Production of xylenes

Claim 1

IN A PROCESS FOR THE PRODUCTION OF XYLENES WHICH COMPRISES THE STEPS OF: SUBJECTING A HYDROCARBON FRACTION CONSISTING ESSENTIALLY OF A PREDOMINANT PROPORTION OF DIMETHYLCYCLOHEXANE HYDROCARBONS AND OF OPEN-CHAIN PARAFFIN HYDROCARBONS WITH SIMILAR VOLATILITY TO SAID DIMETHYLCYCLOHEXANES AND TO XYLENES, TO CATALYTIC DEHYDROGENATION UNDER CONDITIONS TO DEHYDROGENATE AT LEAST A SUBSTANTIAL PORTION OF SAID DIMETHYLCYCLOHEXANES TO CORRESPONDING XYLENES, WHILE LEAVING A SUBSTANTIAL PORTION OF UNCHANGED DIMETHYLCYCLOHEXANES, THEREBY PRODUCING A MIXTURE CONSISTING ESSENTIALLY OF XYLENES, UNCHANGED DIMETHYLCYCLOHEXANES AND SAID PARAFFIN HYDROCARBONS; FRACTIONALLY DISTILLING SAID MIXTURE AND SEPARATING THEREFROM A XYLENES FRACTION CONTAINING ESSENTIALLY ALL OF SAID XYLENES IN SAID MIXTURE; SUBJECTING SAID SEPARATED XYLENES FRACTION TO EXTRACTIVE DISTILLATION WITH A PHENOL AT A TEMPERATURE ABOVE THE BUBBLE TEMPERATURE OF SAID XYLENES FRACTION TO SEPARATE SAID XYLENES AS AN EXTRACT IN SAID PHENOL FROM THE NON-AROMATIC HYDROCARBONS IN SAID XYLENES FRACTION; AND RECOVERING THE XYLENES FROM SAID EXTRACT; THE IMPROVEMENT WHICH COMPRISES CARRYING OUT THE FRACTIONAL DISTILLATION OF THE MIXTURE CONSISTING ESSENTIALLY OF XYLENES, UNCHANGED DIMETHYLCYCLOHEXANES AND PARAFFIN HYDROCARBONS AT A SUFFICIENTLY HIGH TEMPERATURE SO AS TO REMOVE ESSENTIALLY ALL OF THE UNCHANGED DIMETHYLCYCLOHEXANES FROM THE XYLENES AND TO SEPARATE THEREFROM A XYLENES FRACTION WHICH IS ESSENTIALLY FREE FROM DIMETHYLCYCLOHEXANES.