Fundamental Studies of Metal Dispersion for Uniformly and Nonuniformly Distributed Catalysts

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The objective of this project is to establish a scientific basis for the prediction of catalyst dispersion from fundamental studies of the impregnation step of catalyst preparation. Techniques must first be developed for this new approach. Experiments will be designed in which the number of coupled elementary processes of impregnation is minimized. Thus, the first type of system to be studied will be adsorption over a planar substrate. A high-resolution electron microscopy technique will be employed with a special "cold stage" to enable direct, detailed observation of catalyst precursor morphology just after impregnation. A second scheme will be designed for strongly adsorbing systems to permit measurement of an adsorption isotherm from the liquid phase (by atomic adsorption) and measurement of dispersion directly from the solid phase (by chemisorption and possibly TEM) for the same catalyst batch. A third apparatus will be designed to investigate the variation of dispersion with position in nonuniformly distributed catalysts. Different one-dimensional distribution profiles will be produced in an elongated catalyst sample, containing sufficient material so that the bulk metal concentration and metal dispersion can be measured for discrete sections along the sample length. In all cases, direct measurements of catalyst dispersion will be compared to existing impregnation theory. Finally, revised theory will be developed where needed, using as a basis these relatively simple impregnation systems. These studies are intended to provide a background to design of catalyst system preparation procedures that would give predictable results, in contrast to the trial-and-error methods now in use.