One-pot synthesis of the highly efficient bifunctional Ni-SAPO-11 catalyst

Hydroisomerization of linear alkanes to branched isomers is an important petrochemical process for production of gasoline with high octane number. Non-noble metal bifunctional catalysts used in this process always suffer from low metal dispersion and poor metal-acid synergy. Herein, a facile one-pot synthesis method was used to simultaneously regulate metal particle sizes and acidity of the Ni-SAPO-11 hydroisomerization catalyst. The physicochemical properties are investigated using XANES, EXAFS, TEM/STEM, FT-IR, XPS, UV–vis and NH₃-TPD. Apart from the highly dispersed nickel nanoparticles with an average diameter of 8 nm, the framework Ni²⁺ ions are generated via substituting framework Al³⁺ ions of the SAPO-11. The formed NiP-OH structures have lower deprotonation energy (DPE) than the SiAl-OH ones, contributing more and stronger acid sites to the Ni-SAPO-11 catalyst. The great metal-acid synergy including high metal to acid sites ratio (n_Ni/n_A) and close intimacy is obtained for the Ni-SAPO-11 catalyst. The Ni-SAPO-11 catalyst outperforms the counterpart prepared by the impregnation method and exhibits comparable activity and isomers selectivity to the Pt/SAPO-11 catalyst in the n-hexane hydroisomerization.