GB737463A - Improvements in or relating to the preparation of potassium salts of alkyl sulphuricacids - Google Patents

Abstract

A potassium salt of an alkyl sulphuric acid is prepared by introducing into one end of a countercurrent system a sodium salt of the acid dissolved in a first solvent, and introducing into the other end of the countercurrent system an inorganic potassium compound dissolved in a second solvent, the two solvents being substantially immiscible with each other under the conditions of operation and such that, under the conditions of operation, the first solvent retains the sodium and potassium salts of the alkyl sulphuric acid largely to the exclusion of the inorganic compounds, and the second solvent retains the inorganic compounds largely to the exclusion of the sodium and potassium salts of the alkyl sulphuric acid. Preferably the first solvent is an oxygenated organic solvent such as isopropyl alcohol, secondary butyl alcohol or methyl ethyl ketone and the second solvent is water. The ratio of the two solvents may be between 1 : 3 and 3 : 1. Potassium carbonate is the preferred potassium compound but the hydroxide and salts such as the fluoride or nitrate may be used. The reaction may be carried out at room temperature or higher. In examples (1) a mixture of sodium C10-C18 secondary alkyl sulphates dissolved in isopropyl alcohol is fed to the first stage of a four-stage countercurrent contacting apparatus at 50 DEG C. while aqueous potassium carbonate is fed to the fourth stage. The product dissolved in isopropyl alcohol is withdrawn from the fourth stage; (2) a similar mixture of secondary alkyl sulphates dissolved in isopropyl alcohol is treated in a seven-stage apparatus with aqueous potassium hydroxide. Instead of multi-stage apparatus, a packed tower may be used or countercurrent equipment having rotating elements. Specification 537,255 is referred to. The Provisional Specification describes also a batch process in which a sodium salt of an alkyl sulphuric acid is reacted with an inorganic potassium salt in the presence of a solvent in which the sodium salt of the inorganic acid is substantially insoluble as compared with the other components of the reaction mixture. The solvent may be water. In example 3, a mixture of C10-C18 secondary alkyl sulphates is mixed with an aqueous solution of potassium carbonate. After standing, the mixture separates into a lower inorganic layer and an upper organic layer containing the required potassium alkyl sulphate.