PROCESS FOR WORKUP OF A CRUDE ESTER COMPRISING ESTERIFICATION CATALYST HYDROLYSIS PRODUCT IN SUSPENDED PARTICULATE FORM

Abstract

In a process for workup of a crude ester comprising esterification catalyst hydrolysis product in suspended particulate form, a) the crude ester is admixed in an emulsifying tank with 1% to 10% by weight of water and the water is emulsified in the crude ester to obtain a suspoemulsion, b) the suspoemulsion from the emulsifying tank is transferred to an agglomerating tank containing an initial charge of water-undersaturated crude ester, such that a water content below the solubility limit of water in the crude ester is established in the mixture of the suspoemulsion and the initial charge of crude ester, as a result of which the suspended particulate esterification catalyst hydrolysis products form stable agglomerates, and c) the agglomerates formed are filtered off.

Claims

1. A process for workup of a crude ester product that includes an esterification catalyst hydrolysis product in suspended particulate form, the process comprising a) admixing the crude ester product in a tank with 1% to 10% by weight of water, based on the crude ester, and emulsifying the aqueous crude ester product to obtain a suspoemulsion, b) transferring the suspoemulsion from the tank to an agglomerating tank containing an initial charge of water-undersaturated crude ester, wherein the water content is below the solubility limit of water in the combined mixture of the suspoemulsion and the initial charge of the water-undersaturated crude ester, upon which the suspended particulate esterification catalyst hydrolysis product forms stable agglomerates, and c) separating the agglomerates from the combined crude ester suspoemulsion product.

2. The process according to claim 1, wherein the crude ester has an acid number of less than 0.1 mg KOH/g crude ester.

3. The process according to claim 1, wherein the emulsifying the aqueous crude ester product in step a) with at least one mixer at a Reynolds number of greater than 10.sup.4 with a volume-specific power input in the range from 0.4 to 2.54 kW/m.sup.3.

4. The process according to claim 1, wherein the emulsifying the aqueous crude ester product in step a) with at least one stirrer at a circumferential speed in the range from 2.8 to 6.2 m/s.

5. The process according to claim 1, wherein the suspoemulsion obtained in step a) comprises distributed water droplets having a mean particle size of more than 10 μm to less than 2000 μm.

6. The process according to claim 1, wherein the tank has a height/diameter ratio H/D within a range from 1 to 6.

7. The process according to claim 1, wherein the water content in the agglomerating tank is maintained below the solubility limit of water in step b) by continually distilling off water.

8. The process according to claim 1, wherein the suspoemulsion is mixed in the tank with at least one mixer at a volume-specific power input of less than 0.2 kW/m.sup.3.

9. The process according to claim 1, wherein the the combined crude ester suspoemulsion product from step c) is subjected to a stripping treatment.

10. The process according to claim 1, wherein the suspended particulate esterification catalyst hydrolysis product is an esterification product of an esterification reaction catalyzed by a metallic esterification catalyst with an aqueous base from which a portion of water was removed from the esterification product/base mixture.

11. The process according to claim 10, wherein the aqueous base is added to the esterification product at a temperature T of more than 100° C. under a pressure p equal to or greater than the vapor pressure of water at the temperature T.

12. The process according to claim 10, wherein the water is from the esterification product/base mixture by decompressing the esterification product/base mixture.

13. A process for workup of a crude ester product, the process comprising a) admixing the crude ester product in an emulsification tank with 1% to 10% by weight of water, based on the crude ester product, and emulsifying the aqueous crude ester product to obtain a suspoemulsion, the emulsification conducted with a volume-specific power input in a range from 0.6 to 2.0 kW/m.sup.3, wherein the crude ester is an esterification product of an esterification reaction catalyzed by a metallic esterification catalyst with an aqueous base from which a portion of water was removed from the esterification product/base mixture, b) transferring the suspoemulsion from the emulsification tank to an agglomerating tank that contains an initial charge of water-undersaturated crude ester product to provide a mixture of the suspoemulsion and the initial charge of the water-undersaturated crude ester, wherein the water content in the mixture is maintained below the solubility limit of water of the crude ester product with a continuous removal of water from the agglomerating tank, and upon which the suspended particulate esterification catalyst hydrolysis product forms stable agglomerates, and c) separating the agglomerates from the mixture of crude ester suspoemulsion product.

14. The process according to claim 13, wherein the mixture in the agglomerating tank is stirred with a mixer at a volume-specific power input of less than 0.2 kW/m.sup.3.

15. The process according to claim 13, wherein the crude ester product has an alcohol content of 1 to 6 wt %, based on the crude ester product, and suspoemulsion of step a) comprises distributed water droplets having a mean particle size of more than 200 μm to less than 2000 μm.

Description

FIGURES AND EXAMPLES

[0097] The invention is elucidated in detail by the appended drawings 1 and 2, and examples 1 to 4 which follow.

[0098] FIG. 1A: shows a schematic longitudinal section through an illustrative embodiment of an emulsifying tank for performance of step a) of the process according to the invention,

[0099] FIG. 1B: shows a schematic cross section through an illustrative embodiment of an emulsifying tank for performance of step a) of the process according to the invention,

[0100] FIG. 2: shows, by way of example, the relationship between temperature and water content of the crude ester and the solubility of water in the crude ester.

[0101] In FIGS. 1A and 1B, the following reference numerals are used: [0102] 1 emulsifying tank [0103] 2 first baffle [0104] 2′ second baffle [0105] 2″ third baffle [0106] 2′″ fourth baffle [0107] 3 stirrer system [0108] 4 stirrer disk [0109] 5 stirrer blade

[0110] FIG. 1 shows, by way of example, the construction of an emulsifying tank 1 for performance of the process according to the invention. The emulsifying tank consists of a vessel in which is disposed a stirrer system 3. By way of example, the stirrer system 3 is configured as a disk stirrer having a stirrer disk 4 with six stirrer blades 5 disposed thereon. Four baffles 2, 2′, 2″, 2′″ are disposed on the vessel wall. As drive for the stirrer system 3, a 75 kW motor may be used, in order to achieve a specific power at the stirrer shaft in the range from 1 to 3.5 kW/m.sup.2. The stirrer speed may especially be set within the range between 80 to 140 rpm. The measurements cited are examples of the height/diameter ratio H/D claimed in accordance with the invention and of the baffles disposed on the vessel wall.

[0111] FIG. 2 is described in detail in example 3 which follows.

Example 1

[0112] A stream of 20 000 kg/h of crude diisononyl isophthalate (DINP) having an acid number of about 0.05 mg KOH/g and an alcohol content of 2.0% by weight was worked up continuously.

[0113] The DINP stream having a temperature of about 150° C. was admixed under a pressure of 6 bar with 100 kg/h of 2% aqueous sodium hydroxide solution (corresponding to an about 200% excess, based on the acid number of the crude ester). The mixed stream passed through a mixing zone. Then the stream was decompressed into a stirred vessel to about 100 mbar. The residence time in the stirred vessel was about 0.5 h, during which the mixture was stirred with a three-level crossbeam stirrer at 160° C.

[0114] The mixture was pumped over into an emulsifying tank, as shown in FIG. 1, and cooled to about 80° C. in the process. The pressure in the emulsifying tank was ambient pressure. The stirrer used was a disk stirrer having 4 baffles with a specific power at the shaft in the range from 1 to 3.5 kW/m.sup.3 at the speed of 80 to 140 rpm. 800 kg/h of water (corresponding to 4% by weight, based on the crude ester stream) were added. The residence time in the emulsifying tank was about 0.5 h, during which the mixture was mixed vigorously with a disk stirrer (specific power input: 3 W/I) at 85 rpm.

[0115] The suspoemulsion was transferred at a temperature of 80° C. to an agglomerating tank in which an initial charge of dry diisononyl phthalate from prior production was present. In the agglomerating tank, the pressure was about 150 mbar. The residence time in the agglomerating tank was about 0.5 h, during which the mixture was stirred with a three-level crossbeam stirrer with a low power input of less than 0.1 W/I. The vapors comprising water and alcohol were drawn off. A steady-state water content of 0.12% by weight was established. This value is below the solubility limit at the given temperature and the given alcohol content.

[0116] The suspoemulsion was transferred to a further agglomerating tank at a temperature of 90° C. In the further stirred vessel, the pressure was about 100 mbar. The residence time in the further stirred vessel was about 0.5 h, during which the mixture was stirred with a three-level crossbeam stirrer with a low power input of less than 0.1 W/I. The vapors comprising water and alcohol were drawn off.

[0117] The product was fed continuously via an intermediate vessel to a filter and filtered through a Teflon fabric of pore size 10 μm.

[0118] This gave a clear product, entirely free of catalyst residues, having an acid number of 0.01 mg KOH/g, an alcohol content of 1.3% by weight and a water content of 0.1% by weight. By stripping with steam, it was possible to reduce the alcohol content to less than 0.01% by weight.

Example 2

Variation of the Stirrer Speed in the Emulsifying Tank

[0119] Example 1 was repeated with variation in the volume-specific power input and the circumferential speed of the stirrer in the emulsifying tank, by stepwise alteration of the rotational speed of the stirrer in the emulsifying tank between 55 to 120 rpm, as shown in table 1 below.

TABLE-US-00002 TABLE 1 Emulsifying tank parameters and agglomeration characteristics Revolu- Circumfer- Volume-specific tions ential speed power input [rpm] [m/s] [kW/m.sup.3] Observation* 114 5.8 2.18 (+) 120 6.2 2.54 (−) sample cloudy 114 5.8 2.18 (+) sample slightly cloudy 110 5.6 1.96 (+) 100 5.1 1.47 (+) 85 4.4 0.90 (+) 75 3.8 0.62 (+) 65 3.3 0.40 (+) sample cloudy 55 2.8 0.24 (+) sample cloudy *(+): agglomerate formation (−): no agglomerate was formed

[0120] The effect of increasing the rotational speed to 120 rpm was that no agglomerates were formed any more. The product obtained has a higher filter resistance compared to example 1. As a result, the filter is blocked within a short time and the workup has to be stopped. The lowering of the rotational speed to below 70 rpm led to a cloudy ester; the cloudiness indicates the presence of non-agglomerated esterification catalyst hydrolysis product. Aside from that, agglomerates were visible and the product was filterable.

Example 3

Variation of the Temperature in the Agglomerating Tank

[0121] Example 1 was repeated with variation of the temperature in the agglomerating tank in 5 K stages in the range between 60 to 80° C. Because of the variation in temperature, there was also a change in the water content, since less water vapor is drawn off at lower temperature at a constant pressure of about 150 mbar. At each of the temperature stages, samples were taken from the tank and analyzed for water and alcohol content. For all the samples, the alcohol content was between about 1.6 and 2% by weight. The water content is shown in FIG. 2 as a continuous curve. FIG. 2 also shows the solubility curve of water in the crude ester (at an assumed alcohol content of 2% by weight, shown as a dotted trend line through the unfilled rhombus points). Above the solubility curve, water is present as a discrete phase. Up to a temperature of 65° C. and a water content of 0.27% by weight, it was possible to filter product continuously, and the agglomerates formed were visible. If, however, the sample comprising the agglomerates is cooled to room temperature, the free water precipitates out of the solution and the agglomerates are broken down within seconds, forming a white, aqueous precipitate at the base of the sample bottle.

Comparative Example

[0122] The lowering of the temperature in the agglomerating tank in the method of example 3 to below 65° C. at a water content exceeding 0.5% by weight resulted in a shutdown of the agglomeration process. The product has a higher filter resistance compared to example 1. As a result, the filter is blocked within a short time and the workup has to be stopped. As can be seen in FIG. 2, at a temperature below 65° C. and a water content of 0.5% by weight, the solubility of water in the crude ester is exceeded and water is present as a discrete phase. Under these conditions no stable agglomerates are formed.

Example 4

[0123] Example 1 was repeated with variation in the acid number AN of the crude diisononyl isophthalate (DINP) in the range between 0.045 to 0.1 mg KOH per g of solution in the agglomerating tank. The amount of sodium hydroxide solution was adjusted such that the crude ester was fully neutralized (200% excess). Up to an AN of 0.09, it was possible to filter product continuously. At AN of 0.1, the product has a higher filter resistance compared to example 1. As a result, the filter is blocked within a short time and the workup has to be stopped.