SU745897A1 - Method of preparing thiourea - Google Patents

Description

This invention relates to an improved process for the preparation of thiourea used in the gold industry in the field of pharmaceutical preparations. A known method for producing thiourea by reacting cyanamide calcium ki with an aqueous solution of ammonium sulfide or another sulfur-containing raw material at 25-80 ° C by reaction; HjCNa + NajS + 2H (NHj) + 2NaOH When producing thiourea in a known way, increasing the alkalinity of the medium to a certain limit speeds up the process, after which it slows down, products of adverse reactions are formed and the quality of the product deteriorates 1. The closest to the proposed method to the technical essence and the achieved result is a method of obtaining thiourea by the interaction of calcium cyanamide with an aqueous solution of ammonium sulfide by the reaction: CaCN, (NH) j, S --- CS (NHj,), j + Ca (H5) a - HbS, followed by filtration of the suspension by precipitation of calcium ion with carbon dioxide and separation of the thiourea from its aqueous solution by evaporation, crystallization and formation of crystals 2. However, this method does not allow to obtain a product with a basic substance content above 91-92%. The formation of products of side reactions leads to difficulties in the operation of the equipment, reduces the intensity of the process, reduces the yield of the product, which, under the conditions of existing production, does not exceed 72-75%. In order to ensure the maximum rate of formation of the product according to known methods and to improve its quality, it is necessary to maintain during the synthesis either the optimum ratio of ammonia and cyanamide, or the optimum alkalinity. Excess aNDHHac in known methods can be removed either by partially binding it, for example, in the form of sulfate or ammonium chloride, or by purging the reaction medium with a gaseous carrier (for example, inert gas, natural gas combustion products). The first method is expensive and difficult to implement in practice due to the associated formation of calcium salts.

The second method is preferable, since it is simpler and cheaper. However, the volatility of hydrogen sulfide from a solution of ammonium sulfide in the temperature range at which Thiourea is synthesized is very high, especially at 50-80 ° C,

Thus, when ammonia is purged due to high volatility, hydrogen sulfide, which is necessary for the reaction, can be removed.

In addition, the use of, for example, air as a gas source: an energy source can lead to the formation of oxygen oxidation products of cyanide and i, thiourea, which will also decrease the yield of the READY product and. Change as inert gas carrier is expensive.

Thus, according to known data, it is impossible to blow amyiak fiCslayJcoM.

 The aim of the invention is to intensify the process and increase the yield of the finished product.

This goal is achieved by the method of producing thiourea by the interaction of calcium cyanamide with a solution of ammonium sulphide at.

temperature of 25-80 ° C to obtain:.

ammonia and suspension, followed by filtration of the suspension, precipitation., .., ..:., calcium ion with carbon dioxide in case of blowing off state ammonia with a mixture of air, air and water vapor at a volume ratio (10: 1) - (1 : 3) conformance; enno and while maintaining the ratio of ammonia and slr within (2: 1) -. (3: 1), and at the end of the process 6: 1. . ,,., „,,.

A distinctive feature of the method of the 1st; yy1§e of the introduction of the system. L tdukbybyd; Yelu yu of his Ammonia mix; with air and water; about steam with a volume Gbm ratio (10: 1) - (1: 3) and supplying the ratio of ammonia and raw materials within (2: 1) (3: 1 ), and at the end of the process 6: 1.

Example: In a cascade of 3 reactors equipped with frame-type agitators, the mixture of reagents is continuously loaded in the following quantities, kg / l-h per unit volume of the reactor per unit time of calcium cyanamide, technical 0.1; ammonium sulfide solution with a concentration of 140 g / l (0.43); wash water with a concentration of thiourea 70 g / l 0.17.

Temperature, ° C in reactors (as the reactants move). Supported within the following limits: I reactor 25-50

II reactor 60-65

IIIreactor, 70-80

In each FieaKTope for stripping the ammonia, the mixture of reagents is continuously Q is blown with pre-humidified air, the specific flow rate, h, which is equal to:

I R.E./O.

il rector2.0

III reactor; 5.0

After separation of the sludge, a synthetic solution of thiourea is treated in a continuous carbon mill to remove calcium ion. Carbon dioxide consumption 10-12 kg / m solution.

Thiourea is separated from the solution by evaporation, crystallization, and folding. Get the product in the amount of 0.0475-0.490 kg / l: h with the content of pcHOjBHoro substances 96-98%.

The effect of the composition of a moistened airflow and the product yield; and the intensity of the process at a specific flow rate of dry air of 80 l / kg of raw material is shown in the table.

Example 2. In a batch reactor at room temperature: the temperature is charged with a solution (Ø - 140 g / l concentration and technical calcium cyanamide in a weight ratio b: and the temperature gradually increases to ammonia, part which sa randomly differentiates into the atmosphere. The product yield is 93%,

)

Below are the results obtained (in terms of 1 mol of the feedstock):

Claims (1)

Claim The method of obtaining thiourea pu. the interaction of calcium cyanamide with a solution of ammonium sulfide at Branch ^ SPT ’’ Patent ’’ Uzhhorod, st. Project, 4