In-Situ UV Diffuse Reflectance Studies in Heterogeneous Catalysis: Progress Report, December 1, 1987--November 30, 1988.

摘要

The effect of catalyst pretreatment on the surface composition of supported bimetallic clusters is currently under study using the following techniques: (1) in-situ diffuse uv spectroscopy, (2) differential scanning calorimetry and (3) electron microscopy. In- situ uv diffuse reflectance spectroscopy is being used to study the nature of the surface diffusion of the precursor over the silica support. Quantitative differential scanning calorimetry is currently being used to compare heats of reduction of the pure metal precursors to those obtained for the supported catalysts. It is proposed that this study will enable us to arrive at the correct reduction sequence. Scanning transmission electron microscopy (STEM) is currently under use to determine the composition distribution of the supported bimetallic particles over the catalyst surface. EDXS, electron diffuse x-ray spectroscopy is being used to determine the elemental analysis of individual catalyst particles. Catalytic reactions are being used as surface probes to establish the nature and distribution of the dual metal sites obtained on the supported bimetallic particles. Ensemble sizes and their roles in heterogeneous catalyzed reactions are being investigated. 5 refs. (ERA citation 13:049189)