Process for preparing mda

Abstract

The present invention relates to a process for preparing methylenedianiline and a production unit for carrying out said process for preparing methylenedianiline.

Description

[0001] Process for preparing MDA

[0002] The present invention relates to a process for preparing methylenedianiline and a production unit for carrying out said process for preparing methylenedianiline.

[0003] Methylenedianiline, or diamniophenylmethane, abbreviated as MDA, which refers to individual methylenedianiline isomers, methylenedianiline isomer mixture and / or oligomers of methylenedianiline, is an intermediate product for the production of polyisocyanates and resins. Several processes for preparing MDA are known in the art. For example, WO01 / 74755 A1 discloses a process for preparing mixtures of methylenedianiline which comprises reacting aniline and formaldehyde to form aminal in the absence of an acid catalyst and isomerizing the aminal in one or more reactors in the presence of a solid catalyst selected from zeolite and a silico-alumina at a temperature of from 100 to 250°C. W02010 / 072504 A1 discloses a process for providing methylene-bridged polyphenyl polyamines comprising condensing aniline and formaldehyde, obtaining a condensate, reacting said condensate with a solid catalyst at a temperature in the range of from 30 to 100 °C, obtaining an intermediate mixture and converting the intermediate mixture at a temperature in the range of 70 to 250°C into the methylene-bridged polyphenyl polyamines in presence of a subsequent solid catalyst. Further, processes using an acid catalyst such as HCI are also known in the art. For example, HCI can be added after the production of aminal as in US2016068474 A1. Alternatively, HCI can be added to aniline before formaldehyde or together with formaldehyde as disclosed in EP 2145874 A1 , EP 2000459 A1 , DE10141620 and DE19804915. Another process for preparing MDA is disclosed in EP 0109931 A2, said process comprising mixing an aminal stream (uncatalyzed condensation) with an acidic condensate (HCI catalyzed condensation) and a final rearrangement of the mixture. The goal of EP 0109931 was to minimize HCI consumption in the process. However, there is a disadvantage of using said process as there is an increased side-product formation.

[0004] Therefore, there is always a need to provide improved processes able to circumvent problems encountered in the previous processes and improve the production capacity while being cost effective.

[0005] In particular, it has been demonstrated that the process of the present invention permits to improve the 4,4'- MDA yield while saving the acid catalyst, such as HCI.

[0006] Therefore, the present invention relates to a process for preparing methylenedianiline, the process comprising

[0007] (i) preparing a stream S1 comprising aminal, where (i) comprises (1.1) providing a stream S01 comprising aniline;

[0008] (1.2) providing an aqueous stream S02 comprising formaldehyde;

[0009] (1.3) bringing in contact at least a portion of S01 provided according to (i.1) with at least a portion of S02 provided according to (i.2) in a first reactor unit RU1, obtaining a mixture M1 having an organic phase comprising aminal and aniline, and having an aqueous phase comprising water;

[0010] (1.4) passing M1 obtained according to (i.3) through a separation unit Sil for separating the phases of M1 , obtaining a stream S1 comprising the organic phase comprising aminal and aniline, and a stream S11 comprising the aqueous phase comprising water;

[0011] (ii) passing the stream S1 prepared according (i) in a second reactor unit RU2, RU2 comprising an heterogeneous catalyst C, and bringing in contact S1 with C in RU2, obtaining a stream S2 comprising aminobenzylaniline;

[0012] (iii) bringing in contact S2 obtained according to (ii) with a liquid mixture ML comprising a Bronsted acid, obtaining a stream S3 comprising S2 and ML;

[0013] (iv) passing S3 obtained according to (iii) into a third reactor unit RU3 and subjecting S3 to rearrangement conditions in RU3, obtaining a stream S4 comprising methylenedianiline.

[0014] Preferably the first reactor unit RU1 is one or more of a tank, a stirred tank, and a plug flow reactor.

[0015] Preferably upstream of the one or more of a tank, a stirred tank and a plug flow reactor, RU1 further comprises a mixing device, the mixing device being static (nozzle) or dynamic mixers or T-junction.

[0016] Preferably the aniline comprised in S01 is fresh aniline and / or recycled aniline.

[0017] Preferably the stream S01 comprising aniline is non-aqueous.

[0018] Preferably from 20 to 70 weight-%, more preferably from 25 to 60 weight-%, more preferably from 30 to 50 weight-%, of S02 consist of formaldehyde.

[0019] Preferably, according to (i.3), bringing in contact S01 provided according to (i.1) with S02 provided according to (i.2) in a first reactor unit RU1 is performed at a temperature in the range of from 20 to 100 °C, more preferably in the range of from 30 to 95 °C, more preferably in the range of from 40 to 90 °C. Preferably, according to (i.3), bringing in contact S01 provided according to (i.1) with S02 provided according to (i.2) in a first reactor unit RU1 is performed at a pressure in the range of from 0.5 to 10 bar(abs), more preferably in the range of from 0.6 to 5 bar(abs), more preferably in the range of from 0.7 to 2 bar(abs).

[0020] Preferably the molar ratio of aniline to formaldehyde in Rll 1 is in the range of from 1 .5: 1 to 10: 1 , more preferably in the range of from 1.8:1 to 6:1 , more preferably in the range of from 2:1 to 4:1.

[0021] Preferably the separation unit used according to (i.4) is a liquid-liquid separation unit, more preferably said separation unit being one or more of a decanter, a centrifuge, a cyclone and a settler, more preferably one or more of a decanter and a centrifuge, more preferably a decanter.

[0022] Preferably the second reactor unit RU2 comprises one or more fixed-bed reactors.

[0023] Optionally the one or more fixed-bed reactors are one or more cooled fixed-bed reactors. Alternatively, optionally, the second reactor unit RU2 further comprises one or more heat exchangers located in-between the fixed-bed reactors or in a loop around.

[0024] Preferably bringing in contact S1 with C in RU2 according to (ii) is performed at a temperature in the range of from 15 to 200°C, preferably in the range of from 20 to 180°C, more preferably in the range of from 30 to 160°C.

[0025] More preferably bringing in contact S1 with C in RU2 according to (ii) is performed at a temperature in the range of from 30 to 100°C, more preferably in the range of from 40 to 75 °C.

[0026] This step (ii) permits to convert aminal to ABA, and optionally to additionally re-arrange a portion of ABA to MDA.

[0027] Preferably bringing in contact S1 with C in RU2 according to (ii) is performed at a pressure higher than the vapor pressure of the reaction mixture, more preferably higher than at least 0.01 bar, more preferably higher than at least 0.1 bar, more preferably higher than at least 1 bar compared to the reaction mixture pressure.

[0028] As to the pressure in (ii), any pressure can be applied. Preferably, the pressure applied in (ii) is sufficient to provide for liquid phase reaction conditions.

[0029] Any heterogeneous catalyst known in the art can be used provided that they are adapted to catalyze the reaction in (ii). Preferably the heterogeneous catalyst C is one or more of one or more of a zeolitic material, a non-zeolitic oxidic material, an ion exchanger and activated carbon, more preferably a zeolitic material or a non-zeolitic oxidic material.

[0030] Preferably the non-zeolitic oxidic material comprises an oxidic support, wherein the oxidic support comprises an element Ei selected from the group consisting of Ti, Zr, Al, Si, and mixtures of two or more thereof, and the non-zeolitic oxidic material further comprises a supported material supported on the oxidic support, wherein the supported material comprises one or more of Ti, Zr, V, Nb, Ta, Mo, W, Ge, Sn, Sc, Y, La, Ce, Nd, Pr, Hf, Cr, Fe, Co, Ni, Cu, Zn and Pb. More preferably, the non-zeolitic oxidic material comprises an oxidic support, wherein the oxidic support comprises an element Ei selected from the group consisting of Al, Si, and mixtures of two or more thereof, and the non-zeolitic oxidic material further comprises a supported material supported on the oxidic support, wherein the supported material comprises one or more of Hf, Fe, and Zn. More preferably the non-zeolitic oxidic material is Fe supported silica-alumina support. Such catalyst is disclosed in WO 2021 / 116419.

[0031] Other catalysts as disclosed in the prior art such as in WO 2021 / 116419 A1 can be used as the catalyst C.

[0032] In the context of the present invention, preferably the stream S2 further comprises aniline.

[0033] Preferably, (ii) comprises

[0034] (11.1) passing the stream S1 prepared according (i) in a second reactor unit RU2, RU2 comprising an heterogeneous catalyst C, and bringing in contact S1 with C in RU2, obtaining a stream S21 comprising aminobenzylaniline and aniline;

[0035] (11.2) passing S21 obtained according to (ii.1) into a separation unit SUA, obtaining a stream S2, depleted in aniline compared to S21 , comprising aminobenzylaniline and a stream S22 comprising aniline.

[0036] In the context of the present invention, MDA can already be present in S2.

[0037] Preferably the content of aniline in S2 is lower than the content of aniline in S21.

[0038] Preferably the aminobenzylamine comprised in S2 comprises one or more of para- aminobenzylamine (p-ABA), ortho- aminobenzylamine (o-ABA) and polymeric ABA structures.

[0039] Preferably the separation unit SUA is a distillation unit or an evaporation unit. Preferably (ii) further comprises

[0040] (ii.3) recycling S22 obtained according to (ii .2) as a portion of S01 into (i.3).

[0041] Preferably the Bronsted acid comprised in ML is one or more of hydrochloric acid, sulfuric acid and phosphoric acid, more preferably hydrochloric acid.

[0042] Preferably, the liquid mixture ML used in (iii) is an aqueous mixture comprising a Bronsted acid, more preferably HCI.

[0043] Preferably ML comprises, more preferably consists of water and HCI. Preferably from 10 to 70 weight-%, more preferably from 20 to 65 weight-%, more preferably from 30 to 60 weight-%, of the liquid mixture used in (iii) consists of HCI.

[0044] Alternatively, the liquid mixture ML preferably further comprises aminobenzylaniline.

[0045] According to said alternative, the process preferably further comprises preparing the liquid mixture ML comprising a Bronsted acid, more preferably HCI, and aminobenzylaniline, comprising bringing in contact aniline, more preferably a portion of S01 provided in (i.1), with an aqueous solution of the Bronsted acid, obtaining a liquid mixture M10 comprising aniline, water and the Bronsted acid; introducing M10 into a reactor unit RUA together with formaldehyde, more preferably a portion of S02 provided in (i.2); reacting M10 with the formaldehyde in RUA, obtaining the liquid mixture ML comprising aminobenzylaniline and the Bronsted acid.

[0046] Preferably the molar ratio of the Bronsted acid to aniline is in the range of from 0.05:1 to 0.75:1 , more preferably in the range of from 0.07:1 to 0.5:1 , more preferably in the range of from 0.08:1 to 0.3:1.

[0047] Preferably the process of the present invention comprises

[0048] (i) preparing a stream S1 comprising aminal, where (i) comprises

[0049] (1.1) providing a stream S01 comprising aniline;

[0050] (1.2) providing an aqueous stream S02 comprising formaldehyde;

[0051] (1.3) bringing in contact at least a portion of S01 provided according to (i.1) with at least a portion of S02 provided according to (i.2) in a first reactor unit RU1 , obtaining a mixture M1 having an organic phase comprising aminal and aniline and having an aqueous phase comprising water;

[0052] (i.4) passing M1 obtained according to (i.3) through a separation unit Sil for separating the phases of M1 , obtaining a stream S1 comprising the organic phase comprising aminal and aniline, and a stream S11 comprising the aqueous phase comprising water;

[0053] (ii) passing the stream S1 prepared according (i) in a second reactor unit RU2, RU2 comprising an heterogeneous catalyst C, and bringing in contact S1 with C in RU2, obtaining a stream S2 comprising aminobenzylaniline;

[0054] (iii) bringing in contact S2 obtained according to (ii) with a liquid mixture ML comprising a Bronsted acid and aminobenzylaniline, obtaining a stream S3 comprising S2 and ML;

[0055] (iv) passing S3 obtained according to (iii) into a third reactor unit RU3 and subjecting S3 to rearrangement conditions in RU3, obtaining a stream S4 comprising methylenedianiline: wherein the process further comprises preparing the liquid mixture ML comprising the Bronsted acid and aminobenzylaniline, comprising: bringing in contact aniline, more preferably a portion of S01 provided in (i.1 ) , with an aqueous solution of the Bronsted acid, obtaining a liquid mixture M10 comprising aniline, water and HCI; introducing M10 into a reactor unit RUA together with formaldehyde, more preferably a portion of S02 provided in (i.2); reacting M10 with the formaldehyde in RUA, obtaining the liquid mixture ML comprising aminobenzylaniline and the Bronsted acid.

[0056] Preferably bringing in contact aniline, more preferably a portion of S01 provided in (i.1 ), with an aqueous solution of the Bronsted acid is performed in a unit UC, UC being one or more of a nozzle, a pipe, a tank and a stirred tank.

[0057] Preferably, prior to be introduced into RUA, the process further comprises heating M10 to a temperature in the range of from 20 to 95 °C, more preferably in the range of from 30 to 90 °C. Preferably the reactor unit RUA is one or more unstirred or stirred tanks or one or more plug flow reactors, more preferably one or more stirred tanks.

[0058] Preferably the one or more unstirred or stirred tanks have one or more external loops, such loops being used to remove heat and optionally add formaldehyde.

[0059] In the context of the present invention, preferably RUA further comprise one or more cooling devices such as heat exchangers. Alternatively, preferably the tanks or reactors comprised in RUA are cooled tanks or reactors, respectively. Preferably introducing M10 into a reactor unit RUA together with formaldehyde, more preferably a portion of S02 provided in (i.2) and reacting M 10 with the formaldehyde in RUA are continuous steps or semi-batch steps, more preferably semi-batch steps.

[0060] Preferably the molar ratio of aniline to formaldehyde in RUA is in the range of from 1.5:1 to 4.5:1, more preferably in the range of from 1.6:1 to 4:1, more preferably in the range of from 1.7:1 to 3:1.

[0061] Preferably reacting M10 and the formaldehyde in RUA is performed at a temperature in the range of from 30 to 90 °C, preferably in the range of from 40 to 70 °C.

[0062] Preferably reacting M10 and the formaldehyde in RUA is performed at a pressure in the range of from 0.1 to 10 bar(abs), more preferably in the range of from 0.5 to 2 bar(abs).

[0063] Preferably from 20 to 90 weight-%, more preferably from 50 to 85 weight-%, of the liquid mixture ML consist of aminobenzylaniline.

[0064] Preferably, in S3, the ratio of the mass of aminobenzylaniline (ABA) comprised in S2 relative to the mass of aminobenzylaniline (ABA) comprised ML is in the range of from 10:1 to 1 :10, more preferably in the range of from 1 :1 to 1 :6, more preferably in the range of from 1:2 to 1 :4.

[0065] Preferably bringing in contact S2 obtained according to (ii) with ML according to (iii) is performed in a T-junction, a tank or a stirred tank.

[0066] Preferably the third reactor unit RU3 comprises one or more tanks or one or more plug flow reactors, more preferably one or more plug flow reactors.

[0067] Preferably, when RU3 comprises more than one tank or more than one plug flow reactor, the tanks / reactors are arranged in series.

[0068] Preferably subjecting S3 to rearrangement conditions in RU3 comprising subjecting S3 to a temperature in the range of from 80 to 200 °C, more preferably in the range of from 100 to 160°C, more preferably in the range of from 120 to 140°C.

[0069] Preferably subjecting S3 to rearrangement conditions in RU3 comprising subjecting S3 to a pressure in the range of from 0.5 to 10 bar(abs), more preferably in the range of from 0.8 to 5 bar(abs), more preferably in the range of from 1 to 3 bar(abs).

[0070] Preferably the process further comprises (v) subjecting S4 obtained according to (iv) to one or more purification steps.

[0071] The present invention further relates to a production unit for carrying out a process for preparing methylenedianiline, preferably the process for preparing methylenedianiline according to the present invention, the unit comprising a first reactor unit RU1; a means for introducing at least a portion of stream S01 into RU1 ; a means for introducing at least a portion of liquid stream S02 into RU1 ; a means for removing mixture M1 from RU1; a separation unit Sil; a second reactor unit RU2 comprising a heterogeneous catalyst C; a means for introducing stream S1 into RU2; a means for bringing in contact stream S2 with liquid mixture ML; a reaction unit RU3; a means for introducing stream S3 into RU3; a means for removing stream S4 from RU3.

[0072] Preferably the first reactor unit RU1 is one or more of a tank, a stirred tank, and a plug flow reactor.

[0073] Preferably upstream of the one or more of a tank, a stirred tank and a plug flow reactor, RU1 further comprises a mixing device, the mixing device being static (nozzle) or dynamic mixers or T-junction.

[0074] Preferably the separation unit Sil is a liquid-liquid separation unit, more preferably said separation unit being one or more of a decanter, a centrifuge, a cyclone and a settler, more preferably one or more of a decanter and a centrifuge, more preferably a decanter.

[0075] Preferably the second reactor unit RU2 comprises one or more fixed-bed reactors.

[0076] Optionally the one or more fixed-bed reactors are one or more cooled fixed-bed reactors. Alternatively, optionally, the second reactor unit RU2 further comprises one or more heat exchangers located in-between the fixed-bed reactors or in a loop around.

[0077] Preferably the means for bringing in contact S2 with ML is a T-junction, a tank or a stirred tank.

[0078] Preferably the production unit further comprises a separation unit SUA. Preferably the separation unit SUA is a distillation unit or an evaporation unit.

[0079] Preferably the production unit further comprises a reactor unit RUA; a means for introducing M10 into RUA; a means for removing ML from RUA.

[0080] Preferably the reactor unit RUA is one or more unstirred or stirred tanks or one or more plug flow reactors, more preferably one or more stirred tanks.

[0081] Preferably the one or more unstirred or stirred tanks have one or more external loops, such loops being used to remove heat and optionally add formaldehyde.

[0082] In the context of the present invention, preferably RUA further comprises one or more cooling devices such as heat exchangers. Alternatively, preferably the tanks or reactors comprised in RUA are cooled tanks or reactors, respectively.

[0083] Preferably the third reactor unit RU3 comprises one or more tanks or one or more plug flow reactors, more preferably one or more plug flow reactors.

[0084] Preferably, when RU3 comprises more than one tank or more than one plug flow reactor, the tanks / reactors are arranged in series.

[0085] The present invention is further illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and back-references as indicated. In particular, it is noted that in each instance where a range of embodiments is mentioned, for example in the context of a term such as "The process of any one of embodiments 1 to 4", every embodiment in this range is meant to be explicitly disclosed for the skilled person, i.e. the wording of this term is to be understood by the skilled person as being synonymous to "The process of any one of embodiments 1 , 2, 3 and 4". Further, it is explicitly noted that the following set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.

[0086] 1 . A process for preparing methylenedianiline, the process comprising

[0087] (i) preparing a stream S1 comprising aminal, (i) comprising

[0088] (1.1) providing a stream S01 comprising aniline;

[0089] (1.2) providing an aqueous stream S02 comprising formaldehyde; (1.3) bringing in contact at least a portion of S01 provided according to (i.1) with at least a portion of S02 provided according to (i.2) in a first reactor unit RU1 , obtaining a mixture M1 having an organic phase comprising aminal and aniline, and having an aqueous phase comprising water;

[0090] (1.4) passing M1 obtained according to (i.3) through a separation unit Sil for separating the phases of M1 , obtaining a stream S1 comprising the organic phase comprising aminal and aniline, and a stream S11 comprising the aqueous phase comprising water;

[0091] (ii) passing the stream S1 prepared according (i) in a second reactor unit RU2, RU2 comprising an heterogeneous catalyst C, and bringing in contact S1 with C in RU2, obtaining a stream S2 comprising aminobenzylaniline;

[0092] (iii) bringing in contact S2 obtained according to (ii) with a liquid mixture ML comprising a Bronsted acid, obtaining a stream S3 comprising S2 and ML;

[0093] (iv) passing S3 obtained according to (iii) into a third reactor unit RU3 and subjecting S3 to rearrangement conditions in RU3, obtaining a stream S4 comprising methylenedianiline.

[0094] 2. The process of embodiment 1 , wherein the first reactor unit RU1 is one or more of a tank, a stirred tank, and a plug flow reactor.

[0095] 3. The process of embodiment 1 or 2, wherein from 20 to 70 weight-%, preferably from 25 to 60 weight-%, more preferably from 30 to 50 weight-%, of S02 consist of formaldehyde.

[0096] 4. The process of any one of embodiments 1 to 3, wherein, according to (i.3), bringing in contact S01 provided according to (i.1) with S02 provided according to (i.2) in a first reactor unit RU1 is performed at a temperature in the range of from 20 to 100 °C, preferably in the range of from 30 to 95 °C, more preferably in the range of from 40 to 90 °C.

[0097] 5. The process of any one of embodiments 1 to 4, wherein, according to (i.3), bringing in contact S01 provided according to (i.1) with S02 provided according to (i.2) in a first reactor unit RU1 is performed at a pressure in the range of from 0.5 to 10 bar(abs), preferably in the range of from 0.6 to 5 bar(abs), more preferably in the range of from 0.7 to 2 bar(abs).

[0098] 6. The process of any one of embodiments 1 to 5, wherein the molar ratio of aniline to formaldehyde in RU1 is in the range of from 1.5:1 to 10:1 , preferably in the range of from 1.8:1 to 6:1 , more preferably in the range of from 2:1 to 4:1. The process of any one of embodiments 1 to 6, wherein the separation unit used according to (i.4) is a liquid-liquid separation unit, preferably said separation unit being one or more of a decanter, a centrifuge, a cyclone and a settler, more preferably one or more of a decanter and a centrifuge, more preferably a decanter. The process of any one of embodiments 1 to 7, wherein the second reactor unit RU2 comprises one or more fixed-bed reactors. The process of any one of embodiments 1 to 8, wherein bringing in contact S1 with C in RU2 according to (ii) is performed at a temperature in the range of from 15 to 200°C, preferably in the range of from 20 to 180°C, more preferably in the range of from 30 to 160°C. The process of any one of embodiments 1 to 9, wherein the heterogeneous catalyst C is one or more of one or more of a zeolitic material, a non-zeolitic oxidic material, an ion exchanger and activated carbon, preferably a zeolitic material or a non-zeolitic oxidic material. The process of any one of embodiments 1 to 10, wherein (ii) comprises

[0099] (11.1) passing the stream S1 prepared according (i) in a second reactor unit RU2, RU2 comprising an heterogeneous catalyst C, and bringing in contact S1 with C in RU2, obtaining a stream S21 comprising aminobenzylaniline and aniline;

[0100] (11.2) passing S21 obtained according to (ii.1) into a separation unit SUA, obtaining a stream S2, depleted in aniline compared to S21 , comprising aminobenzylaniline and a stream S22 comprising aniline. The process of embodiment 11, wherein (ii) further comprises

[0101] (11.3) recycling S22 obtained according to (ii.2) as a portion of S01 into (i.3). The process of any one of embodiments 1 to 12, wherein the Bronsted acid comprised in ML is one or more of hydrochloric acid, sulfuric acid and phosphoric acid, preferably hydrochloric acid. The process of any one of embodiments 1 to 13, wherein the liquid mixture ML further comprises aminobenzylaniline. The process of embodiment 14, further comprising preparing the liquid mixture ML comprising a Bronsted acid, preferably HCI, and aminobenzylaniline, comprising bringing in contact aniline, preferably a portion of S01 provided in (i.1 ), with an aqueous solution of the Bronsted acid, obtaining a liquid mixture M10 comprising aniline, water and the Bronsted acid; introducing M10 into a reactor unit RUA together with formaldehyde, preferably a portion of S02 provided in (i.2); reacting M10 with the formaldehyde in RUA, obtaining the liquid mixture ML comprising aminobenzylaniline and the Bronsted acid.

[0102] 16. The process of embodiment 15, wherein, prior to be introduced into RUA, the process further comprises heating M10 to a temperature in the range of from 20 to 95 °C, preferably in the range of from 30 to 90 °C.

[0103] 17. The process of embodiment 15 or 16, wherein the reactor unit RUA is one or more unstirred or stirred tanks or one or more plug flow reactors, preferably one or more stirred tanks.

[0104] 18. The process of any one of embodiments 15 to 17, wherein the molar ratio of aniline to formaldehyde in RUA is in the range of from 1.5:1 to 4.5:1 , preferably in the range of from 1.6:1 to 4:1 , more preferably in the range of from 1.7:1 to 3:1.

[0105] 19. The process of any one of embodiments 15 to 18, wherein reacting M 10 and the formaldehyde in RUA is performed at a temperature in the range of from 30 to 90 °C, preferably in the range of from 40 to 70 °C.

[0106] 20. The process of any one of embodiments 15 to 19, wherein reacting M10 and the formaldehyde in RUA is performed at a pressure in the range of from 0.1 to 10 bar(abs), preferably in the range of from 0.5 to 2 bar(abs).

[0107] 21 . The process of any one of embodiments 15 to 20, wherein from 20 to 90 weight-%, preferably from 50 to 85 weight-%, of the liquid mixture ML consist of aminobenzylaniline.

[0108] 22. The process of any one of embodiments 15 to 21 , wherein, in S3, the ratio of the mass of aminobenzylaniline (ABA) comprised in S2 relative to the mass of aminobenzylaniline (ABA) comprised ML is in the range of from 10:1 to 1 :10, preferably in the range of from 1 :1 to 1 :6, more preferably in the range of from 1 :2 to 1 :4. 23. The process of any one of embodiments 1 to 22, wherein bringing in contact S2 obtained according to (ii) with ML according to (iii) is performed in a T-junction, a tank or a stirred tank.

[0109] 24. The process of any one of embodiments 1 to 23, wherein the third reactor unit RU3 comprises one or more tanks or one or more plug flow reactors, preferably one or more plug flow reactors.

[0110] 25. The process of any one of embodiments 1 to 24, wherein subjecting S3 to rearrangement conditions in RU3 comprising subjecting S3 to a temperature in the range of from 80 to 200 °C, preferably in the range of from 100 to 160°C, more preferably in the range of from 120 to 140°C.

[0111] 26. The process of any one of embodiments 1 to 25, wherein subjecting S3 to rearrangement conditions in RU3 comprising subjecting S3 to a pressure in the range of from 0.5 to 10 bar(abs), preferably in the range of from 0.8 to 5 bar(abs), more preferably in the range of from 1 to 3 bar(abs).

[0112] 27. The process of any one of embodiments 1 to 26, further comprising

[0113] (v) subjecting S4 obtained according to (iv) to one or more purification steps.

[0114] 28. A production unit for carrying out a process for preparing methylenedianiline, preferably the process for preparing methylenedianiline according to any one of embodiments 1 to 27, the unit comprising a first reactor unit RU1; a means for introducing at least a portion of stream S01 into RU1 ; a means for introducing at least a portion of liquid stream S02 into RU1 ; a means for removing mixture M1 from RU1 ; a separation unit Sil; a second reactor unit RU2 comprising a heterogeneous catalyst C; a means for introducing stream S1 into RU2; a means for bringing in contact steam S2 with liquid mixture ML; a reaction unit RU3; a means for introducing stream S3 into RU3; a means for removing stream S4 from RU3.

[0115] 29. The production unit of embodiment 28, wherein the first reactor unit RU1 is one or more of a tank, a stirred tank, and a plug flow reactor. 30. The production unit of embodiment 28 or 29, wherein the separation unit Sil is a liquidliquid separation unit, preferably said separation unit being one or more of a decanter, a centrifuge, a cyclone and a settler, more preferably one or more of a decanter and a centrifuge, more preferably a decanter.

[0116] 31 . The production unit of any one of embodiments 28 to 30, wherein the second reactor unit RU2 comprises one or more fixed-bed reactors.

[0117] 32. The production unit of any one of embodiments 28 to 30, further comprising a separation unit SUA.

[0118] 33. The production unit of any one of embodiments 1 to 32, further comprising a reactor unit RUA; a means for introducing M10 into RUA; a means for removing ML from RUA.

[0119] 34. The production unit of embodiment 33, wherein the reactor unit RUA is one or more unstirred or stirred tanks or one or more plug flow reactors, preferably one or more stirred tanks.

[0120] 35. The process of any one of embodiments 28 to 34, wherein the third reactor unit RU3 comprises one or more tanks or one or more plug flow reactors, preferably one or more plug flow reactors.

[0121] It is explicitly noted that the above set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.

[0122] As known in the art, aminal refers to N,N-diphenylmethylenediamine or higher oligomers with N,N-diphenylmethylenediamine structure.

[0123] Aminobenzylaniline is abbreviated herein as ABA, ortho-aminobenzylaniline is also abbreviated herein as o-ABA or ortho-ABA, para-aminobenzylaniline is also abbreviated herein as p-ABA or para-ABA. Aminobenzylaniline refers to ortho-aminobenzylaniline, para-aminobenzylaniline and higher oligomers with ABA structure. Methylenedianiline, abbreviated as MDA, refers to individual methylenedianiline isomers, methylenedianiline isomer mixture and / or oligomers from methylenedianiline. For example, isomers of MDA are 4,4’-MDA, 2,4’-MDA and 2,2’-MDA.

[0124] In the context of the present invention, a term “X is one or more of A, B and C”, wherein X is a given feature and each of A, B and C stands for specific realization of said feature, is to be understood as disclosing that X is either 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 is noted that the skilled person is capable of transfer to above abstract term to a concrete example, e.g. where X is a chemical element and A, B and C are concrete elements such as Li, Na, and K, or X is a temperature and A, B and C are concrete temperatures such as 10 °C, 20 °C, and 30 °C. In this regard, it is further noted that the skilled person is capable of extending the above term to less specific realizations of said feature, e.g. “X is one or more of A and B” disclosing that X is either A, or B, or A and B, or to more specific realizations of said feature, e.g. “X is one or more of A, B, C and D”, disclosing that X is either 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.

[0125] The present invention is further illustrated by the following examples.

[0126] Examples

[0127] Reference Example 1 (Acidic condensation)

[0128] In a tempered stirred-tank reactor, 822 g of aniline are mixed with 171 g of a 32 wt.-% aqueous HCI at 50°C according to an acid to aniline molar ratio of 0.17:1. The mixture was stirred for 30 min and over 1 hour overall 208 g of a 49.-wt% formaldehyde solution was added keeping the reactor temperature at 50°C. After addition, the reactor was heated up to 100°C and the mixture was hold under these conditions for 90 minutes to get an acidic condensate.

[0129] This acidic condensate was fed to a second reactor, temperature was raised to 130°C and the mixture was held for another 120 minutes. Then the mixture was cooled down to 90°C,188 g of 5O.-wt% aqueous NaOH was added for neutralization and the mixture was stirred for another 30 min. The two-phase mixture was allowed to phase-separation and the lower aqueous phase was in most parts removed from reactor. The remaining organic phase was washed twice with 750 ml of water and then the washed organic phase was filled into a rotary evaporator for removal of water and most parts of the aniline. The remaining organic phase comprising MDA (about 605 g) was analyzed by GC. The isomer ratio of most desired monomer 4,4’-MDA to 2,4’-MDA was 7.1 :1. The content of the main side product N-Me-MDA was 1200 mg / kg. Example 1 (according to the present invention) :

[0130] Acidic condensate was prepared according to the procedure described in Reference Example 1 and fed to second reactor.

[0131] Separately, an ABA-containing mixture was prepared by mixing 1000 g aniline and 218 g 37 wt.-% formaldehyde solution (aniline to formaldehyde ratio A:F = 4:1) and stirred for 30 minutes at 80°C to get finally a two-phase reaction mixture. The upper aqueous phase was removed and organic phase comprising aminal and aniline was fed to a fixed bed (RU2) of a solid heterogeneous catalyst, namely iron on silica / alumina oxide support according to EP4072726A1 , at 60°C to convert aminal to ABA. Subsequently, aniline was removed by evaporation (about 350 g) to get 682 g of ABA-containing mixture with a ratio of aromatic rings to methyl bridges of 2.6: 1 . 600 g of the ABA-containing mixture were added to the second reactor filled with the acidic condensate and procedure described in Reference Example 1 was continued to get finally about 1026 g of MDA product. The 4,4’-MDA to 2,4’-MDA isomer ratio was 7.0:1 and the content of N- Me-MDA was 1100 mg / kg.

[0132] Without impairing MDA quality, thanks to the inventive process 421 g (about 70%) more MDA could be produced using same amount of HCI and NaOH. So the specific consumption of HCI and NaOH per MDA could be reduced by 41 % with the claimed process.

[0133] Reference example 2 (Aminal route according to EP0109931 and not the present invention) :

[0134] Acidic condensate was prepared according to the procedure described in reference example of EP0109931 from 800g aniline, 137 g 32 wt.-% aqueous HCI and 263 g 50 wt.-% formaldehyde (aniline to formaldehyde ratio A:F=2.0:1 , Acid to Aniline molar ratio of =0.14:1).

[0135] An aminal mixture was prepared by mixing 2000 g aniline and 436 g of a 37 wt.-% formaldehyde solution (aniline to formaldehyde ratio A:F =4) and stirring for 30 minutes at 80°C to get finally a two-phase reaction mixture. The upper aqueous phase was removed and the organic phase comprising aminal and aniline was fed to a rotary evaporator to remove water and aniline. 600 g of the aminal was mixed with the acidic condensate in second reactor at 75°C and mixture was heated-up to 130°C following the procedure described in Reference Example 1 (Neutralization with 106 g a 50 wt.-% NaOH solution). The final MDA product was analyzed by GC showing an isomer ratio of 6.5:1 and a N- Me- MDA content of 7500 mg / kg.

[0136] Example 2 (according to the present invention) :

[0137] Acidic condensate was prepared as described in Reference Example 2.

[0138] 600 g of a ABA-containing mixture was prepared according procedure describe in Example 1, but aniline was completely removed in evaporation step.

[0139] The ABA-containing mixture was mixed with the acidic condensate in second reactor at 75°C and procedure described in Reference Example 2 was continued. The isomer ratio of the final MDA was 7.8:1 and the content of N-Me-MDA was 3000 mg / kg.

[0140] Compared to Reference Example 2, the pre-conversion of aminal to ABA at a heterogeneous catalyst before admixing with acidic condensate leads much better product in respect to sidecomponents (N-Me-MDA) and content of the most desired isomer 4,4’-MDA.

[0141] Brief description of the figures

[0142] Figure 1 is a schematic representation of a production unit used for the process according to embodiments of the invention.

[0143] The production unit comprises a first reactor unit RU1, a separation unit Sil, a second reactor unit RU2, a means m(ML-S2) for bringing in contact S2 and ML and a third reactor unit RU3. The stream S01 comprising aniline and the aqueous stream S02 comprising formaldehyde are introduced into RU1 for forming aminal, obtaining a mixture M1 having an organic phase comprising aminal and aniline and an aqueous phase comprising water. M1 is passed through the (liquid-liquid) separation unit Sil, obtaining a stream S1 comprising the organic phase comprising aminal and aniline. S1 is introduced into RU2 (fixed-bed) which comprises an heterogeneous catalyst C, preferably Fe on silica-alumina, for a rearrangement, obtaining a stream S2 comprising aminobenzylaniline (ABA) and aniline. The stream S2 is brought in contact with ML via m(ML-S2), obtaining a stream S3 comprising S2 and ML. S3 is then passed through RU3 and subjected to rearrangement conditions in RU3, obtaining a stream S4 comprising meth- ylendianiline (MDA). Figure 2 is a schematic representation of a production unit used for the process according to preferred embodiments of the invention.

[0144] The production unit comprises a first reactor unit RU1 , a separation unit Sil, a second reactor unit RU2, a means m(ML-S2) for bringing in contact S2 and ML, a third reactor unit RU3, a unit UC for bringing in contact the stream S010 comprising aniline and an aqueous stream SA comprising a Bronsted acid and a reactor unit RUA. The stream S010 comprising aniline and the aqueous stream SA are introduced into UC for obtaining a mixture M10 comprising aniline, water and the Bronsted acid, such as HCI. M10 is introduced into RUA and brought in contact with an aqueous stream S020 comprising formaldehyde to obtain a mixture ML comprising the Bronsted acid and aminobenzylaniline. Further, the stream S01 comprising aniline and the aqueous stream S02 comprising formaldehyde are introduced into RU1 for forming aminal, obtaining a mixture M1 having an organic phase comprising aminal and aniline and an aqueous phase comprising water. M1 is passed through the (liquid-liquid) separation unit SU, obtaining a stream S1 comprising the organic phase comprising aminal and aniline. S1 is introduced into RU2 (fixed-bed) which comprises an heterogeneous catalyst C, preferably Fe on silica-alumina, for a rearrangement, obtaining a stream S2 comprising aminobenzylaniline (ABA) and aniline. The stream S2 is brought in contact with ML obtained from RUA and comprising ABA and the Bronsted acid, via m(ML-S2), obtaining a stream S3 comprising S2 and ML. S3 is then passed through RU3 and subjected to rearrangement conditions in RU3, obtaining a stream S4 comprising methylendianiline (MDA).

[0145] Cited literature

[0146] - WO 01 / 74755 A1

[0147] - WO 2010 / 072504 A 1

[0148] - WO 2021 / 116419 A1

[0149] - US2016068474 A1

[0150] - EP 2145874 A1

[0151] - EP 2000459 A1

[0152] - DE 10141620

[0153] - DE 19804915

[0154] EP 0109931 A2

Claims

Claims1 . A process for preparing methylenedianiline, the process comprising(i) preparing a stream S1 comprising aminal, (i) comprising(1.1) providing a stream S01 comprising aniline;(1.2) providing an aqueous stream S02 comprising formaldehyde;(1.3) bringing in contact at least a portion of S01 provided according to (i.1) with at least a portion of S02 provided according to (i.2) in a first reactor unit RU1 , obtaining a mixture M1 having an organic phase comprising aminal and aniline, and having an aqueous phase comprising water;(1.4) passing M1 obtained according to (i.3) through a separation unit Sil for separating the phases of M1 , obtaining a stream S1 comprising the organic phase comprising aminal and aniline, and a stream S11 comprising the aqueous phase comprising water;(ii) passing the stream S1 prepared according (i) in a second reactor unit RU2, RU2 comprising an heterogeneous catalyst C, and bringing in contact S1 with C in RU2, obtaining a stream S2 comprising aminobenzylaniline;(iii) bringing in contact S2 obtained according to (ii) with a liquid mixture ML comprising a Bronsted acid, obtaining a stream S3 comprising S2 and ML;(iv) passing S3 obtained according to (iii) into a third reactor unit RU3 and subjecting S3 to rearrangement conditions in RU3, obtaining a stream S4 comprising methylenedianiline.

2. The process of claim 1 , wherein from 20 to 70 weight-%, preferably from 25 to 60 weight- %, more preferably from 30 to 50 weight-%, of S02 consist of formaldehyde.

3. The process of claim 1 or 2, wherein, according to (i.3), bringing in contact S01 provided according to (i.1) with S02 provided according to (i.2) in a first reactor unit RU1 is performed at a temperature in the range of from 20 to 100 °C, preferably in the range of from 30 to 95 °C, more preferably in the range of from 40 to 90 °C; wherein preferably, according to (i.3), bringing in contact S01 provided according to (i.1) with S02 provided according to (i.2) in a first reactor unit RU1 is performed at a pressure in the range of from 0.5 to 10 bar(abs), more preferably in the range of from 0.6 to 5 bar(abs), more preferably in the range of from 0.7 to 2 bar(abs).

4. The process of any one of claims 1 to 3, wherein the molar ratio of aniline to formaldehyde in RU1 is in the range of from 1.5:1 to 10:1 , preferably in the range of from 1.8:1 to 6:1 , more preferably in the range of from 2:1 to 4:1 .

5. The process of any one of claims 1 to 4, wherein the second reactor unit RU2 comprises one or more fixed-bed reactors.

6. The process of any one of claims 1 to 5, wherein bringing in contact S1 with C in RU2 according to (ii) is performed at a temperature in the range of from 15 to 200°C, preferably in the range of from 20 to 180°C, more preferably in the range of from 30 to 160°C.

7. The process of any one of claims 1 to 6, wherein the Bronsted acid comprised in ML is one or more of hydrochloric acid, sulfuric acid and phosphoric acid, preferably hydrochloric acid.

8. The process of any one of claims 1 to 7, wherein the liquid mixture ML further comprises aminobenzylaniline.

9. The process of claim 8, further comprising preparing the liquid mixture ML comprising a Bronsted acid, preferably HCI, and aminobenzylaniline, comprising bringing in contact aniline, preferably a portion of S01 provided in (i.1 ), with an aqueous solution of the Bronsted acid, obtaining a liquid mixture M10 comprising aniline, water and the Bronsted acid; introducing M10 into a reactor unit RUA together with formaldehyde, preferably a portion of S02 provided in (i.2); reacting M10 with the formaldehyde in RUA, obtaining the liquid mixture ML comprising aminobenzylaniline and the Bronsted acid.

10. The process of claim 9, wherein, prior to be introduced into RUA, the process further comprises heating M 10 to a temperature in the range of from 20 to 95 °C, more preferably in the range of from 30 to 90 °C.11 . The process of claim 9 or 10, wherein the molar ratio of aniline to formaldehyde in RUA is in the range of from 1.5:1 to 4.5:1 , preferably in the range of from 1.6:1 to 4:1 , more preferably in the range of from 1.7:1 to 3:1.

12. The process of any one of claims 9 to 11 , wherein reacting M10 and the formaldehyde in RUA is performed at a temperature in the range of from 30 to 90 °C, preferably in the range of from 40 to 70 °C;wherein preferably reacting M10 and the formaldehyde in RUA is performed at a pressure in the range of from 0.1 to 10 bar(abs), more preferably in the range of from 0.5 to 2 bar(abs).

13. The process of any one of claims 9 to 12, wherein, in S3, the ratio of the mass of aminobenzylaniline (ABA) comprised in S2 relative to the mass of aminobenzylaniline (ABA) comprised ML is in the range of from 10:1 to 1 :10, preferably in the range of from 1 :1 to 1 :6, more preferably in the range of from 1 :2 to 1 :4.

14. The process of any one of claims 1 to 13, wherein subjecting S3 to rearrangement conditions in RU3 comprising subjecting S3 to a temperature in the range of from 80 to 200 °C, preferably in the range of from 100 to 160°C, more preferably in the range of from 120 to 140°C; wherein preferably subjecting S3 to rearrangement conditions in RU3 comprising subjecting S3 to a pressure in the range of from 0.5 to 10 bar(abs), more preferably in the range of from 0.8 to 5 bar(abs), more preferably in the range of from 1 to 3 bar(abs).

15. A production unit for carrying out a process for preparing methylenedianiline, preferably the process for preparing methylenedianiline according to any one of claims 1 to 14, the unit comprising a first reactor unit RU1 ; a means for introducing at least a portion of stream S01 into RU1 ; a means for introducing at least a portion of aqueous stream S02 into RU1 ; a means for removing mixture M1 from RU1 ; a separation unit SU; a second reactor unit RU2 comprising a heterogeneous catalyst C; a means for introducing stream S1 into RU2; a means for bringing in contact stream S2 with liquid mixture ML; a reaction unit RU3; a means for introducing stream S3 into RU3; a means for removing stream S4 from RU3.

Images