finally, approximately 1578 kg / h of crude MDI is obtained. The gaseous mixture at the top of the column is fed into an absorption column, where the phosgene is scrubbed with approximately 805 kg / h of subcooled MCB, and approximately 920 kg / h of HCl is obtained at the top of the column. The mixture obtained in the storage tank (1872 kg / h of phosgene and 1337 kg / h of MCB) is mixed with approximately 1248 kg / h of fresh phosgene and then serves as the phosgene feed in the reaction mixing nozzle of RU.

[0291] The 1248 kg / h of fresh phosgene is obtained in a heterogeneous gas-phase catalysis on activated carbon. For this purpose, the CO stream (371 kg / h) obtained in a cold box is mixed with approximately 895 kg / h of chlorine gas (approx. 5% excess CO), and is converted into phosgene in a tube bundle reactor (RU P ). Then the phosgene is condensed out and fed into the reaction unit RU.

[0292] By the described method, two carbons in the NCO group and the carbon of the methyl bridge in the MDI compound are completely obtained from CO2. Among the 12 aromatic carbon atoms, statistically 5.17% (the share of benzene based on CO2 in the total benzene amount) corresponds to 0.62 C atoms. In total, 2 + 1 + 0.62 = 3.62 out of 15 carbon atoms are based on CO2, which corresponds to 24.1%.

[0293] Comparative Example 1 A method for preparing polyisocyanate not according to the present invention but as in WO 2021 / 089737

[0294] After applying the method described in WO 2021 / 089737 to the preparation of MDI, 2 out of 15 carbon compounds (carbons in the NCO group) are obtained from CO2, which corresponds to a content of 13.3%.

[0295] Thus, the method according to the present invention significantly increases the proportion of CO2-based carbon in MDI, which makes the method according to the present invention more sustainable than the methods of the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0296] Figure 1 is a schematic diagram of a production unit for a method (production of TDI) according to a preferred embodiment of the present invention.

[0297] The production includes a reaction unit RU for the reverse water gas shift reaction RWGS , an alcohol production unit PU1 (i.e., a methanol production unit), an aromatic production unit PU MTA (i.e., a methanol to aromatic compounds production unit), a nitration reaction unit RU N , an amine production unit APU, a reaction unit RU for phosgenation, a reaction unit RU for preparing phosgene P and a CO-H2 separation cold box CB. The feed streams S1 (CO2) and S2 (H2) are introduced into the RU RWGS and made to react, thereby obtaining a feed stream S3 containing CO and H2 and water as the feed stream SH. A part of S3 is passed through PU1, thereby obtaining a feed stream SM containing methanol. Then the feed stream SM is passed through PU MTA , thereby obtaining a feed stream SA containing toluene and another feed stream BX containing benzene and xylene. The said feed streams are not used in the method for preparing TDI, but can be used for Figure 1 other parallel methods not shown. In addition, it is also conceivable to carry out further demethylation of xylene to produce more toluene. Then the feed stream SA is passed into the RU N to obtain a feed stream SN containing dinitrotoluene, and then the feed stream SN is passed into the APU to carry out hydrogenation with a part of S2. Water is removed from PU1, RU N and APU. A feed stream S4 containing toluenediamine (TDA) is removed from the APU and passed through the RU with S6 containing phosgene in the optional presence of a solvent (preferably MCB). The phosgene in S6 is obtained from the reaction of S5 (source of Cl2) entering the RU P and S CO (purified CO-feed stream removed from the CB (purification unit)). S CH containing H2 is removed from the CB. The crude product TDI is removed from the RU as SP.

[0298] Figure 2 is a schematic diagram of a production unit for a method (production of TDI) according to a preferred embodiment of the present invention.

[0299] The production includes a reaction unit RU for the reverse water gas shift reaction RWGS, an alkane production unit PU2 (i.e., a methane production unit), an aromatic production unit PU MTA (i.e., a methane to aromatic compound production unit), a nitration reaction unit RU N , an amine production unit APU, a reaction unit RU for phosgenation, a reaction unit RU for preparing phosgene P and a CO-H2 separation cold box CB. A part of S1 (CO2) and a part of S2 (H2) are introduced into RU RWGS and made to react to obtain a stream S3 containing CO and H2 and water as stream SH. A part of S1 (CO2) and a part of S2 (H2) are introduced and passed through PU2 to obtain a stream SM' containing methane. Then the stream SM' is passed through PU MTA to obtain a stream SA containing toluene and another stream BX containing benzene and xylene. The streams are not used in the process for preparing TDI, but can be used in Figure 2 other parallel processes not shown. In addition, it is also conceivable to carry out further demethylation of xylene to produce more toluene. Then the stream SA is passed through RU N to obtain a stream SN containing dinitrotoluene, and then the stream SN is passed through APU to be hydrogenated with a part of S2. Water is removed from RU N and APU. A stream S4 containing toluenediamine (TDA) is removed from APU and passed through RU having S6 containing phosgene in the optional presence of a solvent (preferably MCB). The phosgene in S6 is obtained from the reaction of S5 (a source of Cl2) and S CO (a purified CO-stream removed from CB and substantially free of, preferably free of, H2) in RU P . S CH containing H2 is removed from CB. The crude product TDI is removed from RU as SP.

[0300] Figure 3 is a schematic diagram of a production unit for a process (production of a mixture of MDI-monomer + polymeric MDI) according to a preferred embodiment of the present invention.

[0301] Figure 2 The production unit shown in includes the same elements as the production unit of Figure 1 , except that APU includes a hydrogenation unit HU and a condensation reactor R C . In addition, compared with Figure 1 , the production unit includes a reactor RF for preparing formaldehyde. The streams S1 (CO2) and S2 (H2) are introduced into RU RWGSIn and react it to obtain a stream S3 containing CO and H2 and water as stream SH. Pass a part of S3 through PU1 to obtain a stream SM containing methanol. Then pass the stream SM through PU MTA , to obtain a stream SA containing benzene and another stream TX containing toluene and xylene. The stream is not used in the process for preparing MDI, but can be used for Figure 3 other parallel processes not shown. In addition, it is also conceivable to carry out further demethylation of xylene to produce more benzene. Then pass the stream SA through RU N to obtain a stream SN containing nitrobenzene, and then pass the stream SN through HU included in APU to carry out hydrogenation with a part of S2 to obtain a stream S14 containing aniline. Then pass the stream S14 through R C and react with a stream SF containing formaldehyde in the presence of a catalyst, preferably HCl, to obtain a stream S4 containing diaminodiphenylmethane (MDA). Remove water from PU1, RU N and APU. Remove the stream S4 containing MDA from APU and pass it through RU having S6 containing phosgene in the presence of a solvent, preferably MCB. The phosgene in S6 is from S5 (source of Cl2) and S CO (purified CO-stream substantially free of, preferably free of, H2 removed from CB) obtained by reaction in RU P . Remove S CH containing H2 from CB. The formaldehyde in SF is obtained by reacting a part of SM with water and oxygen in R F . Remove the crude product MDI as SP from RU.

[0302] Cited literature

[0303] -WO 2021 / 089737 A1

[0304] -WO 2020 / 239716 A1

[0305] -E.Rezaei,S.Dzuryk"Techno-economic comparison of reverse water gasshift reaction to steam and dry methane reforming reactions for syngasproduction",Chemical Engineering Research and Design,Vol 144(2019),S.354-369

[0306] -EP 2175986

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[0308] -US 8946308

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[0315] -EP 0128400

[0316] -"Ullmann’s Encyclopedia of industrial chemistry",Wiley-VCH Verlag GmbH&Co KGaA,Weinheim,2012&2016:in particular J.Ott et.al."Methanol"(2012&2016);G.Booth"Nitro compounds,Aromatic"Vol.24(2012);T.Kahl et.al."Aniline"Vol.3(2012);and A.W.Franz et.al."Formaldehyde"(2016)

[0317] -Sofiane Arab:"Development of a process for methanol synthesis from CO2".PhD,Université Nancy,2014

[0318] -Laetitia Angelo"Development of catalysts for the carbon dioxide hydrogenation into methanol",PhD Laboratoire des matériaux,surfaces et procédés pour la catalyse,2014

[0319] -EP 0011150

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[0325] - W.O. Haag, R.M. Lago, and P.G. Rodewald, J. Mol. Catal. 17, 161 (1982)

[0326] - R. Le Van Mao, P. Levesque, B. Sjariel, and D.T. Nguyen, Can. J. Chem. Eng. 64, 462 (1986)

[0327] - G. Pop and co-workers, Ind. Eng. Chem. Prod. Res. Dev. 25, 208 - 213 (1986)

[0328] - US 11084764

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[0330] - US 2011060176

[0331] - Ismagilov, Z.R., et al., “Direct Conversion of Methane on Mo / ZSM - 5 Catalysts to Produce Benzene and Hydrogen: Achievements and Perspectives,” Energy & Environmental Science 1, 5 (2008), 526 - 541

[0332] -H. Hermann et al, "Industrial Nitration of Toluene to Dinitrotoluene", in L.F. Albright et al, eds, Nitration: Recent Laboratory and Industrial Developments, ACS Symposium Series 623, Chapter 21 (Washington: American Chemical Society, 1996)

[0333] -WO 2007 / 134771 A1

[0334] -WO 2011 / 111351 A1

[0335] -WO 2013 / 004651 A1

[0336] -WO 2013 / 060628 A1

[0337] -US 2418930

[0338] -WO 2012 / 025483 A1

[0339] -WO 2007137685

[0340] -US 6022634

[0341] -WO 2003 / 31690

[0342] -WO 1999031297

[0343] -EP 1103636

[0344] -US 3236760

[0345] -EP 0004903

[0346] -Ullmann‘s Encyclopedia of industrial chemistry, Chapter,, Phosgene“ 5 th Ed., Vol.A 19, p 413 ff., VCH Verlagsgesellschaft mbH, Weinheim, 1991

[0347] -C.Ryan et.al."Phosgene and related carbonyl halides",ElsevierScience,1996,ISBN 978-0-08-053880-8

Claims

1. A process for preparing at least one polyisocyanate R(-NCO)x from CO2, the process comprising (i) providing a stream S1 comprising CO2; (ii) providing a stream S2 comprising H2; (iii) Pass a part of S1 obtained according to (i) and a part of S2 obtained according to (ii) into the reaction unit RU RWGS and bring them into contact to carry out the reverse water-gas shift reaction, thereby obtaining a stream S3 containing CO and H2 and a stream SH containing H2O; (iv) preparing at least one polyamine R(-NH2)x, where x = 2 or greater, the preparation comprising (iv.1) passing a portion of S3 obtained according to (iii), or a portion of S1 and a portion of S2 obtained respectively according to (i) and (ii), into an alcohol production unit PU1 and contacting the CO and H2 contained in the portion of S3 in PU1, or contacting S1 and S2 in PU1, to obtain a stream SM comprising an alcohol having 1 to 4 carbon atoms; or (iv.1’) passing a portion of S1 and a portion of S2 obtained respectively according to (i) and (ii) into an alkane production unit PU2 and contacting the portion of S1 with the portion of S2 in PU2 to obtain a stream SM’ comprising C1-C4 alkanes; (iv.2) Part of the SM obtained according to (iv.1) or part of the SM' obtained according to (iv.1') is fed into the aromatic production unit PU MTA and the alcohol having 1 to 4 carbon atoms contained in the SM or the C1-C4 alkane contained in the SM' reacts in the PU MTA to obtain a stream SA containing at least one aromatic compound; (iv.3) React the SA obtained according to (iv.2) with nitric acid in the nitration reaction unit RU N to obtain a stream SN containing the corresponding at least one nitrated aromatic compound; (iv.4) passing SN obtained according to (iv.3) into an amine production unit APU and reacting the at least one nitrated aromatic compound contained in SN in APU to obtain a stream S4 comprising at least one polyamine R(-NH2)x; (v) preparing phosgene, the preparation comprising (v.1) providing a stream S5 comprising Cl2; (v.2) Pass a portion of S3 into a purification unit to obtain a stream S containing CO CO and a stream S containing H2 that is lean in CO compared to this portion of S3 CH ; (v.3) At least a part of S obtained according to (v.2) CO is introduced into a reaction unit RU for preparing phosgene P and the said at least part of S CO is contacted with S5 obtained according to (v.1) in RU P to obtain a stream S6 containing phosgene; (vi) passing S4 comprising at least one polyamine R(-NH2)x obtained according to (iv.4) into a reaction unit RU and reacting S4 with phosgene contained in S6 obtained according to (v.3) in RU to obtain a stream SP comprising the at least one polyisocyanate R(-NCO)x.

2. The method according to claim 1, wherein According to (iii), the reverse water gas shift reaction carried out in RU RWGS is carried out at a temperature in the range of 500 °C to 1200 °C, preferably in the range of 700 °C to 1100 °C, more preferably in the range of 800 °C to 1000 °C, more preferably in the range of 850 °C to 1000 °C, still more preferably in the range of 900 °C to 1000 °C.

3. The method according to claim 1 or 2, wherein According to (iii), the reverse water gas shift reaction carried out in RU RWGS is carried out at a pressure in the range of 0.5 to 20 bar (absolute pressure), preferably in the range of 2 to 18 bar (absolute pressure), more preferably in the range of 2 to 15 bar (absolute pressure).

4. The method according to any one of claims 1 to 3, wherein, (iii) comprises (iii.1) A part of S1 obtained according to (i) and a part of S2 obtained according to (ii) are introduced into the reaction unit RU RWGS and brought into contact therewith to carry out the reverse water gas shift reaction, thereby obtaining a stream S13 containing CO, CO2, H2 and H2O; (iii.2) cooling the stream S13 obtained according to (iii.1) in a condensation unit CU to obtain a gaseous stream S3 comprising CO and H2 that is leaner in water than S13, and a liquid stream SH comprising H2O; or (iii.2’) comprises (iii.2’.1) cooling the stream S13 obtained according to (iii.1) in a condensation unit CU to obtain a gaseous stream S23 comprising CO and H2 that is leaner in water than S13, and a liquid stream SH comprising H2O; (iii.2’.2) passing S23 obtained according to (iii.2’.1) into an amine scrubbing unit to remove CO2 to obtain a gaseous stream S3 comprising CO and H2 that is leaner in CO2 than S23.

5. The method according to any one of claims 1 to 4, wherein, PU1 comprises an alcohol production reactor, where (iv.1) comprises passing a portion of S3 into PU1 and contacting the CO and H2 contained in the portion of S3 with a catalyst in the alcohol production reactor at a temperature in the range of 150°C to 500°C, preferably in the range of 180°C to 320°C, more preferably in the range of 200°C to 300°C, even more preferably in the range of 205°C to 280°C, to obtain a stream SM comprising an alcohol having 1 to 4 carbon atoms.

6. The method according to any one of claims 1 to 4, wherein PU2 includes an alkane production reactor, wherein (iv.1’) includes Passing a portion of S1 and a portion of S2 into PU2 and bringing the CO2 contained in the portion of S1 and the H2 contained in the portion of S2 into contact in the alkane production reactor PU2 at a temperature in the range of 250°C to 600°C, preferably in the range of 280°C to 500°C, more preferably in the range of 300°C to 400°C, thereby obtaining a stream SM’ containing C1-C4 alkanes.

7. The method according to any one of claims 1 to 6, wherein (iv.2) includes A part of the SM obtained according to (iv.1) or a part of the SM' obtained according to (iv.1') is passed into the aromatic production unit PU MTA and brought into contact with the catalyst in the aromatic production unit, thereby obtaining a stream SA comprising at least one aromatic compound selected from the group consisting of benzene, toluene, and xylene, more preferably benzene or toluene.

8. The method according to claim 7, wherein, When carrying out (iv.1), (iv.2) includes (iv.2.1) Pass a part of the SM obtained according to (iv.1) into at least one aromatic conversion reactor included in the PU MTA ; preferably at least one methanol-to-aromatic compound conversion reactor; (iv.2.2) Bringing the stream SM into contact with a catalyst in the at least one reactor, preferably at a temperature in the range of 250°C to 750°C, preferably in the range of 300°C to 600°C, thereby obtaining a stream SA1 containing water and a mixture of aromatic compounds, which aromatic compounds are benzene, toluene, and xylene; (iv.2.3) Passing the stream SA1 obtained according to (iv.2.2) into a separation unit SU, thereby obtaining a stream SA containing benzene or toluene; or wherein, when carrying out (iv.1’), (iv.2) includes (iv.2.1’) Passing a portion of SM’ obtained according to (iv.1’) into at least one aromatic conversion reactor, more preferably at least one methane-to-aromatic compound conversion reactor; (iv.2.2’) Bringing the stream SM’ into contact with a catalyst in the at least one reactor, more preferably at a temperature in the range of 600°C to 1000°C, more preferably in the range of 625°C to 900°C, more preferably in the range of 650°C to 850°C, thereby obtaining a stream SA1’ containing a mixture of aromatic compounds, which aromatic compounds are benzene, toluene, and xylene; (iv.2.3’) Passing the stream SA1’ obtained according to (iv.2.2’) into a separation unit SU’, thereby obtaining a stream SA containing benzene or toluene.

9. The method according to any one of claims 1 to 8, wherein, (iv.3) includes React the SA obtained according to (iv.2) with nitric acid in the nitration reaction unit RU N to obtain a stream SN comprising the corresponding at least one nitrated aromatic compound, wherein preferably, the at least one nitrated aromatic compound is selected from the group consisting of nitrobenzene and dinitrotoluene.

10. The method according to any one of claims 1 to 9, wherein, (iv.4) includes Passing SN obtained according to (iv.3) into an amine production unit APU serving as a hydrogenation unit and bringing the at least one nitrated aromatic compound contained in SN into contact with H2 in the hydrogenation unit, thereby obtaining a stream S4 containing at least one corresponding aromatic polyamine R(-NH2)x.

11. The method according to claim 10, wherein, (iv.4) includes (iv.4.1) Passing SN containing dinitrotoluene obtained according to (iv.3) into a hydrogenation unit HU under hydrogenation conditions, thereby obtaining a stream S4 containing toluenediamine (TDA).

12. The method according to any one of claims 1 to 9, wherein (iv.4) includes (iv.4.1’) Preparing an aqueous stream SF containing formaldehyde; (iv.4.2’) Passing SN obtained according to (iv.3) into a hydrogenation unit included in an amine production unit APU under hydrogenation conditions, thereby obtaining a stream S14 containing aniline; (iv.4.3’) Contact S14 obtained according to (iv.4.2’) with SF obtained according to (iv.4.1’) in a condensation reactor R included in the APU C in the presence of a catalyst, preferably an acidic catalyst, more preferably hydrochloric acid, to obtain a stream S4 comprising one or more of monomeric methylene diphenyl diisocyanate and polymethylene polyphenylene polyisocyanate.

13. The method according to claim 12, wherein, (iv.4.1’) includes Passing a portion of SM obtained according to (iv.1) into a reactor for preparing formaldehyde in the presence of H2O and O2, thereby obtaining an aqueous stream SF containing formaldehyde.

14. The method according to any one of claims 1 to 13, wherein, This purification unit according to (v.2) is the CO-H2 separation cold box CB.

15. The method according to any one of claims 1 to 14, wherein (v.3) includes At least a part of S obtained according to (v.2), more preferably S obtained according to (v.2) CO is fed into a reaction unit RU for preparing phosgene CO and the said part of S3 is contacted with S5 obtained according to (v.1) in RU P in the presence of a catalyst, preferably activated carbon, to obtain a stream S6 containing phosgene. P ​ 16. The method according to any one of claims 1 to 15, wherein, (vi) includes (vi.1) Introduce S4 containing at least one polyamine R(-NH2)x obtained according to (iv.4), S6 obtained according to (v), and optionally a solvent into a mixing device, preferably a mixing nozzle, included in the reaction unit RU, where the solvent is preferably an aromatic solvent, more preferably a halogenated aromatic solvent, even more preferably monochlorobenzene or dichlorobenzene, to obtain a reaction mixture; (vi.2) Pass the reaction mixture obtained according to (vi.1) into one or more reactors included in RU to obtain a stream SP containing the at least one polyisocyanate R(-NCO)x.

17. A production unit for carrying out the method according to any one of claims 1 to 16, the production unit comprising: - Reaction unit R RWGS , which is used for the reverse water-gas shift reaction to obtain S3 containing CO and H2; - Device for introducing CO2 into R RWGS ; - Device for introducing H2 into R RWGS ; - Device for removing S3 from R RWGS Device for removing S3 from R - An alcohol production unit PU1 for obtaining SM or an alkane production unit PU2 for obtaining SM'; - A device for passing a part of S3 into PU1; - A device for passing a part of S1 into PU2; - A device for removing SM from PU1 or for removing SM' from PU2; - Aromatic production unit PU MTA , which is used to obtain a stream SA containing at least one aromatic compound; - Device for introducing SM or SM' into PU MTA in it; - Nitration reaction unit RU N which is used to obtain a stream SN comprising at least one nitrated aromatic compound; - Device for removing SN from RU N Device for removing SN from RU - An amine production unit APU for obtaining a stream S4 containing at least one polyamine R(-NH2)x, where x = 2 or greater; - A device for passing SN into APU; - Reaction unit RU P , which is used to prepare phosgene as stream S6; - Device for introducing S5 into RU P in; - A purification unit, preferably a CO-H2 separation cold box, for obtaining stream S CO ; - Device for introducing S CO into RU P ; - Device for removing S from this purification unit CO ; - Device for removing S from this purification unit CH ; - Apparatus for introducing a portion of S3 into the purification or R UP ; - Device for removing S6 from R UP and the device for removing S6 from R - A reaction unit RU for obtaining a stream SP containing at least one corresponding polyisocyanate R(-NCO)x; - A device for passing S4 into RU; - A device for passing S6 into RU; - A device for removing SP from RU.

18. A polyisocyanate R(-NCO)x, characterized in that, At least 22.5%, preferably at least 30%, more preferably at least 50% of its carbon atoms are obtained from CO2; preferably, the polyisocyanate R(-NCO)x can be obtained or is obtained by the method according to any one of claims 1 to 16.

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