Abstract
The Si/Al ratio of a commercial HB-25 beta zeolite sample was increased by treatment of dealumination and silicon-insertion. Platinum ions were subsequently dispersed onto the starting and the treated samples through impregnation of aqueous Pt(NH 3) 4(NO 3) 2. Chemical environments of dispersed platinum were characterized by temperature-programmed reduction (TPR) technique. The obtained TPR traces varied with extents of dealumination. Nevertheless, three major signals, in reduction temperature regions around −50, 80 and 480°C were distinguished from these TPR traces and characterized as reductions of platinum oxides dispersed on the external surface of zeolite (Pt eO), platinum oxides occluded in channels (Pt oO x ), and Pt–(–O–Si) y complexes coordinated to external surface or defects of zeolite, respectively. From the variation in the contribution of the 480°C peak in TPR traces, a formation of Si–OH silanol function groups on the zeolite surface during the dealumination treatment and a elimination of these groups during the silicon-insertion treatment are indicated.
Published Version
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