By using the rectangular pulse technique coupled with the reaction NO + NH3 + V=O → N2 + H2O + V-OH, we have determined the number of surface V=O species or the specific area of the (010) face of V2O6 for V2O5/TiO2 catalysts with various contents of V2O5. It has been found that the V=O species or the (010) face of V2O6 is selectively exposed to the surface of V2O5/TiO2 catalysts. As the content of V2O6 in the catalyst increases to 5 mol %, the surface of TiO2 support is gradually covered by the (010) face of V2O5. When the content of V2O5 is 10 mol %, the maximum fraction of the (010) face of V2O5 on the catalyst surface (90%) is attained, indicating that almost all of the surface of the V2O5/TiO2 catalyst is covered by the (010) face of V2O5. When the content of V2O5 increases further, the fraction of the (010) face decreases to reach the value of the unsupported V2O5 (50%) where various crystal faces of V2O5 are exposed in addition to the (010) face. It has been pointed out that these results agree with previous studies of V2O5/TiO2 catalysts and prove the validity of these studies quatitatively. In addition to the number of surface V=O species, the number of V2O5 lamellae on a TiO2 support has been determined by the comparison of experimental concentration profiles of N2 with simulated ones. The number of layers thus determined has agreed with the number of layers calculated from the content of V2O5 and the specific area of the (010) face of V2O5. On the basis of the above-mentioned data, the applicability of the proposed method to supported V2O6 and V2O5-containing multicomponent catalysts has been concluded.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry