Hierarchically porous niobium oxides

Recently, the self-formation phenomenon used for the formation of hierarchically porous metal oxides was ako applied to the formation of hierarchically micro-macroporous niobium oxides [12,141,144]. These synthesized niobium oxide particles with amorphous nature are mainly 100 in size with a regular array of parallel macropores (Figure 32.13a). The macropores with the pore size in the range of 0.3-10 pm extend through almost the whole particle. The macropore walls are constructed from accessible micropores. The hierarchically porous niobium oxides can be obtained via a self-formation phenomenon under different pH values (2, 7, and 12) [141,144]. 

Rooke, J.C., Barakat, T., Finol, M.F., Billemont, P., De Weireld, G., Li, Y., Cousin, R., Giraudon, J.M., Siffert, S., Lamonier, J.F., and Su, B.L. (2013) Influence of hierarchically porous niobium doped Ti02 supports in the total catalytic oxidation of model VOCs over noble metal nanoparticles. Appl. Catal. B Environ., 142-143, 149-160. 

Nb-based catalysts are among the investigated systems in total removal of -butanol due to the capacity of niobium to adopt variable oxidation states. Thus, Nb-doped hierarchically micro(meso) macroporous Ti02 (anatase phase) (Figure 17.10) synthesized via a self-formation procedure showed close performances with catalysts in which the same materials served as supports for noble metals [46]. The efficiency of these catalytic systems in the total oxidation of butan-l-ol was enhanced by the improved diffusion through the intrinsic macro-porous network. An effect of the niobium content was evidenced as welL... 

Figure 18.8 Scanning electron microscopy images for the vanadium (a) and niobium (b) hierarchically nanostructured porous oxides. (Reprinted with permission from Ref. [40]. Copyright 2015, Elsevier.)...

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