Kinetic and Infrared Study of the Effect of Metal Crystallite Size and Metal-Support Interactions on CO Hydrogenation Reactions: A Third-Year Progress Report

摘要

Platinum and palladium supported on four different oxide materials - SiO sub 2 , Al sub 2 O sub 3 , SiO sub 2 -Al sub 2 O sub 3 , and TiO sub 2 - have been studied in depth. Different preparative techniques were utilized to vary metal particle size and change the state of the metal. For example, Pt and Pd deposited on TiO sub 2 and reduced at low temperatures (175 to 200 exp 0 C) exhibit normal adsorption behavior, whereas these same catalysts reduced at a high temperature (500 exp 0 C) transform into an SMSI (Strong Metal-Support Interactions) state and chemisorption becomes greatly reduced. Both fresh and used samples were characterized by H sub 2 , and CO chemisorption. In addition, O sub 2 chemisorption and the H sub 2 -O sub 2 titration reaction were conducted on most fresh reduced Pt and Pd catalysts to further characterize their adsorption properties and to determine the agreement among these various chemisorption techniques. X-ray line broadening measurements were than conducted on all catalyst samples, and TEM was used to further characterize selected samples, especially the Ni catalysts. Metal loadings were determined by Neutron Activation Analysis. Tables 1 and 2 provide the chemisorption data on Pt and Pd catalysts respectively, and Tables 3 and 4 show the turnover frequencies (N) measured on Pt and Pd dispersed on various supports. (ERA citation 05:030067)