Efficient Ring-opening Reaction of Tetralin over Nanosized ZSM-5 Zeolite: Effect of SiO2/Al2O3 Ratio and Reaction Condition

The naphtheno-aromatics from the hydrogenation of light cycle oil and coke gas oil are important feedstocks for producing high octane number gasoline via a cracking reaction. However, besides the ring-opening reaction to desired products, the condensation of naphtheno-aromatics to polycyclic aromatics is inevitable. In this work, the typical micrometer-sized ZSM-5 zeolite and various nanosized ZSM-5 zeolites with different SiO2/Al2O3 ratios have been prepared and evaluated for the catalytic cracking of tetralin as model molecule for naphtheno-aromatics. Compared with the micrometer-sized ZSM-5 zeolite, the nanosized ZSM-5 zeolite with higher porosity and shorter diffusion channel exhibited both an enhanced reactivity and an improved selectivity to the ring-opening reaction. Among the various nanosized ZSM-5 zeolites with different SiO2/Al2O3 ratios, the zeolite with SiO2/Al2O3 ratio of 200 showed the highest selectivity to ring-opening products, which probably resulted from the low hydrogen transfer activity for the lesser amount of acid sites and the efficient diffusion of product molecules from the micropores. Furthermore, the reaction conditions for the ring-opening reaction of tetralin have been tested. The results indicate that the optimal reaction conditions are a temperature of 550 degrees C and WHSV of 2 h(-1), at which 85.41% conversion of tetralin and 80.38% selectivity to ring-opening products have been achieved.