30 Jahre Institut für Heiße Chemie im Kernforschungszentrum Karlsruhe [30 Years Institute for Hot Chemistry at the Nuclear Research Center Karlsruhe]

Das Institut für Heiße Chemie IHCh wurde 1959 gegründet, um die Entwicklung der Technologie zur Wiederaufarbeitung von Kernbrennstoffen zu unterstützen. Aufbauend auf dem sog. PUREX-Prozess wurden mögliche Varianten zur Abtrennung von noch nutzbarem Spaltmaterial durch Kombination verschiedenster Extraktions- und Redoxverfahren vom Labor- bis zum Pilotmaßstab entwickelt, bis dieser mit nur noch einem Extraktionszyklus auskam. Mit dem Ende der nuklearen Reaktorforschung wurden als Institut für Technische Chemie neue Themen aus der Umwelt- und Energieforschung aufgegriffen. In dieser Zeit wurde im Rahmen der internationalen Kollaboration GALLEX ein radiochemischer Sonnenneutrino-Detektor gebaut und erfolgreich betrieben

Recent Progress in Direct DME Synthesis and Potential of Bifunctional Catalysts

PtX technologies are one major building block of the future energy system based on renewables sources. Dimethyl ether (DME) is an important PtX product that can be used as intermediate the production of CO$_{2}$-neutral base chemicals. New applications lead to an increase of the global production and the optimization of the process efficiency, especially when considering decentralized synthesis. This review article puts some spotlights on recent developments in methanol and the direct DME synthesis with a special focus on the modeling and bifunctional catalyst. This study is expected to provide a foundation for future works in the field of catalysis research based on catalysts design and kinetic modeling

Kinetics of the Direct DME Synthesis: State of the Art and Comprehensive Comparison of Semi-Mechanistic, Data-Based and Hybrid Modeling Approaches

Hybrid kinetic models represent a promising alternative to describe and evaluate the effect of multiple variables in the performance of complex chemical processes, since they combine system knowledge and extrapolability of the (semi-)mechanistic models in a wide range of reaction conditions with the adaptability and fast convergence of data-based approaches (e.g., artificial neural networks—ANNs). For the first time, a hybrid kinetic model for the direct DME synthesis was developed consisting of a reactor model, i.e., balance equations, and an ANN for the reaction kinetics. The accuracy, computational time, interpolation and extrapolation ability of the new hybrid model were compared to those of a lumped and a data-based model with the same validity range, using both simulations and experiments. The convergence of parameter estimation and simulations with the hybrid model is much faster than with the lumped model, and the predictions show a greater degree of accuracy within the models’ validity range. A satisfactory dimension and range extrapolation was reached when the extrapolated variable was included in the knowledge module of the model. This feature is particularly dependent on the network architecture and phenomena covered by the underlying model, and less on the experimental conditions evaluated during model development

Kinetics of the direct DME synthesis from CO2_{2} rich syngas under variation of the CZA-to-γ-Al2_{2}O3_{3} ratio of a mixed catalyst bed

The one-step synthesis of dimethyl ether over mechanical mixtures of Cu/ZnO/Al$_{2}$O$_{3}$ (CZA) and γ-Al$_{2}$O$_{3}$ was studied in a wide range of process conditions. Experiments were performed at an industrially relevant pressure of 50 bar varying the carbon oxide ratio in the feed (CO$_{2}$ in COx from 20 to 80%), temperature (503–533 K), space-time (240–400 kg$_{cat}$s m$_{gas}$$^{-3}$), and the CZA-to-γ-Al$_{2}$O$_{3}$ weight ratio (from 1 to 5). Factors favoring the DME production in the investigated range of conditions are an elevated temperature, a low CO$_{2}$ content in the feed, and a CZA-to-γ-Al$_{2}$O$_{3}$ weight ratio of 2. A lumped kinetic model was parameterized to fit the experimental data, resulting in one of the predictive models with the broadest range of validity in the open literature for the CZA/γ-Al$_{2}$O$_{3}$ system

Sector coupling established by the technology partnership reFuels - rethinking fuels

The use of regeneratively produced fuels (reFuels) is a promising path towards CO2-neutral mobility, alongside other measures such as the expansion of electric mobility. These fuels can be produced from carbon-containing residues from agriculture and forestry, from industrial and municipal waste, as well as from CO2 in combination with hydrogen obtained by electrolysis of water. These fuels together form the reFuels class. In order to assess the potential of reFuels, a holistic evaluation is necessary, including the determination of efficiency potentials for their manufacture and application. Under the patronage of the state of Baden-Württemberg the technology partnership reFuels was initiated, in which companies of the energy and mineral oil industry, the automotive industry and the supplier industry together with the Karlsruhe Institute of Technology (KIT) are investigating efficiency potentials for the production and application of reFuels. Pilot facilities already in operation will be used to produce fuel components in a sufficient scale. The systemic and socioeconomic aspects for the production and application of reFuels will be considered and put in an dialogue with civil society actors to consider the open communication into society.. Within the reFuels project started in 2019 for 2 years duration the consortium of industrial companies and KIT including companies as energy providers, fuels synthesis to suppliers, system developers to engine and car manufacturers. The Project shall achieve the following goals: 1. Provision of selected regenerative fuels ("reFuels") and holistic evaluation of the processes for their production including the determination of efficiency potentials for production and application 2. Evaluation of reFuels key properties, demonstration in the application and evaluation of the application properties 3. Involvement of civil society actors and communication in society

Surface reaction kinetics of the methanol synthesis and the water gas shift reaction on Cu/ZnO/Al₂O₃

A three-site mean-field extended microkinetic model was developed based on ab initio DFT calculations from the literature, in order to simulate the conversion of syngas (H2/CO/CO2) to methanol on Cu (211) and Cu/Zn (211). The reaction network consists of 25 reversible reactions, including CO and CO2 hydrogenation to methanol and the water-gas shift reaction. Catalyst structural changes are also considered in the model. Experiments were performed in a plug flow reactor on Cu/ZnO/Al2O3 at various gas hourly space velocities (24–40 L h−1 gcat−1), temperatures (210–260 °C), pressures (40–60 bar), hydrogen feed concentrations (35–60% v/v), CO feed concentrations (3–30% v/v), and CO2 feed concentrations (0–20% v/v). These experiments, together with experimental data from the literature, were used for a broad validation of the model (a total of 690 points), which adequately reproduced the measurements. A degree of rate control analysis showed that the hydrogenation of formic acid is the major rate controlling step, and formate is the most sensitive surface species. The developed model contributes to the understanding of the reaction kinetics, and should be applicable for industrial processes (e.g. scale-up and optimization)

Direct DME synthesis on CZZ/H-FER from variable CO2_{2}/CO syngas feeds

Catalyst systems for the conversion of synthesis gas, which are tolerant to fluctuating CO/CO$_{2}$ gas compositions, have great potential for process-technical applications, related to the expected changes in the supply of synthesis gas. Copper-based catalysts usually used in the synthesis of methanol play an important role in this context. We investigated the productivity characteristics for their application in direct dimethyl ether (DME) synthesis as a function of the CO$_{2}$/CO$_{x}$ ratio over the complete range from 0 to 1. For this purpose, we compared an industrial Cu/ZnO/Al$_{2}$O$_{3}$ methanol catalyst with a self-developed Cu/ZnO/ZrO$_{2}$ catalyst prepared by a continuous coprecipitation approach. For DME synthesis, catalysts were combined with two commercial dehydration catalysts, H-FER 20 and γ-Al$_{2}$O$_{3}$, respectively. Using a standard testing procedure, we determined the productivity characteristics in a temperature range between 483 K and 523 K in a fixed bed reactor. The combination of Cu/ZnO/ZrO$_{2}$ and H-FER 20 provided the highest DME productivity with up to 1017 g$_{DME}$ (kg$_{Cu}$ h)$^{-1}$ at 523 K, 50 bar and 36 000 ml$_{N}$ (g h)$^{-1}$ and achieved DME productivities higher than 689 g$_{DME}$ (kg$_{Cu}$ h)$^{-1}$ at all investigated CO$_{2}$/CO$_{x}$ ratios under the mentioned conditions. With the use of Cu/ZnO/ZrO$_{2}$//H-FER 20 a promising operating range between CO$_{2}$/CO$_{x}$ 0.47 and 0.8 was found where CO as well as CO$_{2}$ can be converted with high DME selectivity. First results on the long-term stability of the system Cu/ZnO/ZrO$_{2}$//H-FER 20 showed an overall reduction of 27.0% over 545 h time on stream and 14.6% between 200 h and 545 h under variable feed conditions with a consistently high DME selectivity