Alumina-grafted SBA-15 as a high performance support for Pd-catalysed cinnamyl alcohol selective oxidation
Alumina-grafted SBA-15 as a high performance support for Pd-catalysed cinnamyl alcohol selective oxidation
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DOI：
10.1016/j.cattod.2013.11.056
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发表时间：
2014-06-15
期刊：
影响因子：
5.3
通讯作者：
Lee, Adam F.
中科院分区：
文献类型：
--
作者：
Parlett, Christopher M. A.;Durndell, Lee J.;Lee, Adam F.
接枝到有序介孔 SBA-15 二氧化硅骨架上的超薄氧化铝单层提供了具有独特结构性能和表面化学性质的复合催化剂载体。通过湿法浸渍沉积在 Al-SBA-15 上的钯纳米粒子表现出纯氧化铝的高分散性和表面氧化特性，以及热稳定、高面积介孔二氧化硅的高活性位点密度特性。与介孔氧化铝或二氧化硅载体相比，这种组合显着提高了 Pd/Al-SBA-15 上肉桂醇的有氧选择性氧化 (selox) 速率。操作性液相 XAS 强调了溶解氧与分散在 Al-SBA-15 上的钯纳米颗粒的氧化态之间的相互作用，以实现在线还原：流动氧气的环境压力足以阻碍氧化钯还原为金属，从而能够保持高 selox 活性，而 PdO 快速还原并伴随催化剂失活 发生在静态氧气下。对所需肉桂醛产物的选择性反映了这些活性趋势，流动的氧气最大限度地减少了肉桂醇反应物到反式-β-甲基苯乙烯的C-O裂解，以及肉桂醛脱羰到苯乙烯的过程。 (C) 2013 Elsevier B.V. 保留所有权利。
Ultrathin alumina monolayers grafted onto an ordered mesoporous SBA-15 silica framework afford a composite catalyst support with unique structural properties and surface chemistry. Palladium nanopartides deposited onto Al-SBA-15 via wet impregnation exhibit the high dispersion and surface oxidation characteristic of pure aluminas, in conjunction with the high active site densities characteristic of thermally stable, high-area mesoporous silicas. This combination confers significant rate enhancements in the aerobic selective oxidation (selox) of cinnamyl alcohol over Pd/Al-SBA-15 compared to mesoporous alumina or silica supports. Operando, liquid-phase XAS highlights the interplay between dissolved oxygen and the oxidation state of palladium nanoparticles dispersed over Al-SBA-15 towards on-stream reduction: ambient pressures of flowing oxygen are sufficient to hinder palladium oxide reduction to metal, enabling a high selox activity to be maintained, whereas rapid PdO reduction and concomitant catalyst deactivation occurs under static oxygen. Selectivity to the desired cinnamaldehyde product mirrors these trends in activity, with flowing oxygen minimising C-O cleavage of the cinnamyl alcohol reactant to trans-beta-methylstyrene, and of cinnamaldehyde decarbonylation to styrene. (C) 2013 Elsevier B.V. All rights reserved.