Method for selectively removing basic nitrogen compounds from lube oils

Abstract

A method is disclosed for the selective removal of basic nitrogen compounds (BNC) from natural and synthetic hydrocarbon feedstocks, preferably petroleum feedstocks, most preferably lube and transformer oils, which method comprises mixing the feedstock oil with a nonaqueous solution of anhydrous nonpolymeric Group IVb, Group Vb, Group VIb, Group VIIb, the non-noble (iron group) metals of Group VIII, copper, zinc, cadmium, and mercury halides (except TiCl.sub.4 or FeCl.sub.3) or tetrafluoroborates, complexed with non-aqueous polar solvents under conditions of agitation and mild heating whereby the basic nitrogen compounds exchange with the polar solvent to complex with the above-recited metal halides and metal tetrafluoroborates. The preferred halide is bromide, and the preferred polar solvent is methanol. The oil is then decanted to separate it from the metal halides: BNC complexes and the decantate washed with a polar solvent, which preferably includes water, and dried. The basic nitrogen compound-metal halide or metal tetrafluoroborate complex dissolves in the polar solvent, and that which is in the oil is removed by the polar solvent wash. The preferred polar solvent for the wash step is water. By the practice of this method, the basic nitrogen compound content of the oil is reduced by at least 90%. The anhydrous nonpolymeric metal halide or metal tetrafluoroborate-nonaqueous polar solvent complex can be used as such, or they can be impregnated onto a support material.