Tunable gas phase hydrogenation of m-dinitrobenzene over alumina supported Au and Au–Ni

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• 作者：Fern ; o Cá ; rdenas-Lizana ; Santiago Gó ; mez-Quero ; Christopher J. Baddeley ; Mark A. Keane
• 关键词：Selective hydrogenation ; m-Dinitrobenzene ; Reductive deposition of Au on Ni ; Au/Al₂O₃ ; Ni/Al₂O₃ ; Au– ; Ni/Al₂O₃
• 刊名：Applied Catalysis A: General
• 出版年：2010
• 出版时间：20 October 2010
• 年：2010
• 卷：387
• 期：1-2
• 页码：155-165
• 全文大小：1534 K

文摘

The gas phase hydrogenation of m-dinitrobenzene (m-DNB) has been investigated over alumina supported Au (1 mol % ), Ni (10 mol % ) and Au–Ni (Au/Ni mol ratio = 1/10). Au/Al₂O₃ delivered a time invariant exclusive formation of m-nitroaniline (partial reduction), Ni/Al₂O₃ promoted total nitro-group reduction to give m-phenylenediamine as the sole product and Au–Ni/Al₂O₃ generated both products (partial and complete hydrogenation); Ni/Al₂O₃ and Au–Ni/Al₂O₃ exhibited a temporal decline in activity. A physical mixture of Au/Al₂O₃ + Ni/Al₂O₃ delivered a hydrogenation rate and product composition that was equivalent to that obtained with Ni/Al₂O₃, i.e. Au/Al₂O₃ had a negligible contribution to the catalytic process, which was governed by the Ni component in the mixture. The catalysts have been characterized in terms of temperature-programmed reduction (TPR), H₂ chemisorption/temperature-programmed desorption (TPD), BET area/pore volume, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV–vis (DRS UV–vis) and HRTEM-EDX measurements. The presence of zero valent Au and Ni is established post-TPR where EDX mapping has revealed a close surface proximity of both metals (mean particle size = 9 nm) in Au–Ni/Al₂O₃ with evidence (from XPS) of electron donation from Ni to Au. While the addition of Au to Ni/Al₂O₃ served to suppress H₂ chemisorption post-TPR, H₂-TPD revealed a more facile release of a greater amount of hydrogen from Au–Ni/Al₂O₃ relative to Ni/Al₂O₃, which we attribute to surface Au–Ni interaction that is also manifest in the hydrogenation activity/selectivity response. Our results establish the feasibility of controlling product distribution through the application of mono- (Au or Ni) and bimetallic (Au–Ni) catalysts.