Abstract: The morphology and microstructure of support as well as the location, size and aggregation state of active metals in industrial spent catalysts Pt-Sn/γ-Al₂O₃ (PS-V) were comprehensively characterized by various characterization methods. The results of X-ray diffraction showed that the crystal structure and parameters of both spent and fresh catalysts had no obvious difference. The high-resolution transmission electron microscope (HRTEM) images showed that carrier part of the spent catalyst was transformed into α-Al₂O₃ from γ-Al₂O₃ with honeycomb or laminar microstructure. Meanwhile, massive Pt atoms reacted with Sn atoms to form Pt-Sn alloy aggregates with the dimension ranging from 20 nm to 150 nm, and the statistical average size of Pt-Sn alloy aggregates was about 50 nm. The results of aberration-corrected high-resolution scanning transmission electron microscopy (Cs-STEM) showed that the unaggregated Pt atoms were still dispersed at the atomic level on the surface of the carrier. The in-situ Fourier transform infrared spectrocopy of CO probe (CO-FTIR) showed that the Pt metals were aggregated in the spent catalyst, and the interaction with the carrier was basically disappeared. At the same time, the microstructure of industrial spent catalyst was analyzed from both support and metal, and the structure-activity relationship between the structure change and the performance decline of catalyst was given.

Key words: Cs-corrected STEM, CO-FTIR, Pt-Sn/γ-Al₂O₃, Reforming catalyst CR401, spent catalyst, microstructure