JP2989477B2 - Purification method of ultra-high purity acetonitrile and crude acetonitrile - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for purifying ultra-high purity acetonitrile and crude acetonitrile. More specifically, a wavelength of 200 to 40, which is highly purified and industrially used for a liquid chromatography mobile phase solvent, particularly, a high performance liquid chromatography mobile phase solvent.
The present invention relates to ultrahigh-purity acetonitrile having an absorption in the ultraviolet region of 0 nm, a free cyan content, and a reduced permanganate-reducing substance, and a purification method thereof.

[0002]

2. Description of the Related Art Currently, commercially available acetonitrile is mainly obtained as a by-product in producing acrylonitrile or methacrylonitrile by a catalytic ammoxidation reaction of propylene or isobutene with ammonia and molecular oxygen. Is recovered and purified. Since acetonitrile obtained as this by-product contains many impurities, various methods for purification have been proposed.

For example, the present inventors have previously described Japanese Patent Application No.
No. 5-128551, a method for producing high-purity acetonitrile in which the absorbance of ultraviolet light having a wavelength of 200 to 400 nm becomes 0.05 or less by contacting with a substance selected from a solid base and an adsorbent after reaction with nascent oxygen. Has been proposed. However, in the conventionally proposed method, the wavelength 20
Although the absorbance of ultraviolet light at 0 to 400 nm can be reduced to 0.05 or less, the concentration of free cyanide is 0.4 ppm by weight or less, and the fading rate of permanganate-reducing substance is 15 after 36 hours.
% Or less high purity acetonitrile could not be obtained. In particular, it was not satisfactory when used as a mobile phase solvent for high performance liquid chromatography in pesticide residue tests.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ultra-high-purity acetonitrile used for a high-performance liquid chromatography mobile phase solvent containing a small amount of impurities and a method for producing the same.

[0005]

Means for Solving the Problems The present inventors have conducted detailed studies on a method of contact treatment with ozone. As a result, acid and permanganate reducing substances are produced by the contact treatment with ozone. They have found that they can be removed by contact with a basic substance and / or an adsorbent and further a permanganate reducing substance removing agent, and have found a simple purification method which is the object of the present invention.

[0006] Surprisingly, after contacting the liquid treated with ozone with at least one of a basic substance and an adsorbent, a permanganate reducing substance is separated and removed, and a low boiling point compound contained in acetonitrile is further removed. By removing high-boiling compounds, the absorbance of ultraviolet rays having a wavelength of 200 to 400 nm is 0.05 or less, and the free cyan content is 0.4 wt ppm.
Hereinafter, the fading rate of the permanganate reducing substance is 1 after 36 hours.
The inventors have found that ultrahigh-purity acetonitrile of 5% or less can be obtained, and have completed the present invention.

That is, the first aspect of the present invention is that the wavelength is 200 to 40.
Liquid chromatography characterized in that the absorbance of ultraviolet light at 0 nm is 0.05 or less, the concentration of free cyanide is 0.4 ppm by weight or less, and the fading rate of permanganate reducing substance is 15% or less after 36 hours. Ultra-pure acetonitrile for mobile phase solvents. The second aspect of the present invention is to produce ultra-high-purity acetonitrile, which is used in a liquid chromatography mobile phase solvent, particularly, a high-performance liquid chromatography mobile phase solvent by performing a simple purification method of crude acetonitrile and further advanced purification. In other words, when purifying crude acetonitrile,
(1) a first step of contacting crude acetonitrile as raw material with nascent oxygen; and (2) contacting acetonitrile after the first step with at least one substance selected from a basic substance and an adsorbent. A second step, (3) a third step of separating and removing a permanganate reducing substance contained in the acetonitrile that has passed through the second step, and (4) a low level of acetonitrile that has passed through the third step. A method for purifying crude acetonitrile, comprising purifying crude acetonitrile comprising a fourth step of separating and removing a boiling point compound and a high boiling point compound.

The raw material crude acetonitrile used in the purification method of the present invention has an absorbance of ultraviolet light having a wavelength of 200 nm of 0.1.
Above acetonitrile, propylene, isobutene or 3
Crude acetonitrile obtained as a by-product when acrylonitrile or methacrylonitrile is produced by a catalytic ammoxidation reaction of grade butanol with ammonia and molecular oxygen can be used.

The raw material acetonitrile has a wavelength of 200 n.
A crude acetonitrile having an absorbance of 0.1 m or more for ultraviolet light of m can be used, preferably a crude acetonitrile having an absorbance of 200 or more for ultraviolet light having a wavelength of 0.1 or more and 5 or less, more preferably an absorbance of 200 nm for ultraviolet light. Is preferably 0.1 or more and 3 or less. Also,
In the purification method of the present invention, crude acetonitrile as a raw material is not particularly limited, and crude acetonitrile produced by another production method can be used as a raw material. Specifically, ethane, propane, butane,
Crude acetonitrile derived from an ammoxidation reaction of a saturated hydrocarbon compound such as isobutane and pentane and an aromatic compound such as carbon monoxide, toluene and xylene can also be used.

According to the purification method of the present invention, a wavelength of 200 nm
The crude acetonitrile having an ultraviolet absorbance of 0.1 or more is used as a raw material, the absorbance of ultraviolet light having a wavelength of 200 to 400 nm is 0.05 or less, and the free cyanide concentration is 0.4 weight pp.
m or less, and ultra-high-purity acetonitrile having a permanganate-reducing substance fading rate of 15% or less after 36 hours can be obtained.

Furthermore, crude acetonitrile having an absorbance of ultraviolet light having a wavelength of 200 nm of less than 0.1 can be used as a raw material. However, using these raw materials is not an attractive method, mainly because of its small effect from an economic point of view. The absorbance of acetonitrile to ultraviolet light in the present invention is a value measured using a quartz cell having an optical path length of 10 mm at a detection wavelength with distilled water as a control.

In the present invention, the free cyan density is J
The values measured by IS K0102 38.2 pyridine-pyrazolone spectrophotometry are shown. Further, the fading rate of the permanganate-reducing substance in the present invention refers to JIS K 8032
Add 0.1 ml of 0.1N potassium permanganate to 10 g of the sample and shake it by referring to the method described above.
It was measured using Model 00 and used as an index for permanganate reducing substances.

Permanganic acid fading rate (%) = (1- (A / B)) × 100 A: Absorbance after 36 hours B: Absorbance immediately after start Wavelength: 545 nm The first step in the purification method of the present invention is as follows: And contacting crude acetonitrile with nascent oxygen. The purpose of this step is to decompose impurities having a double bond, particularly allyl alcohol, oxazole, and acrylonitrile, which are difficult to remove by methods such as distillation, adsorption or reaction, by contact with nascent oxygen, and It is to convert to a compound that can be easily separated and removed in the process. Compounds that generate nascent oxygen include permanganic acid or salts thereof, such as potassium permanganate, peroxides such as hydrogen peroxide, sodium peroxide, barium peroxide, oxyacid or salts thereof, for example, Sodium zinc chlorate, potassium hypochlorite, sodium hypoiodite, potassium hypoiodite, sodium hypobromite, potassium hypobromite, sodium chlorate, potassium chlorate, sodium iodate, potassium iodate , Sodium bromate, potassium bromate, sodium perchlorate, potassium perchlorate, perchloric acid, periodate, sodium periodate, potassium periodate, an ozone-containing gas, and the like can be used. It is preferable to use a contained gas. Through this step, the effect of separating and removing impurities in the subsequent steps can be significantly improved.

The ozone-containing gas used in the present invention is obtained by supplying air or oxygen or an oxygen-containing gas to an ozone generator . When contacting with crude acetonitrile, the ozone-containing gas is diluted with a gas such as nitrogen, carbon dioxide or air. It can also be used. The concentration of ozone in the ozone-containing gas is 0.01 to
It is 5.0 % by weight, preferably 0.1 to 2.0% by weight. If the ozone concentration is too low, the time required for contact with the crude acetonitrile becomes longer, the reactor becomes large, and the accompanying loss of acetonitrile by the supplied gas increases, which is not effective.

The temperature at which the crude acetonitrile is brought into contact with the ozone-containing gas is from -40 to 80 ° C., preferably from 10 to 4 ° C.
0 ° C. If the temperature is too low, there are problems such as slowing down the reaction rate and precipitation of trace components. If the temperature is too high, an excessive reaction proceeds, and the yield of acetonitrile decreases. The pressure at which the crude acetonitrile is brought into contact with the ozone-containing gas may be reduced pressure, normal pressure, or increased pressure, but is preferably in the range of normal pressure to 10 atm.

The contact between the crude acetonitrile and the ozone-containing gas can be carried out batchwise or continuously. In the batch system, it can be carried out in a single-stage or multi-stage contact tank or a bubble tower with a stirring device, but preferably in a contact tank with a stirring device in order to improve gas-liquid contact. . Further, in order to improve the contact between the crude acetonitrile and the ozone-containing gas, the ozone-containing gas is preferably supplied as small bubbles into the acetonitrile from one or more nozzles. Further, the position for supplying the ozone-containing gas is preferably below or beside the stirring blade, and the optimum position and number can be determined by observing the stirring state of the acetonitrile depending on the structure of the tank and the blade. .

The contact between the crude acetonitrile and the ozone-containing gas in the batch system depends on the amount of impurities contained in the crude acetonitrile, but is preferably 1 to 10,000 based on the volume of the acetonitrile contacted with the ozone-containing gas.
Twice, more preferably 10 to 1000 times the gas amount to 1
It is preferable to supply for ~ 300 minutes, more preferably for 10 ~ 120 minutes. If the supply time is too short, there is a problem that the reaction between the ozone and the impurities is insufficient, and the gas flow rate is high, resulting in a large loss due to entrainment of acetonitrile. There is no merit in terms of properties, and an excessive oxidation reaction proceeds.

The supply time of the ozone-containing gas can be determined by analyzing the ozone concentration in the exhaust gas. For analysis of the ozone concentration, a continuous analyzer using an iodine titration method, an ultraviolet absorption method, a chemiluminescence method, or the like can be used. The supply time of the ozone-containing gas is
Specifically, it is preferable to supply the exhaust gas until the ozone concentration in the exhaust gas becomes 80% or more of the ozone concentration of the supplied gas, and more preferably 90% or more. In the continuous method, it can be carried out in a packed tower, a wet wall tower, a bubble tower, or the like, but it is preferably carried out in a packed tower. Raschig rings, lessing rings, berl saddles,
Interlock saddles, teralet packings, pole rings, McMahon packings, dex rings, and the like can be used. These fillers can be made of a material such as porcelain, metal, plastic or carbon.

The contact between the crude acetonitrile and the ozone-containing gas can be carried out in countercurrent or cocurrent, but it is preferable to make contact in countercurrent. In the packed tower, a liquid redistribution plate may be provided at an appropriate height to increase the gas-liquid contact efficiency. The ratio of the ozone-containing gas to the crude acetonitrile is preferably 1 to 10,000 by volume, more preferably 10 to 10,000.
And a value that does not cause flooding is selected according to the characteristics of the packed tower.

The second step in the purification method of the present invention is a step of bringing the acetonitrile that has passed through the first step into contact with at least one substance selected from a basic substance and an adsorbent. The purpose of this step is to convert impurities contained in acetonitrile that has passed through the first step into compounds that can be easily separated, or to perform adsorption separation. The contact of the acetonitrile with a basic substance and an adsorbent in the second step of the present invention is from -40 to 8
At a temperature of 0 ° C., furthermore at a temperature of 5 to 60 ° C., in particular 10 to
It is preferably carried out at a temperature of 40 ° C.

As the basic substance in the present invention, a liquid or solid basic substance is used. Liquid basic substances include hydroxides, carbonates or bicarbonates of Li, Na, K, Rb or Cs as alkali metals, hydroxides of Mg, Ca, Sr or Ba as alkaline earth metals, and ammonia. Alternatively, a compound selected from amines, an aqueous solution thereof, or a solution thereof can be used.

In order to facilitate the separation and removal in the subsequent distillation step, the amine used here should have an amine whose boiling point is at least 5 ° C., more preferably at least 10 ° C., apart from the boiling point of acetonitrile. Preferably, specifically, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, tripropylamine, s-butylamine, t-butylamine, dibutylamine, tributylamine, pentylamine Aliphatic amines such as amine, t-pentylamine, hexylamine, heptylamine, octylamine, ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, ethanolamine, diethanolamine and triethanolamine Or aniline, pyridine, quinoline, o- toluidine, m- toluidine, and aromatic amines p- toluidine.

The solvent of the solution used here has a boiling point of 5 ° C. or more, more preferably 10 ° C., compared to the boiling point of acetonitrile in order to facilitate separation and removal in the subsequent distillation step.
It is preferable to use a solvent which is separated from the solvent by at least 0 ° C., specifically, methanol, 1-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol, 3-pentanol, ethylene glycol, , 3
Aliphatic alcohols such as dioxane, 1,4-dioxane, 1,2-propanediol, 1,3-propanediol, pentane, hexane, octane, nonane,
And saturated aliphatic hydrocarbons such as decane. Also, acetonitrile itself can be used as the solvent.

The concentration of the basic substance in the aqueous solution or solution can be arbitrarily set at a concentration lower than the saturation solubility, but a slurry may be used. The amount of addition of these liquid basic substances may be such that the pH value of the aqueous solution obtained by diluting the acetonitrile 1/10 with water is 5 or more, preferably 5 to 9, more preferably 5 to 9. It is better to control so as to be 6 to 8.

The contact between the acetonitrile and the liquid basic substance may be carried out by injecting the mixture into a pipe equipped with a line mixer in order to promote the reaction, or adding the mixture to a single-stage or multi-stage contact tank equipped with a stirring device. It is preferable to do so. The liquid basic substance forms a salt with an acid such as carboxylic acid and precipitates as a sticky precipitate and the like.To prevent trouble due to clogging in the next distillation step, filtration, sedimentation, etc. An operation for separating these precipitates is required. When water is contained in the basic substance added as a liquid, acetonitrile is removed simultaneously with the removal of water to form an azeotropic composition with acetonitrile when water is separated and removed in the next distillation step. And the recovery rate of acetonitrile decreases.

Further, an ammonia gas or an ammonia-containing gas as a basic substance can be supplied into the acetonitrile for reaction. In order to improve the contact between ammonia gas or ammonia-containing gas and the acetonitrile and promote the reaction, a method such as supplying small bubbles into the acetonitrile from one or more nozzles or performing stirring is used. Good. The supply amount of ammonia or the ammonia-containing gas may be any amount as long as the pH value of the aqueous solution obtained by diluting the acetonitrile 1/10 with water becomes 5 or more, but is preferably 5 to 9, and more preferably 6 to 8. It is better to control so that

Solid basic substances include anion exchange resins, alkali metal hydroxides, carbonates or bicarbonates, alkaline earth metal oxides, hydroxides or carbonates, and heterometallic oxides. Activated carbon, a solid base, a substance in which a compound of an alkali metal or an alkaline earth metal is supported on a carrier, and activated carbon. As the anion exchange resin used in the present invention, a porous or gel type strongly basic anion exchange resin or a weakly basic anion exchange resin can be used. Either type of ion exchange resin for aqueous solution or ion exchange resin for non-aqueous solution can be used. Strongly basic anion exchange resin converts the ionic form to OH form or C by regenerating exchange groups such as trimethylammonium group and dimethylethanol.
It is preferably used as the O ₂ form.

Further, the weakly basic anion exchange resin is 1 to 3
It is preferable to use an exchange group such as a primary amino group after performing a regeneration treatment with NaOH, NH ₄ OH or the like. These anion exchange resins are preferably used after being subjected to regeneration treatment of the exchange groups and then contacted with a sufficient amount of acetonitrile for washing to remove water, impurities and the like contained in the ion exchange resin.

As the solid basic substance used in the present invention, specifically, alkali metals such as Li, Na and
Hydroxides, carbonates or bicarbonates of K, Rb, Cs, oxides, hydroxides or carbonates of Mg, Ca, Sr, Ba which are alkaline earth metals, silica which is a mixture of different metal oxides Magnesia, calcium silica oxide, strontium silica oxide, barium silica oxide, oxides, hydroxides, carbonates or bicarbonates, which are compounds of alkali metals or alkaline earth metals, may be used as a carrier. Activated carbon, silica, alumina, titania or zirconia is used, the loading amount is 0.01 to
It is 50% by weight, preferably 0.1 to 10% by weight.

Further, as a solid basic substance, N ₂ O,
Activated carbon that has been activated with NH ₃ or ZnCl ₂ —NH ₄ Cl—CO ₂ to exhibit basicity can also be used. As the adsorbent, activated carbon, activated alumina, silica gel, synthetic zeolite, natural zeolite, adsorption resin, natural clay mineral, silica alumina, silica magnesia, silica boria and the like are used.

The solid basic substance and / or adsorbent can be handled as a powder or a granule, and the size is 0.001 to 100 mm, more preferably 0.01 to 20 mm.
Are preferred. Further, the powder can be used as a cylindrical or spherical molded body by tableting or the like.

The contact between the basic substance and / or the adsorbent and the acetonitrile can be carried out in a continuous manner or in a batch manner, but is preferably carried out industrially in a continuous manner. As a continuous method, a solid basic substance can be filled in a part of a packed tower or a pipe, and the solid basic substance can be supplied and contacted with the acetonitrile. Also, space velocity, S
V may be operated at 0.001 to 1000 (1 / min), preferably 0.01 to 100 (1 / min).

The batch method can be carried out in a contact tank equipped with a stirring device or a shaking device. The contact time is preferably 0.1 to 1000 minutes, more preferably 1 to 120 minutes. In the purification method of the present invention, the third step comprises the first step.
This is a step of separating and removing the permanganate reducing substance in acetonitrile that has passed through the step or the second step.

The contact between the acetonitrile and the permanganate reducing agent removing agent in the third step of the present invention is -40.
It is preferably carried out at a temperature of from 0 to 200C, more preferably from 5 to 130C. Examples of the permanganate-reducing substance removing agent in the present invention include iron chloride, copper chloride, aluminum chloride, sodium p-toluenesulfonchloroamide, a strongly acidic resin having a sulfone group, leucosulfonic acid, sodium hydrogen sulfite, and sodium thiosulfate. , Hydroxylamine hydrochloride, hydrazine, phenylhydrazine, p-
Nitrophenylhydrazine, 2,4-dinitrophenylhydrazine, semicarbazide, dimedone and the like can be mentioned. These may be carried on various carriers. As the carrier, activated carbon, silica, alumina, titania, zirconia, ion-exchange resin and the like are used, and the loading amount is 0.01 to
It is preferably 50% by weight, more preferably 0.05 to 10% by weight. Solid permanganate reductants are
Although it can be handled as a powder or a granule, its size is 0.001 to 100 mm, and further 0.01 to 2 mm.
The one with 0 mm is preferable. The powder can also be used as a cylindrical or spherical molded body by tableting or the like.

The contact between the permanganate reducing agent-removing agent and the acetonitrile can be carried out in a continuous manner or in a batch manner, but is preferably carried out industrially in a continuous manner. As a continuous method, a part of a packed tower or a pipe or the like can be filled with a solid permanganate-reducing substance removing agent, and can be supplied and contacted with the acetonitrile. Further, the space velocity SV is 0.001 to 1000 (1 /
min), more preferably 0.01 to 100 (1 / min).

The batch system can be carried out in a contact tank equipped with a stirring device or a shaking device. The contact time is preferably from 0.1 to 1000 minutes, more preferably from 1 to 120 minutes. A method of adding the permanganate-reducing substance-removing agent soluble in acetonitrile before being introduced into the fourth step can also be adopted. In the purification method of the present invention, the fourth step is the first step, the second step or the third step.
This is a step of separating and removing low-boiling compounds and high-boiling compounds in acetonitrile that have passed through the step.

The method of separation and removal is selected from a distillation method and a membrane separation method, and a distillation method is particularly preferred as an industrial separation method. The distillation column used in the present invention is a tray column or a packed column. Examples of the tray column include a cross-flow contact type having a downcomer and a countercurrent contact type without a downcomer. In addition, the bubble opening type, perforated plate type,
A valve type or the like can be used. The number of stages in this distillation column is not particularly limited as long as it is 10 or more, but 30 to 80
Stepped ones are preferred.

As an example of the packed tower, a tower filled with a Raschig ring, a dressing ring, a pole ring, a Berl saddle, an interlock saddle, a teralet packing, a Dickson ring, a McMahon packing or the like can be used. As the material of the filler, a material made of porcelain, metal, plastic, carbon or the like can be used. The packed tower may be provided with a liquid redistribution plate at an appropriate height to enhance the gas-liquid contact efficiency.

In the present invention, as a method for separating and removing low-boiling compounds and high-boiling compounds as compared with acetonitrile, a method using two distillation columns is exemplified. Specifically, a method in which a low-boiling compound is separated and removed from the top in a first column, and a high-boiling compound is separated and removed in a second column to obtain purified acetonitrile from the top, or from the bottom in the first column. There is a method of separating and removing high-boiling compounds, separating and removing low-boiling compounds from the top column in the second column, and obtaining purified acetonitrile from the bottom or the upper part thereof.
When the water content in acetonitrile is 23% by weight or more, it is preferable to separate and remove water first by azeotropic distillation with acetonitrile, and to remove acetonitrile from the top in the second column in order to improve the quality of acetonitrile. Therefore,
A method is preferred in which a low-boiling compound is separated and removed from the top in the first column, and a high-boiling compound is separated and removed from the bottom in the second column to obtain purified acetonitrile from the top.

However, this is not the case when the water content in acetonitrile is less than 23% by weight. In addition to the water contained in the crude acetonitrile,
It is produced by the oxidation reaction with ozone. Further, even in a single distillation column, the low-boiling compound and the high-boiling compound can be separated and removed. Specifically, the acetonitrile is supplied to an intermediate portion of the distillation column, a low-boiling compound is extracted from the top of the distillation column, a high-boiling compound is extracted from the bottom of the distillation column, and purified from above or below the acetonitrile supply position. Of acetonitrile, and more preferably a method of obtaining purified acetonitrile from above the supply position of the acetonitrile.

In these separation and removal operations, the reflux ratio and the amount of low-boiling compounds and high-boiling compounds withdrawn can be determined as conditions for obtaining purified acetonitrile suitable for the purpose. The withdrawal amount of the top containing the low-boiling compound and the withdrawal amount of the bottom containing the high-boiling compound are 1% or more, and preferably 5% or more, respectively, of the supplied acetonitrile. When the amount of extraction from the top and the bottom is small, the absorbance of ultraviolet light having a wavelength of 200 to 400 nm is 0.05 or less, and the free cyan content is 0.4 wt ppm or less due to a trace amount of impurities contained in the extracted acetonitrile. In some cases, the fading rate of the permanganate reducing substance does not become 15% or less after 36 hours.

Although the low-boiling compounds and the high-boiling compounds can be separated and removed by using three or more distillation columns, this is not an economically effective method. These distillation operations can be performed at any of reduced pressure, normal pressure, and pressurized pressure, but are usually preferably in the range of normal pressure to 10 atm. In controlling the operation of these three steps, precise and advanced operation control is particularly required in order to obtain acetonitrile used as a mobile phase solvent for high performance liquid chromatography. As one of the methods, it is an effective method to measure a crude acetonitrile raw material and physical properties of each step by using near-infrared spectroscopy and control the operation.

[0043]

EXAMPLES The present invention will be described below in detail with reference to examples, but the contents of the present invention are not limited thereto. The physical properties were measured as follows. (1) Measurement of ultraviolet absorption spectrum; optical path length 10 mm
Was measured using a spectrophotometer 288A manufactured by Hitachi, Ltd. using distilled water as a control.

(2) Analysis by gas chromatography;
Using a gas chromatograph HP-5890 manufactured by Yokogawa, the inner diameter of the capillary column having a filler of silicon OV-1 is 0.
25mm * length 50m, column temperature first at 40 ℃ 5
After the temperature was maintained for 10 minutes, the temperature was raised to 200 ° C. at a rate of 10 ° C./min, and finally the temperature was maintained for 10 minutes.

(3) Acid analysis;
Measured according to 6 (1). (4) Free cyan density: JIS K0102 3
8.2 Value measured by pyridine-pyrazolone absorption spectrophotometry. (5) Permanganate reducing substance fading rate: JIS K
80 ml of 0.1 N potassium permanganate was added to 10 g of the sample according to the method described in 8032, shaken, left standing in a cool dark place for 36 hours, and measured using a Shimadzu UV2000 model to indicate the index of the permanganate reducing substance. And

Permanganic acid fading rate (%) = (1− (A / B)) × 100 A: Absorbance after 36 hours B: Absorbance immediately after start Wavelength: 545 nm

[0047]

Example 1 200 nm as acetonitrile as a raw material
The following operation was performed using acetonitrile having an ultraviolet absorbance of 1.668, acrylonitrile as impurities of 7 wt ppm, and a free cyanide concentration of 1.25 wt ppm. As a first step, the acetonitrile was supplied to the ozone contact tower having a diameter of 30 mm under atmospheric pressure at a temperature of 20 ° C. from the top of the tower at 300 ml / Hr, and 0.24% by weight (5.1 g) of ozone was supplied from the bottom of the tower. / Nm ³ : “Nm ³ ” is 0
180 Nl / Hr containing O ³ gas at 1 ° C. and 1 atm.
).

Acetonitrile contacted with ozone was extracted from the bottom of the ozone contact tower. Acrylonitrile in the extracted acetonitrile was not detected, but the acid concentration increased to 52 ppm by weight, and the permanganic acid fading rate increased to 100%. Next, as a second step, the acetonitrile passed through the first step is continuously supplied to a column having a diameter of 20 mm packed with 50 ml of a non-aqueous porous type weakly basic anion exchange resin (trade name: Amberlyst A-21), The contact was made at a temperature of 20 ° C. The absorbance of the finally obtained acetonitrile at 200 nm UV was 1.780, and acrylonitrile was below the detection limit by gas chromatography analysis.
The acid content was 2 ppm, and the permanganic acid fading rate was 92 ppm.
%Met.

As is evident from the results, acrylonitrile is decomposed by the treatment in the first step, but the acid and permanganate reducing substances increase. Further, as a third step, the acetonitrile passed through the second step was continuously supplied to a column having a diameter of 20 mm filled with 50 ml of sodium bisulfite, and brought into contact at a temperature of 20 ° C.

Next, as a fourth step, a diameter of 40 mm
Using a perforated plate-type distillation apparatus having a total of 65 stages, continuously supplying acetonitrile having passed through the third step to 10 stages, operating at a reflux ratio of 50 with the top pressure at atmospheric pressure, and containing low boiling compounds from the top Acetonitrile was withdrawn in an amount of 20% of the supplied amount, acetonitrile containing a high-boiling compound was withdrawn from the bottom of the column in an amount of 10% of the supplied amount, and purified acetonitrile was obtained in an amount of 70% of the supplied amount from 40 stages. The recovery of acetonitrile was 70%.

The absorbance of this acetonitrile at a wavelength of 200 nm was 0.021, the free cyanide content was 0.05 ppm by weight, and the fading rate of the permanganate-reducing substance was 6% after 36 hours.

[0052]

EXAMPLE 2 In the third step of Example 1, except that 50 ml of sodium hydrogen sulfite which had been ion-exchanged with a non-aqueous porous strong basic anion exchange resin (trade name Amberlyst A-27) was used. The same operation as in Example 1 was performed to obtain purified acetonitrile.

The acetonitrile had an absorbance of 0.020 for ultraviolet light having a wavelength of 200 nm, a concentration of free cyanide of 0.04 wt ppm, and a fading rate of permanganate-reducing substance of 4% after 36 hours.

[0054]

Example 3 In the third step of Example 1, sodium p-toluenesulfone chloroamide was added in an amount of 0.25 g / H.
The same operation as in Example 1 was performed, except that in r, the solution was supplied to acetonitrile after the second step, to obtain purified acetonitrile. The absorbance of this acetonitrile at an ultraviolet wavelength of 200 nm was 0.024, the concentration of free cyanide was 0.08 wt ppm, and the fading rate of the permanganate reducing substance was 9% after 36 hours.

[0055]

Example 4 Purification was performed in the same manner as in Example 1 except that in the third step of Example 1, iron chloride was supplied at 0.14 g / Hr to acetonitrile after the second step. Acetonitrile was obtained. The acetonitrile had an absorbance of 0.025 for ultraviolet light having a wavelength of 200 nm, a free cyanide content of 0.09 wt ppm, and a fading rate of the permanganate-reducing substance of 10% after 36 hours.

[0056]

Comparative Example 1 Purified acetonitrile was obtained in the same manner as in Example 1 except that the third step was omitted.
The acetonitrile has an absorbance of 0.027 for ultraviolet light having a wavelength of 200 nm and a free cyanide concentration of 0.7 weight pp.
m, permanganate reducing substance fading rate is 22 after 36 hours
%Met.

[0057]

According to the method for purifying crude acetonitrile of the present invention, the absorbance of ultraviolet light having a wavelength of 200 to 400 nm is 0.0
5 or less, the free cyanide concentration is 0.4 wt ppm or less,
Ultrahigh-purity acetonitrile having a permanganate-reducing substance fading rate of 15% or less after 36 hours can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C07C 255/03 C07C 253/34

Claims (2)

(57) [Claims] An absorbance of ultraviolet rays having a wavelength of 200 to 400 nm is 0.05 or less, a concentration of free cyanide is 0.4 ppm by weight or less, and a fading rate of permanganate reducing substance is 15% or less after 36 hours. Ultra-pure acetonitrile for liquid chromatography mobile phase solvents, characterized in that: 2. Purification of crude acetonitrile
(1) a first step of contacting crude acetonitrile as a raw material with nascent oxygen; and (2) contacting acetonitrile after the first step with at least one substance selected from a basic substance and an adsorbent. And (3) a third step of separating and removing the permanganate reducing substance contained in the acetonitrile that has passed through the second step, and (4) acetonitrile that has passed through the third step. And a fourth step of separating and removing the low-boiling compound and the high-boiling compound to be obtained, wherein the crude acetonitrile is purified.