Preparation of aromatic hydrocarbons

Claim 1

METHOD OF PRODUCING HIGH PURITY AROMATIC HYDROCARBONS WHICH COMPRISES DISTILLING A PETROLEUM STOCK TO PRODUCE A FRACTION CONTAINING C6 AND C7 NAPHTHENES AND ANOTHER FRACTION CONTAINING C8 NAPHTHENES AND BOILING ESSENTIALLY BELOW THE BOILING RANGE OF XYLENES, CONTACTING THE FIRST-MENTIONED FRACTION WITH A DEHYDROGENATING CATALYST UNDER CONDITIONS EFFECTIVE TO CONVERT CONTAINED NAPHTHENES TO BENZENE AND TOLUENE, CONTACTING THE SECOND-MENTIONED FRACTION WITH A DEHYDROGENATING CATALYST UNDER CONDITIONS EFFECTIVE TO CONVERT CONTAINED NAPHTHENES TO XYLENES DISTILLING REACTION PRODUCT RESULTING FROM THE SECOND CONTRACTING STEP TO SEPARATE A XYLENE-RICH PRODUCT PASSING THE XYLENE-RICH PRODUCT TO A SOURCE OF SUPPLY, AND RECOVERING BENZENE AND TOLUENE FROM REACTION PRODUCT OF THE FIRST CONTACTING STEP BY MEANS OF A CYCLIC OPERATION IN EACH CYCLE OF WHICH SUCH REACTION PRODUCT IS CONTRACTED WITH AN AROMATIC-SELECTIVE ADSORBENTN IS CONTO ADSORB BENZENE AND TOLUENE WHILE DISPLACING XYLENE REMAIMING IN THE ADSORBENT FROM THE PRECEDING CYCLE, AFTER WHICH THE ABSORBENT IS CONTACTED WITH XYLENE-RICH PRODUCT FROM THE SOURCE TO SUPPLY A DISPLACE THE BENZENE AND TOLUENE COLLECTING EFFIUENT FROM THE ADSORBENT IN TWO PORTIONS ONE OF WHICH IS COMPOSED MAINLY OF NONAROMATIC HYDROCARBONS AND XYLENE AND ANOTHER OF WHICH IS COMPOSED MAINLY OF BENZENE, TOLUENE AND XYLENE, DISTILLING EACH PORTION TO RECOVER XYLENE-RICH PRODUCT THEREFROM, RETURNING XYLENERICH PRODUCT TO SAID SOURCE OF SUPPLY, AND REMOVING FROM THE SYSTEM XYLENE-RICH PRODUCT CONTAINING XYLENE USED IN SAID CYCLIC OPERATION TO THEREBY PREVENT PROGRESSIVE CONTAMINATION OF XYLENE BY SATURATE HYDROCARBONS BOILING ABOVE TOLUENE.