n-Hexane isomerization over Pt-Na(H)Y catalysts obtained by different preparation methods

Catalysts containing 0.5 wt.% of Pt on Na(H)Y zeolite with potentially high acidity were prepared alternatively by ion exchange and wetness impregnation. Their acidity was altered by altitude of calcination temperature and by the order of calcination and Pt-acid decomposition. The catalysts were tested in n-hexane isomerization reaction. It was shown that optimum selectivity with the maximal isomer yield was obtained for the catalyst where calcination and Pt-acid decomposition were hold simultaneously at high temperature. This was attributed to very well-balanced acidic and metallic sites due to optimal metal-support interaction. When the sequence of generation of acid sites was followed by Pt-acid decomposition in a separated temperature sequence, the catalyst with poor activity and selectivity was obtained. This is explained by the lower acidity and poorer metal dispersion as the result of different pretreatment procedure. (C) 2001 Elsevier Science B.V. All rights reserved.