CS206972B1 - Method of removing the so2 and hc1 from the reaction compound following the chloridation of carboxyl acids or alcohols - Google Patents

Description

(54) Process for removing SO ₂ and HCl from a reaction mixture after chlorination of carboxylic acids or alcohols The invention relates to a process for removing SO _{2 and} HCl from a reaction mixture after chlorination of carboxylic acids or alcohols.

^s Hydrochloric acid and sulfur dioxide are obtained as a by-product and can be processed further.

In the reaction of thionyl chloride with carboxylic acids or alcohols, a mixture of sulfur dioxide and hydrogen chloride develops as a so-called off-gas. This offgas can be disposed of in many ways. In the case of small quantities, the evolving sulfur dioxide and hydrogen chloride are discharged into the atmosphere, in larger amounts the sulfur dioxide and hydrogen chloride are absorbed into the sodium hydroxide solution and the resulting sodium sulfite and sodium chloride solution is formed ^. either discharged into waste water or a salt solution; is converted by the action of calcium hydroxide to i

Even practically insoluble calcium sulfite and soluble calcium chloride. Calcium sulphite is filtered and exported as waste to landfill. Dissolved calcium chloride together with other formed salts is discharged into waste water. Absorption to calcium hydroxide is also used to capture the mixture of sulfur dioxide and hydrogen chloride, and the resulting calcium sulfite is filtered and weighed to landfill and soluble calcium chloride is discharged into waste water. All these waste gas disposal methods have an adverse effect on the environment, ie they contaminate the air, increase the salinity of watercourses, contaminate groundwater and have high demands on material handling.

The above-mentioned disadvantages reduce the process of removing SO ₂ and HCl from the reaction mixture after the chlorination of carboxylic acids or alcohols with thionyl chloride or from the organic solvent according to the invention, which is based on the fact that the SO ₂ and HCl mixture leaving to boiling water in an absorption system where hydrogen chloride is trapped to form hydrochloric acid containing 2 to 20, 24% by weight of hydrogen chloride and pure sulfur dioxide is separated, for example, by absorption in sodium hydroxide solution, or the balance of SO ₂ and HCl in an organic solvent the organic solvent is removed to form a SO ₂ and HCl degassing which is treated as described above.

An advantage of the process of disposing of the mixture of gaseous sulfur dioxide and hydrogen chloride according to the invention is that technical hydrochloric acid and pure sulfur dioxide can be obtained which can be processed into or liquefied for sodium sulphite and used or otherwise treated. This removes useless waste that needs to be disposed of;

air, watercourses and groundwater. Raw materials are obtained which can be used in other chemical industry productions. ¹

The process for disposing of the sulfur dioxide / hydrogen chloride mixture according to the invention is illustrated by way of example in the following examples:

Example 1

A mixture of 81.7 g of sulfur dioxide and 45.4 g of hydrogen chloride is fed over 120 minutes into an absorption column with a rectification column connected to which 183.4 g of water is kept, which is kept at a constant boiling point during the process. The separating sulfur dioxide is passed to another absorption column with 262.3 g of sodium hydroxide solution (51 g of solid sodium hydroxide in 211.3 g of water). The resulting sodium bisulfite was neutralized in a further phase with 262.3 g of sodium hydroxide solution. After cooling the solution, sodium sulfite precipitates. A total of 228.8 g of hydrochloric acid containing 19.84% of hydrogen chloride and 224 g of crystalline sodium sulfite are obtained.

Example 2

A solution of 6.9 g of sulfur dioxide and 12.2 g of hydrogen chloride in 1890.9 g of o-dichlorobenzene is boiled in a flask equipped with a packed rectification column. Within 60 minutes, 6.7 g of sulfur dioxide and 11.0 g were passed through the top of the column

Claims (2)

SUBJECT Process for removing SO ₂ and HCl from a reaction mixture after the chlorination of carboxylic acids or alcohols with thionyl chloride or an organic solvent, characterized in that the mixture of SO ₂ and HCl leaving in the form of off-gas is led to boiling. water in the absorption system, which retains hydrogen chloride to form hydrochloric acid, containing 2 to 20.24% by weight of hydrogen chloride and pure sulfur dioxide is separated, for example, by absorption in sodium hydroxide solution, or the balance of SO ₂ and HCl in organic hydrogen chloride are processed according to the method of Example 1. Example 3 150.3 g of o-dichlorobenzene containing 1.91 g of hydrogen chloride and 1.65 g of sulfur dioxide and 131.9 g of soil are introduced into the flask. Distillation is carried out by stirring the mixture. The O-dichlorobenzene separating in the arethropic adapter is then back into the flask ^! and water is collected separately. At the end of the distillation, o-dichlorobenzene contains less than 0.01% hpi of sulfur dioxide and less than 0.01% -chlorine; thanks. Distilled water contains all sulfur dioxide and hydrogen chloride, which is shortened according to the examples of flax hydrochloric acid and sulfur dioxide *, as _follows : To. 128.6 g of o-dichlorobenzene containing 1.63 g of hydrogen chloride and 1.42 g of sulfur dioxide are introduced into the flasks. Water is injected into the feed, carrying o-dichlorobenzene and sulfur dioxide. O-Dichlorobenzene returns after separation of the water. In this way, virtually all of the sulfur dioxide (content in the aqueous and dichlorobenzene layers in the flask is less than 0.01 wt%) is blown off, almost all of the hydrogen chloride is transferred to the aqueous layer in the flask which is separated from the o-dichlorobenzene in the separator. . ₍ BACKGROUND OF THE INVENTION The organic solvent is removed from the organic solvent to form SO ₂ and HCl degasses which are treated as described above. 2. Method according to item 1, wherein the removal of SO ₂ and a mixture of HC1 from organic matter rozpoula decoction. The method according to item 1, wherein the removal of SO ₂ and HC1 going from an organic solvent) by adding water or steam, and bringing the mixture to boil.