Process for the production of 2, 6-dimethylnaphthalene

Claim 1

IN A PROCESS INVOLVING, (1) HYDRODESULFURIZING A PETROLEUM FRACTION BOILING MAINLY IN THE RANGE OF 440*-525*F. AND CONTAINING MAINLY MONOCYCLIC AND DICYCLIC AROMATIC HYDROCARBONS INCLUDING DIMETHYLNAPHTHALENES, (2) SEPARATING FROM THE DESULFURIZATION PRODUCT MATERIAL CONTAINING ALKYLNAPHTHALENES, (3) SUBJECTING SUCH MATERIAL TO A DEALKYLATION REACTION AT A TEMPERATURE ABOVE 1000*F. TO PRODUCE NAPHTHALENE AND, (4) RECOVERING FROM THE DEALKYLATION PRODUCT NAPHTHALENE AND A FRACTION RICH IN MONOALKYLNAPHTHALENE, THE STEPS FOR PRODUCING AND RECOVERING 2,6-DIMETHYLNAPHTHALENE WHICH COMPRISES: (A) SEPARATING FROM THE HYDRODESULFURIZATION PRODUCT A FRACTION BOILING ESSENTIALLY IN THE RANGE OF 500*-510*F., (B) FRACTIONALLY CRYSTALLIZING IN A FIRST CRYSTALLIZATION ZONE THE 500*-510*F. FRACTION TO SEPARATE 2,6- AND 2,7-DIMETHYLNAPHTHALENE FROM OTHER DIMETHYLNAPHTHALENES, (C) PASSING THE FILTRATE FROM STEP (B), MATERIALS FROM STEP (A) BOILING BELOW 500*F. AND ABOVE 510*F., AND SAID FRACTION RICH IN MONOALKYLNAPHTHALENE TO SAID DEALKYLATION REACTION FOR CONVERSION TO NAPHTHALENE, (D) FRACTIONALLY CRYSTALLIZING IN A SECOND CRYSTALLIZATION ZONE THE 2,6- AND 2,7-DIMETHYLNAPHTHALENE PRODUCT FROM STEP (B) TO SEPARATE THE 2,6DIMETHYLNAPHTHALENE FROM THE 2,7-DIMETHYLNAPHTHALENE, (E) RECOVERING THE 2,6-DIMETHYLNAPHTHALENE, (F) ISOMERIZING THE 2,7-DIMETHYLNAPHTHALENE FROM STEP (D) TO A MIXTURE RICH IN 2,6- AND 2,7DIMETHYLNAPHTHALENE, AND, (G) RECOVERING 2,6-DIMETHYLNAPHTHALENE FROM SAID MIXTURE.