Role of acidity in catalytic cracking of n-decane over supported Pt-based catalysts

Abstract

Different acidic-basic oxides, Al2O3, SiO2, MgO, MgO-SiO2, MgO-Al2O3 and SiO2-Al2O3, were employed as supports of Pt-based catalysts for n-decane cracking, aiming to investigate the effect of acidity on cracking activity and coking behaviors. The as-prepared catalysts were characterized by the techniques of N2 absorption-desorption, X-ray diffraction (XRD), CO chemisorption, temperature programmed desorption of ammonia (NH3-TPD) and Fourier transform infrared spectroscopy (FTIR) of adsorbed pyridine. The results showed that acidic support catalysts are more suitable for catalytic cracking reaction of n-decane than alkaline support catalyst. Particularly, Pt/SiO2-Al2O3 catalyst exhibited the optimal catalytic activity, leading to heat sink of 3.920 MJ/kg and n-decane conversion of 85.5% at 750 °C. Meanwhile, excellent cracking activity over Pt/SiO2-Al2O3 catalyst is due to large ratio of strong to total acid sites and large amount of Lewis acid sites. Additionally, stability and regeneration experiments of Pt/SiO2-Al2O3 showed that coverage of active sites due to coke deposition is main factor to catalyst deactivation, and carburization of Pt metals will lead to the reduction of catalytic activity.