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:
Link to TU Graz SciPix: https://www.tugraz.at/en/research/research-at-tu-graz/tu-graz-scipix/
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
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 https://doi.org/10.1016/j.biteb.2022.101148.
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.