Zielinski Maciej, Juszczyk Wojciech, Kaszkur Zbigniew
Institute of Physical Chemistry, Polish Academy of Sciences ul. M. Kasprzaka 44/52 01-224 Warszawa Poland
National Centre for Nuclear Research, NOMATEN Centre of Excellence ul. A. Soltana 7 05-400 Otwock-Swierk Poland.
RSC Adv. 2022 Feb 15;12(9):5312-5323. doi: 10.1039/d1ra09434c. eCollection 2022 Feb 10.
Our research focuses on phenomena accompanying adsorption of mesityl oxide (4-methylpent-3-en-2-one) on the surface of heterogeneous supported gold catalysts: Au/CeO, Au/TiO and Au/SiO. We have studied reduction in the gas phase of (volatile) α,β-unsaturated carbonyl compounds (R-(V)ABUCC) which mesityl oxide is a basic model of. infrared (IR) spectroscopy was employed to establish that the most active catalysts allow adsorption of conjugated ketones or aldehydes in the enolate ( bridge-like adsorption through the oxygen from the carbonyl group and the β-carbon) and carboxylic form or with the C[double bond, length as m-dash]C double bond on a Lewis acidic site. Reductive properties of the catalysts and pure supports were studied by temperature-programmed reduction (TPR). We show that cerium(iv) oxide (CeO, ceria) and titanium(iv) oxide (TiO, titania) when decorated with gold nanoparticles (AuNP) can interact with hydrogen at temperatures approx. 150 °C lower than typical for pure oxides what includes even cyclic adsorption and instant release of H below 100 °C in the case of gold-ceria system. Morphology and structure characterisation by transmission electron microscopy (TEM) and powder X-ray diffraction (PXRD) confirms that, with the obtained Au loadings, we achieved excellent dispersion of AuNPs while maintaining their small size, preferably below 5 nm, even though the Au/CeO catalyst contained broad distribution of AuNPs sizes.
我们的研究聚焦于异质负载金催化剂（Au/CeO、Au/TiO和Au/SiO）表面上异亚丙基丙酮（4-甲基戊-3-烯-2-酮）吸附时伴随的现象。我们研究了（挥发性）α,β-不饱和羰基化合物（R-(V)ABUCC）在气相中的还原反应，异亚丙基丙酮是该反应的基本模型。采用红外（IR）光谱法确定，活性最高的催化剂能使共轭酮或醛以烯醇盐形式（通过羰基的氧和β-碳进行桥式吸附）以及羧基形式吸附，或者使碳-碳双键吸附在路易斯酸性位点上。通过程序升温还原（TPR）研究了催化剂和纯载体的还原性能。我们发现，用金纳米颗粒（AuNP）修饰的二氧化铈（CeO，氧化铈）和二氧化钛（TiO，氧化钛）在比纯氧化物典型温度低约150°C的温度下就能与氢气相互作用，在金-二氧化铈体系中，甚至在低于100°C时就会出现氢的循环吸附和瞬间释放。通过透射电子显微镜（TEM）和粉末X射线衍射（PXRD）进行的形态和结构表征证实，在所获得的金负载量下，我们实现了金纳米颗粒的优异分散，同时保持其小尺寸，最好低于5 nm，尽管Au/CeO催化剂中金纳米颗粒的尺寸分布较宽。
