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Traceability between samples, devices and data is of great importance to the catalysis community. Adacta is a new research data management (RDM) system designed to create a traceable digital twin of a testing environment, not only storing data, but also creating a readily retrievable time-accurate record of the critical components used to measure catalyst performance. Future developments include extending Adacta to interact with electronic laboratory notebooks and to spawn simulations directly using data and measurements stored in the database.

Data, scripts and generated microkinetic models for the preprint "Detailed microkinetics for the oxidation of exhaust gas emissions through automated mechanism generation" &nbsp

Compared to conventional internal combustion engines, modern hybrid electric vehicles (HEVs) can save fuel under urban driving conditions, which results in lower CO2 emissions. However, frequent stops and restart of the HEV engine go along with periods of low exhaust gas temperatures and therefore cause a decline in pollutant conversion over the three-way catalyst (TWC) system that is typically used for exhaust gas after-treatment [1]. Composition modulation is reported to increase pollutant conversion over the TWC at low temperatures and to be beneficial for cold start performance [2]. In this regard, dithering frequency, amplitude, temperature, and space velocity are the most important parameters influencing the rate enhancement from composition modulation. A synthetic gas bench with fast switching valves is used to conduct a comprehensive parameter study on the influence of dithering parameters on the TWC performance. For this, monolithic catalysts with Pd/Al2O3 and a commercially relevant Ce-based Pd catalyst are prepared by incipient wetness impregnation and subsequent dip coating. The application of a square wave signal to the catalytic converter remains a challenging task due to axial dispersion in the setup periphery. To further examine the phenomena and predict the behaviour of the TWC under periodic conditions, a detailed kinetic model is under development. Literature suggests that the dithering effect can be described by kinetic models with detailed chemistry considering the interaction among species adsorbed on surface sites [3]. Under the assumption of an ideally backmixed reactor, initial modelling results exploiting a detailed microkinetic model for CO oxidation [4] show an increased average CO conversion for all frequencies around the light-off and a decrease for higher temperature (Figure 1). Furthermore, an increase of optimal frequency with increasing temperature and amplitude was observed for constant amplitude and temperature respectively, which is in line with experimental data from literature [2]. Using transient data for model development will provide valuable insights on surface phenomena that are responsible for the dithering effect on three-way catalysts and will ultimately allow for reducing pollutant emissions from HEVs. [1] Y. Huang, N. Surawski, B. Organ, J. Zhou, O. Tang and E. Chan, "Fuel consumption and emission performance under real driving: Comparison between hybrid and conventional vehicles", Sci. Total Environ. 659, 275-282 (2019). [2] P. Silveston, "Automotive exhaust catalysis: Is periodic operation beneficial?", Chem. Eng. Sci. 51, 2419-2426 (1996). [3] P. Kočí, M. Kubíček, M. Marek, "Multifunctional aspects of Three-Way Catalyst: Effects of Complex Washcoat Composition", Chem. Eng. Res. Des. 82, 284-292 (2004). [4] D. Chan, S. Tischer, J. Heck, C. Diehm, O. Deutschmann, "Correlation between catalytic activity and catalytic surface area of a Pt/Al2O3 DOC: An experimental and microkinetic modelling study", Appl. Catal. B 156-157, 153-165 (2014).

Planar laser-induced fluorescence with laser synchronized flow control is employed as a non-invasive in situ technique to investigate a NOₓ storage catalyst, especially to grant a deeper insight into the reaction dynamics and its interaction with mass transfer. In addition to visualizing the spatial and temporal NO evolution over a Pt/BaO/Al₂O₃ catalyst, the spatially resolved NO distribution over a Pt/Al₂O₃ catalyst in the steady-state is measured to understand the oxidation of NO to NO₂ as a precursor step of NOₓ storage. The experimental results are compared with corresponding numerical simulations using transient one- and two-dimensional reactor simulations with detailed surface reaction mechanisms. The thermodynamic equilibrium for NO oxidation over Pt/Al₂O₃ approaches between 623 K and 723 K, as a reduced conversion is observed at a higher temperature. The NOₓ storage on the Pt/BaO/Al₂O₃ catalyst decreases with time, which is partly due to the reduced storage capacity, but also strongly limited by the NO oxidation rate.

At high temperatures, the oxidative coupling of methane (OCM) is an attractive approach for catalytic conversion of methane into value-added chemicals. Experiments with a Pt/Al$_{2}$O$_{3}$-coated catalytic honeycomb monolith were conducted with varying CH$_{4}$/O$_{2}$ ratios, N$_{2}$ dilution at atmospheric pressure, and very short contact times. The reactor was modeled by a multiscale approach using a parabolic two-dimensional flow field description in the monolithic channels coupled with a heat balance of the monolithic structure, and multistep surface reaction mechanisms as well as elementary-step, gas phase reaction mechanisms. The contribution of heterogeneous and homogeneous reactions, both of which are important for the optimization of C2 products, is investigated using a combination of experimental and computational methods. The oxidation of methane, which takes place over the platinum catalyst, causes the adiabatic temperature increase required for the generation of CH$_{3}$ radicals in the gas phase, which are essential for the formation of C2 species. Lower CH$_{4}$/O$_{2}$ ratios result in higher C2 selectivity. However, the presence of OH radicals at high temperatures facilitates subsequent conversion of C2H2 at a CH$_{4}$/O$_{2}$ ratio of 1.4. Thereby, C2 species selectivity of 7% was achieved at CH$_{4}$/O$_{2}$ ratio of 1.6, with 35% N$_{2}$ dilution.

Although compared to conventional diesel and gasoline engines gas engines running on methane-based fuels emit less pollutants, slip of unburnt methane is a hurdle to be overcome. In this regard, particularly noble metal-based catalysts allow for an efficient methane conversion even at low temperatures. Since these catalysts can undergo modifications under the highly dynamic operation [1] affecting activity and stability, the present work aims at creating a multiscale microkinetic model that has a strong link to the structure of the active sites, which change according to the chemical environment they are exposed. A detailed surface reaction mechanism for platinum-catalysed abatement of exhaust gases by Koop et al. [2] was used as a basis for the further development. The model is validated using light-off experiments with a monolithic Pt/Al2O3 catalyst in stoichiometric model gas mixtures. Simulations were carried out using the DETCHEMCHANNEL software [3] and show a remarkable difference, especially regarding the predicted ignition temperature. This different behaviour could be associated to the activation energies of the key reactive steps that need further investigation, i.e. dissociative adsorption of CH4. Along with theoretical considerations, spatially resolved information from experiments are used to improve the model. [1] P. Lott, O. Deutschmann, “Lean-Burn Natural Gas Engines: Challenges and Concepts for an Efficient Exhaust Gas Aftertreatment System” Emiss. Control Sci. Technol. 7, 1-6 (2021). [2] J. Koop, O. Deutschmann, “Detailed surface reaction mechanism for Pt-catalyzed abatement of automotive exhaust gases”, Appl. Cat. B 91, 1 (2009) [3] O. Deutschmann, S. Tischer, C. Correa, D. Chatterjee, S. Kleditzsch, V.M. Janardhanan, N. Mladenov, H. D. Minh, H. Karadeniz, M. Hettel, V. Menon, A. Banerjee, H. Goßler, E. Daymo, DETCHEM Software package, 2.8 ed., www.detchem.com, Karlsruhe 2020.