Selective hydrogenation of amides using bimetallic Ru/Re and Rh/Re catalysts
Selective hydrogenation of amides using bimetallic Ru/Re and Rh/Re catalysts
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DOI：
10.1016/j.jcat.2010.12.009
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发表时间：
2011-03-07
影响因子：
7.3
通讯作者：
Whyman, Robin
中科院分区：
文献类型：
--
作者：
Beamson, Graham;Papworth, Adam J.;Whyman, Robin
分别由Ru-3(CO)(12)/Re-2(CO)(10)和Rh-6(CO)(16)/Re-2(CO)(10)原位生成的Ru/Re和Rh/Re催化剂对环己烷甲酰胺(CyCONH2)液相加氢合成CyCH2NH2的选择性高达95%，不需要氨气来抑制仲胺和叔胺的生成。在50-100bar H-2和>；=150(Rh)-160℃(Ru)的反应条件范围内，注意到良好的酰胺转化率。Ru：Re和Rh：Re组成的变化只会导致产物选择性的微小变化，而在较高的Re水平上没有证据表明催化剂失活。原位HP-FTIR光谱分析表明，催化剂的生成是通过金属羰基前驱体的分解进行的。用X射线衍射仪、XPS和EDX-STEM对催化剂进行了非原位表征，证明了这些催化剂的活性组份中含有双金属Ru/Re和Rh/Re纳米团簇，其表面在用于酰胺还原后发生了显著的氧化。讨论了酰胺加氢的可能的机理途径，包括初始脱水成腈，一种可能专用于伯胺的途径，以及通常假设的亚胺中间体的证据。(C)2010 Elsevier Inc.保留所有权利。
Heterogeneous Ru/Re and Rh/Re catalysts, formed in situ from Ru-3(CO)(12)/Re-2(CO)(10) and Rh-6(CO)(16)/Re-2(CO)(10) respectively, are effective for the liquid phase hydrogenation of cyclohexanecarboxamide (CyCONH2) to CyCH2NH2 in up to 95% selectivity without the requirement for ammonia to inhibit secondary and tertiary amine formation. Good amide conversions are noted within the reaction condition regimes 50-100 bar H-2 and >= 150 (Rh) - 160 degrees C (Ru). Variations in Ru:Re and Rh:Re composition result in only minor changes in product selectivity with no evidence of catalyst deactivation at higher levels of Re. In situ HP-FTIR spectroscopy has shown that catalyst genesis occurs via decomposition of the metal carbonyl precursors. Ex situ characterization, using XRD, XPS and EDX-STEM, has provided evidence for the active components of these catalysts containing bimetallic Ru/Re and Rh/Re nanoclusters, the surfaces of which become significantly oxidized after use in amide reduction. Potential mechanistic pathways for amide hydrogenation are discussed, including initial dehydration to nitrile, a pathway potentially specifically accessible to primary amides, and evidence for often postulated imine intermediates. (C) 2010 Elsevier Inc. All rights reserved.