Our Research focuses on the development of new catalysts within biomass conversion, fine chemistry and exhaust gas catalysis. More than 60% of all chemical processes are based on catalytic processes among which heterogeneous catalysts play and will play the main role in bulk chemicals, also during the present change from fossile to renewable energies. Thereby three subject are of paramount importance:
(I) Design: synthesis of new nanomaterials
(II) Test & process: efficient catalyst testing
(III) Understanding: fundamental understanding using physico-chemical analysis and in situ spectroscopy.
This combined approach is used for a rational design and improvement of catalytic processes.
The Catalyst and Nanomaterial Preparation
Nanomaterials: New preparation Techniques and High Throughput Testing
Novel preparation methods to new nanomaterials, efficient catalytic tests and proper catalyst characterization are our basis for the design of new catalysts. Presently applied synthesis strategies are: flame synthesis, preparation of size-controlled particles, hydrothermal synthesis and porous materials including metal-organic frameworks (MOFs).
The Target Reactions
Green Chemistry for Fine Chemicals: Use of Carbon Dioxide as Solvent and Reactant
Supercritical fluids offer intesting properties for reaction design: tunability of density, gas-like transport properties and more liquid-like solvent properties. Carbon dioxide is particularly intesting since the pressure and temperature required are moderate (Tc=31°C, pC=73.75 bar). Both hydrogenation and oxidation reactions are of interest. Moreover, the use of carbon dioxide as a safer and cheaper C1-building block than carbon monoxide or phosgene is a great chalenge in "green chemistry". Here, carbon dioxide can act both as reactant and solvent and thus leads to a solvent-less process.
Biomass is the presently the only renewable carbon source and is therefore important for the future to produce fuels and organic key chemicals. We focus on the conversion of biomass platform molecules, e.g. fructose/glucose or glycerol as well as upgrading of pyrolysis oil. Important reactions are dehydration, hydrogenation and in general deoxygenation reactions. Efficient catalyst screening together with rational design of alloy catalysts and reaction engineering aspects appear important to tackle this subject.
More stringent laws for exhaust gases require the development of a new and better generation of exhaust gas catalysts. For example: The new generation of lean-burn engines, which offer the possibility for lower fuel consumption, the classical 3-way catalyst cannot be applied (NOx is not removed effectively). A new catalyst concept is needed. One possibility is the class of NOx-storage catalysts. It stores NOx under the usual lean fuel conditions, but can be rapidly regenerated during a puls of fuel-rich conditions. We are presently building up an exhaust gas catalysis centre with Prof. Olaf Deutschmann and Prof. Sven Kureti.
The Fundamental Understanding
In Situ Characterization of Heterogeneous Catalysts
X-ray diffraction, extended X-ray absorption spectroscopy, Raman and IR spectroscopy and are - among other techniques - versatile and powerful tools for the investigation of heterogeneous catalysts under reaction conditions. The techniques can be applied in gaseous phase but also in liquid phase and at high pressure.
Opportunities of X-ray absorption spectroscopy
A traditionally strong focus is laid in our group on X-ray absorption spectroscopy. The advantage: amorphous and crystalline materials can be investigated. The present focus is on the following topics
Time resolved studies in the second scale
Combination of EXAFS with other spectroscopic techniques
Operando studies in gas phase, liquid phase and elevated pressure.
Several Research Initiatives have recently been established with third party funding. They will be described here in very near future (in preparation).
Materials in Action (Mat-Act, BMBF)
Operando studies on a microscale (Micro, BMBF)
Energy-related catalysis (Helmholtzkolleg)
Catalysis for sustainable energies (CASE, DTU)
Exploring new catalytic reactions in supercritical carbon dioxide as innovative and non-flammable reaction medium (FTP)
Preparation of nanparticles for catalysis by flame spray pyrolysis and hydrothermal synthesis (DSF)