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 aimed at preparing and characterizing two different model catalysts after their exposure at different temperatures to oxygen, carbon monoxide and hydrogen. The experiments were... Show moreThis thesis aimed at preparing and characterizing two different model catalysts after their exposure at different temperatures to oxygen, carbon monoxide and hydrogen. The experiments were performed in an ultra-high vacuum (UHV) set-up using a range of techniques including scanning tunneling and atomic force microscopy. The first part of the thesis deals with platinum deposited onto highly oriented pyrolytic graphite (HOPG). It was found that a sub-monolayer of the deposited metal on this substrate forms randomly distributed two-/three-dimensional particles. Analysis of the morphology and height distribution of Pt particles on the HOPG(0001) surface after annealing in UHV and in the presence of low pressures of oxygen, carbon monoxide and hydrogen indicates that their growth proceeds via coalescence. The second part of the thesis is devoted to the preparation of model manganese oxide surfaces starting with the MnO(100) surface, which were used as a support for Pt deposits. The preparation of manganese oxide surfaces was based on annealing of MnO(100) single-crystals at different temperatures in UHV and in the presence of argon, oxygen and hydrogen. The first results of Pt deposition on the MnO(100) surface and on this surface altered by annealing in the presence of oxygen and hydrogen are described. Show less
