JP2002255871A - Method for purifying 1,2-dichloroethane and purified 1,2- dichloroethane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for purifying 1,2-dichloroethane by which trichloroethylene present as an impurity can be efficiently removed, and further to provide the highly pure 1,2-dichloroethane obtained by the purification method. SOLUTION: The 1,2-dichloroethane containing the trichloroethylene as the impurity is chlorinated in the absence of a chlorination catalyst, especially an iron-based chlorination catalyst to reduce the content of the trichloroethylene, and optionally purifying the resultant product by distillation to prepare the 1,2-dichloroethane regulated so that the amount of the trichloroethylene may be at most the limit of detection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for removing impurities present in 1,2-dichloroethane, in particular, trichloroethylene, to obtain purified 1,2-dichloroethane containing less impurities, and a process for producing the same. 1,2-high purity with low trichlorethylene content
It relates to dichloroethane and belongs to the chemical production technology.

[0002]

2. Description of the Related Art 1,2-Dichloroethane is obtained by a method of chlorinating ethylene in the presence of a catalyst such as iron chloride or a method of reacting ethylene and hydrochloric acid in the air. It is a chemical that is widely used as a raw material for manufacturing or as a solvent, and is manufactured in large quantities.

When 1,2-dichloroethane is produced by reacting ethylene and hydrochloric acid in the air, various chlorides, for example, trichloroethylene, 1,1,2
1,2-trichloroethane, tetrachloroethane (sy
It is well known that m- and asym-), pentachloroethane and the like are by-produced.

[0004] Also, 1,2-dichloroethane produced by a method of reacting ethylene and hydrochloric acid in the air usually has a composition as shown in Table 1 below, so that it contains less impurities. When purified 1,2-dichloroethane is required, it is supplied after removing the impurities contained in the components by distillation.

[0005]

[Table 1]

However, the boiling point of trichlorethylene (boiling point 87 ° C .; 760 mmHg) in the impurities is 1,2.
-Dichloroethane (boiling point 83.7 ° C; 760 mmHg)
, And since both components form an azeotropic composition, it is industrially economical to remove completely (below the detection limit) by distillation, as is clear from Table 2 below. However, 1,2-dichloroethane having a large amount of trichloroethylene is regarded as a problem depending on the use.

[0007]

[Table 2]

On the other hand, in order to remove impurities in 1,2-dichloroethane, a method of removing impurities after chlorination, for example, Japanese Patent Publication No. 54-3846 and Japanese Patent No. The impurities remaining in unreacted 1,2-dichloroethane, generated by thermal decomposition, or originally present in the unreacted 1,2-dichloroethane, were produced by fermentation of 2-dichloroethane to produce vinyl chloride.
l ₃ ) A method for removing by chlorination using a catalyst is disclosed.

However, these prior arts do not suggest the possibility of removing a trace amount of trichlorethylene present in 1,2-dichloroethane, but rather pose a problem of necessity of treating wastewater with an iron chloride catalyst. To be generated.

[0010]

Under such circumstances, the inventors have found that trichloroethylene, which is a trace impurity present in 1,2-dichloroethane produced by reacting ethylene and hydrochloric acid in air. To provide more purified 1,2-dichloroethane.

As a result, the inventors have found that trichlorethylene, which is present in a trace amount in 1,2-dichloroethane produced by reacting ethylene and hydrochloric acid in the air, is almost completely chlorinated under certain conditions. By disappearing and further distilling it, 1,2 has been completely removed (below the detection limit) of trichloroethylene.
-It was found that dichloroethane was obtained, and the present invention was completed.

[0012]

That is, according to the first aspect of the present invention, 1,2-dichloroethane containing trichloroethylene as an impurity is chlorinated in the absence of a chlorination catalyst to contain trichloroethylene. A method for purifying 1,2-dichloroethane, characterized in that the purification is carried out in a reduced amount.

According to a second aspect of the present invention, 1,2-dichloroethane containing trichlorethylene as an impurity is chlorinated in the absence of an iron-based chlorination catalyst to reduce the content of trichloroethylene and to purify the same. A method for purifying 1,2-dichloroethane.

Further, the invention according to claim 3 is characterized in that the content of trichloroethylene is reduced by the method for purifying 1,2-dichloroethane according to claim 1 or 2, -Dichloroethane.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS For chlorination of 1,2-dichloroethane, a normal chlorination technique of contacting 1,2-dichloroethane with chlorine, such as blowing chlorine into liquid 1,2-dichloroethane, is applied. However, in the present invention,
What is important is that an iron-based chlorination catalyst, which is generally effective for the reaction of a compound having a double bond, such as a chlorination catalyst such as iron chloride, is not used.

As a specific chlorination reaction, liquid 1,
In the case of a reaction mode in which chlorine is blown into 2-dichloroethane, the reaction temperature is usually in the temperature range of 40 to 120 ° C, preferably at a high temperature exceeding 85 ° C within the above temperature range, and the pressure is reduced to normal pressure. At 0.9 MPa, chlorine is blown into liquid 1,2-dichloroethane at a molar ratio to 1,2-dichloroethane of 0.05 to 0.5, and the reaction is continued while analyzing the amount of trichloroethylene. .

When the reaction is carried out under the above conditions,
The amount of trichlorethylene in 1,2-dichloroethane contained in 0.1 to 0.5 wt% can be almost ignored, that is, the content can be reduced to 0.001 wt% or less.

Since the obtained 1,2-dichloroethane contains chlorides other than trichloroethylene, if necessary, a low-boiling distillation column for removing low-boiling impurities and a high-boiling impurity are removed. Can be removed by a normal distillation operation performed using a high-boiling distillation column.

[0019]

[Effect] Ethylene and hydrochloric acid are reacted in air to form 1,2-
The production of dichloroethane is carried out on a large industrial scale, and chlorination technology has been proposed as a means for removing impurities in 1,2-dichloroethane.
In the chlorination using iron chloride to remove trichlorethylene, which is an impurity present in 2-dichloroethane, trichlorethylene is chlorinated to pentachloroethane, but trichloroethylene in 1,2-dichloroethane disappears. Strictly, about 500 to 1500 ppm of trichlorethylene remains.

However, when 1,2-dichloroethane containing chloride is chlorinated without using an iron-based chlorination catalyst such as iron chloride, chloride other than trichloroethylene, for example,
Despite the increase in trichloroethane, tetrachloroethane and pentachloroethane, trichloroethylene disappears.

According to the predictions of the present inventors, iron chloride and the like used for the chlorination catalyst also contribute to the chlorination reaction, but also to the decomposition reaction of chloride, that is, the decomposition reaction of tetrachloroethane. This is probably because tetrachlorethane is decomposed to produce trichloroethylene as the amount of tetrachloroethane increases due to chlorination.

[0022]

EXAMPLE 1 In a 3-liter glass reactor equipped with a stirrer, 1,2-dichloroethane containing impurities in the amounts shown in Table 3 below.
5 kg was charged, the temperature of the solution was maintained at 50 ° C., and chlorine was added to the solution while stirring (at 200 rpm) to 0.13 (molar ratio:
(1,2-dichloroethane) was blown and the reaction was carried out for 15 hours.

[0023]

[Table 3]

As a result of analyzing the composition of the obtained reactant by gas chromatography, as shown in Table 4 below, the amount of trichlorethylene was so small that it did not matter.

[0025]

[Table 4]

Even when the reaction conditions, that is, 1,2-dichloroethane having different impurity contents, the reaction temperature, the amount of chlorine, the reaction time, and the like are changed within a certain range, the obtained 1,2 is obtained.
-Dichloroethane had a composition falling within the following range.

[0027]

[Table 5]

In order to remove chloride in 1,2-dichloroethane having the composition shown in the above range, distillation was carried out under ordinary conditions using a low-boiling distillation column and a high-boiling distillation column. 1,2-Dichloroethane having the composition shown in Table 6 could be obtained.

[0029]

[Table 6]

Comparative Example 1 A reaction obtained by performing a chlorination reaction in the same manner as in Example 1 except that iron chloride (FeCl ₃ ) was added to 1,2-dichloroethane at a concentration of 2000 ppm as a catalyst. The product had the following composition and a non-negligible amount of trichlorethylene was present.

[0031]

[Table 7]

As in Example 1, even when the reaction conditions are changed within a certain range, the obtained 1,2-dichloroethane is
As shown in Table 8 below, trichlorethylene cannot be eliminated, and even if the above-mentioned distillation operation is performed, the amount of trichloroethylene in the obtained 1,2-dichloroethane is as shown in Table 9. Did not change.

[0033]

[Table 8]

[0034]

[Table 9]

EXAMPLES 2-3 In a stainless steel cylindrical reactor having an inner diameter of 50 mm, 2,2-dichloroethane containing impurities used in Example 1 was added in an amount of 2%.
It was supplied at a rate of 2.5 kg / Hr, and the chlorine was in a molar ratio of 0.104 (Example 2) to 1,2-dichloroethane of 0.089.
(Example 3), and the reaction temperature was 88 ° C. (Example 2) by passing hot water or steam through the jacket.
The temperature was maintained at 115 ° C. (Example 3), and the reaction was carried out for 1 hour while maintaining the internal pressure at 0.68 MPa with nitrogen (pressure 1.2 MPa). Table 10 shows the component composition of the obtained 1,2-dichloroethane.

[0036]

[Table 10]

[0037]

According to the present invention, trichloroethylene present in 1,2-dichloroethane and which cannot be separated and removed by distillation can be reduced to a negligible amount, and 1,2-dichloroethane is used. In this case, 1,2-dichloroethane which can be provided as a completely problem-free product even in applications where the presence of trichlorethylene is problematic can be easily prepared.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukio Shimazu 575-1 Nakajima, Kawauchi-cho, Tokushima City, Tokushima Prefecture Toa Gosei Co., Ltd. Tokushima Plant (72) Inventor Fumio Yusa 575-1, Nakajima, Kawauchi-cho, Tokushima City, Tokushima Toa F-term (reference) in Tokushima Plant of Synthetic Corporation 4H006 AA02 AD31 BE20

Claims (3)

[Claims] 1. A method for producing 1,2-dichloroethane, comprising purifying 1,2-dichloroethane containing trichloroethylene as an impurity by reducing the content of trichloroethylene by chlorination in the absence of a chlorination catalyst. Purification method. 2. The method for purifying 1,2-dichloroethane according to claim 1, wherein the chlorination catalyst is an iron-based chlorination catalyst. 3. A purified 1,2-dichloroethane having a reduced trichloroethylene content by the method for purifying 1,2-dichloroethane according to claim 1 or 2.