Climate change represents an existential, global threat to humanity, yet its delocalized nature complicates climate action. Here, the authors propose retrofitting air conditioning units as ...integrated, scalable, and renewable-powered devices capable of decentralized CO
conversion and energy democratization.
In this study, we investigated the catalytic properties of mono- and bimetallic palladium (Pd) and platinum (Pt) nanoparticles deposited via supercritical fluid reactive deposition (SFRD) on titanium ...dioxide (TiO2) powder. Transmission electron microscopy analyses verified that SFRD experiments performed at 353 K and 15.6 MPa enabled the deposition of uniform mono- and bimetallic nanoparticles smaller than 3 nm on TiO2. Electron-dispersive X-ray spectroscopy demonstrated the formation of alloy-type structures for the bimetallic PdPt nanoparticles. H2O2 is an excellent oxidizing reagent for the production of fine and bulk chemicals. However, until today, the design and preparation of catalysts with high H2O2 selectivity and productivity remain a great challenge. The focus of this study was on answering the questions of (a) whether the catalysts produced are suitable for the direct synthesis of hydrogen peroxide (H2O2) in the liquid phase and (b) how the metal type affects the catalytic properties. It was found that the metal type (Pd or Pt) influenced the catalytic performance strongly; the mean productivity of the mono- and bimetallic catalysts decreased in the following order: Pd > PdPt > Pt. Furthermore, all catalysts prepared by SFRD showed a significantly higher mean productivity compared to the catalyst prepared by incipient wetness impregnation.
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•Different methods for leak detection are presented and used dependent on defect density.•Laser scan strategy for thin-walled overhangs is developed.•It is possible to print gas-tight ...30° overhangs below dWall < 300 µm, despite the low fault tolerance of this measure.•Design and repeatability are critical.•Case study shows the practical application of the findings for a distillation device.
The industrial adoption of additive manufacturing (AM) technologies increased due to more applications and use cases demonstrating significant functional benefits. Additive manufacturing of thin-walled gas-tight structures with complex shapes can fulfil requirements for a wide range of applications, such as process equipment for the chemical industry. The requirement to be gas-tight makes the manufacturing process very fault-sensitive as even a single open pore in the submicron range can lead to an impermissible leak of hazardous gases. Further, it has always been a challenge to make thin walls using Laser Powder Bed Fusion of Metals (PBF-LB/M). We explore the key design limit of inclined overhanging gas-tight thin walls made from 316l. A double pass scan strategy is presented to realize these structures along with guidelines to be followed when attempting to print these structures. The paper reports the common failure modes where leaks occur and lessons learned to successful design and printing of gas-tight walls. The results show that fabrication of gas-tight walls is feasible even for a 30° inclination angle to the horizontal and wall thicknesses in the range of 200–300 µm. A case study shows the successful the application of the findings to the production of modular distillation devices.
Sustainable aviation fuels (SAF) are needed in large quantities to reduce the negative impact of flying on the climate. So-called power-to-liquid (PtL) plants can produce SAF from renewable ...electricity, water, and carbon dioxide. Reactors for these processes that are suitable for flexible operation are difficult to manufacture. Metal 3D printing, also known as additive manufacturing (AM), enables the fabrication of process equipment, such as chemical reactors, with highly optimized functions. In this publication, we present an AM reactor design and conduct experiments for Fischer-Tropsch synthesis (FTS) under challenging conditions. The design includes heating, cooling, and sensing, among others, and can be easily fabricated without welding. We confirm that our reactor has excellent temperature control and high productivity of FTS products up to 800 kgC5+ mcat−3 h−1 (mass flow rate of hydrocarbons, liquid or solid at ambient conditions, per catalyst volume). The typical space-time yield for conventional multi-tubular Fischer-Tropsch reactors is ~100 kgC5+ mcat−3 h−1. The increased productivity is achieved by designing reactor structures in which the channels for catalyst and cooling/heating fluid are in the millimeter range. With the effective control of heat release, we observe neither the formation of hot spots nor catalyst deactivation.
A microstructured cover flow mixer equipped with two cyclone structures was used for stable continuous hydrothermal synthesis of ZnO nanoparticles from Zn(NO3)2 and NaOH aqueous solutions in ...supercritical water. The effects of the NaOH/Zn(NO3)2 ratio, Zn(NO3)2 molality, and flow rate on Zn conversion, crystal structure, particle size, particle morphology, and mixer clogging were examined. The advantages of this mixer were identified by comparing with the results obtained using the same chemical conditions with tee-type, cross-type, and central collision-type mixers.
Membrane reactors applied to catalytic reactions are currently being studied in many places world-wide. Significant developments in membrane science and the vision of process intensification by ...multifunctional reactors have stimulated a lot of academic and industrial research, which is impressively demonstrated by more than 100 scientific papers on catalytic membrane reactors being published per year. Palladium as a noble metal with exceptional hydrogen permeation properties and, at the same time, broad applicability as a catalyst, first of all for hydrogenation, is part of many of these developments.
This paper discusses two different membrane reactor concepts which both rely on supported palladium, on the one hand as a permselective membrane material, and on the other hand as base component of a membrane-type hydrogenation catalyst. Dense palladium composite membranes can be used for hydrogen separation from packed-bed catalysts in gas-phase hydrocarbon dehydrogenation reactions. Mesoporous membranes containing dispersed bimetallic Pd/X-clusters can be employed as so-called
catalytic diffusers for liquid-phase hydrogenation, e.g. of nitrate and nitrite in water. The principles of both concepts are introduced, recently obtained experimental data are evaluated in connection with literature results, and the perspectives for further development are highlighted.
Determination of local heat transfer coefficient at the interface of channel wall and fluid was the main goal of this experimental study in microchannel flow boiling domain. Flow boiling heat ...transfer to DI-water in a single microchannel with a rectangular cross section was experimentally investigated. The rectangular cross section dimensions of the experimented microchannel were 1050 μm × 500 μm and 1500 μm × 500 μm. Experiments under conditions of boiling were performed in a test setup, which allows the optical and local impedance measurements of the fluids by mass fluxes of 22.1 kg·m−2·s−1 to 118.8 kg·m−2·s−1 and heat fluxes in the range of 14.7 kW·m−2 to 116.54 kW·m−2. The effect of the mass flux, heat flux, and flow pattern on flow boiling local heat transfer coefficient and pressure drop were investigated. Experimental data compared to existing correlations indicated no single correlation of good predictive value. This was concluded to be the case due to the instability of flow conditions on one hand and the variation of the flow regimes over the experimental conditions on the other hand. The results from the local impedance measurements in correlation to the optical measurements shows the flow regime variation at the experimental conditions. From these measurements, useful parameters for use in models on boiling like the 3-zone model were shown. It was shown that the sensing method can shed a precise light on unknown features locally in slug flow such as residence time of each phases, bubble frequency, and duty cycle.
Equipment integrity is an essential aspect of process engineering. Design guidelines facilitate the design and production of safe-to-operate and economic devices. Thin-walled, slit-shaped modules ...form a subgroup of process engineering devices made via additive manufacturing (AM). Being subject to internal pressure, they have lacked design guidelines until now. We derived a user-centered calculation model for such modules with regular internal structures. It was validated with Finite Element Analysis (FEA) and practical pressure tests for which the modules were manufactured additively. The performance of the calculation could be confirmed, and a design graph was derived. Slit-shaped modules with appropriate internal structures can withstand high pressure at a minimum wall thickness, and they are efficiently fabricated. These structures, being pins, fins, lattice, or heat transfer enhancing fluid-guiding elements (FGEs), occupied approximately 10% of the modules’ internal volume.
Immobilized multi-enzyme cascades are increasingly used in microfluidic devices. In particular, their application in continuous flow reactors shows great potential, utilizing the benefits of ...reusability and control of the reaction conditions. However, capitalizing on this potential is challenging and requires detailed knowledge of the investigated system. Here, we show the application of computational methods for optimization with multi-level reactor design (MLRD) methodology based on the underlying physical and chemical processes. We optimize a stereoselective reduction of a diketone catalyzed by ketoreductase (Gre2) and Nicotinamidadenindinukleotidphosphat (NADPH) cofactor regeneration with glucose dehydrogenase (GDH). Both enzymes are separately immobilized on magnetic beads forming a packed bed within the microreactor. We derive optimal reactor feed concentrations and enzyme ratios for enhanced performance and a basic economic model in order to maximize the techno-economic performance (TEP) for the first reduction of 5-nitrononane-2,8-dione.
The adsorption of gases CO2, H2O, methanol, and dimethyl ether (DME) in zeolite H-ZSM-5 in the temperature range of 50–150 °C and pressure range of 0–18 bar has been investigated using a ...high-temperature, high-frequency oscillating microbalance (langatate crystal microbalance, LCM). The determined adsorption data are needed to validate a detailed simulation model, which is meant to assist in the optimization of the preparation of bifunctional core–shell catalysts for one-stage DME synthesis from syngas. Compared to the conventional quartz crystal microbalance (QCM) which is limited to temperatures below 80 °C, LCM can be used at higher temperatures, i.e., at or close to the reaction temperature of one-stage DME synthesis (200–300 °C), owing to the absence of crystalline-phase transitions up to its melting point (1470 °C). Zeolite H-ZSM-5 crystallites have been synthesized on the langatate crystal by steam-assisted crystallization (SAC). The loaded H-ZSM-5 (Si/Al molar ratio 100) on the langatate crystal has been confirmed and characterized with X-ray diffraction (XRD), wavelength-dispersive X-ray spectroscopy (WDX), and scanning electron microscopy (SEM). The adsorption experiments showed that the adsorption of CO2, methanol, and DME in H-ZSM-5 is fitted well by the single site Langmuir model, while the dual-site Langmuir model is needed for the adsorption of H2O in H-ZSM-5. The determined adsorption parameters, i.e., adsorption capacities, adsorption enthalpies, and adsorption entropies, compare well to literature data.
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