or sulfonate moiety are useful as froth promoters to improve the recovery of clean coal in the froth flotation of finely divided coal disulfonated diphenyl ether compounds bearing at least one nuclear alkyl group of from 10 to 22 carbon atoms are particularly efficacious application_number US 16124480 A description the aryl sulfonate used as a froth promoter in the practice of this invention is a sulfonated diphenyl ether or biphenyl compound optionally bearing nuclear alkyl substituents the sulfonated diphenyl ether is preferred preferably this aryl sulfonate compound bears at least one nuclear alkyl radical having from 8 to about 20 more preferably 10 to about 18 more preferably 12 carbon atoms the alkyl radical can be branched or linear a mixture of these aryl sulfonate compounds is also operable the identity of the moiety corresponding to m 1 or m 2 in the formula of the aryl sulfonate compound can greatly affect the activity of the promoter the activity of the aryl sulfonates containing an ammonium moiety bearing one or two alkyl groups is especially unpredictable preferably m 1 and m 2 are each a sodium or potassium cation the aryl sulfonate compounds described herein can be prepared in general by methods known to the art u s pat no 2 854 477 discloses a method of preparing alkyl diphenyl ether sulfonates in one preferred method a diphenyl ether or biphenyl compound is alkylated by reacting it with an olefin in the presence of a friedel crafts catalyst the alkylated aryl compound is then sulfonated by contacting it with sulfur trioxide in refluxing sulfur dioxide this process produces a high degree of sulfonation i e both of the phenyl moieties in the compound are sulfonated which is preferred the coal to be.