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Michaela Roschger, Sigrid Wolf, Boštjan Genorio and Viktor Hacker
In this work, the metal content of Pd85Ni10Bi5/C catalysts for the alkaline ethanol-oxidation reaction was reduced from 40 wt.% (PdNiBi/C (40/60)) to 30 wt.% (PdNiBi/C (30/70)), 20 wt.% (PdNiBi/C (20/80)) and 10 wt.% (PdNiBi/C (10/90)), while increasing performance. The synthesized catalysts were examined using physicochemical measurements and electrochemical measurements. The best performing catalysts were used to fabricate membrane electrode assemblies for carrying out single-cell tests and to determine the influence of the metal/carbon ratio of the electrode. The electrochemical surface area (695 cm2 mg−1) and activity were increased, resulting in high peak-current densities for the ethanol oxidation reaction (3.72 A mg−1) by the resulting more accessible metal particles. The electrode produced with the PdNiBi/C (30/70) catalyst reached a maximum power density of 34.8 mW mg−1 at 50 °C. This successfully demonstrated a doubling of the power density compared with the performance of the PdNiBi/C (40/60) electrode, while simultaneously reducing the costs.
Asep Samsudin, Michaela Roschger, Sigrid Wolf and Viktor Hacker
In recent years, there has been considerable interest in anion exchange membrane fuel cells (AEMFCs) as part of fuel cell technology. Anion exchange membranes (AEMs) provide a significant contribution to the development of fuel cells, particularly in terms of performance and efficiency. Polymer composite membranes composed of quaternary ammonium poly(vinyl alcohol) (QPVA) as electrospun nanofiber mats and a combination of QPVA and poly(diallyldimethylammonium chloride) (PDDA) as interfiber voids matrix filler were prepared and characterized. The influence of various QPVA/PDDA mass ratios as matrix fillers on anion exchange membranes and alkaline fuel cells was evaluated. The structural, morphological, mechanical, and thermal properties of AEMs were characterized. To evaluate the AEMs’ performances, several measurements comprise swelling properties, ion exchange capacity (IEC), hydroxide conductivity (σ), alkaline stability, and single-cell test in fuel cells. The eQP-PDD0.5 acquired the highest hydroxide conductivity of 43.67 ms cm−1 at 80 °C. The tensile strength of the membranes rose with the incorporation of the filler matrix, with TS ranging from 23.18 to 24.95 Mpa. The peak power density and current density of 24 mW cm−2 and 131 mA cm−2 were achieved with single cells comprising eQP-PDD0.5 membrane at 57 °C.
Nanomaterials 2022, 12, 3965.
The ElektroPower project of the Institute of Chemical Engineering and Environmental Technology was awarded the Austrian Start-up Prize PHÖNIX in the category "PROTOTYPE" by the Federal Minister Martin Kocher of the Ministry of Labour and Economy (BMAW) and the Federal Minister Martin Polaschek of the Ministry of Education, Science and Research (BMBWF). In total, there were over 200 submissions and four prizes were assigned.
Merit Bodner received the Young Scientist Award 2022 for the Hydrogen Usages Pillar, organized by Hydrogen Europe Research. The award ceremony took place on the 26th of October 2022 as part of the Hydrogen Week 2022 in Brussels.
Young Scientist Award 2022
The course Chemical Engineering of biobased products, held by Marlene Kienberger and the course ´Bioethanolveredelung´ held by Georg Rudelstorfer are nominated for the ´Price for Excellence in teaching´. Both courses are on the short list for the price.
As part of the cooperation Research and Innovation Ecosystem Graz (RIE Graz), the institute was visited on the initiative of the head of Siemens Technology Austria and the head of CCT Additive Manufacturing, organized by DI Christine Schichler.
Astrid Loder, Simone Santner, Matthäus Siebenhofer, Andreas Böhm, Susanne Lux*
Direct reduction of mineral iron carbonate with hydrogen is a CO2-lean technology for the production of elemental iron from iron carbonate ore. In this study, the reaction mechanism and reaction kinetics were investigated by thermogravimetric analysis and in a fixed-bed tubular reactor. The degree of metallization increases with increasing temperature from 773 to 1023 K. At 1023 K, the degree of metallization is 93 wt%, with the remaining iron species being wüstite. The reduction proceeds via two reaction pathways: calcination of iron carbonate to wüstite with consecutive reduction of wüstite to elemental iron and direct reduction of iron carbonate to elemental iron. The reaction steps occur simultaneously. During the first hour of reaction, which corresponds to the heat-up phase, calcination of iron carbonate to wüstite adopts the dominant reaction path. Then wüstite reduction and direct iron carbonate reduction with hydrogen to elemental iron, become dominant, facilitated by the increasing porosity of the ore due to the release of CO2. Towards the end of the reduction process the remaining wüstite is reduced to elemental iron. The kinetic triplet – solid phase reaction kinetic model, activation energy and frequency factor – was determined for each reaction step. The reaction kinetics can be described by a combination of an Avrami-Erofeyev model (A3 model for iron carbonate calcination to wüstite), and reaction-order models (F2 model for the reduction of iron carbonate to elemental iron and F3 model for the reduction of wüstite to elemental iron).
Chemical Engineering Research and Design 188 (2022) 575-589
During the Seminar RE4Industry Knowledge Transfer on 20-22 October 2022 at TU Graz, Inffeldgasse 25/D, i7, Prof. Hacker chaired the session ‘Green Hydrogen’ supported by Prof Lux as expert, and Prof. Kienberger moderated the panel on Circular Bioeconomy.
The ElektroPower project of the Institute of Chemical Engineering and Environmental Technology has been nominated in the category "PROTOTYPE" for the Austrian start-up prize PHÖNIX, which is awarded on behalf of the Federal Ministry of Education, Science and Research (BMBWF) and the Federal Ministry for Digital and Economic Affairs (BMDW).
Michaela Roschger, Sigrid Wolf, Kurt Mayer, Matthias Singer and Viktor Hacker
Alkaline direct ethanol fuel cells (DEFCs) represent an efficient energy conversion device for sustainable ethanol fuel. In this study, a design with new structural parameters for the anodic flow field of the alkaline DEFC was modeled with the aid of computational fluid dynamics and was then actually constructed. Single-cell tests were performed to evaluate the impact of the developed design on fuel cell performance. The results show that fuel cell performance significantly increased when using the improved design in the low-temperature range. The higher the temperature in the cell, the lower the influence of the flow field structure on performance. In addition, the influence of external factors, such as the orientation of the cell, the preheating of the fuel, and the direction of the two fuel flows relative to each other (co-current and counter-current), are shown.
For his PhD thesis “Modeling of Interfacial Mass Transfer in Liquid-Liquid Systems”, Roland Nagl received the MegaWATT award for the best annual PhD-thesis in the field of technical thermodynamics at a DACH university. In his thesis Roland Nagl established a modeling framework to investigate the fundamental phenomena which govern the mass transfer through liquid-liquid interfaces in industrial separation processes. The price was awarded by the WATT e.V. during the Thermodynamik-Kolloquium 2022 conference in Chemnitz.
TU Graz SciPix is a photo and video competition held at TU Graz, which focuses the spotlight on the diverse research being carried out. With three awarded contributions the institute was very successful this year. The photos and video contributions will first be displayed on the Campus Alte Technik, then moved on to the Campus Neue Technik and finally displayed at the Campus Inffeldgasse.
Winning photos and video:
Rainbow column: This is the Taylor Couette Disc Contactor, which was used for CO2 purification of a gas stream with sodium hydroxide. The pH curve was visualized in the course of the chemical reaction with a universal indicator. © TU Graz
Taylor lava lamp: The eponymous vortex formations of the Taylor-Couette flow are used to bring immiscible phases into contact (gases, liquids and solids). The solid serves as a heterogeneous catalyst and the red colored solvent extracts the reaction product. © TU Graz
The beauty of the imperfect: During the production of a fuel cell, catalyst ink is ultrasonically sprayed onto the membrane. Perfect homogeneity is essential. Here, the aesthetic pattern was created by too much ink. The swollen membrane is unusable. © TU Graz
Mario Kircher, Georg Rudelstorfer, Michaela Roschger, Michael Lammer, Rafaela Greil and Susanne Lux (from left to right) © TU Graz
Link to TU Graz SciPix: https://www.tugraz.at/en/research/research-at-tu-graz/tu-graz-scipix/
To learn about the CO2 problem, the fourth grade students of the Carneri BG/BRG visited the institute on 20 September 2022 and also gained insights into the research work in the field of hydrogen technology.
© TU Graz
Feedback on the visit:
The Summer School on Advanced Studies of Polymer Electrolyte Fuel Cells was organised for the fourteenth time in cooperation between Yokohama National University and Graz University of Technology.
The seven-day program was opened by Prof. Mitsushima and Prof. Hacker, where they placed an emphasis on the long-standing tradition of the summer school and the cooperation between the Universities. The 14th International Summer School on PEFCs attracted 63 participants from 16 different universities and companies.
The Interreg SI-AT H₂GreenTECH project has successfully reached its finish line! The project partners contributed to the establishment of a hydrogen ecosystem in the field of green hydrogen and hydrogen technologies in the cross-border area Slovenia-Austria.
The developed Hydrogen Center, as a B2B web platform and One-stop-shop, is an integrative facilitator and motivator for finding common solutions with its existing and future members that contribute to the improvement of the regional hydrogen ecosystem. It serves companies, researchers, and students by providing information, encouraging research and business networks and collaboration opportunities, sharing knowledge, and improving the flow of innovation in the cross-border area. Two strategic documents to support and guide the further development of the Hydrogen Center were prepared.
Asep Samsudin, Merit Bodner and V. Hacker
Anion exchange membrane fuel cells have unique advantages and are thus gaining increasing attention. Poly(vinyl alcohol) (PVA) is one of the potential polymers for the development of anion exchange membranes. This review provides recent studies on PVA-based membranes as alternative anion exchange membranes for alkaline fuel cells. The development of anion exchange membranes in general, including the types, materials, and preparation of anion exchange membranes in the last years, are discussed. The performances and characteristics of recently reported PVA-based membranes are highlighted, including hydroxide conductivity, water uptake, swelling degree, tensile strength, and fuel permeabilities. Finally, some challenging issues and perspectives for the future study of anion exchange membranes are discussed.
Polymers, MDPI 2022
Silvia Maitz, Matthäus Siebenhofer and Marlene Kienberger
Black liquor, a side stream of the kraft pulping process, contains valuable low molecular weight carboxylic acids and carbohydrates. Hydrothermal treatment and wet oxidation of black liquor with a dry matter content of 43 % were investigated as an approach to convert these carbohydrates to carboxylic acids to increase their concentration. Wet oxidation with H2O2 or O2 at 115–185 °C led to partial degradation of carbohydrates, but no significant formation of the investigated carboxylic acids, glycolic, lactic, formic and acetic acid, was detected. Treatment under N2 atmosphere at 185 and 220 °C finally led to an increase of the hydroxy acid concentration. After two hours of heat treatment at 220 °C, 90 % of the carbohydrates were degraded, coupled with a high carbon conversion efficiency of 32 % based on the formation of lactic acid and glycolic acid, of which the concentrations increased by 51 and 73 %, respectively.
Bioresource Technology Reports,
Volume 19, 2022, 101148, ISSN 2589-014X
Roland Nagl, Sandrina Stocker, Patrick Zimmermann and Tim Zeiner
This work examines the mass transfer in reactive liquid-liquid systems applying the dynamic concentration gradient theory (CGT). The CGT is based on a square gradient approach delivering an expression for the Gibbs energy of an inhomogeneous system as basis for the mass transfer in a two-phase system. For this work, the CGT was combined for the first time with a reaction kinetics model to model the reactive mass transfer. The model was validated by experiments. As model reaction the reversible diacetone alcohol formation in a water-toluene system was chosen. To parameterize the Gibbs excess energy model, phase equilibria were measured and furthermore, the predictive power of the model to calculate interfacial tension in equilibrium was also checked by own experiments. To analyze the mass transfer in liquid-liquid systems the model prediction was compared to experimental data from Nitsch-cell experiments. It was found that the model predictions are in excellent agreement to the forward reaction predictions as well as to the backward reaction.
Adrian Drescher and Marlene Kienberger
In today’s linear economy, waste streams, environmental pollution, and social–economic differences are increasing with population growth. The need to develop towards a circular economy is obvious, especially since waste streams are composed of valuable compounds. Waste is a heterogeneous and complex matrix, the selective isolation of, for example, polyphenolic compounds, is challenging due to its energy efficiency and at least partially its selectivity. Extraction is handled as an emerging technology in biorefinery approaches. Conventional solid liquid extraction with organic solvents is hazardous and environmentally unfriendly. New extraction methods and green solvents open a wider scope of applications. This research focuses on the question of whether these methods and solvents are suitable to replace their organic counterparts and on the definition of parameters to optimize the processes. This review deals with the process development of agro-food industrial waste streams for biorefineries. It gives a short overview of the classification of waste streams and focuses on the extraction methods and important process parameters for the isolation of secondary metabolites.
8th Regional Symposium on Electrochemistry of South-East Europe together with the
9th Kurt Schwabe Symposium, 11−15 July 2022, TU Graz
RSE SEE8 was attended by 152 researchers and scientists from 23 countries. The conference days started with plenary lectures by internationally renowned scientists and included nine sessions with 15 keynote lectures on the topics:
Abstract book ISBN: 978-3-85125-907-0
Sigrid Wolf, Michaela Roschger, Boštjan Genorio, Mitja Kolar, Daniel Garstenauer, Brigitte Bitschnau and Viktor Hacker
In this study, Ag-MnxOy/C composite catalysts deposited on reduced graphene oxide (rGO) and, for the first time on N-doped graphene oxide (NGO), were prepared via a facile synthesis method. The influence of the carbon support material on the activity and stability of the oxygen reduction reaction (ORR) and on the tolerance to ethanol in alkaline medium was focused and investigated. The physicochemical properties of the Ag-MnxOy/C catalysts were analyzed by X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), Brunauer–Emmett–Teller (BET) method, atomic absorption spectroscopy (AAS), inductively coupled plasma-mass spectrometry (ICP-MS), and thermogravimetric gas analysis (TGA). Electrochemical characterization was performed by rotating disk electrode (RDE) experiments. The results show that the active manganese species MnO2 was assembled as nanorods and nanospheres on rGO and NGO, respectively. Ag was assumed to be present as very small or amorphous particles. Similar redox processes for Ag-MnxOy/rGO and Ag-MnxOy/NGO were examined via cyclic voltammetry. The Ag-MnxOy/rGO resulted in a more negative diffusion limiting current density of −3.01 mA cm−2 compared to Ag-MnxOy/NGO. The onset potential of approximately 0.9 V vs. RHE and the favored 4-electron transfer pathway were independent of the support material. Ag-MnxOy/NGO exhibited a higher ORR stability, whereas Ag-MnxOy/rGO showed a better ethanol tolerance.
Catalysts 2022, 12 (7), 780.
B. Stoppacher, T. Sterniczky, S. Bock, V. Hacker
Chemical Looping Hydrogen processes among others, show an outstanding potential for the decentralized conversion of biogas into high-purity hydrogen. For the first time, a 10 kWth fixed-bed chemical looping system has been coupled directly to a 3 MWth biogas digester in the southern region of Austria in the scope of the Austrian research project Biogas2H2. This experimental lab system resembles a blueprint for a potential future industrial system design. A comprehensive parameter study pointed out the influence of relevant process parameters (temperature, O/R ratio, reduction time, steam quantity in oxidation) on hydrogen purity and process efficiency. At the optimal operating point (850 °C, O/R 1.2), the process efficiency was comparable to the utilization of synthetic biogas in previous investigations within a deviation of 2.9%. Sulfuric compounds were isolated before entering the chemical looping system in order to avoid harmful contamination of the product hydrogen and performance loss, as investigated in preliminary experiments.
The generated hydrogen was characterized online by ppm-range gas analysis and exhibited a product gas quality of up to 99.998%, with residual CO and CO2 as only contaminants. The fulfillment of the carbon mass balance within a mean deviation of 9% proved the correct quantification. The results indicate that coupling fixed-bed chemical looping systems to biogas plants enables the production of a fuel cell grade hydrogen and a sufficient process efficiency in upgrading local available biogenic and agricultural residuals to high-purity hydrogen.
At this year's DocDays VT, a total of 18 research proposals from different areas of chemical and process engineering were presented. In addition, five presentations as well as seven posters by senior PhD students showed remarkable results. Congratulations to Philipp Rosenauer (Best Poster Award) and Carina Waldner (Best Presentation Award). As keynote speaker, Christian Witz (SimVantage) gave insights into the simulation of bioreactors and the difficulties of founding a start-up. The mini-conference ended in a relaxed and summery way with a barbecue, supported by members of STV VT.
Book of Abstracts
The next DocDays 2023 will take place on July 3, 2023 (scheduled); we are already looking forward to this interesting event!
Wolfgang Bauer, Viktor Hacker, Carina Waldner (Best Presentation Award) and Johannes Khinast © TU Graz
S. Bock, M. Pauritsch, S. Lux, V. Hacker
The potential of the extremely low-cost alternative of energy and hydrogen storage in the form of natural iron ores has been extensively studied and evaluated both theoretically and experimentally.
Natural iron ores as storage materials are advantageous because the specific costs are an order of magnitude lower compared to synthetic iron oxide-based materials.
For this purpose, regionally available siderite, a carbonate-bearing iron ore, with low reaction temperatures and high storage capacity was investigated in comparison with commercial iron ores such as ilmenite and others.
Specific storage costs are 80-150 $/MWh of hydrogen stored, based on experimental in situ tests. The experimentally determined volumetric energy storage capacity for the bulk material was 1.7 and 1.8 MWh/m3 for hydrogen and heat release, respectively. The raw siderite ore was stable in in situ life tests for 50 consecutive cycles at operating temperatures of 500-600 °C.
The low material price combined with reasonable storage capacity results in very low specific storage costs of 0.075 $/kWh and 0.08-0.15 $/kWh for heat and hydrogen storage, respectively.
Energy Conversion and Management, Elsevier 2022
Maximilian Neubauer, Thomas Wallek, Susanne Lux
One of the most common techniques for separating azeotropes and close-boiling mixtures is extractive distillation, where the relative volatility of the components to be separated is altered by adding an entrainer. In recent years, deep eutectic solvents have emerged as a new class of entrainers in extractive distillation. Similar to the related class of ionic liquids, deep eutectic solvents combine the high separation capability of solid salts with the simple handling of liquids, additionally exhibiting low to negligible vapour pressures and non-flammability. Compared to ionic liquids, deep eutectic solvents offer advantages in terms of toxicity issues but also solvent costs. In this review, the current state of research regarding deep eutectic solvents in extractive distillation spanning from vapour-liquid- equilibrium measurements and thermodynamic modelling of the corresponding systems to general entrainer feasibility considerations and process simulations is presented and critically evaluated. Additionally, future prospects and comments on unresolved issues are provided.
Chemical Engineering Research and Design 184 (2022) 402-418
For the project ‘On-site Biogas Utilization for Decentralized Hydrogen Production (Biogas2H2)’, the project team was awarded the Sustainability Award 2022, field of action Regional Cooperation, 3rd place by the Federal Ministry of Education, Science and Research (BMBWF - BM Polaschek) and the Federal Minister for Climate Action, Environment, Energy, Mobility, Innovation and Technology (BMK - BM Gewessler). on June 13, 2022 at the Technical Museum Vienna.
TU Graz PURE
Thomas Pichler received for his PhD thesis with the title “ Processing of Lignin: Development of Precipitation and Modification Processes” the Mondi/Heinzel/SAPPI award in the category Pulping Process (including utilization of side streams from the pulping process). Thomas Pichler developed basics for the absorption of CO2 in NaOH, which was the basis for the development of an air lift reactor for lignin precipitation and isolation. He received the price during the Pulp& Biorefinery conference on 24th of May 2022 in Graz.
During the Long Night of Research at the campus “Neue Technik” (Graz University of Technology), the working group for Chemical Reaction Engineering, headed by Susanne Lux, represented a research focus in cooperation with the student representative Chemical Engineering.
To show and explain the different operation modes in reactors for gas-liquid reaction to many visitors, the demonstration model of the Taylor Couette Disc Contactor (TCDC) and the Taylor Couette Reactor was used. During operation, the stabilized flow regime in the Taylor Couette Disc Contactor, which was developed at the CEET, was shown to the visitors. Furthermore, different possible operation modes in the TCDC, for example the chemisorption of carbon dioxide for the purification of industrial flue gas, were explained. Due to the clarity of the process and additional information from the student representatives, young visitors were given an understanding of the research focus of the working group and also the study of chemical engineering in order to attract new students to the study of chemical engineering.
Demonstration model of the Taylor Couette Disc Contactor and the Taylor Couette Reactor with (from left to right) Alexandra Hutter (student representative Chemical Engineering), Rafaela Greil (CEET) and Peter Holzmann (student representative Chemical Engineering) at the Long Night of Research 2022 at Graz University of Technology
During the Long Night of Research at Graz University of Technology, the research group of fuel cells at the Institute of Chemical Engineering and Environmental Technology, headed by Prof. Viktor Hacker, gave insights into the topics of hydrogen and fuel cells as part of the ongoing international networking project H2GreenTECH.
Using the demonstration model built as part of the H2GreenTECH project, the environmentally friendly production, storage and use of hydrogen as a fuel instead of fossil fuels was vividly explained to many visitors. The generation of renewable energy by photovoltaic cells and its further use for the production of green hydrogen by an electrolyser was demonstrated. Hydrogen storage and easy energy recovery (whenever needed) through a fuel cell were also demonstrated. By showing the demonstration model, young visitors were also able to get excited about hydrogen technology. Through the distribution of promotional materials (bags, mugs, notebooks), the awareness gained about renewable energy and the environment will be remembered by the visitors for a long time through daily use.
Information table on the energy cycle of hydrogen with the CEET team (from left to right: Mario Kircher, Prof. Viktor Hacker, Michaela Roschger, Sigrid Wolf, Karin Malli) at the Long Night of Research 2022 at TU Graz. Presentation of the demo test rig (right).
This work demonstrates how to apply the Theory of Inventive Problem Solving (Russian acronym TRIZ) on two industrial-scale case studies. The first case study addresses processing of mineral metal carbonates, which is characterized by high CO2 emissions and high energy demand. As solver strategy a novel reductive pathway is suggested. The second case study refers to biobased industrial processes, which discharge aqueous effluents with unexploited carboxylic acid loads. Reactive separations are proposed to isolate the carboxylic acids. In both solver strategies, chemical reactions adopt a central role.
Chemie Ingenieur Technik (2022)
Fabian Zapf, Thomas Wallek
This work demonstrates a case-study to create machine-learning based process models from process data, which are connected into an overall process flowsheet and provide a high level of numerical stability for further multi-objective optimization. The used models are black-box and gray-box models, which are further compared to the proven LP approach. The proposed methodology is demonstrated using real- world measurement data from a refinery, involving a distillation unit, a hydrotreater, a reformer and an ethylene plant. The developed unit models are connected into an overall process flowsheet, which is solved by a sequential-modular approach and optimized in view of maximizing production margin and minimizing CO2 -emissions. This work points out that the combination of engineering knowledge with data-driven techniques enables the incorporation of indirect information for process units, e.g., the crude oil composition vector for downstream units, leveraging the prediction performance of the unit models, compared to models not involving this information.
Computers and Chemical Engineering 162 (2022) 107823
Sascha Kleiber, Astrid Loder, Matthäus Siebenhofer, Andreas Böhm, Susanne Lux
Industrial CO2 emission mitigation necessitates holistic technology concepts; especially in high-emission industrial sectors like the iron and steel industry. A novel direct reduction technology with hydrogen reduces CO2 emissions in iron production from siderite ore by more than 60 %. Subsequent valorization of the process gas, consisting of unconverted hydrogen, carbon monoxide, and CO2, by catalytic hydrogenation to methane and methanol completes the technology concept. This route gives access to CO2 emission-lean iron production from siderite ore, fossil-free methane and methanol synthesis, and thus, improved energy density of the energy carrier hydrogen.
Chem. Ing. Tech.2022,94, No. 5, 701–711
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
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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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