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Georg Rudelstorfer, Maximilian Neubauer, Matthäus Siebenhofer, Susanne Lux and Annika Grafschafter
Isolation of carboxylic acids from dilute aqueous effluents can be achieved by the combination of liquid-phase catalyzed reaction with liquid-liquid extraction. Exemplarily the heterogeneously catalyzed esterification of acetic acid with methanol, accelerated with a cation-exchange resin and simultaneous transfer of the product methyl acetate into the solvent ShellSol T, was successfully performed in a Taylor-Couette disc contactor (TCDC) in batch operation mode. Stable three-phase flow (liquid-liquid-solid) was confirmed in lab scale. The conversion of acetic acid in a TCDC operated in batch mode compares well with conversion in a batch reactor.
ChemieIngenieurTechnik, Volume94, Issue5, Special Issue: Chemische Reaktionstechnik, May 2022, 671-680
One of the flagship projects of the "Digital TU Graz" is the participatory innovation program "Digital TU Graz Marketplace", which transfers methodical and technical innovations in the form of funded pilot projects to university practice in the long term.
Sascha Kleiber, Michael Haring and Thomas Wallek are one of the winning teams in the Digital TU Graz Marketplace 2022 competition. Beginning April 1, 2022, the three will implement a digital innovation project in teaching aimed at new methods of imparting knowledge in courses:
For further information, including a pitch video, click here <https://my.ltb.io/www/#/ > or follow the QR-Code:
The 8th Regional Symposium on Electrochemistry for Southeast Europe will be organized by us at TU Graz from 11-15 July 2022.
ESAT 2022. We are proud to announce that the 32nd European Symposium on Applied Thermodynamics will be held in Graz from 17-20 July 2022.
Summer School on Fuel Cells & Hydrogen. We are co-organizers of the next summer school at Yokohama National University, Japan from 29 Aug – 3 Sept 2022. Join us!
S. Abrari, V. Daneshvari‑Esfahlan, M. G. Hosseini, R. Mahmoodi, V. Hacker
In the present work, Ni@Pd core–shell nanoparticles are successfully deposited on multi-walled carbon nanotubes as support and investigated their performance towards formate oxidation reaction. The structural features of the catalyst are characterized by scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. According to the results, the size of the Ni@Pd core–shell nanoparticles is 5–10 nm and the nanoparticles are uniformly deposited on the multi-walled carbon nanotubes. The performance of the synthesized electrocatalysts for the formate oxidation reaction is investigated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy as well as their comparison with Ni–Pd alloy nanoparticles on multi-walled carbon nanotubes. The results indicated that the Ni@Pd core–shell nanoparticles on multi-walled carbon nanotubes show higher electrocatalytic activity and stability than the Ni–Pd alloy nanoparticles on multi-walled carbon nanotubes against formate electrooxidation reaction. Moreover, the efficiency of synthesized anodic electrocatalysts is evaluated in a direct sodium formate-hydrogen peroxide fuel cell by employing a Pt/carbon as cathode (0.5 mg cm−2) and Ni@Pd core–shell nanoparticles on multi-walled carbon nanotubes as anode (1 mg cm−2). A maximum power density of 45.56 mW cm−2 at 25 °C is achieved for this measurement.
Journal of Applied Electrochemistry, Springer 2022
P.Demmelmayer, M. Kienberger
Fermentation of residues or side streams can be used to produce valuable products, such as carboxylic acids. Reactive solvent extraction is widely studied as isolation method for lactic acid from fermentation broths. Here, we investigate the reactive extraction of lactic acid from sweet sorghum silage press juice using different extractants, modifiers, and diluents. Besides a high extraction efficiency, a low crud formation with this highly complex raw material is targeted. Depending on the solvent phase composition, an extraction efficiency of up to 41.1 % was reached using DOA/ALIQ:1–octanol:n–nonane. The crud layer was highly influenced by the applied diluent and amounted to 2.6–42.3 vol% of the total mixture volume. The back-extraction experiments showed, that up to 98.2 % of lactic acid were recovered. Summarizing, the results show that reactive solvent extraction of lactic acid is applicable to highly complex process streams, and crud formation can be reduced by adjusting the solvent phase composition.
Separation and Purification Technology, Volume 282, Part B, 1 February 2022, 120090
Viktor Hacker & D.J. Liu
On 10/11 November 2021, the Topical Meeting on Potential for cost reduction and performance improvement for PEMFC at component and system level took place at Graz University of Technology. Due to the prevailing Corona situation at the time, the event was geared largely towards online participation, but (additional) personal attendance was also possible. A video stream of the event and interactive discussion of questions, both via chat and directly, allowed for a lively meeting in the auditorium of Graz University of Technology and online.
M.G. Hosseini, V. Daneshvari-Esfahlan, S. Wolf & V. Hacker
Nitrogen-doped reduced graphene oxide-supported palladium–cobalt nanoparticles (PdCo NPs/NrGO NSs) are synthesized and used as a high-performance and low-cost anodic catalyst for direct hydrazine–hydrogen peroxide fuel cells. The SEM and TEM images of PdCo NPs/NrGO NSs show the uniform metal nanoparticle distribution on the NrGO NSs. The reduction of the oxygen functional groups and the doping of the nitrogen atoms in the GO framework are confirmed by FT-IR and XRD spectroscopic studies. The Pd catalysts modified by Co exhibit a higher catalytic activity, lower onset potential, better durability, and lower impedance values than unmodified Pd catalysts for the electro-oxidation of hydrazine. The kinetic studies show a first-order reaction with an activation energy of 12.51 kJ mol-1. A direct hydrazine–hydrogen peroxide fuel cell with PdCo NPs/NrGO NSs as anode and Pt/C as cathode provides an open circuit voltage of 1.76 V and a maximum power density of 148.58 mW cm-2 at 60 °C, indicating that the PdCo NPs/NrGO NSs are an economical, high performance and reliable anode catalyst for the direct hydrazine–hydrogen peroxide fuel cell.
RSC Adv., 2021, 11, 39223
Astrid Loder, Matthäus Siebenhofer, Andreas Böhm, Susanne Lux
Direct reduction of mineral iron carbonate with hydrogen is a high-potential candidate for carbon dioxide emission reduction in the iron and steel industry. This novel technology provides a new route for ‘clean’ iron production. For economic implementation, a sufficient supply of hydrogen is crucial. Up to now only highly pure hydrogen sources were used for the direct reduction. On the way to a sustainable, completely hydrogen-based iron production, low-grade hydrogen sources need to be considered. The effect of the hydrogen concentration and the impact of matrix constituents such as methane and carbon dioxide in the hydrogen source on the direct reduction of mineral iron carbonate with hydrogen at 873 K were investigated in this project. It was shown that complete iron carbonate conversion is possible at a metallization degree of 78 wt% with hydrogen concentrations as low as 55 vol%. Carbon dioxide in the feed gas (27–63 vol%) favors magnetite formation instead. Hydrogen is also consumed by the reverse water gas shift reaction in the formation of carbon monoxide. Methane in the feed gas (15–80 vol%) does not have a negative impact on the composition of the solid product. These results suggest that methane-rich hydrogen sources (e.g., coke oven gas) are viable options for direct iron carbonate reduction opening up a novel pathway for clean iron production from mineral iron carbonate with low-grade hydrogen sources.
Cleaner Engineering and Technology, Volume 5, December 2021
M. Bodner, Ž. Penga, W. Ladreiter, M. Heidinger, & V. Hacker
Fuel starvation is a major cause of anode corrosion in low temperature polymer electrolyte fuel cells. The fuel cell start-up is a critical step, as hydrogen may not yet be evenly distributed in the active area, leading to local starvation. The present work investigates the hydrogen distribution and risk for starvation during start-up and after nitrogen purge by extending an existing computational fluid dynamic model to capture transient behavior. The results of the numerical model are compared with detailed experimental analysis on a 25 cm2 triple serpentine flow field with good agreement in all aspects and a required time step size of 1 s. This is two to three orders of magnitude larger than the time steps used by other works, resulting in reasonably quick calculation times (e.g., 3 min calculation time for 1 s of experimental testing time using a 2 million element mesh).
Energies 2021, 14(23), 7929
G. Hosseini, V. Daneshvariesfahlan, H. Aghajani, S. Wolf & V. Hacker
In the present work, nitrogen-doped reduced graphene oxide-supported (NrGO) bimetallic Pd–Ni nanoparticles (NPs), fabricated by means of the electrochemical reduction method, are investigated as an anode electrocatalyst in direct hydrazine–hydrogen peroxide fuel cells (DHzHPFCs). The surface and structural characterization of the synthesized catalyst affirm the uniform deposition of NPs on the distorted NrGO. The electrochemical studies indicate that the hydrazine oxidation current density on Pd–Ni/NrGO is 1.81 times higher than that of Pd/NrGO. The onset potential of hydrazine oxidation on the bimetallic catalyst is also slightly more negative, i.e., the catalyst activity and stability are improved by Ni incorporation into the Pd network. Moreover, the Pd–Ni/NrGO catalyst has a large electrochemical surface area, a low activation energy value and a low resistance of charge transfer. Finally, a systematic investigation of DHzHPFC with Pd–Ni/NrGO as an anode and Pt/C as a cathode is performed; the open circuit voltage of 1.80 V and a supreme power density of 216.71 mW cm−2 is obtained for the synthesized catalyst at 60 °C. These results show that the Pd–Ni/NrGO nanocatalyst has great potential to serve as an effective and stable catalyst with low Pd content for application in DHzHPFCs.
Catalysts. 2021, 11, 22 p., 1372
Paul Demmelmayer and Marlene Kienberger
Fermentation of residues or side streams can be used to produce valuable products, such as carboxylic acids. Reactive solvent extraction is widely studied as isolation method for lactic acid from fermentation broths. Here, we investigate the reactive extraction of lactic acid from sweet sorghum silage press juice using different extractants, modifiers, and diluents. Besides a high extraction efficiency, a low crud formation with this highly complex raw material is targeted. Depending on the solvent phase composition, an extraction efficiency of up to 41.1 % was reached using DOA/ALIQ:1–octanol:n–nonane. The crud layer was highly influenced by the applied diluent and amounted to 2.6-42.3 vol% of the total mixture volume. The back-extraction experiments showed, that up to 98.2 % of lactic acid were recovered. Summarizing, the results show that reactive solvent extraction of lactic acid is applicable to highly complex process streams, and crud formation can be reduced by adjusting the solvent phase composition.
Separation and Purification Technology 2021, 120090
Sebastian Bock, Bernd Stoppacher, Karin Malli, Michael Lammer and Viktor Hacker
Decentralized hydrogen production is a promising pathway to use locally available, renewable resources and establish regional value chains. Besides the successful demonstration of hydrogen production from real producer biogas in at Ökostrom Mureck a techno-economic study was conducted to proof the economic viability of the technology.
The present study proofs the Reformer Steam Iron Process, conceptualized in the research group of Prof. Viktor Hacker at CEET, as an efficient and economically favorable option for decentralized high-purity hydrogen production.
The cold gas efficiency (CGE) for hydrogen production from biogas was estimated as 60–78%. An external recirculation was found to increase the CGE by +44%rel. for the predominant Fe–FeO conversion step. A pinch analysis proofed the full thermal integration of the process independent of the varied process parameters.
The economic feasibility was ascertained based on a case scenario for hydrogen production at a 3 MWth biogas plant. The system efficiency for hydrogen production was estimated at 62.5%, uncoupling the excess heat for district heating increased the overall system efficiency up to 84%. The costs for hydrogen production from biogas were estimated at 2.27 € kgH2.
Energy Conversion and Management 2021, 250, 114801
doi.org/10.1016/j.enconman.2021.114801 (Open Access)
Maximilian Grandi, Kurt Mayer, Matija Gatalo, Gregor Kapun, Francisco Ruiz-Zepeda, Bernhard Marius, Miran Gaberšček and Viktor Hacker
Electrochemical impedance spectroscopy is an important tool for fuel-cell analysis and monitoring. This study focuses on the low-AC frequencies (2–0.1 Hz) to show that the thickness of the catalyst layer significantly influences the overall resistance of the cell. By combining known models, a new equivalent circuit model was generated. The new model is able to simulate the impedance signal in the complete frequency spectrum of 105–10−2 Hz, usually used in experimental work on polymer electrolyte fuel cells (PEMFCs). The model was compared with experimental data and to an older model from the literature for verification. The electrochemical impedance spectra recorded on different MEAs with cathode catalyst layer thicknesses of approx. 5 and 12 µm show the appearance of a third semicircle in the low-frequency region that scales with current density. It has been shown that the ohmic resistance contribution (Rmt) of this third semicircle increases with the catalyst layer’s thickness. Furthermore, the electrolyte resistance is shown to decrease with increasing catalyst-layer thickness. The cause of this phenomenon was identified to be increased water retention by thicker catalyst layers.
Energies 2021, 14(21), 7299
Austrian researchers have demonstrated a chemical looping system can be retrofitted into biogas plants. It is said the new tech can produce high-purity hydrogen for fuel cells on an industrial scale. The scientists concerned said their system could produce hydrogen, on a decentralized basis, for €5/kg.
Verfahrenstechnik. Wasserstoff gilt als Energieträger der Zukunft. Ein Forschungsteam der Technischen Universität (TU) Graz fand heraus, wie man ihn umweltfreundlich aus Bioabfällen herstellen kann.
Die Presse, Wissen und Innovation
Fabian Zapf, Thomas Wallek
Instance selection aims at selecting model training data in a way that the performance of the trained models is maximized. In the context of modeling chemical processes by artificial neural networks, it can serve as an essential preprocessing step since measurement data of such processes are commonly highly clustered and thus far away from being ideally normally distributed. In this paper, four filter methods from literature and a newly proposed method for data selection are tested and combined with a convex hull data selection algorithm, which results in ten different selection approaches. These approaches are applied to five selected datasets by training feed-forward artificial neural networks with the produced split datasets. The final mean model deviation is used to quantify the algorithms’ performance and their standard deviation to provide information about their reproducibility. It is found that the convex hull extended algorithms self-organizing maps based stratified sampling with a proportional allocation rule and the newly proposed self-information-based subset selection perform best for real-world chemical engineering data.
Applied Soft Computing, Volume 113, Part B, December 2021, 107938
Wissenschaft gestaltet Zukunft. Am jährlichen interdisziplinären Wissenschaftstag TU Graz – Science for Future zeigen Forschende der TU Graz, wie sie über alle Disziplinen hinweg den gesellschaftlichen Herausforderungen mit innovativen Technologien begegnen und unsere Zukunft mitgestalten.
Viktor Hacker, Mobilität & Produktion: Volle Energie für den Klimaschutz
9:30 Begrüßung und Eröffnung des Wissenschaftstages der TU Graz
Horst Bischof, Vizerektor für Forschung der TU Graz
Harald Kainz, Rektor der TU Graz
Grußworte Karin Schaupp, Vorsitzende des Universitätsrates der TU Graz
Grußworte Peter Piffl-Percevic, in Vertretung des Bürgermeisters der Stadt Graz
Grußworte Barbara Eibinger-Miedl, Landesrätin für Wissenschaft und Forschung
Gast-Keynote Claudia KEMFERT:
Corona und Klimaneutralität: Wege aus der Krise
TU Graz Keynote Martin WILKENING: Designstrategien für neue Materialien zur Energiespeicherung
TU Graz Keynote Viktor HACKER:
Mobilität & Produktion: Volle Energie für den Klimaschutz
17:00 Podiumsdiskussion "Science for Future? Kann die Wissenschaft das Klima retten?"
Preisverleihung "TU Graz SciPix - Forschung im Fokus", Forschungsfoto-Wettbewerb der TU Graz
Ab 18:00 Abendessen und Networking
Moderation: Marlene Nowotny (Ö1 Wissenschaftsredaktion)
The Summer School on Polymer Electrolyte Fuel Cells and Hydrogen was successfully organised and held for the thirteenth time (Final Report).
Die Sommerakademie über Polymerelektrolytbrennstoffzellen und Wasserstoff wurde zum dreizehnten Mal erfolgreich organisiert und durchgeführt (Abschlussbericht)
Study Abroad Video by Dr. Barbara Lorber, Faculty of Technical Chemistry, Chemical and Process Engineering, Biotechnology.
Andreas Toth, Matthäus Siebenhofer, Susanne Lux
Emulsion-enhanced biphasic esterification has proven to be applicable for carboxylic acid recovery from dilute aqueous process streams. The carboxylic acid is esterified with 1-octanol in an emulsified regime with 4-dodecylbenzenesulfonic acid (4-DBSA) or Ni(DBSA)2 as catalyst. After phase separation, the laden solvent phase must be regenerated. This study presents a regeneration concept based on reactive distillation with transesterification of the octyl ester-laden solvent with methanol. The regenerated solvent is reused in the extraction step.
Chemie Ingenieur Technik (2021) 93,10, 1493-1501
Maitz, Silvia and Kienberger, Marlene
Black liquor (BL) from the kraft process is considered a promising feedstock for several biorefinery scenarios. Besides lignin and carboxylic acids, this liquor also contains hemicelluloses and their degradation products. A simple and reliable detection of those is of importance for further processing of the liquor. The present paper presents a thorough investigation of quantitative analysis of carbohydrates, by performing acid hydrolysis experiments with a concentrated BL sample of 44% total dry solids. The hydrolysates were then analysed for the four monosaccharides arabinose, xylose, galactose and glucose, by high performance ion chromatography (HPIC) with pulsed amperometric detection. The amount of sulphuric acid needed for complete hydrolysis of the carbohydrates was determined in the range of 3.5–5 mol kg−1 of BL. A lower acid concentration led to insufficient liberation of galactose and glucose, while higher acid concentrations led to degradation of arabinose and xylose. The carbohydrate degradation was also investigated over time for different dilutions and hydrolysis temperatures. These experiments confirmed that the hexoses require considerably harsher conditions for complete liberation compared to xylose and arabinose. The use of internal recovery standards (RSs) was tested; the highest recoveries were obtained by direct spiking of the samples with the RS prior to hydrolysis.
Holzforschung, vol. , no. , 2021, pp. 000010151520210047
Surrogate models of chemical processes can substitute rigorous models that are computationally expensive or of limited stability by simplified and typically solely data-driven models. In this work, gray-box surrogate models of classical process engineering unit operations comprising flash, distillation and compression units are developed to provide accurate models that allow for fast and stable predictions in view of later optimization of coupled models. The gray-box surrogates are first tested as individual models and then applied to model the cracked-gas compression of an ethylene plant, including a recycle stream. The process streams are hydrocarbon mixtures containing 50 components, which typically leads to significant convergence issues with rigorous approaches. A concluding comparison of the proposed surrogate models’ accuracies proves their robustness and computational efficiency and highlights the advantages of the proposed modeling methodology that complements and extends simple but physically meaningful white-box models with black-box models from the field of machine learning.
Computers & Chemical Engineering, Volume 155, 107510
Bernd Stoppacher, Sebastian Bock, Karin Malli, Michael Lammer, Viktor Hacker
Chemical looping with iron-based oxygen carriers enables the production of hydrogen from various fossil and biogenic primary energy sources. In applications with real producer gases, such as biogas or gasified biomass, hydrogen sulfide represents one of the most challenging contaminants. The impact of H2S on the reactivity of a Fe2O3/Al2O3 oxygen carrier material in chemical looping hydrogen production was investigated in the present work. Possible deactivation mechanisms of sulfur are discussed in detail on the basis of thermodynamic data. An experimental study in a fixed-bed reactor system gave experimental evidence on the fate of sulfur in chemical looping hydrogen systems. A profound interpretation was achieved through the fulfillment of the overall sulfur mass balance within a mean deviation of 3.7%. Quantitative investigations showed that hydrogen consumption in the reduction phase decreased by 12% at 100 ppm H2S in the feed gas.
Figure 1: Temperature profile (black), concentration for H2S (red) and SO2 (blue) of a redox cycle with reduction (grey background), steam oxidation (yellow) and air oxidation (blue background).
Fuel 307 (2022) 121677
Zukunftsfonds Steiermark: Approved projects in the 13th call for proposals of the Future Fund of the Styrian Provincial Government and the City of Graz (Climate Protection Fund). Short presentations of the projects in the video (FC-Core 08:16 min).
Georg Rudelstorfer, Matthäus Siebenhofer and Annika Grafschafter
The design of mass transfer systems based on data on the mass transfer of single droplets is still a major challenge, although it has been intensively discussed for decades. Modelling extraction with chemical reaction causes additional difficulties. Single droplet mass transfer of acetic acid from an aqueous carrier into a triisooctylamine-based solvent modified with the Lewis acid modifier isodecanol and the diluent Shellsol T was studied with the result that mass transfer of acetic acid into triisooctylamine-based solvent droplets is limited by diffusion of the loaded solvent from the interface into the droplet bulk phase.
Chemie Ingenieur Technik
For his research achievements in the development of a new sustainable process for hydrogen production at CEET, Dr Sebastian Bock was selected from 70 submissions and received the sponsorship award for special social relevance from the Forum Technik und Gesellschaft.
The transformation to a sustainable, decarbonised energy system is more topical than ever in social, scientific and political terms. The application-oriented provision of renewable energies is essential for their efficient use. In Austria in particular, there is enormous potential for the use of sustainable bioenergy.
In Sebastian Bock's dissertation, a concept for decentralised hydrogen production developed and patented at TU Graz was transferred to an industrial process. The innovative chemical looping process for hydrogen production was developed specifically for the requirements of small and medium-sized plants. The demonstration on an industrially relevant scale took place in what is currently the world's largest 10 kW fixed-bed test plant in Graz.
The added social value of the work lies in particular in the transfer of a scientific concept into an industrial process for hydrogen supply. Such decentralised concepts increase energy self-sufficiency and the added value of rural areas. In the medium and long term, local anchoring also increases awareness of sustainable mobility and the acceptance of hydrogen technologies.
Für seine Forschungsleistungen zur Entwicklung eines neuen nachhaltigen Verfahrens zur Wasserstofferzeugung am CEET wurde Dr. Sebastian Bock aus 70 Einreichungen ausgewählt und erhielt den Förderpreis für besondere gesellschaftliche Relevanz vom Forum Technik und Gesellschaft.
Die Transformation zu einem nachhaltigen, dekarbonisierten Energiesystem ist in gesellschaftlicher, wissenschaftlicher und politischer Hinsicht aktueller denn je. Die anwendungsorientierte Bereitstellung von erneuerbaren Energien ist essentiell für deren effiziente Nutzung. Gerade in Österreich gibt es ein enormes Potenzial für die Nutzung nachhaltiger Bioenergie.
In der Dissertation von Sebastian Bock wurde ein an der TU Graz entwickeltes und patentiertes Konzept zur dezentralen Wasserstofferzeugung in einen industriellen Prozess überführt. Das innovative Chemical-Looping-Verfahren zur Wasserstofferzeugung wurde speziell für die Anforderungen von kleinen und mittleren Anlagen entwickelt. Die Demonstration im industriell relevanten Maßstab erfolgte in der derzeit weltweit größten 10-kW-Festbettversuchsanlage in Graz.
Der gesellschaftliche Mehrwert der Arbeit liegt insbesondere in der Überführung eines wissenschaftlichen Konzepts in ein industrielles Verfahren zur Wasserstoffversorgung. Solche dezentralen Konzepte erhöhen die Energieautarkie und die Wertschöpfung des ländlichen Raums. Mittel- und langfristig erhöht die lokale Verankerung auch das Bewusstsein für nachhaltige Mobilität und die Akzeptanz von Wasserstofftechnologien.
Andraž Kravos, Ambrož Kregar, Kurt Mayer, Viktor Hacker and Tomaž Katrašnik
The detrimental effects of the catalyst degradation on the overall envisaged lifetime of low-temperature proton-exchange membrane fuel cells (LT-PEMFCs) represent a significant challenge towards further lowering platinum loadings and simultaneously achieving a long cycle life. The elaborated physically based modeling of the degradation processes is thus an invaluable step in elucidating causal interaction between fuel cell design, its operating conditions, and degradation phenomena. This analysis enables optimal reduction of the set of calibration parameters, which results in the speed up of both the calibration process and the general simulation time while retaining the full extrapolation capabilities of the framework.
Energies 2021, 14(14), 4380
Sascha Kleiber, Moritz Pallua, Matthäus Siebenhofer, Susanne Lux
Methanol synthesis from carbon dioxide (CO2) may contribute to carbon capture and utilization, energy fluctuation control and the availability of CO2-neutral fuels. However, methanol synthesis is challenging due to the stringent thermodynamics. Several catalysts mainly based on the carrier material Al2O3 have been investigated. Few results on MgO as carrier material have been published. The focus of this study is the carrier material MgO. The caustic properties of MgO depend on the caustification/sintering temperature. This paper presents the first results of the activity of a Cu/MgO catalyst for the low calcining temperature of 823 K. For the chosen calcining conditions, MgO is highly active with respect to its CO2 adsorption capacity. The Cu/MgO catalyst showed good catalytic activity in CO2 hydrogenation with a high selectivity for methanol. In repeated cycles of reactant consumption and product condensation followed by reactant re-dosing, an overall relative conversion of CO2 of 76% and an overall selectivity for methanol of 59% was obtained. The maximum selectivity for methanol in a single cycle was 88%.
Energies 2021, 14(14), 4319;
Kocher, K., Kolar, S., Ladreiter, W. & Hacker, V.
Vehicle applications require efficient cold start capability and durability of polymer electrolyte membrane fuel cells. In this study, we propose different self-cold-start strategies including flushing the PEMFC at shutdown and using galvanostatic operation at start-up. The cold-start properties from -5 °C of a single cell are investigated experimentally in situ at laboratory scale. The amount of cumulative charge transfer density, corresponding to the amount of product water, is used as an index to quantify the cold start capability.
Gas purging prior to freezing facilitates cold start of the PEMFC, although the improvement is relatively small compared to other methods, such as gradually increasing the current during start-up. Microscopic examinations of the membrane electrode assembly (MEA) after a cold start failure are be carried out to determine the material degradation due to ice formation.
Fuel Cells, Wiley, online early view, article FUCE1748
In the FWF Decision Board meeting no. 84 of 21. June 2021, another research project was approved for CEET!
Advanced ceramic supported oxygen carriers – ACCEPTOR
Chemical Looping is one of the most promising technologies for CO2 sequestration. The Reformer Steam Iron Cycle, first published in 2003, is based on a fixed-bed chemical looping scheme with the scope of hydrogen production from locally available renewable resources. This allows the production of pre-pressurized (100 bar), high purity (99.999%) hydrogen for fuel cells in decentralized systems. The key constraint to its widespread use is the low material stability, which is particularly essential in fixed-bed reactors. The main challenge is the maintenance of the chemical and structural integrity of the oxygen carrier over several thousand reduction and oxidation cycles, as it is impossible to replace the material during ongoing operation in fixed beds.
Fortschrittliche keramische Sauerstoffträgermaterialien - ACCEPTOR
Chemical Looping ist eine der vielversprechendsten Technologien zur CO2-Sequestrierung. Der Reformer-Eisen-Dampf-Prozess, der erstmals 2003 veröffentlicht wurde, basiert auf einem Festbett-Chemical-Looping-Schema mit der Möglichkeit der Wasserstoffproduktion aus lokal verfügbaren erneuerbaren Ressourcen. Dies ermöglicht die Produktion von komprimierten (100 bar), hochreinem (99,999%) Wasserstoff für Brennstoffzellen in dezentralen Systemen. Die größte Herausforderung ist die Aufrechterhaltung der chemischen und strukturellen Integrität des Sauerstoffträgers über mehrere tausend Reduktions- und Oxidationszyklen, da ein Austausch des Materials im laufenden Betrieb in Festbetten nicht möglich ist.
Mihanović, L., Penga, Ž., Xing, L. & Hacker, V.
A numerical study compares the currently most common flow field configurations, porous, biporous, porous with baffles, fine mesh Toyota 3D and traditional rectangular flow field. Operation at high current densities is considered to clarify the effects of the flow field designs on overall heat transfer and liquid water removal. A comprehensive, multiphase, non-isothermal 3D fluid dynamics model is developed based on current heat and mass transfer sub-models, including the full formulation of the Forchheimer inertia effect and the permeability ratio of the biporous layers. The conclusions of this work aids in the development of compact and high-performance proton exchange membrane fuel cell stacks
Energies 2021, 14(12), 3675;
Hosseini, G., Daneshvariesfahlan, V., Wolf, S. & Hacker, V.
Bimetallic Pd-X (X = Ni, Co) nanoparticles on nitrogen-doped reduced graphene oxide (N-rGO) are prepared by a solid-state thermal technique followed by polyol reduction to be used as anode electrocatalysts for direct sodium borohydride-hydrogen peroxide fuel cells. The physical characterisation of the synthesised materials is investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. Finally, a direct sodium borohydride-hydrogen peroxide fuel cell with Pt/C as cathode and Pd-X (X = Ni, Co)/N-rGO as anode is constructed and operated with a power density of 353.84 and 275.35 mW cm-2 at 60 °C.
ACS Appl. Energy Mater. 2021, 4, 6, 6025–6039 doi.org/10.1021/acsaem.1c00876
Nagl, R., Zeiner, T., & Zimmermann, P. Interfacial properties such as interfacial mass transfer are essential for the design and optimization of industrial separation processes. In this work we investigate the interfacial behavior of the two quaternary systems water + toluene + ethanol + acetone and water + toluene + ethanol + tetrahydrofuran and the relation between interfacial enrichment and mass transfer. The Concentration Gradient Theory (CGT) is combined with the Koningsveld-Kleintjens (KK) model to calculate interfacial tension and interfacial concentration profiles. By expanding a recent study of ternary systems with ethanol, acetone or tetrahydrofuran as transferring components we demonstrate that interfacial mass transfer in quaternary systems can be modeled with CGT + KK in good accordance to experimental data by adjusting a single additional binary mobility coefficient. Moreover, the present study indicates a hint on a link between interfacial enrichment and interfacial mass transfer. Chemical Engineering and Processing - Process Intensification., 2021, Article number 108501. doi.org/10.1016/j.cep.2021.108501
Topical Meeting on “Potential for cost reduction and performance improvement of the IEA TCP AFC for PEMFC at component and system level”, IEA AFC, Webconference, TU Graz, 10/11. November 2021
TU Graz, in cooperation with Prof. D.J. Liu (ANL), is the organiser of the international Topical Meeting on “Potential for cost reductions and performance improvements at a component and system level”, supported by the Technology Collaboration Programme on Advanced Fuel Cells of the International Energy Agency.
8th RSE-SEE on Electrochemical Engineering and Electrochemistry (Graz, 10.-15. July, 2022)
The Institute of Chemical Engineering and Environmental Technology is a partner of BioBASE, the new innovation platform for bioeconomy and circular economy. With the support of BioBASE, new national and transnational as well as cross-sectoral cooperations between and within industry and science are being established. BioBASE focuses on the entire value chain of the bioeconomy and circular economy. The intensive use of fossil and mineral resources contributes to progressive climate change; a reversal in the energy and production system is therefore necessary. BioBASE is launching an innovation platform to promote biobased products and the recycling of products in a wide range of application areas. The Biorefinery working group at the ICVT is concerned with the isolation of valuable materials from biobased process flows by means of the application, adaptation and new development of thermal separation processes.
Right from the start, BioBASE has been embedded in a strong network of around 60 partner organisations and institutions, including some major Austrian companies as well as specialist representatives from the chemical, pulp and paper, wood, food and stone and ceramics industries. From the scientific side, BioBASE is supported by the most important universities and research institutions in this field. In addition, state governments of the federal states and location agencies or clusters are also part of the BioBASE network.
Das Institut für Chemische Verfahrenstechnik und Umwelttechnik ist Partner von BioBASE, der neuen Innovationsplattform für Bioökonomie und Kreislaufwirtschaft. Mit Unterstützung von BioBASE werden neue nationale und transnationale sowie auch branchenübergreifende Kooperationen zwischen und innerhalb Wirtschaft und Wissenschaft etabliert. BioBASE betrachtet mit ihren Schwerpunkten die gesamte Wertschöpfungskette der Bioökonomie & Kreislaufwirtschaft. Der intensive Einsatz fossiler und mineralischer Ressourcen trägt zum fortschreitenden Klimawandel bei, eine Umkehr im Energie- und Produktionssystem ist daher notwendig. BioBASE startet eine Innovationsplattform zur Forcierung biobasierter Produkte sowie der Kreislaufführung von Produkten in den unterschiedlichsten Anwendungsbereichen. Die AG Biorefinery am ICVT beschäftig sich dabei mit der Isolierung von Wertstoffen aus biobasierten Prozessströme mittels Anwendung, Adaptierung und Neuentwicklung von Thermischen Trennverfahren.
BioBASE ist schon vom Start weg in ein starkes Netzwerk von rund 60 Partnerorganisationen und -institutionen eingebettet, darunter einige wesentliche österreichische Unternehmen sowie Fachvertretungen aus der chemischen-, der Papier- und Zellstoff-, der Holz-, der Lebensmittel- und der Stein- und keramischen Industrie. Von wissenschaftlicher Seite wird BioBASE von den wichtigsten Universitäten und Forschungseinrichtungen aus diesem Bereich unterstützt. Darüber hinaus sind Landesregierungen der Bundesländer und Standortagenturen bzw. Cluster ebenfalls Teil des BioBASE-Netzwerks.
Erasmus+ traineeship student Mark Kozamernik shares his experience about life in Graz and work at the Institute of Chemical Engineering and Environmental Technology (CEET) at TU Graz during the Covid pandemic (TU Graz blog English).
Erasmus+-Praktikant Mark Kozamernik berichtet über das Leben in Graz und die Arbeit am Institut für Chemische Verfahrenstechnik und Umwelttechnik (CEET) an der TU Graz während der COVID-Pandemie (TU Graz blog German).
Marlene Kienberger, Silvia Maitz, Thomas Pichler and Paul Demmelmayer
Technologies for the isolation of lignin from pulping process streams are reviewed in this article. Based on published data, the WestVaco process, the LignoBoost process, the LigoForce SystemTM and the SLRP process are reviewed and discussed for the isolation of lignin from Kraft black liquor. The three new processes that have now joined the WestVaco process are compared from the perspective of product quality. Further, isolation processes of lignosulfonates from spent sulfite liquor are reviewed. The limitation for this review is that data are only available from lab scale and pilot scale experiments and not from industrial processes. Key output of this paper is a technology summary of the state of the art processes for technical lignins, showing the pros and cons of each process.
Processes, 2021, Volume 9, Issue 5, 804
Samsudin, A. M. & Hacker, V.
Anion exchange membranes (AEMs) consisting of quaternary ammonium poly(vinyl alcohol) (QPVA) and poly(diallyldimethylammonium chloride) (PDDA) were prepared by a solution casting method. The influence of the concentration of the chemical crosslinker on the properties and performance of AEMs was investigated. Morphology, chemical structures, thermal and mechanical properties of AEMs were characterized by SEM, FTIR, TGA, and UTM. The performance of AEMs was evaluated by water uptake, swelling degree, ion exchange capacity, and OH- conductivity measurement. The tensile strength, water uptake, and OH- conductivity of AEMs were enhanced with the increase of the crosslinker concentration. By introducing 12.5% glutaraldehyde (GA), the QPVA/PDDA AEMs achieved the highest tensile strength, water uptake, and OH- conductivity of 46.21 MPa, 90.6% and 53.09 ms cm−1 at ambient condition, respectively. The investigations show that crosslinked QPVA/PDDA AEMs are a potential candidate for anion exchange membrane fuel cells.
SEM image (left) and ion exchange capacity and conductivity (right) of a QPVA/PDDA anion exchange membrane [Samsudin and Hacker, 2021].
Journal of the Electrochemical Society, 2021, Volume 168, 27 p., 044526. doi.org/10.1149/1945-7111/abf781
Samsudin, A. M. Wolf, S., Roschger, M. & Hacker, V.
Cross-linked anion exchange membranes (AEMs) made of poly(vinyl alcohol) (PVA) as a backbone polymer and different approaches to introduce functional groups were prepared by solution casting with thermal and chemical cross-linking. Characterisation of the membranes was carried out by SEM, FTIR and thermogravimetric analyses. The performance of the AEMs was evaluated by water uptake, degree of swelling, ion exchange capacity, OH conductivity and single cell tests. A combination of quaternised ammonium poly(vinyl alcohol) (QPVA) and poly(diallyldimethylammonium chloride) (PDDMAC) showed the highest conductivity, water uptake and swelling among the other functional group sources. This study shows that PVA-based AEMs have the potential for the application of alkaline direct ethanol fuel cells (ADEFCs).
SEM image (left) and ion conductivity (right) of a PVA-based anion exchange membrane [Samsudin et al., 2021].
International Journal of Renewable Energy Development, 2021, Volume 10, Issue 3, p 435-443. Doi.org/10.14710/ijred.2021.33168
Gorgieva, S., Osmić, A., Hribernik, S., Božič, M., Svete, J., Hacker, V., Wolf, S. & Genorio, B. Herein, we prepared a series of nanocomposite membranes based on chitosan (CS) and three compositionally and structurally different N-doped graphene derivatives. Two-dimensional (2D) and quasi 1D N-doped reduced graphene oxides (N-rGO) and nanoribbons (N-rGONRs), as well as 3D porous N-doped graphitic polyenaminone particles (N-pEAO), were synthesized and characterized fully to confirm their graphitic structure, morphology, and nitrogen (pyridinic, pyrrolic, and quaternary or graphitic) group contents. The largest (0.07%) loading of N-doped graphene derivatives impacted the morphology of the CS membrane significantly, reducing the crystallinity, tensile properties, and the KOH uptake, and increasing (by almost 10-fold) the ethanol permeability. Within direct alkaline ethanol test cells, it was found that CS/N rGONRs (0.07 %) membrane (Pmax. = 3.7 mWcm −2) outperformed the pristine CS membrane significantly (Pmax. = 2.2 mWcm −2), suggesting the potential of the newly proposed membranes for application in direct ethanol fuel cells.
SEM image (left) and DEAFC cell voltage and power density (right) of a chitosan/graphene-based composite membrane [Gorgieva et al., 2021].
International Journal of Molecular Sciences. Volume 22, Issue 4, p. 1-25 25 p., 1740. Doi.org/10.3390/ijms22041740
Krenn, P., Zimmermann, P., Fischlschweiger, M. & Zeiner, T.
The solvent absorption of an epoxy o-cresol novolac resin composite has been measured in different aqueous electrolyte solutions (NaCl, CaCl2 and MgCl2) at different salt concentrations from 0.1 to 0.3 mg/l. Next to the total solvent uptake, which was measured by a gravimetric measurement, the absorption of ions was determined by ion chromatography and by atomic absorption spectroscopy. The measured solvent absorption in equilibrium was calculated by combining the ePC-SAFT equation of state with a network term, which takes into account elastic forces in the polymer network counteracting a further solvent absorption. In order to model the solvent absorption kinetics, the equation of state was combined with a Maxwell-Stefan diffusion approach and the viscoelastic Kelvin-Voigt model for chain relaxation. The model parameters were only fitted to the absorption in pure water, what was only possible because the epoxy resin absorbed a neglectable amount of ions. The fully predictively calculated values for the absorption in electrolyte solutions are in qualitative agreement to the measured data.
Fluid Phase Equilibria., 2021, Volume 529, Article number 112881 doi.org/10.1016/j.fluid.2020.112881
The Faculty of Technical Chemistry, Chemical & Process Engineering and Biotechnology has worldwide partnerships that serve student exchange and personnel mobility in the fields of teaching and research. Within the Erasmus+ program alone, there are currently about 30 specific agreements with partner universities. In addition, the individual institutes have a large number of specific cooperation agreements with foreign universities in the area of research.
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Grubinger, T., Lenk, G., Schubert, N. & Wallek, T. Fuel surrogates are substitute mixtures that are developed to reproduce real fuels’ physical and chemical properties. These mixtures are created with a small number of components, considering their application in various types of simulations and for bench tests. In the present paper, new gasoline surrogates are proposed by extending and applying an algorithm which was previously developed and successfully used to create diesel surrogates. The five target properties chosen for surrogate optimization include the true boiling point curve (TBP), the research octane number (RON), the liquid density, the carbon-to-hydrogen (C/H) ratio and the oxygenate content. The algorithm is applied to three target fuels, comprising two reference fuels from the FACE working group and one typical oxygenated gasoline that is commercially available in Europe. The proposed surrogates consist of six chemical components which are also represented in reaction kinetics for fuel combustion. An experimental comparison of the boiling point curves, densities and RONs among the surrogates and their respective target fuels provided evidence that the proposed surrogates excellently reproduce the real fuels' properties.
Fuel, 2021, Volume 283, 118642 doi.org/10.1016/j.fuel.2020.118642
Bol, P., Rudelstorfer, G., Grafschafter, A. & Siebenhofer, M.
Liquid-liquid extraction is a major separation process in chemical industry. Beside appropriate design of mass transfer equipment, successful design of phase separation equipment is an important issue. Therefore, the separation of liquid-liquid dispersions was investigated and modeled with kinetic approaches to gain information for settler design. A modified first-order sedimentation rate model, a first-order consecutive step rate model, and a mixed-order rate model were applied and compared to the experimental data. The advantage of kinetic modeling of the rate of sedimentation, specifically addressing the impact of viscosity and electrolyte concentration, was successfully demonstrated.
Chemie-Ingenieur-Technik, 2021, Volume 3, Issue 1-2, p. 260-272 13 p. doi.org/10.1002/cite.202000126
Research on Next Generation Fuel Cell and Hydrogen Technologies
Due to current efforts being made in the reduction of greenhouse gas emissions and the associated political focus on hydrogen as a clean energy carrier, methods for sustainable hydrogen production and efficient utilization are again in great demand. In the coming years, fundamental and industry-related research as well as innovative ideas are essential to meet the ambitious goals with regard to efficiency, service life and sustainability of the whole process chain. The fuel cells and hydrogen working group is currently focusing on several approaches to tackle these challenges.
Wasserstoff – der Stromspeicher der Zukunft?
Soll unser Energiesystem umweltfreundlicher werden, so führt kein Weg an Wasserstoff als Energieträger vorbei. Dessen sind sich Forschende weltweit sicher. Rund 160 Wissenschafterinnen und Wissenschafter arbeiten an der TU Graz an Methoden der Erzeugung, Speicherung, des Transports und der Nutzung von Wasserstoff in mobilen, stationären und industriellen Anwendungen
Pichler, T. M., Stoppacher, B., Kaufmann, A., Siebenhofer, M. & Kienberger, M.
The neutralization of NaOH with CO2 in a continuously operated airlift reactor with gas flow rates up to 10 NL min−1 and gas phase recycle was investigated. Neutralization experiments were performed at 25 °C and the amount of absorbed CO2, as well as the NaOH feed rate, were recorded. The reaction rate was calculated based on the two‐film theory and empirical equations for several parameters. The calculations of the volumetric mass transfer coefficient, the liquid phase circulation velocity, and the gas holdup were experimentally validated. The reaction rate and the process efficiency were modeled with a deviation of 5 %. Journal of Chemical Engineering & Technology, 2021, Volume 44, Issue 1, p. 38-47 10 p. doi.org/10.1002/ceat.202000319
Krenn, P., Zimmermann, P., Fischlschweiger, M. & Zeiner, T. Epoxy resins are often applied to prevent sensitive electronics to come into contact with solvents. Therefore, it is necessary to know the diffusion through the epoxy resins to determine the thickness of the epoxy resins layer for different applications. In this work a diffusion model is developed on the basis of the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equation of state. To consider the polymer network, PC-SAFT is combined with an elastic term. The driving force for the diffusion is the gradient of the chemical potential, but additionally the viscoelastic polymer relaxation below the glass transition temperature is considered. The model is applied to calculate the diffusion of water, isopropyl alcohol, and heptane through the epoxy resin at different temperatures. The modeled diffusion processes are in good agreement with experimentally determined data. Even highly anomalous absorption kinetics, which were measured for isopropyl alcohol diffusion, could be explained and calculated on the basis of the developed diffusion model. Journal of Chemical & Engineering Data, 2020, Volume 65, Issue 12, p. 5677-5687 11 p. doi.org/10.1021/acs.jced.0c00668
Katharina Kocher and Viktor Hacker
Polymer stabilization proved to be a promising approach to increase the catalytic performance of common platinum/carbon based cathode catalysts (Pt/C) used in polymer electrolyte membrane fuel cells (PEMFCs). Platinum and polyaniline composite catalysts (Pt/C/PANI) were prepared by combining chemical polymerization reactions with anion exchange reactions. Electrochemical ex‐situ characterizations of the decorated Pt/C/PANI catalysts show high catalytic activity toward the oxygen reduction reaction (ORR) and, more importantly, a significant enhanced durability compared to the undecorated Pt/C catalyst. Transmission electron microscopy (TEM) investigations reveal structural benefits of Pt/C/PANI for ORR catalysis. All studies confirm high potential of Pt/C/PANI for practical fuel cell application.
Figure: Illustration of Pt/C/PANI catalyst. ©TU Graz/CEET
ChemistryOpen (November 5, 2020)
The guest editors Prof. Katrašnik and Prof. Hacker invite you to submit articles for a special issue of Energies on “Development of Advanced Models for Analysis and Simulation of Fuel Cells”. To address the requirements on shorter product development cycles and reduced development costs, while boosting power density, efficiency, service life and safety, it is necessary to rely on advanced simulation models in the development process of fuel cells, their components, and fuel-cell-based systems. Simulation models are also indispensable for the analysis of fuel cells and for precise online monitoring.
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Special Issue Homepage
Patrick Krenn, Patrick Zimmermann, Michael Fischlschweiger and Tim Zeiner
Fluid Phase Equilibria, Volume 529, 1 February 2021, 112881
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In order to achieve the climate targets, the use of hydrogen is necessary. Numerous experts from industry and science agree on this. In recent years Graz has become a veritable hotspot for fuel cell and hydrogen research. We asked the top developers what makes hydrogen so interesting and why it can be a driver not only for climate protection but also for the economy.
Wirtschaftsnachrichten Süd, 10/2020, 54-57
Christoph Mayer and Thomas Wallek
In this paper, a model for two-component systems of six-sided dice in a simple cubic lattice is developed, based on a basic cluster approach previously proposed. The model represents a simplified picture of liquid mixtures of molecules with different interaction sites on their surfaces, where each interaction site can be assigned an individual energetic property to account for cooperative effects. Based on probabilities that characterize the sequential construction of the lattice using clusters, explicit expressions for the Shannon entropy, synonymously used as thermodynamic entropy, and the internal energy of the system are derived. The latter are used to formulate the Helmholtz free energy that is minimized to determine thermodynamic bulk properties of the system in equilibrium. The model is exemplarily applied to mixtures that contain distinct isomeric configurations of molecules, and the results are compared with the Monte-Carlo simulation results as a benchmark. The comparison shows that the model can be applied to distinguish between isomeric configurations, which suggests that it can be further developed towards an excess Gibbs-energy, respectively, activity coefficient model for chemical engineering applications.
Entropy 2020, 22(10), 1111;
Demmelmayer, P., Hilgert, J., Wijaya, R. & Kienberger, M. Crud formation during reactive extraction hinders phase separation and makes the application of conventional extraction equipment more challenging. This study investigates the influence of amines as a reactive extractant, pH value, and temperature on the crud formation and extraction efficiency for the reactive extraction of lignosulfonates from the Ca–lignosulfonate model solution and spent sulfite liquor. The overall extraction efficiency for different amines dissolved in 1-octanol increased in the order quaternary < tertiary < secondary < primary amines for both the model solution and the spent liquor. Phase equilibria for dioctylamine and trioctylamine showed that the temperature increase from 25 to 50 °C had no effect on the extraction efficiency but clearly reduced the crud formation in the extraction step. No crud was observed during back extraction into deionized water, 0.3 M NaOH, or 0.3 M NaHCO3. The pH value highly influences the phase equilibrium; the extraction step has to be performed at low pH values and the back extraction step at high pH values. Industrial & Engineering Chemistry Research, 2020, Volume 59, Issue 37, p. 16420-16426 7 p. doi.org/10.1021/acs.iecr.0c02525
Bernd Stoppacher, Robert Zacharias, Michael Lammer, Sebastian Bock, Karin Malli and Viktor Hacker
Der Reformer Steam Iron Cycle (RESC), eine Weiterentwicklung des Eisen-Dampf-Prozesses, bietet eine effiziente und kostengünstige Möglichkeit der dezentralen Wasserstoffherstellung. Das auf Reduktions- und Oxidationsreaktionen basierende Chemical Looping System ist in der Lage, hochreinen Wasserstoff aus Biogas, vergaster Biomasse und gasförmigen Kohlenwasserstoffen zu erzeugen. Da eine Reinheit von > 99.999 % bereits im RESC Prozess erreicht wird, sind im Gegensatz zu konventionellen Verfahren, wie Dampfreformierung oder autotherme Reformierung, keine weiteren Reinigungsschritte im System notwendig. Zudem kann das System, durch Abscheidung von hochreinem Stickstoff und Kohlenstoffdioxid, wertvolle Nebenprodukte erzeugen und als Negativemissionstechnologie betrieben werden.
The Reformer Steam Iron Cycle (RESC), a further development of the iron-steam process, offers an efficient and cost-effective option for decentralized hydrogen production. The chemical looping system based on reduction and oxidation reactions is capable of producing high-purity hydrogen from biogas, gasified biomass and gaseous hydrocarbons. Since a purity of > 99.999 % is already achieved in the RESC process, no further purification steps are necessary in the system, in contrast to conventional processes such as steam or autothermal reforming. In addition, the system can generate valuable by-products by separating high purity nitrogen and carbon dioxide and can be operated as a negative emission technology.
gwf Gas+Energie, 09/2020, ISSN 2366-9594, Seite 62-69
M. Mohsin, R. Raza, M. Mohsin-ul-Mulk, A. Yousaf, V. Hacker
In this paper the diagnostic results of single polymer electrolyte membrane fuel cell assemblies are presented, which are characterized by polarization curves. Single PEM fuel cell assemblies were investigated by accelerated voltage cycling tests at different humidity levels. The cells are discussed in this paper with analysis results at different humidity values and different atmospheric pressures. The decrease in relative humidity can result in slower electrode kinetics, including electrode reaction and mass diffusion rates, and higher membrane resistance.
International Journal of Hydrogen Energy, Volume 45, Issue 45, 24093-24107.
Paul Demmelmayer, Julio Hilgert, Robby Wijaya, and Marlene Kienberger
Crud formation during reactive extraction hinders phase separation and makes the application of conventional extraction equipment more challenging. This study investigates the influence of amines as a reactive extractant, pH value, and temperature on the crud formation and extraction efficiency for the reactive extraction of lignosulfonates from the Ca–lignosulfonate model solution and spent sulfite liquor. The overall extraction efficiency for different amines dissolved in 1-octanol increased in the order quaternary < tertiary < secondary < primary amines for both the model solution and the spent liquor. Phase equilibria for dioctylamine and trioctylamine showed that the temperature increase from 25 to 50 °C had no effect on the extraction efficiency but clearly reduced the crud formation in the extraction step. No crud was observed during back extraction into deionized water, 0.3 M NaOH, or 0.3 M NaHCO3. The pH value highly influences the phase equilibrium; the extraction step has to be performed at low pH values and the back extraction step at high pH values.
Ind. Eng. Chem. Res. 2020, 59, 37, 16420–16426
Tobias Grubinger, Georg Lenk, Nikolai Schubert and Thomas Wallek
Fuel surrogates are substitute mixtures that are developed to reproduce real fuels’ physical and chemical properties. These mixtures are created with a small number of components, considering their application in various types of simulations and for bench tests. In the present paper, new gasoline surrogates are proposed by extending and applying an algorithm which was previously developed and successfully used to create diesel surrogates.
The five target properties chosen for surrogate optimization include the true boiling point curve (TBP), the research octane number (RON), the liquid density, the carbon-to-hydrogen (C/H) ratio and the oxygenate content.
The algorithm is applied to three target fuels, comprising two reference fuels from the FACE working group and one typical oxygenated gasoline that is commercially available in Europe. The proposed surrogates consist of six chemical components which are also represented in reaction kinetics for fuel combustion. An experimental comparison of the boiling point curves, densities and RONs among the surrogates and their respective target fuels provided evidence that the proposed surrogates excellently reproduce the real fuels' properties.
Fuel, Volume 283, 1 January 2021, 118642
Michael Lammer and Viktor Hacker
Chemical circulation processes require high-tech materials as oxygen carriers in the fixed-bed reactor. These consist of the reactive iron-based species and inert additives to maintain the functionality of the process. This chapter contains data on various materials and on the chemical reactions and reaction mechanisms. Side reactions and their respective influence on the product gas quality, i.e. the purity, are discussed in detail. Emphasis is placed on the sustainability aspects of this technology by providing information on the pre-pressurization of hydrogen and the sequestration of carbon dioxide.
Published in Current Trends and Future Developments on (Bio-) Membranes: New Perspectives on Hydrogen Production, Separation, and Utilization, A. Iulianelli & A. Basile (eds), 1st edn, Elsevier B.V., Amsterdam, pp. 225-240.
The fact that liquid manure stinks and pollutes the groundwater is no big news. But that it can be converted into valuable fertiliser is perhaps. In a pilot project, nitrogen is removed from the liquid manure and what remains are the pure raw materials.
Robert Zacharias, Sebastian Bock and Viktor Hacker
The successful application of fixed bed chemical looping for hydrogen production in industrial scale demands highly stable oxygen carrier pellets. The vast experience of the research group on the steam iron process enabled the researchers to identify the most crucial differences and challenges in the preparation of suitable oxygen carriers.
The goal of this work was the realistic long-term characterization of pelletized oxygen carriers in a fixed bed reactors, which revealed a high temperature gradient, decreased oxygen exchange capacity and a rapid increase in system pressure caused by to powder formation for some samples. The experimental results of this study indicate that the long-term redox cycling seems to outweigh the impact of oxygen carrier preparation methods that may be overvalued in the long run.
Fuel Processing Technology, 2020, 208.
Hydrogen researchers at Graz University of Technology, together with the Graz-based Start-Up Rouge H2 Engineering, have developed a cost-effective process for the decentralized production of high-purity hydrogen. The research success resulted in a compact and space-saving On-Site-On-Demand-System (OSOD) for filling stations and energy plants, which is developed and distributed by Rouge H2 Engineering.
The inner workings of the OSOD H2 generator. The blue cuboid is the core development: a gas furnace with four tubular reactors in which the chemical looping process for hydrogen production takes place (Photo RGH2 in magazine KLIPP, June/July 2020).
TU Graz Planet Research
Nestor Sanchez, Ruth Ruiz, Viktor Hacker and Martha Cobo
The bioethanol produced by biomass fermentation contains large quantities of water and can be used directly in the ethanol steam reformer without any purification steps. However, such bioethanol samples contain a broad spectrum of impurities that make the reformation process more difficult. This overview defines options to reduce impurities with negative influence on the reforming process and to increase the positive ones during pre-treatment and fermentation of the biomass.
International Journal of Hydrogen Energy, 45(21).
Viktor Hacker and Chistof Sumereder
Fundamentals of Electrical Engineering is an excellent introduction into the areas of electricity, electronic devices and electrochemistry. The book covers aspects of electrical science including Ohm and Kirkoff's laws, P-N junctions, semiconductors, circuit diagrams, magnetic fields, electrochemistry, and devices such as DC motors. This textbook is particularly useful for students of chemical, materials, and mechanical engineering.
De Gruyter Textbook , 224 pages
The solvent uptake in equilibrium of a highly cross-linked epoxy o-cresol novolac resin in water, isopropanol, and heptane was experimentally measured and modeled with the perturbed-chain statistical association fluid theory (PC-SAFT) equation of state. As suggested in the literature, PC-SAFT was combined with a network term, which takes additional elastic forces into account. The model parameters of the epoxy resin were generated by fitting them to the measured solvent uptake in pure substances and to the density of the epoxy resin, which provided a very good agreement with the experimental data. Furthermore, the solvent uptake in the mixtures isopropanol/water and isopropanol/heptane was predicted in very good agreement to the experimental data. For the first time, a thermodynamic model was developed to calculate the solvent uptake in an epoxy resin.
Industrial and Engineering Chemistry Research, 59(11), 5133-5141.
Astrid Loder, Matthäus Siebenhofer and Susanne Lux
A bifunctional Ni/MgO catalyst was prepared to catalyze CO2 methanation and make use of CO2 as an abundant hydrogen storage facility. The effect of Ni loading and MgO quality on the rate of methanation was tested in a temperature range of 533–648 K. The Ni loading was varied between 0 to 27 wt.% on MgO. To investigate the impact of matrix elements, a MgO/CaO support was tested with 21 wt.%. nickel loading. Further, the role of MgO in the bifunctional catalyst was proven. The reaction kinetics was modeled with a Langmuir–Hinshelwood approach considering the bifunctional character of the catalyst. Nickel provides the adsorbent capacity for hydrogen and is highly selective for methane. MgO activates CO2 through chemisorption. Increasing Ni loading of the catalyst increased the rate of CO2 conversion. According to the results, the mechanism of CO2 methanation did not change with Ni loading. The Ni/MgO catalyst acted as a robust, active and highly selective catalyst for CO2 methanation. With CO2 conversion of 87%, the selectivity to methane was ≥99%. Besides excellent catalytic activity the catalysts suffice the necessity of simple catalyst preparation, usage and recyclability for industrial applicability of CO2 methanation.
Loder et al. (2020) – Published by Elsevier B.V. All rights reserved.
Journal of Industrial and Engineering Chemistry, 2020, Volume 85.
Sebastian Bock, Robert Zacharias and Viktor Hacker
The transition of our current carbon-based economy towards a sustainable energy system poses major challenges for all stakeholders. Harmful carbon dioxide emissions have to be substantially decreased and even negative emissions are mandatory to avoid a global mean temperature rise above 2 °C unless stringent regulatory measures are taken within the next decade. Chemical looping is an effective method to sequestrate pure carbon dioxide from fossil and renewable energy resources within the framework of carbon capture and storage (CCS) or utilization (CCU) technologies.
The presented study demonstrates the generation of high-purity hydrogen exceeding 99.997% as a zero-emission energy carrier with the inherent co-generation of pure carbon dioxide (99%) and nitrogen (98.5%) in the largest fixed-bed chemical looping research system worldwide with a feedstock utilization of up to 60%. The use of renewable primary energy sources as biogas qualifies the process as a negative emission technology (NET) if carbon dioxide is appropriately utilized.
Sustainable Energy Fuels, 2020,4, 1417-1426.
Bernd Cermenek, Boštjan Genorio, Thomas Winter, Sigrid Wolf, Justin G. Connell, Michaela Roschger, Ilse Letofsky-Papst, Norbert Kienzl, Brigitte Bitschnau and Viktor Hacker
Direct ethanol fuel cells (DEFC) still lack active and efficient electrocatalysts for the alkaline ethanol oxidation reaction (EOR). In this work, a new instant reduction synthesis method was developed to prepare carbon supported ternary PdNiBi nanocatalysts with improved EOR activity. Synthesized catalysts were characterized with a variety of structural and compositional analysis techniques in order to correlate their morphology and surface chemistry with electrochemical performance. The modified instant reduction synthesis results in well-dispersed, spherical Pd85Ni10Bi5 nanoparticles on Vulcan XC72R support (Pd85Ni10Bi5/C(II-III)), with sizes ranging from 3.7 ± 0.8 to 4.7 ± 0.7 nm.
J. Electrocatalysis 11, 203–214.
Marlene Kienberger, Paul Demmelmayer, Michael Weißl, Armin Zankl and Stefan Spirk
The paper presents an experimental study on the preparation and characterization of cellulose films and their use for reactive lignosulfonate extraction. The extraction of lignosulfonates leads to emulsion and crud formation when standard equipment is applied. By using cellulose films as a support layer between the aqueous feed phase and the organic extractant phase, emulsion formation is prevented. The results showed that selective separation and a fractionation of the lignosulfonates can be realized with this novel approach simultaneously.
Solvent Extraction and Ion Exchange, Volume 38, 2020 - Issue 1.
Asep Muhamad Samsudin and Viktor Hacker
Anion exchange membranes (AEMs) contribute significantly to enhance the performance and efficiency of alkaline polymer electrolyte fuel cells (APEFCs). A sequence of composite anion exchange membranes (AEMs) consisting of poly(vinyl alcohol) (PVA), poly(diallyldimethylammonium chloride) (PDDA), and nano-zirconia (NZ) has been prepared by a solution casting technique. The effect of zirconia mass ratio on attribute and performance of composite AEMs was investigated.
The chemical structures, morphology, thermal, and mechanical properties of AEMs were characterized by FTIR, SEM, thermogravimetric analysis, and universal testing machine, respectively. The performance of composite AEMs was verified using water uptake, swelling degree, ion-exchange capacity, and OH− conductivity measurement. The nano-zirconia was homogeneously dispersed in the PVA/PDDA AEMs matrix. The mechanical properties of the composite AEMs were considerably enhanced with the addition of NZ. Through the introduction of 1.5 wt.% NZ, PVA/PDDA/NZ composite AEMs acquired the highest hydroxide conductivity of 31.57 mS·cm−1 at ambient condition. This study demonstrates that the PVA/PDDA/NZ AEMs are a potential candidate for APEFCs application.
J. Polymers 2019, 11(9), 1399
Den Landespreis „Energy Globe Styria Award" konnte sich in diesem Jahr das Projekt Reduzierende Kalzinierung unter der Leitung von Susanne Lux in Kooperation mit der voestalpine Stahl GmbH und der VA Erzberg GmbH sichern. Dabei gewannen sie den „Energy Globe Styria Award" in der Kategorie „Forschung“ und holten sich auch das „goldene Ticket" für den nationalen „Energy Globe Austria Award" in Linz.
Ziel des Projekts ist es, die Veredelung von Eisenerz zu Eisenoxid nicht wie derzeit üblich durch Sintern unter oxidierenden Bedingungen, sondern unter reduzierenden Bedingungen in Wasserstoffatmosphäre stattfinden zu lassen. Durch dieses Konzept können deutliche Emissions- und Energieeinsparungen erreicht werden.
Im CEET Konkret 2019 präsentieren wir euch unsere aktuellen Forschungsergebnisse und bieten einen Überblick über unsere Themengebiete. Zusätzlich gibt es einen Einblick in unsere internationalen Aktivitäten, sowie das Institutsleben abseits von Forschung und Lehre.
Wir wünschen euch viel Spaß beim Lesen!
CEET Konkret 2019
Biorefineries' Processes and Sustainability
Das CEET-Konkret bietet einen Überblick über aktuelle Forschungsthemen und Instituts-Ereignisse aus dem vergangenen Jahr.
Fig.: Presentation of the national reward "Mobilität 2017" (bmvit, 27.01.2017) by the Federal Minister for the research project "H2 Mobility".
Over 70 participants from 13 countries (Austria, China, Denmark, Germany, Italy, Israel, Japan, Finland, France, Slovenia, South Africa, Sweden, and USA) attended the exciting workshop “Highlights of International Fuel Cell Research 2017” on May 15, 2017.
Prof. Harald Kainz, Rector of Graz University of Technology, opened the workshop and welcomed the renowned scientists. Theodor Zillner, representative of the Austrian Ministry for Transport, Innovation and Technology (bmvit), pointed out the importance of the international network IEA and the international cooperation in science and technology.
D.J. Liu, Argonne National Laboratory USA and Operating Agent of Annex 31 and Fabio Matera, Consiglio Nazionale delle Ricerche Italy and Operating Agent of Annex 35, introduced the IEA Technology Collaboration Programme and the Annexes. Prof. Viktor Hacker, Institute of Chemical Engineering and Environmental Technologies of TU Graz and local organiser of the workshop, gave a short overview of research groups in the field of fuel cells in Austria.
In the main session, the experts presented and discussed in 15 lectures the results and scientific breakthroughs of international fuel cell development. In the evening, the poster session gave the opportunity for discussion with the experts and national representatives of the annexes.
Im Rahmen des Horizon 2020 Projektes BioEnergyTrain (grant agreement N 656760) wurden zwei Masterstudiengänge in dem Umfeld der biobasierten Industrie / biobasierten Energieerzeugung entwickelt, BioRefinery Engineering und BioResource Value Chain Optimization. Der Masterstudiengang BioRefinery Engineering wird ab dem Wintersemester 2017/2018 an der Technischen Universität Graz angeboten. Weiterführende Informationen sind hier https://www.tugraz.at/studium/studienangebot/masterstudien/biorefinery-engineering/) zu finden.
Dipl.-Ing. Dr. tech. Bsc. Christoph Grimmer hat gemeinsam mit Kollegen am Institut für Chemische Verfahrenstechnik und Umwelttechnologien ein Plug&Play Speichersystem für Haushalte entwickelt. Weiteres unter...
Msc. Thomas Goetsch hat mit seinem Vortrag " Vorhersage und experimentelle Überprüfung des Oiling out-Effektes bei der Trennung von Isomeren" den Vortragspreises des Dechema Fachausschusses Kristallisation (6.-7. März 2017 in Köln) bekommen. Die Co-autoren des Vortrages sind Patrick Zimmermann (Karlsruhe Institute of Technology), Rebecca van den Bongardt (TU Dortmund), Amelie Köhler (TU Dortmund), Sabine Enders (Karlsruhe Institute of Technology) und Tim Zeiner.
Bettina Koch Mag.phil.
Jutta Freißmuth Oberkontrollorin
Tel. +43 (316) 873 - 7462 Fax +43 (316) 873 - 107462 jutta.freissmuthnoSpam@tugraz.at Visitenkarte