JPH0239502B2 - MONOMECHIRUHIDORAJINNOKAISHUHOHO - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for recovering monomethylhydrazine from a reaction solution in a monomethylhydrazine manufacturing process. Monomethylhydrazine is an extremely useful industrial chemical for the production of pharmaceuticals, agricultural chemicals, and the like. Conventionally, known methods for producing monomethylhydrazine include the so-called modified Raschzig method, in which monomethylamine is reacted with chloramine obtained by the reaction of ammonia and sodium hypochlorite, and the alkylation method of hydrazine with methyl halide. . However, in the former method, the yield of monomethylhydrazine produced is poor and the concentration in the reaction product solution is extremely low, so a large amount of energy is required to extract the target product. In addition, the latter produces a large amount of by-products such as asymmetric dimethyl hydrazine, symmetric dimethyl hydrazine, and trimethyl hydrazine in addition to the desired monomethyl hydrazine, so the separation and purification process of the desired product is complicated and the yield is low. low. For this reason, none of the conventional methods was satisfactory as an industrial manufacturing method. The present inventors first prepared hydrazine dihydrochloride or methyl chloride from hydrazine monohydrochloride, which is easily obtained from hydrazine and hydrochloric acid, which are industrial basic materials, as well as inexpensive methanol, which is industrially mass-produced. We have invented an innovative production method that allows monomethylhydrazine to be easily obtained with extremely high selectivity by carrying out a heated reaction in the presence of a chemical reaction, and a method for recovering monomethylhydrazine from the reaction product, and are currently applying for a patent. be. (Special application 1982-
173116). In the method of the invention, when monomethylhydrazine is obtained with high selectivity, the conversion rate of hydrazine monohydrochloride is about 30% or less, so in addition to monomethylhydrazine hydrochloride, unreacted hydrazine is contained in the reaction product solution. Monohydrochloride, methanol, water, etc. remain. In order to extract monomethylhydrazine from this reaction solution, we focused on the difference in the solubility of monomethylhydrazine hydrochloride and hydrazine monohydrochloride in methanol. A method was invented in which methanol was added to dissolve monomethylhydrazine hydrochloride, hydrazine hydrochloride insoluble in methanol was separated, the separated mother liquor was neutralized by adding an alkali such as caustic soda, and the liberated monomethylhydrazine was recovered by distillation. It was a method. The method of the invention described above is extremely convenient because the separated hydrazine monohydrochloride can be recycled as it is as a raw material for the next reaction. However, after expelling methanol and water from the reaction solution, new methanol must be added, and in order to liberate monomethylhydrazine from the hydrochloride, an alkali is added to the mother liquor after the separation of hydrazine monohydrochloride. Since it requires a step of mixing, common salt is produced from monomethylhydrazine hydrochloride and slightly dissolved hydrazine monohydrochloride, and it also has the disadvantage that it also requires an operation to separate and remove it. The present inventors, while conducting various research on methods for improving these drawbacks and more economically extracting monomethylhydrazine from the reaction product solution through easier operations, discovered that after distilling off a certain amount of water from the reaction solution, They discovered that monomethylhydrazine could be quantitatively distilled out by adding hydrazine hydrate to the residual liquid and distilling the mixture, and as a result of extensive research, they completed the present invention. The present invention is characterized in that hydrazine is added to a reaction solution containing monomethylhydrazine hydrochloride obtained by reacting hydrazine monohydrochloride and methanol in the presence of hydrazine hydrochloride or methyl chloride, and then distilled. , a method for recovering monomethylhydrazine. In the present invention, hydrazine added to the reaction solution is preferably 100% hydrated hydrazine. The amount of hydrazine hydrate to be added is preferably in the range of 1.2 to 2.0 moles relative to the number of moles of hydrochloric acid present in the reaction solution. The distillation method may be either a batch method or a continuous method, but the heating temperature of the reaction solution is preferably 120° C. or lower. According to the method of the present invention, the process is simpler than the previous method in which hydrazine monohydrochloride is separated and removed as crystals, neutralized with alkali, and then distilled, and the process is simpler, and The residual solution can be adjusted to a hydrochloride salt by adding hydrochloric acid and reused in the next reaction. Furthermore, in addition to monomethylhydrazine, a portion of hydrated hydrazine can also be recovered during distillation. The method of the present invention will be explained below with reference to Examples. Example 1 A predetermined amount of methanol was added to a 50% aqueous solution of hydrazine hydrochloride, and the resulting reaction solution was concentrated to distill off most of the water. Add 100% hydrazine hydrate to
Continuous distillation was carried out under a reduced pressure of 100 mmHg using a vacuum cleaner (with a jacket and passing steam at 100°C through the jacket). The compositions of the distillate and bottoms were analyzed and the results are shown in Table 1. According to Table 1, the recovery rate of monomethylhydrazine is
It is 97.7%.

【table】

[Table] Example 2 After concentrating the reaction solution in the same manner as in Example 1, it was distilled batchwise using a still with a packed column. The packed tower has an inner diameter of 15 mm, a height of 600 mm, and a pressure of 200 mm.
It was operated under reduced pressure of Hg, and the temperature of the reactor was 100 to 120°C. The analysis results are shown in Table 2. From the results in Table 2, the recovery rate of monomethylhydrazine was 95.5%. If the distillate is further rectified, pure monomethylhydrazine can be obtained.

[Table] * The symbols in the compound name column of Table 2 are the same as in Table 1.

Claims (1)

[Claims] 1 Monomethyl hydrazine, which is characterized in that hydrazine is added to a reaction solution containing monomethylhydrazine hydrochloride obtained by reacting hydrazine monohydrochloride and methanol in the presence of hydrazine dihydrochloride or methyl chloride, and then distilled. How to recover hydrazine.