WO2018070166A1 - Production method for cyanohydrin-containing liquid and production device for cyanohydrin-containing liquid - Google Patents

Abstract

The purpose of the present invention is to provide: a method that makes it possible to easily produce a cyanohydrin-containing liquid that contains few reaction raw materials or other impurities; and a device that is suited to the method. This production method for a cyanohydrin-containing liquid includes steps 1–4. Step 1: A step for reacting a raw material carbonyl compound and a raw material cyanating agent to obtain a reaction liquid that includes a cyanohydrin. Step 2: A purification step for supplying the reaction liquid obtained in step 1 to a distillation device and distilling the reaction liquid. Step 3: A step for measuring: the molar concentration of carbonyl compounds in a liquid in the distillation device and/or the molar concentration of cyanating agents in the liquid in the distillation device; and the molar concentration of cyanohydrins in the liquid in the distillation device. Step 4: A step for controlling the purification step on the basis of the results of the abovementioned measurements.

Description

Method for producing cyanohydrin-containing liquid and cyanohydrin-containing liquid production apparatus

The present invention relates to a method for producing a cyanohydrin-containing liquid and an apparatus for producing a cyanohydrin-containing liquid.

Cyanohydrin is industrially important as a raw material for carboxylic acids, amino acids, hydroxy esters and the like.
As a method for producing such cyanohydrin, for example, methods described in Patent Documents 1 and 2 are disclosed.

International Publication No. 2009/054355 International Publication No. 2009/054356

As described above, cyanohydrin is useful as a raw material for carboxylic acids, amino acids, hydroxyesters, and the like. In recent years, these carboxylic acids and the like are used for food and drink materials. For example, lactonitrile, which is one of cyanohydrins, is useful as a raw material for producing lactic acid and the like, and the lactic acid and the like are used for food and drink materials and the like.

In recent years, this food / beverage material and the like have been required to have an extremely low impurity content such as a reaction raw material, and the cyanohydrin-containing liquid that is the raw material is also required to have an extremely low impurity content.

However, the conventional method for producing a cyanohydrin-containing liquid cannot easily obtain a cyanohydrin-containing liquid having a low impurity content.
Therefore, an object of the present invention is to provide a method capable of easily producing a cyanohydrin-containing liquid having a low impurity content such as a reaction raw material and an apparatus suitable for the method.

As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by using the results of measuring the molar concentration of each component in the distillation apparatus for the condition control of the purification process. The invention has been completed.
The present invention relates to the following [1] to [13], for example.

[1] A method for producing a cyanohydrin-containing liquid, comprising the following steps 1 to 4.
Step 1: A step of obtaining a reaction liquid containing cyanohydrin by reacting a raw material carbonyl compound and a raw material cyanating agent. Step 2: A purification step of supplying the reaction liquid obtained in Step 1 to a distillation apparatus and distilling the reaction liquid. Step 3: Measuring at least one of the molar concentration of the carbonyl compound and the molar concentration of the cyanating agent and the molar concentration of cyanohydrin contained in the liquid in the distillation apparatus. Step 4: Purification based on the measurement result. Process control process

[2] The production method according to [1], wherein the purification step is controlled in step 4 so that the content of the carbonyl compound and the cyanating agent in the liquid in the distillation apparatus is 1000 ppm by mass or less, respectively.

[3] The production method according to [1] or [2], wherein the purification step is controlled in step 4 so that the concentration of cyanohydrin in the liquid in the distillation apparatus is 5 to 100% by mass.

[4] The production method according to any one of [1] to [3], wherein in the step 4, the method for controlling the purification step is to change a distillation temperature.

[5] The production method according to any one of [1] to [4], wherein the distillation temperature in Step 2 is 20 to 60 ° C.

[6] The production method according to any one of [1] to [5], wherein in step 2, the reaction solution is continuously supplied to a distillation apparatus.

[7] The manufacturing method according to any one of [1] to [6], wherein the measurement is performed in the distillation apparatus or on a flow path branched from the distillation apparatus.

[8] The manufacturing method according to any one of [1] to [7], wherein the measurement is automatic measurement.

[9] The production method according to any one of [1] to [8], wherein the molar concentration is measured using at least one selected from an ultraviolet absorptiometer and a refractometer.

[10] The production method according to any one of [1] to [9], wherein the raw material carbonyl compound is a compound represented by the formula (A).
R ¹ COR ² ... Formula (A)
In the formula (A), R ¹ and R ² are each independently a hydrogen atom, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, a heterocyclic group, or a part of these groups It is a group substituted with a substituent.

[11] The production method according to any one of [1] to [10], wherein the raw material carbonyl compound is acetaldehyde having a content of a component having a boiling point of 25 ° C. or higher at normal pressure of 300 mass ppm or less.

[12] The production method according to any one of [1] to [11], wherein the raw material cyanating agent is a compound represented by the formula (B).
M (CN) _n ... Formula (B)
In the formula (B), M is a hydrogen atom, an alkali metal, an alkaline earth metal, iron, copper, or zinc, and n is a valence of M.

[13] A supply unit for supplying the raw material carbonyl compound and the raw material cyanating agent;
A reactor for reacting the supplied raw material to obtain a reaction liquid containing cyanohydrin;
A distillation apparatus for distilling the reaction solution obtained in the reactor;
At least one of the molar concentration of the carbonyl compound and the molar concentration of the cyanating agent contained in the liquid in the distillation apparatus provided in the distillation apparatus or on the flow path branched from the distillation apparatus, and cyanohydrin An apparatus for producing a cyanohydrin-containing liquid, comprising a measuring instrument for measuring a molar concentration.

According to the present invention, it is possible to easily obtain a cyanohydrin-containing liquid having a low impurity content such as a reaction raw material without lowering productivity, and to easily produce a cyanohydrin-containing liquid having a desired concentration.
In particular, even when the reaction solution is continuously supplied to a distillation apparatus, a cyanohydrin-containing solution having a desired concentration and a low impurity content can be stably produced for a long period of time.

≪Method for producing cyanohydrin-containing liquid≫
The method for producing a cyanohydrin-containing liquid according to the present invention (hereinafter also referred to as “the present method”) includes the following steps 1 to 4.
Step 1: A step of obtaining a reaction liquid containing cyanohydrin by reacting a raw material carbonyl compound and a raw material cyanating agent. Step 2: A purification step of supplying the reaction liquid obtained in Step 1 to a distillation apparatus and distilling the reaction liquid. Step 3: Measuring at least one of the molar concentration of the carbonyl compound and the molar concentration of the cyanating agent and the molar concentration of cyanohydrin contained in the liquid in the distillation apparatus. Step 4: Purification based on the measurement result. Process control process

The present inventor tried various methods such as control of the impurity content of the reaction raw material, control of reaction, control of purification conditions, etc. in an attempt to produce a cyanohydrin-containing liquid having a low impurity content, but the cyanohydrin having a sufficiently low impurity content. The containing liquid could not be produced.

In the method of simply setting the distillation conditions and keeping them constant, for example, when the reaction solution is continuously supplied to the distillation apparatus, which is adopted from the viewpoint of productivity, etc., a cyanohydrin-containing solution with a low impurity content is stably used. I can't get it.

As a result of intensive studies by the present inventor, cyanohydrin with high productivity and low content of impurities such as reaction raw materials is obtained only by grasping the state of the liquid in the distillation apparatus and controlling the purification process based on the grasped state. It was found that the contained liquid can be easily obtained, and further, a cyanohydrin-containing liquid having a desired concentration can be easily produced.

In the present invention, the term “impurity” refers to components other than cyanohydrin and components such as a pH adjuster added for stabilization of cyanohydrin and cyanohydrin-containing liquids. A carbonyl compound and a cyanating agent which are reaction raw materials.

<Step 1>
Step 1 is a step in which a raw material carbonyl compound and a raw material cyanating agent are reacted to obtain a reaction liquid containing cyanohydrin.

[Raw material carbonyl compound]
The raw material carbonyl compound is not particularly limited as long as it is a compound having a carbonyl group.
As the raw material carbonyl compound, two or more kinds may be used, but it is preferable to use one kind alone because of easy concentration measurement and purification.

The raw material carbonyl compound is preferably a compound represented by the following formula (A).
R ¹ COR ² ... Formula (A)
In the formula (A), R ¹ and R ² are each independently a hydrogen atom, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, a heterocyclic group, or a part of these groups It is a group substituted with a substituent.
The aliphatic hydrocarbon group preferably has 1 to 30 carbon atoms.
The alicyclic hydrocarbon group preferably has 3 to 30 carbon atoms.
The aromatic hydrocarbon group preferably has 6 to 30 carbon atoms.
The heterocyclic group preferably has 2 to 30 carbon atoms.

The heterocyclic group represents a group having a ring formed containing a heteroatom such as nitrogen, oxygen, or sulfur. In the present specification, an aromatic heterocyclic group is an aromatic carbonization. It is not a hydrogen group but a heterocyclic group.

Examples of the substituent include an alkyl group, allyl group, hydroxy group, carbonyl group, carboxyl group, alkoxycarbonyl group, alkoxy group, fluoro group, chloro group, bromo group, iodo group, cyano group, amino group, and alkylamino. Group, carbamoyl group, alkylcarbamoyl group, imino group, N-oxide group, N-hydroxy group, diazo group, azido group, nitro group, nitroso group, sulfo group, mercapto group, alkylthio group.
The group substituted with the substituent may have one substituent or two or more.

R ¹ and R ² are each a hydrogen atom, an aliphatic hydrocarbon group having 1 to 6 carbon atoms, or the like because the effect of the present method is more easily exhibited and the reactivity with a raw material cyanating agent is excellent. An aromatic hydrocarbon group having 6 to 14 carbon atoms is preferable, a hydrogen atom or an alkyl group having 1 to 6 carbon atoms is more preferable, a hydrogen atom or an alkyl group having 1 to 3 carbon atoms is more preferable, and R ¹ is a hydrogen atom. And R ² is particularly preferably an alkyl group having 1 to 3 carbon atoms.
As the raw material carbonyl compound, a compound in which R ¹ or R ² is a hydrogen atom, that is, an aldehyde is preferable, and acetaldehyde is most preferable.

Examples of the raw material carbonyl compound include saturated alkyl aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde; unsaturated aldehydes such as acryl aldehyde and methacrylamide; aromatic aldehydes such as benzaldehyde, phenylacetaldehyde, naphthaldehyde, and phthalaldehyde. A heterocyclic group-containing aldehyde such as nicotine aldehyde; acetone, 2-butanone, 2-pentanone, 3-methyl-2-butanone, 3-pentanone, 3-hexanone, 2-methyl-3-pentanone, 3-heptanone, 2 -Methyl-3-hexanone, 2,4-dimethyl-3-pentanone, acetophenone, 2-nonanone, 2-octanone, 2-heptanone, 2-hexanone, 4-methyl-2-pentanone, 4 Heptanone, cyclohexanone, ketones, such as 2,6-dimethyl-4-heptanone.

The raw material carbonyl compound is not particularly limited and may be a compound that can be obtained for industrial use, research use, etc., but it is preferable to use a purified carbonyl compound obtained by purifying such raw material carbonyl compound.

By using the purified carbonyl compound, the amount of an impurity (hereinafter also referred to as “specific impurity B”) having a boiling point at normal pressure higher than that of the carbonyl compound derived from the carbonyl compound can be reduced. . Specific impurities B include, for example, oligomers such as dimers, trimers, and tetramers of carbonyl compounds. In addition, when using 2 or more types of carbonyl compounds as a raw material carbonyl compound, the said specific impurity B has a boiling point in a normal pressure higher than the carbonyl compound in which the boiling point in a normal pressure is the lowest among the used carbonyl compounds. Means a component other than the carbonyl compound.
If the specific impurity B is small, it is not necessary to distill the reaction solution at a high temperature to remove the specific impurity B in the following step 2. Since cyanohydrin has the property of decomposing at high temperature, the reaction liquid does not require distillation at high temperature, making it difficult for cyanohydrin to decompose, and easily producing high yield and low impurity content cyanohydrin-containing liquid. Can be obtained by sex.

When the raw material carbonyl compound is acetaldehyde, examples of the specific impurity B include components having a boiling point of 25 ° C. or higher at normal pressure (hereinafter also referred to as “specific impurity A”). The amount of the specific impurity A contained in the raw material acetaldehyde can be determined by the following method.

The raw material acetaldehyde is supplied to a glass flask equipped with a stirrer, a distillation tower, and a distiller, and simple distillation is performed at normal pressure. The flask is heated while observing the temperature in the gas phase part of the distillation tower, and when the temperature in the gas phase part has just reached 25 ° C., the heating is stopped and the simple distillation is completed. After simple distillation, the residue remaining in the flask is weighed, and the mass ppm relative to the total amount of raw material acetaldehyde supplied is determined.

The content of the specific impurity A contained in the raw material acetaldehyde is preferably 300 ppm by mass or less, more preferably 250 ppm by mass or less, and further preferably 200 ppm by mass or less.

In addition, about content of the specific impurity B contained in a raw material carbonyl compound, it was specific impurity A except having stopped heating when the temperature of the gaseous-phase part just reached the boiling point in the normal pressure of the carbonyl compound used for the raw material. The content of the specific impurity B contained in the raw material carbonyl compound is preferably 300 ppm by mass or less, more preferably 250 ppm by mass or less, and further preferably 200 ppm by mass or less.

The content of the specific impurity B or the specific impurity A can be measured by the above method, but may be below the detection limit when measured by the method. The content of the specific impurity B or the specific impurity A can be within the above range by purifying the raw material carbonyl compound, but is not necessarily purified if the content of the unpurified raw material carbonyl compound is within the above range. do not have to.

Since the content of the specific impurity B or the specific impurity A is preferably as small as possible, the lower limit of the range is not particularly limited. However, if a numerical value is given, for example, the specific impurity B or A is preferably used. The lower limit of the content of is 0.1 mass ppm.
By using a raw material carbonyl compound in which the content of the specific impurity B or the specific impurity A is in the above range, a cyanohydrin-containing liquid having a low impurity content can be easily obtained with high economic efficiency and high performance without purification at a high temperature. It can be obtained with productivity.

The method for obtaining the purified carbonyl compound is not particularly limited, and a conventionally known method can be adopted. However, from the viewpoint that a purified carbonyl compound can be easily obtained by a simple method, the starting carbonyl compound is used. A distillation method is preferred.

A specific impurity B or A tends to occur in the carbonyl compound. Research by the present inventors has revealed that the generation of the specific impurity is promoted particularly when contacted with an iron member. For this reason, the raw material carbonyl compound can be easily obtained from a cyanohydrin-containing liquid with higher yield and purity, and the effect of using the carbonyl compound with a small content of the specific impurity can be exhibited more efficiently. The purified carbonyl compound obtained in the step of purifying the product is preferably reacted with the raw material cyanating agent without contacting with the iron member.
The iron member means an iron or steel member (pipe, device, etc.) and does not include a member made of an iron alloy such as SUS.

[Raw material cyanating agent]
As the raw material cyanide agent is not particularly limited as long as the material capable of introducing a cyano group into a carbonyl compound, and ionized in liquid CN ^- is preferably a compound which produces a.
Two or more kinds of the raw material cyanating agent may be used, but it is preferable to use one kind alone for ease of concentration measurement and purification.

The raw material cyanating agent is preferably a compound represented by the following formula (B).
M (CN) _n ... Formula (B)
In the formula (B), M is a hydrogen atom, an alkali metal, an alkaline earth metal, iron, copper, or zinc, and n is a valence of M. n is usually an integer of 1 to 3, preferably 1 or 2.

Examples of the alkali metal include lithium, sodium, potassium, rubidium, and cesium. Examples of the alkaline earth metal include magnesium, calcium, strontium, and barium.

Specific examples of the raw material cyanating agent include HCN, LiCN, NaCN, KCN, RbCN, CsCN, Mg (CN) ₂ , Ca (CN) ₂ , Sr (CN) ₂ , Ba (CN) ₂ , Fe (CN) ₂ , Fe (CN) ₃ , CuCN, Cu (CN) ₂ , Zn (CN) _2, etc., among these, making pH control of the reaction liquid easier and by-product of salt. Hydrogen cyanide (HCN) is preferable because it can be suppressed.

The raw material cyanating agent is not particularly limited, and may be a compound that can be obtained for industrial use, research use, and the like. Specifically, in the case of hydrogen cyanide, hydrogen cyanide by-produced by an ammoxidation reaction or the like can be used, and methane or the like can be produced from a raw material. It is also possible to produce sodium cyanide by reacting with a strong acid such as sulfuric acid. Industrially, it is preferable to use hydrogen cyanide by-produced in the production of (meth) acrylonitrile.

The raw material cyanating agent may be a purified cyanating agent purified in advance by distillation, adsorption or the like.
For the purpose of obtaining a higher purity cyanohydrin-containing liquid, a purified cyanating agent may be used. However, since a high boiling point compound is generally not present in the cyanating agent, it is an impure component in the raw material cyanating agent. Can be removed in the purification step of Step 2 below.

[Reaction of raw material carbonyl compound and raw material cyanating agent]
The reaction of the raw material carbonyl compound and the raw material cyanating agent can be exemplified by the following reaction formula.
M (CN) _n + nHX → nHCN + MX _n
nR ¹ COR ² + nHCN → nR ¹ R ² C (OH) (CN)
Here, HX is an acid or water, and M, n, R ¹ and R ² are as described above.
By reacting the raw material carbonyl compound and the raw material cyanating agent, a reaction liquid containing cyanohydrin is obtained. As the cyanohydrin, α-cyanohydrin is preferable, and lactonitrile is particularly preferable.

The amount of the raw material carbonyl compound and the raw material cyanating agent supplied to the reactor is determined by the molar ratio of the raw material carbonyl compound and the cyano group of the raw material cyanating agent (raw material carbonyl compound / cyano group of the cyanating agent). Usually, it is 0.50 to 2.0, preferably 0.70 to 1.5. When the molar ratio is less than or equal to the upper limit of the molar ratio, it is not necessary to recover excess raw material carbonyl compound, and side reactions due to the raw material carbonyl compound are less likely to occur. Moreover, it is not necessary to collect | recover excess raw material cyanating agents as it is more than the minimum of the said molar ratio. From the viewpoint of the conversion rate of the raw material, the molar ratio of the raw material carbonyl compound and the cyano group of the raw material cyanating agent is preferably closer to 1, more specifically 0.95 to 1.05. However, the closer the molar ratio of the raw material carbonyl compound to the cyano group of the raw material cyanating agent is to 1, the smaller the unintended change in the supply amount, and the raw material carbonyl compound supplied to the reactor and the raw material cyanide It will change which one is excessive. When the raw material carbonyl compound is excessive, it is necessary to recover the raw material carbonyl compound, and when the raw material cyanating agent is excessive, it is necessary to recover the raw material cyanating agent. When the molar ratio of the cyano group to which N is close to 1, which is excessive is not stable, an equipment capable of recovering both is required. For this reason, it is also preferable to supply one raw material slightly in advance. Specifically, the molar ratio between the raw material carbonyl compound and the cyano group of the raw material cyanating agent is particularly preferably from 1.001 to 1.10. Further, it is particularly preferable that the molar ratio of the cyano group of the raw material cyanating agent to the raw material carbonyl compound is 1.001 to 1.10. Thus, it is preferable to provide an equipment for recovering the excess component by making one of the raw materials excessive, and the manufacturing apparatus can be simplified.

The reaction is preferably carried out in the presence of one or more catalysts.
The catalyst is not particularly limited as long as the reaction can be promoted, and examples thereof include organic or inorganic basic compounds. Specific examples include amine compounds, quaternary ammonium salts, alkali metal compounds, alkaline earths. And basic compounds such as metal compounds and metal alkoxides.
The catalyst is preferably used in such an amount that the pH of the reaction solution falls within the following range from the viewpoint that the reaction proceeds efficiently.

The reaction is preferably performed in the presence of a solvent. As the solvent, one kind or two or more kinds of solvents can be used. As the solvent, either water or an organic solvent can be used. Examples of the organic solvent include alcohol, carboxylic acid, ester and the like. As the solvent, it is preferable to use water that can easily adjust the concentration of the cyanohydrin-containing liquid after the reaction and is excellent in terms of cost.
The solvent is used in such an amount that the amount of the solvent in the reaction solution is 5 to 95% by mass because the reaction proceeds efficiently and a cyanohydrin-containing solution having a desired concentration can be easily obtained. preferable.

When the raw material carbonyl compound and the raw material cyanating agent are solid at the temperature during use, the raw material carbonyl compound and the raw material cyanating agent are dissolved or suspended in a solvent inert to the reaction, preferably water. It is preferable to use in a turbid state.

The reaction temperature of the reaction is not particularly limited as long as the raw material compound is reacted. Specifically, the reaction temperature is preferably 0 to 40 ° C. from the viewpoint that the reaction is efficiently performed and the generated cyanohydrin is hardly decomposed. More preferably, it is 10 to 30 ° C.

The pH conditions for the reaction are preferably pH 3-7, more preferably pH 4-6.
It is preferable to perform the reaction in the above pH range because a cyanohydrin-containing liquid can be obtained at a high productivity, and a cyanohydrin-containing liquid can be obtained with high productivity, and the generated cyanohydrin is hardly decomposed.

In order to make the pH range, a basic compound or an acidic compound may be used as necessary. In particular, when a material other than hydrogen cyanide is used as the raw material cyanating agent, it is preferable to use an acid for the purpose of adjusting the pH to the above range because the pH of the reaction solution becomes high. As the acid, acids such as sulfuric acid, hydrochloric acid, phosphoric acid and acetic acid can be used.

The reaction can be carried out by any of batch, semi-batch and continuous methods, preferably semi-batch or continuous, more preferably continuous.
The average residence time in the reaction is not particularly limited as long as the raw material carbonyl compound and the raw material cyanating agent can sufficiently react. Usually, the reaction time is 0.1 to 24 hours, preferably 0.5 to 12 hours. More preferably, it is 1 to 6 hours.

In the reaction, it is preferable to measure at least one concentration selected from the group consisting of a carbonyl compound, a cyanating agent and a cyanohydrin in the reactor. It is more preferable to measure at least one of the molar concentrations as well as the molar concentration of cyanohydrin.

In particular, when at least one of the raw material carbonyl compound and the raw material cyanating agent is continuously supplied to the reactor, based on the measurement result, at least one of the raw material carbonyl compound and the raw material cyanating agent supplied to the reactor. It is preferred to control the amount. This is preferable because the reaction between the raw material carbonyl compound and the raw material cyanating agent is efficiently performed, and the amount of unreacted components removed in step 2 is reduced.

(Reaction solution)
The reaction solution obtained by the above reaction may be supplied to the distillation apparatus as it is, but sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, etc. from the viewpoint of suppressing the decomposition of cyanohydrin and stabilizing cyanohydrin. It is preferable to mix the pH adjuster. Two or more kinds of pH adjusting agents may be used.
The blending amount of the pH adjuster is such that the pH of the resulting reaction solution is preferably 0.0 to 5.0, more preferably 0.5 to 3.0.

<Process 2>
Step 2 is a purification step in which the reaction solution obtained in Step 1 is supplied to a distillation apparatus and the reaction solution is distilled.
The supply method to the distillation apparatus is not particularly limited and may be supplied intermittently, but it is preferable to supply continuously from the viewpoint of productivity and the like.
In addition, the reaction solution can be continuously produced because the effect of the present method can be further exerted, and a cyanohydrin-containing solution having a desired concentration with a small impurity content, which was not possible with the conventional method, can be easily and stably produced over a long period of time. It is preferable to supply to a distillation apparatus.

The distillation method is not particularly limited as long as it can be industrially implemented. Specific methods include simple distillation, precision distillation, thin-film distillation, and the like. In precision distillation, a method using a plate tower or a packed tower, or the like can be given. Examples of the method using a packed tower include a method using regular packing or irregular packing. The distillation can be carried out by any of batch, semi-batch and continuous methods, but a semi-batch or continuous method is preferred.

The conditions for the distillation are not particularly limited. However, when acetaldehyde is used as the starting carbonyl compound and hydrogen cyanide is used as the starting cyanating agent to obtain lactonitrile, the distillation temperature is preferably 20 It is ˜60 ° C., more preferably 30 ° -50 ° C., and the distillation time (residence time) is preferably 1 to 300 minutes, more preferably 5 to 150 minutes. Although the distillation pressure is determined by the relationship with the distillation temperature, the distillation temperature is preferably 0.1 to 400 KPaA, more preferably 1 to 200 KPaA.

By distilling the reaction liquid at the above temperature, impurities such as reaction raw materials in the reaction liquid can be reduced, and a cyanohydrin-containing liquid having a high yield and a low impurity content can be easily obtained with high productivity. . In particular, by using the purified carbonyl compound as a raw material carbonyl compound, the effect of purifying the reaction solution at the temperature is more exhibited.

Further, in order to further reduce the impurity content in the cyanohydrin-containing liquid, it is preferable to perform reflux. The reflux ratio when refluxing is preferably 0.1 to 20, more preferably 1 to 10. When the reflux ratio is within the above range, the separation rate of each component such as a carbonyl compound, a cyanating agent, cyanohydrin, and a solvent can be improved without significantly reducing production efficiency.

The distillation is usually performed in a distillation apparatus. At this time, since the raw material carbonyl compound and the raw material cyanating agent tend to have a lower boiling point than the cyanohydrin-containing liquid, the target cyanohydrin-containing liquid tends to accumulate at the bottom of the apparatus.
The distillation preferably includes a step of extracting the cyanohydrin-containing liquid from the bottom of the distillation apparatus from the viewpoint that the distillation conditions can be controlled more easily.

<Step 3>
Step 3 is a step of measuring at least one of the molar concentration of the carbonyl compound and the molar concentration of the cyanating agent and the molar concentration of cyanohydrin contained in the liquid in the distillation apparatus. Although the molar concentration of both the carbonyl compound and the cyanating agent may be measured, when one of the raw material carbonyl compound or the raw material cyanating agent is used in an excess amount during the reaction, One molar concentration used in the quantity is measured. The liquid in the distillation apparatus usually means a cyanohydrin-containing liquid present at the bottom of the distillation apparatus.

In this method, in this step 3, the molar concentration of the component in the actual liquid in the distillation apparatus is grasped, and the molar concentration of at least two kinds of components is grasped instead of one kind of ingredient, and the grasping thereof. The following step 4 is performed based on the situation, and the above-described effect is exhibited only by performing these steps.

In addition, by measuring the molar concentration of cyanohydrin, the actual situation of the liquid in the distillation device, specifically, the temperature of the liquid in the distillation device can be determined from the comparison between the measured cyanohydrin concentration and the expected value. It is possible to evaluate the situation of the control temperature and the like.

The measuring device that performs the measurement is not particularly limited as long as it is a device that can measure each of the components, and specific examples include an ultraviolet absorptiometer, a cyan meter, and a refractometer.
In Step 1, when the raw material carbonyl compound is used in an excess amount and reacted with the raw material cyanating agent, it is preferable to use at least one selected from an ultraviolet absorptiometer and a refractometer as the measuring instrument. On the contrary, in Step 1, when the raw material cyanating agent is used in an excess amount and reacted with the raw material carbonyl compound, it is preferable to use at least one selected from a cyan meter and a refractometer as the measuring device. .

As the measuring instrument, it is more preferable to use an ultraviolet absorptiometer and a refractometer, or a cyan meter and a refractometer in combination. That is, for example, it is preferable to use at least one selected from an ultraviolet absorptiometer and a cyan meter, and further to use a refractometer.

From the viewpoint of ease of measurement, the carbonyl compound is first measured with an ultraviolet absorptiometer, and the total molar concentration of the carbonyl compound and cyanohydrin is measured with a refractometer, and the mole of the carbonyl compound thus obtained is measured. A method of calculating the molar concentration of cyanohydrin from the concentration and the total molar concentration of the carbonyl compound and cyanohydrin is preferable.

Further, the molar concentration of the cyanating agent was measured with a cyan meter, and the total molar concentration of the cyanating agent and cyanohydrin was further measured with a refractometer, and the molar concentration of the cyanating agent thus obtained was compared with the cyanide agent. A method of calculating the molar concentration of cyanohydrin from the total molar concentration of the agent and cyanohydrin is preferred.

The measurement may be performed anywhere as long as the state of the liquid in the distillation apparatus can be grasped, but is preferably performed in the distillation apparatus or on a flow path branched from the distillation apparatus. In view of the point and the simplification of the apparatus, it is more preferable to perform the process on a flow path branched from the distillation apparatus.
When the measurement is performed on the flow path branched from the distillation apparatus, the liquid after the measurement may be flowed into the distillation apparatus again or taken out from the distillation apparatus.

The measurement is preferably performed near the outlet (extraction port) of the cyanohydrin-containing liquid in the distillation apparatus. That is, when measuring in the distillation apparatus, it is preferable that a measuring instrument is installed near the outlet of the cyanohydrin-containing liquid of the distillation apparatus, and when measuring on the flow path branched from the distillation apparatus, The flow path is preferably branched from the vicinity of the outlet of the cyanohydrin-containing liquid of the distillation apparatus.
The measurement is preferably performed near the outlet of the cyanohydrin-containing liquid in the distillation apparatus, so that the molar concentration of the liquid after sufficient purification can be measured, and the suitability of the distillation conditions can be more accurately determined. .

The measurement is preferably automatic measurement.
Here, “automatic measurement” means that the device is actively operated without any human intervention during the measurement. Specifically, the liquid to be measured is automatically sampled. Automatic sampling, automatic detection for automatically detecting the absorbance or refractive index of the liquid being measured, or automatic calculation for automatically calculating the molar concentration of each component in the liquid being measured It means to include either.

The automatic measurement preferably includes two of these automatic sampling, automatic detection and automatic calculation, and more preferably includes all.
By making the measurement automatic, a cyanohydrin-containing liquid with a low impurity content can be obtained easily and stably with high productivity.

Specifically, the automatic sampling includes feeding and collecting a liquid to be measured in a measuring instrument or a measurement place without performing an artificial operation, and more specifically, the distillation apparatus. The liquid is fed and collected via a flow path branched from the flow path, a flow path for sending liquid from the distillation apparatus to the measuring instrument, or a flow path for circulating the liquid to be measured between the distillation apparatus and the detector. Can be mentioned.

The automatic detection is to perform detection of a liquid to be measured without an artificial operation. Specifically, when the detector is an ultraviolet absorptiometer, a certain wavelength is automatically detected. And detecting the absorbance of the liquid, and when the detector is a refractometer, automatically irradiating the light to detect the refractive index of the liquid.
The automatic detection may be a continuous type that continues to be detected continuously, or may be an intermittent type that automatically starts detection every certain time.

The automatic calculation specifically refers to deriving the molar concentration of each component in the liquid, which is the object to be measured, from the detected data without going through an artificial operation. For example, the molar concentration is automatically calculated by performing an operation based on a preset arithmetic expression using the absorbance or refractive index obtained by an absorptiometer or a refractometer.

It is preferable that the measuring instrument further has an automatic recording function or the like.
The automatic recording function is a function for recording detected data, post-computation data, detection conditions, and the like. The recording may be in the form of printing on paper or the like, or in the form of recording as electronic data on a storage medium such as HDD (Hard Disk Drive), SSD (Solid State Drive), CD, DVD, etc., a storage medium installed inside the apparatus, etc. Good.

<Step 4>
Step 4 is a step of controlling the purification step based on the measurement result of the molar concentration of each component obtained in Step 3.
Usually, when performing distillation, conditions such as distillation temperature are set and adjusted after seeing the state of the product. However, with this adjustment alone, a cyanohydrin-containing liquid with a sufficiently low impurity content cannot be easily obtained. . For this reason, the present invention has been made, and this step 4 is preferably a step in which the distillation temperature and the like are adjusted and adjusted in accordance with the state of the actual liquid in the distillation apparatus.
By performing the control, a cyanohydrin-containing liquid with a small impurity content can be easily obtained with high productivity, and the concentration of the cyanohydrin-containing liquid can be adjusted.

The control factor of step 4 includes controlling at least one factor selected from distillation temperature, distillation pressure and reflux ratio, and at least one selected from distillation temperature and distillation pressure for ease of control. It is preferable to control the factor, and it is more preferable to control the distillation temperature.
As a specific example of control, in general, a carbonyl compound and a cyanating agent have a boiling point lower than that of cyanohydrin. Therefore, the carbonyl compound and cyanide in a liquid containing the cyanohydrin-containing liquid in the distillation apparatus measured in step 3 are used. When at least one molar concentration selected from the agent is higher than the upper limit value described later, it is preferable to perform at least one control selected from a control for increasing the distillation temperature and a control for decreasing the distillation pressure. . Thereby, the molar concentration of at least one selected from the carbonyl compound and the cyanating agent in the distillation apparatus can be lowered.

In step 4, the purification step is performed so that the content of the carbonyl compound and the cyanating agent in the liquid measured in step 3 is preferably 1000 ppm by mass or less, more preferably 500 ppm by mass or less. It is preferable to control.
Note that the content of the carbonyl compound and the cyanating agent is preferably as small as possible, and it is preferable that they are not present. Therefore, the lower limit of the range is not particularly limited. , Each of which is 0.1 mass ppm.

In step 4, the concentration of cyanohydrin in the liquid in the distillation apparatus measured in step 3 is preferably 5 to 100% by mass, more preferably 10 to 100% by mass, and even more preferably 50 to 100% by mass. Thus, it is preferable to control the purification process.

In the step 4, it is preferable to automatically control the purification step without intervention of an artificial operation from the viewpoint that a cyanohydrin-containing liquid can be obtained with high productivity. Specifically, automatic control adjusts distillation conditions based on the detected data, post-computation data, post-recording data, etc., and the desired carbonyl compound and cyanating agent content and cyanohydrin concentration. This is done by a program set to do this.

≪Cyanohydrin-containing liquid manufacturing equipment≫
The apparatus for producing a cyanohydrin-containing liquid according to the present invention (hereinafter also referred to as “this apparatus”) includes a supply unit for supplying a raw material carbonyl compound and a raw material cyanating agent, and a reaction liquid containing cyanohydrin by reacting the supplied raw materials. A reactor to be obtained, a distillation apparatus for distilling the reaction liquid obtained in the reactor, and a liquid in the distillation apparatus provided in the distillation apparatus or on a flow path branched from the distillation apparatus. And at least one of the molar concentration of the carbonyl compound and the molar concentration of the cyanating agent, and a measuring instrument for measuring the molar concentration of cyanohydrin.
Such an apparatus can be suitably used in the above-described method for producing a cyanohydrin-containing liquid.

Although it does not restrict | limit especially as said supply part, For example, a pipeline etc. are mentioned.
The supply unit is a supply unit of a raw material carbonyl compound, and when the raw material carbonyl compound is a purified carbonyl compound, it is preferably not made of iron.

The distillation apparatus preferably has an outlet (extraction port) for the cyanohydrin-containing liquid at the bottom of the apparatus, and preferably has the measuring instrument near the outlet.
The measuring instrument preferably has any of automatic sampling ability, automatic detection ability, and automatic computing ability, and further preferably has an automatic recording ability, and more preferably has all of them.

This device controls members for automatically controlling distillation conditions based on the results measured by the measuring instrument, for example, the wiring connecting the measuring instrument and the distillation device (device for controlling the distillation temperature, etc.) and the distillation conditions. It is preferable to have a command unit that sends a signal for performing the control, a control unit that controls distillation conditions based on the signal from the command unit, and the like.

In addition to the above members, this apparatus has been used in conventional manufacturing apparatuses such as a storage tank for storing raw materials and products, a supply unit for supplying a reaction liquid to a distillation apparatus, and supplying a catalyst or the like to a reactor. You may have a member.

Next, although an Example is given and this invention is demonstrated concretely, this invention is not limited to this.
[Method for quantification of acetaldehyde, hydrogen cyanide and lactonitrile when acetaldehyde and hydrogen cyanide are reacted in excess of acetaldehyde]

<1. Acetaldehyde Quantification Method>
Using a part of the liquid extracted from the reaction liquid or the distillation apparatus, the absorbance at a wavelength of 330 nm peculiar to acetaldehyde was obtained with an ultraviolet absorptiometer. From this absorbance, the molar concentration of acetaldehyde in the liquid was measured from a calibration curve in which the correlation between the absorbance and the molar concentration of acetaldehyde in the reaction solution was obtained in advance.

<2. Method for quantifying hydrogen cyanide>
Using a part of the reaction solution, the cyan concentration was determined with a cyan meter. The molar concentration of hydrogen cyanide was measured from a calibration curve in which the correlation between the cyan concentration and the hydrogen cyanide concentration was obtained in advance using the cyan meter.

<3. Creating a calibration curve>
Prior to obtaining the refractive index of the liquid, the following calibration curve was prepared.
1) A plurality of lactonitrile aqueous solutions in which the composition ratio of water / lactonitrile is changed between 100% water and 100% lactonitrile are prepared, and the refractive index of each is measured. A calibration curve was prepared (calibration curve A-0).
2) Acetaldehyde was added to the specific aqueous solution of lactonitrile to prepare a composition solution of acetaldehyde / lactonitrile / water having different acetaldehyde concentrations, and the respective refractive indexes were measured.
3) A lactonitrile aqueous solution in which the molar concentration of lactonitrile was different from that in 2) above was also measured for the refractive index in the same manner as in 2).
4) Using a group of data in which the molar concentration of acetaldehyde was the same specific concentration, a calibration curve between the molar concentration of lactonitrile and the refractive index was prepared (calibration curve A-1).
5) A calibration curve of lactonitrile molar concentration and refractive index was similarly prepared for each molar concentration of the same acetaldehyde with respect to the data of the molar concentration of acetaldehyde different from 4) (calibration curve A). -2 to AX).

<4. Method for quantifying lactonitrile>
A calibration curve corresponding to the molar concentration of acetaldehyde obtained from the ultraviolet absorption spectrophotometer of the liquid is selected from (A-0 to AX) or created by interpolating from the calibration curve group. And the molar concentration of lactonitrile were determined from the refractive index n of the liquid.

[Example 1]
A flask equipped with a distillation tube and a cooling tube was charged with raw material acetaldehyde having a content of a component (specific impurity A) having a boiling point of 25 ° C. or higher at normal pressure of 600 mass ppm, and the temperature was adjusted to 40 at a pressure of 50 KPaG. When distillation was performed by heating at 0 ° C., purified acetaldehyde having a specific impurity A content of 160 mass ppm was obtained.

In addition, content of the specific impurity A in raw material acetaldehyde and refinement | purification acetaldehyde was measured by the above-mentioned method.

Purified acetaldehyde is continuously fed as it is to a CSTR type reactor (continuous tank reactor) equipped with a stirrer and a cooler while stirring, and hydrogen cyanide and water are mixed at a molar ratio of acetaldehyde / hydrogen cyanide of 1. The reaction temperature is 15 to 20 ° C., and the reaction temperature is adjusted to 5 to 6 with a 5% by mass sodium hydroxide aqueous solution so that the residence time is 3 hours. The reaction was conducted while continuously extracting the liquid.
The conversion rate of the obtained reaction solution was 99.0%, the conversion rate of hydrogen cyanide was 100.0%, and the yield of lactonitrile was 98.9% with respect to the amount of supplied acetaldehyde, with respect to the amount of supplied hydrogen cyanide. It was 100.0%.

Further, a 10% by mass sulfuric acid aqueous solution was supplied to the lactonitrile-containing liquid obtained by the reaction, adjusted to pH 1.0, and a pH-adjusted lactonitrile-containing liquid was obtained.
The lactonitrile-containing liquid prepared at the pH was continuously supplied to a distillation column to perform distillation. As distillation conditions, the distillation temperature is 40 ° C., the distillation pressure is 7.5 KPa, the residence time of the distillation column is 0.5 hour, and the measuring instrument is a mole of acetaldehyde and lactonitrile on the flow path branched from the bottom of the distillation column. The concentration was automatically measured.
In the automatic measurement, automatic sampling, automatic detection, and automatic calculation were performed. In addition, a controller that can automatically adjust the distillation temperature in accordance with the molar concentration of acetaldehyde and lactonitrile output from the ultraviolet absorptiometer and refractometer was connected to the measuring instrument online.

Based on the result of the automatic measurement, the control device sets the distillation temperature to 40 ° C. ± 2 so that the lactonitrile concentration of the lactonitrile-containing liquid at the bottom of the distillation column is 80 mass% and the acetaldehyde concentration is 300 mass ppm or less. Fine adjustment in the range of 5 ° C.
The acetaldehyde content in the lactonitrile-containing liquid obtained by distillation was in the range of 200 mass ppm ± 10 mass ppm, and the concentration of lactonitrile was in the range of 80 mass% ± 0.25 mass%. Since the conversion rate of hydrogen cyanide in the reaction solution was 100.0%, the solution after distillation did not contain hydrogen cyanide.

[Comparative Example 1]
In Example 1, lactonitrile was used in the same manner as in Example 1 except that the distillation was controlled only by controlling the distillation temperature, distillation pressure and residence time without measuring the molar concentrations of acetaldehyde and lactonitrile in the distillation column. A containing liquid was produced.

The acetaldehyde content in the lactonitrile-containing liquid obtained by distillation was in the range of 840 mass ppm ± 200 mass ppm, and the concentration of lactonitrile was in the range of 75 mass% ± 5 mass%.

The cyanohydrin-containing liquid produced by the production method according to the present invention is useful as a starting material for various compounds. For example, a lactonitrile-containing liquid can be used as it is as a raw material for lactic acid, lactic acid ester, alanine and the like. .

Claims (13)

A method for producing a cyanohydrin-containing liquid, comprising the following steps 1 to 4.
Step 1: A step of obtaining a reaction liquid containing cyanohydrin by reacting a raw material carbonyl compound and a raw material cyanating agent. Step 2: A purification step of supplying the reaction liquid obtained in Step 1 to a distillation apparatus and distilling the reaction liquid. Step 3: Measuring at least one of the molar concentration of the carbonyl compound and the molar concentration of the cyanating agent and the molar concentration of cyanohydrin contained in the liquid in the distillation apparatus. Step 4: Purification based on the measurement result. Process control process The production method according to claim 1, wherein the purification step is controlled in step 4 so that the contents of the carbonyl compound and the cyanating agent in the liquid in the distillation apparatus are each 1000 ppm by mass or less. The production method according to claim 1 or 2, wherein the purification step is controlled in step 4 so that the concentration of cyanohydrin in the liquid in the distillation apparatus is 5 to 100% by mass. The production method according to any one of claims 1 to 3, wherein, in the step 4, the method for controlling the purification step is to change a distillation temperature. The production method according to any one of claims 1 to 4, wherein the distillation temperature in the step 2 is 20 to 60 ° C. The production method according to any one of claims 1 to 5, wherein in the step 2, the reaction solution is continuously supplied to the distillation apparatus. The production method according to any one of claims 1 to 6, wherein the measurement is performed in the distillation apparatus or on a flow path branched from the distillation apparatus. The manufacturing method according to any one of claims 1 to 7, wherein the measurement is automatic measurement. The production method according to any one of claims 1 to 8, wherein the molar concentration is measured using at least one selected from an ultraviolet absorptiometer and a refractometer. The production method according to any one of claims 1 to 9, wherein the raw material carbonyl compound is a compound represented by the formula (A).
R ¹ COR ² ... Formula (A)
In the formula (A), R ¹ and R ² are each independently a hydrogen atom, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, a heterocyclic group, or a part of these groups It is a group substituted with a substituent. The production method according to any one of claims 1 to 10, wherein the raw material carbonyl compound is acetaldehyde having a content of a component having a boiling point of 25 ° C or higher at normal pressure of 300 mass ppm or less. The production method according to any one of claims 1 to 11, wherein the raw material cyanating agent is a compound represented by the formula (B).
M (CN) _n ... Formula (B)
In the formula (B), M is a hydrogen atom, an alkali metal, an alkaline earth metal, iron, copper, or zinc, and n is a valence of M. A supply section for supplying a raw material carbonyl compound and a raw material cyanating agent;
A reactor for reacting the supplied raw material to obtain a reaction liquid containing cyanohydrin;
A distillation apparatus for distilling the reaction solution obtained in the reactor;
At least one of the molar concentration of the carbonyl compound and the molar concentration of the cyanating agent contained in the liquid in the distillation apparatus provided in the distillation apparatus or on the flow path branched from the distillation apparatus, and cyanohydrin An apparatus for producing a cyanohydrin-containing liquid, comprising a measuring instrument for measuring a molar concentration.