Aromatics production

Claim 1

IN THE METHOD OF PRODUCING BENZENE AND EXYLENES FROM A HYDROCARBON REFORMATE RICH IN AROMATICS THE IMPROVEMENT WITH COMPRISES: REMOVING HYDROCARBONS BOILING BELOW ABOUT 75-78*C. FROM SAID REFORMATE; FRACTIONATING THE REMAINING HYDROCARBNS AFTER SUCH SEPARATION INTO (A) A LIGHT FRACTION COMPOSED PREDOMINANTLY OF C6 TO C8 HYDROCARBONS, AND (B) A HEAVY FRACTION CONSISTING ESSENTIALLY OF C9 AND HIGHER HYDROCARBONS; EXTRACTING AROMATIC HYDROCARBONS FROM SAID LIGHT FRACTION (A); SUBJECTING SAID HEAVY FRACTION (B) TO SELECTED CONDITIONS OF MILD HYDROGENATIVE DEALKYLATION AT TEMPERATURES BETWEEN ABOUT 1100 AND ABOUT 1150*F. OVER ACTIVE CHROME-ALUMINA CATALYST FAVORING PRODUCTION OF EXYLENES; SEPARATING C6 TO C8 HYDROCARBONS FROM SAID MILD DEALKYLATION WHILE CONTINUOUSLY RECYCLING TO SAID DEALKYLATION PRODUCTS BOILING ABOVE EXYLENES; COMBINING THE SEPARATED C6 TO C8 HYDROCARBONS STREAM WITH SSAID AROMATIC EXTRACT STREAM FROM THE LIGHT FRACTION AND SUBJECTING THE COMBINED STREAMS OF FRACTIONAL DISTILLATION TO PROVIDE: (C) AN OVERHEAD CUT CONSISTING SUBSTANTIALLY OF BENZENE; (D) A BOTTOMS CUT COMPOSED ESSENTIALLY OF C8 AROMATIC HYDROCARBONS PREDOMINATING IN EXYLENES; AND (E) A MIDDLE CUT CONSISTING ESSENTIALLY OF TOLUENE; SUBJECTING SAID MIDDLE CUT (E) TO SEVERE DEMETHYLATION OVER ACTIVE CHROME-ALUMINA CATALYST AT TEMPERATURES BETWEEN ABOUT 1000 AND ABOUT 1200*F. UNDER SELECTED CONDITIONS FAVORING PRODUCTION OF BENZENE; REMOVING PRODUCTS BOILING BELOW BENZENE FROM THE EFFLUENT FROM SAID SEVERE DEMETHYLATION REACTION, WHILE RETURNING THE PRODUCTED BENZENE AND UNREACTED TOLUENE TO FRACTIONAL DISTILLATION WITH THE AFORESAID COMBINED STREAMS SO AS TO OBTAIN (1) ADDITIONAL RECOVERED BENZENE PRODUCTS AND (2) TOLUENE FOR RECYCLING TO DEMETHYLATION; AND CONTROLLING THE MILD DEALKYLATION OF THE C9 PLUS HYDROCARBONS FRACTION TO PROVIDE SHORTER RESIDENCE TIME THAN THAT EMPLOYED IN THE SEVERE DEMETHYLATION OF THE TOLUENE.