CO x hydrogenation reactions for hydrocarbon synthesis, such as methane, are becoming more and more important in terms of the energy transition. The formation of the byproduct water leads to a hydrothermal environment, which necessitates stable catalyst materials under harsh reaction conditions. Therefore, novel nanostructured core-shell catalysts are part of scientific discussion, since these materials offer an exceptional resistance against thermal sintering. Here we report on a core-shell catalyst -Co@mSiO 2 -for the hydrogenation of CO/CO 2 mixtures towards methane. CO methanation experiments reveal a rapid temperature-depended deactivation for temperatures above 350°C caused by coking and possible blocking of the pores. In comparison to a Co/mSiO 2 reference catalyst with the same Co particle size a significantly higher methane selectivity was found for CO 2 hydrogenation, which we attribute to the confinement effect of the core-shell structure and therefore a higher probability of CO readsorption. Finally, the simultaneous CO/ CO 2 co-methanation experiments show a high flexibility of the catalyst materials on different gas feed compositions.[a] J. Ilsemann, + Prof. Dr. M. Bäumer

Designing stable materials for processes operating under harsh reaction conditions, like CO hydrogenation, is a challenging topic in catalysis. These may provoke several deactivation mechanisms simultaneously, like thermal sintering, oxidation or poisoning of the active sites. We report HZSM‐5 supported cobalt catalysts, exhibiting cobalt nanoparticles encapsulated inside, or located at the exterior of the ZSM‐5 support. The materials were studied by a combination of ex situ and in situ electron microscopy with respect to the growth of the cobalt particles. After 1200 h time on stream under CO hydrogenation conditions, the spent catalyst showed minimal sintering of encapsulated cobalt particles. In situ environmental TEM experiments under model reduction and CO hydrogenation conditions indicate the presence of cobalt nanoparticles, which appear highly resistant towards sintering even up to 700 °C. These results provide a first indication for the preparation of sinter stable catalysts suitable for operating in harsh reaction environments.

The conversion of synthesis gas to hydrocarbons in the Fischer‐Tropsch (FT) synthesis suffers from a broad product distribution not directly providing high fuel quality. This work, therefore, aims at bifunctional catalysts combining the FT and hydroprocessing (HP) reaction for tailoring the product spectrum. Therefore, we applied a bottom‐up synthesis strategy for bifunctional cobalt/zeolite catalysts and investigated the obtained materials by advanced characterizations such as 3D TEM tomography. Based on the results, descriptors are defined for the acidity and the porosity, which are varied by changing the material preparation parameters. The catalytic properties of the obtained materials are studied in FT experiments at industrially relevant conditions (20 bar, 240 and 260 °C) and are correlated to the material properties by means of the respective descriptors. Therefore, the product distribution was analyzed in detail and distinguished between n‐paraffins and 1‐olefins as typical FT‐products as well as paraffinic and olefinic isomers formed in the HP classified in different fractions. It was found that, apart from the acidity, the pore structure plays a vital role in primary and secondary cracking/isomerization reactions. In addition to that, the particular 3D pore structure and thus the individual transport trajectories of the FT products are strongly affecting the cracking and isomerization probability and consequently the product distribution.

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