Pt@SAPO-11 bifunctional catalysts with spatial architecture constructed via a seed-directed solvent-free strategy for n-dodecane hydroisomerization

Abstract

Inferior sintering-resistance of metal nanoparticles is an obstacle restricting the development of bifunctional catalysts in chemical industry. The construction of spatial architecture in zeolitic framework can enhance the stability of metal nanoparticles and prolong the service life of catalysts. A seed-directed solvent-free strategy was proposed here to prepare a metal-confined catalyst along the zeolitic framework to sterically encapsulate metal nanoparticles. The use of raw materials without extra solvents could improve synthetic efficiency of each kettle, reduce economic cost and decrease environmental pollution caused by organic solvents. The status of metal species was observed by aberration-corrected TEM images and XPS spectra, and the intracrystalline Pt species were speculated to isomorphically substitute the framework Al and P or occupy tens of micropore to form structural defect sites, leading to a decrease in the support acidity and a better balanced bifunctionality. While enhancing the metal stability, the maximum yield of isomer products was increased to 75% versus 63% for the conventional specimen synthesized by hydrothermal and post-impregnated method on n-dodecane hydroisomerization. The results provide an efficient route to the synthesis of alternative bifunctional catalysts for n-alkanes hydroisomerization, and promote the high value-added conversion of downstream products in coal/natural gas chemical industry.