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首页> 外文期刊>Journal of Non-Crystalline Solids: A Journal Devoted to Oxide, Halide, Chalcogenide and Metallic Glasses, Amorphous Semiconductors, Non-Crystalline Films, Glass-Ceramics and Glassy Composites >Surface nature of nanoparticle gold/iron oxide aerogel catalysts
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Surface nature of nanoparticle gold/iron oxide aerogel catalysts

机译：纳米金/氧化铁气凝胶催化剂的表面性质

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The aerogel catalysts investigated are constituted by two chemically different nanoparticle systems consisting of the gold phase and the iron oxide support. High-resolution transmission electronic microscopy (HRTEM) showed an increased surface roughness for aerogel particles with higher gold loading. X-ray photoelectron spectroscopy (XPS) revealed increases in the surface coverage of hydroxyl groups and the Fe2+/Fe3+ ratio due to the addition of gold, and showed the transition of gold from oxidized to metallic states due to calcination. In the presence of gold species, the Fe3+ satellite structure in XPS was not produced. The crystallinity of maghemite as the support was found quite stable with respect to gold addition and thermal treatment. The aerogels were evaluated for methanol oxidation carried out in an ambient flow reactor. The oxidation activity enhanced with decreasing catalyst pretreatment temperatures and with increasing gold loadings up to 5 wt%. A wide selectivity pattern formed between dimethyl ether and carbon dioxide products. The size of gold particles and the status of surface gold species played a crucial role in the catalytic conversion of methanol. The oxidized gold was more active than the metallic gold towards the total combustion to carbon dioxide. The surface nature has been proven to transform from strong Lewis acidic to high basic characters due to the formation of reactive hydroxyl groups near by the gold sites. (c) 2005 Elsevier B.V. All rights reserved.
机译：所研究的气凝胶催化剂由两个化学上不同的纳米颗粒体系组成，该体系由金相和氧化铁载体组成。高分辨率透射电子显微镜（HRTEM）显示，具有较高金载量的气凝胶颗粒的表面粗糙度增加。 X射线光电子能谱（XPS）显示由于添加了金，羟基的表面覆盖率和Fe2 + / Fe3 +比率增加，并且由于煅烧，表明金从氧化态过渡到金属态。在存在金物质的情况下，未产生XPS中的Fe3 +卫星结构。发现在添加金和热处理方面，以磁赤铁矿为载体的结晶度非常稳定。评估气凝胶在环境流动反应器中进行的甲醇氧化。氧化活性随催化剂预处理温度的降低和金含量的增加达到5 wt％而增强。在二甲醚和二氧化碳产物之间形成宽选择性图谱。金颗粒的大小和表面金物质的状态在甲醇的催化转化中起着至关重要的作用。在完全燃烧成二氧化碳的过程中，氧化的金比金属的金更具活性。由于在金部位附近形成反应性羟基，已证明表面性质可从强路易斯酸性转变为高碱性。 （c）2005 Elsevier B.V.保留所有权利。

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