PL219387B1 - Process for the dehydrochlorination of 1,3-dichloro-2-propanol - Google Patents

Description

Description of the invention

The subject of the invention is a method of dehydrochlorination of 1,3-dichloro-2-propanol formed during the chlorination of glycerol with gaseous hydrogen chloride or aqueous hydrochloric acid solution. The dehydrochlorination is performed on pure 1,3-dichloro-2-propanol or its aqueous solution containing up to several percent of water.

The dehydrochlorination of 1,3-dichloro-2-propanol obtained during the chlorination of glycerol or the chlorohydroxylation of allyl chloride is the subject of several Solvay patents. The most important contents of the applied solutions are presented in the patent applications: WO 2008/101866, WO 2009/095429, USA 2010/0032617. They show the dehydrochlorination of pure 1,3-dichloro-2-propanol or solutions containing this compound in significant amounts. In US patent 2010/0032617, neat 1,3-dichloro-2-propanol or in a mixture with 2,3-dichloro-1-propanol was subjected to dehydrochlorination. The process was based on intense mixing

1,3-dichloro-2-propanol or a solution with 2,3-dichloro-1-propanol with an alkaline agent, such as: sodium hydroxide solution, calcium oxide solution in water, for several to several dozen minutes, at room temperature to 45 ° C, with a slight molar excess of 1,3-dichloro-2-propanol to the alkaline agent. The process was carried out in a continuous or batch mode in a reactor with a mechanical stirrer, optionally with recirculation. After several minutes of stirring, the post-reaction solution was separated in order to separate the epichlorohydrin layer from the aqueous salt solution, respectively NaCl or CaCl2 solution. The disadvantage of this procedure is the incomplete conversion of dichloropropanols, as well as the relatively high content of organic compounds, including epichlorohydrin, in the aqueous layer, which requires additional unit operations such as neutralization and extraction or filtration. The process produces a large variety of by-products such as glycerol, chloroethers, chloroacetone, hydroxyacetone, glycidol, 3-chloro-1,2-propanediol, 2-chloro1,3-propanediol. A similar procedure is shown in WO 2008/101866. The dehydrochlorination was carried out on a mixture of 1,3-dichloro-2-propanol and 2,3-dichloro-1-propanol in which the content of 1,3-dichloro-2-propanol was at least 10% by weight. In the international application WO 2009/095429, additional steps are presented to remove organic compounds from the aqueous layer and thereby process the aqueous layer to obtain solid sodium chloride or its solution for diaphragm or diaphragm electrolysis. As a result, the sodium hydroxide or a solution thereof required for the dehydrochlorination can be produced while producing chlorine at the same time. Thus, methods of crystallization of sodium chloride from the aqueous layer by means of vacuum evaporation are presented. The implementation of this production node would enable the closing of the chlorine cycle in the integrated epichlorohydrin production installation. From the Polish patent application P. 398535 there is known a method for the preparation of epichlorohydrin, consisting in dehydrochlorination with a solution of milk of lime 1,3-dichloro-2-propanol obtained during the chlorination of glycerol with gaseous hydrogen chloride, which is characterized by mixing and pre-dehydrochlorinating 1,3- dichloro-2-propanol in the pre-reactor continuously. The reaction mixture is then directed to a reaction stripper equipped with an evaporator. In an evaporator, epichlorohydrin and the remaining volatile organic compounds are distilled off in a steam stream at a temperature of 70 to 120 ° C and the effluent is discharged outside. The pre-dehydrochlorination in the pre-reactor is carried out at a temperature of 40 to 70 ° C and a pressure of 40 to 80 kPa for 1 second to 60 minutes.

The method of dehydrochlorination of 1,3-dichloro-2-propanol with a calcium hydroxide solution continuously according to the invention is characterized in that 1,3-dichloro-2-propanol and a calcium hydroxide solution are introduced into the reaction part of the packed column, stirring at 85 to 95 ° C, atmospheric pressure or reduced pressure, directed to the stripping section of the column. In the stream of direct steam, the epichlorohydrin-water azeotrope is distilled off together with unreacted 1,3-dichloro-2-propanol and by-products, and the stream in the distillation part of the column is washed with a water layer, obtained after condensing the distillate in a condenser, separating the epichlorohydrin layer in a separator . The epichlorohydrin layer is the actual reaction product, and the effluent produced in the process is discharged from the bottom of the column. The aqueous layer obtained after the condensation of the distillate is completely or partially returned to the top of the distillation part of the column. Direct steam is supplied to the stripping section of the column at a temperature such that the temperature in the stripping section of the column is 85-101 ° C. Preferably, the steam is fed directly at a temperature of 105-120 ° C. You can

Also, direct steam at a temperature lower than 105 ° C is supplied, then the missing amount of heat needed to obtain a temperature of 85-101 ° C in the stripping part of the column is obtained by heating the column through diaphragm heating and 1,3-dichloro 2-propanol. Preference is given to using calcium hydroxide and 1,3-dichloro-2-propanol in a molar ratio of 1.00 - 1.04: 1, because then the process is carried out with the highest conversion of 1,3-dichloro-2-propanol and selectivity of the conversion to epichlorohydrin.

In order to obtain high conversion of 1,3-dichloro-2-propanol and selectivity of conversion to epichlorohydrin, it is important to quickly heat the mixture consisting of a 1,3-dichloro-2-propanol solution and a calcium hydroxide solution to a temperature of about 80-95 ° C, at atmospheric pressure or at a pressure of 60-100 kPa at the top of the reaction column. At the same time, epichlorohydrin is removed from the aqueous solution in a stream of steam immediately as it is formed. As a result, side reactions are limited. They consist in the hydration of epichlorohydrin to 3-chloro-1,2-propanediol, its dehydrochlorination to glycidol, hydration of glycidol to glycerol and polyetherification with glycerol and / or glycidol. The course of these reactions can be written as follows:

+ H, O -HCI + H ₂ O

CH ₂ —CH-CH ₂ - ^ CHo — CH— CH ₂ - * CH ₂ —CH-CH ₂ - * \ / ^{1 1} 1 I \ / JL

O Cl OH OH Cl O OH

CH ₂ —CH — CH ₂ —> (ch ₂ OH — CHOH — CH ₂ ) _n O

OH OH OH

The direct steam is introduced to keep the post-reaction solution boiling at the bottom of the column. This temperature in the stripping section, depending on the water vapor flow resistance caused by the filling and the degree of covering of the filling with sediments (mainly CaCO3), as well as the salt content in the sewage, is 85 to 101 ° C. This is most effectively achieved by introducing direct steam at a temperature of 105-120 ° C using a bubbler system. The direct steam mixes the components of the reaction mixture in the stripping section of the column and carries epichlorohydrin into the distillation section at the time of its formation. A small amount of 1,3-dichloro-2-propanol passes into the distillation part of the column together with the epichlorohydrin-water azeotrope (bp = 88 ° C, epichlorohydrin content 75% by weight), because it forms an azeotrope ₃ with boiling point (t _at = 93 ° C). At the concentration of Ca (OH) ₂ in the sewage of 1 g / dm, the concentration of glycerol ₃ should not exceed 1.4 g / dm. Increasing the Ca (OH) ₂ concentration in the sewage increases the glycerol content. Reducing the alkalinity of the sewage reduces its glycerol content, but at the same time the conversion of 1,3-dichloro-2-propanol decreases and it is discharged to a greater extent with the sewage. In the industrial process, the current control of the correct course of the dehydrochlorination will be achieved by continuous measurement of the pH of the sewage, which should be 10.0-11.5 in a properly running process.

The advantage of the new method of dehydrochlorination of 1,3-dichloro-2-propanol is the possibility of obtaining full conversion of this raw material with high selectivity of conversion to epichlorohydrin at the same time. The use of a concentrated solution of 1,3-dichloro-2-propanol allows to significantly reduce the amount of sewage.

The method of dehydrochlorination of 1,3-dichloro-2-propanol is further illustrated in the following working examples and in the drawing showing the process flow chart.

P r z k ł a d I

A solution of 1,3-dichloro-2-propanol heated to 85 ° C is introduced into reaction part 2 of the column. At the same time, 10-18% of the pipes are supplied with the second pipe system. lime milk solution. Due to the targeting insert, the reaction mixture flows into the center of the reaction column and then flows after filling the reaction and stripping portions of the column. The packing of the column is formed by Raschig's, Białecki's or Pall's rings. As the reaction mixture moves down the column, 1,3-dichloro-2-propanol and small amounts of the remaining -2,3-dichloro-1-propanol, 3-chloro-1,2-propanediol compounds are reacted. At the same time, a stream of direct water vapor at a temperature of 105 ° C under atmospheric pressure is fed countercurrently to the downstream reaction mixture in stripping section 1 of the column. In this stream na4

The epichlorohydrin formed, a by-product of unreacted 1,3-dichloro-2-propanol, is distilled off. Water vapor with epichlorohydrin flows through reaction part 2 and distillation part 3 of the column. In the distillation part 3, the vapors are washed with the water layer formed after the distillate decomposition in the Florentine separator 5. The organic layer from this stratification is crude epichlorohydrin (the lower layer contains 94-98% by weight of epichlorohydrin). The aqueous layer comprises epichlorohydrin 3-5% by weight, 1,3-dichloro-2-propanol 0.5-5% by weight, 3-chloro-1,2-propanediol 0.1-0.6% by weight. A waste water containing up to about 0.1 wt. % glycerol, 1.5-1.9 wt.%. calcium chloride, 0.1-03 wt.% calcium hydroxide, 0.01 wt. calcium carbonate; and polyglycerols. The height of the distillation part corresponds to

6. to 10 theoretical plates. The bottom of the column corresponds to the 10th to 15th theoretical plates.

P r z x l a d II

430.0 g of an aqueous solution were introduced into the reaction part of the 2 column at a rate of 3 ml / min

1,3-dichloro-2-propanol at a concentration of 88% by weight. The solution was heated to 90 ° C before being introduced into the column. An independent feed system was fed at a rate of 8 ml / min with 140.8 g of a calcium hydroxide solution at a concentration of 14% by weight. When the solutions were mixed, the dehydrochlorination reaction was initiated. The dehydrochlorination was carried out at atmospheric pressure. The mixture of the reactants and the resulting products ran down the reaction portion 2 and stripping portion 1 of the column in countercurrent to the downstream direct steam column at 110 ° C. Steam was introduced at a rate of 2 ml / min. The epichlorohydrin-water azeotrope, and with it the 1,3-dichloro-2-propanol-water azeotrope and volatile by-products distilled off in the steam stream. The stream of epichlorohydrine-water vapors together with the vapors of 1,3-dichloro-2-propanol and 3-chloro-1,2-propanediol condensed in the condenser-condenser 4. The condensate separated into the aqueous (upper) and epichlorohydrin (lower) layers in a Florentine separator 5. The water layer ran down to the tank 6 and was recirculated by the pump to the dew point of the distillation part 3 of the column. In the test, 186.9 g of the water layer was obtained with the composition: epichlorohydrin 5.60% by weight; 1,3-dichloro-2-propanol 1.93 wt.%; dichloro-1-propanol 0.02 wt.%; water 92.45 wt.% At the same time, 276.60 g of the organic layer (crude epichlorohydrin) was collected with the composition: epichlorohydrin 98.5% by weight; 1,3-dichloro-2-propanol 1.47 wt.%; 2,3-dichloro-1-propanol 0.03 wt.% In the test, 1088.7 g of sewage containing the following organic compounds were collected: glycerol 0.16 wt.%; 3-chloro-1,2-propanediol 1.10 wt.%; 2,3-dichloro-1-propanol 0.01 wt.% From the presented compositions and sizes of streams, after making the material balance, it results that the conversion of 1,3-dichloro-2-propanol is 98.2% and the selectivity of the conversion to epichlorohydrin with respect to the reacted dichloropropanol is 92.9%.

P r x l a d III

484.4 g of pure 1,3-dichloro-2-propanol and 149.5 g of 14% were introduced into the reaction part of the column 2 as in Example 1 at a rate of 3.0 ml / min. calcium hydroxide solution at a rate of about 9.0 ml / min. Simultaneously, 320 ml of water vapor at 105 ° C was introduced from the bottom of the column at a rate of 2 ml / min. The calcium hydroxide solution was heated to 50 ° C and 1,3-dichloro-2-propanol to 80 ° C before loading on the column. The process was carried out at a pressure of 70.5 kPa and a temperature of 85 ° C in the reaction part 2 of the column and 101 ° C in the stripping part 1 of the column. The amounts of the introduced substrates, the obtained products (epichlorohydrin and water layer), the collected sewage and the obtained conversion of 1,3-dichloro-2-propanol and the selectivity of the conversion to: epichlorohydrin, 3-chloro-1,2-propanediol, glycerol are presented in the table.

SUBSTRATES Quantity 1,3-dichloro-2-propanol g 484.4 moth 3.755 calcium hydroxide g 149.5 moth 2.020 water (including steam) g 998.8 (320.0) DISTILLATE - epichlorohydrin layer g 334.0 epichlorohydrin g 290.90 moth 3.103

PL 219 387 B1 cont. table

1,3-dichloro-2-propanol g 28.7 moth 0.222 water g 14.4 DISTILLATE - water layer g 326.1 epichlorohydrin g 16.8 moth 0.182 1,3-dichloro-2-propanol g 4.97 moth 0.038 2,3-dichloro-1-propanol g 0.25 moth 0.0 19 water g 304.0 SEWAGE g 969.1 epichlorohydrin g 0.84 moth 0.042 1,3-dichloro-2-propanol g 0.22 moth 0.002 2,3-dichloro-1-propanol g 0.90 moth 0.007 3-chloro-1,2-propanediol g 5.55 moth 0.05 glycerol g 15.10 moth 0.164 Conversion of 1,3-dichloro-2-propanol % 92.7 Selectivity of the conversion to: epichlorohydrin % 93.6 3-chloro-1,2-propanediol % 1.6 glycerol % 4.6

Patent claims

Claims (6)

1. The method of dehydrochlorination of 1,3-dichloro-2-propanol with a calcium hydroxide solution in a continuous manner, characterized in that 1,3-dichloro-2-propanol and a calcium hydroxide solution are introduced into the reaction part (2) of the packed column , is stirred at a temperature of 85 to 95 ° C, under atmospheric or reduced pressure, directed to the stripping section (1) of the column, then the epichlorohydrin-water azeotrope is distilled off in a stream of direct water vapor together with unreacted dichloro-2-propanol and by-products and the stream is washed in the distillation part (3) of the column with the water layer obtained after condensing the distillate in the condenser (4), separating the epichlorohydrin layer in the separator (5). 2. The method according to p. A process as claimed in claim 1, characterized in that the obtained aqueous layer is partially returned to the top of the distillation part (3) of the column. 3. The method according to claim 1, characterized in that direct steam is supplied to the stripping section (1) of the column at a temperature such that the temperature in the stripping section (1) of the column is 85-101 ° C. 4. The method according to p. The process of claim 3, characterized in that direct steam is supplied at a temperature of 105-120 ° C. 5. The method according to p. 3. The method according to claim 3, characterized in that direct steam with a temperature lower than 105 ° C is supplied, and the missing amount of heat needed to obtain the temperature of 85-101 ° C in the stripping part (1) of the column is obtained by membrane heating of the column and 1, 3-dichloro-2-propanol. PL 219 387 B1 6. The method according to p. The process of claim 1, wherein calcium hydroxide and 1,3-dichloro-2-propanol are used in a molar ratio of 1.00 - 1.04: 1.