Fundamental catalytic studies often attempt to relate the reactivity of a catalyst to its structure and composition. One of the difficulties is that the catalyst composition before and after reaction, quite often, is different than its composition during reaction. X-ray photoelectron spectroscopy (XPS) is highly surface sensitive (less than 2 nm), direct and non-destructive and has been used extensively to characterize the surface of hydroprocessing catalysts. The outermost region of the sample can be probed qualitatively and semi quantitatively for all elements except hydrogen. Usually it is possible to confirm the chemical composition (oxidation state) of a surface sited element. On the other hand Ultra-violet photoelectron spectroscopy (UPS) enables to obtain information concerning the metallic properties of the catalyst, if any, present in the outermost surface layer (less than 0.4 nm). Moreover, coupling of the XPS and UPS spectroscopy studies, in situ, on the same catalyst before and following different treatments by hydrogen reduction will enable to identify the chemical species responsible for the catalytic activity.

In the case of cobalt-molybdenum deposited on alumina hydrotreating catalysts, surface chemical composition and identification of the compounds present on the fresh and reacted catalyst (i.e., MoO3 → MoS2, CoO → Co9S8, etc) will be studied. The nature of interaction between the Mo and Co with the alumina surface will be explored.

Morphology and catalysts texture before and after catalytic studies will be studied by different electron microscopy (EM) techniques such as scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM). It is well known that modification of the chemical composition of the starting material(s) that lead to the formation of the catalytic active phase following the exposure of the surface to different treatments such as reduction by hydrogen at different temperatures and sulfidation will certainly affect the morphology of the catalyst surface. Dispersion of the catalyst active phase plays an important part in determining its activity.

In this workshop, an introduction to the XPS-UPS techniques will be presented. Characterization of Co-Mo / Al2O3 HDS as well as Platinum on chlorinated alumina isomerization catalyst by using the above mentioned techniques will be presented.

The scanning microscopy can be operated in many ways. These different techniques provide a variety of capabilities for imaging different types of samples and generating a wide range of information. Imaging modes (sometimes referred to as “scan modes”) are the methods that are used to move the sensor over the sample surface and sense the surface in order to create an image. There is a continuum of possible imaging modes, due to different interactions between the sensor and the sample, as well as the detection scheme used. So the proper choice of the appropriate mode to the specific application is of prime importance