The Search for a Cracking Catalyst: Aluminum- and Surfactant-Modified ZSM-5 Zeolites

In the present study, modified ZSM-5 catalysts were synthesized, characterized, and tested for their cracking activity and selectivity toward desired cracked products. The ZSM-5 zeolite was modified by aluminum impregnation to increase the acidic strength as well as by non-ionic Pluronic F127 surfactant to induce the mesoporosity in the zeolitic structure. The catalysts were characterized and their catalytic performance was evaluated in a high-pressure Parr autoclave reactor through n-hexadecane cracking. The experiments were performed at a fixed residence time of 60 min, a feed-to-catalyst ratio of 20:1 by weight, different cracking temperatures between 325°C and 400°C, and an initial cold pressure of 1 bar. The reaction products (both gas and liquid) were quantitatively analyzed by a GC-FID system. The results of the cracking experiments showed that at 350°C, the 2.5 wt% aluminum-impregnated ZSM-5 catalyst offered significantly high conversion (79.1%) and selectivity toward gasoline-ranged hydrocarbons compared to the other aluminum-modified catalysts. The modification with F127 considerably reduced the crystallinity of ZSM-5 and resulted in relatively higher conversions but lower liquid yields.

Abdullah Ramzan and Muhammad R Usman