Catalytic cracking of n-octane over zeolites with different pore structures and acidities

Abstract

Catalytic cracking of n-octane has been studied over FAU, FER, MWW, MFI, BEA and MOR zeolites in order to investigate the effects of pore structure and acidity on their catalytic properties. The conversion of n-octane was largely dependent on the number of strong acid sites, while their pore structure determined the rate of catalyst deactivation due to carbon deposit. Continuous and high catalytic activity, therefore, was obtained on the MFI zeolite with sinusoidal pores and small Si/Al molar ratio, because its pores suppress the formation of large intermediate and its large number of strong acid sites accelerates the cracking of n-octane. urated hydrocarbons, they are also active for the catalytic cracking. Strong acidity, therefore, is required for the catalytic cracking, but strong acid sites simultaneously initiate a rapid deactivation of cat- alysts due to carbon deposit. As a result, catalysts suitable for the catalytic cracking of paraffin should have a large number of strong acid sites to initiate the cracking reaction by producing reactive in- termediates and specific pore structures to suppress the formation of large hydrocarbons which are converted to high boiling carbon- eous materials. The high hydrothermal stability of the catalysts is also indispensable because the catalytic cracking is operated at high temperatures in the presence of steam.