Patent ID: 7795489

Claim:
A method for separation and purification of 2,6-dimethylnaphthalene, which comprises a step of subjecting a dimethylnaphthalene isomer mixture rich in 1,5-dimethylnaphthalene, high boiling point materials, unreacted 1,5-dimethyltetralin, and low boiling point materials, which are produced from a dehydrogenation reaction of 1,5-dimethyltetralin, to separation, using a distillation column; a step of subjecting the dimethylnaphthalene mixture separated by the distillation column to liquid state isomerization in the presence of an isomerization catalyst; a first crystallization step (melt crystallization process) of cooling the product of the liquid state isomerization with a refrigerant without a solvent to form crystals; a second crystallization step (solution crystallization process) of mixing the crystals produced in the first crystallization step with an ethanol solvent to form crystals a step of separating mother liquor separated in the first and second crystallization steps to a solvent and DMN isomers by distillation; and a step of using the solvent separated in the step of separating the mother liquor for the second crystallization step and recycling the separated DMN isomers in the step of separating the mother liquor to the distillation column, wherein a cooling temperature of the first crystallization step is in the range of 90 to 0° C. and cooling rates of the first crystallization step and the second crystallization step are in the range of 0.5 to 1° C./min, wherein the purification by the distillation column comprises a step of separation and purification of low boiling point materials to separate low boiling materials; and a step of separation and purification of high boiling point materials to separate high boiling materials, wherein the distillation column at the step of separation and purification of low boiling point materials is operated such that the pressure and the temperature of the top of the tower are 60 to 150 mmHg and 160 to 200° C., respectively, and the temperature of the bottom of the tower is 176 to 220° C., and wherein the distillation column at the step of separation and purification of high boiling point materials is operated such that the pressure and the temperature of the top of the tower arc 30 to 80 mmHg and 150 to 170° C., respectively, and the temperature of the bottom of the tower is 190 to 250° C.