XANES analysis of catalytic systems under reaction conditions

ABSTRACT The article gives an overview of the XANES technique contribution to the analysis of multicomponent catalysts. The theoretical basis of the technique, the interpretation of the energy position and intensity of XANES features, and the numerical methods developed to interpret XANES data on catalytic systems are described and discussed in the first part. In the second part, the most recent XANES studies of catalytic samples are reviewed, giving particular attention to the solid state chemistry information extracted under real, in-situ conditions. This concerns structural and redox properties of the systems during preparation stages, activation treatments like reduction, oxychlorination, or sulfidation, and reaction conditions. Additional effort was made to describe the use of XANES to gain insight on electronic properties of catalysts. The influence of all these redox, geometrical and electronic properties on catalytic behavior, particularly as a function of particle size and active metal-support interaction, has also been examined on the light of XANES data. Keywords: X-ray absorption spectroscopyXANESMethods of XANES data analysisIn-situ study of catalytic systemsSolid state chemistry of catalystsParticle size effectActive metal—support effect Acknowledgments Quantum-chemical calculations for the TiO6 8− were done with the hondo–cipsi chain of programs (M. Dupuis, J. Rys, H. F. King, hondo-76, Program 338, qcpe). The authors are also grateful to Mrs. A. Iglesias-Juez, A. B. Hungría, Drs. J.A. Anderson, A. Martinez-Arias, J. C. Conesa, P. Ferreira-Aparicio, A. Guerrero-Ruiz, I. Rodríguez-Ramos and Profs. J. Soria and G. L. Haller. Thanks are given to Profs. S. Overbury and F. Farges for kindly supplying figures used in this review.