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Opis: Ena izmed glavnih onesnaževal v odpadnih vodah so strupene organske spojine, katerih količina se z industrijskim razvojem nenehno povečuje. Najbolj nevarna so tako imenovana zaskrbljujoča onesnaževala (CEC – Contaminants of Emerging Concern), med katerimi so najpogostejših farmacevtski izdelki in izdelki za osebno nego. Za učinkovito odstranjevanje le-teh se raziskave osredotočajo na napredne oksidacijske procese (Advanced Oxidation Processes – AOP), ki s pomočjo katalizatorjev in oksidantov organska onesnaževala oksidirajo v ogljikov dioksid, vodo in mineralne kisline. Magistrska naloga se nanaša na proučevanje eno, dvo in trikovinskih katalizatorjev na silikatnem nosilcu. Kovine, ki smo jih proučevali, so bile baker, mangan in železo. Katalizatorji so bili sintetizirani na Odseku za anorgansko kemijo in tehnologijo na Kemijskem inštitutu. Katalizatorje smo najprej ovrednotili z osnovnimi karakterizacijskimi metodami, kot so rentgenska difrakcija (XRD – X-Ray Diffraction), dušikova fizisorpcija in vrstična elektronska mikroskopija (SEM – Scanning Electron Microscopy). Ugotovili smo, da imajo višjo vsebnost kovin skoraj vsi kalcinirani katalizatorji v primerjavi z ekstrahiranimi in kalciniranimi katalizatorji, kar lahko pripišemo ekstrakcijskemu postopku, med katerim se najverjetneje odstrani določeno množino kovin iz katalizatorjev. Postopek priprave bistveno ne vpliva na specifično površino, velikost por in volumen por katalizatorjev. Pri kalciniranih katalizatorjih, ki vsebujejo Cu, je le-ta prisoten v obliki CuO. Katalitske teste sem izvedla na dveh modelnih onesnaževalih iz skupine CEC in sicer na kumarinu (Fenton in foto-Fenton AOP) in glifosatu (Fenton AOP). Ugotovila sem, da so v primeru obeh uporabljenih modelnih onesnaževal najbolj učinkoviti dvokovinski katalizatorji in sicer pri kumarinu katalizator s Cu in Mn ter pri glifosatu katalizator s Cu in Fe. Pri kumarinu katalizator s Cu in Mn kaže tudi na fotokatalitsko aktivnost pri obsevanju z vidno svetlobo. Prav tako sem ugotovila, da so tako kot pri kumarinu tudi pri glifosatu bolj učinkoviti kalcinirani katalizatorji v primerjavi z ekstrahiranimi in kalciniranimi katalizatorji. To lahko pripišemo višji vsebnosti kovin ali/in prisotnosti Cu specij v obliki CuO v kalciniranih katalizatorjih. To ugotovitev bi bilo potrebno v nadaljevanju podrobneje raziskati.
Ključne besede: čiščenje odpadnih voda, napredni oksidacijski procesi, heterogena kataliza, katalizatorji na silikatnem nosilcu, glifosat, kumarin
Objavljeno v RUNG: 11.09.2024; Ogledov: 753; Prenosov: 13
Celotno besedilo (2,43 MB)

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: 1781; Prenosov: 5
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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: 2753; Prenosov: 27
Celotno besedilo (11,05 MB)
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Opis: 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.
Ključne besede: SnO2, zeolite, SnO2-clinoptilolite composite, photocatalysis, solar light, methylene blue removal, wastewater treatment
Objavljeno v RUNG: 25.02.2020; Ogledov: 4017; Prenosov: 135
Celotno besedilo (3,50 MB)

Opis: Manganese plays an important role in redox catalysis using zeolites as inorganic support materials, but the formation of the preferred redox manganese species (framework or extraframework) is still not well understood. Herein, the influence of the amount of manganese together with conventional and microwave-assisted hydrothermal synthesis paths on the formation of manganese species within the zeolite silicalite-1 (S-1) with MFI structure was investigated. It was found out that both synthesis procedures led to the formation of framework and extraframework manganese species, but in different molar ratios. However, the conventional synthesis procedure with all Mn/Si molar ratios generates more framework Mn in comparison to the microwave procedure. Additionally, the diminution of the zeolite crystals to nanoscale from 100 to 200 nm was achieved via the conventional procedure for the first time. UV–vis, Raman, and X-ray absorption spectroscopic analyses revealed different local environments of manganese: Mn3+ incorporated into the silicalite-1 framework as “framework manganese” and Mn2+/3+ present as “extraframework manganese” (Mn2O3, Mn3O4). TEM reveals the presence of Mn3O4 nanorods. Both framework manganese and extraframework manganese exhibit good catalytic activity for styrene epoxidation. Catalytic results suggest that, in oxidation reactions of hydrocarbons, framework manganese is more active at lower Mn contents (Mn/Si < 0.015), whereas extraframework manganese is more active at higher loadings (Mn/Si > 0.015).
Ključne besede: MnS-1 Nanocrystals, Mn XANES, EXAFS, zeolites, microwave-assisted hydrothermal synthesis
Objavljeno v RUNG: 06.05.2019; Ogledov: 4254; Prenosov: 0
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