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首页> 外文期刊>Chemistry: A European journal >Interfacial impregnation chemistry in the synthesis of nickel catalysts supported on titania
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Interfacial impregnation chemistry in the synthesis of nickel catalysts supported on titania

机译：二氧化钛负载镍催化剂合成中的界面浸渍化学

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摘要

The interfacial chemistry of the impregnation step involved in the preparation of nickel catalysts supported on titania is presented. Several methodologies based on deposition data, pH measurements, potentiometric mass titrations, and microelectrophoresis have been used in conjunction with diffuse reflectance UV/Vis/NIR spectroscopy, simulations, and semiempirical quantum chemical calculations. Three mononuclear inner-sphere complexes were formed at the compact layer of the "titania/electrolyte solution" interface: A monosubstituted, dihydrolyzed complex above a terminal oxo group, a disubstituted, dihydrolyzed complex above two terminal adjacent oxo groups, and a disubstituted, nonhydrolyzed complex above one terminal and one bridging adjacent oxo groups. The monosubstituted, dihydrolyzed complex predominates. The contribution of the disubstituted configurations is also important at very low NiII surface concentration, but it decreases as the NiII surface concentration increases. In addition, bi-and trinuclear inner-sphere complexes were formed. The receptor site involves one bridging and two terminal oxo groups in the first case and two bridging and three terminal oxo groups in the second case. The relative surface concentrations of these configurations increase initially with NiII surface concentration and then remain practically constant. The understanding of these interfacial processes at a molecular level is very important to shift the catalytic synthesis from an art to a science as well as to obtain strict control of the impregnation step and, to some extent, of the whole preparative sequence. This study is very relevant to the synthesis of submonolayer/monolayer nickel catalysts supported on TiO2 following equilibrium deposition filtration (otherwise called equilibrium adsorption).
机译：介绍了在二氧化钛上负载的镍催化剂的制备过程中涉及的浸渍步骤的界面化学。基于沉积数据，pH测量，电位滴定和微电泳的几种方法已与漫反射UV / Vis / NIR光谱，模拟和半经验量子化学计算结合使用。在“二氧化钛/电解质溶液”界面的致密层上形成了三个单核内球络合物：一个在末端氧代基上方的单取代的二水解复合物，在两个末端相邻的氧代基上方的一个双取代的二水解复合物以及一个被双取代的非水解的复合物。在一个末端和一个桥接相邻的氧代基团上方的络合物。单取代的二水解复合物占主导。在非常低的NiII表面浓度下，二取代构型的贡献也很重要，但随着NiII表面浓度的增加，其降低。另外，形成了双核和三核内球复合物。在第一种情况下，受体位点涉及一个桥和两个末端氧代基团，在第二种情况下，受体位点涉及两个桥和三个末端氧代基团。这些构型的相对表面浓度最初随NiII表面浓度而增加，然后实际上保持恒定。在分子水平上对这些界面过程的理解对于将催化合成从一门技术转移到一门科学以及对浸渍步骤以及在一定程度上对整个制备顺序进行严格控制非常重要。这项研究与在平衡沉积过滤（也称为平衡吸附）之后负载在TiO2上的亚单层/单层镍催化剂的合成非常相关。

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