Reactivity of Surface Species in Heterogeneous Catalysts Probed by In Situ X-ray Absorption Techniques

Starting from the late seventies, the progressively increased availability of synchrotron light sources allowed the execution of experiments requiring a high X-ray flux in a continuous interval. In particular, XAFS techniques are extremely powerful to shed light on the structure and reactivity of surface species in heterogeneous catalysts, in many steps of the catalyst life and also during the catalytic act. A quantitative EXAFS and XANES analysis, possible only in these conditions, was fundamental to reveal the local structure of carbonyl species. IR spectroscopy gave independent information on the fraction of chromium sites active in ethylene polymerization on the Phillips catalysts as a function of polymerization conditions, in well agreement with the values obtained by XANES. The second is the experimental hutch, where the experiment is performed. The third is the control room, where where scientists monitor the experiment and perform a first data analysis.