Deactivation of Ni/TiO2 catalyst in the hydrogenation of nitrobenzene in water and improvement in its stability by coating a layer of hydrophobic carbon
Deactivation of Ni/TiO2 catalyst in the hydrogenation of nitrobenzene in water and improvement in its stability by coating a layer of hydrophobic carbon
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DOI：
10.1016/j.jcat.2012.04.020
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发表时间：
2012-07-01
影响因子：
7.3
通讯作者：
Zhao, Fengyu
中科院分区：
文献类型：
--
作者：
Lin, Weiwei;Cheng, Haiyang;Zhao, Fengyu
水作为一种绿色溶剂取代传统的有机溶剂在有机合成中具有许多优点。本文以Ni/TiO_2为催化剂，对硝基苯在水溶液中的加氢反应进行了研究，主要目的是考察Ni/TiO_2催化剂的活性及其稳定性。实验结果和XRD、XPS、ICP数据分析表明，Ni与水反应生成氢氧化镍是导致Nil-TiO_2催化剂快速失活的主要原因。在此基础上，我们设计了一种具有疏水性的催化剂，以防止Ni活性物种与水接触，从而在Ni/TiO 2表面包覆一层疏水碳层。正如预期的那样，通过水热方法将疏水碳成功地涂覆在Ni/TiO 2催化剂上，并且它们在本水溶液反应体系中呈现出更高的反应性和改善的稳定性;在使用过的和水处理过的碳涂覆的Ni/TiO 2样品上未检测到氢氧化镍。活性炭改性后的催化剂的疏水性增强，不仅阻止了水与镍催化物种的接触，而且保护了金属镍在暴露于空气中时被氧化。(C)2012 Elsevier Inc. All rights reserved.
Water as a green solvent to replace the conventional organic solvent presents many advantages in the organic synthesis. The hydrogenation of nitrobenzene in water has been investigated by using Ni/TiO2 catalyst in this work, and our main purpose was focused on the Ni/TiO2 catalyst activity and its stability improvement. The experimental results and analysis from the data of XRD, XPS, ICP revealed that the formation of nickel hydroxide from metallic nickel reacting with water caused a rapid deactivation of Nil TiO2 catalyst. Based on these, we designed a catalyst with hydrophobic property to prevent the nickel active species to contact with water: thus, a hydrophobic carbon layer was coated on the surface of Ni/TiO2. As expected, the hydrophobic carbon was successfully coated on Ni/TiO2 catalysts by a hydrothermal method and they presented higher reactivity and improved stability in the present aqueous reaction system; nickel hydroxide was not detected on the used and water treated carbon-coated Ni/TiO2 samples. The improved abilities were attributed to the increased hydrophobicity of catalysts modified by carbon, which not only prevents water to contact with nickel catalytic species, but also protects the metallic nickel to be oxidized as it exposed to air. (C) 2012 Elsevier Inc. All rights reserved.