1. Catalytic hydro(deoxy)genation of furfural and modelling of its reaction kinetics : dissertationRok Šivec, 2024, doktorska disertacija Opis: In recent decades, there has been a growing interest in producing biofuels and biochemicals from renewable sources. Furfural stands as one of the ligno(hemi)cellulosic biomass derived platform chemical, which can be transformed into numerous value-added products.
The goal of this PhD was to systematically study hydrotreatment reactions of furfural under varying operating conditions and to gain insights into the reaction mechanism and kinetics. An extensive experimental and computational study of hydrogenation, hydrodeoxygenation, oligomerisation and etherification of furfural in a three-phase batch reactor was performed. The goals were divided into three consecutive objectives.
In the first part, hydrotreatment of furfural over Pd/C catalyst under various reaction conditions, including the solvent selection (solventless conditions, tetrahydrofuran, isopropanol), atmosphere (nitrogen, hydrogen), temperature (100–200 °C), pressure (25–75 bar) and stirring speed, was studied. A reaction pathway network and a micro-kinetic model were developed, incorporating thermodynamics (hydrogen solubility), mass transfer, adsorption, desorption, and surface reactions. These phenomena and their contribution to the surface coverages, TOF’s and global reaction rates were studied. The hydrogen presence on the catalyst surface was found to influence the main reaction pathway, leading to ring, aldehyde group or full hydrogenation.
In the second part, various monometallic catalysts (Pd/C, Pt/C, Re/C, Ru/C, Rh/C, Ni/C, Cu/C) were tested at 100 -200 °C with 60 bar of hydrogen and tetrahydrofuran as solvent. A generalized reaction pathway network was developed. H2 temperature-programmed reduction (H2-TPR) and CO temperature-programmed desorption (CO-TPD) were conducted, and a regression analysis of the results was subsequently performed by numerical modelling and optimisation. The obtained adsorption and desorption kinetic parameters for active metallic sites were further used in a generalized micro-kinetic model, applicable to all tested catalysts. Pd/C exhibited high activity and non-selective hydrogenation of furfural, while other catalysts showed selective aldehyde group hydrogenation followed by deoxygenation, consistent with density functional theory (DFT) calculations. Ru/C uniquely produced 2 methyltetrahydrofuran and ring-opening products at 200 °C. In silico optimization of reaction conditions for promising catalysts ((Pd/C, Pt/C, Re/C, Ni/C) aimed to maximize the yield of the target product.
In the third part, the influence of support on catalytic activity was studied. Hydrotreatment of furfural over Pd/Al2O3, Pd/SiO2, Ru/Al2O3, Ru/SiO2, Ni/Al2O3, and Ni/SiO2 was performed between 150 - 200 °C, using 60 bar of hydrogen and tetrahydrofuran as solvent. The strength and rate of adsorption and desorption to/from acidic, metallic and interface site structures were determined, using H2-TPR, CO-TPD and NH3-TPD and subsequent regression analysis of the results by numerical modelling and optimisation. The resulting parameters were sequentially used in the generalized micro-kinetic model to quantify the contribution of the active metal (Ni, Pd, or Ru), support (Al2O3 or SiO2), interphase sites and their relationship on catalyst activity and selectivity. Evaluation of morphological and structural characteristics, adsorption/desorption and intrinsic reaction kinetics has indicated that the coverage of acidic sites (on alumina or silica) facilitated yielding ring hydrogenation and inhibited deoxygenation, decarbonylation and cyclic compound opening. The rates for aromatics or aldehyde functional groups were, nonetheless, affected in a different order.
The used and developed methods and findings of this PhD offer useful guidelines for transforming furfural into high-value chemicals through catalytic hydrotreatment, with significant implications for future research and industrial applications.
Ključne besede: lignocellulosic biomass, furfural, catalytic hydrogenation, micro-kinetic mass transfer model, reaction kinetics, first-principle methods, furfuryl alcohol, tetrahydrofurfuryl alcoholv, dissertations
Objavljeno v RUNG: 08.11.2024; Ogledov: 315; Prenosov: 4
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2. Negative pragmatic transfer in bilinguals : cross‑linguistic influence in the acquisition of quantifiersGreta Mazzaggio, Penka Stateva, 2024, izvirni znanstveni članek Opis: Building on the cross-linguistic variability in the meaning of vague quantifiers, this study explores the potential for negative transfer in Italian-Slovenian bilinguals concerning the use of quantificational determiners, specifically the translational equivalents of the English “many”, that is the Slovenian "precej" and "veliko". The aim is to identify relevant aspects of pragmatic knowledge for cross-linguistic influence. The study presents the results of a sentence-picture verification task in which Slovenian native speakers and Italian-Slovenian bilinguals evaluated sentences of the form "Quantifier X are Y" in relation to visual contexts.
The results suggest that Italian learners of Slovenian, unlike Slovenian native speakers, fail to distinguish between "precej" and "veliko". This finding aligns with the negative transfer hypothesis. The study highlights the potential role of pragmatic knowledge in cross-linguistic transfer, particularly in the context of vague quantifiers.
Ključne besede: quantification, cross-linguistic differences, pragmatics, semantics, negative transfer
Objavljeno v RUNG: 20.08.2024; Ogledov: 838; Prenosov: 6
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4. Modulation of charge transfer exciton dynamics in organic semiconductors using different structural arrangementsCristian Soncini, Abhishek Kumar, Federica Bondino, Elena Magnano, Matija Stupar, Barbara Ressel, Giovanni De Ninno, Antonis Papadopoulos, Efthymis Serpetzoglou, Emmanuel Stratakis, Maddalena Pedio, 2023, izvirni znanstveni članek Opis: In devices based on organic semiconductors, aggregation and inter-molecular interactions play a key role in affecting the photo-physical and dynamical carrier properties of the material, potentially becoming a limiting factor to achieving high efficiency. As a consequence, a detailed understanding of the interplay between the film molecular structure and the material properties is essential to properly
design devices with optimized performance. Here we demonstrate how different molecular structural arrangements modulate the charge transfer (CT) dynamics in cobalt phthalocyanine (CoPc) thin films. By transient absorption spectroscopy and time-resolved photoemission spectroscopy, we study the influence of different CoPc structures on the dynamical electronic properties, the CoPc intra and inter- molecular de-excitation pathways up to 7 ns. We rationalize the ultrafast formation of triplet states in the CoPc through an electron exchange process between the single-occupied Co3dz2 orbital and p orbitals of the macrocycle, which obviate for an energetically unfavourable spin-flip. We found enhanced CT exciton lifetime in the case of the herringbone structure with respect to the brickwork one, possibly explainable by a more efficient CT exciton delocalization along the stacking axis.
Ključne besede: charge transfer, organic molecules, time resolved spectroscopies
Objavljeno v RUNG: 30.06.2023; Ogledov: 2240; Prenosov: 8
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5. Composites of transition metal dichalcogenides and topological insulators as catalytic materials for HERJelena Rmuš, Blaž Belec, Igor Milanović, Mattia Fanetti, Sandra Gardonio, Matjaž Valant, Sandra V. Kurko, 2023, izvirni znanstveni članek Ključne besede: MoS2/Bi2Se3 composites, electrocatalyst, hydrogen evolution reaction, electron transfer
Objavljeno v RUNG: 01.06.2023; Ogledov: 2431; Prenosov: 4
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6. On the Italian Molto and Tanto and the differences with the Slovenian Precej and Veliko : lecture at the 48. Incontro di Grammatica Generativa, IGG48, Dilef, University of Florence, 16. 2. 2023Greta Mazzaggio, Penka Stateva, 2023, prispevek na konferenci brez natisa Opis: The present work is based on a previous study in which Stateva and Stepanov (2017) compare speakers’ comprehension of two Slovenian m(any)-words, veliko and precej. S&S argue for a degree analysis of the two quantifiers suggesting that they are semantically equivalent but subject to different mechanisms of pragmatic enrichment. We present the results of two experiments that use the S&S protocol in order to assess i) the comprehension of two Italian translational equivalents of these m-words, namely, molti and tanti, and ii) potential crosslinguistic influence in the context of Italian-Slovenian bilingualism. Our results suggest that Italian m-words have the same numerical bounds even in direct competition in contrast to their Slovenian counterparts. Italian L2 speakers of Slovenian fail to differentiate between the two m-words in Slovenian which suggests that this aspect of L2 acquisition is subject to negative transfer.
Ključne besede: amount quantifier, Italian, bilingualism, negative transfer, pragmatic enrichment
Objavljeno v RUNG: 27.03.2023; Ogledov: 2110; Prenosov: 0
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8. Van der Waals heterostructuresVadym Tkachuk, doktorska disertacija Ključne besede: Graphene, hexagonal boron nitride, PDI8-CN2, organic semiconductor, heterostructure, charge transport, electronic properties, 2D crystal, 2D crystal transfer, tunneling.
Objavljeno v RUNG: 24.10.2022; Ogledov: 2429; Prenosov: 91
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10. Organometallic sodium carbide for heat transfer applications: A thermal lens studyMohanachandran Nair Sindhu Swapna, Sankararaman S, 2020, izvirni znanstveni članek Opis: The search for excellent heat transfer fuids necessitates the development of novel nanofuids. The paper is the frst report revealing the potential of sodium carbide (Na2C2) nanoparticle for heat transfer and thermal shielding applications. For this,
Na2C2 is prepared from the porous carbon matrix of Aloe vera leaves by hydrothermal method. The morphological changes on hydrothermal treatment and the thermal stability are analyzed by Field Emission Scanning Electron Microscopy and Thermogravimetry. The X-ray difraction analysis reveals the formation of sodium
carbide, which is confrmed by Fourier transform infrared, Ultraviolet–Visible–Near Infrared, and Raman spectroscopic analyses. The spectroscopic study of the sample synthesized shows indirect bandgap energy of 1.58 eV. The thermal difusivity
of Na2C2 nanofuid, determined by the single-beam thermal lens technique, exhibited 87 % enhancement for the base fuid, suggesting its potential in heat transfer applications.
Ključne besede: Aloe vera, Heat transfer, Organometallic, Sodium carbide, Thermal
lens
Objavljeno v RUNG: 04.07.2022; Ogledov: 1892; Prenosov: 0
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