Developing a supported metal oxide catalyst for direct dehydrogenation of propane to propene

Abstract

Propene is an important building block in the petrochemical industry and its demand is rapidly increasing. However, the production through conventional processes is limited, and there is a dire need to develop a suitable catalyst for the direct dehydrogenation of propane. Multiple set of catalysts are synthesized via incipient wetness impregnation method and characterized by various techniques. These catalysts are also tested for the direct dehydrogenation reaction, to examine the effect of active metal oxide species, support material, metal oxide loading and potassium (K) loading. Subsequently, the reaction temperature and contact time are optimized for the reaction. A near-monolayer loading chromium oxide supported on ZrO₂ is the most active. At this loading incipient amounts of Cr₂O₃ crystallites are detected, which became larger at higher coverages. The monolayer coverage appears to be between 5.2 and 6.6 $\mathrm{ato}{m}_{\mathrm{Cr}}/n{m}^2$. Furthermore, at this coverage the amount of reducible Cr⁺⁶ species was maximum. The activity of this near-monolayer catalyst is further improved by co-impregnating K. A Cr to K molar ratio of 1:0.05 is found to increase the amount of reducible Cr⁺⁶ and the catalyst activity and selectivity. Increasing the K amount further leads to a decrease in activity. Activity is increased by increasing the reaction temperature till 550 ℃; however, above 550 ℃ the catalyst deactivates due to coke formation. Further improvement in activity is achieved by increasing the contact time and a conversion of ∼30 % and yield of ∼27 % is achieved for the K-promoted supported chromia catalyst at 550 °C and a contact time of 37.33 $g_{\mathrm{cat}}.h/\mathrm{mol}$.