A process for preparing a synthetic petroleum sulfonate comprising (a) reacting at least one aromatic compound with a mixture of olefins selected from olefins having from about 8 to about 100 carbon atoms, in the presence of an acidic ionic liquid catalyst, wherein the resulting product comprises at least about 50 weight percent of a 1,2,4 tri-substituted aromatic compound or a 1,2,3 tri-substituted aromatic compound or mixtures thereof; (b) reacting the product of (a) with sulfur trioxide, which has been diluted with air; and (c) neutralizing the product of (b) with an alkali or alkaline earth metal hydroxide.