Browsing by Author "Sundmacher K."

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    A method for rough estimation of the catalyst surface area in a fuel cell
    (2009-02-01) Vidaković T.; Christov M.; Sundmacher K.
    A method for a rough estimation of the catalyst surface area in a fuel cell is developed. It is based on the deconvolution of experimental CO oxidation data by use of a mathematical model. The kinetic parameters of the model are determined by fitting the experimental curves. The experimental data are collected at different sweep rates (2-100 mV s-1) and at different temperatures (room -60.0 °C). The model can predict the sweep rate dependence of the CO oxidation onset potential, the peak current, the peak potential and the peak broadness. The model is further used for the prediction of the baseline in the presence of CO and for calculation of the CO charge consumed up to half peak potential. It is obtained that the latter value is constant at different sweep rates and that the baseline deviates from linearity already at low sweep rates (2 mV s-1), but not very significantly (2.0% in comparison to 8.8% at 100 mV s-1, based on calculated CO charge). It is suggested that lower sweep rates should be used for experimental surface area determination. © 2008 The Author(s).
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    Core–shell catalyst pellets for effective reaction heat management
    (2023-02-01) Zimmermann R.T.; Weber S.; Bremer J.; Idakiev V.; Pashminehazar R.; Sheppard T.L.; Mörl L.; Sundmacher K.
    Catalyst research is concerned with synthesizing increasingly active materials, leading to safety issues at reactor scale, unless the reaction heat release is controllable. Computational studies predict that core–shell pellets with catalytically active core and inert shell are beneficial for this purpose, compared to established concepts such as catalyst pellet dilution. At high temperatures, reactant diffusion through the shell becomes rate-determining, resulting in a well-controllable heat release rate, which prevents further temperature increase. Here, industrial catalyst pellets were coated in a fluidized-bed pilot plant, demonstrating large-scale production feasibility. The obtained pellets were characterized via Dynamic Image Analysis, Scanning Electron Microscopy and X-ray Computed Tomography. Conducted CO2 methanation experiments confirm the predicted trends, if the applied shell is fully closed. Furthermore, mathematical and experimental studies demonstrate, that the inert shell shifts selectivity. Based on this work, safer and yet economical reactor operation is anticipated also for other reaction systems.