JP2003064045A - Method of production for ethylene cyanhydrin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of production for ethylene cyanhydrin capable of obtaining the ethylene cyanhydrin including reduced amount of acrylamide in a method producing the ethylene cyanhydrin by reacting acrylonitrile and water. SOLUTION: This method of production for ethylene cyanhydrin comprises reacting acrylonitrile and water in an aqueous medium or the like in the presence of a catalyst and then polymerizing acrylamide included in the reaction mixture by a method using a polymerization initiator or the like to change it into a product easy to separate from the ethylene cyanhydrin.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing ethylene cyanohydrin, and more particularly to a method for producing ethylene cyanohydrin by hydrating acrylonitrile.

[0002]

BACKGROUND OF THE INVENTION Ethylene cyanohydrin is a compound useful as a raw material and an intermediate for many organic synthetic products such as pharmaceuticals, agricultural chemicals, and polymeric raw materials. Examples of the method for producing ethylene cyanohydrin include a method of reacting ethylene oxide with hydrocyanic acid (US Pat. No. 2,459,430).
Japanese Patent Application Laid-Open Publication No. JP-A-2003-264242 is known, and according to this method, ethylene cyanohydrin can be easily obtained in high yield.
However, since the hydrocyanic acid used as a starting material has strong toxicity and is difficult to handle, the method is not necessarily the best industrial production method. Therefore, a method of producing ethylene cyanohydrin by a hydration reaction of acrylonitrile using acrylonitrile, which is supplied as a synthetic fiber raw material in large quantities and at low cost, has been attempted. The hydration reaction of acrylonitrile is a method of reacting acrylonitrile with water in the presence of a catalyst. For example, an alkali metal hydroxide, a quaternary ammonium hydroxide or a tertiary amine is used as a catalyst for the reaction. There is known a method of reacting and a method of reacting with formaldehyde in the reaction system (US Pat. No. 3).
No. 024287, German Patent Publication No. 2655794
JP-A-59-210058, etc.).

[0003]

However, in the hydration reaction of acrylonitrile, acrylamide is produced as a by-product in addition to the intended product, ethylene cyanohydrin. Therefore, it is necessary to separate and purify ethylene cyanohydrin from the obtained reaction mixture. Distillation is considered as a method for this separation and purification, but when the present inventors performed distillation for the separation and purification of this ethylene cyanohydrin, it was difficult to separate ethylene cyanohydrin and acrylamide, and Ethylene cyanohydrin with a low content could not be obtained. An object of the present invention is to provide a method for producing ethylene cyanohydrin by reacting acrylonitrile with water, which is capable of obtaining ethylene cyanohydrin having a low acrylamide content. The present inventors have found that the above-mentioned problems can be solved by polymerizing the by-produced acrylamide and converting it into a polymer that can be easily separated from ethylene cyanohydrin, and completed the present invention.

[0004]

Means for Solving the Problem That is, the present invention is characterized in that acrylonitrile and water are reacted in the presence of a catalyst to polymerize acrylamide contained in the reaction mixture after completion of the reaction to produce ethylene cyanohydrin. It provides a method.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The hydration reaction for producing ethylene cyanohydrin from the acrylonitrile of the present invention can be carried out in the same manner as a conventionally known method.

The hydration reaction of acrylonitrile is usually carried out in an aqueous medium. Examples of the aqueous medium include water and mixed solvents of water-alcohol, water-dioxane, water-tetrahydrofuran, and the like. Industrially, only water is convenient and preferable. The amount of the aqueous medium with respect to the amount of acrylonitrile tends to improve as the amount increases, but from the viewpoint of productivity, 1 to 20 parts by weight is suitable for 1 part by weight of acrylonitrile.

A catalyst is used for the hydration reaction of acrylonitrile. Examples of the catalyst include basic catalysts, metals, solid acid catalysts and the like. Examples of the basic catalyst include organic bases and inorganic bases. Examples of the organic base include trimethylamine, triethylamine, tributylamine, triethanolamine, dimethylethanolamine, diethylethanolamine, 1,8-diazabicyclo [5.
4.0] Undec-7-cene, 1,5-diazabicyclo [4.3.0] non-5-ene, 1,4-diazabicyclo [2.2.2] octane, N, N-dimethylaniline, pyridine Tertiary amines such as bases and their derivatives, imidazole and its derivatives, Amberlite IRA-
Polymeric tertiary amines such as 400 (strongly basic ion exchange resin manufactured by Organo), and quaternary ammonium salts such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and the like. To be As an inorganic base,
Examples thereof include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkaline earth metal oxides such as magnesium oxide and calcium oxide. As a metal,
Examples include copper, silver, gold, cobalt, nickel, lanthanum, and cerium. Further, examples of the solid acid catalyst include zeolite, alumina and the like, and those in which the above metal is supported.

Usually, a basic catalyst, for example, a tertiary amine such as triethylamine, or an alkali metal hydroxide such as sodium hydroxide is preferably used because of its good yield and easy handling. The amount of the catalyst used is preferably 0.01 to 0.5 mol with respect to 1 mol of acrylonitrile.
Further, formaldehyde or a copolymer thereof may be allowed to coexist during the hydration reaction of acrylonitrile. The reaction temperature is usually 0 to 200 ° C, preferably 40 to 170 ° C in view of the reaction rate and the selectivity. The reaction is carried out under normal pressure, pressure,
It can be performed under reduced pressure. The reaction time varies depending on the reaction conditions such as reaction temperature and catalyst, but is usually 0.5
~ 20 hours, preferably 1-5 hours.

The hydration reaction of acrylonitrile can be carried out by stirring a mixture of acrylonitrile, a catalyst and an aqueous medium in the above proportions at the above temperature to produce ethylene cyanohydrin. Preferably, in order to suppress a rapid heat generation due to the reaction, the mixture is allowed to react with a mixture of acrylonitrile and an aqueous medium at the above temperature while stirring, and after completion of the catalyst addition, the reaction is aged for several hours to complete the reaction. .

As described above, in the hydration reaction of acrylonitrile, acrylamide is produced as a by-product together with ethylene cyanohydrin. The present invention is characterized in that the by-product acrylamide is polymerized to obtain ethylene cyanohydrin having a low acrylamide content.

The polymerization of acrylamide can be carried out by adding a polymerization initiator to the reaction mixture after completion of the hydration reaction of acrylonitrile, but an aqueous medium may be partially or partially added from the reaction mixture after completion of the hydration reaction. A method in which a polymerization initiator is added to the residue obtained by removing all of them to carry out is preferable. It is also possible to heat and polymerize without adding a polymerization initiator, but a method of adding a polymerization initiator is preferable in consideration of reactivity.

Examples of the polymerization initiator used for the polymerization of acrylamide include a compound which thermally decomposes to generate a free radical, a photopolymerization initiator and the like. It is also possible to use a redox catalyst that generates a free radical by the reaction of an oxidizing agent and a reducing agent. Examples of the compound which thermally decomposes to generate a free radical include hydrogen peroxide, dibenzoyl peroxide, dicumyl peroxide, dicyclohexyl peroxycarbonate, dilauryl peroxide, methyl ethyl ketone peroxide, acetylacetone peroxide, t-butyl hydroperoxide, and the like. Cumene hydroperoxide, bis (4-
t-butylcyclohexyl) peroxycarbonate,
t-Butyl perneodecanoate, t-amyl perpiperate, t-butyl perpiperate, t-butyl perneo hexanoate, t-butyl per-2-ethyl hexanoate, t-butyl perbenzoate, peroxoni Peroxides such as lithium sulfate, sodium peroxodisulfate, potassium peroxodisulfate, ammonium peroxodisulfate, azobisisobutyronitrile, 2,2'-
Azohis- (2-amidinopropane) dihydrochloride, 2-
(Carpamoylazo) isobutyronitrile and 4,4 '
-Azo compounds such as azopis (4-cyanovaleric acid). As the photopolymerization initiator, (4-alkoxyphenyl) phenyliodonium salt, tris (ethyl-3-)
Oxybutanoate) Aluminum and 4-chloro-2-
A combination of nitrobenzyl triphenylsilyl ether and the like can be mentioned.

When a redox catalyst is used as the polymerization initiator, examples of the oxidizing agent include the above-mentioned compounds that thermally decompose to generate free radicals. or,
Examples of the reducing agent used in combination with the oxidizing agent include salts of transition metals, specifically, iron sulfate (I
I), cobalt chloride (II) nickel sulfate (II), copper chloride (I), manganese acetate (II), vanadium acetate (III) and the like. Other suitable redox catalyst reducing agents include ascorbic acid, reducing sulfur compounds such as alkali metal and ammonium compound sulfites, bisulfites, thiosulfates, didithionates and tetrathionates, and the like. Or a reducing neighbor compound in which phosphorus has an oxidation state of 1 to 4, such as phosphoric acid and phosphite, and a nitrogen-containing compound such as aqueous ammonia, triethylamine, triethanolamine, triethylammonium chloride. Etc.

The amount of the polymerization initiator used is usually 0.001 to 10 mol, preferably 0.01 to 0.1 mol, per 1 mol of acrylamide. The amount of acrylamide in the reaction mixture can be quantified by analysis using gas chromatography or liquid chromatography.
Further, 0.01 mol% or more, preferably 0.05 to 0.5 mol% of a polymerization initiator may be added to 1 mol of acrylonitrile used for the hydration reaction. For acrylamide polymerization in the present invention, usual acrylamide polymerization conditions can be adopted. The reaction temperature of the polymerization is usually -20 to 150.
C., preferably 50 to 80.degree. The reaction time was 0.
It may be about 5 to 20 hours, but usually about 1 hour is sufficient.

From the reaction mixture after completion of acrylamide polymerization, for example, ethylene cyanohydrin having a low acrylamide content can be obtained by distillation. This distillation can be carried out by conventional distillation methods and conditions. For example, extraction with an organic solvent and distillation of the extract, direct vacuum distillation of the reaction solution, thin film distillation, etc. may be mentioned. It is preferable to remove the produced polymer solid matter by filtration or the like before the distillation because the operation becomes simple.

[0016]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 200 g (3.69 mol) of 98% by weight acrylonitrile and 1600 water in an autoclave equipped with a thermometer and a stirrer.
g (88.89 mol) and triethylamine 7.49 g
(0.074 mol) was charged and then sealed. Stir the contents of the autoclave from room temperature to 120 ° C.
The temperature was raised over 5 hours, then to 150 ° C. over 2.5 hours, and the mixture was aged at the same temperature for 1.5 hours. afterwards,
A part of the obtained reaction liquid was collected and analyzed by gas chromatography. As a result, the reaction liquid was 162.6 g (2.29 mol) of ethylene cyanohydrin and 19.
It contained 7 g (0.277 mol). From the obtained reaction liquid, 60 ° C., 0.67 to 4.00 kPa (5 to 30 mm
Hg) water was distilled off under reduced pressure, the residue was cooled to room temperature, and then 0.45 g of azobisisobutyronitrile
(0.0028 mol) was added. While stirring the obtained mixture, the temperature was raised to 80 ° C. over 1 hour, and the mixture was heated to the same temperature for 1 hour.
Hold for time to complete reaction. After completion of the reaction, the reaction mixture was filtered to remove insoluble materials, and a part of the filtrate was collected and analyzed by gas chromatography. As a result, the filtrate contained 162 g (2.29 mol) of ethylene cyanohydrin. Was there. No acrylamide was present in the filtrate. The obtained filtrate was heated at 120 ° C. and 1.07 kPa (8
Distillation by thin-film distillation under reduced pressure (mmHg) to give acrylamide-free ethylene cyanohydrin 158.
8 g (2.23 mol) could be obtained.

Comparative Example 1 After the hydration reaction was carried out in the same manner as in Example 1, water was distilled off from the resulting reaction solution, and the residue was treated in the same manner as in Example 1 without carrying out a polymerization reaction. After distillation, a distillate containing 159.3 g (2.24 mol) of ethylene cyanohydrin and 10.0 g (0.14 mol) of acrylamide was obtained.

[0019]

EFFECT OF THE INVENTION According to the method of the present invention, acrylamide produced as a by-product in the hydration reaction of acrylonitrile can be converted into a polymer which can be easily separated from ethylene cyanohydrin. As a result, ethylene cyanide having a low acrylamide content can be obtained. Hydrin can be obtained.

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Claims (4)

[Claims] 1. A method for producing ethylene cyanohydrin, which comprises reacting acrylonitrile with water in the presence of a catalyst to polymerize acrylamide contained in the reaction mixture after the reaction. 2. The method for producing ethylene cyanohydrin according to claim 1, wherein the polymerization of acrylamide is carried out by adding a polymerization initiator. 3. The method for producing ethylene cyanohydrin according to claim 1, wherein the reaction between acrylonitrile and water is carried out in an aqueous medium. 4. After completion of the reaction between acrylonitrile and water,
The method for producing ethylene cyanohydrin according to claim 3, wherein the acrylamide is polymerized by adding a polymerization initiator after removing the aqueous medium from the reaction mixture.