Spatial Configurational Construction of Pt-ZSM-5 Bifunctional Catalysts for Hydroisomerization of n-Heptane

Design of efficient metal-acid bifunction catalysts is of significance for development of hydroisomerization of linear alkanes. In this study, the spatial configurational construction of Pt-ZSM-5 catalytic system was achieved by fabrication of acidic ZSM-5 zeolite and mesoporous silica core-shell composites equipped with controlled location of Pt sites, which aim to explore the effect of functional sites proximity on isomerization reactivity. A series of characterization techniques such as X-ray diffraction, transmission electronic microscopy, N2 physical adsorption, NH3 temperature programmed desorption, X-ray photoelectron spectroscopy and so on had confirmed that the synthesized core-shell bifunctional catalysts with different Pt location possessing similar textural, acid and metal properties. In the catalytic hydroisomerization of n-heptane, however, the catalyst with Pt sites locating at acid zeolite exhibits superior n-heptane conversion and isomerization selectivity, which indicates that proximity of active sites at atomic scale may be more conducive to their synergistic effect when the diffusional limitation from zeolitic channel is minimized. These results had presented new direction for the preparation of efficient bifunctional catalysts in hydroisomerization of linear alkanes.