Ti-Peroxo Species in the TS-1/H2O2/H2O System

• DOI: 10.1021/jp036166e
• Publication Date: 2004-03-11T06:18:48Z
• Authors: Francesca Bonino; Alessandro Damin; Gabriele Ricchiardi; Marco Ricci; Guido Spanò; Rino D'Aloisio; Adriano Zecchina; Carlo Lamberti; Carmelo Prestipino; Silvia Bordiga
• Keywords: Oxidizing agent

This work is devoted to the study of active species present on TS-1-H2O2/H2O catalytic system and elucidation mechanisms formation interconversion these species. In particular new experimental data computational evidence are reported concerning (i) acidic character hydroperoxo species, (ii) role water in hydroperoxo−peroxo interconversion, (iii) as co-reactant favoring H2O2 adsorption at Ti sites. It demonstrated that gentle drying leads transformation yellow peroxo groups into noncolored still located centers. The process reversible colored can be partially restored again by successive rehydration. As have different oxidizing ability, results indicate presence molecules hydrophilic sites correlate with activity. it well-known, unstable their concentration declines aging. However, UV−vis spectroscopic demonstrate small fractions (characterized a cream color) persist sample even after prolonged On this basis EXAFS results, comprehensive scheme mutual conversion oxidized concluded. Spectroscopic supported acidity measurements titration oxygen content, show following: O−O responsible color catalyst, side-on complex, probably generated rupture one Ti−O−Si bridge, Ti(O2H) H−O−Si groups; stability complex low absence an excess H2O; strong enhancement TS-1/H2O2/H2O respect TS-1/H2O has been observed, demonstrating synergic between Ti(IV) centers hydrogen peroxide; (iv) fraction negligible ability does not play any catalysis.