Sulfonation process with emphasis on economy of sulfonating agent

Claim 1

A PROCESS FOR EFFECTING MONO-SULFONATION OF A SULFONATABLE HYDROCARBON WHICH COMPRISES MIXING SAID HYDROCARBON WITH AN OLEUM CONTAINING FROPM 5 TO ABOUT 65% BY WEIGHT OF FREE SULFUR TRIOXIDE DERIVED AS HEREINAFTER INDICATED, THE AMOUNT OF SAID OLEUM CORRESPONDING TO A MOLAR RATIO OF FREE SULFUR TRIOXIDE IN SAID OLEUM TO SAID HYDROCARBON OF FROM ABOUT 0.9 TO 1 TO ABOUT 4 TO 1, WHILE MAINTAINING THE RESULTING MIXTURE OF OLEUM AND HYDROCARBON AT A SULFONATION TEMPERATURE, THEREAFTER ADDING WATER IN AN AMOUNT CORRESPONDING TO THE FORMULA: X=1+2N-2(1-N''), WHEREIN X IS EQUAL TO THE AMOUNT OF WATER ADDED, 2N IS EQUAL TO THE NUMBER OF MOLES OF SULFURIC ACID IN SAID OLEUM, AND N'' IS EQUAL TO THE NUMBER OF MOLES OF FREE SULFUR TRIOXIDE IN SAID OLEUM, SEPARATING A RESULTING SULFURIC ACID MONOHYDRATE PHASE FROM AN UPPER LAYER COMPRISI NG PREDOMINATELY THE MONOHYDRATE OF THE RESULTANT HYDROCARBON SULFONIC ACID AND ADDING SUFFICIENT SULFUR TRIOXIDE TO SAID SULFURIC ACID MONOHYDRATE PHASE TO FORM SAID OLEUM IN THE AMOUNT AND AT THE SULFUR TRIOXIDE CONCENTRATION UTILIZED IN SAID SULFONATION REACTION, AS AFORESAID, AND SUPPLYING THE OLEUM THUS FORMED FROM THE SULFURIC ACID MONOHYDRATE PHASE TOP THE SULFONATION REACTION AS SAID SULFONATING AGENT.