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In order to increase the typically low equilibrium CO2 conversion to methanol using commercially proven technology, the addition of two intermediate condensation units between reaction steps is evaluated in this work. Detailed process simulations with heat integration and techno-economic analyses of methanol synthesis from green H2 and captured CO2 are presented here, comparing the proposed process with condensation steps with the conventional approach. In the new process, a CO2 single-pass conversion of 53.9% was achieved, which is significantly higher than the conversion of the conventional process (28.5%) and its equilibrium conversion (30.4%). Consequently, the total recycle stream flow was halved, which reduced reactant losses in the purge stream and the compression work of the recycle streams, lowering operating costs by 4.8% (61.2 M€·a−1). In spite of the additional number of heat exchangers and flash drums related to the intermediate condensation units, the fixed investment costs of the improved process decreased by 22.7% (94.5 M€). This was a consequence of the increased reaction rates and lower recycle flows, reducing the required size of the main equipment. Therefore, intermediate condensation steps are beneficial for methanol synthesis from H2/CO2, significantly boosting CO2 single-pass conversion, which consequently reduces both the investment and operating costs.

Correction for ‘Surface reaction kinetics of the methanol synthesis and the water gas shift reaction on Cu/ZnO/Al2O3’ by Bruno Lacerda de Oliveira Campos et al., React. Chem. Eng., 2021, 6, 868–887; DOI: 10.1039/D1RE00040C

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).

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.

Heterogeneous catalysis and anaerobic syngas fermentation represent two different approaches for the conversion of synthesis gas into chemicals and fuels. This review provides a unique comparison of different reaction paths for the fixation of CO$_{2}$, CO and H$_{2}$ into elementary building blocks such as methanol, acetic acid and ethanol. Operating conditions, reactor engineering, influence of gas impurities, yields, conversion efficiencies as well as downstream product recovery are compared. It was found that mass-specific productivity ranges in the same order of magnitude for both technologies, while space-time yield of heterogeneous catalysis is up to three orders of magnitude higher.

Kinetic investigations and model-based optimization of CuO/ZnO/ZrO2 : H-FER 20 catalytic systems for direct DME synthesis from CO2-rich syngas.

A microfluidic reactor enabled continuous co-precipitation synthesis of CuO/ZnO/Al2O3 catalysts for methanol production.

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.

Reaction kinetic modeling, model-based optimization and experimental validation are performed for the direct synthesis of dimethyl ether from CO2 rich synthesis gas. Among these disciplines, experimental methods and models are aligned in a stringent way of action, i.e., the same setup and models are applied throughout the whole contribution. First, a lumped reaction kinetic model from the literature is modified and parametrized to fit a vast array of 240 data points measured in a laboratory fixed bed reactor. The data were acquired using a mechanical mixture of the commercial catalysts CuO/ZnO/Al2O3 and γ-Al2O3. For this setup, a predictive model is derived and applied within dynamic model-based optimization. Here, the single-pass COx conversion serves as objective function while the operating conditions and composition of the mixed catalyst bed are the optimization variables. Finally, the optimization results obtained numerically are validated experimentally verifying the identified performance enhancement qualitatively. The remaining quantitative deviations yield valuable insights into model and methodological weaknesses or inaccuracies, closing the loop between kinetic investigations, model-based optimization and experimental validation.

The one-step synthesis of dimethyl ether over mechanical mixtures of Cu/ZnO/Al

Catalyst systems for the conversion of synthesis gas, which are tolerant to fluctuating CO/CO

Zur Herstellung alternativer Kraftstoffe aus erneuerbaren Rohstoffen steht eine Reihe von Verfahren zur Verfugung und mehrere solcher Kraftstoffe haben sich schon lange am Markt etabliert [1]. Bedeutende Beispiele fur diese Biokraftstoffe der ersten Generation sind Ethanol, das fermentativ aus Starke bzw. Zuckern gewonnen wird [2], Biodiesel, aus der Umesterung von Fettsaureestern mit Methanol (Fatty Acid Methyl Esters, FAME) [3], oder hydrierte Pflanzenole (Hydrogenated Vegetable Oils, HVO) [4]. Durch den Einsatz solcher Kraftstoffe konnen, im Vergleich zu konventionellen Kraftstoffen aus fossilen Quellen, CO2-Emissionen deutlich reduziert werden. Voraussetzung ist eine nachhaltige Produktion uber die ganze Prozesskette hinweg, von den Einsatzstoffen bis hin zum Kraftstoff. Dies impliziert nicht nur die Verwendung erneuerbarer Rohstoffe, die nicht in Konkurrenz zu etablierten Markten, z. B. zum Nahrungsmittelsektor stehen, sondern auch den Einsatz regenerativer Energien.

The reaction pathways leading to coke formation in dry reforming on Ni and Pt-based catalysts were investigated. Using isotope-labeled reactants (i.e., CH 4 + 13 CO 2 ⇌ 2CO + 2H 2 ) showed that initially 13 CO 2 is converted faster than CH 4 and that this higher activity leads to a higher concentration of 13 CO compared with 12 CO in the product stream, suggesting little isotope scrambling among products at this stage. Gasification of carbon deposits was found to be an important pathway enhancing the catalyst stability. Analysis of the pathways leading to carbon deposits suggests that coke is formed predominantly via reverse Boudouard reaction on Ni, while both metals contribute to CH 4 dissociation. The pronounced reversibility of the C H and C O bond formation and cleavage was also shown by the presence of 13 CH 4 formed from 13 CO 2 and 12 CO formed from 12 CH 4 . Numeric calculations complementing the experimental results led to the proposal of a reaction pathway for the surface reactions, accounting for the differences between Ni and Pt.

An experimental and kinetic modeling study on the Ni-catalyzed conversion of methane under oxidative and reforming conditions is presented. The numerical model is based on a surface reaction mechanism consisting of 52 elementary-step like reactions with 14 surface and six gas-phase species. Reactions for the conversion of methane with oxygen, steam, and CO2 as well as methanation, water-gas shift reaction and carbon formation via Boudouard reaction are included. The mechanism is implemented in a one-dimensional flow field description of a fixed bed reactor. The model is evaluated by comparison of numerical simulations with data derived from isothermal experiments in a flow reactor over a powdered nickel-based catalyst using varying inlet gas compositions and operating temperatures. Furthermore, the influence of hydrogen and water as co-feed on methane dry reforming with CO2 is also investigated.

Catalytic dry reforming over a platinum-based catalyst is described experimentally and numerically in a laboratory pilot-plant flow reactor. The results reveal that coking in the upper part of the catalyst bed and at the entrance of the reactor occurs, depending on the composition of the reaction mixture and the respective temperature. To a significant extent, gas-phase reactions play a role as being the cause for the observed coking behavior in the reforming of methane in the presence of carbon dioxide at high temperatures of 1123–1273 K and at 20 bar. Hydrogen addition can inhibit coke formation better than water addition. The reactor is modeled by a one-dimensional description of the reacting field using elementary-step reaction mechanisms of up to 4238 gas-phase reactions among 1034 species and 58 heterogeneous reactions among 8 gas-phase species and 14 surface-adsorbed species. The study leads an optimized positioning of the catalyst in a technical reformer tube.