Development of solid acid catalysts

Project description

Acid catalysts play a central role in the conversion of biogenic raw materials into valuable products. Solid acids such as zeolites and ion exchange resins are often used because they allow easy recovery and reuse of the catalyst. However, homogeneous catalysts such as heteropolyacids have a higher acid strength and can be molecularly adapted to the requirements of the respective reaction. Despite these advantages, the direct industrial use of homogeneous acid catalysts in the production of bulk chemicals has so far been limited due to economic constraints and the difficulty of catalyst recovery.

Although we have already demonstrated stable immobilization of heteropolyacids on solid supports,^[1] there is currently no commercial support material available that is suitable for large-scale catalyst synthesis.

In this context, N-doped carbon materials represent a promising solution as they are easily accessible and can prevent leaching of the active phase in non-noble metal catalysis^[2].

In the project, N-doped carbons are produced either by post-synthetic doping or by direct incorporation of nitrogen during the production of activated carbon. The resulting materials are then loaded with commercial heteropolyacids and hydrogenation-active metals. The catalysts are then tested over several reaction cycles under aqueous reductive conditions to assess their activity and long-term stability.

Representative applications of these bifunctional acid/base hydrogenation catalysts include the one-step hydrolytic hydrogenation of xylan to xylitol and the selective dehydroxylation of internal hydroxyl groups, for example in the conversion of glycerol to 1,3-propanediol and of 1,2,6-hexanetriol to 1,6-hexanediol.

References

1. L. Hombach, F. Müller, F. Varamo, C. O. Ogolla, R. Hoffmann, J. Frohne, H. Schönherr, R. Palkovits, B. Butz, A. K. Beine:

   "Heteropolyacids and Ruthenium on Covalent Triazine Frameworks - a Bifunctional, Recyclable Catalyst for Bio-Based Tandem Systems"

   Catalysis Science & Technology 2025, 15, 1439

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2. F. Varamo, A. K. Beine:

   "N-Containing Carbon Materials in Metal-Free and Non-Noble Metal Liquid Phase Heterogenous Catalysis"

   Advanced Synthesis & Catalysis 2025, e70134