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Item type:Publication, Access status: with files , Enzymatic reaction kinetics within pickering emulsions through progress-curve analysisPickering emulsions are attracting increasing attention in biphasic biocatalysis because their particle-stabilized interfaces provide a large contact area between enzymes in the aqueous phase and water-insoluble substrates. Despite growing interest, a comprehensive kinetic framework for enzymatic reactions in Pickering emulsions remains lacking. Here, a progress-curve-based kinetic description of a hydrolysis reaction is presented for the first time and compared with both a single-phase system and a particle-free biphasic system. Transitioning from an aqueous single-phase system to a biphasic system the maximum reaction velocity v<inf>max</inf> increased threefold, while the apparent Michaelis–Menten constant increased by four orders of magnitude, indicating significant interfacial mass-transfer contributions. Notably, Michaelis–Menten kinetics derived from initial rates failed to predict product formation at elevated concentrations due to product inhibition. Direct fitting of integrated rate equations to full progress curves enabled efficient parameter estimation and captured product inhibition while substantially reducing experimental effort compared to conventional initial-rate analysis. Both competitive and non-competitive inhibition models adequately described the data. Comparison with a particle-free biphasic system revealed similar kinetics at high stirring rates; however, under reduced energy input, the Pickering emulsion retained its kinetic parameters and activity, whereas the biphasic system became mass-transfer limited. Overall, this study establishes macrokinetic parameters for Pickering emulsions using progress-curve analysis and demonstrates their advantages under low-stirring conditions, providing a basis for process development.Publicationtype: Journal Article27 8 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Oscillatory motion of trickle-bed reactor can break up liquid channeling and thus increase reaction efficiency(Elsevier, 2026-07-16); ; ; We report that applying an oscillatory pitching motion can substantially increase the reaction efficiency in trickle-bed reactors used for the hydrogenation of liquid organic hydrogen carriers (LOHC). In the present experiments, steady-state reaction was reached 14 times faster and with approx. 25% larger mean efficiency for the pitching reactor compared to the conventional non-moving reactor. Increasing the pitching amplitude from 1° to 4° accelerated the reaction by about 45%. Strong memory effects were observed, with increased reaction efficiency being maintained for 2 h in a non-moving reactor, if the reactor had been operated under oscillatory pitching motion beforehand. Therefore, the present results indicate that substantial efficiency increases do not require continuous oscillations, instead already occasional reactor motions may suffice. We hypothesize that the increase in efficiency is due to breaking-up of liquid channels. Computational Fluid Dynamics (CFD) simulations and cold-flow experiments are reported that strongly support this theory. It is anticipated that the present findings will be applicable to many other types of trickle-bed reactors as well.Publicationtype: Journal Article34 12 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Comprehensive study of 3D liquid flow fields in additively manufactured structures for SMART reactors using large-scale vertical magnetic resonance imaging and computational fluid dynamics(Elsevier, 2026-04-24); ; ; ; Triply Periodic Minimal Surface (TPMS) structures have emerged as a new class of porous materials with variable geometries and favourable transport properties, making them promising for reactor internals in chemical engineering. However, experimental data on internal TPMS flow behaviour are still limited. To address this gap, the flow behaviour in additively manufactured TPMS structures is analysed using three-dimensional Magnetic Resonance Imaging (MRI) velocimetry in a large-bore vertical 3 T MRI system, in cylindrical columns of 38 mm diameter and Reynolds numbers between 50 and 300. Three different TPMS geometries are investigated, and consistency between Computational Fluid Dynamics (CFD) simulations and experimentally measured MRI velocity fields is established through cross-validation. The MRI system provides fully three-dimensional velocity fields with a divergence deviation below 6 %. MRI revealed distinct flow features: the Gyroid TPnS exhibited pronounced channelling, while the Schwarz-Diamond TPSf showed merge-split behaviour, achieving a 46 % increase in lateral mixing compared to the Gyroid TPnS structures. Numerical simulations reproduce the flow features and show agreement with the MRI data. The combined methodology demonstrates the suitability of MRI velocimetry for the experimental validation of CFD simulations and establishes a robust foundation for future studies of heat and mass transfer, as well as reactive flow, in structured reactor systems.Publicationtype: Journal Article68 84 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , 18 12 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Integrating optimal design of experiments and superstructure optimization under uncertainties for the design of membrane processesMembrane processes are attractive options for fluid separations as they enable highly selective separations under mild process conditions. The design and evaluation of membrane processes is however a complex task, due to the large variety of different separation principles and corresponding types of membrane processes, a variety of different membrane materials, and alternative process structures, as well as the limited availability of data and models that is especially a hurdle in the early-stage design of chemical processes. A model- and optimizationbased approach can help to design membrane separation processes systematically but requires the determination of a sufficiently accurate process model that usually requires time-consuming experimental work. In the early stage of process design, there are still many options regarding the process structure and operating parameters, and it is desirable to focus the experimental and modelling efforts only on promising process variants and operating conditions. For this purpose, the current work presents an integrated methodology that enables the application of optimization-based methods in early phase process design applied to a reaction-separation process. The application focusses on the selection and design of the membrane separation as an important aspect of the overall flowsheet. By performing a superstructure optimization in which uncertainties are explicitly considered, a set of promising flowsheet variants can be selected. Instead of a separated design of experiments for the model identification, an integral approach is pursued by selecting the most informative experiments on the basis of the impact of the model uncertainties on the design decisions, in order to quickly determine the most relevant parameters. In the specific case study, the methodology is used for the conceptual design of a membrane process where the membrane is used to separate a co-product from a complex reaction mixture while retaining the expensive homogeneous catalyst. Using the integrated approach only one set of experiments in addition to the initial screening experiments is necessary to identify the optimal flowsheet for the case study.Publicationtype: Journal Article45 13 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Theoretical calculations to identify and design transition metal-based additives for hydrogen storage materials(Elsevier, 2025-08-07); ; ; This study demonstrates the successful design of transition metal boride-based additives to enhance the hydrogen absorption and desorption kinetics of hydrogen storage materials. Density functional theory (DFT) was used to predict a range of boride compounds, with (Ta:Ti)B2 and (Nb:Ti)B2 identified as promising candidates. In particular, the Nb1/2Ti1/2B2 and Ta1/2Ti1/2B2 compositions significantly improve the kinetic properties of the 2LiH-MgB2 (LiMgB) system. When a small amount of these additives is incorporated into LiMgB, its kinetics are improved twice in comparison to the undoped material while maintaining stable reversibility. This substantial improvement is attributed to the presence of Nb1/2Ti1/2B2 and Ta1/2Ti1/2B2 nanoparticles, which act as heterogeneous nucleation sites for MgB2. The study highlights how computational methods can accelerate the design and discovery of optimal additive compositions for hydrogen storage, minimizing the need for extensive experimental testing.Publicationtype: Journal Article13 8 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , La-Ni-H metal hydride system aging effects identificationOne of the most commonly used materials for sorption compression in space applications is based on the La-Ni-H system. The degradation of the material properties and, therefore, the system lifetime is of great importance for the final success of a potential space mission. Considering that satellites and other equipment that have to operate in space are expected to be fully functional for more than 10 years, in this work, an accelerated aging method is designed and carried out to predict the La-Ni-H system properties after 12 years under specific operating conditions. For this test, several specimens of fully hydrogenated LaNi5 are exposed to specific hydrogen pressures (i.e., 20, 35, 58 and 96 bar) at different temperatures (i.e., 50, 90, 130 and 160 °C) for a duration of 90 days. Sievert's type apparatus, synchrotron radiation powder X-ray diffraction (SR-PXD), quasi-elastic neutron scattering (QENS), scanning electron microscopy (SEM), and small-angle X-ray scattering (SAXS) methods are used to investigate the material aging and its impact on the material chemical and microstructural properties.Publicationtype: Journal Article36 18 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Trajectory-based breakup modelling for dense bubbly flowsA new model to predict the breakup of gaseous bubbles in a continuous liquid phase is developed. In the model each bubble is modelled as a spring–damper system, namely a Kelvin–Voigt element, while the outer force is derived by a Lagrangian analysis determining the largest stretching rate of the flow field below. The developed model is based on physical principles and no further arbitrary parameters have to be adjusted. Each bubble is observed on its way through the bubbly flow individually, taking into account its history along its respective path. With the implemented model numerical simulations in a wide range of scales are conducted, ranging from the laboratory scale of a vessel of 3L to the large industrial scale of 15m3. The simplicity of the model allows for a good cost to benefit ratio. In the present work, the achieved results are compared to experimental data obtained from optical measurements in a replica of a 200L aerated stirred tank reactor for various stirrer frequencies.Publicationtype: Journal Article38 64 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Employing a multi-resonance microwave sensor for in-line moisture monitoring of fluidized bed agglomeration(Elsevier, 2024-09-23); ; ; Amorphous substances are relatively common in food industry and their characteristics depend highly on the moisture content. Process parameters are adjusted based on online measurements to control the product quality of the agglomerates. This leads to two major challenges: precise moisture content measurements of amorphous particles at (i) different temperatures and for (ii) a wide moisture content range. In this study two workflows (inline fluidized bed and conditioned fixed bed) calibration of microwave sensors are compared and it is shown that for fluidized beds inline calibration is necessary to achieve accurate moisture measurements. The application of the novel microwave sensor MW 4200 working at resonance frequencies of 2.3 and 5.6 GHz is described. The temperature influence on the measurement is investigated with measurements of a fixed particle bed. Rapid, reliable in-process moisture control at a wide range of moisture contents and temperatures for agglomeration in fluidized beds, with a mean relative accuracy of 82 %, is achieved. This technology improves productivity and precision in industrial operations, minimizes waste and optimizes energy usage.Publicationtype: Journal Article38 69 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Three-dimensional measurement method of binary particle collisions under dry and wet conditionsThe description, calculation and design of solids processes, such as fluidization, pneumatic conveying or mixing, require knowledge of collision dynamics between particles and apparatus walls or interparticle collisions without, but often also with the presence of an additional liquid. For the study of such dry and wet interparticle collisions, an experimental setup is presented that allows the performance of dry or wet free binary collisions of spherical particles down to a minimum diameter of 1 mm. The recording of the particle motions in all three spatial directions is provided by two synchronized highspeed cameras. Methods and algorithms are presented for analyzing the translational and rotational motion in three-dimensional space, as well as for measuring the amount of liquid on the particles in the case of wet collisions. Motion data from dry collisions between equal sized and unequal sized spherical particles are compared with a three-parameter collision model. In addition, a first series of measurements of wetted collisions is used to compare the collision dynamics with dry collisions.Publicationtype: Journal Article28 101