CONFIRMATION OF SULFUR TOLERANCE OF BIMETALLIC PD-PT SUPPORTED ON HIGHLY ACIDIC USY ZEOLITE BY EXAFS

The sulfur tolerance (i.e., degree of sulfidation) of Pd and Pt in sul fided bimetallic Pd-Pt catalysts (Pd:Pt mole ratio of 4:1) supported o n USY (ultrastable Y) zeolites (SiO2/Al2O3 = 10.7. 48, and 310) was in vestigated using an extended X-ray absorption fine structure (EXAFS) m ethod. The sulfidation of the catalysts was done in a 1000 ppm H2S-2% H-2/N-2 stream at 573 K for 0.5 h. In the Fourier transforms of Pd K-e dge and Pt L-III-edge EXAFS spectra both of the peaks due to metallic Pd and to metallic Pt for the Pd-Pt/USY (SiO2/Al2O3 = 10.7) catalyst r emained most after sulfidation. Further, the results of the Fourier tr ansforms confirmed that the sulfur tolerance of both Pd and Pt decreas ed with increasing SiO2/Al2O3 ratio, suggesting that Pd and Pt become sulfur-tolerant when Pd-Pt bimetallic particles are supported on highl y acidic USY zeolite.