The Effect of Thermal Aging and Addition of CeOx, NbOx, and SbOx on the Structure of Dispersed VOx in Low-Loaded Anatase-Supported Vanadia Catalysts

Journal article, 2026

In situ vibrational spectroscopy (Raman, FTIR) is used at temperatures of 120-430 degrees C under oxidative dehydration conditions to study the effect of CeO x , NbO x , and SbO x modifiers, as well as the effect of thermal aging, on the structural and configurational properties of titania(anatase)-supported vanadia catalysts. The study pertains to catalysts with low vanadium coverage (i.e., similar to 0.5 V nm-2) and an M/V molar ratio (M = Ce, Nb, Sb) equal to one. The dispersed (VO x )n phase consists of three species with distinct configurations: a majority Species-I with an O=V(-O-Ti)3 configuration (V=O terminal mode at 1024-1027 cm-1) followed by Species-II with an O=V(-O-Ti)4 configuration (V=O terminal mode at 1014-1016 cm-1) and a minority Species-III with an (O=V)2(-O-Ti) x configuration (symmetric stretching mode at similar to 1000 cm-1). Lowering of the temperature in the 430-120 degrees C range results in reversible temperature-dependent structural transformations. First, in the 430-250 degrees C range, a Species-II to Species-I transformation takes place, followed by a Species-I to Species-III transformation at lower temperatures. Modifying the VO x /TiO2(anatase) catalysts with CeO x , NbO x , or SbO x results in the increased presence of Species-I at the expense of Species-II. Thermal aging of the studied catalysts at 580 degrees C for 100 h gives rise to structural transformation of the anatase carrier, resulting in an increased presence of (101) facets and severe lowering of the specific surface area, thereby causing an increase in Species-I at the expense of Species-II and in the formation of V-O-V and/or V-O-M linkages. The results are deemed important for gaining insight into the structure and the behavior of anatase-supported vanadia catalysts.