CN110818605A

CN110818605A - Synthetic method of thiourea

Info

Publication number: CN110818605A
Application number: CN201911189446.2A
Authority: CN
Inventors: 高鹏; 安敬瑞; 张宁; 崔卫华
Original assignee: Shandong Efirm Biochemistry and Environmental Protection Co Ltd
Current assignee: Shandong Efirm Biochemistry and Environmental Protection Co Ltd
Priority date: 2019-11-27
Filing date: 2019-11-27
Publication date: 2020-02-21

Abstract

The invention belongs to the technical field of organic synthesis, and particularly relates to a synthetic method of thiourea. Carbon disulfide and ammonium carbonate are used as raw materials, thiourea is synthesized as a target product under the action of a catalyst, a certain amount of ammonia gas is introduced in the reaction process, and the catalyst is one of sodium carbonate, a molecular sieve and sodium hydrosulfide. The method has the advantages of simple operation steps, low energy consumption, short production period, high product yield and purity, and capability of meeting the quality requirements of the market on the thiourea; the raw materials are easy to obtain and the price is lower; the reaction has no solid waste, has high environmental protection value and is suitable for industrial production.

Description

Synthetic method of thiourea

Technical Field

The invention belongs to the technical field of organic synthesis, and particularly relates to a synthetic method of thiourea.

Background

Thiourea is an important chemical raw material and an organic chemical intermediate, can be used for producing medicines such as sulfimidazole, methyl thiouracil, methionine and the like, is a raw material of ascarid and contraceptive, and is used for synthesizing antithyroidism anti-entry medicines, antitubercular medicines, intravenous injection anesthetic medicines and the like;

the thiourea has wide application prospect in petrochemical industry and pharmaceutical chemical industry, and a plurality of medical molecules also have structural fragments of the thiourea. For example, many oral hypoglycemic drugs and antithyroid drugs in the current market belong to thiourea molecules. In agriculture, thiourea can also be used as a bactericide, a rust remover, a potato germination promoter, a livestock fattening agent, a nitrification-inhibiting fertilizer, and the like. The addition of trace thiourea can inhibit the nitrification of soil and increase the adsorbability of soil.

The lime nitrogen method is a main process for producing thiourea, and the reaction principle is as follows: (1) absorbing hydrogen sulfide by lime nitrogen water solution, and (2) reacting calcium hydrosulfide with calcium cyanamide to generate thiourea. The specific process comprises the following steps: mixing lime nitrogen and water (reflux mother liquor or washing liquor) uniformly in a synthesis reaction kettle, and introducing hydrogen sulfide gas while stirring for reaction to generate thiourea solution. Filtering the solution, putting the solution into a cooling crystallizer for freezing crystallization, centrifugally separating a crystallization liquid, and drying crystals to obtain a finished product. The process is continuously perfected and matured in production practice, has good production stability and low operation technical requirement, is suitable for a extensive production mode, but produces a large amount of solid waste residues, and produces 2.7 tons of waste residues every ton of thiourea, thereby causing huge environmental protection pressure.

With the increasing development of the industrial, agricultural and pharmaceutical industries, the demand of thiourea and derivatives thereof is increasing, and the old process for producing thiourea has the problems of large energy consumption, serious solid waste residue pollution and the like. Therefore, a new process with low cost and environmental protection is urgently needed to be developed.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a method for synthesizing thiourea, which synthesizes the target product thiourea by taking carbon disulfide and ammonium carbonate as raw materials under the action of a catalyst, and solves the problems of high production cost, high energy consumption, high pollution and the like in the prior art.

A method for synthesizing thiourea uses carbon disulfide and ammonium carbonate as raw materials, synthesizes the target product thiourea under the action of a catalyst, and introduces a certain amount of ammonia gas in the reaction process, and the reaction equation is as follows:

the catalyst is one of molecular sieve, sodium carbonate and sodium hydrosulfide;

preferably, the mass of the catalyst is 0.05-5% of that of the solvent;

preferably, the molar ratio of ammonium carbonate to carbon disulfide is 1: 1.1-1.5;

the solvent used in the reaction is water, and the mass of the solvent is 4-8 times of that of ammonium carbonate.

In the reaction route adopted by the invention, the reaction raw material ammonium carbonate is solid, and the solid-liquid reaction effect is better than the gas-liquid reaction. The amount of the solvent water is 4-8 times of the mass of the ammonium carbonate, so that the reaction can be better carried out, the separation of a final product is facilitated, if the amount is too large, the separation difficulty of the final product is increased, and the reaction is influenced if the amount is not enough.

The specific synthesis steps are as follows:

adding carbon disulfide, ammonium carbonate and a catalyst into a reactor filled with solvent water; introducing ammonia gas as system pressure, heating to reaction temperature, and reacting for a period of time; and after the reaction is finished, cooling, separating excessive carbon disulfide, and crystallizing to obtain the target product thiourea.

Preferably, ammonia gas is introduced until the system pressure is kept between 0 and 1.5 MPa;

by introducing ammonia gas under such a pressure, decomposition of ammonium carbonate and evaporation of carbon disulfide can be suppressed. The loss of raw materials is large due to low pressure, the yield is reduced, and the cost is increased; too high a pressure increases the risk of reaction.

Preferably, the reaction temperature is 40-80 ℃.

At the reaction temperature, the yield is high, and the reaction rate is high. The excessive high temperature can cause the generation of more impurities along with other reactions in the reaction process, thereby influencing the yield and the purity; if the temperature is too low, the reaction rate is slow and the reaction may not proceed sufficiently.

Preferably, the reaction time is 0.5-2.5 h.

If the time is too short, the reaction is insufficient, the quality of the product cannot be guaranteed, and if the time is too long, the production period is too long, and the production cost is increased.

The invention has the following beneficial effects:

(1) the method has the advantages of simple operation steps, low energy consumption, short production period, high product yield and purity which are far higher than the quality requirements of the market on thiourea;

(2) the raw materials are easy to obtain and have lower price, and the excessive carbon disulfide can be recycled;

(3) no waste is generated in the reaction, and the method has high environmental protection value.

At present, ammonia can be directly used as a reaction raw material to participate in the reaction, a small amount of ammonia is introduced into the reaction to play a role similar to that of shielding gas, only a small amount of ammonia is required to be introduced, and ammonium carbonate is used as a reactant, so that the production cost is better than that of the ammonia directly used as the raw material. And after the reaction is finished, the excessive carbon disulfide and water are mechanically used for the next batch. In conclusion, the invention provides a novel thiourea synthesis method, which greatly reduces the production cost, improves the yield and the quality of the product, has low energy consumption, no by-product, environmental protection and energy conservation, is suitable for industrial production and is convenient for downstream use. The reaction product is free from other solid wastes which are difficult to treat, the operation steps are simple, the raw materials are easy to obtain and low in price, and the method has high environmental protection value.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all 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.

Example 1

The method comprises the following steps of (1) synthesizing a target product thiourea by using carbon disulfide and ammonium carbonate as raw materials, wherein a reaction equation is as follows:

the concrete steps are as follows

(1) Adding 72.12g of ammonium carbonate, 75.28g of carbon disulfide, 500.17g of water and 25g of molecular sieve into a reactor;

(2) introducing ammonia gas to ensure that the system pressure is 1.5MPa, heating to 80 ℃, and keeping the temperature for reaction for 60 minutes;

(3) and after the reaction is finished, cooling, separating carbon disulfide, and crystallizing to obtain an aqueous solution of thiourea solid and thiourea, wherein the yield is 91.17% in terms of thiourea, and the content of the solid thiourea is 99.43%.

Example 2

the concrete steps are as follows

(1) 120.01g of ammonium carbonate, 105.33g of carbon disulfide, 500.17g of water and 2g of sodium carbonate are added into a reactor;

(2) introducing ammonia gas to ensure that the system pressure is 0.5MPa, heating to 40 ℃, and keeping the temperature for reaction for 150 minutes;

(3) and after the reaction is finished, cooling, separating carbon disulfide, and crystallizing to obtain an aqueous solution of thiourea solid and thiourea, wherein the yield is 90.21% in terms of thiourea, and the content of the solid thiourea is 99.39%.

Example 3

the concrete steps are as follows

(1) 105.12g of ammonium carbonate, 105.41g of carbon disulfide, 500.57g of water and 5g of sodium hydrosulfide are added into a reactor;

(2) introducing ammonia gas to ensure that the system pressure is 1.3MPa, heating to 60 ℃, and carrying out heat preservation reaction for 120 minutes;

(3) and after the reaction is finished, cooling, separating carbon disulfide, and crystallizing to obtain an aqueous solution of thiourea solid and thiourea, wherein the yield is 90.87% in terms of thiourea and the solid thiourea content is 99.26%.

Comparative example

According to the prior art, 28.09g of lime nitrogen and 500.04g of water are added into a reaction container, a hydrogen sulfide gas is introduced under a micro-negative pressure for absorption, the calcium value of the hydrogen sulfide gas is detected after the hydrogen sulfide gas is introduced for 2 hours, 50.37g of secondary lime nitrogen is added when the calcium value is detected to be 85g/L (the calcium value reaches 80-100g/L, the secondary lime nitrogen can be added), the temperature is increased to 85 ℃, the reaction is kept for 2.5 hours to obtain a thiourea aqueous solution, 70.2g of solid waste filter residue is generated after filtration, thiourea solid is obtained after the filtrate is cooled and crystallized, the yield is 88.85% of thiourea, and the content of the thiourea solid is 99.

In the comparison example, the feeding is carried out twice, the calcium value needs to be detected between the two times of feeding, the time is consumed for detecting the calcium value, and the product yield and quality are influenced if the calcium value is not in the index range.

Claims

1. A method for synthesizing thiourea is characterized in that carbon disulfide and ammonium carbonate are used as raw materials, thiourea is synthesized under the action of a catalyst, ammonia gas is introduced in the reaction process, and the reaction equation is as follows:

2. a method for synthesizing thiourea according to claim 1, wherein the solvent used in the reaction is water, and the mass of the solvent is 4-8 times of the mass of ammonium carbonate.

3. The method for synthesizing thiourea according to claim 1, wherein the catalyst is one of molecular sieve, sodium carbonate and sodium hydrosulfide.

4. The method for synthesizing thiourea according to claim 1, wherein the molar ratio of ammonium carbonate to carbon disulfide is 1: 1.1-1.5.

5. The method for synthesizing thiourea according to claim 1, wherein the mass of the catalyst is 0.05-5% of the mass of the solvent.

6. The method for synthesizing thiourea according to claim 1 or 2, comprising the following steps: adding carbon disulfide, ammonium carbonate and a catalyst into a reactor filled with solvent water; and (3) introducing ammonia gas, heating to raise the temperature, carrying out reaction, cooling after the reaction is finished, separating excessive carbon disulfide, and crystallizing to obtain the target product thiourea.

7. The method for synthesizing thiourea according to claim 6, wherein ammonia gas is introduced until the system pressure is maintained at 0-1.5 MPa.

8. The method for synthesizing thiourea according to claim 6, wherein the reaction temperature is 40-80 ℃.

9. The method for synthesizing thiourea according to claim 6, wherein the reaction time is 0.5-2.5 h.