The research in the Inorganic Chemistry and Catalysis group involves synthesis, characterization and performance of well-defined solid catalysts and related functional materials for gas storage and photochemical conversion processes. Strongholds are catalyst synthesis techniques and advanced spectroscopy for the study of catalyst materials under working conditions. The fundamental scientific challenge is to establish a relationship between structure and catalytic function at different length scales ranging from the single atomic and molecule level over the micro-, meso- and macroscopic scale up to the level of small reactor set-ups. The group works on various topics of heterogeneous catalysis, including but not limited to the valorization of crude oil, natural gas, biomass and solar light for the production of transportation fuels, base chemicals and materials.
A. Assembly of solid catalysts and functional materials
Based upon concepts of inorganic chemistry, synthesis of solid catalysts involves control of composition, structure and location of active phases in three dimensions in a catalyst particle. The production of solid catalysts resembles the production of a three-dimensional device rather than synthesis of a chemical compound. The materials that are used as building blocks for assembling catalysts include zeolites, mesoporous materials, two-dimensional solid acids and bases, carbon nanofibers, metal organic frameworks as well as many other materials. The applied assembly techniques are homogeneous deposition precipitation, impregnation with chelated metals, ion exchange, hydrothermal crystallization, liquid-phase reduction of metal ions, growth of materials from the gas phase and micelle- and emulsion-templating.
B. Development and application of advanced characterization methods
The group is developing three-dimensional transmission electron microscopy (3D-TEM), in combination with electron energy loss (EELS) detection, which is a crucial characterization tool to assess the process of assembly of solid catalysts and obtaining chemical information about the elemental distribution in a catalyst particle. Furthermore, dealumination processes in zeolites can be characterized in great detail. Other spearheads in the catalysis toolbox are in-situ catalytic studies using advanced microbalance (TEOM) methods, X-ray absorption spectroscopy (EXAFS-XANES), vibrational spectroscopy (IR/Raman) and UV-Vis-NIR spectroscopy. For all in-situ techniques specially designed spectroscopic-reaction cells have been made to ensure that the active catalyst material is studied under relevant catalytic conditions. Several in-situ techniques are also combined in one set-up (UV-Vis/Raman, UV-Vis/Raman/XAFS and SAXS/WAXS/XAFS), giving several advantages over a single spectroscopy approach. More recently, attention is directed toward adding spatial resolution to the above-described in-situ spectroscopic techniques. Examples include transmission X-ray microscopy and tomography making use of soft or hard X-rays, Tip-enhanced Raman spectroscopy, atomic force microscopy combined with surface-enhanced Raman spectroscopy, confocal fluorescence and Raman microscopy, synchrotron-based IR microscopy, UV-Vis micro-spectroscopy and spatially offset Raman spectroscopy. Furthermore, the spectroscopic tools developed can also be applied to probe catalyst synthesis and crystallization processes.
Seven main topics in heterogeneous catalysis are studied in our research group:
- Activation of methane and alkanes.
- Production of base chemicals and fuels from biomass, including the valorization of lignin, cellulose and glycerol.
- Automotive and environmental catalysis, including reactions with NO and CO.
- Fischer-Tropsch catalysis.
- Alcohol-to-hydrocarbon catalysis.
- Photocatalysis, including the solar fuels research.
- Bulk chemicals production, including selective oxidation, hydrogenation and deoxygenation reactions.