The impact of preparation route on the performance of silver dodecatungstophosphate/β zeolite catalysts in the ethylene production

Heteropolyacids and their salts comprise catalytic centers for the production of ethylene, one of the most important constituents in the chemical industry. The paper emphasizes different synthesis routes of hybrid materials consisting of dodecatungstophosphoric acid silver salt (AgPW) and β zeolite—stepwise wet impregnation, silver-exchange in β zeolite, and dry mixing of precursors. Composite preparation procedures induced minor effects on the weak acid sites, while strong acid sites were increased significantly. β/AgPW composites prepared by two-steps wet impregnation and ion-exchange procedures have strong acid sites content and total acidity higher in comparison to the pure AgPW salt and β zeolite. This is a result of precursors synergetic effect—cumulative strong acidic sites are generated in the presence of well-dispersed Keggin ions on the zeolite network. Composite samples with a higher content of strong acid centers exhibit higher conversion in the ethanol dehydration reaction, i.e., the ion-exchanged βAgPW sample has attained a conversion over 81%, while the wet-impregnated sample has a significant 86%. The distribution and presence of AgPW active phase are found to be crucial for both stable conversion and high selectivity results in ethylene production from ethanol, which is regarded as one of the most significant processes in environmental and sustainable industrial chemistry. Graphic abstract: [Figure not available: see fulltext.

Electrochemical Crosslinking of Alginate—Towards Doped Carbons for Oxygen Reduction

Electrochemical crosslinking of alginate strands by in situ iron oxidation was explored using a potentiostatic regime. Carbon-based materials co-doped with iron, nitrogen, and/or sulfur were prepared via electrolyte composition variation with a nitrogen-rich compound (rivanol) or through post-treatments with sodium sulfide. Nanometer-sized iron particles were confirmed by transmission and field emission scanning electron microscopy in all samples as a consequence of the homogeneous dispersion of iron in the alginate scaffold and its concomitant growth-limiting effect of alginate chains. Raman spectra confirmed a rise in structural disorder with rivanol/Na2S treatment, which points to more defect sites and edges known to be active sites for oxygen reduction. Fourier transform infrared (FTIR) spectra confirmed the presence of different iron, nitrogen, and sulfur species, with a marked difference between Na2S treated/untreated samples. The most positive onset potential (−0.26 V vs. saturated calomel electrode, SCE) was evidenced for the sample co-doped with N, S, and Fe, surpassing the activity of those with single and/or double doping. The mechanism of oxygen reduction in 0.1 M KOH was dominated by the 2e− reduction pathway at low overpotentials and shifted towards complete 4e− reduction at the most negative explored values. The presented results put forward electrochemically formed alginate gels functionalized by homogeneously dispersed multivalent cations as an excellent starting point in nanomaterial design and engineering

Can Zeolite-Supporting Acridines Boost Their Anticancer Performance?

Acridine and its derivatives (9-chloroacridine and 9-aminoacridine) are investigated here, supported on FAU type zeolite Y, as a delivery system of anticancer agents. FTIR/Raman spectroscopy and electron microscopy revealed successful drug loading on the zeolite surface, while spectrofluorimetry was employed for drug quantification. The effects of the tested compounds on cell viability were evaluated using in vitro methylthiazol-tetrazolium (MTT) colorimetric technique against human colorectal carcinoma (cell line HCT-116) and MRC-5 fibroblasts. Zeolite structure remained unchanged during homogeneous drug impregnation with achieved drug loadings in the 18–21 mg/g range. The highest drug release, in the µM concentration range, with favourable kinetics was established for zeolite-supported 9-aminoacridine. The acridine delivery via zeolite carrier is viewed in terms of solvation energy and zeolite adsorption sites. The cytotoxic effect of supported acridines on HCT-116 cells reveals that the zeolite carrier improves toxicity, while the highest efficiency is displayed by zeolite-impregnated 9-aminoacridine. The 9-aminoacridine delivery via zeolite carrier favours healthy tissue preservation while accompanying increased toxicity toward cancer cells. Cytotoxicity results are well correlated with theoretical modelling and release study, providing promising results for applicative purposes

Environmental Potential of Carbonized MOF-5/PANI Composites for Pesticide, Dye, and Metal Cations—Can They Actually Retain Them All?

The environmental application of the carbonized composites of the Zn-containing metal-organic framework MOF-5 and polyaniline (PANI) in its emeraldine salt and base forms (C-(MOF-5/PANI)) was investigated for the first time. Textural properties and particle size distributions revealed that composites are dominantly mesoporous and nanoscale in nature, while Raman spectroscopy revealed the ZnO phase beneath the carbon matrix. Adsorption of pesticide, dye, and metal cation on C-(MOF-5/PANI) composites in aqueous solutions was evaluated and compared with the behavior of the precursor components, carbonized MOF-5 (cMOF), and carbonized PANIs. A lower MOF-5 content in the precursor, a higher specific surface area, and the pore volume of the composites led to improved adsorption performance for acetamiprid (124 mg/g) and Methylene Blue (135 mg/g). The presence of O/N functional groups in composites is essential for the adsorption of nitrogen-rich pollutants through hydrogen bonding with an estimated monolayer capacity twice as high as that of cMOF. The proton exchange accompanying Cd2+ retention was associated with the Zn/Cd ion exchange, and the highest capacity (9.8 mg/g) was observed for the composite synthesized from the precursor with a high MOF-5 content. The multifunctionality of composites was evidenced in mixtures of pollutants where noticeably better performance for Cd2+ removal was found for the composite compared to cMOF. Competitive binding between three pollutants favored the adsorption of pesticide and dye, thereby hindering to some extent the ion exchange necessary for the removal of metal cations. The results emphasize the importance of the PANI form and MOF-5/PANI weight ratio in precursors for the development of surface, porosity, and active sites in C-(MOF-5/PANI) composites, thus guiding their environmental efficiency. The study also demonstrated that C-(MOF-5/PANI) composites retained studied pollutants much better than carbonized precursor PANIs and showed comparable or better adsorption ability than cMOF

Enzymatic oligomerization and polymerization of arylamines: state of the art and perspectives

The literature concerning the oxidative oligomerization and polymerization of various arylamines, e.g., aniline, substituted anilines, aminonaphthalene and its derivatives, catalyzed by oxidoreductases, such as laccases and peroxidases, in aqueous, organic, and mixed aqueous organic monophasic or biphasic media, is reviewed. An overview of template-free as well as template-assisted enzymatic syntheses of oligomers and polymers of arylamines is given. Special attention is paid to mechanistic aspects of these biocatalytic processes. Because of the nontoxicity of oxidoreductases and their high catalytic efficiency, as well as high selectivity of enzymatic oligomerizations/polymerizations under mild conditions-using mainly water as a solvent and often resulting in minimal byproduct formation-enzymatic oligomerizations and polymerizations of arylamines are environmentally friendly and significantly contribute to a "green'' chemistry of conducting and redox-active oligomers and polymers. Current and potential future applications of enzymatic polymerization processes and enzymatically synthesized oligo/polyarylamines are discussed

Pesticide adsorption on zeolites, polyanilines and their composites

Katalitička svojstva Fe-modifikovanih zeolita zavise od formiranja dimernih i oligomernih vrsta gvožđa, kao i čestica gvožđe-oksida. U ovoj doktorskoj disertaciji je sinteza Femodifikovanih ZSM-5 zeolita izvedena metodom jonske izmene iz razblaženih rastvora različitih soli (Fe(III)citrata, Fe(II)oksalata i Fe(III)nitrata). Pokazano je da aktivnost Femodifikovanih zeolita kao katalizatora zavisi od soli gvožđa u čijem prisustvu se vrši izmena, što ukazuje da je moguće, iz razblaženih rastvora, dobiti različite vrste gvožđa kao centre na zeolitima, dok se izolovani, dispergovani joni, koji su presudni za adsorpciju i katalizu, u velikom prinosu dobijaju samo izmenom iz rastvora Fe(II)oksalata. Oksidacija metilen-plavog u prisustvu vodonik-peroksida kao tipična katalitička test reakcija je pokazala da polazni HZSM-5 ima slabija katalitička svojstva nego Femodifikovani ZSM-5 zeoliti. Najveću aktivnost je pokazao uzorak izmenjen u rastvoru Fe(III)citrata što predstavlja potvrdu da su mononuklearni, izolovani centri gvožđa, čak i pri niskim koncentracijama, od presudnog značaja za aktivnost katalizatora. S obzirom da su se sintetisani Fe-modifikovani zeoliti pokazali kao aktivni katalizatori, ispitana je adsorpcija isparljivih organskih jedinjenja, koja predstavljaju česte zagađivače u životnoj sredini. Ispitivano je da li se na hidratisanim Fe-modifikovanim zeolitima adsorbuju isparljiva organska jedinjenja (n-heksan, benzen, metil-benzen i etil-benzen). Utvrđeno je, na osnovu eksperimenata temperaturski-programirane desorpcije, da se nepolarni molekuli ispitivanih organskih jedinjenja vezuju na hidratisanim zeolitima na specifičnim, jakim adsorpcionim centrima. Do vezivanja najverovatnije dolazi tako što organski molekuli zamenjuju vodu prethodno adsorbovanu na istim centrima, što predstavlja indikaciju da ovi materijali mogu da se koriste za akumulaciju/adsorpciju isparljivih organskih jedinjenja iz vodenih rastvora. Korišćenjem analize masenih spektara je pokazano da se n-heksan i benzen molekulski adsorbuju i desorbuju, dok se u slučaju desorpcije metil-benzena i etil-benzena javljaju novi maseni fragmenti koji potvrđuju da je desorpcija metil-benzena i etil-benzena praćena njihovim razlaganjem na aktivnim centrima hidratisanih zeolita. Analizom ukupnog sadržaja ugljenika potvrđeno da su svi sintetisani FeZSM-5 zeoliti aktivni i kao katalizatori u reakcijama oksidacije metil-benzena i etil-benzena u prisustvu vodonikperoksida. U nastavku teze je razvijen postupak za sintezu novih kompozita polaznog HZSM-5 i modifikovanog FeZSM-5 zeolita sa nanostrukturnim i granularnim polianilinima, kao potencijalnih adsorbenata/katalizatora. Ovi kompoziti su sintetisani oksidativnom polimerizacijom anilina u vodi (bez dodate kiseline) i u vodenom rastvoru sumporne kiseline u prisustvu zeolita, korišćenjem amonijum peroksidisulfata (APS) kao oksidacionog sredstva i različitih početnih masenih odnosa anilin/zeolit. Materijali su okarakterisani velikim brojem fizičko-hemijskih tehnika (HPLC, ULj-Vid, FTIC, ramanska, IKP-OES i EPR spektroskopija, TGA, elementarna analiza, XRD, SEM, TEM, analiza fizisorpcije azota, Hg-porozimetrija i merenje električne provodljivosti)...The catalytic properties of Fe-exchanged zeolites are influenced by the formation of dimeric and oligomeric iron species and oxide particles. In this thesis, the preparation of FeZSM-5 zeolite by ion-exchange method was carried out using dilute solutions of various salts (Fe(III)citrate, Fe(II)oxalate and Fe(III)nitrate). It has been demonstrated that the activity of the Fe-exchanged zeolite catalyst depends on the iron salt used for ionexchange, indicating that various types of iron can be obtained as active centers in zeolites. However, the isolated, dispersed ions, which are essential for adsorption and catalysis, can be, with high yield, obtained only by ion-exchange in the presence of Fe(II)oxalate. Oxidation of the Methylene Blue dye with hydrogen peroxide is a typical catalytic reaction and this test showed that the starting HZSM-5 expresses lower activity in comparison with Fe-exchanged ZSM-5 zeolites. The highest activity was found for the sample prepared in the presence of Fe(III) citrate which is confirmation that, even at low concentrations, the mononuclear isolated iron centers are crucial for the catalyst activity. Since the Feexchanged zeolites have proved as active catalysts, the adsorption of volatile organic compounds, which are common contaminants in the environment, was tested. We examined whether the volatile organic compounds (n-hexane, benzene, methylbenzene, and ethyl benzene) adsorb on hydrated Fe-exchanged zeolites. It was determined, by means of temperature - programmed desorption coupled with mass spectrometry, that tested, non-polar organic molecules do adsorb on specific, strong adsorption centers in hydrated zeolites. The binding occurred when organic molecules replaced water previously adsorbed at the same centers. This finding suggests that these materials can be used for accumulation/adsorption of volatile organic compounds from aqueous solutions. The analysis of mass spectra has revealed that n-hexane and benzene are both adsorbed and desorbed in molecular form, while new mass fragments were recorded during methylbenzene and ethyl-benzene desorption which implied their decomposition at active sites in hydrated zeolites. The analysis of the total carbon content confirmed that all ionexchanged FeZSM-5 zeolites were active catalysts in oxidation reactions of methylbenzene and ethyl-benzene in the presence of hydrogen peroxide. Subsequently, a method for the synthesis of new composite adsorbent/catalyst materials was developed. Composites, comprising the starting HZSM-5 or ion-exchanged FeZSM-5 zeolite and nanostructured or granular polyanilines, were synthesized by the oxidative polymerization of aniline in water (without added acid) and in an aqueous solution of sulfuric acid in the presence of zeolite, using ammonium peroxydisulfate (APS) as an oxidizing agent. Various initial mass ratios aniline/zeolite were used. These materials were characterized by a large number of experimental techniques (HPLC, UV/Vis, FTIC, Raman, ICP - OES and EPR spectroscopies, TGA, elemental analysis, XRD, SEM, TEM, nitrogen physisorption, Hg-porosimetry and electrical conductivity measurements)..

Pesticide adsorption on zeolites, polyanilines and their composites

Katalitička svojstva Fe-modifikovanih zeolita zavise od formiranja dimernih i oligomernih vrsta gvožđa, kao i čestica gvožđe-oksida. U ovoj doktorskoj disertaciji je sinteza Femodifikovanih ZSM-5 zeolita izvedena metodom jonske izmene iz razblaženih rastvora različitih soli (Fe(III)citrata, Fe(II)oksalata i Fe(III)nitrata). Pokazano je da aktivnost Femodifikovanih zeolita kao katalizatora zavisi od soli gvožđa u čijem prisustvu se vrši izmena, što ukazuje da je moguće, iz razblaženih rastvora, dobiti različite vrste gvožđa kao centre na zeolitima, dok se izolovani, dispergovani joni, koji su presudni za adsorpciju i katalizu, u velikom prinosu dobijaju samo izmenom iz rastvora Fe(II)oksalata. Oksidacija metilen-plavog u prisustvu vodonik-peroksida kao tipična katalitička test reakcija je pokazala da polazni HZSM-5 ima slabija katalitička svojstva nego Femodifikovani ZSM-5 zeoliti. Najveću aktivnost je pokazao uzorak izmenjen u rastvoru Fe(III)citrata što predstavlja potvrdu da su mononuklearni, izolovani centri gvožđa, čak i pri niskim koncentracijama, od presudnog značaja za aktivnost katalizatora. S obzirom da su se sintetisani Fe-modifikovani zeoliti pokazali kao aktivni katalizatori, ispitana je adsorpcija isparljivih organskih jedinjenja, koja predstavljaju česte zagađivače u životnoj sredini. Ispitivano je da li se na hidratisanim Fe-modifikovanim zeolitima adsorbuju isparljiva organska jedinjenja (n-heksan, benzen, metil-benzen i etil-benzen). Utvrđeno je, na osnovu eksperimenata temperaturski-programirane desorpcije, da se nepolarni molekuli ispitivanih organskih jedinjenja vezuju na hidratisanim zeolitima na specifičnim, jakim adsorpcionim centrima. Do vezivanja najverovatnije dolazi tako što organski molekuli zamenjuju vodu prethodno adsorbovanu na istim centrima, što predstavlja indikaciju da ovi materijali mogu da se koriste za akumulaciju/adsorpciju isparljivih organskih jedinjenja iz vodenih rastvora. Korišćenjem analize masenih spektara je pokazano da se n-heksan i benzen molekulski adsorbuju i desorbuju, dok se u slučaju desorpcije metil-benzena i etil-benzena javljaju novi maseni fragmenti koji potvrđuju da je desorpcija metil-benzena i etil-benzena praćena njihovim razlaganjem na aktivnim centrima hidratisanih zeolita. Analizom ukupnog sadržaja ugljenika potvrđeno da su svi sintetisani FeZSM-5 zeoliti aktivni i kao katalizatori u reakcijama oksidacije metil-benzena i etil-benzena u prisustvu vodonikperoksida. U nastavku teze je razvijen postupak za sintezu novih kompozita polaznog HZSM-5 i modifikovanog FeZSM-5 zeolita sa nanostrukturnim i granularnim polianilinima, kao potencijalnih adsorbenata/katalizatora. Ovi kompoziti su sintetisani oksidativnom polimerizacijom anilina u vodi (bez dodate kiseline) i u vodenom rastvoru sumporne kiseline u prisustvu zeolita, korišćenjem amonijum peroksidisulfata (APS) kao oksidacionog sredstva i različitih početnih masenih odnosa anilin/zeolit. Materijali su okarakterisani velikim brojem fizičko-hemijskih tehnika (HPLC, ULj-Vid, FTIC, ramanska, IKP-OES i EPR spektroskopija, TGA, elementarna analiza, XRD, SEM, TEM, analiza fizisorpcije azota, Hg-porozimetrija i merenje električne provodljivosti)...The catalytic properties of Fe-exchanged zeolites are influenced by the formation of dimeric and oligomeric iron species and oxide particles. In this thesis, the preparation of FeZSM-5 zeolite by ion-exchange method was carried out using dilute solutions of various salts (Fe(III)citrate, Fe(II)oxalate and Fe(III)nitrate). It has been demonstrated that the activity of the Fe-exchanged zeolite catalyst depends on the iron salt used for ionexchange, indicating that various types of iron can be obtained as active centers in zeolites. However, the isolated, dispersed ions, which are essential for adsorption and catalysis, can be, with high yield, obtained only by ion-exchange in the presence of Fe(II)oxalate. Oxidation of the Methylene Blue dye with hydrogen peroxide is a typical catalytic reaction and this test showed that the starting HZSM-5 expresses lower activity in comparison with Fe-exchanged ZSM-5 zeolites. The highest activity was found for the sample prepared in the presence of Fe(III) citrate which is confirmation that, even at low concentrations, the mononuclear isolated iron centers are crucial for the catalyst activity. Since the Feexchanged zeolites have proved as active catalysts, the adsorption of volatile organic compounds, which are common contaminants in the environment, was tested. We examined whether the volatile organic compounds (n-hexane, benzene, methylbenzene, and ethyl benzene) adsorb on hydrated Fe-exchanged zeolites. It was determined, by means of temperature - programmed desorption coupled with mass spectrometry, that tested, non-polar organic molecules do adsorb on specific, strong adsorption centers in hydrated zeolites. The binding occurred when organic molecules replaced water previously adsorbed at the same centers. This finding suggests that these materials can be used for accumulation/adsorption of volatile organic compounds from aqueous solutions. The analysis of mass spectra has revealed that n-hexane and benzene are both adsorbed and desorbed in molecular form, while new mass fragments were recorded during methylbenzene and ethyl-benzene desorption which implied their decomposition at active sites in hydrated zeolites. The analysis of the total carbon content confirmed that all ionexchanged FeZSM-5 zeolites were active catalysts in oxidation reactions of methylbenzene and ethyl-benzene in the presence of hydrogen peroxide. Subsequently, a method for the synthesis of new composite adsorbent/catalyst materials was developed. Composites, comprising the starting HZSM-5 or ion-exchanged FeZSM-5 zeolite and nanostructured or granular polyanilines, were synthesized by the oxidative polymerization of aniline in water (without added acid) and in an aqueous solution of sulfuric acid in the presence of zeolite, using ammonium peroxydisulfate (APS) as an oxidizing agent. Various initial mass ratios aniline/zeolite were used. These materials were characterized by a large number of experimental techniques (HPLC, UV/Vis, FTIC, Raman, ICP - OES and EPR spectroscopies, TGA, elemental analysis, XRD, SEM, TEM, nitrogen physisorption, Hg-porosimetry and electrical conductivity measurements)..

Karakterizacija Fe-ZSM-5 katalizatora dobijenog jonskom izmenom u rastvorima Fe-citrata i Fe-oksalata

The oxidation-reduction properties of iron cations exchanged into zeolites have been know for some time and zeolites that contain ion-exchanged iron are known to be catalytically active for several reduction-oxidation type reactions. Different methods are suited for preparing Fe-ZSM-5 catalysts like addition of iron during the hydrothermal synthesis of ZSM-5, ion exchange in the liquid phase, solid-state ion exchange, or sublimation (chemical vapor deposition) of FeCl3. The nature and local environment of iron species is strongly dependent on the synthetic route, which influences their catalytic performance. In the work presented here, Fe-ZSM-5 catalysts have been obtained from a hydrogen form of the zeolite ZSM-5, with Si/Al=15 purchased from Zeolyst International. Fe-ZSM-5 catalysts were prepared using Fe-citrate and Fe-oxalate solutions. The obtained samples were characterized by IR, TG, XRPD method and temperature programmed desorption (TPD) technique. The effect of ion exchange procedures on the activity of Fe-ZSM-5 catalysts was studied by n-hexane adsorption experiments. The main aim of this work was to evaluate and compare the influence of ion exchange procedure on the active sites for adsorption in the investigated samples.Zeoliti koji poseduju jone gvožđa su vrlo važni katalizatori u oksidoredukcionim reakcijama, kako u gasovima, tako i u rastvorima. U ovom radu su napravljeni i okarakterisani uzorci Fe-ZSM-5 zeolita koji su sintetisani iz Fe-oksalatnog i po prvi put, Fe-citratnog rastvora. Pokazano je da stepen izmene jako zavisi od uslova sinteze i da se mehanizam izmene u prisustvu Fe-citrata i Fe-oksalata znatno razlikuje. Oba tipa uzoraka u hidratisanoj formi adsorbuju nepolarni molekul n-heksana. TPD-MS i TG rezultati ukazuju da se heksan različito vezuje na uzorcima dobijenim iz rastvora Fe-citrata u odnosu na uzorke dobijene iz Feoksalata

Galectin-3 Involvement in Cognitive Processes for New Therapeutic Considerations

Cognitive impairment may be a consequence of the normal aging process, but it may also be the hallmark of various neurodegenerative and psychiatric diseases. Early identification of individuals at particular risk for cognitive decline is critical, as it is imperative to maintain a cognitive reserve in these neuropsychiatric entities. In recent years, galectin-3 (Gal-3), a member of the galectin family, has received considerable attention with respect to aspects of neuroinflammation and neurodegeneration. The mechanisms behind the putative relationship between Gal-3 and cognitive impairment are not yet clear. Intrigued by this versatile molecule and its unique modular architecture, the latest data on this relationship are presented here. This mini-review summarizes recent findings on the mechanisms by which Gal-3 affects cognitive functioning in both animal and human models. Particular emphasis is placed on the role of Gal-3 in modulating the inflammatory response as a fine-tuner of microglia morphology and phenotype. A review of recent literature on the utility of Gal-3 as a biomarker is provided, and approaches to strategically exploit Gal-3 activities with therapeutic intentions in neuropsychiatric diseases are outlined