日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

Production of alkylbenzenes is one of the most important technologies on the chemical industry. p-Xylene is, in particular, much valuable in alkylbenzenes due to the steady increase of its market demand, and catalysts development for selective formation of p-xylene has been attractive because of the low p-xylene selectivity in the thermodynamic equilibrium and the high energy consumption on its separation from xylene isomers. For selective formation of p-xylene, MFI type aluminosilicate zeolite, ZSM-5 was coated with pure silica MFI, silicalite-1. The core-shell zeolite catalyst showed extremely high paraselectivity with high toluene conversion on the alkylation of toluene. The silcalite-1 layer with a few hundred nanometers was epitaxially grown on the ZSM-5 crystal resulting in the direct connection of pores between ZSM-5 and silicalite-1. This direct connection of pores and deactivation of acid sites on the external surface of the ZSM-5 crystal could achieve the remarkable para-selectivity with high toluene conversion.