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
Catalysis is one of the most important technical and scientific developments, on which present-day society is based. For example, it is crucial to the production of fertilizers or clean... Show more Catalysis is one of the most important technical and scientific developments, on which present-day society is based. For example, it is crucial to the production of fertilizers or clean fuels and needed for the abatement of exhaust gases. Frequently, the employed catalysts are being discovered in a very empirical way; by trial and error. However, designing catalysts based on detailed understanding is preferred. Obtaining understanding is very difficult, because catalysts are very complex materials. Furthermore, its properties often depend on the atmosphere surrounding the catalysts, i.e., the temperature and pressure of reactants and products, which they are exposed to, and these properties also change over time. The major part of this thesis focuses on structural changes of Pt model catalysts exposed to high oxygen pressures at elevated temperatures. The changes were measured with a ReactorSTM, a special version of a scanning tunneling microscope (STM) adapted to operate at high pressure and temperatures. These observations show that various surface oxide with a single-layer thickness form under reaction conditions. These oxides are structurally and chemically different from the Pt bulk oxides. The second part describes a set of experiments to understand the role of low-coordinated atoms and water in Au-catalyzed CO oxidation. Show less
