Sample preparation and electron microscopy of hydrocracking catalysts

This work focuses on the preparation of zeolite and alumina hydrocracking catalysts for investigation by electron energy-loss spectroscopy (EELS). EELS can potentially give new insights into the location and structure of coke which can result in catalyst deactivation. Three sample preparation techniques have been used - microtoming, focussed ion beam milling (LIB) and conventional ion beam milling. Crushing and grinding the catalyst pellets has been discounted as a preparation technique as the spatial relationship between the coke and the catalyst is lost using this method. Microtomed sections show some mechanical damage while sections milled in a single beam LIB microscope show gallium decoration in pores and were too thick for EELS. Conventional ion beam milling has proved to be most successful as it results in extensive thin regions and maintains the spatial distribution of the zeolite and alumina phases.