JP3001020B2 - Acetonitrile purification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high quality acetonitrile, relates to the purification method of acetonitrile to obtain highly pure acetonitrile used in a solvent such as for liquid chromatography, especially.

[0002]

2. Description of the Related Art High-purity acetonitrile, especially acetonitrile used as a solvent for liquid chromatography (hereinafter abbreviated as "liquid chromatography"), has no ultraviolet absorption at 200 to 350 nm so that the ultraviolet absorption therein does not become the background. Need to be something. Conventionally, in order to obtain such acetonitrile, it has been necessary to purify crude acetonitrile by a complicated and non-industrial method.

[0003] That is, as a method for purifying acetonitrile by-produced in the ammoxidation reaction of propylene or the like, the following methods are known, but in all cases, only acetonitrile unsuitable for liquid chromatography was obtained.

For example, Japanese Patent Application Laid-Open No. 58-124751 discloses a method of producing acrylonitrile by catalytic ammoxidation of propylene with ammonia and oxygen.
In this method, acetonitrile is recovered by using two digesters. However, acetonitrile for liquid chromatography was not obtained, and the purification was only at the raw material level.

[0005] Japanese Patent Application Laid-Open No. 55-11847 discloses a method for concentrating acetonitrile.
JP-A-5-143949 discloses a method of extracting and removing water in acetonitrile with NaOH, and JP-A-55-143949 discloses a method of distilling and separating allyl alcohol in acetonitrile.
JP-A-5-129257 discloses a method for removing hydrogen cyanide from acetonitrile, but none of these methods alone could be used alone or in combination for a liquid chromatography solvent.

[0006] Under such circumstances, as a technique for thoroughly removing impurities and purifying until high-purity acetonitrile is obtained, a slightly East German patent DD (11) 217212 is used.
(A1) a method of performing an ozone treatment followed by a distillation treatment, and Chem. Tech (Leipzig), 37
(8), 328-30 discloses a method in which KMnO ₄ treatment is carried out and then distillation separation is performed, and Hoppe-Sey is also disclosed.
ler's Z. Physiol. Chem. , 363
(5), 485-6 only discloses a method of treating with an Al ₂ O ₃ column. However, none of these methods is sufficient as a method for purifying acetonitrile having no ultraviolet absorption suitable for a solvent for liquid chromatography.

[0007]

[0008] The present invention provides a method from crude acetonitrile produced as a byproduct in the ammoxidation reaction of propylene or the like, the industrial purification of highly pure acetonitrile that can be used in liquid chromatography solvent That is the task.

[0008]

Means for Solving the Problems As a result of repeated studies for solving the above-mentioned problems, the present inventors have found that after contacting crude acetonitrile as a by-product with sulfuric acid, the crude acetonitrile is further contacted with a gas containing ozone and distilled. Thus, the present inventors have found that this problem can be solved, and have reached the present invention. That is, the present invention provides high purity by contacting a crude crude acetonitrile obtained by subjecting propylene or isobutylene to an ammoxidation reaction in the presence of a catalyst with a gas containing ozone, and then neutralizing with a basic substance, followed by distillation. there is provided a method for purifying acetonitrile and obtaining the acetonitrile. Hereinafter, the present invention will be described in detail.

The crude acetonitrile used as the raw material of the present invention is
When producing acrylonitrile by ammoxidation of propylene such as those which can be obtained as a by-product, HCN contained in the acetonitrile recovered from its manufacturing process, acrylonitrile, H ₂ O, oxazole, allyl alcohol, acetone, etc. It is preferable that impurities are separated and removed.

As a method for separating and removing these impurities, for example, a “continuous acetonitrile recovery method” described in JP-A-58-124751, a method disclosed in Japanese Patent Publication No. 40-26814, or a method described in JP-A-55-26814. 118447
JP-A-55-153775, JP-A-55-143
949, JP-A-55-12957, JP-A-55-1
For example, a combination of the methods described in 43950 can be used.

According to these methods, the quality of acetonitrile, for example, is generally 200 pp of allyl alcohol.
m, acrylonitrile 5 ppm, oxazole 50 pp
m, hydrocyanic acid 5 ppm, propionitrile 200 ppm, H
_About 2500 ppm of 2O is obtained. Needless to say, different concentrations can be obtained depending on the equipment and operating conditions of the distillation column, reaction tank, extraction column, and the like.

According to the present invention, the above crude acetonitrile is contacted with sulfuric acid as a raw material, sulfuric acid and a reactant thereof are separated, and then contacted with a gas containing ozone, followed by distillation. This is to obtain high-purity acetonitrile.

That is, first, not completely removed allyl alcohol, acrylonitrile, oxazole, hydrocyanic acid,
Using crude acetonitrile containing acetone or the like as a raw material, sulfuric acid is added in an amount of 1 to 10 moles, preferably 2 to 6 moles relative to the unsaturated compound / carbonyl compound, and the temperature is 30 to 100.
C., preferably at 50 to 80.degree. C. for 10 to 120 minutes.

Next, mainly sulfuric acid and the reaction product with sulfuric acid are separated by distillation. The distillation can be performed by simple distillation or a distillation column having a number of stages. Distillation can be performed at normal pressure, but it is preferable to reduce the temperature by distillation under reduced pressure in order to suppress the reaction between sulfuric acid and acetonitrile. A temperature of -7 is applied to the fraction obtained by this distillation.
A gas containing ozone is contacted at 0 to 80 ° C, preferably at 10 to 60 ° C. This gas containing ozone is
Ozone concentration 0.01 to 10 vol%, preferably 0.1
A gas such as air or oxygen of about 5 vol% is used. At this time, an inert gas is added as a diluting gas to the gas containing ozone to avoid the explosion range of acetonitrile. As the inert gas, nitrogen, carbon dioxide or the like is used.

The supply amount of ozone is equal to or more than the amount of ozone required to completely extinguish compounds having a double bond (such as allyl alcohol, acrylonitrile, and oxazole) contained in acetonitrile. That is, the amount is 1 to 5 times, preferably 1.05 to 3 times the amount of ozone required to completely eliminate the compound having a double bond contained in acetonitrile. Confirmation of the point at which the reaction with ozone is stopped can be performed by analyzing the ozone concentration in the exhaust gas. As the analysis method, JIS method, continuous analysis calculation utilizing ultraviolet absorption, and the like are used.

Next, when the light-boiling compound and the high-boiling compound generated in the process of ozone treatment / neutralization treatment are separated from this liquid, the target product is obtained as a middle distillate. In this distillation, after removing the light-boiling compounds, the high-boiling compounds may be removed. On the contrary, it is preferable to remove the high-boiling compounds and then remove the light-boiling compounds. Alternatively, the light-boiling compound and the high-boiling compound may be simultaneously separated in one distillation column, and the target acetonitrile may be extracted as a side stream of the distillation column. These are operated in a batch or continuous manner.

These operations can be performed under any of reduced pressure, normal pressure, and increased pressure. However, in order to ensure high quality by suppressing the decomposition of impurities, vacuum distillation is preferable. Thus , high- purity acetonitrile can be produced.

[0018]

Next, the present invention will be described with reference to examples and comparative examples.

Example 1 Crude acetonitrile, a by-product of the ammoxidation reaction of propylene, was concentrated by distillation, and concentrated with caustic soda.
The reaction was carried out at 75 ° C. for 8 hours, and acrylonitrile and HCN were separated by distillation. Next, the water content is reduced to 5 wt% or less with caustic soda, and then low-boiling substances are distilled off.
High boiling materials were removed. As a result, the following acetonitrile was obtained.

[Impurities] Allyl alcohol 100 ppm Acrylonitrile 5 ppm Oxazole 50 ppm H ₂ O 500 ppm 1 / 10PH 6.0

[Ultraviolet absorption] Wavelength 200 nm abs = 2.1 Wavelength 220 nm abs = 0.60 Wavelength 250 nm abs = 0.03 Absorbance [abs = absorbance is 10 m
The absorbance value using an m quartz cell is shown. (same as below)〕.

2 liters of acetonitrile as a raw material was placed in a round bottom flask equipped with a stirrer, 98% sulfuric acid was added to acetonitrile in a weight ratio of 20%, and the reaction was carried out at a temperature of 75 ° C. for 30 minutes. . Then 3
Simple distillation was performed under the condition of a reduced pressure of 00 mmHg abs to obtain 1438 g of a fraction. The pot residue was 475 g. The impurities and ultraviolet absorption of the fraction were as follows.

[Impurities] Allyl alcohol 0 ppm Acrylonitrile 5 ppm Oxazole 0 ppm Acetone 0 ppm HCN 0 ppm H ₂ O 500 ppm

[Ultraviolet absorption] Wavelength 200 nm abs = 0.9 Wavelength 225 nm abs = 0.35 Wavelength 250 nm abs = 0.04

The resulting 1400 g was subjected to a contact treatment at 20 ° C. for 5 minutes at 50 NL / Hr with air containing 0.5 vol% of ozone. The impurities and UV absorption were as follows.

[Impurities] Allyl alcohol 0 ppm Acrylonitrile 0 ppm Oxazole 0 ppm Acetone 0 ppm HCN 0 ppm H ₂ O 500 ppm

[Ultraviolet absorption] Wavelength 200 nm abs = 0.09 Wavelength 225 nm abs = 0.3 Wavelength 250 nm abs = 0.04

Using acetonitrile as a raw material, 5
1 mm diameter filled with 200 mm height
After total reflux with a 5 mm atmospheric distillation apparatus, 5% of the initial distillation was removed at a reflux ratio of 2 and the remaining 95% was distilled off. The impurities and ultraviolet absorption of the recovered acetonitrile were as follows: It became so.

[Impurities] Allyl alcohol 0 ppm Acrylonitrile 0 ppm Oxazole 0 ppm Acetone 0 ppm HCN 0 ppm H ₂ O 200 ppm

[UV absorption] wavelength 200 nm abs = 0.03 wavelength 220 nm abs = 0.01 wavelength 250 nm abs = 0.00

COMPARATIVE EXAMPLE 1 The same crude acetonitrile as in Example 1 was used as a starting material and acetonitrile obtained by the same treatment as in Example 1 was used as a raw material. After the reflux, 5% of the initial fraction was removed at a reflux ratio of 2 and the remaining 95% was distilled off. The impurities and ultraviolet absorption of the recovered acetonitrile were as follows.

[Impurities] Acrylonitrile 5 ppm Oxazole 10 ppm H ₂ O 50 ppm

[Ultraviolet absorption] Wavelength 200 nm abs = 2.0 Wavelength 220 nm abs = 0.5 Wavelength 250 nm abs = 0.03

Comparative Example 2: 1400 g of acetonitrile obtained by treating the same crude acetonitrile as in Example 1 in the same manner as in Example 1
Contact treatment was performed at 20 ° C. for 90 minutes at a rate of 50 NL / Hr containing air containing 0.5 vol% of ozone. The impurities and UV absorption were as follows.

[Impurities] Allyl alcohol 0 ppm Acrylonitrile 0 ppm Oxazole 0 ppm Acetone 0 ppm HCN 0 ppm H ₂ O 500 ppm

[Ultraviolet absorption] Wavelength 200 nm abs = 2.80 Wavelength 220 nm abs = 1.3 Wavelength 250 nm abs = 0.2

Using acetonitrile as a raw material, 5
1 mm diameter filled with 200 mm height
After total reflux with a 5 mm atmospheric distillation apparatus, 5% of the initial distillation was removed at a reflux ratio of 2 and the remaining 95% was distilled off. The impurities and ultraviolet absorption of the recovered acetonitrile were as follows: It became so.

[Impurities] Allyl alcohol 0 ppm Acrylonitrile 0 ppm Oxazole 0 ppm Acetone 0 ppm HCN 0 ppm H ₂ O 200 ppm

[UV absorption] wavelength 200 nm abs = 0.12 wavelength 220 nm abs = 0.06 wavelength 250 nm abs = 0.01

COMPARATIVE EXAMPLE 3 Acetonitrile obtained by the same treatment as in Example 1 was used as a raw material, and the mixture was completely refluxed in a 15 mm-diameter atmospheric distillation apparatus packed with a 5 mm Raschig ring at a height of 200 mm. After removing 5% of the first distillate, the remaining 95%
As a result, impurities and ultraviolet absorption of the recovered acetonitrile were as follows.

[Impurities] Allyl alcohol 0 ppm Acrylonitrile 0 ppm Oxazole 0 ppm Acetone 0 ppm HCN 0 ppm H ₂ O 50 ppm

[Ultraviolet absorption] wavelength 200 nm abs = 0.15 wavelength 220 nm abs = 0.05 wavelength 250 nm abs = 0.02

[0043]

According to the present invention, a high-purity acetonitrile used for a liquid chromatography solvent which has been conventionally difficult to obtain industrially can be obtained industrially.
Is big.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C07C 253/34 C07C 255/03

Claims (1)

(57) [Claims] 1. A crude by-product acetonitrile obtained by subjecting propylene or isobutylene to an ammoxidation reaction in the presence of a catalyst is contacted with sulfuric acid, a sulfuric acid component is separated, and then contacted with a gas containing ozone, purification of acetonitrile, wherein the <br/> this distillation.