COUPLING OF DISTILLATIVE PURIFICATION WITH A PARTIAL CONDENSER FOR PRE-PURIFICATION OF ISOPHORONEDIAMINE

Abstract

A process for fine purification of isophoronediamine (IPDA), including producing IPDA by aminating hydrogenation of isophorone nitrile in the presence of at least ammonia, hydrogen, a a hydrogenation catalyst and optionally further additions to obtain a crude IPDA, and subjecting the crude IPDA to a fine purification via two vacuum distillation columns, wherein in the first vacuum distillation column the removal of any remaining relatively low-boiling byproducts is effected and in the second vacuum distillation column the IPDA is obtained in pure form as tops and thus separated from the organic residues, and wherein the first vacuum distillation column has vacuum distillation column has a partial condenser fitted to it.

Claims

1. A process for fine purification of isophoronediamine (IPDA), pure isophoronediamine, comprising the steps of: (a) producing isophoronediamine by aminating hydrogenation of isophorone nitrile in the presence of at least ammonia, hydrogen, a hydrogenation catalyst and optionally further additions and in the presence or absence of organic solvents to obtain a crude isophoronediamine; and (b) subjecting the crude isophoronediamine to a fine purification via two vacuum distillation columns, wherein in the first vacuum distillation column the removal of any remaining relatively low-boiling byproducts is effected and in the second vacuum distillation column the isophoronediamine is obtained in pure form as tops and thus separated from the organic residues, and wherein the first vacuum distillation column has a partial condenser fitted to it.

2. The process according to claim 1, wherein the crude isophoronediamine generally comprises the following composition in weight % (wt %) based on the weight of the crude isophoronediamine : TABLE-US-00010 IPDA 75-100 wt %; Water  0-15 wt %; Low boilers 0-6 wt %; and High boilers   0-6 wt %.

3. The process according to claim 1, wherein the partial condenser is installed at the top of the first vacuum distillation column and is attached inside the column or outside the column.

4. The process according to claim 1, wherein the vapor stream in the first vacuum distillation column is pre-cooled and consequently partly condensed in the partial condenser and the condensed liquid is used as return stream in the vacuum distillation column.

5. The process according to claim 1, wherein the uncondensed vapor stream in the first vacuum distillation column is fully condensed and divided into an organic phase and an aqueous phase in a second condenser, wherein the organic phase is partly used as reflux for the first vacuum distillation column.

6. The process according to claim 1, wherein IPDA leaves the first vacuum distillation column as bottoms stream and is sent to a second vacuum distillation column for removal of the high boilers.

7. The process according to claim 1, wherein the pure IPDA is obtained at the top of the second vacuum distillation column.

8. The process according to claim 1, wherein the partial condenser is operated under the following conditions: TABLE-US-00011 Temperature 40-120° C.; and Pressure 10-200 mbar.

9. The process according to claim 1, wherein the employed first vacuum distillation column comprises the following parameters: TABLE-US-00012 Pressure 10-200 mbar; Bottoms temperature 80-200° C.; and Theoretical plates 10-80.

10. The process according to claim 1, wherein the composition of the feed stream from the first vacuum distillation column into the second vacuum distillation column (crude IPDA II) comprises the following composition (wt %) based on the weight of the crude isophoronediamine: TABLE-US-00013 IPDA 90-100 wt %; and High boilers 0-10 wt %.

11. The process according to claim 1, wherein the employed second vacuum distillation column comprises the following parameters: TABLE-US-00014 Pressure 10-200 mbar; Tops temperature 80-200° C.; and Theoretical plates 5-50.

12. An isophoronediamine prepared by the process of claim 1.

13. The process according to claim 2, wherein the partial condenser is installed at the top of the first vacuum distillation column and is attached inside the column or outside the column.

14. The process according to claim 2, wherein the vapor stream in the first vacuum distillation column is pre-cooled and consequently partly condensed in the partial condenser and the condensed liquid is used as return stream in the vacuum distillation column.

15. The process according to claim 2, wherein the uncondensed vapor stream in the first vacuum distillation column is fully condensed and divided into an organic phase and an aqueous phase in a second condenser, wherein the organic phase is partly used as reflux for the first vacuum distillation column.

16. The process according to claim 2, wherein IPDA leaves the first vacuum distillation column as bottoms stream and is sent to a second vacuum distillation column for removal of the high boilers.

17. The process according to claim 2, wherein the pure IPDA is obtained at the top of the second vacuum distillation column.

18. The process according to claim 2, wherein the partial condenser is operated under the following conditions: TABLE-US-00015 Temperature 40-120° C.; and Pressure 10-200 mbar.

19. The process according to claim 2, wherein the employed first vacuum distillation column comprises the following parameters: TABLE-US-00016 Pressure 10-200 mbar; Bottoms temperature 80-200° C.; and Theoretical plates 10-80.

20. An isophoronediamine prepared by the process of claim 2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Reference will now be made to the accompanying drawings wherein like reference characters designate the same or similar parts throughout the several views, and wherein:

[0012] FIG. 1 is a chemical reaction showing the chemical reaction of isophorone nitrile (IPN) to make isophoronediamine (IPNA);

[0013] FIG. 2 is a block diagram of the IPNA chemical reaction of FIG. 1 including step a—reductive amination reaction, b distillative ammonia removal and c fine distillation of IPA; and

[0014] FIG. 3 is a schematic perspective view of the column setup with partial condenser for fine distillation of IPNA.

DETAILED DESCRIPTION

[0015] This entire process for producing pure IPDA is divided into three sections (see FIG. 2). In section a the reaction is effected by aminating hydrogenation of isophorone nitrile in a single- or multi-stage process in the presence of at least ammonia, hydrogen and a catalyst. In section b the distillative removal of ammonia and hydrogen to obtain crude IPDA is affected. The distillation may be performed in one or more columns. In section c the fine purification of crude IPDA is effected by distillative removal of IPDA, water, low boilers and high boilers. The fine purification is performed in two columns.

[0016] The crude IPDA generally has the following composition in weight % (wt %):

TABLE-US-00001 IPDA 75-100 wt % Water 0-15 wt % Low boilers 0-6 wt % High boilers 0-6 wt %

[0017] Low boilers are defined as byproducts from the production process having a lower boiling point than IPDA. High boilers are defined as byproducts from the production process having a higher boiling point than IPDA.

[0018] The crude IPDA I is initially passed into the first vacuum distillation column, see FIG. 3. The partial condenser is installed at the top of the first vacuum distillation column and may be attached either inside the vacuum distillation column or outside the distillation column. The vapor stream is thus pre-cooled and consequently partly condensed in the partial condenser. The condensed liquid is used as return stream in the vacuum distillation column. The uncondensed vapor stream is subsequently fully condensed and divided into an organic phase 3 and an aqueous phase 2 in a second condenser, wherein the organic phase 3 is partly used as reflux for the first vacuum distillation column (phase 7). The other part and the aqueous phase serve as discharge for low boilers and water. The IPDA leaves the vacuum distillation column as bottoms stream and is sent to a second vacuum distillation column for removal of the high boilers, the pure IPDA being obtained here at the top of the second vacuum distillation column.

[0019] The partial condenser is operated under the following conditions:

TABLE-US-00002 Temperature 40-120° C. Pressure 10-200 mbar

[0020] The employed 1st vacuum distillation column has the following parameters:

TABLE-US-00003 Pressure 10-200 mbar Bottoms temperature 80-200° C. Theoretical plates 10-80

[0021] The composition of the feed stream (crude IPDA II) from the 1st vacuum distillation column into the 2nd vacuum distillation column has the following composition:

TABLE-US-00004 IPDA 90-100 wt % High boilers  0-10 wt %

[0022] The employed 2nd vacuum distillation column has the following parameters:

TABLE-US-00005 Pressure 10-200 mbar Tops temperature 80-200° C. Theoretical plates 5-50

[0023] The purity of the pure isophoronediamine shall be at least 98 wt %.

EXAMPLES

Example 1

Comparative Example

[0024] The distillation was simulated using Aspen Plus. In the comparative example a setup composed of two vacuum distillation columns was chosen. At the top of the first distillation column a decanter was used to separate the two liquid phases, only the organic phase being used as reflux for the vacuum distillation column. The first vacuum distillation column had 36 theoretical plates and the second vacuum distillation column had 15 theoretical plates, with reflux-to-feed ratios of 1.1 (first vacuum distillation column) and 1.4 (second vacuum distillation column). The column pressure of the first vacuum distillation column was set to 110 mbar and that of the second vacuum distillation column was set to 80 mbar.

[0025] The feed stream employed at the following composition in weight % (wt %):

TABLE-US-00006 IPDA 88.6 wt % Water  9.1 wt % Low boilers  1.2 wt % High boilers  1.1 wt %

[0026] In the first vacuum distillation column the removal of the low boilers and of the water was effected at a bottoms temperature of 168° C. and a tops temperature of 95° C. The feed stream from the first vacuum distillation column into the second vacuum distillation column thus had the following composition:

TABLE-US-00007 IPDA 98.7 wt % High boilers  1.3 wt %

[0027] In the second vacuum distillation column the fine purification of IPDA was effected at a bottoms temperature of 187° C. and a tops temperature of 159° C. A purity of 99.95 wt % was achieved. The total loss of IPDA over the 2 vacuum distillation column system was 0.2 wt %

[0028] At a chosen feed mass flow of 2160 kg per hour

[0029] the heating power required was: 1184 kW

[0030] and the cooling power required was: 1232 kW.

Example 2

Inventive Vacuum Distillation Column Setup

[0031] The distillation was simulated using Aspen Plus. In the inventive example a setup composed of two vacuum distillation columns was chosen. At the top of the first vacuum distillation column a decanter was used to separate the two liquid phases. In addition, a partial condenser was installed upstream of the decanter. In this apparatus the vapor stream was first partially condensed and then added to the vacuum distillation column as reflux. The remaining vapor stream was subsequently fully condensed and separated into the two liquid phases via the decanter. The organic phase was likewise used as reflux for the vacuum distillation column. The first vacuum distillation column had 36 theoretical plates and the second vacuum distillation column had 15 theoretical plates, with reflux-to-feed ratios of 1.1 (first vacuum distillation column) and 1.4 (second vacuum distillation column). The column pressure of the first vacuum distillation column was set to 110 mbar and that of the second vacuum distillation column was set to 80 mbar.

[0032] The feed stream employed at the following composition in weight % (wt %):

TABLE-US-00008 IPDA 88.6 wt % Water  9.1 wt % Low boilers  1.2 wt % High boilers  1.1 wt %

[0033] In the first vacuum distillation column the removal of the low boilers and of the water was effected at a bottoms temperature of 168° C., a tops temperature of 117° C. and a partial condenser temperature of 74° C. The feed stream from the first vacuum distillation column into the second vacuum distillation column thus had the following composition:

TABLE-US-00009 IPDA 98.7 wt % High boilers  1.3 wt %

[0034] In the second vacuum distillation column the fine purification of IPDA was effected at a bottoms temperature of 187° C. and a tops temperature of 159° C. A purity of 99.95 wt % was achieved. The total loss of IPDA over the 2 column system was 0.2 wt %

[0035] At a chosen feed mass flow of 2160 kg per hour

[0036] the heating power required was: 1006 kW

[0037] and the cooling power required was: 1048 kW.

[0038] In the inventive distillation setup with the installed partial condenser the required heating and cooling powers were 15% lower than in the comparative setup.