GB1043043A - Process for making substituted diphenyl ether sulfonates - Google Patents

Abstract

Diphenyl ether sulphonates of the general formula <FORM:1043043/C2/1> where R is a C8-C18 alkyl group, b is 0 or 1, and c is 1 or 2 are prepared by contacting a substituted diphenyl ether with at least the theoretical amount of chlorosulphonic acid or sulphur trioxide as a sulphonating agent at a temperature of 0-50 DEG C. characterized in that the diphenyl ether is dissolved in a liquid saturated aliphatic hydrocarbon solvent prior to the sulphonation. The sulphonation is preferably carried out by passing into the hydrocarbon-ether solution a gaseous mixture of sulphur trioxide and an inert gas. When sufficient sulphur trioxide has been introduced and has reacted, the sulphonated product, being insoluble in the hydrocarbon solvent, forms a separate lower layer in the reaction mixture. The supernatant hydrocarbon layer may be decanted or drawn off for reuse in the process. The lower sulphonate layer may then be reacted with a base in water sufficient to make an aqueous salt solution. Liquid chlorosulphonic acid may also be used as the sulphonating agent. Saturated aliphatic hydrocarbons suitable for use as solvents include those containing from four to twenty carbon atoms in the molecule and especially hexane particularly a hexane - rich mixture commercially available from petroleum refining processes. The preferred ratio of reactants is from about the theoretical equivalent amount to about 30% in excess of that amount of the sulphonating agent in relation to the substituted diphenyl ether. When sulphur trioxide is used for the sulphonation, an inert gas, e.g. nitrogen may be used as a carrier and diluent. The process may be carried out in a batchwise or continuous manner. A continuous reaction may be carried out in a column in which the gaseous sulphonating mixture is passed upward, countercurrent to the downward flow of a hydrocarbon-ether solution. Examples are given for the preparation of dodecyl diphenyl ether disulphonic acid and dodecyl chlorodiphenyl ether sulphonic acid using hexane and octane as the hydrocarbon solvent.