Pt nanoclusters entrapped within Cu-SSZ-13 zeolite for efficient propane dehydrogenation

Abstract

Pt-Cu bimetallic particles have been regarded as promising catalysts for propane dehydrogenation. The dispersion of Pt and Cu species on conventional supports always results in the formation of large Pt-Cu particles, and it is highly desirable to fabricate ultra-small Pt-Cu cluster catalysts for propane dehydrogenation. Herein, we used the isolated Cu species in the Cu-SSZ-13 to localize the Pt species and the alloying of Pt with Cu leads to a formation of ultra-small (<1 nm) Pt-Cu bimetallic clusters in the structure of SSZ-13. The structure of synthesized PtCu-SSZ-13 catalysts was studied by XRD, SEM, STEM, XPS, CO-FTIR, H₂-TPR and EXAFS techniques, which demonstrates that Pt-Cu clusters are entrapped in the micropore of SSZ-13 and their migration can be greatly inhibited. The synthesized PtCu-SSZ-13 catalyst shows high activity and good regeneration in propane dehydrogenation. The optimized catalyst 0.3 %PtCu-SSZ-13 delivers propane conversion of 28.5 % (close to equilibrium conversion) with 100 % propane as feed under WHSV of 7.1 h⁻¹ at 520°C, and its catalytic performance can be completely regenerated via calcination in air. Density functional theory (DFT) calculations indicate that the unique Pt-Cu bimetallic nanocluster structure reduces the energy potential for propane dehydrogenation as well as promotes the adsorption of C₃H₈ and desorption of C₃H₆ thus enhancing the activity of the PtCu-SSZ-13 catalyst.