JPS61167633A - Purification of allyl alcohol - Google Patents

Abstract

PURPOSE:To produce high-purity allyl alcohol, by adding dipotassium phosphate and/or potassium carbonate and glycerol to an aqueous solution of allyl alcohol, separating the mixture into an aqueous phase and an organic phase, distilling the organic phase, and recycling the mixture to the system. CONSTITUTION:The aqueous solution of allyl alcohol 1 uses as a raw material (a mixture of allyl alcohol and water at a ratio of about 70:30) is thoroughly mixed with a glycerol solution 2 of dipotassium phosphate and/or potassium carbonate in a mixing tank B to obtain a solution, and the solution is let stand in a phase-separator C and separated into the aqueous phase 4 and the oil phase 5. The azeotropic mixture is removed from the oil phase 5 in the first distillation column D and returned to the mixing tank B, and the column bottom consisting of a mixture of glycerol and allyl alcohol is distilled in the second distillation column E to obtain purified allyl alcohol. The glycerol 8 obtained from the column bottom is mixed with the aqueous phase 4 of the phase- separator C, the mixure is distilled in vacuum in the water-evaporator A to remove the water and the glycerol solution of salt is recycled to the mixing tank B.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a method for purifying allyl alcohol. More specifically, the present invention relates to a method for obtaining highly pure allyl alcohol by removing water from an aqueous solution of allyl alcohol.

[Conventional technology]

Allyl alcohol is an industrially useful substance as an intermediate for many chemicals and synthetic resins, such as glycerin and diallyl phthalate.

As a method for producing allyl alcohol, the following reaction formula (1) is used.
As shown in (2) above, a method is known in which allyl chloride is synthesized by spaced chlorination of propylene and then subjected to alkaline hydrolysis.

GHz = GHGHs + G-ex→OH, = GH
CH,C4+H(J(1)OH,=CHGH,G-g
+ NaOH→OH* = CHGHtQH−) N
a(J? (2) This method has problems such as consuming a large amount of expensive chlorine and severe corrosion of the equipment because it is necessary to handle chlorine and hydrogen chloride gas at high temperatures.

In recent years, a method has been proposed that can produce allyl alcohol using propylene as a raw material without having to deal with chlorine or hydrogen chloride. As shown in the following formulas (3) and (4), this method uses propylene in the presence of acetic acid with oxygen or an oxygen-containing gas as a catalyst, using an alkali acetate and palladium, and optionally a copper compound supported on a catalyst. After reacting in the gas phase [100-600°C, 0-60 atm (gauge pressure)] to obtain allyl acetate, the produced allyl acetate is cooled and collected, an acetic acid aqueous solution is added to make it homogeneous, and this homogeneous solution is Allyl alcohol is obtained by distilling the resulting reaction solution through a tubular reactor filled with a strongly acidic ion exchange resin and heated by a heating medium (for example, see % Peng Show No. 58-137768).

OH,=CH-0H1+AcOH+No.0°→CHt=G
HGH10AC+HtO(31GH,=0H-OH,
OAc+H, 0→OH, =GH-OH, OH+AcOH
(41 In these production methods, allyl alcohol is obtained as a water bath liquid, but allyl alcohol (boiling point 96-9
7°C) formed an azeotrope with water at a ratio of 72.3:27.7 (line point 87.5°C), so water could not be removed by simple distillation.

As a result of extensive research, the present inventors have found that by adding dipotassium phosphate and/or potassium carbonate to an aqueous allyl alcohol solution, the water content of the azeotropic composition can be reduced to 27.7%.
It was discovered that the amount of allyl alcohol could be reduced to 5-10%, and a separate application was filed as a method for purifying allyl alcohol (Japanese patent application 1986-
issue). This purification method uses dipotassium phosphate and/or
Alternatively, potassium carbonate is added in the form of solid or concentrated water bath liquid in an amount below the saturation concentration to the allyl alcohol water bath liquid, stirred and dissolved, and after standing still, the separated organic phase and aqueous phase are separated.This purification method is an industrial process, and when dipotassium phosphate and potassium carbonate are circulated at concentrations below the saturation concentration, if there are locally low temperatures in the system, or if the aqueous phase is too concentrated. When this occurs, salts precipitate, causing problems such as a decrease in the heat transfer coefficient and clogging of pipes. In addition, when all the water is evaporated from the aqueous phase to dryness to recover salts as solids for recycling use, there is a problem that the operation becomes complicated and the equipment cost increases.

[Problem that the invention seeks to solve]

The object of the present invention is to prevent the precipitation of salts when an industrial process is applied to purify allyl alcohol by adding dipotassium phosphate and/or potassium carbonate to an aqueous solution of allyl alcohol and removing the separated aqueous phase. The aim is to avoid the problems involved.

[Means and effects for solving the problem] The present inventors have discovered that the problems caused by salting out when dipotassium phosphate and potassium carbonate are recycled can be solved by adding salt to a solvent whose boiling point is much higher than that of water. We considered that the problem could be resolved by dissolving it and recycling it, and that it would be easy to separate it from allyl alcohol if the solvent had a sufficiently large difference in boiling point.

It has been found that many solvents that are themselves soluble in water separate into two phases in the presence of salts, and that when added to an allyl alcohol water bath along with the salt, the solvent is transferred towards the allyl alcohol phase and cannot be used. Among the few solvents that dissolve in concentrated aqueous solutions of dipotassium phosphate and potassium carbonate, ethylene glycol, propylene glycol, etc. have very low salt solubility, and when water is distilled off from a mixed solution of salt and water, the salt is dissolved. As a result of many experiments, it was discovered that only glycerin could be used for the purpose of the present invention, leading to the non-invention.

That is, in the present invention, dipotassium phosphate and/or potassium carbonate and glycerin are added to an allyl alcohol water bath solution, the water phase and the allyl alcohol phase are separated, and the allyl alcohol phase is distilled to obtain high purity allyl alcohol. In addition, it is a method for purifying allyl alcohol, which is characterized by recovering glycerin, adding the recovered glycerin to an aqueous phase, removing water by distillation, and recycling and using the salt as a glycerin solution. .

In the purification method of the present invention, glycerin, dipotassium phosphate, and/or potassium carbonate may be added to an allyl alcohol water bath solution (approximately 70% allyl alcohol, 60% mains) having an azeotropic composition. After stirring, an apparatus is used to separate an oil phase enriched in allyl alcohol and an aqueous phase in which salt and glycerin are dissolved.

The ratio of salts and glycerin to be added to the allyl alcohol aqueous solution is determined in consideration of the solubility of the salts in glycerin and the degree of phase separation. That is, if the weight ratio of glycerin to salts is less than 2 in the case of dipotassium phosphate and less than 1 in the case of potassium carbonate, the salts will precipitate when water is removed, and in both cases the weight ratio will be 4 or less. If it is more than that, allyl alcohol and water will not phase separate, so glycerin/salts = 1 to 4, preferably 5 to 6.5
is the dropper.

The greater the amount of salts added to the allyl alcohol aqueous solution, the better the water removal rate will be, but if the amount is too large, the amount of glycerin will also increase, and the amount of glycerin will be about 1.2 times that of allyl alcohol water fgri. Phase separation will no longer occur. Therefore, the appropriate weight ratio of the salts to be added is 0.5 to 2 to the water content in the allyl alcohol aqueous liquid.

According to the purification method of the present invention, water content can be reduced to 5 to 10% from an allyl alcohol aqueous solution having a close azeotropic composition, so that highly pure allyl alcohol can be obtained by distilling this. The allyl alcohol aqueous solution with an azeotropic composition that is initially distilled out at this time can be used again as a raw material for the purification process, and the glycerin dissolved in the allyl alcohol phase can also be recovered as a distillation residue, so it can be directly distilled or distilled under reduced pressure. It can be made of silk and used again. That is, the recovered glycerin can be added to an aqueous phase containing salt and glycerin, water can be removed by distillation, and the salt can be circulated and used as a glycerin solution. As described above, since salts are always present in the purification system of the present invention as solutions in glycerin or water, troubles associated with precipitation of salts do not occur at all. Glycerin is present in both the oil phase (allyl alcohol phase) and the aqueous phase at a fairly high concentration, but since its boiling point (290°C) is significantly different from allyl alcohol and water, they can be easily separated by distillation. .

A flowchart of an example of an industrial process using the purification method of the present invention is shown in FIG.

Raw material allyl alcohol water bath liquid (allyl alcohol approx. 7
0: Honsuri 30) 1 and glycerin bath solution 2 of dipotassium phosphate and/or potassium carbonate are thoroughly stirred and dissolved in mixing tank B, and left to stand in phase separator C to separate aqueous phase 4 and oil phase. 5
Separate into The azeotrope is removed from the oil phase 5 in the first distillation column, and the azeotrope is distilled under reduced pressure in the water evaporator A to remove water, and then the glycerin salt solution is circulated to the mixing tank B again.

〔Example〕

Hereinafter, the purification method of the present invention will be explained with reference to Examples and Comparative Examples. In the following description, % represents weight %.

Example Solution 1 consisting of 70% allyl alcohol and 50% water was initially added with 300 r of dipotassium phosphate (anhydrous).

After adding glycerin 900f and shaking well for 10 minutes,
When it was allowed to stand still, it separated into two phases. The upper layer (oil phase) had allyl alcohol as a main component, water content was 8.99%, and glycerin was 21.3%. The main component of the lower layer is a glycerin-water-salt solution, containing 51.2% glycerin and 22.0% salt.
% and allyl alcohol 10.6%. The oil phase was distilled using a precision distillation apparatus to obtain an azeotropic fraction containing 72.6% allyl alcohol and 27.7% water from the top of the column, and the bottom component was separated by vacuum distillation to obtain allyl alcohol. 5
4.6 t and 20.3 r of glycerin were obtained. This glycerin was added to the lower layer described above and distilled under reduced pressure to remove water. The glycerin bath solution of the remaining salt was reheated and added to a mixed solution of 70% allyl alcohol and 60% water, stirred for 10 minutes, and left to stand, resulting in separation into two phases.In the upper layer (oil phase) The moisture content was 8.90%.

The water content was analyzed by the Karl Fischer method, dipotassium phosphate was analyzed by neutralization titration, and glycerin and allyl alcohol were analyzed by gas chromatography.

Comparative Example The same operation as in Example was carried out except that ethylene glycol was used instead of glycerin. In the process of adding the phase-separated upper ethylene glycol phase to the lower aqueous phase and evaporating the water, dipotassium phosphate crystals were precipitated.

〔Effect of the invention〕

The present invention involves adding dipotassium phosphate and/or potassium carbonate and glycerin to an allyl alcohol aqueous solution, mixing and standing to separate the phases, distilling the allyl alcohol phase to recover high purity allyl alcohol and glycerin, and recovering the glycerin. This is an allyl alcohol purification method in which allyl alcohol is added to the aqueous phase, then distilled under reduced pressure to remove water, and the salts are recycled as a glycerin solution, and the salts are always present in the system as a solution in the form of a glycerin or water solution. Therefore, troubles associated with salt precipitation do not occur at all, and highly pure allyl alcohol can be advantageously produced industrially.

[Brief explanation of drawings]

FIG. 1 is a flowchart of an example of an industrial process using the purification method of the present invention. Code in the figure:

Claims (1)

[Claims] Dipotassium phosphate and/or potassium carbonate and glycerin are added to an allyl alcohol aqueous solution to separate it into an aqueous phase and an allyl alcohol phase, and the allyl alcohol phase is distilled to obtain high purity allyl alcohol and dissolve it. The recovered glycerin was added to the aqueous phase, and the water was removed by distillation.
A method for purifying allyl alcohol, which comprises circulating dipotassium phosphate and/or potassium carbonate as a glycerin solution.