The internal distribution of catalytically active metal within a supported metal catalyst can determine its activity, selectivity, and durability. Since the early 1950s, electron probe microanalysis has grown into a mature and widely available technique. By providing quantitative elemental analysis from volumes on the order of 1μm3, EPMA is uniquely suited for the study of metal concentration profiles in supported metal catalysts. However, independent knowledge of metal particle size or dispersion is needed to identify the catalytically active fraction of deposited metal. Most available techniques for metal particle size determination are indirect methods such as selective chemisorption. The transmission electron microscope is the only available device which is capable of resolving metal particles on the order of lnm in diameter. For years, the EPMA has been used in determining internal distributions of deposited metal within supported catalysts, while the TEM has been used to observe supported metal catalyst particles on powdered supports. However, there has been no study that combines both EPMA and TEM which attempts to furnish the information about a supported metal catalyst which is truly desired (its internal distribution of catalytically active metal). In the present work, a Pt/Al2O3 catalyst with a nonuniform internal distribution of deposited Pt was analyzed by incorporating EPMA and TEM.
Soot Particle Size Distribution Functions in a Turbulent Non-Premixed Ethylene-Nitrogen Flame
