1. Insight into the interdependence of Ni and Al in bifunctional Ni/ZSM-5 catalysts by Ni K-edge XAS analysisIztok Arčon, Hue-Tong Vu, Goran Dražić, Janez Volavšek, Gregor Mali, Nataša Zabukovec Logar, Nataša Novak Tušar, 2023, published scientific conference contribution abstract Abstract: 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.
Keywords: Ni/ZSM-5 catalysts, Ni EXAFS, XANES
Published in RUNG: 19.09.2023; Views: 733; Downloads: 3
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2. Multicomponent Cu-Mn-Fe silica supported catalysts to stimulate photo-Fenton-like water treatment under sunlightAndraž Šuligoj, Ivalina Trendafilova, Ksenija Maver, Albin Pintar, Alenka Ristić, Goran Dražić, Wael H. M. Abdelraheem, Zvonko Jagličić, Iztok Arčon, Nataša Zabukovec Logar, Dionysios D. Dionysiou, Nataša Novak Tušar, original scientific article Keywords: Magnetic catalyst, Photocatalyst, Water treatment, Sunlight, Contaminants of emerging concern, Photo-Fenton-like systems, Cu, Mn, Fe, XANES, EXAFS
Published in RUNG: 06.07.2023; Views: 1186; Downloads: 5
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3. Winning combination of Cu and Fe oxide clusters with an alumina support for low-temperature catalytic oxidation of volatile organic compoundsTadej 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, original scientific article Abstract: 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.
Keywords: Iron oxide clusters, copper oxide clusters, alumina support, synergistic effect, low-temperature total catalytic oxidation, toluene, Cu, Fe XANES, EXAFS
Published in RUNG: 06.07.2023; Views: 1031; Downloads: 13
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4. Analiza konkurenčnih izdelkov in implementacija podatkov v interno platformo podjetjaTimotej Novak, 2023, undergraduate thesis Abstract: Podjetja s pomočjo analize konkurenčnih izdelkov pridobivajo pomembne informacije o uporabljenih pristopih, rešitvah, stroškovnih ter delovnih optimizacijah pri proizvodnji, ki so se izkazale kot učinkovite pri konkurenčnih podjetjih. Problem v izbranem podjetju je predstavljala nejasna, razpršena in težko dostopna baza podatkov z rezultati analiz. Rešitev predstavlja platforma podjetja, namenjena hranjenju in deljenju podatkov, kjer se na enem mestu zbirajo podatki pridobljeni z analizo izdelkov in ostale pomembne informacije. Podatke je potrebno analizirati, filtrirati in jih implementirati v platformo. Tako imajo delavci v razvojnih oddelkih podjetja na različnih koncih sveta takojšen in pregleden dostop do koristnih informacij o posameznih izdelkih, kar jim služi za bolj učinkovit in hitrejši razvoj novih izdelkov. Namen diplomske naloge je prikazati pomembnost analize konkurenčnih izdelkov za podjetje na nenehno spreminjajočem se globalnem trgu in prikazati, kako poteka implementacija in upravljanje podatkov v spletni platformi v povezavi z analizo konkurenčnih izdelkov.
Keywords: Analiza konkurenčnih izdelkov, spletna platforma, baza podatkov, avtomobilska industrija
Published in RUNG: 03.05.2023; Views: 1281; Downloads: 19
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5. Insight into the interdependence of Ni and Al in bifunctional Ni/ZSM-5 catalysts at the nanoscaleHue-Tong Vu, Iztok Arčon, Danilo Oliveira de Souza, Simone Pollastri, Goran Dražić, Janez Volavšek, Gregor Mali, Nataša Zabukovec Logar, Nataša Novak Tušar, 2022, original scientific article Abstract: 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. 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
using Ni K-edge XANES and EXAFS analyses, complemented by XRD and TEM, to resolve 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. Ni species in Ni/ZSM-5 exist as NiO crystals (3–50 nm) 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 ¼ 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.
Keywords: Ni/ZSM-5 catalysts, zeolite, Ni XANES, EXAFS
Published in RUNG: 11.05.2022; Views: 1572; Downloads: 43
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8. SnO2-Containing Clinoptilolite as a Composite Photocatalyst for Dyes Removal fromWastewater under Solar LightAndraž Šuligoj, Jelena Pavlovič, Iztok Arčon, Nevenka Rajić, Nataša Novak Tušar, 2020, original scientific article Abstract: Due to their adsorbent, ion exchange and catalytic properties zeolites are suitable for a variety of applications. We report on the photocatalytic activity of a readily available and inexpensive natural zeolite clinoptilolite (Z) containing SnO2 (Sn-Z). The Sn-Z samples with 3–15 wt. % of Sn were prepared by using a precipitation–deposition method. Powder X-ray diffraction analysis showed that the zeolite structure was unaffected by the introduction of the Sn-phase. Diffuse reflectance UV/VIS spectra of the Sn-Z samples confirmed the presence of SnO2 and X-Ray absorption spectroscopy analyses suggested that the SnO2 particles mainly resided on the surface of the clinoptilolite, while ATR-FTIR analysis gave some clues that part of the SnO2 phase was incorporated in the pores of the zeolite. The presence of SnO2 in Sn-Z increased both adsorption capacity and photocatalytic performance which could be partially explained by higher surface area and partially with an increased negative potential of the surface. Adsorption and total degradation of methylene blue (MB) for the Sn-Z with the highest amount of Sn (15 wt.%) was about 30% and 45%, respectively, suggesting a synergetic effect between SnO2 and the clinoptilolite lattice. Reusability tests showed that these catalysts present a promising material for water purification.
Keywords: SnO2, zeolite, SnO2-clinoptilolite composite, photocatalysis, solar light, methylene blue
removal, wastewater treatment
Published in RUNG: 25.02.2020; Views: 2971; Downloads: 132
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9. In-depth structural characterization and magnetic properties ofquaternary ferrite systems Co0.5Zn0.25M0.25Fe2O4(M¼Ni, Cu, Mn, Mg)Radu-G. Ciocarlan, Iztok Arčon, Aurel Pui, Myrjam Mertens, Nataša Novak Tušar, Elena M. Seftel, Pegie Cool, 2019, original scientific article Abstract: This paper investigates the structural and magnetic properties of a mixed series of ferrites having generalformula Co0.5Zn0.25M0.25Fe2O4(M¼Ni, Cu, Mn, Mg). Insights on surface chemistry, structural andmorphological parameters are presented in order to achieve highly tuned ferrite systems with specificcharacteristics. The site occupancy of the cations in the spinel structure was determined using XAS, XRDand Raman spectroscopy. A 100% occupancy of the tetrahedral sites was observed for the Zn cations forall the samples. Co cations occupied the octahedral sites in proportion of 100% for CoeZneCu, CoeZneMg and around 80% for CoeZneNi, CoeZneMn. Ni cations were found only in the octahedral sites,while Cu 80% in the octahedral sites and Mn 60% in the octahedral sites. The cation distribution resultswere correlated with the magnetic properties data. At the same time, not only the cation distribution, butalso the particles size distribution was observed to have a great influence on magnetic and opticalproperties of the ferrites. Given the importance of the surface chemistry of the nanoparticles, XPS and FT-IR analysis were used to prove the functionalization with groups belonging to the surfactant. Moreover,the peculiar behavior of manganese in spinel structures was clarified and the origin of the multiple states(Mn2þand Mn4þ) was elucidated. Finally, parallels have been drawn between the use of different cationsin mixed ferrites in order to gain specific properties.
Keywords: FerritesMagnetic propertiesSpinel nanoparticlesX-ray absorption spectroscopyCo-precipitation
Published in RUNG: 23.10.2019; Views: 3209; Downloads: 0
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