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

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