Shape Selective Disproportionation of Methylnaphthalene on ZSM-5 Catalyst

The conversion of 2-methylnaphthalene (2-MN) was studied at atmospheric pressure in a flow-type fixed bed reactor using H-Y, H-beta, H-mordenite, H-ZSM-5, H-ZSM-11 and H-ZSM-48 as catalysts. H-Y and H-beta exhibited high activities for disproportionation and isomerization of 2-MN. H-Mordenite and zeolites having medium size pores were active for the conversion of 2-MN which was mainly isomerized to 1-MN. The low disproportionation activities of these zeolites resulted from their shape selective properties. Disproportionation of 2-MN on the zeolite catalysts gave 2,6- and 2,7-dimethylnaphthalenes (DMN) in higher proportions than the thermodynamically attainable level. H-ZSM-5 was the most selective catalyst to produce these DMN isomers among the zeolite catalysts tested, although 2,7-DMN was formed in a higher proportion than 2,6-DMN. On H-mordenite catalyst, 2,6-DMN was more selectively formed than 2,7-DMN. The selectivity for 2,6-DMN against 2,7-DMN increased with increasing SiO 2 /Al 2 O 3 ratio of H-mordenite. It is suggested that the composition of DMN isomers produced by disproportionation of 2-MN depends on the acid strength as well as on the shape selective properties of zeolites used.