Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208, USA.
Phys Chem Chem Phys. 2011 Nov 21;13(43):19573-9. doi: 10.1039/c1cp21660k. Epub 2011 Oct 5.
Adsorption and desorption of trans-2-methyl-2-pentenoic acid (MPeA) in dichloromethane (CH(2)Cl(2)) were investigated by using in situ attenuated total reflection infrared (ATR-IR) spectroscopy. A liquid flow-through spectroscopic cell allowed for high quality spectra to be obtained from deposited thin films of Al(2)O(3) and 1 wt% Pd/γ-Al(2)O(3) on a ZnSe internal reflection element. The MPeA molecules adsorb on both Al(2)O(3) and Pd surfaces molecularly and dissociatively under the concentration range examined (2-16 mM). In the case of molecular adsorption, both monomer (ν(C=O) ~ 1720 cm(-1)) and dimer (ν(C=O) ~ 1685 cm(-1)) species are observed to adsorb, with the relative amount of monomer to dimer dependent on the surface and the liquid phase acid concentration. In the case of dissociative adsorption, the acid adsorbs predominantly in a bridged bidentate configuration, as adjudged by the ca. 150-220 cm(-1) separation between asymmetric and symmetric vibrational bands. All of these species are found to be strongly adsorbed on both Al(2)O(3) and 1 wt% Pd/γ-Al(2)O(3) surfaces, even under pure solvent flow after adsorption.
采用原位衰减全反射红外光谱法（ATR-IR）研究了反-2-甲基-2-戊烯酸（MPeA）在二氯甲烷（CH（2）Cl（2））中的吸附和解吸。液体流通光谱池允许从沉积在 ZnSe 内反射元件上的 Al（2）O（3）和 1wt%Pd/γ-Al（2）O（3）的薄膜上获得高质量的光谱。在研究的浓度范围内（2-16mM），MPeA 分子在 Al（2）O（3）和 Pd 表面上以分子和离解方式吸附。在分子吸附的情况下，观察到单体（ν（C=O）1720cm（-1））和二聚体（ν（C=O）1685cm（-1））物种都吸附，单体与二聚体的相对量取决于表面和液相酸浓度。在离解吸附的情况下，酸主要以桥联双齿配位的形式吸附，这可以通过不对称和对称振动带之间约 150-220cm（-1）的间隔来判断。在吸附后仅在纯溶剂流的情况下，所有这些物种都被发现强烈吸附在 Al（2）O（3）和 1wt%Pd/γ-Al（2）O（3）表面上。
