PROCESS FOR PHASE SEPARATION OR EXTRACTION AND DEVICE SUITABLE THEREFOR

Abstract

The present invention relates to a device for separating two immiscible phases and/or for extracting one phase with another phase (phase separation or extraction device), comprising at least one vessel for receiving the at least two phases, at least one pipe for supplying a fluid to the vessel, at least one pipe for discharging a fluid from the vessel, and at least one arrangement comprising a transparent disk for observing the separation operation or the extraction operation, wherein at least the side of the transparent disk that faces the phases to be separated or extracted consists of sapphire (sapphire glass) or mica (mica disk), and to the use of such a device in the preparation of di- and poly-amines of the diphenylmethane series.

Claims

1-12. (canceled)

13. A process for the preparation of di- and polyamines of the diphenylmethane series, comprising: (i) reacting aniline with formaldehyde in the presence of an acidic catalyst to form an acidic reaction mixture; (ii) neutralizing the acidic reaction mixture with a base followed by separating an organic phase obtained thereby from an aqueous phase obtained thereby in a separation vessel; (iii) subjecting the organic phase to washing; and (iv) freeing the organic phase from excess aniline; wherein a device is used in at least one of the separating and washing steps, the device comprising: a) at least one vessel that receives a two-phase liquid mixture, b) at least one pipe that supplies the two-phase liquid mixture to the vessel, the two-phase liquid mixture being separated in the vessel into an organic phase and an aqueous phase, c) at least two pipes that discharge the organic phase and the aqueous phase from the vessel, and d) a transparent disk comprising sapphire or mica arranged on a side of the disk facing the two-phase liquid mixture in the vessel, wherein the transparent disk is arranged on the vessel so that phase separation taking place in the vessel is observable.

14. The process of claim 13, wherein the transparent disk consists of sapphire or mica.

15. The process of claim 13, wherein only the side of the transparent disk facing the two-phase liquid mixture in the vessel comprises sapphire or mica.

16. The process of claim 15, wherein the transparent disk is a composite of sapphire or mica and another transparent material selected from the group consisting of borosilicate glass and quartz glass.

17. The process of claim 16, wherein the side of the transparent disk facing the two-phase liquid mixture in the vessel consists of sapphire.

18. The process of claim 13, wherein the aqueous phase is alkaline.

19. The process of claim 18, wherein the aqueous phase has a pH value of from 8.0 to 14.

20. The process of claim 13, wherein the device extracts an organic phase containing di- and poly-amines of the diphenylmethane series with an aqueous phase.

21. The process of claim 13, wherein the device extracts an aqueous phase containing di- and poly-amines of the diphenylmethane series with an organic, aniline-containing phase.

Description

EXAMPLES

Construction and Fitting of the Sight Glasses:

[0030] Mounting of the sight glass is carried out in accordance with DIN 28120 (Circular sight glasses with case in main power connection). As the gasket there is used a graphite gasket with a steel insert of 1.4401 (gasket code letter NK).

[0031] The borosilicate sight glasses are produced according to DIN 7080. The sight glasses with sapphire or mica were produced, apart from the material, according to the same specification.

General Specification for Working Up Crude Di- and Poly-Amines of the Diphenylmethane Series

[0032] 32% sodium hydroxide solution is added in a molar ratio of 1.1:1 (sodium hydroxide solution to HCl) to an HCl-acidic reaction mixture containing inter alia the desired di- and poly-amines of the diphenylmethane series and excess aniline and water, and the mixture is reacted to completion in a stirred neutralisation vessel. The temperature is from 80 C. to 130 C. and the absolute pressure is from 0.7 to 2.0 bar.

[0033] The resulting mixture is then separated in a neutralisation separator, which is equipped with a sight glass, into an aqueous, lower phase which is fed to the waste water collection vessel. This water has a pH value of about 13, an NaCl content of about 21 wt. % and an NaOH concentration of about 2 wt. %. The organic, upper phase is fed to washing. In the stirred washing vessel, the organic phase is washed with condensed water vapour. After the wash water has been separated off in the wash water separator, which is equipped with a sight glass, the moist mixture of MDA and PMDA is pumped into a collecting vessel. The wash water which has been separated off, which has a pH value of about 11, an NaCl content of about 0.2 wt. % and an NaOH concentration of about 0.8 wt. %, is likewise transferred to the waste water collecting vessel. The water from the waste water collecting vessel, which consists of the water of the neutralisation, the washing and other water streams from the reaction and distillation and which has a pH value of about 13, an NaCl content of about 7 wt. % and an NaOH concentration of about 0.8 wt. %, is extracted with fresh aniline in the waste water extraction.

Example 1 (Comparison)

[0034] Use of a conventional sight glass of borosilicate glass in all apparatuses equipped with a sight glass. Because leakages occur at random, there are unplanned stoppages in production.

Example 2 (According to the Invention)

[0035] Use of a borosilicate sight glass protected on the product side with a mica disk in all apparatuses equipped with a sight glass.

Example 3 (According to the Invention)

[0036] Use of a sapphire sight glass in all apparatuses equipped with a sight glass. There are no leakages. The sapphire glass does not become scratched either.

Example 4 (According to the Invention)

[0037] Use of a two-layer sight glass of sapphire (product side) and borosilicate glass (on the side that is remote from the product) in all apparatuses equipped with a sight glass.

The table below summarises the results:

TABLE-US-00001 TABLE Material, lifetime, damage Neutralisation Waste water separator Washing extraction Lifetime Dam- Lifetime Dam- Lifetime Dam- Example (months) age (months) age (months) age 1 6 pitted 12-15 pitted 12 pitted (compar- ison) 2 >24 none >24 none >24 none (according to the invention, mica/ boro- silicate) 3 >36 none >36 none >36 none (according to the invention, solid sapphire) 4 >24 none >24 none >24 none (according to the invention, sapphire/ boro- silicate)

[0038] Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.