Process for hydrogenating toluenediamine (TDA) tar

Abstract

Process for hydrogenating toluenediamine (TDA) tar containing TDA and high boilers relative to TDA, including the step of contacting the toluenediamine tar with a heterogeneous hydrogenation catalyst comprising at least one metal selected from the group consisting of Ni, Co, Ru, Pd, Pt on at least one catalyst support selected from the group consisting of carbon, TiO.sub.2 and ZrO.sub.2, and with hydrogen under hydrogenating conditions.

Claims

1. A process for hydrogenating a toluenediamine (TDA) tar containing TDA and high boilers relative to TDA, the process comprising: contacting the toluenediamine tar with a heterogeneous hydrogenation catalyst comprising at least one metal selected from the group consisting of Ni, Co, Ru, Pd, Pt on at least one catalyst support selected from the group consisting of carbon, TiO.sub.2 and ZrO.sub.2, and with hydrogen under hydrogenating conditions, wherein the toluenediamine tar contains 5 to 35 wt % of toluenediamine isomers.

2. The process according to claim 1, wherein the catalyst comprises Ni, Ni and Pt, Ru, Pd, or Pt on a ZrO.sub.2 or an active carbon catalyst support.

3. The process according to claim 1, wherein an amount of Ru, Pd, Pt or mixtures thereof, based on the heterogeneous hydrogenation catalyst, is 1 to 7 wt %.

4. The process according to claim 1, wherein an amount of Ni, Co or mixture thereof, based on the heterogeneous hydrogenation catalyst, is 0.5 to 70 wt %.

5. The process according to claim 1, wherein the heterogeneous hydrogenation catalyst is Ni/ZrO.sub.2, Ru/ZrO.sub.2, Pd/C, Pt/C or Pt/Ni/C.

6. The process according to claim 1, which is carried out in suspension or in a fixed bed.

7. The process according to claim 1, which is carried out as a continuous operation or batchwise.

8. The process according to claim 1, which is carried out at a temperature of from 120 to 270 C.

9. The process according to claim 1, which is carried out at a hydrogen pressure of from 60 to 300 bar.

10. The process according to claim 1, wherein the zirconium oxide support material is present in monoclinic, tetragonal, cubic or amorphous phase or in a mixed phase of these modifications.

11. The process according to claim 1, wherein the zirconium oxide support material has a BET surface area of from 30 to 300 m.sup.2/g a pore volume of from 0.1 to 1 cm.sup.3/g and a tamped density of from 500 to 2000 kg/m.sup.3.

12. The process according to claim 1, wherein upon hydrogenation, part of the high boilers are transformed into mid-boilers or low boilers having a lower boiling point than the high boilers.

13. The process according to claim 1, wherein part of the toluenediamine (TDA) tar containing TDA and high boilers relative to TDA are converted into methylcyclohexylamine (MCA) and/or methylcyclohexyldiamine (MCDA).

14. The process according to claim 1, wherein the toluenediamine tar is diluted with an organic solvent or diluent inert to the hydrogenation before performing the hydrogenation.

Description

EXAMPLES

(1) General Procedure:

(2) All experiments were performed in a lab autoclave in batch mode. The 100 ml autoclave was filled with catalyst (typically 2 g) and 50 g 7 wt % solution of TDA tar in 1,4-dioxane. After this it was pressurized with nitrogen for leak-test and depressurized. To purge out nitrogen a pressurization with hydrogen followed with depressurization was applied. Then the autoclave was heated to reaction temperature (typically 170 C.) stirring with 1000 rpm. At reaction temperature the system was pressurized with hydrogen to the reaction pressure (typically 150 bar) which is regarded as the starting time. Liquid is sampled manually typically after 3, 5 and 24 h after pressurization with hydrogen and the samples are analyzed by GC.

Example 1

(3) Apart from 3% Pt-1% Ni/C (1 g) always 2 g of catalysts were employed. To enable handling of the Rh-carbon catalyst which is pyrophoric the catalyst was pre-immersed in 10 g diethyleneglycol and 40 g of the tar-solution was employed to avoid overfilling of the autoclave.

(4) TABLE-US-00001 TABLE 1 Conversion of high boilers resp. TDA and corresponding product composition after 3 h relative product composition other X(HB) X(TDA) HB TDA MCDA MCA Toluidine LB MB [%] [%] [%] [%] [%] [%] [%] [%] [%] 60% Ni/ZrO.sub.2 22% 18% 50% 26% 1% 2% 0% 12% 9% 3 h@170 C. CuZnAlO.sub.3 6% 4% 66% 26% 0% 3% 0% 1% 4% 3 h@170 C. CuMn/Al.sub.2O.sub.3 7% 10% 65% 28% 0% 0% 0% 1% 5% 3 h@170 C. 5% Ru/ZrO.sub.2 15% 51% 59% 12% 14% 4% 0% 1% 8% 3 h@170 C. 5% Pd/C 57% 65% 30% 9% 1% 15% 4% 14% 26% 3 h@170 C. 3% Pd/C 49% 63% 36% 10% 2% 11% 4% 10% 27% 3 h@170 C. 3% Rh/C 2% 63% 61% 10% 3% 2% 1% 7% 11% 3 h@170 C. 3% Pt/C 14% 9% 60% 28% 0% 0% 0% 1% 8% 3 h@170 C. 3% Pt1% Ni/C 10% 6% 57% 33% 0% 0% 0% 1% 8% 3 h@170 C.

(5) Results after 3 h are given in Table 1. Summarizing the catalyst testing program it can be stated:

(6) Base Metal Catalysts

(7) TABLE-US-00002 Ni catalysts (60% Ni/ZrO.sub.2) moderately active Cu catalysts inactive
Precious Metal Catalysts

(8) TABLE-US-00003 5% Ru/ZrO.sub.2 (BASF) moderately active/MCDA as product 3% Pd/C (Aldrich) & (BASF 5% Pd/C) very active/MCA as product 3% Rh/C (Aldrich) inactive 3% Pt/C (Aldrich) & (3% Pt-1% Ni/C) moderately active but only to mid-boilers

Example 2

(9) Ni Catalyst:

(10) Test results for a nickel-zirconia catalyst are given in Table 2. After 3 h the temperature was elevated to 190 C. resulting in strong increase in MCA yield. After 24 h more than 70% of the high boilers are converted and TDA is only partially converted. The main fraction is composed of the mid-boilers (35% yield) but MCA yield is considerably high with 24%.

(11) TABLE-US-00004 TABLE 2 relative product composition other X(HB) X(TDA) HB TDA MCDA MCA Toluidine LB MB [%] [%] [%] [%] [%] [%] [%] [%] [%] 60% Ni/ZrO.sub.2 22% 18% 50% 26% 1% 2% 0% 12% 9% 3 h@170 C. 60% Ni/ZrO.sub.2 + 31% 28% 44% 23% 2% 6% 0% 11% 15% 2 h@190 C. 60% Ni/ZrO.sub.2 + 72% 52% 18% 15% 2% 24% 1% 6% 35% 19 h@190 C.

Example 3

(12) Pd Catalyst:

(13) Test results for catalyst (5% Pd/carbon) are given in Table 3. After 24 h almost 90% of the high boilers are converted and TDA is fully converted. The main fraction is composed of the mid-boilers (46% yield).

(14) The MCA-yield is considerably high with 23%. The distribution between 2-methylcyclohexylamine and 4-methylcyclohexylamine is around 1:1. The relative share of cis/trans-isomers of the two regio-isomers lies between 1:1 and 1:3 however the assignment to cis or trans is not established. Furthermore the base-line separation of the first peaks of both region-isomers i.e. 2MCA_a and 4MCA_a is not given so that the twin-peak was arbitrarily split at the minimum.

(15) TABLE-US-00005 TABLE 3 Conversion of high boilers resp. TDA and corresponding product composition after 3, 5 and 24 h relative product composition other X(HB) X(TDA) HB TDA MCDA MCA Toluidine LB MB [%] [%] [%] [%] [%] [%] [%] [%] [%] 5% PdC 57% 65% 30% 9% 1% 15% 4% 14% 26% 3 h@170 C. 5% PdC + 76% 92% 17% 2% 2% 22% 5% 16% 37% 2 h@170 C. 5% PdC + 89% 99% 8% 0% 3% 23% 5% 16% 46% 19 h@170 C.

Example 4

(16) Ru Catalyst:

(17) Test results for 5% Ru/ZrO.sub.2 are given in Table 4. After 24 h at 190 C. almost 70% of the high boilers are converted and TDA is fully converted. The main product fractions are MCA-isomers, MCDA-isomers and mid-boilers. To known value products MCA and MCDA the yield is 47%. At 170 C. the conversion of high boilers is considerably low and mostly TDA is converted to MCDA.

(18) TABLE-US-00006 TABLE 4 Conversion of high boilers resp. TDA and corresponding product composition at various times for two temperatures relative product composition other X(HB) X(TDA) HB TDA MCDA MCA Toluidine LB MB [%] [%] [%] [%] [%] [%] [%] [%] [%] 5% Ru/ZrO.sub.2 15% 51% 59% 12% 14% 4% 0% 1% 8% 3 h@170 C. 5% Ru/ZrO.sub.2 + 18% 65% 58% 9% 17% 5% 0% 2% 9% 2 h@170 C. 5% Ru/ZrO.sub.2 27% 77% 51% 6% 20% 9% 1% 3% 10% 3 h@190 C. 5% Ru/ZrO.sub.2 + 32% 81% 48% 5% 21% 10% 0% 4% 12% 2 h@190 C. 5% Ru/ZrO.sub.2 + 69% 95% 22% 1% 26% 21% 0% 8% 21% 19 h@190 C.