Effect of matrix on aromatics production by cracking and dehydrocyclization of n-pentane using Ga ion-exchanged ZSM-5-alumina composite catalysts

The composite catalysts were prepared from mesoporous alumina as a matrix and Ga-exchanged ZSM-5 as a major catalytic component by the conventional kneading method. The effects of the matrix on the activity and selectivity of aromatics in cracking and dehydrocyclization of n-pentane were investigated. 65-85 wt% of GaZSM-5 was mixed with 0-20 wt% of Al2O3 and 15 wt% of alumina-sol binder. Cracking of n-pentane and successive dehydrocyclization of formed olefins to produce aromatic compounds were performed using a fixed bed reactor under the conditions, H2 atmosphere and temperature range 450-550 degrees C. The conversion of n pentane and the selectivity for aromatics increased with increasing temperature. A catalyst Ga(15)ZSM/10A, where the Ga-exchange ratio was 15%, exhibited the highest conversion among the catalysts with same Ga(15), suggesting that there would be the optimal values of Ga and alumina contents to obtain the high conversion. Further, Ga(15)ZSM/10A exhibited the highest selectivity for aromatics, suggesting that the presence of matrix alumina would appropriately inhibit the cracking to C1 and that the amount of GaZSM-5 would be enough large to increase aromatics to the maximum. Reaction routes and product distributions could be explained by the initial cracking of n-pentane, the small amount of C4 fraction cracking and the successive aromatization through dehydrocyclization of formed olefins.

Automated summary

Composite catalysts were prepared using mesoporous alumina as a matrix and Ga-exchanged ZSM-5 as a major catalytic component, with investigations into their effects on the activity and selectivity of aromatics from cracking and dehydrocyclization of n-pentane. Experimental results using a fixed bed reactor showed that increasing temperature led to higher conversion of n-pentane and selectivity for aromatics.