Boosting hydroisomerization of n-hexadecane by designing core-shell bifunctional catalysts with partially blocked micropores

Abstract

Hydroisomerization of long-chain n-alkanes is an indispensable route for upgrading fossil fuels and lubricant oils to meet the state of art regulations. Precisely regulate the distribution of acidic and metal active sites to suppress unwanted cracking reaction is hitherto a difficult task. In this work, we develop a simple coating-carbonation strategy for constructing novel core-shell bifunctional catalysts, comprising ZSM-22 zeolite core with the partially blocked channels and Pt nanoparticles loaded on the mesoporous SiO₂ shell. The unique treatment not only adjusted the distribution of acid sites located within the micropore channels and external surface, but also alter the locations and dispersion of Pt nanoparticles. Owing to the short diffusion lengths, nanoscale distance between acid sites and Pt species, and high metal dispersions, the core-shell bifunctional catalyst exhibits outperformed performance in n-hexadecane hydroisomerization, i.e., the yield of isomerized hexadecane can reach 87.9 %, which is among the relatively high level compared with the previous reported Pt/zeolite counterparts. Moreover, the catalyst also displays excellent stability (no deactivation within 100 h). The disclosed structure-catalysis relationship provides rational reference for designing the synergistic meta-acid active sites in the hydroisomerization of long-chain n-alkanes.