Exchanged NaY Zeolite Research Articles

Molecular dynamic simulations for interactions of oxytetracycline with copper(II)-exchanged NaY zeolite

• Surface structure reflections on interactions of OTC with Cu 2+ -Y was explored. • The Raman spectra revealed ion exchange took place at the 4-ring I site. • Cu 2+ -Y offered reducing strain broadening and narrow particle size distribution. • MD simulation revealed ability of Cu 2+ -Y to attract OTC at force interaction. This study was devoted to examine the effect of the surface structure of Cu 2+ -Y against pure NaY on the photodegradation of oxytetracycline (OTC). The lattice strain examined by Rietveld analysis of XRD data showed strain induced peak broadening at 0.124 for NaY, which diminished to 0.119 for Cu 2+ -Y, prompted by the exchange of Cu 2+ onto the NaY zeolite. Scanning electron microscope (SEM) statistical analysis of Cu 2+ -Y revealed better crystallinity with larger cube width, >2 µm, compared with NaY, 1.7 µm. The vibrational modes and optical properties of Cu 2+ -Y and NaY were compared using Fourier transform infrared (FTIR) spectra, Raman spectroscopy, and ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS). An IR band at 665 cm −1 associated with ν s (Si-O-Cu) was evident for Cu 2+ -Y, which was absent from the spectrum of pure NaY. The Raman bending vibration at 490 cm −1 due to 4-membered ring I in the Cu 2+ -Y displayed a blue shift and a lower value of the full width at half maximum (FWHM) by about 3.02 nm and 0.74 cm −1 , respectively, compared with that of NaY. It was proposed that Cu 2+ ions are attached to shared oxygen of double 4-rings in Y-zeolite. The electronic analysis of Cu 2+ -Y revealed an indirect energy bandgap of 3.17 eV together with an excitonic absorption band at ∼2 eV. The computational molecular adsorption calculations demonstrated the potential effect of Cu 2+ -Y to accommodate five molecules of OTC per unit cell. Molecular dynamics (MD) simulations were committed to support the response behind the higher efficiency and stability of Cu 2+ -Y towards adsorption of the OTC under the force of interaction. OTC molecules brought into being travel toward positions of copper in the optimized OTC@Cu 2+ -Y. In contrast, Na + ions in OTC@NaY held moving towards the edges of the zeolite unit cell and no evidence of the presence of OTC molecules inside the confines of the zeolite cavities. H-bond distribution indicate a close connection and a more stable configuration of OTC inside the Cu 2+ -Y. Thus, MD simulations can safely predict the potential of Cu 2+ to attract the OTC molecules to form OTC@Cu 2+ -Y complexes.

Antibacterial Action and Efficacy of Silver and Copper Exchanged Na-Y Zeolite from Fly Ash on 304 Stainless Steel Coupons by Agar Diffusion Method

Na-Y Zeolite synthesized from fly ash was exchanged with Ag+ and Cu2+ ions by ion exchange process. The antibacterial action and efficacy of silver and copper exchanged Na-Y zeolite on Escherichia coli and Staphylococcus aureus were investigated. Escherichia coli and Staphylococcus aureus was suspended in broth media and exposed to silver and copper exchanged zeolite Y (ranging from 25-1000 μg) for a period of 24 h. The minimum bactericidal concentration (MBC) of silver and copper loaded zeolite-Y powder was 50 and 250 μg for Escherichia coli. Staphylococcus aureus was destroyed at a powder concentration of 100 μg for both Ag-Y and Cu-Y zeolite. Further, the present work also focuses to incorporate 5% silver and copper exchanged zeolite pigment in coating and study the antibacterial effect on the coated 304 stainless coupons. Paint containing copper exchanged zeolite shows antibacterial activity compared to paint with silver containing zeolite.

Adsorptive Desulfurization of Model Gasoline by Using Different Zn Sources Exchanged NaY Zeolites.

A series of Zn-modified NaY zeolites were prepared by the liquid-phase ion-exchange method with different Zn sources, including Zn(NO3)2, Zn(Ac)2 and ZnSO4. The samples were tested as adsorbents for removing an organic sulfur compound from a model gasoline fuel containing 1000 ppmw sulfur. Zn(Ac)2-Y exhibited the best performance for the desulfurization of gasoline at ambient conditions. Combined with the adsorbents’ characterization results, the higher adsorption capacity of Zn(Ac)2-Y is associated with a higher ion-exchange degree. Further, the results demonstrated that the addition of 5 wt % toluene or 1-hexene to the diluted thiophene (TP) solution in cyclohexane caused a large decrease in the removal of TP from the model gasoline fuel. This provides evidence about the competition through the π-complexation between TP and toluene for adsorption on the active sites. The acid-catalyzed alkylation by 1-hexene of TP and the generated complex mixture of bulky alkylthiophenes would adsorb on the surface active sites of the adsorbent and block the pores. The regenerated Zn(Ac)2-Y adsorbent afforded 84.42% and 66.10% of the initial adsorption capacity after the first two regeneration cycles.

Monitoring by in situ neutron diffraction of simultaneous dehydration and Ni2+ mobility in partially exchanged NaY zeolites

The incoherent signal in neutron diffraction patterns allows correlating in real time hydration–dehydration levels and structural changes in zeolites.

Ion Exchange Dependent Electroactive Phase Content and Electrical Properties of Poly(vinylidene fluoride)/Na(M)Y Composites

Different metal ion exchanged NaY zeolite, Na(M)Y, were used to prepare poly(vinylidene fluoride) based composites by solvent casting and melting crystallization. The effect of different metal ion exchanged zeolites on polymer crystallization and electrical properties was reported. Cation–framework interactions and hydration energy of the cations determined that K+ is the most efficient exchanged ion in NaY zeolite, followed by Cs+ and Li+. The electroactive phase crystallization strongly depends on the ions present in the zeolite, leading to variations of the surface energy characteristics of the Na(M)Y zeolites and the polymer chain ability of penetration in the zeolite. Thus, Na(Li)Y and NaY induce the complete electroactive γ-phase crystallization of the crystalline phase of PVDF, while Na(K)Y only induces it partly and Na(Cs)Y is not able to promote the crystallization of the electroactive phase. Furthermore, different ion size/weight and different interaction with the zeolite framework result in significant variations in the electrical response of the composite. In this way, iinterfacial polarization effects in the zeolite cavities and zeolite–polymer interface lead to strong increases of the dielectric constant on the composites with lightest ions weakly bound to the zeolite framework. Polymer composites with Na(Li)Y show the highest dielectric response, followed by NaY and Na(K)Y. Zeolite Na(Cs)Y contributes to a decrease of the dielectric constant of the composite. The results show the relevance of the materials for sensor development.

ChemInform Abstract: Indole Cyanation via C—H Bond Activation under Catalysis of Ru(III)‐Exchanged NaY Zeolite (RuY) as a Recyclable Catalyst.

AbstractIndole substrates react with (II) as a nontoxic, slow cyanide releasing agent in the presence of RuY to yield 3‐cyanated derivatives regioselectively.

P.6.e.004 Smoking, nicotine dependence and anxiety in medical students

This work demonstrated that the catalytic wet oxidation (CWO) of high-strength alcohol-distillery waste liquors is feasible. Two distillery liquors (TOC=10 500; 22 500 mg/l; COD=26 000; 50 000 mg/l) produced by alcohol fermentation of enzymatic hydrolyzates from steam- and ammonia-exploded timothy grass were treated in a batch stirred autoclave over three different catalysts, 1% Pt/Al2O3, Mn/Ce oxides, and Cu(II)-exchanged NaY zeolite. The temperature and oxygen partial pressure ranges were (453–523 K) and (0.5–2.5 MPa), respectively. Effects of temperature, oxygen partial pressure, TOC content, and type of catalyst on the removal of total organic carbon (TOC) were investigated. The CWO initial rates were found to be first-order with respect to TOC, and the activation energies ranged from 34 to 51 kJ/mol. The highest TOC removal was achieved with Mn/Ce oxides and Cu(II)/NaY catalysts. The catalysts were found to be very effective for short contact times, while for prolonged exposures coke laydown was shown to be the prime factor responsible for the loss of catalyst activity. The carbonaceous deposits were characterized by electron spectroscopy for chemical analysis (ESCA) and temperature-programmed oxidation (TPO).

Indole cyanation via CH bond activation under catalysis of Ru(III)-exchanged NaY zeolite (RuY) as a recyclable catalyst

Abstract Selective 3-cyanation of indoles was achieved under heterogeneous catalysis of Ru(III)-exchanged NaY zeolite (RuY) as a recyclable catalyst, in combination with K4[Fe(CN)6] as a nontoxic, slow cyanide releasing agent. Under the aforementioned conditions, good yields of the desired products were obtained.

Study of the Alkylation of Phenol with Methanol on Zn(H)-Exchanged NaY Zeolites

The gas-phase alkylation of phenol with methanol was studied at 473 K on zeolite NaY exchanged with Zn+2 (samples Zn(x)NaY) or H+ (samples Na(x)HY) cations. Zeolite NaY contained only weak and medium Lewis acid sites. The addition of Zn+2 formed essentially strong Lewis acid sites. In contrast, the exchange of NaY with H+ generated Bronsted acid sites and decreased the density of Lewis acid sites. Zeolite NaY was inactive at 473 K, but after its exchange with Zn2+ efficiently promoted the phenol methylation reaction. Phenol conversion and the selectivities to o- and p-cresols increased with the Zn content in the sample. The exchange of Na+ with H+ also activated the parent NaY zeolite. At similar phenol conversion levels, Na(x)HY samples formed more anisole and less cresols than Zn(x)NaY. All the Zn(x)NaY and Na(x)HY samples deactivated on stream, but the catalyst activity decay increased with the exchange degree.

Preparation and characterization of NaY/PVDF hybrid ultrafiltration membranes containing silver ions as antibacterial materials

A novel antibacterial ultrafiltration (UF) membrane obtained by blending poly (vinylidene fluoride) (PVDF) with Ag + exchanged NaY zeolite particles (AgNaY) was prepared using phase inversion methods. The AgNaY hybrid PVDF membranes exhibited excellent and long-lasting antibacterial activity against Escherichia coli ( E. coli) . Its antibacterial activity was improved with increased Ag + content. The hydrophilicity of P-AgNaY-3 was improved with a low contact angle of 81.6°. Compared with P-0, the permeate performance, thermal stability, and mechanical properties of P-AgNaY were improved with a steady bovine serum albumin (BSA) retention above 92%. Antibacterial activity of the membranes against E. coli was measured using the halo zone test. The characterization of AgNaY/PVDF hybrid membranes was investigated by scanning electron microscope, X-ray diffraction, tensile stress tests, thermogravimetric analysis, contact angle tests, pure water flux, and permeation flux.

Synthesis and catalytic performance of a bi-phase core-shell zeolite composite

A zeolite composite Y/Beta with core-shell structure was synthesized by adding tetraethylammonium bromide (TEABr) exchanged NaY zeolite into the pre-reacted mixture used to prepare Beta zeolite. The composite was characterized by XRD, N2 adsorption, SEM, and FTIR spectra of pyridine. The results show that the composite is composed of a core zeolite Y and a shell of intergrown zeolite Beta crystals, representing dual microporous structures of both Y and Beta zeolites and a new mesoporous structure. The composite has a high activity in n-octane catalytic cracking because of the formation of intergrowths and the change of acidity due to the distorted interface and surface defects.

Enhanced Photocatalytic Activity by Silver Metal Ion Exchanged NaY Zeolite Photocatalysts for the Degradation of Organic Contaminants and Dyes in Aqueous Medium

Zeolite-based photocatalyst have been prepared using TiO2-coated NaY zeolite by post-synthesis modification with silver metal ion exchange. The characterization of the catalysts was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), Inductively coupled plasma-optical emission spectrophotometry (ICP), Diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FTIR), and N2 adsorption techniques. The presence of metal ions and TiO2 on zeolite surface was observed by UV-visible diffuse reflectance spectroscopy. It was found that the structure of the support materials is retained after the silver metal ion exchange. The photocatalytic activity of the catalysts was studied by degradation of aqueous nitrobenzene, acetophenone, methylene blue, and malachite green in the presence of UV light. The highest photocatalytic activity was obtained for silver metal ion exchanged photocatalysts coated with TiO2 (2%, w/w) as compared to other silver exchanged NaY zeolite catal...

Magnetic properties of Ni2+ clusters in NaY zeolite

We have investigated the magnetic properties of Ni2+ exchanged NaY zeolite by using a direct current magnetization technique. At T>5 K, the M vs H/T curves superimpose and these curves could be fitted well using a Langevin function with a log-normal distribution of moments. The mean spin-cluster moment has been found to be ∼3.3μB. The deviation from the superposition of the M vs H/T curves is observed at T<5 K indicating the building up of a spin-spin correlation between Ni clusters below 5 K. The zero-field-cooled and field-cooled magnetization curves show branching at low temperatures (T≤5 K) under low applied magnetic fields (H≤1 kOe) with a peak in the zero-field-cooled magnetization curves. A log-normal distribution of spin-freezing/blocking temperature has been observed with mean spin-freezing/blocking temperature ∼3.0 K. The peak temperature Tg decreases with increasing field and follows the de Almeida–Thouless (AT) line [1−Tg(H)/Tg(0)]∝H2/3. The extrapolation of the AT line gives the spin-freezing temperature Tg(0)≈3.29 K.

Rare-earth (Ce 3+, La 3+, Sm 3+, and RE 3+) exchanged Na-Y zeolites and K-10 clay as solid acid catalysts for the synthesis of benzoxazole via Beckmann rearrangement of salicylaldoxime

Rare-earth exchanged (Ce 3+, La 3+, Sm 3+, and RE 3+) Na-Y zeolites, K-10 montmorillonite clay and amorphous silica–alumina have been employed as solid acid catalysts for the vapor phase Beckmann rearrangement of salicylaldoxime to benzoxazole. Rare-earth exchanged Na-Y zeolites were prepared by simple ion-exchange methods. These systems were characterized by energy dispersed X-ray analysis, 27Al and 29Si MAS NMR, FTIR spectroscopy, temperature programmed desorption and surface area and pore volume measurements. The catalysts show both Brönsted and Lewis acidity. Definite correlation between Brönsted acid sites amount obtained from thermodesorption of 2,6-dimethylpyridine and benzoxazole formation in the reaction were observed. Hydrolysis of salicylaldoxime to salicylaldehyde is correlated with Lewis acidity as obtained from hydrocracking of cumene.

Study of superparamagnetic clusters in Co2+-exchanged NaY zeolite

Magnetic properties of Co2+-exchanged NaY zeolite have been investigated using a dc magnetization technique. In the presence of low applied magnetic fields, a difference between zero-field-cooled and field-cooled magnetizations is observed below ∼3.4K. At T>5K, the M vs H∕T curves superimpose and these curves could be fitted well using the Langevin function, which yields a saturation moment of 3.2μB per Co2+ ion and a cluster moment of 6.66μB. This indicates that there are superparamagnetic clusters which are formed due to a positive exchange coupling among the Co2+ ions. For T<5K, the M vs H∕T curves do not superimpose on the curves for T>5K. The analysis of the low-temperature M vs H data suggests the building up of weak antiferromagnetic-type correlation between the superparamagnetic clusters at T<5K.

Magnetic interaction between copper (II) ion and paramagnetic NO and O 2 molecules in Y-type zeolite at low temperature: An EPR study

Electron paramagnetic resonance (EPR) spectra of partially copper ion exchanged Na-Y zeolite (CuNa-FAU) were measured in the presence of paramagnetic gases such as nitrogen monoxide (NO) and oxygen (O 2) as a function of temperature (110–270 K). The EPR signal intensities of the Cu 2+ ions deviated from those predicted by Curie’s paramagnetic law due to the magnetic interaction between the Cu 2+ ions and paramagnetic gaseous molecules adsorbed on the zeolites; the minimum signal intensity was observed at 150–170 K for CuNa-FAU with NO and the maximum intensity was observed at 170–190 K for CuNa-FAU with O 2. The temperature dependent signal intensities, accompanying the NO adsorption, were discussed in terms of the Langmuir adsorption model in the higher temperature range of 150–190 K.

Iron-based heterogeneous catalysts for epoxidation of alkenes using molecular oxygen

Fe 2+-exchanged NaY zeolite and Fe 2+-containing compounds including Fe 3(PO 4) 2 and Fe 3O 4 are efficient heterogeneous catalysts for the epoxidation of alkenes with molecular oxygen in the absence of a sacrificial reductant. Fe 2+ cations existing in the supercages of zeolite Y or on the surface of the Fe 2+-containing compounds probably function as the active sites for the epoxidation with O 2. The solvent plays a crucial role in the epoxidation, and the reactions catalyzed by these iron-based catalysts may proceed via a radical mechanism.

Suzuki cross-coupling reaction of aryl halides with arylboronic acids catalysed by Pd(II)-NaY zeolite

Pd(II)-exchanged NaY zeolite showed high activity in the Suzuki cross-coupling reactions of aryl bromides and iodides without added ligands. The DMF:water ratio, and the type and amount of base were found to be critical for the efficiency of the reaction. The catalyst is reusable after regeneration.

Heck reaction catalyzed by PD-modified zeolites.

[Pd]-exchanged NaY zeolites have been prepared, characterized, and applied for the first time for catalytic carbon-carbon coupling reactions. The catalysts exhibit a high activity and selectivity toward the Heck reaction of aryl bromides with olefins for small palladium concentrations (< or =0.1 mol % of Pd). The catalysts can easily be separated from the reaction mixture and reused after washing without loss in activity. No limitation to the diffusion of adducts in the zeolite cages was observed (for linear alkenes). The electronic nature of the aryl bromides and the olefins has a dominating effect on the reaction yield and selectivity. The heterogeneous catalysts quantitatively convert all types of all aryl bromide (complete conversion of bromobenzene within 30 min) and activated aryl chlorides under standard reaction conditions. Product form selectivity is observed in the Heck reaction with cyclic olefins.

First heterogeneously palladium catalysed α-arylation of diethyl malonate

Pd exchanged NaY zeolites ([Pd(0)]–, [Pd(II)]– and entrapped [Pd(NH 3) 4]) exhibit a good activity towards the α-arylation of carbonyl compounds using different para-substituted aryl bromides. Low Pd-concentrations (only 2 mol%) are required to observe interesting activity. The catalysts can easily be separated from the reaction mixture and reused without any loss in activity. For large-scale applications the alternative use of an insoluble base as K 2CO 3 seems to be promising. The electronic nature of the aryl halides plays a limited role concerning the rate of the reaction.