Comparative study of Pt/zeolites for n-hexadecane hydroisomerization: EU-1, ZSM-48, ZSM-23, ZSM-22, and ZSM-12

The hydroisomerization of n-hexadecane was investigated using bifunctional platinum catalysts supported on EU-1, ZSM-48, ZSM-23, ZSM-22, and ZSM-12 zeolites. These one-dimensional microporous zeolites were synthesized at 160 ℃ with an Si/Al molar ratio of 60, and 0.5 wt% Pt was loaded onto them using the impregnation method. The findings indicate that Brønsted acidity predominantly influences the conversion to n-hexadecane over 10 membered ring zeolites. Additionally, ZSM-12, characterized by a 12-ring channel, exhibits preferential activity in this regard. The apparent activation energy for the reactions increased from 81 kJ/mol (Pt/ZSM-23) to 134 kJ/mol (Pt/ZSM-48) across all tested catalysts. Pt/ZSM-22 demonstrated high selectivity towards mono-branched isomers, whereas Pt/ZSM-12 favored the formation of multi-branched isomers. The isomer selectivity trend was Pt/ZSM-22 > Pt/ZSM-12 > Pt/EU-1 > Pt/ZSM-48 > Pt/ZSM-23. Moreover, TG analysis of spent catalysts unveiled that coke formation on these zeolites was chiefly influenced by zeolite channel structure and Brønsted acid content. The average coke selectivity followed this order: Pt/EU-1 > Pt/ZSM-12 > Pt/ZSM-48 > Pt/ZSM-22 > Pt/ZSM-23.