Platinum catalysts supported on ZSM5 zeolites with a hierarchical pore structure: characterization and performance in n-hexadecane hydroconversion

HZSM5 zeolites with a hierarchical pore structure were prepared from a microporous one using the top-down methodology by treatment with a sodium hydroxide solution in optimal conditions of time, alkali concentration and temperature. These materials were used as supports for platinum to produce bifunctional hydroconversion catalysts. The activity in n-hexadecane hydroconversion was one order of magnitude larger on Pt supported on the mesoporous than on the untreated zeolite and one order of magnitude larger than that of the supports. All Pt catalysts and supports were more selective to hydrocracking than to hydroisomerization, but the initial selectivity for hydroisomerization of the Pt catalysts supported on the mesoporous supports was considerably smaller than that of all other materials, including the supports. This was attributed to a smaller mass transfer limitation with the Pt catalysts supported on the mesoporous zeolites. All supports and catalysts were extensively characterized by techniques such as X-ray diffraction, hydrogen chemisorption, TPD of ammonia, IR spectroscopy of adsorbed pyridine, MAS Si-29 and Al-27 solid state NMR and transmission electron microscopy. [GRAPHICS] .

Automated summary

HZSM5 zeolites with a hierarchical pore structure were prepared using a top-down methodology by treating a microporous one with a sodium hydroxide solution. These materials were used as supports for platinum to produce bifunctional hydroconversion catalysts, resulting in significantly improved activity and selectivity in n-hexadecane hydroconversion compared to untreated zeolites. Extensive characterization was carried out using various techniques to study the properties of the supports and catalysts.