Separation of 2,6-dimethylnaphthalene from a mixture of its isomers using lithium-incorporated zeolite Y synthesized by rapid crystallization method

Abstract

Lithium-incorporated zeolite Ys (Li-NaYs) were directly synthesized under a hydrothermal condition from a gel mixture of Li 2O·Na 2O·SiO 2·Al 2O 3·H 2O. It was confirmed by XRD, NMR and elementary analysis, that lithium ions could be introduced onto the ion sites of zeolite Y during the course of crystallization. Usage of lithium citrate as the lithium source is the indispensable factor to achieve the synthesis. In adsorption of mixtures of 2,6-dimethylnaphthalene and its isomers, Li-NaYs exhibited greater adsorptive capacities and higher adsorption selectivities to 2,6-dimethyl naphthalene than NaY. Direct hydrothermal synthesis of Li-incorporated zeolite Y prevents the blockage of pore openings and/or channels during lithium ion-exchange. Furthermore, the difference in adsorptive properties between Li-NaY and Li ion-exchanged NaY is due to Li ions being introduced onto the S 1 ion sites, which can hardly be ion-exchanged, during the hydrothermal synthesis.