Genesis of the active-component precursor in the synthesis of Pt/Al2O3 catalysts: I. Transformation of the [PtCl6](2-) complex in the interaction between chloroplatinic acid and the gamma-Al2O3 surface

摘要

Gradient elution experiments have revealed the difference between platinum complexes in terms of the strength of their interaction with the alumina surface. A considerable part (30-40%) of the supported platinum is nondesorbable via competitive ion exchange reactions or upon changes in the charge state of the support surface. The surface platinum complexes can be divided into ion-exchangeable and coordinatively fixed species according to the nature of their bonding with aluminum oxide. Combining desorption and spectroscopic methods (EXAFS and diffuse reflectance spectroscopy) has made it possible to characterize the surface complexes. The strongest metal-support interaction takes place in the fixation of hydrolyzed platinum species.