GB723185A - Process for the preparation of adducts of sulphur compounds and for the separation of sulphur compounds from hydrocarbons and from mixtures of sulphur compounds - Google Patents

Abstract

The invention comprises adducts formed of 1 mol. of an organic compound containing a divalent sulphur atom and 2 mols. of hexafluorophosphoric acid. They are made by contacting the compound with the acid or a mixture of hydrofluoric acid and phosphorus pentafluoride and contain 1 mol. of the compound and 2 mols. of the acid. Sulphur compounds instanced are dialkylsulphides, benzylalkylsulphides, alkylarylsulphides, benzothiophene and dibenzothiophene. Generally low temperatures, e.g. 0 DEG C., are necessary for adduct formation and since the temperature for adduct formation varies with the particular sulphur compound treated it is possible to separate mixtures of sulphur compounds, e.g. by treatment in stages of lower temperatures. Sulphur compounds may also be removed from admixture with hydrocarbons, e.g. petroleum hydrocarbons. When separating sulphur compounds from hydrocarbons an excess or stoichiometric quantity of the acid reactant is used, the sulphur compounds appearing in the extract phase or as a filterable solid. The acid reactant may be used in solution, e.g. dissolved in liquid sulphur dioxide. Water and water vapour are preferably absent. Mixtures of adducts may be separated by treatment with solvents, e.g. chloroform is a selective solvent for dialkylsulphide adducts. The adducts are decomposed into their components on heating and mixtures of adducts may thus be separated, e.g. by solvents such as pentane, benzene, toluene, liquid sulphur dioxide or diethylether, which dissolve the sulphur compounds but not the adducts and chloroform in which the adducts are only partially soluble. At relatively high temperatures, e.g. room temperature, pressure may be necessary. If the sulphur compounds decompose on heating they may be regenerated from their adducts by treating the latter with a strong base, e.g. aqueous caustic-alkali solution. In an example, a Mexican gas oil diluted with pentane is treated at 0 DEG C. with hexafluor-phosphoric acid in liquid sulphur dioxide to give an adduct which is filtered off and decomposed with aqueous caustic soda.ALSO:Divalent sulphur compounds are removed from petroleum hydrocarbons by treatment with hexafluorophosphoric acid or a mixture of hydrofluoric acid and phosphorus pentafluoride to form an adduct with the sulphur compound which is then separated from the hydrocarbon. When the quantity of acid reagent used is about equivalent to the quantity of sulphur compounds present a solid adduct is formed. The use of an excess of acid reagent leads to the production of an extract phase containing the sulphur compounds. Generally low temperatures e.g. 0 DEG C. are necessary for adduct formation. At higher temperatures e.g. room temperature, pressure may be applied. The acid reactant may be used in solution e.g. dissolved in liquid sulphur dioxide. Water and water vapour are preferably absent. Since the temperature of adduct formation varies with the particular sulphur compound treated it is possible to remove sulphur compounds stepwise by treatment at lowering temperatures. Sulphur compounds mentioned are dialkyl-benzylalkyl- and alkylaryl-sulphides and benzo- and dibenzothiophene. In an example a Mexican gas oil diluted with pentane is treated at 0 DEG C. with hexafluorophosphoric acid in liquid sulphur dioxide to give an adduct which is filtered off.