Hydrodesulfurization (HDS) is an ubiquitous part of oil refining that ensures that fuels are cleaned of impurities and environment release of pollutants such as SOx and NOx gasses are minimized. In... Show moreHydrodesulfurization (HDS) is an ubiquitous part of oil refining that ensures that fuels are cleaned of impurities and environment release of pollutants such as SOx and NOx gasses are minimized. In this thesis, atomic level insights into the process of HDS are gained by exploring various methods of generating the catalytically active CoMoS phase as well as the effect of the reaction gasses like hydrogen and methylthiol on the atomic structure of the catalyst at industrially relevant conditions. For this purpose, a variety of techniques such as high-pressure scanning tunneling microscopy, X-ray photoelectron spectroscopy and electron diffraction are used. Furthermore, the studies presented in this thesis make several steps towards bridging the pressure and materials gap between the fundamental catalysis studies and industrial catalytic conditions. The results of this work pave way for more fundamental research with the help of theoretical methods such as DFT calculations which can help with designing more efficient catalysts to meet the future demands of clean fuels. Show less
This thesis uses the surface science approach to address questions regarding the interaction of oxygen with platinum and its subsequent reaction with carbon monoxide. A Pt(111) single crystal... Show moreThis thesis uses the surface science approach to address questions regarding the interaction of oxygen with platinum and its subsequent reaction with carbon monoxide. A Pt(111) single crystal surface is used as a model for the catalyst. Chapter 1 provides an overview of the literature on the subject. The description of employed experimental techniques and their backgrounds are presented in Chapter 2. Chapter 3 discusses the adsorption of oxygen on Pt(111) at various temperatures and its role in the oxidation of carbon monoxide. Chapter 4 gives an atomic scale insight into the reaction between adsorbed oxygen and carbon monoxide for different ratios of oxygen and carbon monoxide pressures. In Chapter 5, the reaction between CO and oxygen on Pt(111) was used to register noise in tunneling current due to diffusion and recombination of molecules on the catalytically active surface, to draw conclusions on the most likely rate-limiting step in the process Show less
In this thesis two subjects are treated. The first one is the poisoning of hydrogen dissociation on Pt(533) by CO. It was found that decorating the step edges of Pt(533) by CO does not only block... Show moreIn this thesis two subjects are treated. The first one is the poisoning of hydrogen dissociation on Pt(533) by CO. It was found that decorating the step edges of Pt(533) by CO does not only block the indirect dissociation mechanism and the direct dissociation at step edges but also introduces an additional barrier for dissociation at the terraces. The second area contains a description of how a cylindrical Ni single crystal is employed in dissociation dynamics measurements. The analysis of the circumference by LEED is explained. Results for hydrogen dissociation are shown. They are analyzed by means of a model introduced for hydrogen dissociation on stepped Pt surfaces with (111) terraces and (100) steps. Show less
