Patent GB-592924-A (GB)
Title: Prevention of oxidation in hydrocarbon oils and the manufacture of aryl sulfides therefor
IPC: F02B75/16
Filed: 1945-06-12
Abstract: Mineral lubricating oils, particularly motor oils, are improved with regard to their resistance to oxidation, non-corrosion of bearings, and anti-ring sticking properties by the addition of a small proportion, e.g., 0.1 per cent. to 2.0 per cent. of a compound of the formula RAr(XM)Sx(MX)ArR in which Ar is an aromatic nucleus, R is a branched chain aliphatic hydrocarbon radical containing at least 14 carbon atoms, X is a non-metallic element of Group VI of the Periodic Table, M is a metallic equivalent of hydrogen, S is sulphur, and x is an interger from 1 to 4.  The compound may be a metal salt of an alkylated phenol sulphide, the alkyl group may contain 16 to 20 carbon atoms and the metal may be a divalent metal of Group II of the Periodic Table especially calcium, barium, strontium, magnesium or zinc. The alkylating material may be a mixture of polymers of C4 hydrocarbons, having a boiling range of about 400 to 600 DEG F., e.g., a refinery C4 cut containing unsaturated hydrocarbons, polymerized by treatment with sulphuric acid, such as "naphtha rerun tower bottoms," occurring as a by-product in the manufacture of secondary butyl alcohol from a C4 cut from refinery cracking operations.  The phenol may be alkylated in the presence of hydrochloric acid and a Friedel-Crafts catalyst such as anhydrous aluminium chloride, the mixture of phenol and butene polymer in equimolecular proportion being, for example, saturated with hydrochloric acid, the aluminium chloride added with stirring and the catalyst and unreacted phenol then removed by water-washing.  Any unreacted material not thus removed may be taken off as an overhead by distilling to 400 DEG F. with fire and steam.  The alkyl phenols thus produced are converted to phenol sulphides by the conventional processes, e.g., by reacting them with sulphur monochloride or dichloride in the ratio of 2 mols of phenol to 1-2 mols of sulphur halide in the presence of a suitable organic solvent.  To prepare the metal salts, the alkyl phenol sulphides are preferably dissolved in mineral oil and neutralized with a metal oxide or hydroxide, e.g., Ba(OH)28H2O, using a defoaming aid and plasticiser, such as stearyl alcohol.  The additives may be prepared in the form of concentrates in mineral lubricating oil, the mixture containing 25-75 per cent, of additive.  The concentrate may also contain stearyl alcohol, e.g., about 40 per cent. of barium salts of alkylated phenol sulphides, about 10 per cent. of stearyl alcohol, and about 50 per cent. of mineral lubricating oil.  0.625 per cent. of such concentrate in an S.A.E. 20 solvent-extracted paraffinic mineral lubricating oil very markedly reduced the corrosion of copper-lead bearings in 8 hours at 325 DEG F. with air blown through the oil.  Comparative tests in a single cylinder Caterpillar Diesel engine showed that an oil containing 1 per cent. of barium C16-C20 branched chain alkyl phenol sulphide-disulphide and 0.25 per cent. of stearyl alcohol was superior in engine cleanliness, and particularly piston skirt varnish, to either the plain oil or oils containing 1 per cent. of either the corresponding C8 or C16-C20 straight chain additives and 0.25 per cent. stearyl alcohol.  The metal salts of phenol sulphides which have highly branched long chain substituent aliphatic radicals containing 14 or more carbon atoms are superior in detergent qualities, oil solubility, and resistance to removal from solution in oil by intimate contact with a small amount of water, to metal salts of phenol sulphides in which the alkyl groups consist of comparatively short chains, containing 4 to 8 carbon atoms each (e.g., the alkaline earth metal salts of tertiary amyl phenol sulphide, tert.-octyl phenol sulphide, and di-tert.-amyl phenol sulphide).  A greater variety of mineral lubricating oil base stocks give good inhibitor response with the additives in which the alkyl groups contain 14 or more carbon atoms than with those containing only 4 to 8 carbon atoms.  The former are also superior in oil solubility and still more superior in detergency, to straight chain wax alkylated phenol sulphide salts.  Specifications 513,774, 547,972 and 555,053 are referred to.ALSO:Metal salts of alkaryl sulphides of the general formula RAr(XM)Sx(MX)ArR in which Ar is an aromatic nucleus, R is a branched chain aliphatic hydrocarbon radical containing at least 14 carbon atoms, X is a non-metallic element of Group VI of the Periodic Table, M is a metal equivalent of hydrogen, S is sulphur and x is an integer from 1 to 4, for use as oxidation and corrosion inhibitors in mineral lubricating oils, are obtained by alkylating a phenol in the presence of anhydrous aluminium chloride and hydrogen chloride with a mixture of polymers of unsaturated C4 hydrocarbons having a boiling range of about 400-600 DEG  F.  The alkyl phenols thus produced are converted to sulphides by reacting them with sulphur mono- or dichloride in chloroform solution and finally the metal salt produced by reacting the alkylated phenol sulphide with a base of the metal or by other methods such as double decomposition.  Various phenols such as phenol, cresols, xylenols, phenyl phenol, petroleum phenols, resorcinol, alpha and beta naphthols, &c. may be used as starting materials.  In examples: (1) sulphuric acid is slowly added to a butene polymer boiling in the range 400-600 DEG  F. and phenol in a cooled vessel and the mixture allowed to stand several hours.  Water is added to effect the hydrolysis of the sulphonic acid groups.  The alkylated phenol layer is washed with alkali and water.  After purification a final product having alkyl side chains containing on an average 19 carbon atoms is obtained; (2) the alkylated phenol is refluxed with chloroform and sulphur dichloride to form the alkylated phenol sulphide.  A 40 per cent concentrate in mineral lubricating oil of the barium salts of the mixed monosulphides and disulphides thus obtained is prepared; (3) phenol is alkylated with butene polymers of 400-600 DEG  F. boiling range using anhydrous aluminium chloride and hydrogen chloride as catalysts; (4) the product thus obtained is converted into the mono- or disulphide by refluxing it with sulphur di- or monochloride in chloroform solution and converted into a solution of the barium salt in mineral lubricating oil as in example (2). Specifications 513,774, [Group III], 547,972 and 555,053 are referred to.