GB672736A - Improvements in and relating to the production of petroleum sulphonates - Google Patents

Abstract

Oil-soluble petroleum sulphonates are produced by treating a petroleum hydrocarbon oil or fraction thereof with a sulphonating agent under sulphonating conditions, recovering an oil phase containing oil-soluble sulphonic acids from the sulphonation mixture, extracting the oil-soluble sulphonic acids from the oil phase with a mixture of water and a lower aliphatic alcohol containing from about 50 to 80 per cent by volume of alcohol, alternately mixing the aqueous-alcohol extract with a low boiling-point, water-immiscible organic solvent for oil-soluble petroleum sulphonates and with at least a slight excess of an alkaline compound thereby forming an aqueous-alcohol phase containing inorganic salts and a water-immiscible solvent phase containing oil-soluble petroleum sulphonates, separating the two phases, and recovering the oil-soluble sulphonates from the water-immiscible solvent phase so separated. The petroleum hydrocarbon oil may be sulphonated with a sulphonating agent such as sulphuric acid, chlorsulphonic acid or sulphur trioxide in the presence of a suitable catalyst. Preferably concentrated or fuming sulphuric acid is used, the oil phase is separated and extracted with an aqueous solution of methanol containing from 50 to 80 per cent by volume of methanol. An acidic aqueous alcohol sludge is separated from the resultant mixture and it is mixed with an alkaline compound, such as an alkali or alkalic earth metal hydroxide, carbonate, borate, phosphate, acetate or the like to a resultant pH of 9.7 or higher. The aqueous alcoholic solution, in the presence of the alkaline compound, is mixed with a water-immiscible, low-boiling point organic solvent for the oil-soluble petroleum sulphonates, preferably from about one-half to two volumes based on the aqueous alcohol solution, of a light petroleum hydrocarbon fraction predominantly non-aromatic, with a boiling range of about 170 DEG -250 DEG F. This solvent may be added prior to, simultaneously with or subsequent to the addition of the alkaline compound. The resulting mixture separates into two layers and the aqueous-alcoholic layer containing inorganic salts and any free alkali is separated from the solvent layer containing the oil-soluble sulphonates and some neutral oil. The sulphonates are obtainable from the solvent layer by distilling off the solvent. Preferably petroleum hydrocarbon oils containing naphthenic type hydrocarbons together with paraffin hydrocarbons are used as starting materials. Raffinates obtained by solvent extraction, e.g. by the Edeleanu process or by furfural extraction of mid-continent lubricating oil distillates are particularly suitable. Preferably the sulphonation takes place in several steps with separation of sludge between successive treatments. The water-immiscible organic solvent for the oil-soluble petroleum sulphonates may be any suitable, relatively low-boiling substance or mixture of such substances such as hydrocarbons boiling from 125 DEG to 135 DEG F. Preferred solvents are light naphtha fractions boiling from 170 DEG to 250 DEG F. containing a major proportion of non-aromatic hydrocarbons. The proportions of solvent used may vary from 1/4 to 10 times the volume of acid alcohol extract or the neutralized extract. Lower aliphatic alcohols which may be used for extracting the sulphurated mixture are monohydric alcohols having from one to three carbon atoms or glycols such as ethylene and propylene glycols or glycerol.