Abstract:
Two structurally similar polycyclic compounds can be separated by contacting a fluid feed mixture containing said compounds with a partially dehydrated molecular sieve zeolite, the ratio Al/Si of the zeolite being in the range of 0.65-0.2. The polycyclic compounds can be heterocyclic or carbocyclic. For example, selective adsorption of 2,7-dimethylnaphthalene from a dimethylnaphthalene concentrate is obtained with sodium Type Y molecular sieves. 2,6-Dimethylnaphthalene can then be crystallized from the unadsorbed raffinate fraction. Separation factors of 6 to 8 are obtained, indicating the unexpected high selectivity of these particular molecular sieves for this adsorption (especially compared to Type X zeolite). A continuous method is disclosed for adsorption and desorption of 2,7-dimethylnaphthalene utilizing Type Y zeolite. Type L zeolite can be used for adsorption and desorption of 2,6-DMN.
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. ($2*C.) TO AVOID DISSOLVING FREE 2,6-DMT.
Abstract:
2,6-DIMETHYLNAPHTHALENE (DMN) CAN BE RECOVERED IN HIGH YIELDS AND HIGH PURITY BY CAREFULLY CONTROLLING THE TEMPERATURE OF CRYSTALLIZATION AT THE TEMPERATURE DETERMINED FROM FIG. 2 AT WHICH ALL 2,6-/2,7-DMN EUTECTIC IS SOLUBLE IN THE LIQUIDS PRESENT. FOR EXAMPLE, A 495510$F. CATALYTIC GAS OIL DISTILLATE FRACTION CONTAINING
WT. PERCENT 2,6-DMN 25 2,7-DMN 28 OTHER 47
WILL HAVE A EUTECTIC OF 2,6-/2,7-DMN IN THE WT. RATIO OF .725/1 THUS THE EUTECTIC REPRESENTS 48.3% OF INCOMING FEED. TO USE FIG. 2, THE WT. PERCENT OF EUTECTIC IS CALCULATED ON TOTAL FEED, EXCLUDING FREE 2,6-DMN, IN THIS CASE 50.6 WT. PERCENT EUTECTIC. FROM FIG. 2, 50.6 EUTECTIC IS SOLUBLE AT 37* C. THE TEMPERTURE OF CRYSTALLIZATION SHOULD BE NO LESS THAN 37* C. ($2*C.) TO AVOID CRYSTALLIZATION OF THE 2,6-/2,7-EUTECTIC AND NO MORE THAN 37* C. ($2* C.) TO AVOID DISSOLVING FREE 2,6-DMN.