Selective synthesis of 2,6-dimethylnaphthalene by methylation of 2-methylnaphthalene with methanol on Zr/(Al)ZSM-5

A new catalyst, Zr/(Al)ZSM-5, prepared by partly isomorphic substitution of Al in ZSM-5 framework by Zr, was used to synthesize 2,6-dimethylnaphthalene (DMN) by methylation of 2-methylnaphthalene (MN) with methanol. The catalyst exhibits higher selectivity of DMNs, 2,6-DMN and β,β-DMNs, 2,6- to 2,7-DMN ratio and lower isomerization than unmodified ZSM-5. About 10% of 2-MN conversion, 56% of 2,6-DMN selectivity, ratio of 2,6- to 2,7-DMN being 3.0 are obtained on Zr/(Al)ZSM-5. The improvement in catalytic performance is mainly attributed to the weakening of acid strength and the expansion of pore dimension from partial incorporation of Zr in ZSM-5 framework.