New frontiers in X-ray spectroscopy in heterogeneous catalysis: Using Fe/ZSM-5 as test-system

Abstract

We have applied a number of novel X-ray spectroscopic tools to Fe/ZSM-5 systems. Fe/ZSM-5 can be considered as an ideal test-system for the characterization techniques in heterogeneous catalysis. The existence of a large range of sites and structures creates a good testing ground to determine which experimental tools are able to resolve such complex system. In situ soft X-ray absorption provides important information on the valence and electronic structure of iron during treatments, with a time scale down to 30 s. K beta-detected XANES yields unprecedented resolution for pre-edge structures and using hard X-rays can be used under any condition and treatment, including high-pressures. It can be expected that both in situ soft X-ray absorption and K beta-detected XANES become 'standard' tools for catalysis research, similar to traditional XANES and EXAFS today. The X-MCD is also used in this paper but it will probably remain a rather specialized technique in the field of heterogeneous catalysis. Further new developments for catalysis characterization are for all to be expected from X-ray spectro-microscopy, where one will have the possibility to perform the in situ soft X-ray absorption and K beta-detected XANES experiments with nanometer size spatial resolution. (c) 2005 Elsevier B.V. All rights reserved.