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1.
XAS analysis of bifunctional Ni/ZSM-5 catalysts
Iztok Arčon, Hue-Tong Vu, Goran Dražić, Janez Volavšek, Gregor Mali, Nataša Zabukovec Logar, Nataša Novak Tušar, 2024, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: In a bifunctional Ni/ZSM-5 zeolite type catalyst, catalytic properties are usually tuned via varying Al and Ni contents [1]. Here we present a systematic structural study of the Ni/ZSM-5 materials by Ni K-edge XANES and EXAFS analyses, to monitor the changes of local structure and chemical state of Ni species in the catalysts as a function of Al and Ni content. A series of Ni/ZSM-5 type zeolites with different Al to Si and Ni to Si molar ratios were synthesized by a “green”, template free technique [2]. With a combination of XAS, XRD and TEM we resolved the changes in the local environment of Ni species induced by the different Al contents in the Ni/ZSM-5 catalysts. Ni species in Ni/ZSM-5 exist as NiO nanocrystals and as charge compensating Ni2+ cations. The Ni K-edge XANES and EXAFS results enabled the quantification of Ni-containing species. At a low Al to Si ratio (nAl/nSi < 0.04), the NiO nanoparticles predominate in the samples and account for over 65% of Ni phases. However, NiO is outnumbered by Ni2+ cations attached to the zeolite framework in ZSM-5 with a high Al to Si ratio (nAl/nSi = 0.05) due to a higher number of framework negative charges imparted by Al. The obtained results show that the number of highly reducible and active NiO nanocrystals is strongly correlated with the framework Al sites present in Ni/ZSM-5 zeolites.
Ključne besede: Ni EXAFS, XANES Ni/ZSM-5 catalyst
Objavljeno v RUNG: 05.07.2024; Ogledov: 214; Prenosov: 1
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2.
The influence of polyphenolic compounds on anaerobic digestion of pepper processing waste during biogas and biomethane production
Gregor Drago Zupančič, Anamarija Lončar, Jasmina Ranilović, Drago Šubarić, Mario Panjicko, 2024, izvirni znanstveni članek

Opis: Pepper processing waste has the potential to be used as a substrate in the process of anaerobic digestion, but because of its high polyphenol content, certain limitations are expected. During the determination of the biodegradability of pepper samples, a biogas potential of 687 L/kg DM was observed, as well as a biomethane potential of 401 L/kg DM. While both the testing of biodegradability and the process in the pilot scale progressed, it was observed that total polyphenol content in both cases decreased. Also, as far as individual polyphenols during the process in the pilot scale are concerned, it can be observed that at the end of the process no procyanidin A2, epicatechin, myricetin, and quercetin were detected. The observed concentration of the ferulic acid on the last day of the process was 0.09 μg/g. Finally, it can be concluded that the presence of polyphenols did not significantly affect the biogas potential of pepper waste. Due to its relatively stable biogas production, as far as biogas production on the pilot scale is concerned, it can be concluded that pepper processing waste has the potential to be used as a substrate for biogas production.
Ključne besede: anaerobic digestion, polyphenols, ferulic acid, procyanidins, epicatechin, myricetin, quercetin
Objavljeno v RUNG: 06.05.2024; Ogledov: 446; Prenosov: 2
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3.
Contribution of black carbon and desert dust to aerosol absorption in the atmosphere of the Eastern Arabian Peninsula
Mohamed M. K. Mahfouz, Gregor Skok, Jean Sciare, Michael Pikridas, M. R. Alfarra, Shamjad Moosakutty, Bálint Alföldy, Matic Ivančič, Martin Rigler, Asta Gregorič, Rok Podlipec, Griša Močnik, 2024, izvirni znanstveni članek

Opis: Discriminating the absorption coefficients of aerosol mineral dust and black carbon (BC) in different aerosol size fractions is a challenge because of BC's large mass absorption cross-section compared to dust. Ambient aerosol wavelength dependent absorption coefficients in supermicron and submicron size fractions were determined with a high time resolution. The measurements were performed simultaneously using identical systems at an urban and a regional background site in Qatar. At each site, measurements were taken by co-located Aethalometers, one with a virtual impactor (VI) and the other with a PM1 cyclone to respectively collect super-micron-enhanced and submicron fractions. The combined measurement of aerosol absorption and scattering coefficients enabled the particles to be classified based on their optical properties' wavelength dependence. The classification reveals the presence of BC internally/externally mixed with different aerosols. Helium ion microscopy images provided information concerning the extent of mineral dust in the submicron fraction. The determination of absorption coefficients during dust storms and non-dust periods was used to establish the absorption Ångström exponent for dust and BC. Non-parametric wind regression, potential source contribution function and back-trajectory analysis reveal major regional sources of desert dust associated with north-westerly winds and a minor local dust contribution. In contrast, major BC sources found locally were associated with south-westerly winds with a smaller contribution made by offshore emissions transported by north-easterly and easterly winds. The use of a pair of Aethalometers with VI and PM1 inlets separates contributions of BC and dust to the aerosol absorption coefficient.
Ključne besede: aerosol absorption, black carbon, mineral dust, desert dust, Arabian Peninsula
Objavljeno v RUNG: 29.02.2024; Ogledov: 823; Prenosov: 6
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4.
Insight into the interdependence of Ni and Al in bifunctional Ni/ZSM-5 catalysts by Ni K-edge XAS analysis
Iztok Arčon, Hue-Tong Vu, Goran Dražić, Janez Volavšek, Gregor Mali, Nataša Zabukovec Logar, Nataša Novak Tušar, 2023, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: Catalyst design is crucial for improving catalytic activity and product selectivity. In a bifunctional Ni/ZSM-5 zeolite type catalyst, catalytic properties are usually tuned via varying Al and Ni contents [1]. While changes in acid properties associated with Al sites are usually closely investigated, Ni phases, however, receive inadequate attention. Herein, we present a systematic structural study of Ni in the Ni/ZSM-5 materials by Ni K-edge XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure) analyses, to monitor the local structure and chemical state of Ni species in the catalysts. In combination with XRD and TEM we resolved the changes in the local environment of Ni species induced by the different Al contents of the parent ZSM-5 prepared by a “green”, template free technique [2]. Ni species in Ni/ZSM-5 exist as NiO crystals (3–50 nm) and as charge compensating Ni2+ cations. The Ni Kedge XANES and EXAFS results enabled the quantification of Ni-containing species. At a low Al to Si ratio (nAl/nSi < 0.04), the NiO nanoparticles predominate in the samples and account for over 65% of Ni phases. However, NiO is outnumbered by Ni2+ cations attached to the zeolite framework in ZSM-5 with a high Al to Si ratio (nAl/nSi = 0.05) due to a higher number of framework negative charges imparted by Al. The obtained results show that the number of highly reducible and active NiO crystals is strongly correlated with the framework Al sites present in ZSM-5 zeolites, which depend greatly on the synthesis conditions. Therefore, this kind of study is beneficial for any further investigation of the catalytic activities of Ni/ZSM-5 and other metal-modified bifunctional catalysts.
Ključne besede: Ni/ZSM-5 catalysts, Ni EXAFS, XANES
Objavljeno v RUNG: 19.09.2023; Ogledov: 1133; Prenosov: 3
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5.
In vitro tumor hypoxia imaging with fluorescent covalent organic frameworks
Tina Skorjanc, Dinesh Shetty, Damjan Makuc, Gregor Mali, Martina Bergant Marušič, Matjaž Valant, 2023, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: Hypoxia refers to a condition where cells and tissues experience low, inadequate levels of O2. While healthy tissues are typically supplied with sufficient O2 (normoxia), cancerous tissues commonly face hypoxia due to the tumor’s extraordinarily high demand for oxygen. Various fluorescent small-molecule probes have been designed for selective detection of hypoxia in living cells, but few nanomaterials have been investigated for this type of bioimaging. Herein, we prepare a fluorescent covalent organic framework (COF) with β-ketoenamine linkages and post-synthetically modify it to conjugate hypoxia-sensitive nitroimidazole moieties into its pores (NI-COF). Stacks of sheets in NI-COF observed under electron microscopy were exfoliated by ultrasonication, and dynamic light scattering measurements confirmed particle size of less than 200 nm. Thus-prepared material exhibited good stability in physiological conditions and low cytotoxicity in in vitro experiments. NI-COF also showed useful fluorescence properties with an emission peak at 490 nm (λex = 420 nm) at both neutral and mildly acidic pH levels that are characteristic of tumor tissues. Encouraged by the favorable properties of the material, we incubated HeLa cells pre-treated in either hypoxic or normoxic conditions with NI-COF. Fluorescence microscopy images demonstrated that the material was preferentially taken up by hypoxic cells, which showed higher fluorescence signal in their interior than cells cultured under normoxia conditions. It is anticipated that this study will stimulate further developments of COFs for imaging various biological conditions.
Ključne besede: hypoxia, fluorescence, covalent organic frameworks, imaging, tumor cells
Objavljeno v RUNG: 19.09.2023; Ogledov: 1136; Prenosov: 4
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6.
Utilizing structurally disordered AlMg-oxide phase in Cu/ZnO catalyst for efficient ▫$CO_2$▫ hydrogenation to methanol
Andraž Mavrič, Gregor Žerjav, Blaž Belec, Matevž Roškarič, Matjaž Finšgar, Albin Pintar, Matjaž Valant, 2023, objavljeni povzetek znanstvenega prispevka na konferenci

Ključne besede: carbon dioxide, methanol, catalysis
Objavljeno v RUNG: 15.09.2023; Ogledov: 1302; Prenosov: 4
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7.
Winning combination of Cu and Fe oxide clusters with an alumina support for low-temperature catalytic oxidation of volatile organic compounds
Tadej Žumbar, Iztok Arčon, Petar Djinović, Giuliana Aquilanti, Gregor Žerjav, Albin Pintar, Alenka Ristić, Goran Dražić, Janez Volavšek, Gregor Mali, Margarita Popova, Nataša Zabukovec Logar, Nataša Novak Tušar, 2023, izvirni znanstveni članek

Opis: A γ-alumina support functionalized with transition metals is one of the most widely used industrial catalysts for the total oxidation of volatile organic compounds (VOCs) as air pollutants at higher temperatures (280−450 °C). By rational design of a bimetal CuFe-γ-alumina catalyst, synthesized from a dawsonite alumina precursor, the activity in total oxidation of toluene as a model VOC at a lower temperature (200−380 °C) is achieved. A fundamental understanding of the catalyst and the reaction mechanism is elucidated by advanced microscopic and spectroscopic characterizations as well as by temperature-programmed surface techniques. The nature of the metal−support bonding and the optimal abundance between Cu−O−Al and Fe−O−Al species in the catalysts leads to synergistic catalytic activity promoted by small amounts of iron (Fe/Al = 0.005). The change in the metal oxide−cluster alumina interface is related to the nature of the surfaces to which the Cu atoms attach. In the most active catalyst, the CuO6 octahedra are attached to 4 Al atoms, while in the less active catalyst, they are attached to only 3 Al atoms. The oxidation of toluene occurs via the Langmuir−Hinshelwood mechanism. The presented material introduces a prospective family of low-cost and scalable oxidation catalysts with superior efficiency at lower temperatures.
Ključne besede: Iron oxide clusters, copper oxide clusters, alumina support, synergistic effect, low-temperature total catalytic oxidation, toluene, Cu, Fe XANES, EXAFS
Objavljeno v RUNG: 06.07.2023; Ogledov: 1552; Prenosov: 15
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8.
Characterization of MOS-FET dosimeters for use in the ATLAS-RadMON system : diploma seminar
Anže Pirc, 2023, raz. nal. na višji ali visoki šoli

Ključne besede: MOS-FET dosimeters, high radiation fields, ATLAS detector, ATLAS-RadMON system
Objavljeno v RUNG: 05.07.2023; Ogledov: 1108; Prenosov: 0

9.
Covalent organic frameworks for fluorescent imaging of hypoxia
Tina Škorjanc, Dinesh Shetty, Gregor Mali, Damjan Makuc, Martina Bergant Marušič, Matjaž Valant, 2023, objavljeni povzetek znanstvenega prispevka na konferenci

Ključne besede: hypoxia, covalent organic frameworks, imaging, fluorescence, post-synthetic modification
Objavljeno v RUNG: 06.06.2023; Ogledov: 1403; Prenosov: 2
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10.
Structural disorder of AlMg-oxide phase supporting Cu/ZnO catalyst improves efficiency and selectivity for ▫$CO_2$▫ hydrogenation to methanol
Andraž Mavrič, Gregor Žerjav, Blaž Belec, Matevž Roškarič, Matjaž Finšgar, Albin Pintar, Matjaž Valant, 2023, izvirni znanstveni članek

Opis: The performance of the Cu/ZnO catalyst system with the AlMg-oxide phase is studied for CO2 hydrogenation to methanol. The catalyst is prepared by thermal treatment of the hydrotalcite phase containing intimately mixed metal cations in the hydroxide form. CuO in the presence of ZnO and disordered AlMg-oxide phase gets easily reduced to Cu during the hydrogenation reaction. Its catalytic activity at relatively low Cu metal content (∼14 at.%) remains stable during 100 hours on stream at 260 °C with constant space-time yield for methanol (∼1.8 gMeOH gcat−1 h−1) and high methanol selectivity (>85 %) The improved performance is attributed to the neutralization of surface acidity, increased number of weak basic sites in the disordered phase, and lower tendency for coke formation.
Ključne besede: carbon dioxide hydrogenation, heterogenous catalysis, methanol, reducibility
Objavljeno v RUNG: 02.06.2023; Ogledov: 1357; Prenosov: 15
.pdf Celotno besedilo (1,12 MB)

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