Sulfuric acid refining of benzene

Claim 1

IN A PROCESS FOR PRODUCING BENZENE OF HIGH PURITY, IN WHICH A BENZENE-CONTAINING CHARGE MIXTURE IS CONTACTED WITH CONCENTRATED SULFURIC ACID TO REACT WITH IMPURITIES, TREATED WITH ALKALI TO NEUTRALIZE THE REMAINING ACID, AND THEN SUBJECTED TO FRACTIONAL DISTILLATION TO PRODUCE PURE BENZENE AND OTHER PRODUCTS, THE NOVEL STEPS COMPRISING: PRODUCING BY FRACTIONAL DISTILLATION AN OVERHEAD FRACTION COMPRISING PRIMARILY BENZENE AND BEING SUBSTANTIALLY FREE OF HEAVIER COMPONENTS, AND A RESIDUAL COMPRISING SUBSTANTIALLY ALL THE COMPONENTS HEAVIER THAN BENZENE TOGETHER WITH A PREDETERMINED QUANTITY OF BENZENE WHICH IS SUFFICIENT TO CONTAIN THE MAJOR PORTION OF THE REMAINING IMPURITIES BOILING IN THE BENZENE RANGE; PRODUCING BY FURTHER FRACTIONAL DISTILLATION OF SAID RESIDUAL AN INTERMEDIATE OVERHEAD FRACTION CONTAINING SUBSTANTIALLY ALL THE REMAINING MATERIAL BOILING IN THE BENZENE RANGE TOGETHER WITH SOME HIGHER-BOILING MATERIAL, AND A RESIDUAL SUBSTANTIALLY COMPRISING COMPONENTS HEAVIER THAN BENZENE; AND RECYCLING SAID INTERMEDIATE OVERHEAD FRACTION FOR FURTHER CONTACTING WITH SULFURIC ACID AND RE-FRACTIONATION.