CN111320554A - Improved technology of monomethylhydrazine production process - Google Patents

Abstract

An improved technology for the production of monomethyl hydrazine, based on the hydrochloric acid methanol hydrazine hydrate method, an improved process is invented to solve the problem of many by-products, low reaction yield, reaction The disadvantages such as environmental pollution caused by the formation of highly toxic polyhydrazine in the liquid, avoid the further methyl diversification of the target product-methylhydrazine first produced in the reaction process, ensure the single production of the target product, and more importantly The advantages are process simplification, environmental protection, improved yield and reduced cost.

Description

A kind of technology for improving the production process of monomethyl hydrazine

technical field

The invention relates to the field of organic synthesis, in particular to a new process technology for improving the synthesis process for industrial production of monomethylhydrazine and establishing clean production of target products

Background technique

Monomethylhydrazine is widely used in medicine, pesticides and dyes. Because of its low freezing point, good thermal stability and stable combustion process, it is considered as a very valuable compound in various industries such as aerospace and missiles. The production volume of this raw material is also increasing continuously. my country is also a big producer of monomethyl hydrazine, and its annual output ranks among the top in the world.

There are many reports on the synthetic method of methyl hydrazine. At present, the synthetic methods of existing literature mainly include the following:

Chloramine method

Patent US4192819 firstly disclosed the process of synthesizing methylhydrazine by chloramine method, mainly using sodium hypochlorite and ammonia to react to generate chloramine, and then reacting chloramine with monomethylamine to generate methylhydrazine. Although this technology is mature,

However, the subsequent separation of this route is difficult, the energy consumption of the production process is high, and the equipment cost is high.

Hydrazine hydrate benzaldehyde condensation method

Use hydrazine hydrate as raw material to react with benzaldehyde to generate benzylidene azide, then add dimethyl sulfate to generate methyl hydrazine sulfate, which is neutralized and rectified by sodium ethoxide. The product yield is 60% to 70%. However, the cost of the whole reaction raw materials is relatively high, the reaction process is relatively complicated, the production energy consumption is relatively large, and the odor in the production process is relatively large, which is not conducive to industrialized production.

Dimethyl sulfate hydrazine hydrate method

Patent CN101402586A discloses a method of using hydrazine hydrate and dimethyl sulfate with hydrochloric acid as a protective agent, and tetrabutylammonium bromide as a catalyst to generate methylhydrazine sulfate at 115-125 ° C, and then under the free condition of strong alkali sodium hydroxide. The desired methylhydrazine solution is obtained by rectification and separation.

This method has the advantages of easy availability of raw materials, low price, fast reaction speed and high yield. However, dimethyl sulfate is highly toxic and has potential safety hazards, and at the same time, a large amount of intractable sodium salt will remain after the dissociation, which undoubtedly increases the cost of sodium salt treatment and brings very troublesome environmental protection problems. Therefore, this process is difficult to industrialize. Production.

Hydrochloric acid methanol hydrazine hydrate method

In recent years, Japan Hydrazine Co., Ltd. has proposed a new process for producing methyl hydrazine. In the patent JP8298247, it is disclosed a reaction of hydrazine monohydrochloride and methanol, using hydrazine dihydrochloride or methyl chloride as a catalyst to generate methyl hydrazine at high pressure and a certain temperature. hydrazine hydrochloride, then the methyl hydrazine is freed by the method of alkali freeing, and finally the methyl hydrazine is distilled out by the rectification method. This method has cheap raw materials and high product selectivity. But the disadvantage is that the reaction yield is not high, only about 30%, and the reaction is carried out in a high-pressure anti-corrosion reaction kettle, the equipment investment is large, and the cost is high.

The domestic production of monomethylhydrazine (MMH) mainly adopts the above-described two synthesis processes: the ammonia chloride method or the hydrochloric acid methanol hydrazine hydrate method. At present, the most mature and widely used method is the hydrochloric acid methanol hydrazine hydrate method. The main technological process is as follows: using methanol and hydrazine hydrate as raw materials, using hydrochloric acid and methyl chloride as catalysts, and preparing monomethylhydrazine under the pressure of 0.7-1.3Mpa. Several existing production enterprises in my country generally use this process (patent CN102516117A). ), the advantages of this process are that the raw materials are easily available, the relative cost is low, etc., and the disadvantages are that the by-products are many, the yield of monomethylhydrazine is low and the methylation of hydrazine is not well controlled, etc., a large amount of by-products generated by this process such as partial di Methylhydrazine (UDMH), 1,2-dimethylhydrazine (1,2-DMH) and other highly toxic derivatives of hydrazine hydrate, by-products such as asymmetric dimethylhydrazine (UDMH), 1,2-dihydrazine The formation of methylhydrazine (1,2-DMH) and other highly toxic derivatives of hydrazine hydrate complicates the components of the entire reaction system, resulting in great difficulty in subsequent separation, high energy consumption in the production process, low yield and therefore high production cost. The production plant releases thousands of tons of such waste liquids for treatment every year. They are highly toxic and flammable substances, and their vapor and air can form explosive mixtures, which are easily combustible and exploded or decompose into highly toxic gases when exposed to fire and high heat. Therefore, the recovered waste liquid can only be incinerated or decomposed by incinerators, which not only pollutes the environment, but also wastes resources.

Aiming at the problems existing in the prior art, the present invention provides a new process for the technical improvement of the hydrochloric acid methanol hydrazine hydrate method to make the operation safe, the yield increased and the environmental protection, and the synthesis process for synthesizing methyl hydrazine in the original hydrochloric acid methanol hydrazine hydrate method Based on this, a new technical method is provided. The inventive method is most suitable for large-scale industrial production.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an improved process technology based on the hydrochloric acid methanol hydrazine hydrate method to solve the shortcomings such as many by-products and low reaction yield when synthesizing monomethyl hydrazine by the hydrochloric acid methanol hydrazine hydrate method at present, and prevent the reaction liquid from being violent in the reaction solution. For the purpose of environmental pollution caused by the formation of toxic polyhydrazine, improving yield and reducing cost, a redox control method was invented for the reaction mixture realized by using methyl chloride as a catalyst in the reaction of hydrochloric acid methanol hydrazine hydrate method. The single formation of monomethylhydrazine (MMH) has high selectivity and prevents the by-products of polyhydrazine compounds from being restored, and a new clean production process for the target product, monomethylhydrazine, is established. The main advantage of the present invention is that the process effectively controls side reactions, and the reactants are separated by simple distillation and other processes to obtain monomethylhydrazine with high purity, which improves the yield and reduces environmental pollution; greatly improves the production efficiency. Safety and reduced production costs.

The technical scheme of the present invention is: a kind of improvement method of monomethylhydrazine production technology, comprises the following steps:

A compound salt is obtained by adding an oxidant to the reaction mixture realized by using methyl chloride as a catalyst in the reaction of hydrochloric acid methanol hydrazine hydrate method, and stirring and heating the reaction mixture to obtain a composite salt. The high concentration of monomethylhydrazine aqueous solution is obtained by rectification.

1. The composition is as follows: the molecular formula of monomethylhydrazine is: CH ₃ NHNH ₂ ; the oxidant is one of concentrated sulfuric acid, nitric acid, sodium percarbonate, Cu ²⁺ and potassium iodate.

The reducing agent is one of hydrogen sulfate, ammonia, sodium hydrogen sulfite, sodium sulfite, sulfur dioxide and iron sulfite.

The acidic compound is one of citric acid, SO ₂ , CO ₂ , sulfuric acid, phosphoric acid, nitric acid, oxalic acid and acetic acid.

The alkaline neutralizer is one of ammonia water (or ammonia gas), hydrazine hydrate, sodium hydroxide, sodium carbonate, sodium bicarbonate and calcium oxide.

2. Composition ratio: the molar ratio of the oxidant and the reaction solution is (0.1～1.3): 1; the concentration of the acid compound is 2～38% or pure acid gas; the alkali concentration used for neutralization is 10～40%. % or use a solid basic compound, the solution is adjusted to pH 6.5-11.0; the reaction time is 0.5-5 hours at a constant temperature of 5-80°C.

The technological process is: adding methyl chloride as a catalyst in the reaction of hydrochloric acid methanol hydrazine hydrate method reaction mixture---oxidation reaction---neutralization---suction filtration---addition of reducing agent and rectification---high concentration monomethyl Hydrazine aqueous solution.

Technical effect: the technical effect of the present invention is to adopt the above technical scheme to avoid further methyl diversification of the target product monomethylhydrazine first generated in the reaction process, ensure the single production of the target product, and more importantly, the process is simple, Environmentally friendly, increased productivity and reduced costs.

The method of the present invention will now be described in detail, with reference to the following examples, which will help to understand the present invention, but these examples are only for the purpose of illustrating the present invention and the present invention is not limited to these contents.

Detailed ways

Example 1

125g (2.0mol) of 80% hydrazine hydrate was slowly added dropwise to 192.1g (2.0mol) of 38% concentrated hydrochloric acid, and the temperature was controlled at 20-30°C under stirring for 2 hours. After the reaction was completed, adjust pH=6-7 In between, the water was distilled off in vacuo, the obtained hydrazine hydrochloride was mixed with 96 g (3 mol) of methanol, the reaction temperature was raised to 85° C. and condensed and refluxed for 2-3 h. The reacted mixed solution is distilled to separate methanol and a small amount of water, and the methanol can be recycled. The remaining residual liquid was added to 136.0 g of hydrazine hydrate with a mass fraction of 80% for freeing, and the liquid reaction mixture was analyzed to obtain the following results: Selective methyl hydrazine: 94.0%; Selective 1,1-dimethyl hydrazine Hydrazine: 3.7%; selectivity: 1,2-dimethylhydrazine rate: 2.1%; selectivity: 1,1,1-trimethylhydrazine rate: 0.3%. Finally, the dissociated solution was heated for rectification, and the fraction at 102-110° C. was collected to obtain 87.0 g. The content of methyl hydrazine in gas phase detection was 34.3%. The remaining residue is added with hydrochloric acid to form a hydrazine hydrochloride salt, which is returned to the methylation step for recycling.

Example 2

125g (2.0mol) of 80% hydrazine hydrate was slowly added dropwise to 192.1g (2.0mol) of 38% concentrated hydrochloric acid, and the temperature was controlled at 20-30°C under stirring for 2 hours. After the reaction was completed, adjust pH=6-7 In between, the water was removed by vacuum distillation, the obtained hydrazine hydrochloride was mixed with 96g (3mol) methanol, the reaction temperature was raised to 85°C and condensed and refluxed for a period of time, and the monochloromethane was slowly introduced into the mixed solution to react for 2-3h . The reacted mixed solution is distilled to separate methanol and a small amount of water, and the methanol can be recycled. The remaining residual liquid was added to 136.0 g of hydrazine hydrate with a mass fraction of 80% for freeing, and the liquid reaction mixture was analyzed to obtain the following results: Selective methyl hydrazine: 96.0%; Selective 1,1-dimethyl hydrazine Hydrazine: 1.3%; selectivity 1,2-dimethylhydrazine: 0.8%; selectivity 1,1,1-trimethylhydrazine rate: 0.7%. Finally, the solution was heated for rectification, and the fraction at 102 to 110° C. was collected to obtain 96.3 g, and the content of methyl hydrazine in gas phase detection was 45.0%. The remaining residue is added with hydrochloric acid to form a hydrazine hydrochloride salt, which is returned to the methylation step for recycling.

Example 3

125g (2.0mol) of 80% hydrazine hydrate was slowly added dropwise to 192.1g (2.0mol) of 38% concentrated hydrochloric acid, and the temperature was controlled at 20-30°C under stirring for 2 hours. After the reaction was completed, adjust pH=6-7 In between, the water was removed by vacuum distillation, the obtained hydrazine hydrochloride was mixed with 96g (3mol) methanol, the reaction temperature was raised to 85°C and condensed and refluxed for a period of time, and the monochloromethane was slowly introduced into the mixed solution to react for 2-3h . The reaction mixture was added to the mixed solution of sulfuric acid and sodium percarbonate for stirring, and the compound salt obtained after the reaction temperature was kept constant for 1 hour at 60 °C was added to the solution after CaO analysis, precision filtration, and a small amount of sodium sulfite was added to the filtrate. The liquid reaction mixture was analyzed and the following results were obtained: selectivity for methylhydrazine: 99.9%; selectivity for 1,1-dimethylhydrazine: 0.1%; selectivity for 1,2-dimethylhydrazine: 0%; selectivity 1,1,1-trimethylhydrazine rate: 0%. Finally, the solution was heated for rectification, and the fraction at 102-110° C. was collected to obtain 99.3 g, and the content of methyl hydrazine in gas phase detection was 44.6%. The remaining residue is added with hydrochloric acid to form a hydrazine hydrochloride salt, which is returned to the methylation step for recycling.

Example 4

125g (2.0mol) of 80% hydrazine hydrate was slowly added dropwise to 192.1g (2.0mol) of 38% concentrated hydrochloric acid, and the temperature was controlled at 20-30°C under stirring for 2 hours. After the reaction was completed, adjust pH=6-7 In between, the water was removed by vacuum distillation, the obtained hydrazine hydrochloride was mixed with 96g (3mol) methanol, the reaction temperature was raised to 85°C and condensed and refluxed for a period of time, and the monochloromethane was slowly introduced into the mixed solution to react for 2-3h . The reaction mixture was added to the mixture of sulfuric acid and sodium peroxycarbonate and stirred, and the compound salt obtained after the reaction temperature was kept constant for 1 hour at 60 ° C was added to CaO and analyzed. The liquid reaction mixture was analyzed, and the following results were obtained: Selective methyl hydrazine: 99.1%; selectivity 1,1-dimethylhydrazine: 0.9%; selectivity 1,2-dimethylhydrazine rate: 0.1%; selectivity 1,1,1-trimethylhydrazine rate: 0%. The solution after precision filtration was heated and rectified, and the fraction at 102-110° C. was collected to obtain 98.1 g, and the content of methyl hydrazine in gas phase detection was 42.0%. The remaining residue is added with hydrochloric acid to form a hydrazine hydrochloride salt, which is returned to the methylation step for recycling.

Example 5

125g (2.0mol) of 80% hydrazine hydrate was slowly added dropwise to 192.1g (2.0mol) of 38% concentrated hydrochloric acid, and the temperature was controlled at 20-30°C under stirring for 2 hours. After the reaction was completed, adjust pH=6-7 In between, the water was removed by vacuum distillation, the obtained hydrazine hydrochloride was mixed with 96g (3mol) methanol, the reaction temperature was raised to 85°C and condensed and refluxed for a period of time, and the monochloromethane was slowly introduced into the mixed solution to react for 2-3h . The reaction mixture was added to the mixed solution of sulfuric acid and sodium percarbonate and stirred. After the reaction temperature was kept constant for 1 hour at 60°C, the compound salt obtained was added with 80% hydrazine hydrate for analysis, precision filtration, and a small amount of sodium sulfite was added to the filtrate to mix the solution at 50°C. After 15 minutes of constant temperature, the liquid reaction mixture was analyzed, and the following results were obtained: selectivity of methyl hydrazine: 99.7%; selectivity of 1,1-dimethylhydrazine: 0.15%; selectivity of 1,2-dimethylhydrazine: 0 %; Selectivity of 1,1,1-trimethylhydrazine: 0%. After rectification, the fractions at 102-110°C were collected to obtain 98.0 g, and the content of methyl hydrazine in gas phase detection was 41.4%. The remaining residue is added with hydrochloric acid to form a hydrazine hydrochloride salt, which is returned to the methylation step for recycling.

Claims (2)

1. a monomethylhydrazine production technique improvement technology, it is characterized in that: for the reaction mixture that is realized with methyl chloride as a catalyst in the hydrochloric acid methanol hydrazine hydrate method reaction, add a kind of acid mixture of oxidant and stir and heat reaction to obtain a The compound salt is subjected to alkaline analysis, precision filtration, adding a trace amount of reducing agent to the filtrate and mixing, and then rectifying to obtain a high-concentration monomethylhydrazine aqueous solution. 2. a kind of monomethylhydrazine production technique improvement technology according to claim 1, is characterized in that: described oxygenant is a kind of in the vitriol oil, nitric acid, sodium percarbonate, Cu ²⁺ and potassium iodate , the reducing agent is a kind of hydrogen sulfate, ammonia, sodium hydrogen sulfite, sodium sulfite, sulfur dioxide and iron sulfite, and the acid compound is citric acid, SO ₂ , CO ₂ , sulfuric acid, phosphoric acid, nitric acid , a kind of in oxalic acid and acetic acid, described alkaline neutralizing agent is a kind of in ammoniacal liquor (or ammonia gas), hydrazine hydrate, sodium hydroxide, sodium carbonate, sodium bicarbonate and calcium oxide, composition ratio: all The molar ratio of the oxidant and the reaction solution is (0.1～1.3): 1, the concentration of the acid compound is 2～38% or pure acid gas, and the alkali concentration used in neutralization is 10～40% or solid alkaline The compound, the solution is adjusted to PH6.5-11.0, the constant temperature is 5～80℃, and the reaction time is 0.5～5 hours. The technological process is: adding methyl chloride as a catalyst in the reaction of hydrochloric acid methanol hydrazine hydrate method reaction mixture---oxidation reaction--- Neutralization---suction filtration---add reducing agent and rectification---obtain high-concentration monomethylhydrazine aqueous solution.