SU808498A1 - Method of preparing tetramethylthiuramdisulfide - Google Patents

Description

(54) METHOD OF OBTAINING TETRAMETHYLTIURUM DISULFIDE

The invention relates to organic synthesis, in particular, to an improved method for producing tetramethylthiuram disulfide, and can be used in chemical industry. A known method of producing tetramethylthiuram disulfide by bubbling a mixture of nitrogen oxides {NO2NO2) with air through an aqueous solution of sodium dimethyldithiocarbamate 1. Despite the high yield of tetramethylthiuran disulfide (90-95%), the duration of the process (approx. use it in large-scale production. In addition, a method is known for the rapid oxidation of sodium dimethyldithiocarbamate (O time, 2-5 min), which includes continuous feeds-in. sodium dimethyldithiocarbamate solution mixed with sodium nitrite and an aqueous solution of sulfuric acids necessary to maintain a pH in the range of 1.5 to 2. The waste nitrogen oxides are mixed with air and fed back to the reaction zone 2. The main disadvantage of this method is the use of expensive sodium nitrite reagent in the amount of 105% of the theoretically necessary, as well as a large amount of wastewater. The closest to the technical essence and the achieved result to the proposed method is to obtain tetramethylthiuramdis This includes the continuous supply of sodium dimethyldithiocarbamate and the aqueous solution of mineral acid to the reaction zone in an amount necessary to maintain the pH in the range of 1.5-2. At the same time, continuous bubbling of nitrogen oxides in a mixture with air is carried out through the reaction zone. Nitrogen oxides are removed from the reaction zone, mixed with oxygen-containing gas and fed back into the reaction zone. With a process time of 0.4-5 minutes, the yield of tetramethylthiuram disulfide is 49-76% pj. The disadvantage of this method is the low yield of the product and the large amount of waste; water (7001530 t / year). The purpose of the invention is to increase the yield of the target product. The goal is achieved by the fact that in the process of producing tetramethylthiuranyl disulfide by reacting sodium dimethyldithiocarbamate with an aqueous solution of mineral acid at pH 1.5-2 in the presence of nitrogen oxides, the solution of mineral acid is preliminarily treated with a mixture of nitrogen oxides with oxygen-containing gas for 30-60 s, then sodium dimethyldithiocarbamate is fed into the reaction solution for 15-40 seconds. The amount of sulfuric acid is determined by maintaining the pH of the reaction medium in the range of 1.5-2. As nitrogen oxides, N0 and N0 are used, which, in a mixture with air, form other oxides, for example, NjO. All nitrogen oxides in the mixture are in dynamic equilibrium and their proportion does not affect the product yield. This makes it possible to vary the supply of oxygen-containing gas, for example air, over a wide range. Reducing the time of pretreatment with nitrogen oxides of a solution of sulfuric acid (less than 30 s) and the dosing time of a solution of sodium dimethyldithiocarbamate (less than 15 s) and an increase in the dosage time of sodium dimethyldithiocarbamate (above 40 s) leads to a sharp decrease in product yield. An increase in the time of pretreatment with nitrogen oxides in a mixture with air of a solution of sulfuric acid for more than 60 s does not affect the product yield. Example 1. 50 ml of 10% sulfuric acid are charged to a reactor equipped with a turbine agitator for vigorous stirring to maintain the pH of the medium in the range of 1.5 2. Then bubbling is carried out

Time sparging nitrous gases, with

Dosing time of sodium dimethyldithiocarbamate, with

Air consumption, l / min. Nitrous gas consumption, l / min. Product yield,% Melting point, s

30,115

thirty

thirty

60

50 2020 30 1.0 1.5 1.0 2.0 1.5 2.0 1.0 1.5

79.5 7595 96

145 144146145 oxides of nitrogen mixed with air at a rate of 1 l / min through a solution of mineral acid. After 30 seconds sparging is stopped and 80 ml of sodium dimethyldithiocarbamate solution are dosed out within 26 seconds. The nitrogen oxides exiting the apparatus are mixed with air and re-fed into the reaction zone by bubbling. After dosing with sodium dimethyldithiocarbamate, the suspension of the tetramethylthiuram disulfide formed is continued to stir for 1 minute to remove nitrogen oxides. Then the suspension of tetramethylthiuram disulfide is washed, filtered, and after drying, the yield of the product is determined. The yield is 12.7 g or 95%. Melting point 146 ° C. Example 2. A reactor equipped with a turbine mixer for vigorous stirring was charged with 50 ml of 10% sulfuric acid to maintain the pH of the medium in the range of 1.5-2. Then, nitrogen oxides are bubbled in a mixture with air at a rate of 1.5 l / min through a mineral acid solution. After 60 seconds sparging is stopped and 80 ml of sodium dimethyldithiocarbamate solution are dispensed in 80 ml for 30 seconds. The oxides of nitrogen leaving the apparatus are mixed with air and again fed into the reaction zone by bubbling. After dosing with sodium dimethyldithiocarbamate, the suspension of the tetramethylthiuram disulfide formed is continued to stir for 1 minute to reduce the oxides of nitrogen. Then the tetramethylthiuram disulfide suspension is rolled, filtered, and after drying, the yield of the product is determined. The yield is 12.8 g or 96%. Melting point 145 ° C. The table shows the results of experiments on the implementation of the method for producing tetramethylthiuram disulfide.

A reduction in the pretreatment time of the mineral acid solution with nitrogen oxides in a mixture with air up to 12 s, as well as an increase or decrease in the dosing time of the sodium dimethyldithiocarbamate solution relative to optimal values (1540 s) results in a decrease in the yield of the product to 75%.

At the same time, carrying out the process of synthesizing tetramethylthiurancisulfide c. By the interaction of sodium dimethyldithiocarbamate and sulfuric acid solution, when the acid solution is pretreated with nitrogen oxides mixed with air for 30-60 s, and then dispensing the sodium dimethyldithiocarbamate solution for 15-40 s, allows to obtain a product with a high yield (more than 95%) and good quality, as evidenced by a high melting point of 143-1460 ° C.

In addition, the amount of wastewater is reduced to 120-150 tons / year due to a more complete conversion of the reactants, as well as due to the reduction of wash water at the washing stage.

tetramethylthiuram disulfide from by-products.

Claims (3)

1. The patent of Germany 1164391, cl. 12 about 17/02, publ. 1964. 2. The US patent 3255251, CL 260-567, published. 1966. 3. US patent number 3255250, five cl. 260-567, publ. 1966 (prototype).