The direct synthesis of dimethyl ether (DME) from captured CO2 and renewable hydrogen represents a promising pathway to intensify power-to-fuels (PtF) processes and support their large-scale deployment. Building on a previously proposed multi-stage condensation-enhanced carbon utilization (multi-CECU) concept, this work investigates alternative process layouts to improve carbon conversion and energy efficiency. To this end, the original multi-CECU configuration is redesigned to incorporate an absorption-based separation step, replacing sub-zero condensation for DME recovery. The proposed scheme employs methanol both as a reaction intermediate and as a physical sorbent, avoiding the presence of water, which limits CO2 absorption and may cause liquid-liquid phase separation. Technical performance metrics, as well as energy, exergy, techno-economic, and environmental analyses, are used to assess process efficiency, identify optimal heat integration options, and evaluate trade-offs in process intensification. Configurations from one to four reaction stages were compared, with the three-stage layout offering the best compromise between performance and complexity. The selected configuration reaches 98.4% CO2 conversion and 80.5% exergy efficiency, while limiting the increases in external heating and cooling demand by 50.6% and 35.0%, respectively. Under wind-powered electrolysis conditions, the three-stage configuration achieves a DME production cost of 2183 $ t(-1) and a carbon footprint of 0.60 kg CO(2)eq/kg DME, emphasizing the influence of hydrogen supply on economic and environmental performance. When benchmarked against the previous multi-CECU process, the methanol-assisted layout increases DME productivity by 31%, with almost 100% DME yield and selectivity. Overall, the results demonstrate that the multifunctional use of methanol can support process intensification in CO2-based DME synthesis, while low-carbon hydrogen remains decisive for the implementation of economically and environmentally sustainable PtF routes.

Utilization of CO2-containing industrial waste gas emissions as substrates for fermentation with acetogen bacteria is a novel approach. A key requirement for successful process optimization and the development of advanced control strategies is a robust model that can sufficiently predict system responses to varying process conditions. However, few fermentation models have been developed for continuous cell retention or elevated pressure conditions, which are beneficial for integrating gas fermentation with CO2 separation technologies. Therefore, this study adapts a dynamic kinetic model to simulate these conditions to enable model-supported process design with Clostridium ljungdahlii. The literature model was modified by adjusting key equations and re-estimating important kinetic parameters derived from long-term fermentation experiments in a continuous stirred tank reactor. Addition of a carbon dioxide dependency to the hydrogen uptake rate and the acetate to ethanol conversion rate improves the model's accuracy to predict biomass and product concentration trends under high hydrogen substrate gas and moderately increased pressure conditions. Model predictions indicate that maximum ethanol production is linked with biomass growth and increases more than tenfold when the gas residence time is lowered from 1.80 to 0.09 h, and the HQ content in the substrate gas is simultaneously raised from 60 to 80 %, with the remainder being CO. Maximum acetate production is predicted to increase with lower gas residence time, 50 % HQ in the feedstock gas and a shift from CO to a mixture of CO and COQ as a carbon source, with a COQ content of up to 30 %.

In the context of carbon-neutral production, sustainable H2 will become a crucial resource and key element for the transformation of the chemical industry. In this study, the potential of inter-plant H2 networks is demonstrated in the context of methanol and its derivatives. In order to assess the impact of the exploitation of untapped H2-rich waste streams, a process chain for the directly coupled production of CO2-based methanol and formaldehyde was chosen. It is shown that including a H2 loop between a modified silver catalyst processes for formaldehyde production and the feed stream of CO2-based methanol synthesis results in an increase in process performance as well as economic benefits. Directly coupled production leads to utilization ratios of 98% and 99% for CO2 and H2, respectively, while exergy efficiencies are improved by up to 4.5%pt. Economic evaluation shows that improved H2 management not only yields savings in operational expenditures but also lowers capital investments. Over a wide range of assumed H2 prices, small decentralized plants become more competitive when both subprocesses are directly linked. Minimum selling prices between 836 & euro;& sdot;t-1 and 852 & euro;& sdot;t-1 are reached for methanol in integrated plants, corresponding to a decrease of 3 to 13.5%pt when compared to separately operated CO2-based methanol synthesis followed by conventional formaldehyde production.

Due to modern civilization's dependence on finite fossil resources, there is a growing need to implement a circular economy. Catalyzed acetalization reactions could contribute to achieve this goal. In such reactions, a wide variety of aldehydes and alcohols can be converted into acetals, which are known for their good recyclability and non-toxicity. Hence, this work focused on the utilization of acetalization reactions to produce novel and facile degradable building blocks for the chemical industry. The educts employed were the lactic acid derivatives ethyl lactate and butyl lactate, as well as formaldehyde, an important C1 bulk chemical that can potentially be produced from green methanol. The synthesis of functionalized oxymethylene ethers (f-OMEs) using the lactic acid derivatives and formaldehyde was performed for the first time. Based on an initial catalyst screening, the cheap and eco-friendly clay material montmorillonite K10 was employed as the catalyst with the highest selectivity for the desired acetals. The different reactivities of the tested solid acid catalysts are discussed. The conversion values reached up to 60%, and the selectivity for f-OMEs reached up to 70%, depending on the reaction conditions. Catalyst screening and experiments covering the relevant reaction conditions were initially carried out in a batch reactor. Subsequently, the process was successfully implemented in a continuously operating fixed-bed reactor, demonstrating the first steps for scale-up and further selectivity control. After a systematic study of the varying reaction conditions, a reaction network was proposed, and a kinetic model to estimate product distributions was developed. The validation of the model showed that the conversion prediction was mostly within a relative deviation of ±30%. The model exhibited good applicability to batch and fixed-bed reactors, making it a useful tool for process upscaling. A solvent-free and scalable production process for f-OMEs was developed, and the novel substances were characterized.

This work provides a robust database for CO 2 hydrogenation to methanol on a Cu/ZnO/ZrO 2 catalyst and a new 6-parameter kinetic model suitable for application in Power-to-X plant concepts.

This work investigates the impact of higher olefins and typical impurities from a preceding Dimethyl ether-to-Olefins (DtO) process on olefin oligomerization for fuel production. Feed complexity was systematically increased to mimic a DtO product containing lower and higher olefins as well as paraffinic and aromatic components. Higher olefins incorporation enhanced the yield of C13+ hydrocarbons, while impurities reduced it. Kerosene was the dominant product fraction. Temperature was determined to be the governing parameter for promoting C13+ formation and increasing diesel fuel yields, surpassing feed composition effects. Several key properties of the kerosene fraction comply with the ASTM D7566 22a standard for sustainable aviation fuels, whereas some important properties of the diesel fraction meet the ISO 8217 DMB grade for marine diesel fuel.

A new kinetic model for the supercritical water gasification of lignocellulosic biomass is presented. This model accurately simulates the production of gases up to C3 products, and distinguishes condensable products as either aqueous condensate or tars. The reaction orders were treated as hyperparameters, which were tuned via Bayesian optimization. The model was validated against experiments conducted in a continuous laboratory plant operating within a broad range of conditions, including variations in temperature (823-973 K), pressure (240-300 bar), biomass content (1.3-6.6 wt%), K2CO3 addition (0-3750 ppm), and residence time (6-48 s). The proposed model provides insight into the behavior of the reactive system and is useful for applications such as scale-up, process optimization, and process design.

Methanol synthesis’ carbon footprint can be reduced using SynGas feeds from renewable power, but such feeds may strain catalysts due to impurities inherited from its production. Renewable sources include (biogas) pyrolysis, reforming, electrolysis, and shift reactions, whose possible poisons critically affect catalysis for future methanol production. In this work, Cu/ZnO/ZrO2 and Cu/ZnO/ZrO2/SiO2 catalysts were tested under simulated feed conditions containing impurities from hydrogen sources. Since methane impurities and trace oxygen are rarely studied yet highly relevant, solar-powered methane or biogas pyrolysis and alkaline electrolysis were considered as case studies for a wide-rainging, sustainable hydrogen supply. Catalysts were investigated across their lifetime: before and after initial reduction, and during varying times on stream. Results show Cu0 sintering strongly depends on the feed, whereas oxygen-containing feeds promote ZnO crystallization, reducing long-term performance. Incorporating silicon suppresses these effects, enabling more stable catalysts and supporting future use of solar-powered hydrogen feeds.

In order to reduce greenhouse gas emissions in road traffic, different technologies can be considered. Besides electrification, alternative fuels offer the possibility to reduce the climate impact of vehicles using combustion engines. Thereby, they can be used to reduce greenhouse gas emissions in the existing car fleet. By using biomass as raw material, biofuels offer the possibility to create a closed carbon cycle as the plants used for their production absorb CO2 from the atmosphere. In this paper, the potential to produce sustainable, biogenic gasoline with second generation biomass in Europe is evaluated. The considered potentials are only based on second generation biomass that is currently not used for other purposes. The biomass potentials include residual and waste materials, as well as perennial crops cultivated on unused marginal lands. With the considered biomass amounts, the potential gasoline that could be produced is calculated. Therefore, different pathways using ethanol and methanol as an intermediate product are considered. Besides the estimation of the mass potentials, a cost estimation as well as an outlook on future potentials is included in this study.

In this work, the treatment of highly saline wastewaters simulating the effluent of the SCWG process was investigated for the first time using a combined process of electrocoagulation (EC) and electrochemical oxidation (EO) in a single set-up. First, EC with different metal electrodes (e.g. Fe, Al, SS) as anode was applied to synthetic wastewater and the effect of operating parameters, such as current density, electrolysis time and pH, on the process performance was systematically studied. Experimental design, statistical analysis and model optimization were carried out to determine the optimum experimental conditions that maximize the removal of lead ions while minimizing energy consumption. According to the results, EC was very effective in the removal of Pb2+ as 93 % was achieved under specific conditions (10 mA/cm2, 9 min, pH 10), while the energy consumption was relatively low at 0.88 kWh/m3 of treated wastewater. Furthermore, this work provides a performance evaluation of the integrated EC/EO process for the treatment of synthetic or real SCWG brines. EC/EO with two electrode pairs (Fe/Fe and BDD/SS) connected in parallel can achieve complete Pb2+ removal at high flow rates (175 ml/ min), corresponding to short electrolysis times (9 min), when treating a synthetic SCWG brine, and also performs very well under realistic conditions. In the case of real industrial wastewater, high removal rates of organic and inorganic substances; i.e., approx. 60 % PhOH, 40 % TOC, 75 % Pb2+, 75 % Ni2+, can be achieved after 132 min of electrolysis with 64 mA/cm2, which demonstrates the very high efficiency of the EC/EO.

Methanol serves as a starting material for the production of various fuels or fuel components such as methyl tert-butyl ether (MTBE) and biodiesel. In addition, hydrocarbon fuels can be obtained either directly via Methanol-to-Gasoline (MtG) processes or indirectly via Methanol-to-Olefins (MtO) processes followed by flexible conversion of olefins to gasoline, kerosene or diesel fuel. Another option is the synthesis of dimethyl ether (DME) or oxymethylene ethers (OMEs), which exhibit properties similar to conventional diesel fuel. Within this work, the different strategies are described and compared. Provided that methanol is produced from renewable resources, e.g. by hydrogenation of CO2 in a Power-to-X (PtX) process, sustainability of methanol-based process chains can be strongly enhanced. The strategies are, at least partially, on an advanced stage of development and could significantly contribute to future mobility concepts.

A continuous process combining the supercritical water gasification (SCWG) of ethanol with the subsequent steam reforming (SR) of the product gas was investigated. An experimental study was conducted that involved the operating parameters in the SR reactor, the ethanol concentration, and a comparison of two commercial catalysts for SR. With ethanol as a biomass model compound, complete gasification in the SCWG reactor was achieved. Regarding the SR reactor, high pressures, i.e., 20-40 bar, required a temperature of 750 degrees C to achieve methane conversion higher than 90% at a constant gas hourly space velocity of 63500 h- 1. The increase in EtOH concentration significantly decreased the steam/carbon ratio of the SCWG product and increased the content of CH4, C2+hydrocarbons, and CO. This in turn resulted in a decrease in H2 yield in the SR reactor from 98.6% to 58.3%, as the EtOH concentration increased from 5 wt% to 20 wt% at a temperature of 730 degrees C, pressure of 30 bar, and a space velocity of 47877 h- 1. Under atmospheric pressure, both catalysts showed similar CH4 conversion. However, at higher pressures (30-40 bar), the catalyst with the higher Ni loading exhibited greater activity in SR.

Correction for “Sustainable aviation fuel production via the methanol pathway: a technical review” by Ali Elwalily et al., Sustainable Energy Fuels, 2025, https://doi.org/10.1039/D5SE00231A.

Die Erreichung der Klimaneutralität der chemischen Industrie erfordert einen grundlegenden Umbau der Wertschöpfungsketten in 20 Jahren. Um den Kohlenstoffkreislauf zu schließen, werden bekannte Technologien wie Pyrolyse oder Vergasung in neuen Wertschöpfungsketten eingesetzt. Die Endprodukte müssen weiterhin den hohen Qualitätsanforderungen der Abnehmerindustrien genügen. Die Herausforderung besteht darin, Prozesse zu entwickeln, die tolerant gegenüber der Vielzahl der Rohstoffe sind. Für eine erfolgreiche Umsetzung ist gründliches Scale‐up erforderlich, das in der Regel eine Pilotierung einschließt. In der zur Verfügung stehenden Zeit können die Ziele nur erreicht werden, wenn neue Wege der Zusammenarbeit zwischen den verschiedenen Akteuren und Sektoren mit der Wissenschaft, besonders in der Aus‐ und Weiterbildung, beschritten werden.

This work explores the one-step catalytic process of erythritol hydrodeoxygenation (HDO) to 1,3-butadiene over supported Re and mixed Mo-Re oxides on carbon black. Catalyst screening under reducing H2 atmosphere was performed in liquid phase under batch conditions. Mixed Mo-Re catalysts show the best HDO performance, as they are active towards C-O scission with mild hydrogenation activity, contributing to preservation of the C--C bond of 1,3-butadiene. The effect of reaction parameters was exploited over the promising 5Mo-10Re/CB catalyst. 3-butene-1,2-diol is the main intermediate to 1,3-butadiene formed at short reaction times while longer reaction times lead to butenes. Maximum 1,3-butadiene selectivity 93 % was achieved at 51 % erythritol conversion at 140 degrees C, 60 bar and 5 h reaction time. XPS measurements of fresh and used materials indicated that the upper surface layer consists of fully and partially reduced Mo and Re species, which according to CH3OHTPSR host both redox and acid sites.

The kinetics of CO2 hydrogenation to methanol over a self-developed Cu/ZnO/ZrO2 (CZZ) catalyst was studied in a wide range of process conditions. Experiments were performed at industrially relevant pressures (30-60 bar) and temperatures (190-250 degrees C), as well as H2 to CO2 ratios between 1 and 6, addressing the use of hydrogen from renewable energy sources and the use of CO2 as a C1 raw material in Power-to-X technologies. The CZZ catalyst has shown improved performance and higher stability in CO2 hydrogenation to methanol in comparison to other Cu/ZnO-based catalysts. A mathematical description of the kinetics is crucial to enable model-based design for the industrial implementation of this catalyst. Therefore, a lumped 6-parameter kinetic model was developed to fit the experimental data, resulting in one of the predictive models with the broadest validity range (experimental database of 500 points) for the CZZ system. This new kinetic model is compared to state-of-the-art literature models with more parameters, and our model performs equally well or even better in terms of sensitivity to process parameters and extrapolability.

A novel reactor concept for supercritical water gasification was developed where cold biomass is mixed with supercritical water for heating. This approach enhanced the gasification efficiency and reduced solid deposition. Following proof of concept over 100 h, a parametric study was conducted, varying biomass type, dry matter content (1.3-8.2 wt %), temperature (550-700 °C), pressure (240-300 bar), potassium addition (0-3750 ppm), and residence time (0-42 s). Results showed that biomass type, pressure, and potassium addition had a minimal impact on the process. Higher biomass concentration reduced carbon efficiency (CE) but maintained levels around 80%. Increasing the residence time at the reaction temperature significantly improved CE up to 8 s at 650 °C (τ = 0 s, CE = 27%; τ = 8 s, CE = 72%), beyond which gains plateaued. Temperature strongly influenced CE (T = 550 °C, CE = 58%; T = 700 °C, CE = 91%) and gas composition, with higher temperatures reducing organic carbon and tar formation but increasing methane (T = 550 °C, 9.5 vol % CH4; T = 700 °C, 15.9 vol % CH4) and C2+ (T = 550 °C, 2.3 vol % C2+; T = 700 °C, 5.1 vol % C2+) contents. Deviations in gas composition from equilibrium calculations, conducted with ASPEN HYSYS, suggest insufficient steam reforming, potentially addressable with a nickel catalyst. An empirical multilinear regression model was developed, accurately predicting outcomes for studied biomasses and reducing experimental effort for process optimization. Overall, the study demonstrates the reactor concept's superior performance and provides a strong foundation for further developing and optimizing supercritical water gasification processes that could potentially be applied to other feedstocks.

Die Förderung unseres Nachwuchses ist uns ein zentrales Anliegen, deshalb ist es besonders erfreulich, dass NaWuReT, der Nachwuchs in der Reaktionstechnik, sich mit einem Beitrag zu den Karrieremöglichkeiten junger Reaktionstechnikerinnen und Reaktionstechniker beteiligt. Vom 6.–8. Mai fand das Jahrestreffen Reaktionstechnik 2024 in Würzburg statt. Die Veranstaltung wurde gemeinsam mit der Fachgruppe "Elektrochemische Prozesse" durchgeführt. Diese sehr erfolgreiche Veranstaltung zeigte eindrucksvoll, dass es nicht nur sehr viele Möglichkeiten für eine Zusammenarbeit sowohl bei methodischen Ansätzen als auch bei Anwendungen gibt, sondern dass generell beide Communities sehr stark an einer intensiven Zusammenarbeit interessiert sind. Während des Treffens hat sich die Fachsektion "Chemische Reaktionstechnik" neu konstituiert. Der Vorstand der Fachsektion besteht aus bis zu 30 Personen, darunter Vertreterinnen und Vertreter der drei beteiligten Fachgruppen "Elektrochemische Prozesse", "Polymere" sowie "Kinetik und Reaktionsmechanismen" und den beiden Vorsitzenden von NaWuReT. 22 Vertreterinnen und Vertreter der Reaktionstechnik wurden auf der Mitgliederversammlung gewählt. Im Vorstand der Fachsektion sind nunmehr Universitäten, Hochschulen für angewandte Wissenschaften und außeruniversitäre Einrichtungen ebenso vertreten wie große und kleine Unternehmen. Zum Vorsitzenden der Fachsektion wählte der Vorstand Prof. Hannsjörg Freund von der TU Dortmund, zu seinen Stellvertretern Dr. Kai Ehrhardt von der BASF und Prof. Jörg Sauer vom KIT. Die Fachsektion ist der chemischen Reaktionstechnik in ihrer ganzen Breite gewidmet. Die nächsten geplanten Veranstaltungen werden wir nutzen, um die Zusammenarbeit der Fachgruppen und der zugehörigen Communities innerhalb der Fachsektion zu fördern und daraus Ideen, Themen und Initiativen für die Zusammenarbeit über die Fachsektion hinaus innerhalb der DECHEMA und der VDI-GVC zu entwickeln. Als ein Beispiel für diese Zusammenarbeit wird die Entwicklung von methodischen Ansätzen, Verfahren und Materialien für die Elektrifizierung der chemischen Produktion ein Schwerpunkt der Arbeit der Fachsektion in den kommenden Jahren sein. Die Elektrifizierung ist ein interessanter Ansatz, um nachhaltigere Prozesse zu entwickeln und damit CO2-Emissionen zu reduzieren. Durch den Einsatz erneuerbarer Energien und die Nutzung von CO2 als Rohstoff kann der Kohlenstoffkreislauf geschlossen werden. Mit der Elektrifizierung und damit der Substitution von Dampf aus Kraft-Wärme-Kopplung als Wärmeträger bzw. der dedizierten Erzeugung von Dampf durch direkte elektrische Beheizung, Wärmepumpen und elektrischer Kessel wird sich der Produktionsverbund chemischer Prozesse verändern müssen. Nebenströme können dann nicht mehr im heutigen Umfang anlagen- oder standortintern energetisch genutzt werden, dabei muss der Einsatz von Strom möglichst intelligent erfolgen. Die neu formierte Fachsektion "Chemische Reaktionstechnik" kann hier wichtige Beiträge zur Entwicklung und Umsetzung interessanter Elektrifizierungsansätze auf dem Weg zu effizienten, stabilen und damit wirtschaftlichen Prozessen leisten. Hannsjörg Freund Jörg Sauer Kai Ehrhardt