Effect of Secondary Additives on the Properties of Vanadium-Aluminum Mixed Oxide Catalysts Used in the Oxidation of Propane

We investigated how secondary additives for tableting vanadium-aluminum
mixed-oxides affect the mechanical resistance, surface chemistry, and catalytic performance in
propane oxidation of tablets based on this material. The secondary additives were magnesium
oxide, silica, boron nitride, sepiolite, and zinc oxide while graphite was used as the primary
shaping agent. Our results showed that the changes in mechanical strength and porosity were
directly related to the softness and ductility of the secondary additive. Overall, we learned that
when manufacturing catalyst tablets, there is a compromise between mechanical strength and
loss in mesoporosity and surface area. On the other hand, the components of the formulated
tablets did not show signs of establishing a chemical interaction with the vanadium-aluminum
mixed oxide. Therefore, the effects of the additives that we found on the catalytic performance
were ascribed to the fact that the selected secondary additives may act as co-catalysts during
propane oxidation. In this sense, boron nitride and sepiolite were best for promoting both the
reactivity of the catalytic formulations while showing a better productivity of propene. The data
was interpreted suggesting that the promotion effect may be due to the combination of a redox
mechanism over the vanadium-aluminum mixed oxide phase and to a surface radical mechanism
occurring over the active moieties of these secondary additives.