Zeolites treated with silicon tetrachloride vapour. IV. Acidity

The concentration and properties of the Brönsted and Lewis acid sites in samples of zeolite Y dealuminated with silicon tetrachloride vapour at elevated temperatures are examined using infrared spectroscopy with temperature-controlled sorption/desorption of pyridine and ammonia. Preliminary experiments on dealuminated zeolites omega (synthetic mazzite) and ZSM—5 are also described.     

Photo-degradation of acid green dye over Co-ZSM-5 catalysts prepared by incipient wetness impregnation technique

Co-ZSM-5 catalysts with different Co-loadings (2-30wt.%) were prepared by incipient wetness impregnation method. The prepared solid catalysts were characterized by X-ray diffraction, FTIR, in situ FTIR of pyridine adsorption and surface area measurements. The XRD data presented disintegration in the zeolitic crystalline structure accompanied by an increase in particle size of the prepared solids. New phases, Co(3)O(4) and Co(2)SiO(4), were detected with increasing the Co-loading, which indicate the strong interaction of cobalt ions with the ZSM-5 zeolite. FTIR study proved the presence of Co ions in stabilized sites inside the ZSM-5 framework. The in situ FTIR of adsorbed pyridine determined the type and relative strength of acidity on the surface of the prepared solids. The acidity switched from B-acid sites to L-acid sites with impregnation of cobalt ions in ZSM-5 zeolite. The acidity decreased with increasing Co-loading, which might be due to the destruction of zeolite framework and presence of new phases such as cobalt silicate and cobalt oxide on the surface. The surface texture characteristics changed with the promotion of ZSM-5 by cobalt ions, since a decrease of surface area, mean pore radius and pore volume was observed. The assessment of the catalytic activity was performed by the use of the photo-degradation of acid green (AG) dye as a probe reaction in presence of H(2)O(2) as an oxidant. The pH value controlled the degradation rate since a gradual increase of AG degradation rate was observed with increasing pH value and the optimum H(2)O(2) concentration was 61.6 mmol/l. It was found that, the AG degradation rate increased until an optimum value of Co-loading (ca. 10 wt.%), beyond which a monotonic decrease of reaction rate was recognized. The experimental data pointed to the importance of both the cobalt moieties and the zeolite framework structure in the AG degradation reaction.     

Arsenic adsorption by polyvinyl pyrrolidone K25 coated cassava peel carbon from aqueous solution

Sorption of arsenic from aqueous solution was carried out using polyvinyl pyrrolidone K25 coated cassava peel carbon (PVPCC). Batch experiments were conducted to determine the effect of contact time, initial concentration, pH and desorption. Batch sorption data's were fitted to Lagergren kinetic studies. Column studies were also conducted using PVPCC as adsorbent. The optimized flow rate of 2.5 mL min(-1) and bed height 10 cm were used to determine the effect of metal ion concentration on removal of As(V). BDST model was applied to calculate the adsorption capacity (N(0)) of column. The N(0) value of 2.59 x 10(-5), 4.21 x 10(-5), 4.05 x 10(-5), 4.26 x 10(-5) and 3.2 x 10(-5) mg g(-1) were obtained for 0.5, 1.0, 1.5, 2.0 and 2.5 mg L(-1) of As(V), respectively. The batch sorption proved to be more efficient than the column sorption. The sorption of As(V) and the nature of the adsorbent was examined by Fourier transmission infrared spectroscopy (FTIR) and X-ray diffraction (XRD) studies, respectively.     

Cation–Cation Interaction in Complexes of Np(V) Benzoate and Salicylate with N-Containing Molecular Ligands

Radiochemistry - The hydrothermal method was used to obtain two new compounds of Np(V): benzoate [(NpO2)3(py) (C7H5O2)3(H2O)2] (1) and salicylate [(NpO2)(phen)(HOC7H4O2)] (2), where py = pyridine...     

The nature of 'overexchanged' copper and platinum on zeolites

The uptake of platinum and copper tetra-ammine (PTA and CTA, [(NH(3))(4)Pt](2+) and [(NH(3))(4)Cu](2+)) into zeolites was compared over silica and three zeolites (Y, MOR and MFI) with different points of zero charge and aluminium content. Adsorption was determined as a function of pH at several metal concentrations, and pH shifts relative to metal free control experiments were carefully monitored. The uptake of both metal ammine complexes onto silica is well described by electrostatic adsorption. We suggest that the metal cations interact with zeolites by two mechanisms, ion exchange at the Al exchange sites and electrostatic adsorption at silanol groups. The former is the dominant mechanism at low to mid pH, and the latter at high pH. This effect is most clearly manifested in zeolites with low aluminium content such as ZSM5; electrostatic adsorption at high pH in ZSM5 yields metal loadings much in excess of the ion exchange capacity and so gives rise to 'overexchange'. Differences between PTA and CTA can be explained by the weaker stability of the CTA complex and its response to the decrease in local pH near the adsorption plane of low PZC zeolites. This change in local pH near oxide surfaces is characteristic of electrostatic adsorption. As the local pH decreases, the CTA ion is probably converted to a dimerized copper complex, perhaps Cu(2)(OH)(2)(2+). A portion of the released ammonia is protonated, increasing the solution pH. In high PZC, high aluminium zeolites with high ion exchange capacity, there is relatively little contribution from electrostatic adsorption.     

Preparation and characterization of VO-ZSM5 catalyst for the selective reduction of NO with ammonia

The structural characteristics and catalytic behavior of VO-ZSM5 catalysts, obtained by oxidative degradation of vanadyl acetyl acetonate, were characterized by FTIR spectroscopy and XRD analysis. The organometallic precursor was analysed during the preparation and activation steps. The thermal decomposition of the organometallic compound led to the formation of V-oxides anchored to the aluminosilicate surface in a stressed ligand field instead of an ordered oxide structure. The catalysts which were prepared by impregnation of a planar complex of V on ZSM5 were active for the selective reduction of NO with ammonia.     

玻璃表面PS-r-P4-VP共聚物“刷子”的制备与表征

采用原位活性聚合法在玻璃表面接枝聚苯乙烯与聚4-乙烯吡啶无规共聚物(PS-r-P4-VP)"刷子",并对其进行表征。X射线光电子能谱(XPS)结果表明,玻璃表面接枝共聚物后,Si(1s/2p)、O(1s)的吸收峰强度降低,C(1s)吸收峰强度增强并出现了N(1s)(吡啶环)的特征吸收峰;椭圆偏振仪测试结果表明,接枝PS-r-P4-VP的厚度随聚合时间延长而增加,表面均方粗糙度则减小;原子力显微镜(AFM)观察结果表明,随着St配比的增加,玻璃表面聚合物"刷子"粗糙度降低;红外光谱(FT-IR)表明,玻璃表面的聚合物为PS-r-P4-VP;透光率测试表明,在玻璃表面接枝PS-r-P4-VP并不影响玻璃的透光率;接触角测试结果表明,接枝共聚物的玻璃表面接触角随着St比例的增加而显著增大。     

Antibiofouling thin-film composite membranes (TFC) by in situ formation of Cu-(<Emphasis Type="Italic">m</Emphasis>-phenylenediamine) oligomer complex

In situ formation of a Cu-(m-phenylenediamine) (Cu-mPD) oligomer complex from copper chloride during the interfacial polymerization process was successfully employed to produce modified thin-film composite reverse osmosis membranes (TFC-RO) with antibiofouling properties. Membranes were characterized by field emission scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy, and contact angle measurements. Antibiofouling properties were studied using a colony-forming unit test with Escherichia coli. Moreover, an antiadhesion test was developed using fluorescence microscopy. Membrane performance using a cross-flow cell was evaluated, and copper concentration in permeate water was measured. FTIR, XPS and XRD results confirmed the formation of a Cu-mPD oligomer complex and its incorporation into the polyamide layer. A mechanism for formation of the oligomer within the membrane was proposed based on the interaction between the oxygen of the carbonyl group of the polyamide layer and copper ion of the Cu-mPD oligomer complex. The modified membrane showed a slight decrease in hydrophilicity and higher surface roughness. However, excellent antibacterial and antiadhesion effects were observed, attributed to copper toxicity as a result of Cu²⁺ ions release from the membrane surface. Release of copper ions in the permeate water was determined, and the maximum value observed was considered negligible according to the World Health Organization. The desalination performance of modified membrane showed an important salt rejection with stable water flux. In conclusion, a novel chemical method for the incorporation of Cu-mPD oligomer complex into the polyamide layer of TFC-RO membranes to improve their antibiofouling properties and desalination performance was achieved.     

Solid State Characterization of Stanozolol

A study was undertaken to illustrate the ability to characterize various crystal forms of Stanozolol by by thermal analysis (differential scanning calorimetry-DSC), X-ray powder diffraction (XRPD), and Fourier transform infrared spectroscopy (FTIR). Mixtures of forms I and II were prepared and analyzed by each technique to investigate the strengths and weaknesses of the three methods. The detection of a contaminant polymorph in mixtures of forms I and II was possible by both FTIR and XRPD but not possible by DSC.

Various solvated forms were prepared by recrystallization from methanol, ethanol, 2-propanol, and were shown by thermal gravimetric analysis to exist in a 1:1 stoichiometry with Stanozolol. XRPD analysis of solvates indicated that each solvated form (monohydrate, ethanol solvate, methanol solvate, 2-propanol solvate) exists in a crystal unique with respect to forms I and II.

The concentration of drug in solution for the different crystal forms was determined at room temperature in 2% SLS at 5 and 24 hours. A significantly higher concentration was observed for the form II sample at 5 hours versus the form I and the monohydrate samples. It is likely that the form I sample had converted to the monohydrate form after 5 hours and a maximum concentration would be observed at an earlier time. At 24 hours, both the form I and II samples had converted to the monohydrate form and concentrations of 0.5-0.6 mg/mL were observed for each form. Due to the transformations to the hydrate during solubility studies, meaningful comparisons were difficult.     

Characterization and reactivity of sulfided NiNaY zeolite catalysts for thiophene conversion

The hydrodesulfurization (HDS) of thiophene has been studied in the presence of hydrogen at 613 K in a fixed-bed flow reactor over a series of sulfided Ni-exchanged Y zeolite catalysts. Both oxidic precursors and sulfided catalysts have been characterized by X-ray photoelectron spectroscopy, infrared spectroscopy of NO and pyridine adsorbed probes, and acidity measurements. Sulfidation led to the formation of sulfided Ni²⁺ and, probably, reduced Ni, species that migrated to the external surface layers and to supercages of the zeolite. There is also an important increase of Brönsted acidity. Both HDS (major reaction) and cracking activities increased with increasing Ni content and, therefore, with increasing acidity of the zeolites, and decreased markedly with pyridine poisoning. Precalcination at 873 K or nonsulfidation pretreatments of the Ni-exchanged zeolites led to an important decrease of HDS activity. All the results point out that sulfided Ni-species formed on zeolite are predominantly involved in the HDS of thiophene.     

Coal ash conversion into effective adsorbents for removal of heavy metals and dyes from wastewater

Fly ash was modified by hydrothermal treatment using NaOH solutions under various conditions for zeolite synthesis. The XRD patterns are presented. The results indicated that the samples obtained after treatment are much different. The XRD profiles revealed a number of new reflexes, suggesting a phase transformation probably occurred. Both heat treatment and chemical treatment increased the surface area and pore volume. It was found that zeolite P would be formed at the conditions of higher NaOH concentration and temperature. The treated fly ash was tested for adsorption of heavy metal ions and dyes in aqueous solution. It was shown that fly ash and the modified forms could effectively absorb heavy metals and methylene blue but not effectively adsorb rhodamine B. Modifying fly ash with NaOH solution would significantly enhance the adsorption capacity depending on the treatment temperature, time, and base concentration. The adsorption capacity of methylene blue would increases with pH of the dye solution and the sorption capacity of FA-NaOH could reach 5 x 10(-5) mol/g. The adsorption isotherm could be described by the Langmuir and Freundlich isotherm equations. Removal of copper and nickel ions could also be achieved on those treated fly ash. The removal efficiency for copper and nickel ions could be from 30% to 90% depending on the initial concentrations. The increase in adsorption temperature will enhance the adsorption efficiency for both heavy metals. The pseudo second-order kinetics would be better for fitting the dynamic adsorption of Cu and Ni ions.     

Preparation and application of attapulgite/iron oxide magnetic composites for the removal of U(VI) from aqueous solution

Recently, magnetic sorbents have received considerable attention because of their excellent segregative features and sorption capacities. Herein, attapulgite/iron oxide magnetic (ATP/IOM) composites were prepared and characterized. The sorption results indicated that ATP/IOM composites were superior to ATP and iron oxides individually for the removal of U(VI) from aqueous solution. Based on X-ray photoelectron spectroscopy (XPS) analysis and surface complexation model, the main sorption species of U(VI) on ATP were==X(2)UO(2)(0) below pH 4.0 and==S(s)OUO(2)(+), ==S(w)OUO(2)CO(3)(-), and==S(w)OUO(2)(CO(3))(2)(3-) above pH 5.0. However the prevalent species on ATP/IOM composites were==S(s)OUO(2)(+) and==S(w)OUO(2)(CO(3))(2)(3-) over the observed pH range. ATP/IOM composites are a promising candidate for pre-concentration and immobilization of radionuclides from large volumes of aqueous solutions, as required for remediation purposes.     

Experimental Study on Energy Dissipation Characteristics of ZSM‐5 Zeolite/Water System

Interaction with liquids at the ultra‐large surface area of nanoporous material enables a high‐efficiency energy dissipation system with wide perspective applications [A. Han, et al., Langmuir 2008, 24, 7044]. In this paper, a nanoporous energy dissipation system composed of a mixture of zeolite ZSM‐5 and water is established and studied experimentally. Firstly, quasi‐static compression experiments are carried out to analyze the pressure–volume curve and reveal the energy dissipation mechanism. Afterwards, a parametric study is conducted to explore the effects of three parameters, the pretreatment temperature of zeolite ZSM‐5 (600–1100 °C), mass ratio of ZSM‐5 to water (1:5–6:5), and average zeolite particle size (2.145–5.251 µm before heated or 6.104–9.557 µm after heated). Results show that in order to obtain optimum energy absorption performance, the pretreatment temperature of about 1000 °C, and higher ratio of ZSM‐5 with larger particle size are desired. With high energy dissipation and reusability, the zeolite‐water system with optimal parameters established herein may become an attractive cushioning device.     

Study of structural transformations in potassium-exchanged zeolite A induced by thermal and mechanochemical treatments

Thermal transformations of potassium-exchanged zeolite A and the X-ray amorphous material obtained by ball milling the potassium-exchanged zeolite A were investigated by different methods, such as differential thermogravimetric analysis (DTA), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Controlled heating of crystalline, potassium-exchanged zeolite A causes a phase transformation in the sequence: [0.22 Na2O, 0.78 K2O]·Al2O3·2SiO2·3.48 H2Oamorphouskalsilite+kaliophilite, while the heating of mechanochemically amorphous potassium-exchanged zeolite A results in its transformation into a mixture of kalsilite and kaliophilite. The differences in the pathways of the transformation processes are discussed in terms of the structural properties of the starting materials.     

Suppressing Al_2O_3 nanoparticle coarsening and Cu nanograin growth of milled nanostructured Cu-5vol.%Al_2O_3 composite powder particles by doping with Ti

Both the coarsening of Al_2O_3 nanoparticles and the growth of Cu nanograins of mechanically milled nanostructured Cu-5 vol.%Al_2O_3 composites with, and without, trace amounts of Ti during annealing at973 K for 1 h were investigated. It was found that doping with a small amount of Ti(e.g. 0.2 wt%) in a nanostructured Cu-5 vol.%Al_2O_3 composite effectively suppressed the coarsening of Al_2O_3 nanoparticles during exposure at this temperature. Further, the Ti addition also prevented the concomitant abnormal growth of the copper grains normally caused by the coarsening of the Al_2O_3 nanoparticles. Energy dispersive X-ray spectroscopy analysis of the Al_2O_3 nanoparticles in the annealed Cu-5 vol.%Al2 O3-0.2 wt%Ti sample suggested that the Ti atoms either diffused into the Al_2O_3 nanoparticles or segregated to the Cu/Al_2O_3 interfaces to form Ti-doped Al_2O_3 nanoparticles, which was more stable than Ti-free Al_2O_3 nanoparticles during annealing at high homologous temperatures.     

Characteristics of titania supported copper oxide catalysts for wet air oxidation of phenol

Various techniques have been used to characterize the CuO(x)/TiO(2) catalysts with different copper loading. Surface area, pore volume and pore size distribution of the prepared catalysts were estimated from nitrogen adsorption isotherm. Temperature programmed reduction (TPR), X-ray diffraction (XRD), electron spin resonance (ESR), X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) experiments were performed to investigate the chemical state of the copper species. The chemical state of copper in the CuO(x)/TiO(2) catalysts varied with copper loading (1-25wt.%): highly dispersed Cu(2+) cluster for 1 and 5wt.%, and bulk CuO for 7-25wt.%. The activity and mineralization selectivity of the CuO(x)/TiO(2) catalysts increased with copper loading up to 20wt.%, and remained almost constant for higher copper loading. The optimum copper loading was 20wt.% for the wet air oxidation of phenol over the CuO(x)/TiO(2) catalysts in this work. The stability of the CuO(x)/TiO(2) catalysts with different copper loading was also studied with respect to carbonaceous deposits and copper leaching.     

Phase transformation behaviours and shape memory characteristics of Ti-45xNi-5Cu-xMo x=0.3-1.0 alloys

Abstract

Transformation behaviours and shape memory characteristics in Ti-45xNi-5Cu-xMo x=0.3, 0.5, or 1.0 at.- alloys were investigated by means of electrical resistivity measurements, differential scanning calorimetry, X-ray diffraction, thermal cycling tests under constant load, and tensile tests. The two stage transformation B2-B19-B19 occurred in Ti-45xNi-5Cu-xMo alloys, and complete separation of the B2-B19 transformation from the B19-B19 transformation was observed in Ti-44.0Mo-5Cu-1.0Mo at.- alloy. Substitution of Mo for Ni in Ti-45Ni-5Cu at.- alloy increased the critical stress for slip deformation and the pseudoelastic recovery. The maximum recoverable elongations of Ti-44.7Ni-5Cu-0.3Mo at.- and Ti-44.5Ni-5Cu-0.5Mo at.- alloys were 6.4 and 7 respectively.     

气相沉积聚合法制备聚酰亚胺绝缘薄膜及其性能研究

以联苯四酸二酐和4,4’-二氨基二苯醚为单体原料使用气相沉积聚合(VDP)法制备了聚酰亚胺(PI)绝缘膜,分析不同热亚胺化处理温度对PI薄膜绝缘性能的影响。分别使用红外光谱、俄歇能谱、扫描电镜、原子力显微镜对薄膜成分以及薄膜表面形貌进行了表征;利用超高阻微电流测试仪测试了PI复合绝缘膜漏电流和电压击穿特性。结果表明:热亚胺化300℃/1 h真空(1.0×10-2Pa)处理后的PI绝缘膜内部结构致密,当场强为8.0MV/cm时漏电流密仅为8.2×10-5A/cm2;薄膜击穿场强达到8.42MV/cm,表明PI薄膜具有良好的电学性能以及热稳定性。     

Dihydrogen Activation by Titanium Sulfide Complexes

The titanocene sulfido complex Cp*(2)Ti(S)py (1, Cp* = pentamethylcyclopentadienyl; py = pyridine) is synthesized by addition of a suspension of S(8) to a toluene solution of Cp*(2)Ti-(CH(2)CH(2)) (2) and py. The rate of rotation of the pyridine ligand in solution was determined by (1)H NMR spectroscopy, and the structure of 1 was determined by X-ray crystallography. Complex 1 reacts reversibly with dihydrogen to give Cp*(2)Ti(H)SH (6) and py. Reaction of 1 with HD gives an equilibrium mixture of Cp*(2)Ti(D)SH and Cp*(2)Ti(H)SD; H(2) and D(2) are not formed in this reaction. 1D (1)H NMR magnetization transfer spectra and 2D EXSY (1)H NMR spectra of 6 in the presence of H(2) show that in solution the H(2), hydride, and hydrosulfido hydrogen atoms exchange. A four-center mechanism for this exchange is proposed. The EXSY studies show that the Ti-H and S-H hydrogens exchange with each other more rapidly than either of those hydrogens exchanges with external H(2). A transient dihydrogen complex intermediate is proposed to explain this observation. The infrared spectrum of 6 shows an absorption assigned to the Ti-H stretching mode at 1591 cm(-1) that shifts upon deuteration to 1154 cm(-1). Reaction of 1 with trimethylsilane, diethylsilane, or dimethylsilane gives Cp*(2)-Ti(H)SSiMe(3) (7), Cp*(2)Ti(H)SSiHEt(2) (8), or Cp*(2)Ti(H)SSiHMe(2) (9), respectively. The isotope effect for the reaction producing 7 has been measured, and a mechanism is proposed. Treatment of 1 with an additional equivalent of S(8) results in the formation of the disulfide Cp*(2)Ti(S(2)) (4). Acetylene inserts into the Ti-S bond of 4 to produce the vinyl disulfide complex 5. The structures of 4 and 5 have been determined by X-ray diffraction. Compound 4 reacts with 2 in the presence of py to produce 1. Phosphines react with 4 in the presence of H(2) to provide 6 and the corresponding phosphine sulfide. Reaction of hydrogen with 4 gives Cp*(2)-Ti(SH)(2) (3). The reactions of 1 and 4 with dihydrogen provide a model for possible mechanisms of H(2) activation by metal-sulfide hydrodesulfurization catalysts.     

The interaction of vanadium and nickel in USY zeolite

The interaction of vanadium and nickel in USY zeolite has been investigated by X-ray diffraction, nitrogen sorption, Fourier-transform infrared spectroscopy, temperature-programmed reduction, and n-hexane cracking reaction. There is an interaction existing, either direct or indirect through nonframework aluminum, between vanadium and nickel. This leads to the inhibition effect for vanadium and nickel to affect the catalytic and physical-chemical properties of USY zeolite. Nickel can inhibit the destruction of USY zeolite caused by vanadium. Vanadium can suppress the coke formation due to the presence of nickel.