Sulfonation of crude oils to produce petroleum sulfonates

In a process for the preparation of petroleum sulfonates comprising contacting sulfur trioxide with a hydrocarbon selected from the group consisting of whole crude oil, topped crude oil, and mixtures thereof in a reaction zone, at a temperature of from about 80.degree. to about 250.degree. F., at a pressure of from about 0.01 to about 150 atmospheres, and for a reaction time of from about 0.001 to about 3600 seconds wherein from about 5 to about 30 lbs. of sulfur trioxide are contacted with each 100 lbs. of hydrocarbon, the improvement comprising removing unreacted hydrocarbons after said contact with sulfur trioxide and thereafter neutralizing, with base, the produce obtained by said contact with sulfur trioxide, wherein said removal of hydrocarbons comprises the step of extracting the product mixture resulting from said contact of said sulfur trioxide with said hydrocarbon by contacting said product mixture with from about 0.8 to about 2.0 lbs. of an extraction solvent per lb. of said product mixture.