Effect of FeOx Modification of Al2O3 on Its Supported Au Catalyst for Hydrogenation of 5-Hydroxymethylfurfural

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• 作者：Junya Ohyama ; Yoshinori Hayashi ; Kakuya Ueda ; Yuta Yamamoto ; Shigeo Arai ; Atsushi Satsuma
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：July 21, 2016
• 年：2016
• 卷：120
• 期：28
• 页码：15129-15136
• 全文大小：425K
• 年卷期：0
• ISSN：1932-7455

文摘

To enhance the hydrogenation activity of alumina supported Au (Au/Al₂O₃) catalyst for selective hydrogenation of 5-hydroxymethylfurfural (HMF), an important biomass-derived aldehyde, Al₂O₃ support was modified with iron oxide (FeO_x). The apparent catalytic activity of the FeO_x/Al₂O₃ supported Au (Au/FeO_x/Al₂O₃) catalysts increased as an increase of Fe loading up to 10 wt % (3–4 times higher than Au/Al₂O₃). When the Fe loading was more than 10 wt %, the apparent catalytic activity decreased, and Au/α-Fe₂O₃ showed much lower activity than Au/Al₂O₃. The Fe K-edge X-ray absorption fine structure (XAFS) spectra and the atomic scale observation using aberration corrected scanning transmission electron microscopy (Cs-STEM) suggested positive and negative effects of FeO_x support. As the positive effect, FeO_x promotes formation of Au clusters by reduction of Au single atoms having low or no catalytic activity for the hydrogenation. On the other hand, as the negative effect, FeO_x, more specifically, large α-Fe₂O₃, can form buried structure of Au clusters in FeO_x due to reduction of α-Fe₂O₃ to Fe metal by H₂ pretreatment. The buried structure of Au clusters is responsible for the decrease of hydrogenation activity at high Fe loading. In contrast, dispersed Fe₂O₃ species of Au/FeO_x/Al₂O₃ with less than 20 wt % of Fe loading was not subjected to the reduction of Fe₂O₃ species to Fe metal, and the Au clusters were exposed on the support surface. Therefore, the dispersed Fe₂O₃ on Al₂O₃ is effective to enhance the activity of Au catalysts for the hydrogenation because of the formation of exposed small Au clusters.