Lundie David T, McInroy Alastair R, Marshall Robert, Winfield John M, Jones Peter, Dudman Chris C, Parker Stewart F, Mitchell Chris, Lennon David
Department of Chemistry, Joseph Black Building, The University of Glasgow, Glasgow, G12 8QQ, UK.
J Phys Chem B. 2005 Jun 16;109(23):11592-601. doi: 10.1021/jp0405963.
The surface acidity of an activated eta-alumina catalyst has been investigated by examining the interaction of pyridine with the catalyst by a combination of gravimetric and volumetric adsorption isotherms, infrared spectroscopy (diffuse reflectance and transmission), inelastic neutron scattering spectroscopy, temperature-programmed desorption spectroscopy, and gravimetric desorption experiments. From previous work, this surface was considered to contain three types of Lewis acid sites of increasing acidity: weak, medium, and strong. However, this multitechnique approach reveals the presence of an additional type of Lewis acid site. Although the traditional pyridine ring modes about 1580 cm(-1) are consistent with previous studies, temperature-programmed infrared spectroscopy of the surface hydroxyl groups and mass-selective temperature-programmed desorption experiments establish that the medium-strength Lewis acid category can be subdivided into two components. In this way, the surface structure of the activated catalyst is redefined as comprising (i) weak, (ii) medium-weak, (iii) medium-strong and (iv) strong Lewis acid sites. The (O-H) stretching mode of surface hydroxyl groups provides information on the local structure of the distinct sites, and schematic descriptions for these sites are proposed.
通过重量法和容量法吸附等温线、红外光谱（漫反射和透射）、非弹性中子散射光谱、程序升温脱附光谱以及重量法脱附实验等方法，研究了吡啶与活性 η-氧化铝催化剂之间的相互作用，以此来探究该催化剂的表面酸度。根据之前的研究，该表面被认为含有三种酸度递增的路易斯酸位点：弱、中、强。然而，这种多技术方法揭示了另外一种路易斯酸位点的存在。尽管传统的吡啶环模式在约1580 cm⁻¹ 处与之前的研究一致，但表面羟基的程序升温红外光谱和质量选择程序升温脱附实验表明，中等强度的路易斯酸类别可细分为两个组分。通过这种方式，活性催化剂的表面结构被重新定义为包含（i）弱、（ii）中弱、（iii）中强和（iv）强路易斯酸位点。表面羟基的（O-H）伸缩模式提供了不同位点局部结构的信息，并对这些位点提出了示意性描述。
