Method for recycling tail gas during thionyl chloride preparation

Abstract

The invention relates to a method for recycling tail gas during thionyl chloride preparation, which belongs to the field of chemical engineering process. The method is that delivering the gas released during the transportation process of thionyl chloride crude product from a crude product vulcanizing tank to a crude product intermediate tank and the gas remained after the rectification and the condensation of the thionyl chloride to a thionyl chloride synthesis kettle for cyclic utilization by using a gas compression conveying machinery. The sulfur dioxide method thionyl chloride manufacturing technology forms a perfect gas phase closed cycle, which enables the yield of thionyl chloride to be above 99 percent, and saves a great amount of tail gas absorption alkali and eliminates environment pollution. The liquid ring type compressor has the advantages that the operation is simple and convenient, the construction cost is low, the maintenance quantity is small and no additional agent is used in the system.

Description

technical field [0001] The invention relates to a method for recovering and utilizing tail gas in the preparation of thionyl chloride, which belongs to the field of chemical technology. Background technique [0002] Thionyl chloride is an important chlorination agent for organic synthesis, such as the chlorination of alcoholic hydroxyl groups, chlorination of carboxylic acids, chlorination of acid anhydrides, chlorine replacement of organic sulfonic acids or nitro compounds. Manufacture of acid chlorides can also be used in ring closure reactions and Beckmann transpositions. (Extracted from the second edition of "Inorganic Salt Industry Handbook", edited by Tianjin Research Institute of Chemical Industry P601) [0003] Commonly used synthetic methods suitable for industrialized production of thionyl chloride have three kinds: [0004] (1) Sulfur trioxide method: Phosphorus pentachloride reacts with sulfur trioxide to generate thionyl chloride and phosphorus oxychloride. Th...

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Problems solved by technology

[0004] (1) Sulfur trioxide method: Phosphorus pentachloride reacts with sulfur trioxide to generate thionyl chloride and phosphorus oxychloride. The process of this route is simple, but the separation of thionyl chloride and phosphorus oxychloride is difficult, and the product is not easy purify

[0005] (2) Chlorosulfonic acid method: use antimony chloride as a catalyst to react sulfur monochloride with chlorine gas and chlorosulfonic acid. This method has complicated process, backward technology, large material consumption and serious pollution

There are two ways to remove the gas dissolved in the liquid, the heating method and the decompression method, and this degassing method, which depends on increasing the temperature of the material so that the gas is released and returned to the thionyl chloride synthesis kettle, will cause some product loss. Under higher pressure, there are more non-condensable gases such as sulfur dioxide dissolved in it, resulting in an increase in the amount of tail gas in the latter production process

For the rectification tail gas, the patent simply mentions that the diaphragm pump is used to return the thionyl chloride synthesis tank for recycling. This process may cause the pressure of the thionyl chloride synthesis tank to gradually increase and the proportion of reaction materials to be unbalanced

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