JPS5953915B2 - Method for producing dichloromaleic anhydride - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing dichloromaleic anhydride.

Dichloromaleic anhydride is a substance useful as a raw material for agricultural chemicals, etc., and is usually produced by directly reacting maleic anhydride and chlorine. However, the reaction mechanism is thought to consist of chlorination and dehydrochlorination reactions shown by the following formula. (1) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Maleic anhydride (2) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (3) Acids Conventionally, anhydrous ferric chloride and anhydrous aluminum chloride have been used as catalysts in the raising reaction, but these catalysts have low yields of dichloromaleic anhydride and require a long time for the reaction.

It is also known to use barium chloride to promote dehydrochlorination, but barium chloride has the drawback of being a negative catalyst for the reaction. For this reason, an excellent method for producing dichloromaleic acid using ferric chloride hexahydrate as a catalyst (Japanese Patent Application Laid-open No. 49-124021),
A method has been proposed in which iron is used and water is added during the chlorination reaction (JP-A-50-52022). However,
If this method is followed, it is expected that the yield of dichloromaleic anhydride will be the same and the reaction time will be shortened, but in the case of the former method, free water and in the case of the latter method, the added water will be in the gas phase of the reactor. Because it coexists with chlorine gas, which is a reaction raw material, and hydrogen chloride gas, which is a reaction by-product, very serious problems can occur in terms of corrosion of the reactor material when carrying out the reaction on an industrial scale. Hard to avoid. The inventors of the present invention have conducted intensive research on a method for obtaining dichloromaleic anhydride in a high yield in a short period of time without such drawbacks, and have found that if fumaric acid is present even in the absence of water or a water source. The inventors have discovered that the present invention can be achieved by not only improving the yield of dichloromaleic anhydride and shortening the reaction time, but also solving the problem of equipment corrosion. That is, the gist of the present invention resides in a method for producing cyclomaleic anhydride, which is characterized by reacting maleic anhydride with chlorine gas in the presence of anhydrous ferric chloride and fumaric acid.

To explain the present invention in more detail, normal maleic anhydride and chlorine gas are used as raw materials, but in order to prevent corrosion of equipment materials and achieve the effects of the present invention, these raw materials must be It is preferable to supply it in an anhydrous state.

The higher the reaction temperature is, the more hydrochloric acid gas produced as a by-product is removed, and the reaction rate becomes faster. ~200℃,
Preferably 120-180°C, optimally 130-170°C
Selected from the range of °C. Particularly when carried out industrially, the first stage reaction of the above reaction mechanism, that is, the reaction until dichlorosuccinic anhydride is produced, is carried out at 130 to 160°C, and the reactions after dehydrochlorination of dichlorosuccinic anhydride are carried out at 150 to 170°C.
It is preferred to select the reaction temperature so that it is carried out at .
Theoretically, 2 moles of chlorine gas are consumed based on maleic anhydride. Although the amount of chlorine gas blown cannot be determined unconditionally since the chlorine utilization rate varies depending on the blown speed and stirring condition, it is usually sufficient if it is about 2.2 to 4.0 times the molar amount of maleic anhydride. As for the blowing rate of chlorine gas, the blowing rate used in the usual chlorination reaction of maleic anhydride is adopted. Regarding reaction time, reaction temperature, chlorine blowing rate, blowing type, stirring type,
It usually takes 3 to 20 hours depending on the stirring speed.It is necessary to use anhydrous ferric chloride as a catalyst, and avoid using hydrated salts as they cause problems such as corrosion of the material as mentioned above. There must be. The amount used is usually 1 to 5% by weight based on maleic anhydride. Therefore, it is necessary to have fumaric acid present during the reaction of the method of the present invention.

Fumaric acid is usually 1 to 15% by weight based on maleic anhydride.
, preferably 3 to 10% by weight. The form of the reaction is not particularly limited, and the reaction is usually carried out in a batch manner without a solvent. A tank-type reactor equipped with a stirrer and made of class lining is usually used as the reactor.

For example, by arranging several such reactors in parallel and introducing chlorine gas from one direction, unreacted chlorine gas is absorbed into the next reaction tank, and after the reaction in the reaction tank to which chlorine gas was first introduced is completed, the chlorine gas is removed. It is preferable to reverse the direction of introduction and conduct the reactions alternately, since this increases the utilization rate of chlorine. Furthermore, according to this method, it is also easy to recover the hydrochloric acid gas that is produced in large amounts as a by-product in the second reaction. To obtain purified dichloromaleic anhydride from the reaction product obtained in this way, ordinary organic chemical methods such as steaming under reduced pressure or normal pressure, and recrystallization using benzene, toluene, chloroform, carbon tetrachloride, etc. will be adopted.

The method of the present invention has been explained in detail above, but if the method of the present invention is followed, there will be no problems such as corrosion of the material of the reactor.
Since dichloromaleic anhydride can be produced in a short time with high yield, it is extremely advantageous in industrial scale implementation.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 300 liters of maleic anhydride, 6 tons of anhydrous ferric chloride, and 15 tons of fumaric acid were heated and melted at 160°C.

A chlorination reaction was carried out by blowing dehydrated chlorine gas into this solution at a rate of 70 tons/body while stirring at 160°C. After 10 hours, the blowing of chlorine gas was stopped, and after heating under reflux for 1 hour to complete the dehydrochloric acid reaction, the reaction product liquid was distilled to obtain B. p. l9
A fraction of 3-197°C was obtained.

The yield was 4767, and as a result of gas chromatography analysis of this fraction, the composition was 98% dichloromaleic anhydride, 1.5% monochloromaleic anhydride, and 0.5% tetrachlorosuccinic anhydride, and the yield was 9. , 1%. Comparative Example 1 The reaction and distillation were carried out in the same manner as in Example 1 without adding fumaric acid, and a fraction of 465V was obtained.

The composition of this fraction was 22% dichloromaleic anhydride. The monochloromaleic anhydride content was 38%, the tetrachlorosuccinic anhydride content was 40%, and the yield was 2096%. Comparative Example 2 The reaction and distillation were carried out in the same manner as in Comparative Example 1 except that dehydrated chlorine gas was blown in at a rate of 15 f/hr for 50 hours, resulting in a fraction of 473 t.

Claims (1)

[Claims] 1. A method for producing dichloromaleic anhydride, which comprises reacting maleic anhydride with chlorine gas in the presence of anhydrous ferric chloride and fumaric acid.