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Nasl. z nasl. zaslona. Soavtorji: Matjaž Finšgar, Janez Zavašnik, Nataša Novak Tušar, Albin Pintar. Opis vira z dne 17. 2. 2023. Bibliografija: str. 10-12. Abstract.

Fenton and Fenton-like Advanced Oxidation Processes (AOP) have obtained large applicative use for the removal of organic pollutants from wastewater. Herein, we discuss a novel bimetal Cu-Mn porous silica-supported Fenton-like AOP catalyst with interparticle mesoporosity working under neutral pH and UV-VIS irradiation (CuMnKIL with Mn/Si = 0.01, Mn/Cu = 0.06). The photocatalyst was prepared via solvothermal synthesis (Mn incorporation into porous silica support) followed by incipient wetness impregnation (Cu loading into Mn containing porous silica support) and was tested for the decomposition of methylene blue as a model dye. Copper addition significantly reduced Mn leaching from the porous silica support (from 60 to 30 %) and functioned also as additional surface adsorption site. CuMnKIL (Mn/Si = 0.01, Mn/Cu = 0.06) showed 20 % higher adsorption and 20 % lower efficiency if compared with MnKIL (Mn/Si = 0.01) in Fenton-like AOP system, however, addition of irradiation (photo-Fenton-like system) improved efficiency of Cu/MnKIL (Mn/Si = 0.01, Mn/Cu = 0.06) for 10 % if compared to MnKIL (Mn/Si=0.01) due to the additional •OH radicals produced by the decomposition of H2O2 by the light. No synergistic effects between Cu and Mn were recorded, meaning that Cu and Mn sites were acting as separate sites, which was confirmed with AR-TEM imaging as well as UV spectroscopy studies.

Solar-powered photocatalysis has come a long way since its humble beginnings in the 1990s, producing more than a thousand research papers per year over the past decade. In this review, immobilized photocatalysts operating under sunlight are highlighted. First, a literature review of solar-driven films is presented, along with some fundamental operational differences in relation to reactions involving suspended nanoparticles. Common strategies for achieving sunlight activity from films are then described, including doping, surface grafting, semiconductor coupling, and defect engineering. Synthetic routes to fabricate photocatalytically active films are briefly reviewed, followed by the important factors that determine solar photocatalysis efficiency, such as film thickness and structure. Finally, some important and specific characterization methods for films are described. This review shows that there are two main challenges in the study of photocatalytic materials in the form of (thin) films. First, the production of stable and efficient solar-driven films is still a challenge that requires an integrated approach from synthesis to characterization. The second is the difficulty in properly characterizing films. In any case, the research community needs to address these, as solar-driven photocatalytic films represent a viable option for sustainable air and water purification.

A systematic structural study of Ni in the Ni/ZSM-5 materials is presented, which is beneficial for any further investigation of the catalytic activities of Ni/ZSM-5 and other metal-modified bifunctional catalysts.

The present study focuses on clinoptilolite (CLI)-rich natural zeolitic tuffs and their photocatalytic activity in the degradation of cationic organic dyes. CLI from different regions was tested in the photocatalytic degradation of methylene blue (MB) as a model cationic dye. The photocatalytic tests were performed at room temperature and atmospheric pressure under visible light irradiation. For all the CLI samples, the highest activity was observed at pH = 6. Total MB degradation varied between 70 and 91% (C0 = 10 mg dm–3, 0.2 g dm–3 of photocatalyst, during 300 min). It is suggested that the presence of Fe species in the studied tuffs is responsible for the photocatalytic activity. The activity increases linearly with the Fe content in the tuffs. The MB photodegradation follows the Langmuir–Hinshelwood kinetic model. The recyclability tests showed good stability and efficiency of the photocatalyst. The degradation rate decreased from 91 to 69% during three reaction cycles, indicating a promising potential of natural zeolites in the treatment of textile industry wastewater.

Crystal growth & design 19(6), 3130 - 3138 (2019). doi:10.1021/acs.cgd.8b01181, 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 frameworkand extraframework manganese species, but in different molar ratios. However, theconventional synthesis procedure with all Mn/Si molar ratios generates moreframework Mn in comparison to the microwave procedure. Additionally, thediminution of the zeolite crystals to nanoscale from 100 to 200 nm was achievedvia the conventional procedure for the first time. UV−vis, Raman, and X-rayabsorption spectroscopic analyses revealed different local environments ofmanganese: Mn$^{3+}$ incorporated into the silicalite-1 framework as “frameworkmanganese” and Mn$^{2+/3+}$ present as “extraframework manganese” (Mn$_2$O$_3$, Mn$_3$O$_4$). TEM reveals the presence of Mn$_3$O$_4$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)., Published by ACS Publ., Washington, DC

The present work is focused on the role of ZrO2 modification in the performance of CuO modified TiO2. Zirconia loading leads to formation of more resistant photocatalytic layers compared to samples modified with only copper containing species. Surface modification of mixed phase TiO2 with CuO/ZrO2 improves the degradation of Reactive blue 19 dye under simulated solar irradiation. An in-depth investigation of the catalysts showed that in case of CuO/ZrO2 modification, the covering of the TiO2 surface with zirconium containing species prevents morphological and harmful energetic changes induced by copper species formed on the rutile TiO2 phase at a higher copper loading.

The structure–property relationship of catalytic supports for the deposition of redox-active transition metals is of great importance for improving the catalytic efficiency and reusability of the catalysts. In this work, the role of alumina support precursors of Cu-Fe/Al2O3 catalysts used for the total oxidation of toluene as a model volatile organic air pollutant is elucidated. Surface characterization of the catalysts revealed that the surface area, pore volume and acid site concentration of the alumina supports are important but not the determining factors for the catalytic activity of the studied catalysts for this type of reaction. The determining factors are the structural order of the support precursor, the homogeneous distribution of the catalytic sites and reducibility, which were elucidated by XRD, NMR, TEM and temperature programed reduction (TPR). Cu–Fe/Al2O3 prepared from bayerite and pseudoboehmite as highly ordered precursors showed better catalytic performance compared to Cu-Fe/Al2O3 derived from the amorphous alumina precursor and dawsonite. Homogeneous distribution of FexOy and CuOx with defined Cu/Fe molar ratio on the Al2O3 support is required for the efficient catalytic performance of the material. The study showed a beneficial effect of low iron concentration introduced into the alumina precursor during the alumina support synthesis procedure, which resulted in a homogeneous metal oxide distribution on the support.

The conversion of the biomass-derived lipid, lignocellulosic and carbohydrate resources into renewable platform intermediates, chemicals and biofuels has been lately increasing in interest. The mechanistic reaction pathways, like hydro-deoxygenation, decarboxylation and hydrocracking, of the selected palmitic acid, as a model fatty acid, over Ni/ZSM-5 zeolite catalysts were studied. The ZSM-5 material with different Al/Si molar ratios was synthesized via a green template-free hydrothermal synthesis procedure, treated and subsequent functionalised with various Ni metal loadings. However, Ni/Al molar ratio was kept stoichiometric (Ni/Al = 0.5). The characteristic physicochemical properties of composite catalysts were studied by numerous characterization techniques, such as X-ray powder diffraction (XRD), scanning-, as well as high-resolution transmission electron microscopy (SEM/HRTEM), and X-ray photoelectron spectroscopy (XPS). NiO with an average particle size of 10–20 nm was found on ZSM-5 support. The relative Ni/Al atom fraction in Ni/ZSM-5 systems influenced their Lewis/Bronsted acidic sites, as well as the external exposed area of prepared heterogeneous structures. Furthermore, the mentioned morphological parameters affected predominant catalytic routes. Species’ production mechanism, as a consequence of Lewis/Bronsted centre weak/strong acidity, as well as their integral concentration, was proposed, mirroring the observed process kinetics, selectivity and turnover. It was demonstrated that the main obtained products were esters, aldehydes, alcohols, hydrocarbons and gases (CO2, CO…), produced by deoxygenation (e.g. decarbonylation), hydrogenation and cracking, less, though, through isomerisation.

For the photocatalytic wastewater treatment containing lower concentrations of dyes as pollutants, a suitable photocatalyst may be selected for anionic or cationic dye removal according to the photocatalyst surface charging and desired adsorption/degradation ratio. Herein, for the first time, we evaluate mesoporous silica supported TiO 2 versus mesoporous silica supported ZnO photocatalysts at neutral pH and at equal conditions. The evaluation shows that model anionic dye Reactive Blue 19 (RB19) was adsorbed onto silica supported ZnO nanoparticles at neutral pH in a much higher rate than on silica supported TiO 2 nanoparticles, even though the surfaces of ZnO and TiO 2 –silica composite catalysts were negatively charged in both cases (ca. −20 mV of zeta potential). This was ascribed to the strong positive zeta potential of pure ZnO nanoparticles at neutral pH value (ca. +37 mV) and consequently to more mixed oxide (spinel-like) ZnO/silica composite behaviour if compared to the physical mixture of oxide TiO 2 /silica composites. The highest dye adsorption (50%) and the fastest dye degradation (k app = 0.0544 min −1 at 25 °C) was observed on disordered ZnO/silica with Zn:Si molar ratio 1:1. Pure TiO 2 or silica supported TiO 2 nanoparticles were stable under UV irradiation. On the other hand, the interaction between SiO 2 and ZnO resulted in increased resistance of ZnO to photocorrosion, which was proven to be an issue in pure ZnO nanoparticles.

Au nanoparticles supported on ZrO2 enhance its surface acidic/basic properties to produce a high yield of methanol via the hydrogenation of CO2. Amorphous ZrO2-supported 0.5–1 wt.% Au catalysts were synthesized by two methods, namely deposition precipitation (DP) and impregnation (IMP), characterized by a variety of techniques, and evaluated in the process of CO2 hydrogenation to methanol. The DP-method catalysts were highly advantageous over the IMP-method catalyst. The DP method delivered samples with a large surface area, along with the control of the Au particle size. The strength and number of acidic and basic sites was enhanced on the catalyst surface. These surface changes attributed to the DP method greatly improved the catalytic activity when compared to the IMP method. The variations in the surface sites due to different preparation methods exhibited a huge impact on the formation of important intermediates (formate, dioxymethylene and methoxy) and their rapid hydrogenation to methanol via the formate route, as revealed by means of in situ DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) analysis. Finally, the rate of formation of methanol was enhanced by the increased synergy between the metal and the support.

Titanium dioxide has been widely used as an antimicrobial agent, UV-filter and catalyst for pollution abatement. Herein, surface modifications with selected transition metals (Me) over colloidal TiO2 nanopartides and immobilization with a colloidal SiO2 binder as composite films (MeTiO2/SiO2) on a glass carrier were used to enhance solar-light photoactivity. Colloidal TiO2 nanopartides were modified by Loading selected transition metals (Me = Mn, Fe, Co, Ni, Cu, and Zn) in the form of chlorides on their surface. They were present primarily as oxo-nanoclusters and a portion as metal oxides. The structural characteristics of bare TiO2 were preserved up to an optimal metal Loading of 0.5 wt%. We have shown in situ that metaloxo-nanodusters with a redox potential dose to that of O-2/O-2(center dot-) were able to function as co-catalysts on the TiO2 surface which was excited by solar-light irradiation. The materials were tested for photocatalytic activity by two opposite methods; one detecting O-2(center dot-) (reduction, Rz ink test) while the other detecting (OH)-O-center dot (oxidation, terephthaEic acid test). It was shown that the enhancement of the solar-light activity of TiO2 by the deposition of transition metal oxo-nanoclusters on the surface depends strongly on the combination of the reduction potential of such species and appropriate band positions of their oxides. The latter prevented excessive self-recombination of the photogenerated charge carriers by the nanoclusters in Ni and Zn modification, which was probably the case in other metal modifications. Overall, only Ni modification had a positive effect on solar photoactivity in both oxidation and reduction reactions.

The novelty of this work was to prepare a series of defect-rich colored TiO2 nanostructures, using a peroxo solvothermal-assisted, high-pressure nitrogenation method. Among these solids, certain TiO2 materials possessed a trace quantity of anatase–rutile heterojunctions, which are beneficial in obtaining high reaction rates in photocatalytic reactions. In addition, high surface area (above 100 m2/g), even when utilizing a high calcination temperature (500 °C), and absorption of light at higher wavelengths, due to the grey color of the synthesized titania, were observed as an added advantage for photocatalytic hydroxyl radical formation. In this work, we adopted a photoluminescent probe method to monitor the temporal evolution of hydroxyl radicals. As a result, promising hydroxyl radical formations were observed for all the colored samples synthesized at 400 and 500 °C, irrespective of the duration of calcination.

The present research reports on a successful strategy of titanium dioxide modification with carbon and zirconium, for enhanced photocatalytic activity under UV–vis irradiation. Carbon and/or zirconium modified TiO 2 nanoparticles were synthesized via sol–gel hydrothermal method. It was found that both elements positively influence important parameters for the photocatalytic activity improvement, such as crystallite size, diameter of agglomerates and surface area, summing their effects in case of co-doped sample. Moreover, carbon modification shifts the absorption edge toward larger wavelength and decreases band gap energy in opposite to zirconium, which induces blue shift and increases the band gap energy. Thus, modification with two elements at a time narrows the band gap energy of co-doped sample maintaining its high oxidation potential , which along with increased absorption of visible light leads to enhancement in visible and ultraviolet light driven photocatalytic decomposition of methylene blue. It was found that Zr,C TiO 2 sample is more efficient photocatalyst for both visible and ultraviolet light driven processes than either of the pure or single element modified TiO 2 .

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&ndash, 15 wt. % of Sn were prepared by using a precipitation&ndash, 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.

Zirconia nanomaterials were prepared by impregnation of KIL-2 type silica with 4, 8, 15 and 25 wt% of ZrO2, and were modified by sulfate groups in order to vary the type, strength and density of the active sites. The samples were characterized by X-ray powder diffraction (XRD), EDX analysis, N2 physisorption, SEM, TEM, UV–Vis spectroscopy, XPS, and thermogravimetric analysis (TGA). The acidic properties were investigated by FT-IR spectroscopy of adsorbed pyridine. The catalytic properties of ZrKIL-2 catalysts and their sulfated varieties were studied in levulinic acid (LA) esterification with ethanol or n-butanol. The sulfated materials showed significantly higher activity compared to the non-sulfated ones due to their stronger Bronsted and Lewis acid sites. It was found that the silica supported sulfated samples show different activity depending on the applied alcohol. With increasing ZrO2 content up to 15 wt% increasing catalytic activity and selectivity was observed to produce levulinate esters. A further increase of the amount of zirconia leads to a decrease in catalytic activity because of the significant decrease of ZrO2 dispersion and the structure deterioration of the catalyst. For the first time insight was provided into the relation between sulfates group leaching and zirconia dispersion.

The rate of methylene blue and terephthalic acid degradation assisted with double metal-modified catalyst (0.1 mol% Cu and 1.0 mol% Zr) was enhanced as compared with single metal-modified catalysts (0.1, 0.5 mol% Cu and 1.0 mol% Zr). The wet impregnation method was used for copper and zirconium modification of the surface of Aeroxide P25 TiO2 particles. Simultaneous loading of both metals on the surface of P25 leads to an increased specific surface area of the obtained material despite negative Cu influence. The tendency of stabilization and agglomerate size rising with the time for Cu and Zr-modified catalysts were traced by dynamic light scattering (DLS) measurements. The observed optical characteristics suggest that Cu compensated the broadening of band gap caused by Zr loading. Crystal structure of obtained photocatalysts was explored by XRD; morphological data and particle size were obtained by SEM. EDX was used for Zr and Cu content determination. Cu K-edge extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) analytical techniques were used to investigate the local Cu neighbourhood in the samples and to identify copper coordination and valence state of copper species in the synthesized nanocomposites.

The development of efficient TiO2-based photocatalysts for water treatment is mainly performed by doping with transition metals or by establishing junctions between different phases, metal–semiconductor or semiconductor–semiconductor. We present, for the first time, the synthesis of Zr- and Mn-modified TiO2 by a redesigned sol–gel technique that allows the formation of heterometallic bridges on the TiO2 surface. Cations of the doping metals are located in the pores of mesoporous anatase and attached to the crystalline TiO2 walls. The presence of the Zr enhances the photoactivity of the TiO2 catalyst. However, the introduction of Mn decreases the photocatalytic efficiency in a nonadditive manner. The inhibition effect was assigned to the side reaction between hydroxyl radicals and Mn ions. The fact that Mn effectively scavenges the hydroxyl radicals and, consequently, inhibits the whole oxidation process is direct proof that hydroxyl radicals are the main reactive species in the photocatalytic oxidative processes on TiO2 surfaces in aqueous media and the process of .OH generation is the rate-determining step, which was confirmed using a method based on the decolorization of a commercial dye Bezaktiv Blau in a reaction with Fenton's reagent as a source of hydroxyl radicals.

Monometallic (CuO and FeOx) and bimetallic (CuFeOx) entities on different supports are promising transition-metal low-cost catalysts for catalytic oxidation of volatile organic compounds (VOC) from industrial air alternatively to noble-metal catalysts which are currently in use. In this work we report for the first time that the promotion of catalytic oxidation of toluene as a model VOC is due to the cooperative redox effect between CuO nanocrystals and finely dispersed Cu-oxo-Fe clusters on mesoporous silica with defined Fe/Cu molar ratio. This increases the number and reactivity of adsorbed electrophilic (O− and O2−) as well as nucleophilic lattice oxygen (O2-) species at the CuO crystal and and Cu-oxo-Fe cluster interface, thus providing up to twofold enhancement in catalytic activity for total oxidation of toluene. Catalysts were prepared via direct synthesis of Fe-functionalized disordered mesoporous silica containing only isolated iron sites followed by copper addition via impregnation.

International audience; A mechanism for Li–S battery operation with a composite electrode and an adsorption additive obtained by using operando ultraviolet/visible (UV/vis) spectroscopy and X-ray absorption spectroscopy confirms the role of the adsorption additive and reflects the conversion mechanism of sulfur into Li2S. Operando UV/vis spectroscopy shows a reversible appearance of the long-chain polysulfides in the separator in the fifth cycle, whereas the appearance of mid- and short-chain polysulfides suggests a polysulfide shuttle mechanism. By using a nonsulfur-containing electrolyte, a high-precision analysis of sulfur K-edge X-ray absorption near-edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) spectra is possible. The XANES analysis shows that polysulfides reach the maximum concentration at the end of the high-voltage plateau, and the low-voltage plateau is characteristic of the polysulfides/Li2S equilibrium. The relative amount of Li2S increases linearly until the end of discharge and reaches a relative amount of 75%. This is confirmed by sulfur K-edge EXAFS analysis. Additionally, a quantitative analysis of EXAFS spectra measured during discharge evidences a decrease of the average S–S coordination number. This can be interpreted as a decrease of the chain length of polysulfides. EXAFS analysis showed that there are no specific interactions of the polysulfide species with the matrix or with other species in the electrolyte.

In this study smart-removal magnetic nanocomposites are developed in an attempt to decrease the band gap energy of the catalyst and to enable separation of the catalyst from the wastewater after the process. Ferrite magnetic nanoparticles Co0.5Zn0.25M0.25Fe2O4 (M = Ni, Cu, Mn, Mg) (MNPs) are obtained by the co-precipitation method using carboxymethyl cellulose (CMC) as surfactant and NaOH as precipitation agent. Further, the magnetic nanocomposites Co0.5Zn0.25M0.25Fe2O4-TiO2 (anatase) (MNPs-TiO2) are obtained by the TiO2 deposition onto the MNPs using Pluronic P123 as template and tetra butyl titanate (TBOT) as titanium source. This type of photocatalyst can be used under solar light irradiation because of the activation of TiO2 with MNPs in visible light range and can be very easily recovered due to their strong magnetic properties. The MNPs-TiO2 have proven to be very active for the degradation of different dyes, such as methyl orange and methylene blue, under solar light irradiation.

So far, in situ-generated Ni nanoparticles have been reported to be efficient catalysts for tar cracking during wood liquefaction by pyrolysis. Herein, their performance in further bio-oil conversion steps is evaluated. Nanoparticles were generated for the first time from a Ni-containing metal-organic framework, MIL-77, during the hydrotreatment of glycerol-solvolyzed lignocellulosic (LC) biomass. Reactions were conducted at 300 °C and the H2 pressure was 8 MPa in a slurry reactor. The catalytic activity and selectivity of the deoxygenation and hydrocracking reactions for real biomass-derived feedstock using in situ-generated nanoparticles was compared with Ni nanoparticles dispersed on a silica-alumina support (commercial Ni/SiO2 -Al2 O3 catalyst). The mass activity of the in situ-generated nanoparticles for hydrogenolysis was more than ten times higher in comparison to their commercial analogues, and their potential for the use in LC biorefinery is discussed.

cited By 11; International audience; Discharge/charge process of classical lithium sulphur battery proceeds through intermediate polysulphides which are soluble in classical electrolyte systems. Due to concentration gradient soluble polysulphides easily diffuse/migrate out from cathode composite forming non-uniform distribution of the sulphur within cathode. Eventually polysulphides can be completely reduced on the metallic lithium anode. In this work we compare the sorption properties of manganese modified zeolite silicalite-1 (MnS-1) with a cathode composite containing SBA-15 additive and a cathode composite without additive. Careful analysis using XPS and FIB microscopy equipped with EDX show improved retention of polysulphide species within cathode composite in the case of MnS-1 zeolite as an additive. Interestingly, the amount of sulphur species detected by XPS on the metallic lithium is very similar regardless on cathode composite we use. Finally, similar cycling behaviour can be observed if MnS-1 zeolite is used as an interlayer between composite cathode and separator. © 2014 Elsevier B.V.

This paper investigates the structural and magnetic properties of a mixed series of ferrites having general formula Co0.5Zn0.25M0.25Fe2O4 (M Ni, Cu, Mn, Mg). Insights on surface chemistry, structural and morphological parameters are presented in order to achieve highly tuned ferrite systems with specific characteristics. The site occupancy of the cations in the spinel structure was determined using XAS, XRD and Raman spectroscopy. A 100% occupancy of the tetrahedral sites was observed for the Zn cations for all the samples. Co cations occupied the octahedral sites in proportion of 100% for Co-Zn-Cu, Co-Zn -Mg and around 80% for Co-Zn-Ni, Co-Zn-Mn. 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 results were correlated with the magnetic properties data. At the same time, not only the cation distribution, but also the particles size distribution was observed to have a great influence on magnetic and optical properties of the ferrites. Given the importance of the surface chemistry of the nanoparticles, XPS and FTIR 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 (Mn(2+)and Mn4+) was elucidated. Finally, parallels have been drawn between the use of different cations in mixed ferrites in order to gain specific properties. (C) 2019 Elsevier B.V. All rights reserved.

Solid, nanoporous silica-based spherical mesoporous MCM-41 and KIL-2 with interparticle mesoporosity as well as nanosized zeolite BEA materials differing in morphology and pore size distribution, were used as carriers for the preparation of resveratrol-loaded delivery systems. Two preparation methods have been applied: (i) loading by mixing of resveratrol and mesoporous carrier in solid state and (ii) deposition in ethanol solution. The parent and the resveratrol loaded carriers were characterized by XRD, TEM, N2 physisorption, thermal analysis, and FT-IR spectroscopy. The influence of the support structure on the adsorption capacity and the release kinetics of this poorly soluble compound were investigated. Our results indicated that the chosen nanoporous silica supports are suitable for stabilization of trans-resveratrol and reveal controlled release and ability to protect the supported compound against degradation regardless of loading method. The solid-state dry mixing appears very effective for preparation of drug formulations composed of poorly soluble compound. - Graphical abstract: trans-Resveratrol was stabilized in the pores of BEA zeolite, MCM-41and KIL2 mesoporous silicas. - Highlights: • BEA, KIL-2 and MCM-41 materials were used as carriers for resveratrol loading. • Resveratrol encapsulation in ethanol solution and solid state procedure were applied. • The solid-state preparation appears very effective formore » stabilization of trans-resveratrol.« less

Zirconia nanomaterials were prepared by impregnation of KIL-2 type silica with 4, 8 and 12 wt.% ZrO2 and were modified by sulphate groups in order to vary the type and strength of acidity. Samples were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and N2 physisorption methods. Acidic properties of adsorbed pyridine were investigated by FT-IR spectroscopy. The catalytic performance of ZrKIL-2 and SO42−/ZrKIL-2 in glycerol esterification with acetic acid was studied and compared to that of pure zirconia varieties. It was found that silica-supported zirconia samples are more active than pure zirconia ones. With increasing ZrO2 content, KIL-2-supported catalysts showed increasing catalytic activity and selectivity in producing valuable fuel additives, di- and triacetyl glycerols. Sulphated analogues showed even higher activity and selectivity compared to non-sulphated ones due to their strong Bronsted acidity.

Iron-functionalized disordered mesoporous silica (FeKIL-2) is a promising, environmentally friendly, cost-effective and highly efficient catalyst for the elimination of volatile organic compounds (VOCs) from polluted air via catalytic oxidation. In this study, we investigated the type of catalytically active iron sites for different iron concentrations in FeKIL-2 catalysts using advanced characterization of the local environment of iron atoms by a combination of X-ray Absorption Spectroscopy Techniques (XANES, EXAFS) and Atomic-Resolution Scanning Transmission Electron Microscopy (AR STEM). We found that the molar ratio Fe/Si ≤ 0.01 leads to the formation of stable, mostly isolated Fe3+ sites in the silica matrix, while higher iron content Fe/Si > 0.01 leads to the formation of oligonuclear iron clusters. STEM imaging and EELS techniques confirmed the existence of these clusters. Their size ranges from one to a few nanometers, and they are unevenly distributed throughout the material. The size of the clusters was also found to be similar, regardless of the nominal concentration of iron (Fe/Si = 0.02 and Fe/Si = 0.05). From the results obtained from sample characterization and model catalytic tests, we established that the enhanced activity of FeKIL-2 with the optimal Fe/Si = 0.01 ratio can be attributed to: (1) the optimal concentration of stable isolated Fe3+ in the silica support; and (2) accelerated diffusion of the reactants in disordered mesoporous silica (FeKIL-2) when compared to ordered mesoporous silica materials (FeSBA-15, FeMCM-41).

Cobalt-containing porous silicas were prepared by incipient wetness impregnation with different salt precursors. We compare cobalt-containing silica with interparticle mesoporosity (Co/KIL-2) to mesoporous silica (Co/SBA-15) in total toluene oxidation. Different cobalt species were detected in dependence on the kind of the salt precursor used. Lower production costs and high catalytic activity and stability of Co/KIL-2 make KIL-2 a promising support for volatile organic compounds elimination.

Copper-supported catalysts are of industrial importance in many catalytic processes. Mesoporous silica materials are of particular interest as green heterogeneous catalyst supports. In the present study we demonstrate the nature and reduction properties of copper oxide species, which are influenced by the peculiarity of the silica nanoparticles with interparticle mesoporosity (KIL family) and the presence of a second metal (iron) in the silica matrix. The copper-containing KIL-2 and FeKIL-2 samples are prepared by incipient wetness impregnation. The reduction of copper oxide species is easier on the FeKIL-2 supported sample in comparison to its KIL-2 supported analogue, whereas the copper-containing KIL-2 sample shows higher catalytic activity in total toluene oxidation. The presence of iron in the FeKIL-2 structure leads to autoreduction of copper followed by the redispersion and oxidation of metallic copper in the reaction medium; this results in the formation of different types of finely dispersed copper oxide species (

Wet hydrogen peroxide catalytic oxidation (WHPCO) is one of the most important industrially applicable advanced oxidation processes (AOPs) for the decomposition of organic pollutants in water. It is demonstrated that manganese functionalized silicate nanoparticles with interparticle porosity act as a superior Fenton-type nanocatalyst in WHPCO as they can decompose 80% of a test organic compound in 30 minutes at neutral pH and room tem- perature. By using X-ray absorption spectroscopic techniques it is also shown that the superior activity of the nanocatalyst can be attributed uniquely to framework manganese, which decomposes H2O2 to reactive hydroxyls and, unlike manganese in Mn3O4 or Mn2O3 nanoparticles, does not promote the simultaneous decomposition of hydrogen peroxide. The presented material thus introduces a new family of Fenton nanocatalysts, which are environ- mentally friendly, cost-effective, and possess superior efficiency for the decomposition of H2O2 to reactive hydroxyls (AOP), which in turn readily decompose organic pollutants dissolved in water.

Mn-containing redox molecular sieves, i.e., highly crystalline microporous MnS-1 (0.6 wt% Mn, n (Si)/ n (Mn) = 160) and ordered mesoporous silicates MnMCM-41 and MnMCM-48 (1.8 wt% Mn, n (Si)/ n (Mn) = 51), were synthesized. The porosity of the products was determined by X-ray powder diffraction (XRD) and high - resolution transmission electron microscopy (HRTEM). The evidence for the presence of isolated Mn sites incorporated into the silicate framework was obtained by Mn K-edge XANES and EXAFS analysis, which provided direct information on valence state and local environment of Mn in these products. The analysis revealed the presence of predominantly Mn 3+ cations located at a 3-fold coordination in the silicate framework indicating Lewis acid sites in microporous (MnS-1) and mesoporous (MnMCM-41, MnMCM-48) silicate structures. The micro- and mesoporous silicates containing framework Mn 3+ -sites selectively catalyze the oxidation of alkyl aromatics in benzylic position to aromatic ketones in the absence of any initiator using molecular oxygen as the terminal oxidant under mild, solvent-free, liquid-phase conditions.

The photocatalytic degradation of toluene was carried out on titania/mesoporous silica photocatalysts in a self-constructed gaseous fluidized-bed photoreactor equipped with UVA light source. The powder photocatalysts were synthesized by incorporation of aqueous titania sol (as a photoactive component), into silica mesoporous materials (as a high-surface-area support), via the sol–gel impregnation method. SBA-15 was used as an ordered and KIL-2 as a disordered mesoporous silica support. The Ti/Si nominal molar ratio was adjusted to 1/2, 1/1 and 2/1. The photocatalysts were characterized by X-ray diffraction (XRD), nitrogen sorption (BET), UV–vis–NIR diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FT-IR) and high-resolution transmission electron microscopy (HR-TEM). The effects of Ti/Si molar ratio and of the mesoporous silica structure were investigated measuring adsorption capacity and photocatalytic degradation of toluene. The rates of photocatalytic degradation reactions were found to be similar for photocatalysts with the same Ti/Si molar ratio independently of the mesoporous structure of silica. The adsorption capacity was decreasing as a function of the increasing Ti/Si molar ratio in the case of both types of mesoporous silica support. However, the photocatalytic degradation proceeded faster for the Ti/Si molar ratio 1/1 while, in the case of the other investigated Ti/Si molar ratios 1/2 and 2/1, the degradation rates were lower. In general, the photocatalytic activity was considerably improved by using supported titania–silica catalyst compared to an unsupported titania powder prepared from the same nanocrystalline titania sol.

Ordered (SBA-15) and disordered (KIL-2) mesoporous silica supports have been synthesized and used for incorporation of titania with different Ti/Si molar ratios (1/2, 1/1, 2/1) via sol–gel impregnation method. Titanium isopropoxide and aqueous titania sol prepared by low-temperature sol–gel processing were used as a source of titania. Characterization by powder X-ray diffraction (XRD), nitrogen sorption measurements, scanning electron microscopy (SEM) and UV–vis–NIR diffuse reflectance spectroscopy (DRS) has been carried out to investigate the chemical framework and morphology of powders. The photocatalytic degradation of isopropanol in the gaseous medium was selected as a probe reaction to test the photoactivity of powders and to verify the potential application of these materials for air remediation. It was found that the titania source, Ti/Si molar ratio and the type of silica support influenced the functional properties of the material, which were evaluated by adsorption capacity and photocatalytic activity in the gas–solid reactor. The adsorption capacity of isopropanol was the highest in the presence of the SBA-15-supported materials. The photoactivity results indicated that the powders which were prepared using SBA-15 as a silica support and a Ti/Si molar ratio of 1/1 were the most active towards isopropanol oxidation monitored in situ by FT-IR spectroscopy.

Mesoporous aluminophosphate thin films and xerogels with ordered three-dimensional pore arrangement, modified by silicon or silicon and manganese, were synthesized. Aluminophosphate reaction mixtures were templated with non ionic polymer surfactant Pluronic F127 and deposited as thin layers of precursor solution on Petri dishes for xerogels and on glass substrates for thin films. Surfactant removal was investigated by thermal analysis. Small Angle X-ray Scattering measurements showed that calcined silicoaluminophosphate (SAPO) and manganese silicoaluminophosphate (MnSAPO) thin films have highly ordered mesostructures, which remain stable up to at least 400°C. The mesostructures exhibit cubic symmetry described by an Im3̄m space group. Cubic mesostructure was confirmed also by TEM, SEM and AFM microscopy. Incorporation of silicon and manganese into the aluminophosphate framework was studied by solid-state NMR and X-ray absorption spectroscopy. Silicon-rich domains were detected in calcined SAPO and MnSAPO xerogels and in MnSAPO thin films. The observation of Si(OSi)3(OAl) framework units at the border of such domains suggests that acid sites might be included within silicoaluminophosphate walls. Mn3+ and Mn2+ cations are present in the MnSAPO frameworks of calcined xerogels and thin films in the molar ratio of 40%/60%. Manganese cations are coordinated to four oxygen atoms, suggesting that they are incorporated within the framework and that they can act as framework redox sites. Fil: Cecowski, Sasa. National Institute Of Chemistry; Eslovenia Fil: Tusar, Natasa Novak. National Institute Of Chemistry; Eslovenia Fil: Rangus, Mojca. National Institute Of Chemistry; Eslovenia Fil: Mali, Gregor. National Institute Of Chemistry; Eslovenia Fil: Soler Illia, Galo Juan de Avila Arturo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; Argentina Fil: Kaucic, Venceslav. National Institute Of Chemistry; Eslovenia

Porous silicates are often used as catalysts or catalyst supports for many chemical reactions. The immobilization of metals by their incorporation into silicate frameworks is an important strategy for generating catalytically active sites. The catalytic properties of metal-modified porous silicates depend on the structure type and on the location and nature of the incorporated metal. Recently, manganese-containing porous silicates have received considerable attention as catalysts for various chemical conversions. Herein, an overview on the synthesis, structure characterization, and catalytic applications of manganese-containing porous silicates is presented. The particular suitability of these materials to address major challenges in environmentally benign catalysis is outlined.

The present work deals with the study of the parameters which govern the partial conversion of the amorphous walls of Al-SBA-15 supports into ZSM-5 type deposits under alkaline aqueous conditions. The influence of the mode of insertion of aluminium into Al-SBA-15 as well as of the quantities of ammonium fluoride and ZSM-5 template (TPABr) has been investigated. XRD and nitrogen sorption data indicate that the mesopore network is very fragile under the conditions required for the crystallization of ZSM-5. A compromise was found by using a TPABr/Al molar ratio lower than 1, thus affording materials containing both mesopores and zeolite-type micropores. The combined use of hyperpolarized (HP) 129Xe NMR and α-plot studies gave evidence for the ZSM-5 nature of the micropores as well as some indications in favour of the interconnection of the different pore networks.

In this study the uptake capacity of Mn(II) ions by zeolite A beads was investigated for different initial Mn concentration (100-400 mg Mn dm(-3)) in batch mode at 25-55 degrees C. The obtained adsorption capacity varying from 30 to 50 mg Mn g(-1) demonstrated a high affinity of zeolite A towards Mn(II) present in solutions. Kinetic studies indicated the intra-particle diffusion as the rate limiting step up to 45 degrees C with apparent diffusivities in the range (1.2-2.0) x 10(-13) m(2) s(-1) and the activation energy of 21.9 kJ mol(-1), which implies strong interactions between the zeolite A and Mn ions. At 55 degrees C ion-exchange became the rate limiting step. The adsorption isotherms were studied at 25 degrees C showing that the Mn adsorption is the best described by the Langmuir model suggesting a homogenous zeolite surface. XPS analysis of the Mn-loaded beads showed that there is no surface accumulation of Mn but an almost uniform Mn distribution inside zeolite A, whereas XANES and EXAFS suggested that the adsorption of Mn(II) was followed by the Mn(II) oxidation and oxide formation. Regeneration of the spent zeolite was examined in 8 adsorption/desorption cycles by a chelating Na(2)EDTA in a fluidized column. It has been found that zeolite A beads could be reused for at least 4 cycles with satisfactory Mn(II) adsorption efficiencies of about 70%.

Mesoporous silicate catalyst FeTUD-1 containing only isolated iron was synthesized. Local environment of iron was investigated by X-ray Absorption and Mossbauer spectroscopies. XANES (X-ray Absorption Near Edge Structure) studies show that iron in the as-synthesized and template-free FeTUD-1 is present in the form of Fe3+ ions in coordination geometries posses an inversion center. EXAFS (X-ray Absorption Fine Structure) analyses reveal that iron cations in the as-synthesized sample are coordinated to four oxygens at the distance of 1.87 A and in the template-free sample to one oxygen at 1.86 A and five oxygens at 2.0 A distances. Mossbauer spectroscopy proves the presence of iron in Fe3+ form in template-free sample. Moreover, it determines Fe3+ in two types of distorted octahedral coordinations.

A thorough FTIR investigation of the thermal stability of arenesulfonic modified SBA-15 solids revealed that most of the organic functional groups are preserved until 400 °C. These results have been confirmed by the thermogravimetric analyses of the corresponding materials calcined at 200 °C (EC-200) or 400 °C (EC-400), respectively. Such studies showed that the smoother calcination procedure (200 °C) is appropriate in order to complete the removal of Pluronic P123 in the extracted sample (E). Moreover, it can be noticed that such calcination treatment did not alter tremendously the catalytic performances of the resulting solids. Both E and EC-200 materials exhibited high activities in the liquid phase condensation of 2-methylfuran with acetone and in the decomposition of cumene hydroperoxide into phenol.

Thermally stable titanium-containing microporous/mesoporous composite (Ti, Al)-Beta/MCM-48 was synthesised hydrothermally in the presence of structure-directing agents cetyltrimethylammonium bromide (CTABr), polyoxyethylene(8) isooctylhexyl ether (Triton ® X-114) and tetraethylammonium hydroxide (TEAOH) in the absence of sodium cations. The presence of both microporous and mesoporous phases was determined by XRD and HRTEM measurements and by the analysis of nitrogen adsorption isotherm based on the α -plot method. The mass percentage ( μ ) of the microporous material in the composite is approximately 6.5%. NMR investigations showed that acid sites related to framework aluminium were generated by calcination of the as-synthesised (Ti, Al)-Beta/MCM-48. Local environment of titanium incorporated into the microporous/mesoporous silicate material was investigated by X-ray absorption spectroscopy. XANES studies showed the presence of tetrahedrally-coordinated Ti 4+ cations in the template-free sample. EXAFS analysis revealed that titanium cations were coordinated to four oxygens in the first coordination shell, to one oxygen at 1.73(1) A and three oxygens at 1.86(1) A. In the second coordination sphere three silicon atoms were found at distances 3.18(2) A and 3.48(2) A, respectively. These results indicated framework Ti and thus the presence of Ti oxidation centres within the composite material.

Manganese-modified hexagonal mesoporous aluminophosphate (MnHMA) was synthesized hydrothermally in a microwave oven in the presence of cetyltrimethylammonium chloride (CTACl) as a template. The mesoporous structure was elucidated by HRTEM. Local environment of aluminum and phosphorus forming the mesoporous aluminophosphate framework was studied by MAS NMR. The local environment of manganese incorporated in HMA was investigated by X-ray absorption spectroscopy. XANES studies show that manganese in the as-synthesized and template-free MnHMA is present in the form of Mn 2+ and Mn 3+ ions in the ratio 40–60%. EXAFS analyses revealed four oxygens in the first coordination sphere of manganese in the as-synthesized and template-free MnHMA at the distances 2.142(5) A and 2.15(1) A, respectively. EPR and ESEEM measurements revealed that Mn 2+ in both as-synthesized and template-free products was located within the mesoporous aluminophosphate framework.

Hydrothermally stable titanium containing microporous/mesoporous composite (Ti,Al)-Beta/MCM-41 was synthesized hydrothermally in the presence of structure-directing agents cetyltrimethylammonium bromide (CTABr) and tetraethyl ammonium hydroxide (TEAOH). XRD analysis and analysis of nitrogen adsorption isotherm confirmed the presence of micropores and mesopores in the composite. HRTEM microscopic studies revealed that micro- and mesoporosity of the composite was not due to the mechanical mixture of microporous (Ti,Al)-Beta and mesoporous (Ti,Al)-Beta/MCM-41. The local environment of titanium incorporated into the microporous/mesoporous silicate material was investigated by X-ray absorption spectroscopy. XANES studies showed the presence of tetrahedrally coordinated Ti 4+ cations in the template-free sample. EXAFS analysis revealed that titanium cations were coordinated to four oxygens in the first coordination shell at a distance of 1.84 A. In the second coordination sphere one and two silicon atoms were found at the distances 3.12 A and 3.51 A, respectively. These results indicated framework Ti and thus the presence of Ti oxidation centers within the composite material. NMR investigations showed that Bronsted and Lewis acid sites related to framework aluminum were generated by the removal of potassium and sodium ions from the (Ti,Al)-Beta/MCM-41 pores. The new composite material was preliminarily tested in the oxidation reaction. Titanium leaching from the composite was not observed.