FTIR evidences of the reactivity of spilt-over stored hydrogen: Transformation of Lewis acid sites into Bronsted sites on Pt/ZrO_2 catalyst

摘要

The reactivity of hydrogen species resulted from backspllover of H atoms stored in the support when Pt/ZrO_2 catalyst is reduced was shown even in the absence of H_2 in the gas phase. These species were able to create acidic hydroxyls and move pyridine chemisorbed on Lewis acid sites to the new Bronsted sites just formed, when the sample was heated in a closed system. Also piperidine chemisorbed on Lewis acid sites was dehydrogenated to pyridine when the sample was heated in a closed system, and the IR spectrum showed bands which were assigned to pyridine chemisorbed on Lewis and Bronsted sites. The reactivity of hydrogen spillover species was also observed by CO chemisorption experiments using FTIR and TPD techniques.