In situ XAFS analysis of Pd–Pt catalysts during hydrotreatment of model oil

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• 作者：Kyoko K. Bando ; Toshihide Kawai ; Kiyotaka Asakura ; Takashi Matsui ; Lionel Le Bihan ; Hiroyuki Yasuda ; Yuji Yoshimura and S. Ted Oyama
• 关键词：In situ XAFS ; Hydrodearomatization ; Hydrodesulfurization ; Pd– ; Pt ; Model oil
• 刊名：Catalysis Today
• 出版年：2006
• 期刊代码：13_09205861
• 类别：ce
• 出版时间：15 February 2006
• 卷：111
• 期：3-4
• 页码：199-204
• 文件大小：353 K

摘要

Supported Pd–Pt catalysts are efficient for hydrodesulfurization (HDS) and hydrodearomatization (HDA) reactions of diesel fuel and their activity varied with the kinds of supports. Concerning HDA, alumina supported catalysts showed four times higher TOF (turn over frequency) than silica supported one. In order to elucidate the difference in activity, the structural analysis of the active phase was performed. After reduction pretreatment, relatively uniform and large metallic alloy Pd–Pt particles were formed on SiO₂, whereas, Pd and Pt atoms formed rather segregated particles on Al₂O₃. Subsequent X-ray absorption of fine structure (XAFS) analysis under HDS conditions showed no contribution of sulfur for SiO₂ supported catalyst, whereas, formation of sulfided metal species was observed in XAFS spectra for the Al₂O₃ supported catalyst. It is suggested that on Pd–Pt/SiO₂, thin sulfide layer on the metal cluster surface blocked the active sites and lowered the HDA activity. Presence of partially sulfided phase originated from rather segregated structure like Pd–Pt/Al₂O₃ is thought to be requisite for high HDA activity.