Material Synthesis© ACA
Modern exhaust gas catalytic converters usually consist of a non-porous ceramic monolith and a porous washcoat as a carrier for the catalytically active metal species (i.e. platinum). Enhancing the performance of the catalytic system is enabled by different analysis methods and their correlation. These contain the optimization of carrier structures and their pore design by simulation.
Furthermore, the configuration of the catalytic active component is specifically adjusted by controlling particle sizes and morphology as well as their surface properties to improve the catalytic activity. Another aim consists in the substitution respectively reduction of the proportion of noble metal in the catalytic active component accompanied at constant or improved activity, i.e. by use of bimetal systems with specifically adjustable metal-metal-interactions, transition metal carbides, mixed oxides or metal-oxide-hybrid structures.
Standard analytics at ACA comprises the analysis of elemental composition, distribution, crystal structure, specific surface, porosity and pore size distribution. Besides, tests concerning coating structures and to determine active centers are conducted.
The material samples produced at ACA are in shape of granules or mini catalysts tested under "real" conditions in the laboratory gas bench. The test bench is coupled with a complex multi-component analysis, which captures with a high time resolution the gas composition before and after the catalyst samples. With the help of fast clocked admission valves it is possible to depict transient motor management strategies to realistically characterize material development. Thereby, data material is collected and will be provided for the application at the engine test bed.
Furthermore, the material developed at ACA is analyzed for their electrical properties. This goes within a parallel testing in an in situ impedance spectroscopy/ diffuse reflectance infrared fourier transform infrared spectroscopy (DRIFTS) measuring station to correlate electrical properties with molecular information.
Additionally, the sample material is compared with commercially available material in the material data base. Thus, we can generate a verifiable transparent ranking that allows a final evaluation of the catalysts developed at ACA.
Experimental work for production of new types of catalytic systems are supported by theoretical approaches of the adsorbate-surface-interactions with calculations of the electronic structure.
These simulations should yield detailed understanding about the most important mechanisms. For a quantitative description of non-linear surface processes the quantum chemical simulation is linked to kinetic and Metropolis Monte Carlo simulations. Recently, a universal descriptor approach was developed to determine with simple DFT calculations the catalytic behavior of CeO2 doped with transition metals. Similar approaches shall be developed for others of the above-mentioned materials and shall be applied by an optimal design in combination with experiments for identifying new material for the catalysis. This work is done in direct collaboration with the experiments for the material synthesis at IAC and ITMC.
Additionally, simulations of the engine operation including the entire exhaust gas aftertreatment system are conducted to enhance boundary conditions of catalyst development for the expected exhaust gas temperatures, volume flow and compositions. For this purpose, we have access to a special software, which was created and optimized over years in proprietary development at TME. This software is able to rapidly determine the influence of new engine concepts as well as changed catalyst position and size with the help of parameter variation.
Material Transport© WSA
In the first phase of the Project House a new measurement technique is developed for in situ characterization of material transport in the boundary layer between the free gas flow and the catalytic surface. Thereto, a FTIR spectrometer is placed at an overcurrent reactor. This method enables the species measurement without disturbing the boundary layer, which is crucial for material transport.
At the beginning the requirements for material, surfaces and sample production are defined, so that the measuring technique can be calibrated for the expected materials and the test set-up can appropriately be constructed. The collected empirical data is finally used to develop a concept for a test bed.
The definition of the related boundary conditions ensures that the measurements, the numerical analysis of the material transport and a possible model development are well synchronized. Based on the measuring technique at ACA and on the planned and designed test bed data will be measured in future projects. This should serve the validation of detailed numerical simulations.
An efficient and economical exhaust gas aftertreatment concept can not only be realized by optimizing the used components. To gain the optimal performance aftertreatment processes are analyzed at ACA up to vehicle integration level.
Based on experimental and simulative findings the catalysts are specifically synchronized and new approaches for the system configuration are developed. Modern testing facilities for engine, powertrain and vehicle enable the validation of the system structure as well as the adjustment of the engine operating parameters. Highly transient engine conditions will be an important influence factor of future aftertreatment concepts. The pointedly usage and influence of these processes already take place at ACA at laboratory level and can further be followed up into the vehicle.