Pt/Al-SBA-15 catalysts for hydrocracking of C₂₁-C₃₄ n-paraffin mixture into gasoline and diesel fractions

In this study, a Pt-loaded mesoporous aluminosilicate (Pt/Al-SBA-15) was optimized as a catalyst for the hydrocracking of Fischer-Tropsch waxes, for which n-paraffin wax in the C_21-34 range was used as a model reactant. Pt/Al-SBA-15 was more active than a Pt-loaded microporous zeolite (Pt/β-zeolite) in producing gasoline-range products from n-paraffin wax. Hydrocracking over Pt/Al-SBA-15 occurs via a bifunctional mechanism, the activity of which was correlated closely with the density (concentration) of strong acid sites and total exposed Pt surface area. The reaction was more noticeably promoted at the Brønsted acid sites, rather than at the Lewis acid sites, of Al-SBA-15. The highest gasoline yield (72.8%) was achieved with the catalyst comprised of 0.5 wt.% Pt and Al-SBA-15 with Si/Al molar ratio of 14.5.