Supported Catalysts: Does Surface Roughness Matter? A Case Study with VOx-SBA-15

2013 Spring Symposium

Michael A. Smith
Depart­ment of Chem­i­cal Engi­neer­ing
Vil­lano­va Uni­ver­si­ty
Vil­lano­va, PA 19085

Abstract — 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] Sil­i­cas such as SBA-15 have long been con­sid­ered a rel­a­tive­ly inert sup­port, quite in con­trast to oth­er oxides such as tita­nia or ceria. We find the effect of sur­face rough­ness of SBA-15 has an under­ap­pre­ci­at­ed effect on cat­a­lyst per­for­mance. Specif­i­cal­ly, sam­ples of VOx-SBA-15 where the sup­port sur­face rough­ness was sys­tem­at­i­cal­ly var­ied were chara­ter­ized 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 for­made­hyde, 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.
[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.

Michael A. Smith

Michael A. Smith

Biog­ra­phy — Pro­fes­sor Michael A. Smith is cur­rent­ly an Assis­tant Pro­fes­sor in the Depart­ment of Chem­i­cal Engi­neer­ing at Vil­lano­va Uni­ver­si­ty. He received his BS in Chem­i­cal Engi­neer­ing from Lafayette Col­lege in 1980, then worked in a vari­ety of assign­ments with the DuPont Com­pa­ny for 17 years. Dr. Smith returned to school to obtain a Mas­ters at Vil­lano­va Uni­ver­si­ty, and obtained his PhD in Chem­i­cal Engi­neer­ing from the Uni­ver­si­ty of Delaware in 2004 work­ing with Prof Raul Lobo. Since he has work as a research sci­en­tist for an SBIR start­up, and has been at Vil­lano­va since 2006, first as a Vis­it­ing Assis­tant Pro­fes­sor, then in a tenure track posi­tion since 2008. Dr Smith’s research inter­ests include the syn­the­sis and char­ac­ter­i­za­tion of nanos­truc­tured mate­ri­als made using col­loidal self-assem­bly and sol-gel tech­niques, and het­ero­ge­neous catal­y­sis with an empha­sis on catal­y­sis by met­al oxides.