Separation of 2,6-and 2,7-dmn eutectic via 2,6-dimethyltetrahydronaphthalene crystallization

Abstract

Abstract ESSENTIALLY ALL OF THE 2,6-DIMETHYLNAPHTHALENE (DMN) CONTAINED IN THE 2,6-/2,7-DIMETHYLNAPHTHALENE EUTECTIC MIXTURE CAN BE RECOVERED BY HYDROGENATING THE EUTECTIC MIXTURE TO PRODUCE A MIXTURE OF 2,6- AND 2,7-DIMETHYLTETRALIN (DMT). THE 2,6/2,7-DMT ALSO FORMS A EUTECTIC, HOWEVER, IT IS AT A DIFFERENT RATIO THAN THE 2,6/2,7-DMN. THE SHIFT IS IN FAVOR OF GREATER 2,7-DMT IN THE EUTECTIC THUS THERE IS FREE 2,6-DMT THAT CAN BE RECOVERED FROM THIS MIXTURE. 2,6-DMT CAN BE RECOVERED IN HIGH YIELDS AND HIGH PURITY BY CAREFULLY CONTROLLING THE TEMPERATURE OF CRYSTALLIZATION AT THE LOWEST TEMPERATURE DETERMINED FROM FIG. 3 AT WHICH ALL OF THE 2,6-/2,7-DMT EUTECTIC IS SOLUBLE IN THE LIQUIDS PRESENT. FOR EXAMPLE, A HYDROGENATED 2,6-/2,7-DMN EUTECTIC FEED CONTAINING WT. PERCENT 2,6-DMT 30 2,7-DMT 30 OTHER LIQUID AROMATICS 40 WILL HAVE A EUTECTIC OF 2,6-/2,7-DMT IN THE WEIGHT RATIO OF .538. THUS, THE EUTECTIC REPRESENTS 46.2% OF THE INCOMING FEED. TO USE FIG. 3, THE WEIGHT PERCENT OF EUTECTIC IS CALCULATED ON TOTAL FEED EXCLUDING THE FREE 2,6-DMT IN THIS CASE THE WEIGHT PERCENT OF EUTECTIC TO BE DISSOLVED IS CALCULATED TO BE 53.6 WT. PERCENT. FROM FIG .3, 53.66 WT. PERCENT EUTECTIC IS SOLUBLE AT -51*C. THE TEMPERATURE OF CRYSTALLIZATION SHOULD BE NO LESS THAN -51*C. ($2*C.) TO AVOID CRYSTALLIZATION OF THE 2,6-/2,7-DMT EUTECTIC AND NO MORE THAN -51*C. ($2*C.) TO AVOID DISSOLVING FREE 2,6-DMT.

Inventors

• 👤 John A Hedge
• 👤 Kenneth A Scott

Bibliographic Details