Aktivitätsuntersuchungen und Methoden zur Regeneration von Katalysatoren für die autotherme Reformierung von Dieselkraftstoffen

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 H$_{2}$ 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 structureand 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 Mg$_{2}$Al$_{4}$Si$_{5}$O$_{18}$ – 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 physicalproperties, 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 H$_{2}$ 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

Hydrogen production from bio-fuels using precious metal catalysts

Fuel cell systems with integrated autothermal reforming unit require active and robust catalysts for H2 production. Thus, an experimental screening of catalysts for autothermal reforming of commercial biodiesel fuel was performed. Catalysts consisted of a monolithic cordierite substrate, an oxide support (γ-Al2O3) and Pt, Ru, Ni, PtRh and PtRu as active phase. Experiments were run by widely varying the O2/C and H2O/C molar ratios at different gas hourly space velocities. Fresh and aged catalysts were characterized by temperature programmed methods and thermogravimetry to find correlations with catalytic activity and stability

Hydrogen production from bio-fuels using precious metal catalysts

Fuel cell systems with integrated autothermal reforming unit require active and robust catalysts for H2 production. Thus, an experimental screening of catalysts for autothermal reforming of commercial biodiesel fuel was performed. Catalysts consisted of a monolithic cordierite substrate, an oxide support (γ-Al2O3) and Pt, Ru, Ni, PtRh and PtRu as active phase. Experiments were run by widely varying the O2/C and H2O/C molar ratios at different gas hourly space velocities. Fresh and aged catalysts were characterized by temperature programmed methods and thermogravimetry to find correlations with catalytic activity and stability

Hydrogen production from bio-fuels using precious metal catalysts

Fuel cell systems with integrated autothermal reforming unit require active and robust catalysts for H2 production. Thus, an experimental screening of catalysts for autothermal reforming of commercial biodiesel fuel was performed. Catalysts consisted of a monolithic cordierite substrate, an oxide support (γ-Al2O3) and Pt, Ru, Ni, PtRh and PtRu as active phase. Experiments were run by widely varying the O2/C and H2O/C molar ratios at different gas hourly space velocities. Fresh and aged catalysts were characterized by temperature programmed methods and thermogravimetry to find correlations with catalytic activity and stability

Routes for deactivation of different autothermal reforming catalysts

Fuel cell systems with integrated autothermal reforming units require active and robust catalysts for H2 production. In pursuit of this, an experimental screening of catalysts utilized in the autothermal reforming of commercial diesel fuels is performed. The catalysts incorporate a monolithic cordierite substrate, an oxide support (γ-Al2O3, La-Al2O3, CeO2, Gd-CeO2, ZrO2, Y-ZrO2) and Rh as the active phase. Experiments are run by widely varying the O2/C and H2O/C molar ratios at different gas hourly space velocities. In most cases, this provokes accelerated catalyst deactivation and permits an informative comparison of the catalysts. Fresh and aged catalysts are characterized by temperature-programmed methods, thermogravimetry and transmission electron microscopy to find correlations with catalytic activity and stability. Using this approach, routes for catalyst deactivation are identified, together with causes of different catalytic activities. Suitable reaction conditions can be derived from our results for the operation of reactors for autothermal reforming at steady-state and under transient reaction conditions, which helps improve the efficiency and the stability of fuel cell systems