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.

Abstract