Study of the zeolite-catalyzed isomerization of 1-methylnaphthalene.

Isomerization of 1-methylnaphthalene (1-MN) to 2-methylnaphthalene (2-MN) is a crucial step in the production of 2,6-dimethylnaphthalene (2,6-DMN), which is an important raw material for polyethylene naphthalate (PEN). Herein, the isomerization of 1-MN was systemically investigated over beta zeolite. Firstly, reaction conditions were systemically optimized, by which enhanced catalytic performance was obtained. Thereafter, the effect of nitride on the catalytic performance was investigated using a series of characterization techniques and DFT calculations, revealing that firm adsorption of nitride on acid sites was the main reason for catalyst deactivation. Activity of the deactivated catalyst was difficult to recover via extraction with hot benzene. Fortunately, catalytic performance could be effectively recovered through coke-burning, wherein the framework and acid sites were well-preserved during calcination.