Unexpected roles of toluene in the catalytic isomerization of 1,5- to 2,6-dimethylnaphthalene

Catalytic isomerization of 1,5- to 2,6-dimethylnaphthalene (DMN) over H-beta zeolite was carried out in a continuous flow fixed bed system by using toluene as a solvent in this study. Feed flow rates, reaction temperatures and feed concentrations were varied to investigate their effect on the isomerization in the presence of the solvent. Interestingly, it was found that the presence of toluene leads to the modification of the reaction thermodynamics, resulting in the ease of the isomerization to be occurred at significant lower temperatures, besides its roles to facilitate the reaction for the flow system by dissolving the solid reactant (1,5-DMN) and enhance the system mass transfer. As a result, the maximum yield of 2,6-DMN as in the high temperature equilibrium of the solvent-free system could possibly be approached at even low temperatures when the system is not limited by mass transfer of the DMN species and the reaction kinetics.