Hydrogen Spillover and Surface Diffusion : spillover from a point source

Hydrogen exchange and spillover on a palladium/silica catalyst

“…The calculated total amount of palladium metal on this catalyst was 15.04 mmol/kg of catalyst. The amount adsorbed exceeds this value by a factor of approximately 2-5 (depending on whether the adsorbing species is H2 or D2) already at an experimental temperature below 373 K. The H/Pd value reaches a limit of about 33 at the highest temperature, and this is well above previously published data (Curtis Conner et al, 1983). The dispersion of palladium, mentioned earlier, was 42.9%, and as the ratio of H/Pd in the a-phase of the palladium-hydrogen system never exceeds 0.01 (Scholten and Knovalinka, 1966) for low-temperature and high partial pressure hydrogen isotopes, the amount of hydrogen isotopes absorbed can be disregarded from the total amount adsorbed on the dispersed metal.…”

“…The hydrogen in the hydroxyl groups will then be exchanged with the adsorbed hydrogen atom and finally desorb, through an adsorbed species on the metal surface. A description of the different energy levels of the different states of hydrogen atoms on the surface is given by Curtis Conner et al (1983). An estimate of the total amount of OH groups on the Si02 part of the catalyst can be made, as 830 mmol/kg of catalyst, assuming a concentration of 5 OH groups/nm2 (Anderson, 1975).…”

Dynamic oxygen mobility and a new insight into the role of Zr atoms in three-way catalysts of Pt/CeO2–ZrO2

“…A similar study over Rh/Al 2 O 3 was reported by Cavanagh and Yates, who followed the H/D exchange by IR spectroscopy [6]. Quantitative measurements of surface diffusivities were carried out by Conner et al [7,8] by means of a spatially resolved FTIR apparatus. In 1987, Duprez and coworkers developed a method of isotopic exchange for the study of surface mobility, and systematically studied the supported metal catalysts and some mixed oxides [9][10][11][12][13].…”

Characterization of the dynamic oxygen migration over Pt/CeO2-ZrO2 catalysts by 18O/16O isotopic exchange reaction

“…Hall and Lutinski [6] and Carter et al [7] had studied the exchange of D 2 with the OH groups of Pt/Al 2 O 3 . A similar study over Rh/Al 2 O 3 was reported by Cavanagh and Yates, who followed the H/D exchange by IR spectroscopy [8], Quantitative measurements of surface diffusivities were carried out by Conner and co-workers [9,10] by means of a spatially-resolved FTIR apparatus. In 1987, Duprez and co-workers developed a method of isotopic exchange for the study of surface mobility [16][17][18][19], and systematically studied the supported metal catalysts and some mixed oxides [11][12][13][14][15][16][17][18].…”