Redispersion of Ptzeolite catalysts with chlorine

Abstract

Platinum supported on zeolites K-L, H-L, silanated H-L, H-ZSM 5 and silicalite was treated with chlorine in nitrogen or hydrogen chloride in air at 620 K. The catalysts were examined using X-ray diffraction, transmission electron microscopy and temperature-programmed reduction. Platinum redispersion was found to be linked to the formation of strongly bound platinum (IV) chloride species, which concentrations depended on the aluminium content of the zeolite. A redispersion scheme is proposed which involves splitting of some SiOAl linkages and bonding of the platinum halide species to the aluminium.