Isomerization of 1,5- to 2,6-dimethylnaphthalene and its thermodynamic aspects

Study on liquid phase isomerization of 1,5- to 2,6-dimethylnaphthalene (DMN) was conducted in a batch reactor using acidic zolite catalysts. The effect of catalyst amount, catalyst type, and reaction temperature were investigated before thermodynamic study. The results showed that H-beta zolite was the best catalyst for the reaction. Interestingly, the isomerization of 2,6-DMN from 1,5-DMN under particular conditions was not only limited by the thermodynamic equilibrium, but also by the kinetic control of the first isomerization step from 1,5-DMN to 1,6-DMN. Both restrictions should be properly manipulated in order to maximize the 2,6-DMN production. The thermodynamic study indicated an endothermic characteristic of the isomerization and provided information about thermodynamic properties of 1,5- and 1,6-DMN and equilibrium constant of the reactions that had not been reported before in literatures.