Department of Chemistry and Centre of Excellence NIS, University of Torino, via P. Giuria 7, 10125 Torino, Italy.
Phys Chem Chem Phys. 2013 Aug 28;15(32):13446-61. doi: 10.1039/c3cp50990g.
In situ FTIR spectroscopy was employed to investigate some aspects of the ambient temperature (actually, IR-beam temperature) adsorption of acetone on various pure and sulfate-doped zirconia specimens. Acetone uptake yields, on all examined systems and to a variable extent, different types of specific molecular adsorption, depending on the kind/population of available surface sites: relatively weak H-bonding interaction(s) with surface hydroxyls, medium-strong coordinative interaction with Lewis acidic sites, and strong H-bonding interaction with Brønsted acidic centres. Moreover acetone, readily and abundantly adsorbed in molecular form, is able to undergo the aldol condensation reaction (yielding, as the main reaction product, adsorbed mesityl oxide) only if the adsorbing material possesses some specific surface features. The occurrence/non-occurrence of the acetone self-condensation reaction is discussed, and leads to conclusions concerning the sites that catalyze the condensation reaction that do not agree with either of two conflicting interpretations present in the literature of acetone uptake/reaction on, mainly, zeolitic systems. In particular, what turns out to be actually necessary for the acetone aldol condensation reaction to occur on the examined zirconia systems is the presence of coordinatively unsaturated O(2-) surface sites of basicity sufficient to lead to the extraction of a proton from one of the CH3 groups of adsorbed acetone.
采用原位傅里叶变换红外光谱（FTIR）技术研究了在不同的纯氧化锆和硫酸盐掺杂氧化锆样品上，环境温度（实际上是红外光束温度）下丙酮吸附的一些方面。在所有研究的体系中，丙酮的吸附产率在不同程度上取决于表面活性位的种类/分布：与表面羟基的氢键相互作用较弱、与路易斯酸位的中等强度配位相互作用以及与布朗斯台德酸位的强氢键相互作用。此外，在分子形式下容易且大量吸附的丙酮，如果吸附材料具有一些特定的表面特征，则能够进行羟醛缩合反应（作为主要反应产物，生成吸附的均三甲苯氧化物）。讨论了丙酮自缩合反应的发生与否，并得出了关于催化缩合反应的活性位的结论，这些结论与文献中关于丙酮在主要是沸石体系上的吸收/反应的两种相互矛盾的解释不一致。特别是，对于在研究的氧化锆体系上发生的丙酮羟醛缩合反应，实际上必需的是存在足够碱性的配位不饱和 O(2-)表面位，从而从吸附的丙酮的一个 CH3 基团中提取质子。
