81. Modelling-assisted optimisation of hemicellulose-derived monosaccharide valorization : dissertationAna Jakob, 2025, doctoral dissertation Abstract: Hemicellulose, one of the key components of lignocellulosic biomass, and its sugar monomers offer significant potential as a substrate for producing value-added platform chemicals. With both pentoses (xylose and arabinose) and hexoses (glucose, galactose, and mannose), the conversion of hemicellulose can yield various products including furfural, hydroxymethylfurfural (HMF), and levulinic acid. This doctoral thesis investigates the dehydration of various hemicellulose-derived monosaccharides, utilizing catalyst-free systems, as well as homogeneous and heterogeneous catalysts, in both aqueous and organic solvents. Monosaccharide conversion was evaluated in a catalyst-free aqueous solution at temperatures ranging between 130 – 190 °C. Conducting dehydration reactions under simple, hydrothermal conditions highlighted the differences in the reactivity of individual monosaccharides. Experimental data from extensive activity testing enabled the development of accurate kinetic models. Aiming at the optimization of reaction parameters relevant to the post-Organosolv production of furanics and levulinic acid, sulfuric and formic acid were introduced into the reaction system as homogeneous acid catalysts. Reaction kinetics of acid catalysed conversion using sulfuric and formic acid indicated a significant reduction in the activation energy of ketose dehydration. In addition, the addition of both acids enhanced the dehydration rates and promoted the conversion of HMF towards levulinic acid due to its low activation energies 86 – 91 kJ mol−1 and high reaction rate constants. The established kinetic model for individual saccharides was proven to be robust and able to accurately predict optimal reaction conditions for two distinct industrially relevant hemicellulose streams. In pursuit of a more sustainable and recyclable catalyst, various zeolites, specifically H-BEA, were tested. Although H-BEA exhibited excellent catalytic activity, its selectivity towards furanics remained limited in aqueous media. The low activation energy for HMF rehydration facilitated the formation of levulinic acid even at a moderate reaction temperature of 165 °C. Notably, the addition of THF as an organic solvent in combination with H-BEA, drastically improved the product selectivity towards furanics, particularly furfural. In addition to H-BEA zeolite, various types of zeolites with different Si/Al ratios were studied. Catalyst characterization revealed a strong correlation between catalytic activity and acidity. The addition of THF resulted in 90 mol % of furfural after only 30 min, demonstrating an exponential increase in dehydration rates and a decrease in activation energies. This zeolite-THF system was therefore applied for tandem reactions involving both xylose dehydration and furfural hydrogenation. The addition of metallic active sites via a Ni/H-BEA catalyst, and a hydrogen atmosphere, resulted in the catalytic hydrogenation of xylose to tetrahydrofurfuryl alcohol. Adjusting reaction temperatures allowed the production of secondary hydrogenated (2-methylfuran and 2-methyltetrahydrofuran) and dehydration products (tetrahydropyran), while the addition of water as a co-solvent with THF resulted in the complete inhibition of dehydration reactions and the selective formation of xylitol. Through a systematic study of reaction conditions and the development of comprehensive kinetic models, this work provides an in-depth investigation of monosaccharide dehydration. This doctoral thesis represents a comprehensive study to systematically investigate both catalytic and non-catalytic dehydration of five relevant monosaccharides, providing a methodical kinetic modelling approach that addresses the challenges associated with the complexity related to hemicellulose conversion.
Keywords: hemicellulose, monosaccharides, kinetic modelling, furanics, catalysis, dissertations
Published in RUNG: 19.02.2025; Views: 556; Downloads: 12
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86. Orography‐induced atmospheric small‐scale waves during Bora using lidar observations and numerical simulationsLonglong Wang, Marija Bervida, Samo Stanič, Luca Patruno, Wenjun Dong, Daru Chen, 2025, original scientific article Abstract: Atmospheric flow of cold air over mountain barriers in the Alpine region often gives a rise to
strong and gusty downslope wind, Bora. Such flows are often accompanied by atmospheric waves, generated by
the flow passing an elevated barrier. Such phenomenon can only rarely be observed visually and can generally
not be reliably reproduced by simplified numerical models. Orography‐induced atmospheric small‐scale waves
were experimentally observed on 25 January 2019 during a Bora outbreak in the Vipava valley, Slovenia. A
vertical scanning lidar, positioned at the lee side of the Trnovski gozd mountain and a fixed direction lidar, 5 km
apart in the Vipava valley, were used to characterize the density field. The flow exhibited a stationary jump after
the mountain ridge and, superimposed, an oscillatory flow pattern. High‐resolution numerical simulations
complemented the observations and supported experimental results on the flow periodicity but also on the wave
structures and propagation characteristics.
Keywords: Bora, wind, lidar, numerical simulation, Vipava valley, atmospheric waves
Published in RUNG: 18.02.2025; Views: 420; Downloads: 5
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88. Outreach, education, and communication initiatives at the Pierre Auger ObservatoryV. Scherini, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2024, published scientific conference contribution Abstract: The Pierre Auger Collaboration has a long tradition of outreach that engages a wide range of people of all ages worldwide. In Malargüe, Argentina, the heart of the Pierre Auger Observatory, the Visitor Center offers a permanent interactive exhibition. Every November Collaboration meeting, we organize a Science Fair where Argentinian students from across the country can present their works and talk with the scientists at the site, motivating youngsters to pursue a career in Science. We also participate in the local parade, commemorating the foundation of Malargüe. We have developed numerous activities and interactive tools, including a 3-D event display. We have an open data policy and share them according to FAIR principles. Recently, we joined the International Masterclasses within the International Particle Physics Outreach Group, using a framework similar to the ATLAS and CMS Collaborations. In this contribution, we summarize all of our Outreach activities.
Keywords: ultra-high-energy cosmic rays, Pierre Auger Observatory, outreach, education, communication, Auger visitor center, Auger science fair, open data policy, FAIR principles, International Particle Physics Outreach Group, International Masterclasses
Published in RUNG: 17.02.2025; Views: 417; Downloads: 6
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89. Infantilna percepcija sveta u Cankarevom romanu Kuća Marije pomoćniceSara Vukotić, 2019, published scientific conference contribution Abstract: Ovaj rad se zasniva na tumačenju infantilne percepcije sveta u Cankarevom romanu Kuća Marije pomoćnice koja je interpretativno interesantna stoga jer izneverava konvencionalni horizont očekivanja. Suštinska egzistencijalna pitanja poput života, smrti, slobode, te odnosa prema drugome i drugosti propuštena su kroz vizuru deteta, te je znakovito pratiti kako se pojam dečijeg razvija u romanu. S tim u vezi važno je napomenuti I uticaj porodičnog modela na formiranje ličnosti, pri čemu se u romanu može primetiti njegovo narušavanje I niz posledica koje takvo narušavanje izaziva kod dece, aktivirajući izrazito pesimistično poimanje sveta. Tema bolesti takođe će u radu zadobiti važno mesto u cilju rasvetljavanja infantilnog pogleda na svet.
Keywords: infantilno, život, smrt, sloboda, bolest, porodica, Ivan Cankar, roman
Published in RUNG: 17.02.2025; Views: 386; Downloads: 0
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