| Heterogeneous catalysis takes place at the interface between the solid catalyst and the gas- or liquid-phase that contains the reactant. Most methods used in traditional catalyst characterization study the solid catalyst itself, and do not provide much information on adsorbates. Ultrahigh vacuum studies have furnished rich information on the chemistry of many organic compounds on catalytic surfaces, but under conditions far away from reality. In-situ probing is key to understand heterogeneous liquid-phase catalysis, but such kind of studies is challenging and has not yet been advanced. In this Dissertation, systematical work has been carried out using both reflection-absorption infrared spectroscopy to study the adsorption on solid surfaces and solubility tests to study the relevant solution chemistry. The following specific topics were addressed.;(1) The gas effect on cinchonidine adsorption. The facilitating effect of H2 and the poisoning effect of CO on cinchonidine adsorption, and the synergic effect of O2 and cinchonidine on CO removal, were identified. (2) The decomposition of a number of solvents and reactants on Pt. The ease of decarbonylation was correlated to the presence of C-O versus C=O functional groups, and also to bulkiness of the substituent groups. (3) The development of a novel diagnosing method based on the marked solvent effect on CO oxidation on Pt, to further pin down the low-coverage CO originating from the decomposition of alpha-ketoesters and diketones. (4) The solvent effect on the adsorption-desorption equilibrium of cinchona alkaloids on Pt. Correlations among solvent polarity, cinchona solubility, and catalytic performance were identified. (5) The cinchona solubility as a function of both modifier structure and solvent temperature. (6) The adsorption and competition of a number of quinoline-derived polycyclic aromatic compounds on Pt. All these results have been correlated to the catalysis data reported in literature. Finally, a number of preliminary experiments have been carried out to test the feasibility of research directions for the future. |
