METHOD FOR PRODUCING CIS- AND TRANS-ENRICHED MDACH

Abstract

A process for preparing trans-enriched MDACH, including: distilling an MDACH starting mixture in the presence of an auxiliary, which is an organic compound having a molar mass of 62 to 500 g/mol, a boiling point at least 5° C. above the boiling point of cis,cis-2,6-diamino-1-methylcyclohexane, and 2 to 4 functional groups, each of which is independently an alcohol group or a primary, secondary or tertiary amino group. The MDACH starting mixture includes 0 to 100% by weight of 2,4-MDACH and 0 to 100% by weight of 2,6-MDACH, based on the total amount of MDACH present in the MDACH starting mixture. The MDACH starting mixture includes both trans and cis isomers. Trans-enriched MDACH includes 0 to 100% by weight of 2,4-MDACH and 0 to 100% by weight of 2,6-MDACH, where the proportion of trans isomers in the mixture is higher than the proportion of trans isomers in the MDACH starting mixture.

Claims

1. A process for preparing trans-enriched MDACH, comprising: distilling an MDACH starting mixture in the presence of an auxiliary, wherein trans-enriched MDACH is distilled off, and wherein the auxiliary is an organic compound having a molar mass of 62 to 500 g/mol, a boiling point at least 5° C. above the boiling point of cis,cis-2,6-diamino-1-methylcyclohexane, where the boiling points are each based on a pressure of 50 mbar, and 2 to 4 functional groups, each of which is independently an alcohol group or a primary, secondary or tertiary amino group, wherein the MDACH starting mixture comprises 0% to 100% by weight of 2,4-diamino-1-methylcyclohexane (2,4-MDACH) and 0% to 100% by weight of 2,6-diamino-1-methylcyclohexane (2,6-MDACH), based on the total amount of MDACH (2,4-and 2,6-MDACH) present in the MDACH starting mixture, and wherein the MDACH starting mixture comprises both trans and cis isomers, and wherein trans-enriched MDACH is a mixture comprising 0% to 100% by weight of 2,4-MDACH and 0% to 100% by weight of 2,6-MDACH, based on the total amount of MDACH present in the mixture, where the proportion of trans isomers in the mixture, based on the total amount of MDACH present in the mixture, is higher than the proportion of trans isomers in the MDACH starting mixture, based on the amount of MDACH present in the MDACH starting mixture.

2. A process for preparing cis- and trans-enriched MDACH, comprising: I. preparing trans-enriched MDACH by the process according to claim 1; and II. distilling the bottom product obtained in preparing I, with distillative removal of cis-enriched MDACH, wherein cis-enriched MDACH is a mixture comprising 0% to 100% by weight of 2,4-MDACH and 0% to 100% by weight of 2,6-MDACH, based on the total amount of MDACH present in the mixture, where the proportion of cis isomers in the mixture, based on the total amount of MDACH present in the mixture, is higher than the proportion of cis isomers in the MDACH starting mixture, based on the amount of MDACH present in the MDACH starting mixture.

3. The process according to claim 1, which is performed continuously and comprises: feeding the auxiliary into a column, feeding the MDACH starting mixture into the column, and distilling trans-enriched MDACH out of the column.

4. The process according to claim 2, which is performed continuously, wherein: the preparing I comprises: feeding the auxiliary into a column, feeding the MDACH starting mixture into the column, and distilling trans-enriched MDACH out of the column, and the distilling II comprises: feeding the bottom product from the column into a second column, and distilling cis-enriched MDACH out of the second column.

5. The process according to claim 4, further comprising: III. recycling the bottom product from the second column into the column.

6. The process according to claim 3, wherein the auxiliary is fed in above the feed of the MDACH starting mixture.

7. The process according to claim 1, wherein the distillation of the MDACH starting mixture in the presence of the auxiliary is conducted at a top temperature of 80 to 180° C. and a top pressure of 10 to 500 mbar.

8. The process according to claim 1, wherein the auxiliary has either 2 to 4 alcohol groups, a primary, secondary or tertiary amino group and 1 to 3 alcohol group(s), or 2 to 4 functional groups, each of which is independently a primary, secondary or tertiary amino group.

9. The process according to claim 1, wherein the auxiliary, aside from the functional groups, has no further heteroatoms or 1 to 3 ether group(s) and otherwise, aside from the functional groups, has no further heteroatoms.

10. The process according to claim 1, wherein the auxiliary has a molar mass of from 76 to 300 g/mol.

11. The process according to claim 1, wherein the auxiliary has a molar mass of 62 to 250 g/mol, a melting point of less than 60° C. at a pressure of 1 bar, and 2 to 4 alcohol groups, where the auxiliary, aside from the alcohol groups, has no further heteroatoms or one or two ether groups and otherwise, aside from the alcohol groups, has no further heteroatoms

12. The process according to claim 1, wherein the auxiliary has a molar mass of 75 to 300 g/mol a melting point of less than 60° C. at a pressure of 1. bar, and a primary, secondary or tertiary amino group and 1 to 3 alcohol group(s), where the auxiliary, aside from the functional groups, has no further heteroatoms or one ether group and otherwise, aside from the functional groups, has no further heteroatoms.

13. The process according to claim 1, wherein the auxiliary has a molar mass of 100 to 300 g/mol a melting point of less than 60° C. at a pressure of 1 bar, and 2 to 4 functional groups, which are each independently a primary, secondary or tertiary amino group, where the auxiliary, aside from the functional groups, has no further heteroatoms.

14. The process according to claim 1, wherein the auxiliary is at least one selected from the group consisting of: 2-methylpropane-1,3-diol, hexane-1,2-diol, cis-cyclopentane-1,2-diol, trans-cyclopentane-1,2-diol, propane-1,3-diol, pentane-1,5-diol, 2-methylpropane-1,3-diol, hexane-1,3-diol, hexane-2,4-diol, cyclobutane-1,3-diol, cyclopentane-1,3-diol, cyclohexane-1,3-diol, cis- and trans-butene-1,4-diol, butane-1,4-diol, 2,3-dimethylbutane-1,4-diol, 2,2-dimethylbutane-1,4-diol, pentane-1,4-diol, 2,3-dimethylpentane-1,5-diol, hexane-1,4-diol, hexane-1,3,6-triol, hexane-1,2,6-triol, diglycerol, diethylene glycol, triethylene glycol, dipropylene glycol, diethanolamine, N-methyldiethanolamine, N-propyldiethanolamine, N-butyldiethanolamine, triethanolamine, N-ethylpropanolamine, N-propylethanolamine, N,N-dipropylethanolamine, N,N-dibutylethanolamine, dipropanolamine, N-methyldipropanolamine, N-propyldipropanolamine, N-butyldipropanolamine, tripropanolamine, diisopropanolamine, N-methyldiisopropanolamine, triisopropanolamine, N-2-methylaminopropanol, 4-(2-hydroxyethyl)morpholine, pentanolamine, hydroxyethylpiperazine, N-(2-hydroxyethyl)aniline, N,N-di(2-hydroxyethyl)aniline, 3-(cyclohexylamino) propylamine, dipropylenetriamine, triethylenetetramine, 3-(2-aminoethylamino) propylamine, and isophoronediamine.

15. The process according to claim 1, wherein the auxiliary is at least one selected from the group consisting of: glycerol, propane-1,3-diol, butane-1,4-diol, cis-butene-1,4-diol, triethylene glycol, diglycerol, 3-(cyclohexylamino)propylamine, 4-(2-hydroxyethyl)morpholine, N-(2-hydroxyethyl) aniline, triethanolamine, and N-methyldiethanolamine.

16. The process according to claim 1, wherein the MDACH starting mixture comprises more than 95% by weight of MDACH.

17. The process according to claims 1, wherein the MDACH starting mixture comprises 5% to 95% by weight of 2,4-MDACH and 5% to 95% by weight of 2,6-MDACH, based on the total amount of MDACH present in the MDACH starting mixture,

18. The process according to claim 1, wherein the MDACH starting mixture comprises 5% to 60% by weight of trans isomers and 40% to 95% by weight of cis isomers, based on the total amount of MDACH present in the MDACH starting mixture.

19. The process according to claim 1, wherein the trans-enriched MDACH comprises 55% to 100% by weight of trans isomers, based on the total amount of MDACH present in the mixture.

20. The process according to claim 1, wherein the trans-enriched MDACH comprises more than 95% by weight of MDACH.

21. The process according to claim 1, wherein the trans-enriched MDACH comprises 5% to 95% by weight of 2,4-MDACH and 5% to 95% by weight of 2,6-MDACH, based on the total amount of MDACH present in the mixture.

22. The process according to claim 2, wherein the cis-enriched MDACH comprises 55% to 100% by weight of cis isomers, based on the total amount of MDACH present in the mixture.

23. The process according to claim 2, wherein the cis-enriched MDACH comprises more than 95% by weight of MDACH.

24. The process according to claim 2, wherein the cis-enriched MDACH comprises 5% to 95% by weight of 2,4-MDACH and 5% to 95% by weight of 2,6-MDACH, based on the total amount of MDACH present in the mixture.

25. Trans-enriched MDACH, comprising: 0% to 100% by weight of 2,4-MDACH; and 0% to 100% by weight of 2,6-MDACH, based on the total amount of MDACH present in the mixture, wherein a proportion of trans isomers present in the mixture is from 62% to 85% by weight, based on the total amount of MDACH present in the mixture.

26. Cis-enriched MDACH, comprising; 0% to 100% by weight of 2,4-MDACH; and 0% to 100% by weight of 2,6-MDACH, based on the total amount of MDACH present in the mixture, wherein a proportion of cis isomers present in the mixture is from 70% to 95% by weight, based on the total amount of MDACH present in the mixture.

Description

EXAMPLES

[0224] Unless stated otherwise, in all the examples, Baxxodur ECX210 was used as MDACH starting mixture.

[0225] Composition of Baxxodur ECX 210:

[0226] trans isomer: 36% to 38% by weight

[0227] 2,4 MDACH: 80% to 90% by weight

[0228] 2,6-MDACH: 10% to 20% by weight

[0229] The figures given are each based on the total amount of MDACH present in the MDACH starting mixture.

[0230] The MDACH starting mixture consisted to an extent of ≧98% by weight of MDACH.

Example 1

[0231] Batch distillation with auxiliary (in accordance with the invention) and without auxiliary (not in accordance with the invention)

[0232] A 1.6 liter Miniplant reactor provided with an anchor stirrer and thermostat was initially charged with 800 g of Baxxodur ECX210 (MDACH starting mixture) and the particular auxiliary with exclusion of air, with a molar ratio of the auxiliary and the molar amount of all the isomers of 2,4-diamino-1-methylcyclohexane and 2,6-diamino-1-methylcyclohexane of 1. The distillation as effected with the aid of a column (Sulzer DX packing, N.sub.th =30-45) with a reflux divider at top pressure about 20 mbar and a reflux ratio of 1, During the distillation, a fraction of 100 mL was removed and then analyzed by means of GC.

TABLE-US-00001 TABLE 1 Proportion of trans isomers as a function of the auxiliary used. All figures are in % by weight and relate to the total amount of MDACH present in the MDACH starting mixture or in the fraction. Auxiliary Fraction No auxiliary 44.15 Glycerol 46.03 Propane-1,3-diol 49.29 Triethanolamine 46.01 Triethylene glycol 45.39 Diglycerol 45.03 Butane-1,4-diol 46.20 N-(2-Hydroxy-ethyl)aniline 45.82 cis Butene-1,4-diol 47.22 Pentane-1,5-diol 47.09 N-Methyldiethanol-amine 46.07 4-(2-Hydroxyethyl)-morpholine 46.86

[0233] The results show that the use of an auxiliary leads to an improvement in the separation efficiency with respect to the trans isomers. Propane-1,3-diol has the highest separation efficiency.

Example 2

[0234] Batch distillation with sulfolane as auxiliary (not in accordance with the invention)

[0235] The MDACH starting mixture used was Baxxodur ECX 210 and the auxiliary sulfolane. The experimental setup and experimental procedure correspond to those from example 1, with the difference that the top pressure during the distillation was about 50 mbar During the distillation, a fraction of 100 mL was removed and then analyzed by means of GC.

TABLE-US-00002 TABLE 2 Proportion of trans isomers as a function of the use of the sulfolane auxiliary. All figures are in % by weight and are based on the total amount of MDACH present in the MDACH starting mixture or in the fraction. Auxiliary Fraction Without sulfolane 46.61 With sulfolane 45.90

[0236] The results show that an addition of sulfolane as auxiliary does not achieve any significant improvement in the distillation yield of trans isomers, but a deterioration compared to the distillation without sulfolane occurs.

Example 3

[0237] Batch distillation with propane-1,3-diol with different composition of the MDACH starting mixture (in accordance with the invention)

[0238] The distillation was effected with the aid of a column (Sulzer DX packing+Moritz A3-1000, N.sub.th about 60) at a top pressure of 50 mbar. The total amount of MDACH starting mixture and propane-1,3-diol used was about 1000-1200 g, with use in experiment a) of Baxxodur ECX 210 and in experiment b) of a mixture having a proportion of about 44% by weight of trans isomers. The molar ratio of the propane-1,3-diol (auxiliary) and MDACH was 1, The reflux ratio was set to 2. For the rest, the experimental setup and experimental procedure corresponded to those from example 1. During the distillation, a fraction of 100 mL was removed and then analyzed by means of GC.

TABLE-US-00003 TABLE 3 Proportion of trans isomers as a function of the proportion of trans isomers in the MDACH starting mixture. All figures are in % by weight and relate to the total amount of MDACH present in the MDACH starting mixture or in the fraction. Experiment Fraction a) 52.66 b) 68.91

Example 4

[0239] Continuous distillation with propane-1,3-diol as auxiliary (in accordance with the invention)

[0240] The columns used (Sulzer CY packing, about N.sub.th =45) have each been equipped with a thin-film evaporator and a separate condenser. The feeds to and draws from the column are shown in schematic form in FIG. 1 for example 4.1 and FIG. 2 for example 4.2. The auxiliary used was propane-1,3-diol and the MDACH starting mixture Baxxodur ECX 210.

Example 4.1

[0241] Propane-1,3-diol was fed in in the rectifying section of the column at a pressure of about 50 mbar. The MDACH starting mixture was fed in in the stripping section of the column at a pressure of about 53 mbar. The feeds were boiling liquids.

[0242] Variant 1:

[0243] Feedrates:

[0244] MDACH starting mixture=1540 g/h,

[0245] Propane-1,3-diol=920 g/h

[0246] Draws:

[0247] Distillate=300 g/h

[0248] Reflux: 2000 g/h

[0249] Results (variant 1):

[0250] The trans-enriched MDACH obtained as distillate had the following composition:

[0251] trans isomer: about 66% by weight

[0252] 2,4-MDACH: about 68% to 69% by weight

[0253] 2,6-MDACH: about 31% to 32% by weight

[0254] The figures are each based on the total amount of MDACH present in the distillate.

[0255] MCHA was present in the distillate to an extent of about 1 GC area % (GC area percent). The propane-1,3-diol was present almost entirely in the bottoms.

[0256] Variant 2:

[0257] Feed rates:

[0258] MDACH starting mixture=1540 g/h,

[0259] Propane-1,3-diol=1250 g/h

[0260] Draws:

[0261] Distillate=300 g/h

[0262] Reflux: 1700 to 1800 g/h

[0263] Results (variant 2):

[0264] The trans-enriched MDACH obtained as distillate had the following composition:

[0265] trans isomer: about 74% by weight

[0266] 2,4-MDACH: about 64% by weight

[0267] 2,6-MDACH: about 36% by weight

[0268] The figures are each based on the total amount of MDACH present in the distillate.

[0269] MCHA was present in the distillate to an extent of about 1 GC area %, The proportion of propane-1,3-diol in the distillate was about 13.8% by weight, based on the total amount of the distillate.

Example 4.2

[0270] Feeds to and draws from the columns are shown schematically in FIG. 2.

[0271] The first distillation step (DISTILLATION 1) corresponds to variant 2 for example 4.1. The feed composition for DISTILLATION 2 thus corresponds to the composition of the distillate obtained in variant 2 of example 4.1.

[0272] The figures which follow in relation to variants 1 and 2 relate to the second distillation step (DISTILLATION 2).

[0273] Variant 1

[0274] Feed rate: 1000 g/h

[0275] Draws:

[0276] Sidestream=590 g/h,

[0277] Distillate (in the top condenser)=0 g/h,

[0278] Postcondenser=about 10 to 30 g/h

[0279] Reflux (column)=2000 g/h

[0280] Temperatures:

[0281] Top condenser=85° C.,

[0282] Postcondenser=about 15° C.

[0283] Results (variant 1):

[0284] The trans-enriched MDACH obtained in the sidestream had the following composition:

[0285] trans isomer: about 74% by weight

[0286] 2,4-MDACH: about 60% by weight

[0287] 2,6-MDACH: about 40% by weight

[0288] The figures are each based on the total amount of MDACH present in the sidestream.

[0289] The propane-3-diol was present almost entirely in the bottoms. The MCHA content in the sidestream was reduced by the postcondenser at the top of the column from about 1 GC area % in the feed composition to about 0.61-0.66 GC area %.

[0290] Variant 2:

[0291] Feed rate: 1000 g/h

[0292] Draws

[0293] Sidestream=490 g/h,

[0294] Distillate (in top condenser)=100 g/h,

[0295] Postcondenser=about 10-30 g/h

[0296] Reflux (column)=2000 g/h

[0297] Temperatures:

[0298] Top condenser=90° C.,

[0299] Postcondenser=about 15° C.

[0300] Results (variant 2):

[0301] The trans-enriched MDACH present in the sidestream had the following composition:

[0302] trans isomer; about 74% by weight

[0303] 2,4-MDACH: about 60% by weight

[0304] 2,6-MDACH: about 40% by weight

[0305] The figures are each based on the total amount of MDACH present in the sidestream

[0306] The propane-1,3-diol was present almost entirely in the bottoms, The MCHA content in the sidestream was reduced by the postcondenser at the top of the column and the distillate draw in the top condenser from about 1% in the feed composition to about 0.57 GC area %.

[0307] Preparation of cis-enriched MDACH and recovery of the auxiliary (in accordance with the invention):

[0308] The bottom product from example 4.1 variant 1, was initially charged in a distillation still equipped with a column (Sulzer DX packing+Moritz A3-1000, N.sub.th =about 60) and distilled at a top pressure of about 250 mbar with exclusion of air. This gave a bottom product which consisted to an extent of about 65% by weight of propane-1,3-diol. This can be used again in the distillation of the MDACH starting mixture. The distillate obtained was a mixture which had the following composition:

[0309] cis isomer: about 83% by weight

[0310] 2,4-MDACH: about 92% by weight

[0311] 2,6-MDACH: about 8% by weight

[0312] The figures are each based on the total amount of MDACH present in the distillate.