REMOVAL OF AL-SALTS, HCL, NACL AND ORGANIC BY-PRODUCT FROM DIOPAT SUSPENSION BY MEANS OF CERAMIC MEMBRANES IN STRONG ACIDIC CONDITIONS AT HIGH TEMPERATURE

Abstract

The present invention provides an improved process for isolating 2,4-bis-(2,4-dihydroxyphenyl)-6-(4-methoxyphenyl)-1,3,5-triazine (DIOPAT) from an aqueous alkaline mixture M comprising the DIOPAT, 2,4-dihydroxybenzophenone, and aluminum salts, wherein the process comprises the steps of precipitating the DIOPAT by acidifying the mixture M to a pH<1; heating the acidified mixture M to a temperature in the range of from 80° C. to 95° C.; and separating of the precipitated DIOPAT from the dissolved 2,4-dihydroxybenzophenone and the dissolved aluminum salts with a ceramic membrane by means of diafiltration.

Claims

1.-15. (canceled)

16. A process for isolating 2,4-bis-(2,4-dihydroxyphenyl)-6-(4-methoxyphenyl)-1,3,5-triazine (DIOPAT) from an aqueous alkaline mixture M comprising (i) the 2,4-bis-(2,4-dihydroxyphenyl)-6-(4-methoxyphenyl)-1,3,5-triazine; (ii) 2,4-dihydroxybenzophenone; and (iii) aluminum salts; wherein the process comprises the steps of a) precipitating the 2,4-bis-(2,4-dihydroxyphenyl)-6-(4-methoxyphenyl)-1,3,5-triazine by acidifying the mixture M to a pH<1; b) heating the acidified mixture M to a temperature in the range of from 80° C. to 95° C.; c) separating the precipitated 2,4-bis-(2,4-dihydroxyphenyl)-6-(4-methoxyphenyl)-1,3,5-triazine from the dissolved 2,4-dihydroxybenzophenone and the dissolved aluminium salts with a ceramic membrane by means of diafiltration with water, whereby the pH increases from <1 to at most 3 and the temperature remains in the range of from 80° C. to 95° C., wherein the separation step c) provides the precipitated 2,4-bis-(2,4-dihydroxyphenyl)-6-(4-methoxyphenyl)-1,3,5-triazine in the form of an aqueous suspension in the retentate, and the dissolved 2,4-dihydroxybenzophenone and the dissolved aluminum salts in the form of an aqueous solution in the permeate.

17. The process of claim 16, wherein acidifying in step a) is performed with hydrogen chloride, by adding the mixture M to an aqueous hydrogen chloride solution.

18. The process of claim 16, wherein the ceramic membrane is a TiO.sub.2, ZrO.sub.2, or Al.sub.2O.sub.3 membrane.

19. The process of claim 16, wherein the ceramic membrane has a pore size in the range of from 20 to 500 nm.

20. The process of claim 16, wherein the ceramic membrane has a pore size in the range of from 50 to 100 nm.

21. The process of claim 16, wherein the ceramic membrane is an α-Al.sub.2O.sub.3 membrane having a pore size of 50 nm.

22. The process of claim 16, wherein the ceramic membrane is an α-Al.sub.2O.sub.3 membrane having a pore size of 50 nm, and with 400/200/50 nm membrane layers.

23. The process of claim 16, wherein the ceramic membrane is provided in the form of a multi-channel element having a length of from 0.5 to 1.5 m and a channel diameter of from 3 to 8 mm, wherein the multi-channel element comprises from 7 to 19 channels.

24. The process of claim 16, wherein the feed pressure is from 1.0 to 4 bar and the cross flow is from 2 to 5 m/s.

25. The process of claim 16, wherein the separation step c) involves continuous washing of the suspension in the retentate with water, and removing of the permeate.

26. The process of claim 25, wherein the amount of washing water is at least three times as high as the amount of the suspension in the retentate.

27. The process of claim 25, wherein the washing water is heated before use, preferably by an external heat exchanger or direct steam injection.

28. The process of claim 16, wherein the concentration factor of the retentate is less than 2.5.

29. The process of claim 16, wherein the process further comprises the step of d) neutralizing the aqueous suspension of the retentate obtained in step c) to obtain a pH of from 6 to 8, and optionally simultaneously concentrating the aqueous suspension.

30. The process of claim 29, wherein neutralizing in step d) is performed with sodium hydroxide or sodium carbonate.

31. The process of claim 29, wherein the process further comprises the step of e) concentrating the neutralized aqueous suspension obtained in step d) by filtration, optionally after washing the neutralized aqueous suspension with water.

32. The process of claim 31, wherein the process further comprises the step of f) drying the concentrate obtained in step e).

Description

EXAMPLE

[0114] Diafiltration (DF) experiments were conducted in a low-pressure lab unit, designed for operation with HCl solutions up to 90° C.

[0115] The feed reactor was replaced by a long tube with heating jacket without agitator. This allowed homogeneous movement of the suspension with diafiltration (DF) water into the feed pump which made the final homogenization. Additionally, to avoid negative effects from clumps in suspension, the suspension was homogenized by means of an ultra-speed agitator (Ultra Turrax®).

[0116] Membrane Used:

TABLE-US-00001 Channel element 6 mm channel, 1 m long Membrane material α-Al.sub.2O.sub.3 Nominal pore size 50 nm with 400/200/50 membrane layers

[0117] Operating Parameters:

TABLE-US-00002 Temperature 85-90° C. Cross flow 3.5 and 4 m/s Feed pressure 1.5-2.5 bars

[0118] Process Parameters:

TABLE-US-00003 Dilution factor of the start suspension only dead volume of the pump Total concentration factor (CF) up to 2 Total diafiltration factor 4.5

[0119] Sampling: The sampling and the analysis were the same independent from the process step. After each total diafiltration factor or CF step, samples of permeate and retentate were taken for:

[0120] Dry content (DC) and NaCl content

[0121] Al content

[0122] Total Organic Carbon (TOC, only permeates)

[0123] DIOPAT content and content of side products (AHRT, 2,4-DHBP, DMPRT)

[0124] DC was measured with DC scales, NaCl was measured by titration, TOC was measured with a TOC analyzer. DIOPAT and side products were determined via HPLC using

[0125] Agilent 1100

[0126] column material: EUROSPH ER 100-C18/5 Knauer

[0127] column length: 25 cm, column diameter: 4 mm

[0128] column temperature: 20° C.

[0129] injection volume: 5 μl

[0130] mobile phase: eluent A: 900 Deionat (2)+100 acetate buffer pH 4.65 (3)+0.2% TBAHS, eluent B: acetonitrile (1)+0.2% TBAHS

[0131] method: flow: 1.0 mL/min, pressure: max. 400 bar, stop time: 30 min

[0132] timetable:

TABLE-US-00004 Time % A % B  5 min 50%   50% 25 min 0% 100% 30 min 0% 100%

[0133] According to the present invention, the Al-salts as well as undesired organic by-products are separated with a ceramic membrane by means of diafiltration with water. The cycle time was around 1 hour. Therefore, 3 kg DIOPAT suspension, comprising 93.2 g DIOPAT, 1.8 g resorcinol, 6.0 g benzoic acid, 2.4 g anisyl-hydroxy-resorcinyl-triazine (AHRT), 9.6 g 2,4-DHBP, 1.8 g DMPRT (dimethoxyphenylresorcinyltriazine), 2.544 kg water, 330.0 g NaCl, and 11.1 g AlCl.sub.3, was transferred to a vessel of suitable size.

[0134] The temperature was adjusted to 90° C. The 2,4-DHBP concentration in the feed DIOPAT suspension of the diafiltration was about 0.32%. The solubility of 2,4-DHBP in acidic water at 90° C. was about 0.18%. Thus, some 2,4-DHBP probably was already precipitated and had to be brought back into solution during the DF process. In the DF process, the DIOPAT suspension was held at 90° C. and was permanently washed with 12 kg fresh water. During the washing process, the DIOPAT concentration stayed constant. To separate the Al-salts and organic by-products, the DIOPAT suspension was pumped from the feed vessel to a ceramic membrane module and from there back to the feed vessel. In the ceramic membrane, the dissolved components (Al-salts and some org. components such as 2,4-DHBP) passed through the membrane. The DIOPAT particles stayed in the suspension and went back to the feed vessel. The permeate was send to the waste water treatment plant. In total, the suspension at the beginning of the membrane process (suspension after precipitation) was washed with a washing factor of 4.5. Then, the Al-salt concentration in the retentate was less than approx. 65 ppm.

[0135] The aqueous suspension was neutralized by 1.3 g NaOH (50% w/v). The neutralized retentate was concentrated by means of a Dyno Filter from Bokela to obtain 685.8 g of DIOPAT suspension, comprising 96.0 g (14%) DIOPAT.

[0136] After spray drying, 106.9 g spray dried DIOPAT mass, comprising 96.0 g (87.2%) DIOPAT, 0.07 g (0.05%) resorcinol, 0.10 g (0.1%) benzoic acid, 2.2 g (2.1%) AHRT, 1.7 g (1.6%) 2,4-DHBP, 1.8 g (1.7%) DMPRT (dimethoxyphenylresorcinyltriazine), 3.2 g (3%) water, 4.5 g (4.2%) NaCl, and 0.14 g (0.13%) AlCl.sub.3, was obtained.

[0137] Comparison of the effect of the temperature on the removal of 2,4-DHBP:

[0138] To assess the influence of the temperature on the residual amounts of 2,4-DHBP in the obtained DIOPAT concentrate after ultrafiltration, the procedure as described above was repeated under the following temperature conditions:

TABLE-US-00005 UF1 (72° C.) UF2 (89° C.) Susp Concentrate Susp Concentrate Parameter [%] [%] [%] [%] NaCl 14.63 0.49 14.63 0.24 DC 13.78 5.85 13.78 5.32 Diopat 3.00 4.65 3.00 4.67 2,4-DHBP 0.28 0.26 0.28 0.07 NaCl/Diopat 487.7 10.5 487.7 5.1 Diopat/DC 21.8 79.5 21.8 87.8 2,4-DHBP/Diopat 9.3 5.6 9.3 1.5

[0139] As can be seen, the amount of 2,4-DHBP in the Concentrate is significantly reduced, if the ultrafiltration is performed at temperatures of 88-91° C. in comparison to temperatures of 71-76° C.