Temporally and spatially resolved operando characterization of hydrogenolysis in wax-filled Fischer-Tropsch pellets using magnetic resonance imaging.

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A transient Fischer-Tropsch synthesis (FTS) can lead to an increase in activity and selectivity with respect to desired liquid products when pure or dilute hydrogen is added periodically. This is attributed to a draining of liquid-filled catalyst pores by the hydrogenolysis reaction, in which long carbon chains are broken up with the addition of hydrogen, allowing them to evaporate more easily and escape from the catalyst bed. Overall, the hydrogenolysis reaction of long-chain alkanes in FTS catalyst pores is still little studied. This is not least due to the fact that classical analytical methods such as gas chromatography or mass spectrometry can only quantify the products in the outlet stream of a reactor. Therefore, this project aims to investigate the mass transfer processes of hydrogenolysis using temporally and spatially resolved operando magnetic resonance imaging (MRI). The non-invasive MRI measurements shall allow a characterization of the mass and phase transformations in the reactor and pellet interior during the entire course of pore depletion. In this way, a fundamental understanding of the dynamic process of pore emptying and hydrogenolysis in wax-filled Fischer-Tropsch catalysts will be systematically developed.