阅读说明：本技术 一种微分环流连续化生产原乙酸三甲酯的方法 (Method for producing trimethyl orthoacetate through differential circulation and continuous production ) 是由 邱振中 汪美贞 *** 于 2020-06-09 设计创作，主要内容包括：本发明提供一种微分环流连续化生产原乙酸三甲酯的方法,其特征在于：包括以下步骤：吸收冷却、成盐反应、中和反应、醇解反应、膜法分离、精馏,本发明采用DMI作为溶剂,提高了盐酸盐的收率,成盐质量好；利用膜法分离技术实现了固液分离,提高产品得率；采用微分环流管式反应装置,可连续化生产,加快反应速度,提高生产效率；采用负压精馏法分离原乙酸三甲酯,产品纯度高,塔釜溶剂可循环利用,无废水产生,非常环保。(The invention provides a method for producing trimethyl orthoacetate by differential circulation and continuity, which is characterized by comprising the following steps: the method comprises the following steps: the method adopts DMI as a solvent, improves the yield of hydrochloride, and has good salification quality; solid-liquid separation is realized by utilizing a membrane separation technology, and the product yield is improved; the differential circulation tube type reaction device is adopted, so that continuous production can be realized, the reaction speed is increased, and the production efficiency is improved; the trimethyl orthoacetate is separated by adopting a negative pressure rectification method, the product purity is high, the solvent in the tower kettle can be recycled, no waste water is generated, and the method is very environment-friendly.)

1. A method for producing trimethyl orthoacetate by differential circulation continuity is characterized in that: the method comprises the following steps:

(1) absorption and cooling: feeding anhydrous acetonitrile, anhydrous methanol and a solvent into a reaction absorption tower to be absorbed and mixed with introduced dry hydrogen chloride gas at low temperature;

(2) salt forming reaction: introducing the mixed solution into a differential circulation tube type reaction device for salt forming reaction;

(3) and (3) neutralization reaction: introducing ammonia gas into a differential circulation tube type reaction device for neutralization reaction;

(4) alcoholysis reaction: carrying out alcoholysis reaction in a differential circulating tube type reaction device;

(5) membrane separation: cooling the alcoholysis solution to 0 ℃, and separating a by-product ammonium chloride by a membrane separation method;

(6) and (3) rectification: and (3) feeding the separated alcoholysis solution into a normal pressure rectifying tower to recover excessive methanol solution, feeding the bottom liquid of the normal pressure rectifying tower into a negative pressure rectifying tower to obtain trimethyl orthoacetate, and returning the bottom liquid of the negative pressure rectifying tower to the step (1) to be used as a solvent.

2. The method for producing trimethyl orthoacetate by differential loop continuous production according to claim 1, wherein: the solvent in the step 1 is dimethylethylene urea, DMI for short, the dosage of the dimethylethylene urea is 1-2 times of the total mass of the anhydrous acetonitrile and the anhydrous methanol, the dosage of the anhydrous methanol is equal to the molar quantity of the anhydrous acetonitrile, and the cooling absorption temperature is-5 ℃.

3. The method for producing trimethyl orthoacetate by differential loop continuous production according to claim 1, wherein: the reaction temperature in step 2 was 10 ℃.

4. The method for producing trimethyl orthoacetate by differential loop continuous production according to claim 1, wherein: and in the step 3, the pH value of the reaction system is adjusted to be 5-7.

5. The method for producing trimethyl orthoacetate by differential loop continuous production according to claim 1, wherein: the reaction temperature in step 4 was 40 ℃.

Technical Field

The invention relates to the field of fine chemical engineering, in particular to a method for producing trimethyl orthoacetate through differential circulation and continuity.

Background

Trimethyl orthoacetate is also known as 1,1, 1-trimethoxyethane. The liquid is colorless and transparent liquid with pleasant smell at normal pressure and temperature, is insoluble in water, and is soluble in organic solvents such as ethanol and diethyl ether. The molecular formula is C5H12O3, and the structural formula is CH3C (OCH3) 3. The main application is the organic intermediate for synthesizing medicines and pesticides.

At present, the commonly reported production process of trimethyl orthoacetate takes ethylene wax, absolute methanol and dry hydrogen chloride as raw materials, and performs salt forming reaction under the action of a solvent to generate ethylimine formamidine hydrochloride, and then methanol is added for alcoholysis reaction to prepare trimethyl orthoacetate. Wherein, the selection of the solvent has great influence on the reaction process, and the solvents with low boiling point, such as normal hexane, carbon tetrachloride and kerosene, which are commonly used in industry have large toxicity, easy volatilization and large dosage, are not beneficial to safe production and low-cost operation. Meanwhile, a centrifugal machine is adopted for filtering in the solid-liquid separation process of the byproduct ammonium chloride and trimethyl orthoacetate, the safety production is not facilitated, and the ammonium chloride carried in the filtered alcohol solution is washed by water due to low filtering precision, so that on one hand, waste water is generated, and on the other hand, the yield of methyl orthoacetate is reduced.

CN 102924244A (43), discloses a production process of high-quality trimethyl orthoacetate, which comprises the steps of preparing ethimine A hydrochloride by salifying ethyl wax, methanol and hydrogen chloride in the presence of pseudocumene as a solvent, then placing the ethimine A hydrochloride into a methanol solution, dropwise adding ammonia methanol solution to adjust the pH value, carrying out alcoholysis reaction to obtain a trimethyl orthoacetate crude product, filtering to remove solid ammonium chloride and recycling, adsorbing the filtrate by strong-basicity macroporous ion exchange resin to remove chloride ions, and finally obtaining the trimethyl orthoacetate product by continuous fine filling. The disadvantages of this method are: the strong-alkaline macroporous ion exchange resin generates an acid-base solution in the regeneration process, which causes the problem of wastewater treatment.

The invention has the following patent: a preparation method (CN201410047965.6) of a process for continuously preparing trimethyl orthoacetate by taking ionic liquid as a solvent comprises the steps of feeding anhydrous acetonitrile, anhydrous methanol and the solvent into a reaction kettle, cooling to-5 ℃ at a low temperature, introducing dry hydrogen chloride gas into the kettle, stirring for reaction for 6 hours, conveying the mixed solution into a second reaction kettle, adding precooled methanol at the temperature of 5 ℃, stirring for 0.5 hour, adjusting the pH of the reaction system to 5-6 by ammonia gas, and conducting alcoholysis on the mixed solution for 12 hours at the temperature of 40 ℃, wherein the solvent is hydrophobic ionic liquid; cooling the alcoholysis solution to 0 ℃, adjusting the pH value to 8.0 by using ammonia gas, then conveying the alcoholysis solution into a normal-pressure rectifying tower, and collecting fractions at 107-109 ℃ to obtain a trimethyl orthoacetate product; and (3) feeding the bottom kettle liquid of the rectifying tower into a washing kettle for washing, feeding the lower layer liquid into a drying kettle for drying, and recycling the dried solvent. The method has the disadvantages that the reaction process is a kettle type continuous reaction, the reaction time is long, the bottom liquid of the rectifying kettle is washed by adding water, the operation is complicated, and the problem of sewage treatment generated by washing water is solved.

The method for producing trimethyl orthoacetate by taking acetonitrile, methanol and hydrogen chloride as raw materials comprises the steps of intermittent production, continuous production and wastewater production, and causes pressure on the environment.

Disclosure of Invention

The invention aims to provide a method for producing trimethyl orthoacetate by differential circulation and continuous production, so as to solve the problems in the background technology.

In order to achieve the purpose, the invention provides the following technical scheme:

a method for producing trimethyl orthoacetate by differential circulation continuity comprises the following steps:

(1) absorption and cooling: feeding anhydrous acetonitrile, anhydrous methanol and a solvent into a reaction absorption tower to be absorbed and mixed with introduced dry hydrogen chloride gas at low temperature;

(2) salt forming reaction: introducing the mixed solution into a differential circulation tube type reaction device for salt forming reaction;

(3) and (3) neutralization reaction: introducing ammonia gas into a differential circulation tube type reaction device for neutralization reaction;

(4) alcoholysis reaction: carrying out alcoholysis reaction in a differential circulating tube type reaction device;

(5) membrane separation: cooling the alcoholysis solution to 0 ℃, and separating a by-product ammonium chloride by a membrane separation method;

(6) and (3) rectification: and (3) feeding the separated alcoholysis solution into a normal pressure rectifying tower to recover excessive methanol solution, feeding the bottom liquid of the normal pressure rectifying tower into a negative pressure rectifying tower to obtain trimethyl orthoacetate, and returning the bottom liquid of the negative pressure rectifying tower to the step (1) to be used as a solvent.

Preferably, the solvent in the step 1 is dimethylethylene urea, abbreviated as DMI, the dosage of which is 1-2 times of the total mass of the anhydrous acetonitrile and the anhydrous methanol, the dosage of the anhydrous methanol is equal to the molar quantity of the anhydrous acetonitrile, and the cooling absorption temperature is-5 ℃.

Preferably, the reaction temperature in the step 2 is 10 ℃.

Preferably, the pH of the reaction system is adjusted to 5 to 7 in the step 3.

Preferably, the reaction temperature in the step 4 is 40 ℃.

Compared with the prior art, the invention has the following advantages: DMI is used as a solvent, so that the yield of hydrochloride is improved, and the salt formation quality is good; solid-liquid separation is realized by utilizing a membrane separation technology, and the product yield is improved; the differential circulation tube type reaction device is adopted, so that continuous production can be realized, the reaction speed is increased, and the production efficiency is improved; the trimethyl orthoacetate is separated by adopting a negative pressure rectification method, the product purity is high, the solvent in the tower kettle can be recycled, no waste water is generated, and the method is very environment-friendly.

Drawings

FIG. 1 is a schematic flow chart of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.