(736e) Does Surface Roughness Matter: A Case Study With VOx / SBA-15 in the Partial Oxidation of Methanol and Propane

SBA-15 is a template-synthesized mesoporous silicate that has found extensive use as a model support for studies of supported catalysis.[1, 2] Thorough structural analyses clearly describe the dual micropore-mesopore structure with a broad distribution of micropore sizes.[3]  In contrast to other oxides such as titania or ceria, silicas such as SBA-15 have long been considered a relatively inert support. However, we find the effect of microporosity or surface roughness in SBA-15 has an underappreciated effect on catalyst performance. Specifically, samples of VO_x-SBA-15 where the support surface roughness was systematically varied were characterized using UV-vis and Raman spectroscopy, then tested in the catalytic partial oxidation of methanol to formaldehyde, and propane to propene. Results show that supports with smoother surfaces permit the development of more polymeric vanadia species at the same surface density loading. Such smoother-surface catalysts result in a lower selectivity of methanol to formaldehyde, yet conversely show a higher selectivity of propane to propene. This result is significant with respect to our understanding the role of vanadium in in partial oxidation catalysts, and illustrates the importance of considering differences in support surface morphology in analyzing catalytic behavior.

References

[1]     V. Dufaud, M. E. Davis,  J. Am. Chem. Soc.  125 (2003) 9403-9413.

[2]     R. K. Zeidan, S. J. Hwang, M. E. Davis,  Angew. Chem.-Int. Edit.  45 (2006) 6332-6335.

[3]        M. Kruk, M. Jaroniec, R. Ryoo, J. M. Kim,  Chem. Mat.  11 (1999) 2568-2572.