Process for preparing a salt of a sulfurized alkyl-substituted hydroxyaromatic composition

A process for preparing a salt of a sulfurized alkyl-substituted hydroxyaromatic composition having a reduced content of unsulfurized alkyl-substituted hydroxyaromatic compound and its unsulfurized metal salt, the process comprising the steps of:

• (a) providing a composition comprising (i) a salt of a sulfurized alkyl-substituted hydroxyaromatic compound;
• (ii) an unsulfurized alkyl-substituted hydroxyaromatic compound and (iii) an unsulfurized metal salt of the alkyl-substituted hydroxyaromatic compound;
• wherein the alkyl-substituted hydroxyaromatic compound is derived from alkylation of a hydroxyaromatic compound with one or more olefins comprising C9 to C18oligomers of monomers selected from propylene, butylene or mixtures thereof;
• (b) protonating the unsulfurized metal salt of the alkyl-substituted hydroxyaromatic compound with an effective amount of an acidic compound capable of protonating the unsulfurized metal salt of the alkyl-substituted hydroxyaromatic compound;
• and
• (c) removing the unsulfurized alkyl-substituted hydroxyaromatic compound and the protonated unsulfurized metal salt of the alkyl-substituted hydroxyaromatic compound from the composition wherein the salt of the sulfurized alkyl-substituted hydroxyaromatic composition obtained in step (c) contains less than or equal to 2.45 wt. % of the unsulfurized alkyl-substituted hydroxyaromatic compound and its metal salt.