A series of Pt−Sn/SBA-15 catalysts (Sn/Pt nominal ratios: 0−3) prepared by direct reduction were applied to ethylbenzene dehydrogenation to styrene. The characterization by X-ray diffraction, X-ray absorption fine structure, CO adsorption, transmission electron microscopy, and X-ray photoelectron spectroscopy revealed the formation of highly dispersed and stable Pt−Sn alloy particles [Pt x Sn y (x/ y ≥ 3) and Pt−Sn alloys having Sn-rich surfaces] on SBA-15. Nonalloyed Sn existed as highly dispersed SnO 2 . 1Pt−1Sn/ SBA-15 (Sn/Pt nominal ratio = 1) exhibited the highest activity, on which Pt 3 Sn alloy nanoparticles were mainly formed. In contrast, PtSn alloy was dominant on Pt−Sn/SBA-15 catalysts whose Sn/Pt nominal ratios were larger than 1, and the activity was decreased. Furthermore, 1Pt−1Sn/SBA-15 exhibited a higher stability than Pt/SBA-15 and 1Pt−1Sn/SiO 2 . The addition of Sn not only inhibits C−C bond cleavage and improves selectivity toward styrene but also enhances the "drainoff" effect, allowing coke precursors to migrate from the active metals to SBA-15 with large surface area.
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