Characterization and cracking activity of MoO3-SiO3catalysis

Pure silica and a series of MoO₃/SiO₂ catalysts with different MoO₃ loadings ( 2-16wt%) were prepared using the standard incipient wetness technique. The catalysts were characterized using XRD and FTIR techniques. The textural properties were determined from nitrogen adsorption at 77K. the acidic properties of these catalysts were measured by the amine titration method. The cracking of cumene was investigated over these catalysts. XRD data revealed the amorphous nature of the catalyst up to 6 wt%MoO₃ loading and the formation of crystalline MoO₃ phase on amorphous silica support were detected only for the catalyst with higherMoO₃ loading. Loading SiO₂ with higherMoO₃ (9wt %) leads to a significant change in texture, surface acidity and catalytic activity of the prepared catalysts. Catalysts with higher MoO₃ loading show much higher acid strength compared to the catalysts with lowerMoO₃ loading (6 wt %). The cracking activity has been related to the strength of the acid sites presented on the catalyst surface. Cracking of cumene over the investigated catalyst necessitates the presence of strong acid sites. These sites are evidently Bronsted acid sites on which the cracking process probably proceeds via a carbonium ion mechanism