Analysis of Catalysts
Taking Control over Chemical Reactions

Catalysis is the effect that certain substances, so-called catalysts, are able to specifically influence the kinetics of a chemical reaction. Catalysts reduce the activation energy of the respective chemical reaction without being consumed in it. Often heterogeneous catalysts are used where the catalyst consists of a solid material. This material itself can be active in the reaction, as is the case with e.g. zeolites, or the catalyst can have an active phase dispersed on a support. With the latter method small amounts of expensive noble metals are needed to obtain a large surface area of these metals. Examples of these supported catalysts are Pd/C hydrogenation catalysts or automotive catalysts containing Pt and Rh on Ceria.

Heterogeneous catalytic reactions take place at the outermost atomic layer of a catalyst. It is therefore not surprising that quantitative, surface analytical methods such as Low Energy Ion Scattering Spectroscopy (LEIS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) or photoelectron spectroscopy (XPS, ESCA) are used in the development of catalysts and in the search for the causes of failure of catalysts. Ideally, catalysts emerge unchanged from a chemical reaction. However, catalysts can be deactivated by a variety of mechanisms and they can be poisoned by specific contamination. In that case, the cause should be clarified. The analysis of catalysts has been part of our daily work in the Tascon laboratory for over 20 years. The following example shows the analysis of a catalyst in our laboratory.