SU655699A1 - Method of purifying phthalic acid esters - Google Patents

Description

one

The invention relates to an improved method for the continuous purification of phthalic acid esters. The esters obtained are used mainly as plasticizers of various thermoplastics.

Methods are known for the purification of phthalic acid esters obtained in the presence of acidic catalysts by neutralizing the acidic components, washing the neutralizing salts, distilling off excess alcohol and water, and treating with sorbents and filtering.

Thus, a method of purification of dibutylphthalate is described, which consists in distilling the main mass of butanol at a residual pressure of 50-90 mm Hg, neutralizing it with an aqueous solution of sodium carbonate, washing neutralization salts and distilling water, volatile and butanol residues on a cap dish-shaped column with an acute superheated steam at a temperature of lOO-.lSOc and a residual pressure of 80-50 mm Hg, Art. one.

A known method of purification of esters by successive neutralization, washing and distillation of volatile acute superheated steam. In accordance with this method, the volatile stripping is carried out using several successive columns with a gradual deepening of the vacuum and countercurrent movement of the hot superheated steam relative to the ether 2.

The disadvantages of these methods are the high consumption of hot superheated steam and a large amount of chemical contaminated wastewater.

The technical essence and the achieved result to the described method is the closest method of purification of phthalic acid esters, in particular di- (2-ethylhexyl) -phthalate,

by neutralizing the acidic components with an aqueous solution of caustic soda at 60-70 s, separating the ether layer from the water-salt solution, washing the ether from the neutralization salts

water at -70-80 s, distillation from ether of excess alcohol and volatile acute superheated steam at a temperature of 155-165 ° C and a residual pressure not higher than 130 mm Hg, treatment of ether

sorbents and filtering. The consumption of hot superheated steam with 270-630 kg / t 3.

However, at the stage of distilling off with acute superheated BBW, raw suckers containing a large amount of 36% water and alcohol are fed in, to distill which requires a significant consumption of sharp superheated steam. The composition of the raw ether entering the stripping stage varies widely. The alcohol content varies from 6 to 20%, and water from 0.5 to 15%. This leads to a corresponding instability of the process at the stage of continuous distillation and the production of a non-conforming product. In order to eliminate this drawback, the consumption of acute superheated steam is additionally increased at the rate of the most unfavorable of the possible trick modes. With a high concentration of alcohol and water in the raw ether, their evaporation requires the expenditure of a significant amount of heat (the heat of evaporation of alcohol and water, respectively, 100 and 540 kcal / kg). In order to compensate for heat losses, it is necessary to additionally increase the consumption of hot superheated steam. An increase in the consumption of acute superheated steam leads to an increase in the amount of chemical effluent from the distillation stage. The loss of raw materials at the stage of distillation with chemical effluent is determined with the solubility of the alcohol and the desired product in the condensed condensed superheated vapor and the amount of condensate. Therefore, increased consumption of overheated steam leads to significant losses of raw materials. The aim of the invention is to reduce the loss of raw materials, reduce the consumption of acute superheated steam and the amount of chemical contaminated wastewater. The goal is achieved by the described method of purification of phthalic acid esters by neutralizing the acidic components with a solution of sodium hydroxide at 95 ° C, washing the ether from neutralization salts with water at 90 ° C, distilling excess alcohol and water by heating the ether to a temperature of 12 ° C to 170 ° C at - pressure from atmospheric to excessive 3 kg / cm, azeotropic distillation of water and alcohol from it by instant evaporation with a sharp deepening of the vacuum to a residual pressure of 20-150 mm Hg, re-heating the ether at a residual pressure of 20-150 mm Hg ..to temperatures of 140–200 ° C –– by distilling from it at the indicated temperature traces of water and distillation of the remaining alcohol with a sharp first vapor at 140–200 ° C and a residual pressure of 40–170 mm Hg, followed by sorbents and filtration. Distinctive features of the method are distillation of excess alcohol and water by heating the ether to a temperature of from 120 ° C at a pressure from atmospheric to: excess 9 foot 3 kg / cm, azeotroic distillation of water and alcohol from it instantaneous evaporation at a rare vacuum deepening to a residual pressure of 20150 mm Hg, re-heating the ether at a residual pressure of 20150 mm Hg. to a temperature of 140200 ° C with the removal of traces of water from it at the indicated temperature and the distillation of the remaining alcohol with hot superheated steam at a temperature of 140-200 ° C and a residual pressure of 40-170 mm Hg. The process technology is as follows. The continuous distillation unit consists of a pump for creating pressure up to 3 kg / cm, a heat exchanger for heating the crude ether to a temperature of 120-, a control valve for abrupt pressure relief from excess (0-3 kg / cm) to residual (20-150 mm Hg) .st.) ,. an expansion chamber in which instantaneous evaporation of water and alcohol, a heat exchanger for re-heating the crude ether to a temperature of 150-200 ° C, an apparatus for stripping volatile hot superheated steam, a system for condensing and cooling vapor, a Florentine vessel for separating condensate into alcohol, and water and receiver of the target product. As a heat exchanger, you can use any heat exchange apparatus, as a rule, shell-and-tube heat exchangers. A rotary film evaporator can be used for preheating in the second stage. The expansion chamber can be any hollow apparatus or free space of the heat exchanger of the second stage of distillation, for example, the expansion part of a rotary film evaporator. In the quality of an apparatus for distilling with superheated steam, it is advisable to use a cap plate column, on the upper plate of which the raw ether is fed, and in the lower part - sharp superheated steam. The method according to the invention can be implemented in the preparation of esters by the esterification of phthalic anhydride with normal aliphatic alcohols or isostructures with 4 to 12 carbon atoms or a mixture of these alcohols in the presence of acidic catalysts. - Butanol, for example, can be used as aliphatic alcohols. -ethyl texanol, dodecyl alcohol, a mixture of CJ alcohols - With a normal structure, a mixture of Cg -Cg alcohols and iso-alcohol, and as acid catalysts, for example, sulfuric acid, benzenesulfo islotu, p-toluene sulfonic acid. Example. On a continuous installation, including a 5 liter ether raw meter, a tube-in-tube heat exchanger, heated with hot glycerin, a throttling valve, a 0.5 l expansion chamber, a tube-in-tube heat exchanger for re-heating the Sior ether , A 1.5 liter of distillation apparatus with a bubbler for supplying hot superheated steam, two tube type condenser coolers in the tube for condensing and cooling alcohol and water vapor, a 0.7 L Florentine vessel for separating alcohol and water, and an ether receiver raw about emom 5 L distilled volatile di- {2-ethylhexyl) phthalate crude obtained by reaction of phthalic anhydride with 2-ethylhexanol. in the presence of benzenesulfonic acid as catalyst. The crude ether is preliminarily purified by a known method, namely, the acidic components are neutralized with an aqueous solution of alkali at a temperature of 95 ° C and atmospheric pressure and the neutralization salts are washed with water at a temperature and atmospheric pressure. The acid number of the crude ether, coming to the stage of distillation of volatiles, 0.07 mg KOH / G, the concentration of alcohol and water, respectively, 11 and 2 wt.%. Raw ether at a rate of 1 l / h from a raw ether meter through a heat transfer tube-type pipe in a pipe and a throttling valve is continuously fed to the expansion chamber. Pressure in the measuring device 3 kg / cm is created by compressed nitrogen. In the heat exchanger, the raw ether is heated to. The residual pressure in the expansion chamber and the heat exchanger for reheating the raw ether is 150 mm Hg. From the heat exchanger, the raw ether with a temperature of 170 ° C by gravity flows through the hydraulic lock into the distilled ap.erat, where the hot superheated steam is introduced at a speed of 250 g / h. The temperature in the otgene apparatus is 180 ° C, the residual pressure is 140 mm Hg. The alcohol content in the raw ether at the entrance to the distant cube is 4, 5 wt.%, The water content is 0.05 wt.%. Raw ether from the receiver is treated with sorbents in a known manner (0.5% of activated carbon and clay by weight of ether, temperature, residual pressure of 20 mm Hg) .. Indicators of the obtained di- (2-ethylhexyl) phthalate, corresponding to the first grade GOST 8728-66: Color by iodometric scale, number .o, 5 Acid number, mg KOH / G0.08 Flash point, ° С,, 206 Examples 2-4. The phthalic acid esters are purified as described in example 1, but with different values of the process parameters given in ny. The following table. The composition of the feedstock in the example: dibutyl phthalate, butanol, benzene sulfonic acid; in example 3: ester arch DAF-68, a mixture of alcohols Cg-Cg, sulfuric acid; in example 4: resin grade DAF-789, a mixture of alcohols CT-C, benzolulfonic acid; in example 5: didodecyphthalate, dodecyl alcohol, sulfuric acid.

Neutralization temperature, C

Washing temperature, ° С

Processing sorbents temperature, ° C

residual pressure, mm Hg

Indicators efiryyrtsa entering the stage of distillation

acid number, M1 / KS) Ig

alcohol content, wt.%

80

80

95 70

60

60

95 120

100 20 250 760

0.04 0.08 0.09 0.06

9.5

20

water content

weight.%

Stripping volatile

The heating

temperature, ° С

residual pressure, mm Hg

Instant evaporation 130 60 40 20 140 160 150 200 130 60 40 20

2.0 4.0 3.5 6.0 - - 0.03 0.02 140 170 170 200

The flash point of the target product, ether, purified. Under the conditions of Examples 2-5, is respectively 170; 202; 205 and.

Since the quality of distillation of volatiles is determined only by the flash point corresponding to the total plasticizer, the remaining indicators of the target product in the table are not given. For all the synthesized esters, the temperature BcntflflKH corresponds to the quality of the product of the first grade.

When carrying out the purification process according to the invention, the consumption of hot superheated steam is significantly reduced, since anhydrous ethyl raw material containing a small amount is supplied to the distillation step by this steam.

0.5 1.2

170

150

20,760

in alcohol (2-6% against 6-20% by a known method).

The stripping column operates in a stable mode, so an increased consumption of superheated superheated steam is not required to compensate for possible variations in the alcohol ether and water content. As a result, the flow rate of the hot superheated steam is further reduced.

The distillation of water and a significant part of the alcohol occurs in the first stage, where the heat necessary for evaporation is supplied by deaf steam, therefore the consumption of the hot superheated steam is reduced.

Reducing the flow rate of superheated steam leads to a decrease in

It is necessary to reduce the loss of raw material at the stage of distillation.

Claims (3)

Invention Formula The method of purification of phthalic acid esters by neutralizing the acidic components with an aqueous solution of alkali during heating, washing neutralization salts with water when heating, distilling off excess alcohol and water under heating and reduced pressure, processing sorbents and filtering, in order to reduce raw material losses, reducing the consumption of hot superheated steam and the amount of chemical effluent, excess alcohol and water are distilled off by heating the ether to a temperature of 120-170 ° C with pressure from „ atmospheric to excessive 3 kg / cm of azeotropic detritus from it of water and alcohol by instant evaporation with a sharp deepening of the vacuum to a residual pressure of 20-150 mm Hg, re-heating the ether at a residual pressure of 20-150 mm Hg. to temperature CEL 140-200-C with stripping from it at this temperature traces of water and distilling the remaining alcohol with superheated steam at a temperature of 140,200 0 and a residual pressure of 40170 mm Hg. Sources of information taken into account during the examination: 1- France Patent No. 2047642, cl. From 07 p. 67/00, 1970. 2, Patent of France 2098915, cl. C 07 S 64/00, 1970. 3. Regulation 108 of Nizhny Tagil plant.