(233a) Methods to Study Catalysts Under Reaction Conditions

The most useful way to probe a catalyst is under reaction conditions as its properties are usually dependent on the reaction environment.  The catalyst can be probed in order of usefulness and experimental difficulty as: 1- in situ, 2- operando or 3- under dynamic conditions.  We will discuss examples, including the description of experimental techniques, for all three modes with examples from water-gas shift and selective catalytic reduction with ammonia.  The methods discussed will include environmental transmission electron microscopy, x-ray absorption spectroscopy and infrared spectroscopy.  We make extensive use of model catalysts to take best advantage of these techniques. Metal catalysts deposited on non-porous supports of simple geometry are ideal to explore structure-property relationships.  They fulfill three requisites: 1-there is no porosity and thus all particles are accessible for observation by TEM 2-the supports have geometries that allow for profile TEM and studies on single metal particles, 3-the surface area is high enough for the usual characterization probes (e.g., chemisorption and kinetics).  In addition, surface density can be controlled and a tight particle size distribution can be achieved.