JPS5822013B2 - Production method of xylylene dichloride - Google Patents

Description

[Detailed description of the invention] The present invention provides a method for producing xy'IJ dichloride.

In detail, when producing xylylene dichloride by chlorinating the nuclear substituted methyl group of xylene, xylylene dichloride is produced by irradiating the reaction solution containing xylene and chlorine with ultraviolet light and chlorinating it in the liquid phase. After producing chloride, the xylylene dichloride precipitated as a solid at this time is separated, and unreacted xylene and only one of the methyl groups of the xylene is monochlorinated, or the methyl group is polychlorinated. The present invention relates to a method for producing xylylene dichloride from xylene, characterized in that a mother liquor consisting of xylene is recycled to the reaction process.

The target xylylene dichloride is a dihalide in which two methyl groups of xylene are each monohalogenated as shown by the following structural formula (wherein, X represents a chlorine atom.

) Since each of its nuclear-substituted methyl groups has one reactive chlorine atom, it is useful as an intermediate raw material, and due to its bifunctionality, it can be used as a crosslinking agent for synthetic resins such as polyurethane resins, or as a crosslinking agent for synthetic resins such as polyurethane resins, etc. The present invention has high industrial value because it is extremely useful as an insecticide and the method of the present invention can be applied to its production.

OrganicSynthese is a method for halogenating alkyl aromatic hydrocarbons while irradiating ultraviolet-containing light.
An example of brominating O-xylene is described in sVo 14984-986 (1963).

Further, while irradiating an aromatic hydrocarbon having a side chain methyl group or its halide and a halogen with light, at least (
1) A method of reacting in the presence of boron trifluoride or its active derivative and (2) ammonium halide is described in Japanese Patent Publication No. 40-28788, or a method of reacting in the presence of an alkaline earth metal halide is described. Tokuko Sho 43-825
4 are all known.

However, when these conventional methods for producing halogen derivatives of alkyl aromatic hydrocarbons by irradiation with ultraviolet-containing light are used to produce xylylene dichloride, which is the object of the present invention, undesirable chlorinated products are formed concurrently, It has the disadvantage of poor selectivity in the reaction to xylylene dichloride.

Moreover, since the physical properties of the undesirable chlorinated products are extremely similar to those of the target xylylene dichloride, it is practically extremely difficult to separate only the target xylylene dichloride from the mixture produced in the chlorination reaction. be.

For example, the boiling points of these chlorides are very close, so it is extremely difficult to separate them by distillation, and the melting point of xylylene dichloride is high, so it is difficult to crystallize during distillation and block the pipes of the distillation equipment. It happens.

Furthermore, since p-xylylene chloride and p-chloromethylbenzaldichloride form a eutectic, it is difficult to separate them by crystallization.

Therefore, even if xylylene dichloride is produced in the reaction step by the above-mentioned known method, it has hitherto been an industrial obstacle to economically separate only xylylene dichloride from a mixture of these chlorinated products.

An object of the present invention is to provide a method for producing xylylene dichloride which solves the difficulty of separating and obtaining the xylylene dichloride and improves its yield.

In other words, the production of undesirable chlorinated products can be minimized, extremely pure xylylene dichloride can be economically separated and obtained in solid form from the reaction solution in good yield, and the raw materials xylene and salt can be obtained.

The purpose of the present invention is to provide a method for producing xylylene dichloride that improves the basic unit consumption of xylylene dichloride.

In order to achieve this goal, the inventors applied chlorine to xylene in a liquid phase while irradiating it with ultraviolet light, thereby producing the target xylylene dichloride.

Chlorinated methane has low solubility in solvents, so it precipitates as a solid, unreacted xylene, its monochloride, and those with polychlorinated methyl groups in which one methyl group is substituted with two or more chlorines, etc. It has been found that the undesirable chlorinated substances do not precipitate in the solid state and exist in solution.

In this case, the target xylylene dichloride was separated from the reaction solution by a simple means called solid precipitation, and it was found that the obtained xylylene dichloride contained almost no impurities.

Furthermore, the precipitated mother liquor after separating the xylylene dichloride mentioned above is mainly composed of unreacted xylene and contains nearly saturated dissolved xylylene dichloride and undesirable chlorinated substances, but the mother liquor does not react as it is. It can be recycled to the reactor and subjected to repeated chlorinations with xylene being freshly charged to the reactor as feedstock.

Recirculating the mother liquor will suppress the formation of undesirable chlorinated products in the reactor, so the amount of chlorine charged to act on the newly charged xylene should be adjusted to the desired level of xylene. Add only the chemical equivalent necessary to produce range chloride.

Xylylene dichloride is almost quantitatively obtained in solid form from the nearly saturated reaction solution as it is produced, while undesirable chlorides are dissolved in the reaction solution and maintain their concentration approximately constant. It has been found that it is possible to do so, and thus its generation can be largely avoided.

In the present invention, when producing xylylene dichloride from xylene and chlorine, hydrogen chloride and xylylene dichloride are produced by irradiating 5-xylene with chlorine while irradiating it with ultraviolet light in the liquid phase in the presence of a solvent. After the xylylene dichloride is formed, the xylylene dichloride precipitated as a solid is separated, and the unreacted xylene and the monochlorinated product and polychloromethylated product other than the xylylene dichloride are recycled to the chlorination reaction step. A method for producing xylylene dichloride, characterized by:

The xylene used in the present invention includes 0-xylene, m-xylene, p-xylene, and the like.

Next, in the present invention, chlorine is used.

The effects of the present invention are well exhibited if the amount of chlorine supplied in the reaction step is less than the chemical equivalent required to convert xylene to xylylene dichloride.

Although the method of the present invention is possible without necessarily using a solvent, it is effective if a solvent is used.

The solvent used in the present invention is a chlorinated product of methane.

For example, carbon tetrachloride, chloroform, and especially carbon tetrachloride are effective.

The irradiation with ultraviolet-containing light mentioned here is particularly limited depending on the type of light source, as long as it is irradiated with ultraviolet-containing light emitted from light sources commonly used in this field, such as natural light, mercury arc lamps, hydrogen discharge tubes, flash discharge lamps, etc. Not done.

Further, the reaction temperature used in the present invention is usually from O'C to a temperature below the boiling point of the reaction solution using a solvent.

For example, 10°C to 30°C is suitable.

In addition, for the separation and acquisition of xylylene dichloride in the present invention, methods commonly used in the chemical industry, such as filtration, centrifugation, and sedimentation concentration, are used.

As described above, the method of the present invention has the advantage that the obtained xylylene dichloride has a high purity and also minimizes the production of undesirable chlorinated products, so that the yield of xylylene dichloride is improved.

Next, the present invention will be explained with reference to Examples, but the scope of the present invention is not limited thereby.

Example 1 A reaction solution containing 40.6 g of p-xylene and 240 g of carbon tetrachloride was maintained at 20° C., and 45.3 g of chlorine gas was introduced under ultraviolet irradiation with a 100 W high-pressure mercury arc lamp.

A while after the start of the reaction, crystals of p-xylylene dichloride precipitated and the reaction solution became a slurry.

As a result of analysis by gas chromatography after the completion of the reaction,
Unreacted p-xylene 23.69. 30.7 g of p-xylylene dichloride, 7.8 g of undesirable halogen derivatives
Formation of g was observed.

The yield of p-xylylene dichloride was 45.9.

The amount of crystals of p-xylylene dichloride obtained by furnace separation from this reaction solution was 222 g, and the purity determined by gas chromatography was 94.

Next, in order to apply the method of the present invention, 0.5.9 g of p-xylene, 23.6 g of α-chloro-p-xylene, and 9.8 g of p-xylylene dichloride were obtained by the door-to-door inspection. !
and 7.8 g of undesirable halogen derivatives and 340 y of mother liquor consisting of carbon tetrachloride and 669 y of p-xylene.
75.1 g of chlorine gas was introduced again in the same manner as described above to carry out chlorination.

After the reaction was completed, the presence of 0.6 g of unreacted p-xylene, 60.2 g of alpha-4-4-p-xylene, 668 g of p-xylylene dichloride, and 9.6 g of undesirable halogen derivatives was observed.

The amount of p-xylylene dichloride obtained by furnace separation from this reaction solution was 58.8 g, and the purity was 96.

The yield of p-xylylene dichloride to p-xylene is 58.8 x O, 96x 106.2, □xlOO = 51. ．． It was 2 175.07 x 67.4.

Example 2 A reaction solution of 65 g of 0-xylene and 250 g of carbon tetrachloride was
The temperature was maintained at 0° C., and 59.9 g of chlorine gas was introduced while irradiating ultraviolet light with a 100 W high-pressure mercury arc lamp.

As a result of analysis by gas chromatography after the completion of the reaction,
The production of 38.9 g of α-4-4-0-xylene, 37.5 g of 0-xylylene dichloride, and 7.9 g of undesirable halogen derivatives was observed.

Next, 50.1 g of 0-xylene was added to 292 g of a mother liquor consisting of 360 g of α-chloro-o-xylene, 12.5 g of 0-xylylene dichloride, 7.5 g of undesirable halogen derivatives, and carbon tetrachloride obtained from each house. 9 was added, and chlorine gas 61.5.9 was introduced again in the same manner as in Example 1 to carry out chlorination.

After completion of the reaction, 39.7 g of α-chloro-〇-xyleno, 0
- 63.6 g of xylylene dichloride, 27.1 i of undesired halogen derivatives were observed.

The amount of 0-xylylene dichloride obtained from this reaction solution was 47.5 g, and the purity was 96%.

Claims (1)

[Claims] 1. When producing xylylene dichloride from xylene and chlorine, chlorine is added to the xylene by irradiating ultraviolet-containing light in the liquid phase using a chlorinated product of methane as a solvent. After reacting to form hydrogen chloride and xylylene dichloride, the xylylene dichloride precipitated as a solid is separated, and unreacted xylene and the xylylene dichloride are separated. characterized in that monochlorides and polychlorides other than loride are recycled to the halogenation reaction step,
A method for producing xylylene dichloride.