EPR studies on the formation of atomic oxygen(1-) (O-) ions on reduced silica-supported molybdenum catalysts prepared by the grafting method

EPR Investigation of the Activation of N2O on Mo/SiO2Catalysts via Electron Transfer: From N2O as a Ligand to Adsorbed O-Ion

“…Moreover, this result indicates that each Mo 4c 5+ site can accept only one N 2 O molecule. Thus, in agreement with earlier results, , it appears that the penta- and hexacoordinated Mo 5+ complexes play only a spectator role during N 2 O adsorption at room temperature. The same behavior was previously observed in the case of CO and Et 3 P adsorption onto Mo/SiO 2 catalysts, contrasting with the ability of highly polar molecules like H 2 O or CH 3 OH to fill the coordination vacancies also of the pentacoordinated molybdenum.…”

“…Though the results of NO adsorption onto Cu-ZSM5 catalysts provide further precedence for this hypothesis, 26 it was reported that increase of the pressure of nitrous oxide adsorption up to 300 Torr does not produce further changes in the EPR spectrum. 20 It is likely that this phenomenon is due to the known poor ligand property of nitrous oxide.…”

“…N 2 O (Air Liquide) was purified by freeze−pump−thaw cycles prior to adsorption, which was carried out at room temperature under a pressure of 30−40 Torr. Referring to previous works, , the O - ions were (except in the variable-temperature study) generated by heating the sample with preadsorbed N 2 O at 373 K for 15−20 min, followed by evacuation to 10 -5 Torr.…”

Characterisation and reactivity of oxygen species at the surface of metal oxides

“…It provides the pathway for surface diffusion of atomic ROS, which is crucial for the Langmuir-Hinshelwood-type reactivity [6,8,21] The interfacial O2 2-intermediates may also be produced via O2 (or N2O) interaction with the basic O 2surf surface sites acting as anionic redox centers (½ O2 + O 2surf → O2 2-) [22]. The Ospecies, in turn, are often generated upon N2O adsorption via dissociative electron transfer [17,23,24] N2O + e → Oads + N2 (2) or as a hole OO -(h + VB) intrafacial centers, produced via photochemical charge separation (0 ® e -CB + h + VB) [25][26][27].…”

Acoplamento oxidativo de metano sobre catalizadores de Li/MgO-SiO2

“…O produto formado a partir do metano, depende então das taxas relativas das etapas 12 e 17, que pode ser relacionado à influência das condições experimentais sobre a formação de íons o• do NzO adsorvido sobre Mo03-Si02 e o papel desses íons nas reações de transferência de carga superficiais (Che, M., Dyrek, K., 1985). Metano!…”