Aktivitätsuntersuchungen und Methoden zur Regeneration von Katalysatoren für die autotherme Reformierung von Dieselkraftstoffen
Jülich / Forschungszentrum Jülich, Zentralbibliothek (2015, 2016) [Book, Dissertation / PhD Thesis]
The present study concerns the impacts that the molar ratios of reactants have on the catalytic activity of different catalyst systems while operating parameters are gradually altered. The hydrogen synthesized on the surfaces of catalysts varies with catalyst activity. If the H2 concentration drops, catalyst deactivation occurs, and the catalyst material is unsuitable for autothermal reforming (ATR). The main deactivation mechanisms are poisoning, carbon deposition, thermal degradation, mechanical wear, corrosion, and leaching. These forms of deactivation can cause total inactivity of the relevant catalyst system. Deactivation is a process that can alter the structure and state of the catalyst. The aforementioned mechanisms reduce the number of catalytically active centres on the surfaces, which gives rise to a loss of activity. An ideally designed catalyst system comprises a solid oxide substrate – the cordierite Mg2Al4Si5O18 – and an oxide washcoat upon which the catalyst is deposited. The washcoat enlarges the surface, ensuring better catalyst dispersion and thus activation. The catalyst is an agent that accelerates the chemical reaction but is not actually used up itself. Tried and tested catalysts are simply transition metals with a high conductivity, density, and melting point. As fuel, NExBTL and Ultimate Diesel, which have different chemical and physical properties, are used.The test reactor used in the analysis – an autothermal reformer – is designed so that the different catalyst systems can be exchanged quickly via a flange. Before and after their use in the test rig, the same procedure is used to analyse the samples and thus compare the fresh and aged catalysts. In the tests, the catalyst activity is determined on the basis of the H2 concentration. In addition, the results of the analyses before and after the tests permit conclusions on catalyst activity. These analytical results can then be correlated with the test results.