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1

Copper-containing zeolite catalysts  

DOEpatents

A catalyst useful in the conversion of nitrogen oxides or in the synthesis of nitriles or imines from amines, formed by preparing an intimate mechanical mixture of a copper (II)-containing species, such as CuO or CuCl.sub.2, or elemental copper, with a zeolite having a pore mouth comprising 10 oxygen atoms, such as ZSM-5, converting the elemental copper or copper (II) to copper (I), and driving the copper (I) into the zeolite.

Price, Geoffrey L. (Baton Rouge, LA); Kanazirev, Vladislav (Sofia, BG)

1996-01-01

2

Copper-containing zeolite catalysts  

DOEpatents

A catalyst useful in the conversion of nitrogen oxides or in the synthesis of nitriles or imines from amines, is formed by preparing an intimate mechanical mixture of a copper (II)-containing species, such as CuO or CuCl{sub 2}, or elemental copper, with a zeolite having a pore mouth comprising 10 oxygen atoms, such as ZSM-5, converting the elemental copper or copper (II) to copper (I), and driving the copper (I) into the zeolite.

Price, G.L.; Kanazirev, V.

1996-12-10

3

Copper-Exchanged Zeolite L Traps Oxygen  

NASA Technical Reports Server (NTRS)

Brief series of simple chemical treatments found to enhance ability of zeolite to remove oxygen from mixture of gases. Thermally stable up to 700 degrees C and has high specific surface area which provides high capacity for adsorption of gases. To increase ability to adsorb oxygen selectively, copper added by ion exchange, and copper-exchanged zeolite reduced with hydrogen. As result, copper dispersed atomically on inner surfaces of zeolite, making it highly reactive to oxygen, even at room temperature. Reactivity to oxygen even greater at higher temperatures.

Sharma, Pramod K.; Seshan, Panchalam K.

1991-01-01

4

Kinetics and thermodynamics of copper ions removal from wastewater by use of zeolite.  

PubMed

Natural Bulgarian zeolite was tested for its ability to remove Cu2+ from model wastewater. Influence of process variables was investigated. It was found that the optimum wastewater to zeolite ratio is 100:1 and the optimum pH value of water to be treated is 5.5 to 7.5. Zeolite with finer particles shows a higher uptake capacity. The simultaneous presence of Ca2+ and Mg2+ in concentrations similar to their concentrations in Bulgarian natural water does not significantly influence the uptake of Cu2+. Zeolite modification by treating it with NaCl, CH3COONa and NaOH increases its uptake ability. Copper ions are strongly immobilized by modified zeolite and secondary pollution of water caused by its contact with preloaded zeolite is very low (1.5-2.5% of Cu2+ preliminary immobilized have been released back into acidified water). Contacting with 2 mol dm(-3) NaCl can easily regenerate loaded zeolite; best results were obtained for zeolite modified with NaCl. Requirements of Bulgarian standards for industrial wastewater can be met by a one-stage process for an initial Cu2+ concentration of 10 mg dm(-3), and by a two stage process for an initial Cu2+ concentration of 50 mg dm(-3). Uptake of Cu2+ by zeolite from neutral wastewater has proved to be as effective as Cu2+ removal by precipitation of copper hydroxide. The process of Cu2+ uptake by natural zeolite is best described by the kinetic equation for adsorption. This fact, together with the correlation found between the Cu2+ uptake and the amount of Na+, Ca2+ and K+ released into solution by zeolite shows that the ion exchange sorption plays the basic role in Cu2+ uptake by natural zeolite. The value obtained for the apparent activation energy (26.112 kJ mol(-1) implies that the process can be easily carried out with a satisfactory rate. The uptake equilibrium is best described by the Langmuir adsorption isotherm, with Langmuir constants KL= 6.4 x 10(-2) dm3 mg(-1) and M = 6.74 mg g(-1). The apparent equilibrium constant found shows moderate affinity of zeolite for Cu2+. Values of deltaG degrees and deltaH degrees found show the spontaneous and endothermic nature of the process of Cu2+ uptake by natural zeolite. PMID:11530923

Panayotova, M I

2001-01-01

5

Copper cation removal in an electrokinetic cell containing zeolite.  

PubMed

Zeolites are used in environmental remediation of soil or water to immobilize or remove toxic materials by cation exchange. An experiment was conducted to test the use a low electric field to direct the toxic cations towards the zeolite. An electrokinetic cell was constructed using carbon electrodes. Synthetic Linde Type A (LTA) zeolite was placed in the cell. Copper(II) chloride dissolved in water was used as a contaminant. The Cu(2+) concentration was measured for ten hours with and without an applied electric field. The removal of the Cu(2+) ions was accelerated by the applied field in the first two hours. For longer time, the electric field did not improve the removal rate of the Cu(2+) ions. The presence of zeolite and applied electric field complicates the chemistry near the cathode and causes precipitation of Cu(2+) ions as copper oxide on the surface of the zeolite. With increased electric field the zeolite farther away from the cathode had little cation exchange due to the higher drift velocity of the Cu(2+) ions. The results also show that, in the LTA Zeolite A pellets, the cation exchange of Cu is limited to a shell of several tens of micrometers. PMID:21109348

Elsayed-Ali, Omar H; Abdel-Fattah, Tarek; Elsayed-Ali, Hani E

2011-01-30

6

Copper removal using bio-inspired polydopamine coated natural zeolites.  

PubMed

Herein, for the first time, natural clinoptilolite-rich zeolite powders modified with a bio-inspired adhesive, polydopamine (PDA), have been systematically studied as an adsorbent for copper cations (Cu(II)) from aqueous solution. Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) revealed successful grafting of PDA onto the zeolite surface. The effects of pH (2-5.5), PDA treatment time (3-24h), contact time (0 to 24h) and initial Cu(II) ion concentrations (1 to 500mgdm(-3)) on the adsorption of Cu(II) ions were studied using atomic absorption spectroscopy (AAS) and neutron activation analysis (NAA). The adsorption behavior was fitted to a Langmuir isotherm and shown to follow a pseudo-second-order reaction model. The maximum adsorption capacities of Cu(II) were shown to be 14.93mgg(-1) for pristine natural zeolite and 28.58mgg(-1) for PDA treated zeolite powders. This impressive 91.4% increase in Cu(II) ion adsorption capacity is attributed to the chelating ability of the PDA on the zeolite surface. Furthermore studies of recyclability using NAA showed that over 50% of the adsorbed copper could be removed in mild concentrations (0.01M or 0.1M) of either acid or base. PMID:24731937

Yu, Yang; Shapter, Joseph G; Popelka-Filcoff, Rachel; Bennett, John W; Ellis, Amanda V

2014-05-30

7

Modification of Synthetic Zeolite Pellets from Lignite Fly Ash A : The Pelletization  

Microsoft Academic Search

The possibility of the use of synthetic zeolites from coal fly ash as adsorbent in water purification has also been investigated in a number of studies but the development of its another form with more appropriate for real industrial application has not been clarified adequately. This study focuses on modification zeolite synthesized from coal fly ash in pellet form by

Chaiwat Rongsayamanont; Khajornsak Sopajaree

8

Zeolites  

NASA Technical Reports Server (NTRS)

Zeolites are crystalline aluminosilicates that have complex framework structures. However, there are several features of zeolite crystals that make unequivocal structure determinations difficult. The acquisition of reliable structural information on zeolites is greatly facilitated by the availability of high-quality specimens. For structure determinations by conventional diffraction techniques, large single-crystal specimens are essential. Alternatively, structural determinations by powder profile refinement methods relax the constraints on crystal size, but still require materials with a high degree of crystalline perfection. Studies conducted at CAMMP (Center for Advanced Microgravity Materials Processing) have demonstrated that microgravity processing can produce larger crystal sizes and fewer structural defects relative to terrestrial crystal growth. Principal Investigator: Dr. Albert Sacco

1992-01-01

9

Removal of zinc, copper and lead by natural zeolite-a comparison of adsorption isotherms.  

PubMed

An uptake of zinc (Zn), copper (Cu), and lead (Pb) from aqueous solutions by ion exchange on natural zeolitic tuff has been studied. The Croatian zeolite clinoptilolite from the Donje Jesenje deposit has been used as a natural ion exchanger. The efficiency of removal is higher for Pb and Cu than for Zn ions. Measured concentrations of Si in the liquid phase identify the detachment of the aluminosilicate structure during ion exchange in the presence of H(+) and OH(-) ions. The adsorption isotherm equations; Langmuir-Freundlich, Redlich-Petersen, Toth, Dubinin-Radushkevich, modified Dubinin-Radushkevich, and Lineweawer-Burk were derived from the basic empirical equations, and used for calculation of ion exchange parameters. The best fitting of experimental results to the proposed isotherms was observed in models that assume that ionic species bind first at energetically most favorable sites, with multi-layer adsorption taking place subsequently. PMID:15026244

Peri?, J; Trgo, M; Vukojevi? Medvidovi?, N

2004-04-01

10

Internal surface modification of zeolite MFI particles and membranes for gas separation  

NASA Astrophysics Data System (ADS)

Zeolites are a well-known class of crystalline oxide materials with tunable compositions and nanoporous structures, and have been used extensively in catalysis, adsorption, and ion exchange. The zeolite MFI is one of the well-studied zeolites because it has a pore size and structure suitable for separation or chemical conversion of many industrially important molecules. I synthesized MFI membranes with [h0h] out-of-plane orientation on ?-alumina supports. The membranes were modified by the same procedures as used for MFI particles and with 1-butanol, 3-amino-1-propanol, 2-[(2-aminoethyl)amino]ethanol, and benzenemethanol. The existence of functional groups in the pores of the zeolite was confirmed by PA-FTIR measurements. Permeation measurements of H2, N2, CO2, CH 4, and SF6, were performed at room temperature before and after modification. Permeation of n-butane, and i-butane were measured before and after modification with 1-butanol. For all of the studied gases, gas permeances decreased by 1-2 orders of magnitude compared to bare MFI membranes for modified membranes. This is a strong indication that the organic species in the MFI framework are interacting with or blocking the gas molecule transport through the MFI pores. The CO2/CH 4 permeation selectivity was close to the Knudsen selectivity (0.6) for the membranes before modification. CO2/CH4 selectivity increased for MFI/benzenemethanol modified membrane (1.0), whereas it decreased for the MFI/2-[(2-aminoethyl)amino]ethanol modified membrane (0.5). MFI/benzenemethanol crystals were shown to have a highest sorption capacity for CH4, whereas, MFI/2-[(2-aminoethyl)amino]ethanol crystals were shown to have a highest sorption capacity for CO2 over all other studied molecules Higher sorption of CH4 in MFI/benzenemethanol and higher sorption of CO2 in MFI/2-[(2-aminoethyl)amino]ethanol and their strong binding to the modified membrane are likely the reasons for observing higher and lower CO2/CH4 permeation selectivity respectively, compared to bare MFI membrane. A further detailed fundamental study of the CO2 adsorption mechanism in modified zeolites is necessary to gain a better understating of the adsorption and permeation behavior of such materials. For the organic molecules with only one functional group (1-butanol, benzenemethanol, and 1-propaneamine), physical adsorption was found - as intuitively expected - to be the only observed mode of attachment of CO2 to the modified zeolite material. Even in the case of MFI modified with 1,3-diaminopropane, only physical adsorption is seen. This is explained by the isolated nature of the amine groups in the material, due to which only a single amine group can interact with a CO2 molecule. On the other hand, chemisorbed CO2 species are clearly observed on bare MFI, and on MFI modified with 3-amino-1-propanol or 2-[(2-aminoethyl)amino]ethanol. Specifically, these are carbonate-like species that arise from the chemisorption of CO2 to the silanol group in bare MFI and the alcohol groups of the modifying molecule. The possibility of significant contributions from external surface silanol groups in adsorbing CO2 chemisorbed species was ruled out by a comparative examination of the FTIR spectra of 10 ?m and 900 nm MFI particles modified with 2-[(2-aminoethyl)amino]ethanol. (Abstract shortened by UMI.).

Kassaee, Mohamad H.

11

Kinetics of Copper Adsorption from Effluent Stream by ZeoliteNaX  

NASA Astrophysics Data System (ADS)

The batch experiments were conducted to study the copper (II) removal by ZeoliteNaX at temperature of 288+1 K, adsorbent dose of 2 g/L and contact time of 24 hour. Effects of pH, temperature, contact time and Cu (II) ion concentration by the adsorbent were investigated. The data were analyzed using the Langmuir, Freundlich and Temkin isotherms. Freundlich isotherm was found to correlate the adsorption of Cu (II) better and the mono-layer adsorption capacity for Cu (II) removal was 41.6 mg/g. The adsorbed amounts of Cu (II) reached equilibrium within 150 minutes. The four adsorption kinetic models namely, the first order equation, second order equations, pseudo-first order equation and pseudo second-order equations were also tested to fit the data. The pseudo-first-order equation was found to fit best for the experimental data. Thermodynamic analysis indicated the spontaneous and endothermic nature of the adsorption of Cu (II) by ZeoliteNaX.

Singh, Surinder; Sambi, S. S.; Sharma, S. K.; Pandey, Pankaj Kumar

2010-06-01

12

Corrosion resistance properties of superhydrophobic copper surfaces fabricated by one-step electrochemical modification process  

NASA Astrophysics Data System (ADS)

Superhydrophobic copper surfaces have been prepared by a one-step electrochemical modification process in an ethanolic stearic acid solution. In this work, the corrosion properties of hydrophobic copper surface and superhydrophobic copper surfaces were analyzed by means of electrochemical analyses and compared with that of as-received bare copper substrate. The decrease of corrosion current density (icorr) as well as the increase of polarization resistance (Rp) obtained from potentiodynamic polarization curves revealed that the superhydrophobic film on the copper surfaces improved the corrosion resistance performance of the copper substrate.

Huang, Ying; Sarkar, D. K.; Gallant, Danick; Chen, X.-Grant

2013-10-01

13

Antimicrobial properties of zeolite-X and zeolite-A ion-exchanged with silver, copper, and zinc against a broad range of microorganisms.  

PubMed

Zeolites are nanoporous alumina silicates composed of silicon, aluminum, and oxygen in a framework with cations, water within pores. Their cation contents can be exchanged with monovalent or divalent ions. In the present study, the antimicrobial (antibacterial, anticandidal, and antifungal) properties of zeolite type X and A, with different Al/Si ratio, ion exchanged with Ag(+), Zn(2+), and Cu(2+) ions were investigated individually. The study presents the synthesis and manufacture of four different zeolite types characterized by scanning electron microscopy and X-ray diffraction. The ion loading capacity of the zeolites was examined and compared with the antimicrobial characteristics against a broad range of microorganisms including bacteria, yeast, and mold. It was observed that Ag(+) ion-loaded zeolites exhibited more antibacterial activity with respect to other metal ion-embedded zeolite samples. The results clearly support that various synthetic zeolites can be ion exchanged with Ag(+), Zn(2+), and Cu(2+) ions to acquire antimicrobial properties or ion-releasing characteristics to provide prolonged or stronger activity. The current study suggested that zeolite formulations could be combined with various materials used in manufacturing medical devices, surfaces, textiles, or household items where antimicrobial properties are required. PMID:24242073

Demirci, Selami; Ustao?lu, Zeynep; Y?lmazer, Gonca Alt?n; Sahin, Fikrettin; Baç, Nurcan

2014-02-01

14

Copper oxide modified NaY zeolite: Efficient catalysts for degrading N-nitrosopyrrolidine  

Microsoft Academic Search

A series of CuO modified zeolites samples were prepared by use of the methods like calcination, microwave radiation and impregnation. Their catalytic behaviors in degradation of N-nitrosopyrrolidine (NPYR) were investigated by temperature programmed surface reaction (TPSR), pulse reaction, and the technique of XRD, TPD, XPS and TG-MS etc. The degradation temperature of NPYR on CuO\\/NaY(imp) was lowered and the maximum

H. D. Liu; S. L. Zhou; Y. Wang; Y. Xu; Y. Cao; J. H. Zhu

2004-01-01

15

Copper stabilization by zeolite synthesis in polluted soils treated with coal fly ash  

SciTech Connect

This paper reports on the process of zeolite formation in an agricultural soil artificially polluted by high amounts of Cu (15 mg of Cu/g of soil dry weight) and treated with fused coal fly ash at 30 and 60 C and how this process affects the mobility and availability of the metal. As a consequence of the treatment, the amount of dissolved Cu, and thus its mobility, was strongly reduced, and the percentage of the metal stabilized in the solid phase increased over time, reaching values of 30% at 30{sup o}C and 40% at 60{sup o}C. The physicochemical phenomena responsible for Cu stabilization in the solid phase have been evaluated by EDTA sequential extractions and synchrotron radiation based X-ray microanalytical techniques. These techniques were used for the visualization of the spatial distribution and the speciation of Cu in and/or on the neo-formed zeolite particles. In particular, micro XRF (X-ray fluorescence) tomography showed direct evidence that Cu can be entrapped as clusters inside the porous zeolitic structures while -{mu}XANES (X-ray absorption near edge structure) spectroscopy determinations revealed Cu to be present mainly as Cu(II) hydroxide and Cu(II) oxide. The reported results could be useful as a basic knowledge for planning new technologies for the on-site physicochemical stabilization of heavy metals in heavily polluted soils. 32 refs., 5 figs.

Roberto Terzano; Matteo Spagnuolo; Luca Medici; Bart Vekemans; Laszlo Vincze; Koen Janssens; Pacifico Ruggiero [University of Bari, Bari (Italy). Dipartimento di Biologia e Chimica Agro-forestale ed Ambientale

2005-08-15

16

Topotactic conversion of ?-helix-layered silicate into AST-type zeolite through successive interlayer modifications.  

PubMed

AST-type zeolite with a plate morphology can be synthesized by topotactic conversion of a layered silicate (?-helix-layered silicate; HLS) by using N,N-dimethylpropionamide (DPA) to control the layer stacking of silicate layers and the subsequent interlayer condensation. Treatment of HLS twice with 1)?hydrochloric acid/ethanol and 2)?dimethylsulfoxide (DMSO) are needed to remove interlayer hydrated Na ions and tetramethylammonium (TMA) ions in intralayer cup-like cavities (intracavity TMA ions), both of which are introduced during the preparation of HLS. The utilization of an amide molecule is effective for the control of the stacking sequence of silicate layers. This method could be applicable to various layered silicates that cannot be topotactically converted into three-dimensional networks by simple interlayer condensation by judicious choice of amide molecules. PMID:24431158

Asakura, Yusuke; Takayama, Ryosuke; Shibue, Toshimichi; Kuroda, Kazuyuki

2014-02-10

17

Surface modification of calcium-copper hydroxyapatites using polyaspartic acid  

NASA Astrophysics Data System (ADS)

Mixed calcium-copper hydroxyapatite (Ca-CuHAp), with general formula Ca(10-x)Cux(PO4)6(OH)2, where 0 ? x ? 0.75 was prepared in aqueous medium in the presence of different concentrations of poly-L-aspartic acid (PASP). XRD, IR, TG-DTA, TEM-EDX, AFM and chemical analyses were used to characterize the structure, morphology and composition of the products. All techniques show the formation of new hybrid compounds Ca-CuHAp-PASP. The presence of the grafting moiety on the apatitic material is more significant with increasing of copper amount and/or organic concentration in the starting solution. These increases lead to the affectation of apatite crystallinity. The IR spectroscopy shows the conservation of (Psbnd OH) band of (HPO4)2- groups, suggesting that PASP acid was interacted only with metallic cations of hydroxyapatite.

Othmani, Masseoud; Aissa, Abdallah; Bachoua, Hassen; Debbabi, Mongi

2013-01-01

18

Surface modification of copper using high intensity, 1015 W/cm2, femtosecond laser in vacuum  

NASA Astrophysics Data System (ADS)

A study of copper target surface modification with high intensity (1015 W/cm2, fluence of ˜300 J/cm2) Ti:sapphire laser, operating at 800 nm wavelength and pulse duration of 60 fs is presented. The Cu surface variations were studied in vacuum ambience. The copper target specific surface changes and phenomena observed are: (i) creation of craters (with extra-low diameters); (ii) formation of periodic surface structures especially expressed at the reduced intensity; (iii) presence of the "clean" surface in the irradiated zone (mainly absence of the oxide(s)), and (iv) occurrence of plasma in front the surface, emitting predominantly X-ray radiation (soft and hard). It can be concluded from this study that the reported laser intensities can effectively be applied for copper surface modification. The appearance of plasma in front of the target, irradiating in the X-ray/UV region, offers additional effect of surface purification facilitating contaminant-free conditions which is highly important for specific applications, e.g. in microelectronics. Generally, femtosecond laser surface modification of copper is non-contact and very rapid compared to traditional modification methods.

Momcilovic, M.; Limpouch, J.; Kmetik, V.; Redaelli, R.; Savovic, J.; Batani, D.; Stasic, J.; Panjan, P.; Trtica, M.

2012-09-01

19

Surface modification of medical metals by ion implantation of silver and copper  

Microsoft Academic Search

Implant related infections remain a concern in modern surgery. Surface modification is an effective way to reduce the occurrence of these complications. Of various techniques, ion implantation shows promise. In the present work, silver and copper were ion implanted separately, into three typical medical metals, namely 317L stainless steel, titanium, and Ti–Al–Nb by a MEVVA ion source machine at various

Y. Z. Wan; S. Raman; F. He; Y. Huang

2007-01-01

20

First principle study of selective catalytic nitrogen oxide reduction over copper-exchanged zeolites  

NASA Astrophysics Data System (ADS)

Cu-ZXM5 is as promising catalyst candidate for mobile source (auto truck) NOX emission control. The present work studies this phenomenon from different perspectives. Firstly, a methodology is developed to validate the proposed NO decomposition mechanism with a kinetic Reactor model. The Reactor model involves a plug flow reactor that simulates forty-two elementary reactions. The simulation operates at moderate temperatures (300-1000 K) and the results are compared with micro-reactor experimental results. Secondly, gas phase reaction of NO with NH3 in the thermal deNOX process is studied to reveal origins of ammonia's selectivity for NO over O2. The gas phase study does electronic comparison of the competing reactions of NH3 radical with NO and O2 respectively. NH3 selectivity lies in strongly bound H2NNO adduct that readily rearranges and decompose to N2 and H2O. The pronounced discrimination of NH3 against reaction with O2 is explored through comparison of the electronic structures of the H2NNO and H2NOO radical adducts and provides insight into the selectivity of NH3 in the surface reactions. Thirdly, thermal chemistry of selective catalytic reduction (SCR) of NOX with ammonia over Cu-exchanged zeolites is investigated with density functional theory (DFT). The catalytic reaction pathways are mapped out and compared with those in the gas phase reactions, which reveals that the major activation barriers are lowered in the catalytic reactions.

Sun, Donghai

21

Preparation and characterization of surfactant-modified hydroxyapatite/zeolite composite and its adsorption behavior toward humic acid and copper(II).  

PubMed

A novel composite material, i.e., surfactant-modified hydroxyapatite/zeolite composite, was used as an adsorbent to remove humic acid (HA) and copper(II) from aqueous solution. Hydroxyapatite/zeolite composite (HZC) and surfactant-modified HZC (SMHZC) were prepared and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and field emission scanning electron microscope. The adsorption of HA and copper(II) on SMHZC was investigated. For comparison purposes, HA adsorption onto HZC was also investigated. SMHZC exhibited much higher HA adsorption capacity than HZC. The HA adsorption capacity for SMHZC decreased slightly with increasing pH from 3 to 8 but decreased significantly with increasing pH from 8 to 12. The copper(II) adsorption capacity for SMHZC increased with increasing pH from 3 to 6.5. The adsorption kinetic data of HA and copper(II) on SMHZC obeyed a pseudo-second-order kinetic model. The adsorption of HA and copper(II) on SMHZC took place in three different stages: fast external surface adsorption, gradual adsorption controlled by both film and intra-particle diffusions, and final equilibrium stage. The equilibrium adsorption data of HA on SMHZC better fitted to the Langmuir isotherm model than the Freundlich isotherm model. The equilibrium adsorption data of copper(II) on SMHZC could be described by the Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. The presence of copper(II) in solution enhanced HA adsorption onto SMHZC. The presence of HA in solution enhanced copper(II) adsorption onto SMHZC. The mechanisms for the adsorption of HA on SMHZC at pH 7 may include electrostatic attraction, organic partitioning, hydrogen bonding, and Lewis acid-base interaction. The mechanisms for the adsorption of copper(II) on SMHZC at pH 6 may include surface complexation, ion exchange, and dissolution-precipitation. The obtained results indicate that SMHZC can be used as an effective adsorbent to simultaneously remove HA and copper(II) from water. PMID:22961484

Zhan, Yanhui; Lin, Jianwei; Li, Jia

2013-04-01

22

Surface modification of an epoxy resin with polyamines and polydopamine: The effect on the initial electroless copper deposition  

NASA Astrophysics Data System (ADS)

This paper describes the influence of polydopamine and polyamine surface modifications of an etched epoxy cresol novolak (ECN) resin on the initial electroless copper deposition. Three different strategies to introduce polyamines on a surface in aqueous environment are applied: via polyethyleneimine adsorption (PEI), via polydopamine and via polyamines grafted to polydopamine. Next, the influence of these surface modifications on the catalytic palladium activation is investigated through X-ray photoelectron spectroscopy (XPS) analysis. Finally, the initial electroless copper deposition on modified epoxy surfaces is evaluated using SEM and Energy Dispersive Spectroscopy (EDS). Grafted polyamines on polydopamine surface modifications result in a large increase of the initial deposited copper.

Schaubroeck, David; Mader, Lothar; De Geyter, Nathalie; Morent, Rino; Dubruel, Peter; Vanfleteren, Jan

2014-06-01

23

Removal of lead, copper, nickel, cobalt, and zinc from water by a cancrinite-type zeolite synthesized from fly ash  

Microsoft Academic Search

As a low Si\\/Al ratio zeolite, cancrinite received very scant study in previous studies on the adsorption removal of heavy metals from water. In this study, a cancrinite-type zeolite (ZFA) was synthesized from Class C fly ash via the molten-salt method. Adsorption equilibriums of Pb2+, Cu2+, Ni2+, Co2+, and Zn2+ on ZFA were studied in aqueous solutions and were well

Wei Qiu; Ying Zheng

2009-01-01

24

Zeolite A functionalized with copper nanoparticles and graphene oxide for simultaneous electrochemical determination of dopamine and ascorbic acid.  

PubMed

A novel Cu-zeolite A/graphene modified glassy carbon electrode for the simultaneous electrochemical determination of dopamine (DA) and ascorbic acid (AA) has been described. The Cu-zeolite A/graphene composites were prepared using Cu(2+) functionalized zeolite A and graphene oxide as the precursor, and subsequently reduced by chemical agents. The composites were characterized by X-ray diffraction, Fourier transform infrared spectra and scanning electron microscopy. Based on the Cu-zeolite A/graphene-modified electrode, the potential difference between the oxidation peaks of DA and AA was over 200mV, which was adequate for the simultaneous electrochemical determination of DA and AA. Also the proposed Cu-zeolite/graphene-modified electrode showed higher electrocatalytic performance than zeolite/graphene electrode or graphene-modified electrode. The electrocatalytic oxidation currents of DA and AA were linearly related to the corresponding concentration in the range of 1.0×10(-7)-1.9×10(-5)M for DA and 2.0×10(-5)-2.0×10(-4)M for AA. Detection limits (S/N=3) were estimated to be 4.1×10(-8)M for DA and 1.1×10(-5)M for AA, respectively. PMID:22819046

He, Ping; Wang, Wei; Du, Licheng; Dong, Faqin; Deng, Yuequan; Zhang, Tinghong

2012-08-20

25

Conversion of trypsin to a copper enzyme: tyrosinase/catechol oxidase by chemical modification.  

PubMed

New active sites can be introduced into naturally occurring enzymes by the chemical modification of specific amino acid residues in concert with genetic techniques. Chemical strategies have had a significant impact in the field of enzyme design such as modifying the selectivity and catalytic activity which is very different from those of the corresponding native enzymes. Thus, chemical modification has been exploited for the incorporation of active site binding analogs onto protein templates and for atom replacement in order to generate new functionality such as the conversion of a hydrolase into a peroxidase. The introduction of a coordination complex into a substrate binding pocket of trypsin could probably also be extended to various enzymes of significant therapeutic and biotechnological importance. The aim of this study is the conversion of trypsin into a copper enzyme: tyrosinase by chemical modification. Tyrosinase is a biocatalyst (EC.1.14.18.1) containing two atoms of copper per active site with monooxygenase activity. The active site of trypsin (EC 3.4.21.4), a serine protease was chemically modified by copper (Cu(+2)) introduced p-aminobenzamidine (pABA- Cu(+2): guanidine containing schiff base metal chelate) which exhibits affinity for the carboxylate group in the active site as trypsin-like inhibitor. Trypsin and the resultant semisynthetic enzyme preparation was analysed by means of its trypsin and catechol oxidase/tyrosinase activity. After chemical modification, trypsin-pABA-Cu(+2) preparation lost 63% of its trypsin activity and gained tyrosinase/catechol oxidase activity. The kinetic properties (K(cat), K(m), K(cat)/K(m)), optimum pH and temperature of the trypsin-pABA-Cu(+2) complex was also investigated. PMID:20024799

Okutucu, Burcu; Zeytunluoglu, Ali; Zihnioglu, Figen

2010-01-01

26

Zeolite Studies. Aluminium Phosphate Zeolites.  

National Technical Information Service (NTIS)

Alpo-zeolites (ALPO sub 4 -zeolites) have been synthesized by hydrothermal synthesis in an autoclave from alumina, tetralkylammonium hydroxide and phosphorus acid. Catalysis tests with hydrocarbons indicate that the compounds have good olefinisomerization...

G. S. Haegh, U. Blindheim

1983-01-01

27

Luminescent materials derived from the surface-modification of Ln3+-doped zeolite L with a silylated terpyridine  

NASA Astrophysics Data System (ADS)

Herein we report luminescent materials of Ln3+ (Ln = Eu or Tb) doped disc shaped zeolite L crystals (Eu3+/ZLD, Tb3+/ZLD) modified with a silylated terpyridine (Terpy-Si). The modified crystals show bright red emission and green emission under UV-light irradiation due to the energy transfer from the Terpy-Si to the Eu3+ and Tb3+ ions. The obtained materials were characterized with FT-IR, SEM, XRD and elemental analysis. Luminescence spectroscopy was used to study the luminescence properties of the modified Eu3+(Tb3+)/ZLD crystals. The formation of europium(III) and terbium(III) Terpy-Si silicon complexes and energy transfer from Terpy-Si to Eu3+ ions and Tb3+ have been confirmed by luminescence spectroscopy.

Qin, Zhiqiao; Li, Hongshi; Wang, Yige

2014-11-01

28

Thermal behavior of natural zeolites  

SciTech Connect

Thermal behavior of natural zeolites impacts their application and identification and varies significantly from zeolite to zeolite. Zeolites evolve H{sub 2}0 upon heating, but recent data show that distinct ``types`` of water (e.g., loosely bound or tightly bound zeolitic water) do not exist. Rather water is bound primarily to extra-framework cations with a continuum of energies, giving rise to pseudocontinuous loss of water accompanied by a dynamic interaction between remaining H{sub 2}0 molecules and extra-framework cations. These interactions in the channels of zeolites give rise to dehydration dependent on the extra-framework cation, in addition to temperature and water vapor pressure. The dehydration reaction and the extra-framework cation also affect the thermal expansion/contraction. Most zeolites undergo dehydration-induced contractions that may be anisotropic, although minor thermal expansion can be seen with some zeolites. Such contractions can be partially or completely irreversible if they involve modifications of the tetrahedral framework and/or if rehydration is sluggish. Thermally induced structural modifications are also driven initially by dehydration and the concomitant contraction and migration of extra-framework cations. Contraction is accommodated by rotations of structural units and tetrahedral cation-oxygen linkages may break. Thermal reactions that involve breaking of tetrahedral cation-oxygen bonds markedly irreversible and may be kinetically limited, producing large differences between short- and long-term heating.

Bish, D.L.

1993-09-01

29

Calcium- and ammonium ion-modification of zeolite amendments affects the metal-uptake of Hieracium piloselloides in a dose-dependent way.  

PubMed

The role of natural zeolite and of two types of modified zeolite (with ammonium and with calcium ions) in reducing the accumulation of ions of heavy metals in roots and leaves of Hieracium piloselloides grown on tailing ponds was investigated. The variation of the content of zeolite (5% w/w and 10% w/w) is another parameter that significantly and positively affects the accumulation of the metal ions in Hieracium piloselloides. The results showed that zeolite used as an amendment in the soil in tailing ponds significantly reduces the accumulation of heavy metal ions in Hieracium piloselloides. The highest concentrations of heavy metals were accumulated in plants grown on soil without zeolite, being followed by the plants grown on the substrate with natural zeolite. Moreover, the translocation factors of heavy metal ions uptake in roots and leaves grown on substrates with modified zeolites are lower than those calculated for the organs grown on the substrate amended with natural zeolite. This behaviour has demonstrated the positive effect of those changes of zeolite amendments in the potential phytoremediation practice. PMID:22898921

Peter, Anca; Mihaly-Cozmuta, Leonard; Mihaly-Cozmuta, Anca; Nicula, Camelia; Indrea, Emil; Tutu, Hlanganani

2012-10-26

30

Ginkgo Biloba Extract (EGb 761) Protects Human Low-Density Lipoproteins against Oxidative Modification Mediated by Copper  

Microsoft Academic Search

The antioxidant effects of Ginkgo biloba extract (EGb 761) on copper-mediated human low density lipoprotein (LDL) oxidative modification were evaluated by several techniques. Human LDL (0.5 mg\\/ml) in phosphate buffered saline, pH 7.4, was incubated with 10 ?M cupric sulfate at 37°C under air for 8 hours and 24 hours in the presence of varying concentrations of EGb 761. Increases

L. J. Yan; M. T. Droylefaix; L. Packer

1995-01-01

31

Zealous zeolites  

Microsoft Academic Search

Zeolites have made significant inroads in fluid cracking catalysts for gasoline and have pushed phosphates out of laundry detergents. But these crystalline aluminosilicate structures are just beginning to make their mark in chemical processes and environmental applications. Ideally suited for work as molecular sieves and catalysts, zeolites sport uniform surface pores and channels that are receptive only to molecules of

1996-01-01

32

Copper on-top-sputtering induced modification of tin dioxide thin film gas sensors  

Microsoft Academic Search

Thin film gas sensors based on pure tin dioxide were modified by sputtering of copper on the surface of the films. A gradual increase of an amount of the on-top-Cu produced increasing doping with uniform distribution of copper throughout entire tin oxide film. An increase of an amount of Cu caused continuous variation of the clean air resistance and the

A Galdikas; A Mironas; A Šetkus; W Göpel; K.-D Schierbaum

1999-01-01

33

Modification of H-ZSM-5 zeolites with phosphorus. 2. Interaction between phosphorus and aluminum studied by solid-state NMR spectroscopy  

Microsoft Academic Search

A suite of one- and two-dimensional solid-state NMR methods was used to follow the complex structural changes in different types of phosphorus species in P-ZSM-5 zeolites that were generated upon treatment of H-ZSM5 zeolites with 0–15% P2O5, followed by calcination or calcination and steaming. Through space and through bond 27Al–31P correlations were used for the first time to study the

K. Damodaran; J. W. Wiench; S. M. Cabral de Menezes; Y. L. Lam; J. Trebosc; J.-P. Amoureux; M. Pruski

2006-01-01

34

Inactivation of high and low pathogenic avian influenza virus H5 subtypes by copper ions incorporated in zeolite-textile materials.  

PubMed

The effect of cotton textiles containing Cu(2+) held by zeolites (CuZeo-textile) on the inactivation of H5 subtype viruses was examined. Allantoic fluid (AF) containing a virus (AF virus) (0.1 ml) was applied to the textile (3×3-cm), and incubated for a specific period at ambient temperature. After each incubation, 0.9 ml of culture medium was added followed by squeezing to recover the virus into the medium. The recovered virus was titrated using Madin-Darby canine kidney (MDCK) cells or 10-day-old embryonated chicken eggs. The highly pathogenic H5N1 and the low pathogenic H5N3 viruses were inactivated on the CuZeo-textile, even after short incubation. The titer of A/chicken/Yamaguchi/7/04 (H5N1) in MDCK cells and in eggs declined by >5.0 log(10) and 5.0 log(10), respectively, in 30 s. The titer of A/whooper swan/Hokkaido/1/08 (H5N1) in MDCK cells declined by 2.3 and 3.5 in 1 and 5 min, respectively. When A/whistling swan/Shimane/499/83 (H5N3) was treated on the CuZeo-textile for 10 min, the titer declined by >5.0 log(10) in MDCK cells and by >3.5 log(10) in eggs. In contrast, no decrease in the titers was observed on cotton textiles containing zeolites alone (Zeo-textile). Neither cytopathic effects nor NP antigens were detected in MDCK cells inoculated with the H5N1 virus treated on the CuZeo-textile. The viral genes (H5, N1, M, and NP) were amplified from the virus treated on the CuZeo-textile by RT-PCR. The hemagglutinating activity of the CuZeo-textile treated virus was unaffected, indicating that virus-receptor interactions were maintained. Electron microscopic analysis revealed a small number of particles with morphological abnormalities in the H5N3 virus samples recovered immediately from the CuZeo-textile, while no particles were detectable in the 10-min treated sample, suggesting the rapid destruction of virions by the Cu(2+) in the CuZeo-textile. The loss of infectivity of H5 viruses could, therefore, be due to the destruction of virions by Cu(2+). Interestingly, CuCl(2) treatment (500 and 5000 ?M) did not have an antiviral effect on the AF viruses (H5N1 and H5N3) even after 48 h of incubation, although the titer of the purified H5N3 virus treated with CuCl(2) declined greatly. The antiviral effect was inhibited by adding the AF to the purified H5N3 virus prior to the CuCl(2) treatment. The known antibacterial/antifungal activities of copper suggest that the CuZeo-textile can be applied at a high level of hygiene in both animals and humans. PMID:22179064

Imai, Kunitoshi; Ogawa, Haruko; Bui, Vuong Nghia; Inoue, Hiroshi; Fukuda, Jiro; Ohba, Masayoshi; Yamamoto, Yu; Nakamura, Kikuyasu

2012-02-01

35

Modification of soil microbial activity and several hydrolases in a forest soil artificially contaminated with copper  

NASA Astrophysics Data System (ADS)

Soils have long been exposed to the adverse effects of human activities, which negatively affect soil biological activity. As a result of their functions and ubiquitous presence microorganisms can serve as environmental indicators of soil pollution. Some features of soil microorganisms, such as the microbial biomass size, respiration rate, and enzyme activity are often used as bioindicators of the ecotoxicity of heavy metals. Although copper is essential for microorganisms, excessive concentrations have a negative influence on processes mediated by microorganisms. In this study we measured the response of some microbial indicators to Cu pollution in a forest soil, with the aim of evaluating their potential for predicting Cu contamination. Samples of an Ah horizon from a forest soil under oakwood vegetation (Quercus robur L.) were contaminated in the laboratory with copper added at different doses (0, 120, 360, 1080 and 3240 mg kg-1) as CuCl2×2H2O. The soil samples were kept for 7 days at 25 °C and at a moisture content corresponding to the water holding capacity, and thereafter were analysed for carbon and nitrogen mineralization capacity, microbial biomass C, seed germination and root elongation tests, and for urease, phosphomonoesterase, catalase and ß-glucosidase activities. In addition, carbon mineralization kinetics were studied, by plotting the log of residual C against incubation time, and the metabolic coefficient, qCO2, was estimated. Both organic carbon and nitrogen mineralization were lower in polluted samples, with the greatest decrease observed in the sample contaminated with 1080 mg kg-1. In all samples carbon mineralization followed first order kinetics; the C mineralization constant was lower in contaminated than in uncontaminated samples and, in general, decreased with increasing doses of copper. Moreover, it appears that copper contamination not only reduced the N mineralization capacity, but also modified the N mineralization process, since in the contaminated samples all of the inorganic nitrogen was present as ammonium, probably because of inhibition of nitrification. There was a marked decrease in biomass-C with addition of copper, and the decrease was more acute at intermediate doses (average decrease, 73%). Despite the decreases in microbial biomass and mineralized C, the value of qCO2 increased after the addition of copper. Urease activity was strongly affected by the presence of copper and the decrease was proportional to the dose; the activity at the highest dose was only 96% of that in the uncontaminated sample. Phosphomonoesterase activity was also affected by addition of copper; the reduction in activity was less than for urease and the greatest reduction was observed for the dose of 1080 mg kg-1 of copper. Catalase activity was affected by the contamination, but no clear trend was observed in relation to the dose of copper. ß-glucosidase was scarcely modified by the contamination but an increase in activity was observed at the highest dose of copper. Seed germination was not affected by copper contamination, since it only showed a clear decrease for the sample contaminated with the highest dose of copper, while root elongation decreased sharply with doses higher than 120 mg kg-1 of copper. The combined germination-elongation index followed a similar pattern to that of root elongation. For all investigated properties showing a reduction of more than 50%, the response to copper contamination was fitted to a sigmoidal dose-response model, in order to estimate the ED50 values. The ED50 values were calculated for microbial biomass, urease, root elongation and germination-elongation index, and similar values were obtained, ranging from 340 to 405 mg kg-1 Cu. The ED50 values may therefore provide a good estimation of soil deterioration.

Bellas, Rosa; Leirós, M? Carmen; Gil-Sotres, Fernando; Trasar-Cepeda, Carmen

2010-05-01

36

Superhydrophilic surface modification of copper surfaces by Layer-by-Layer self-assembly and Liquid Phase Deposition of TiO(2) thin film.  

PubMed

A new method has been developed for the superhydrophilic surface modification of copper using versatile solution-based fabrication techniques. The high surface area of TiO(2) nanoparticles was exploited to create a thin film with increased surface energy that transformed copper materials from relatively hydrophobic to superhydrophilic. Copper exposed to ambient conditions resulting in a thin layer of copper oxide has a water contact angle near 90°, but following TiO(2) modification, the contact angle dropped to 0°. The thin film responsible for this drastic improvement in wettability proved durable by retaining its excellent properties throughout an extended application of thermal stress. SEM and Raman Spectroscopic analysis confirmed the structural integrity of the film before and after a durability test. PMID:21047640

McDonald, Benjamin T; Cui, Tianhong

2011-02-01

37

Modifications in the Morphological and Chemical Properties of Copper Supported on Different Allotropic Forms of Carbon  

Microsoft Academic Search

A combination of techniques including controlled atmosphere electron microscopy coupled within situelectron diffraction has been used to follow the manner by which the nature of a carbonaceous support can impact both the chemistry and morphological properties of small copper particles when treated in various gas environments. We have found that the ease of reduction of CuO is dependent upon the

J. Ma; N. M. Rodriguez; M. A. Vannice; R. T. K. Baker

1999-01-01

38

Copper  

MedlinePLUS

... copper status and certain CVD risk markers in young healthy women. Br J Nutr. 2005;94:231-236. Cassileth B. The Alternative Medicine Handbook: The Complete Reference Guide to Alternative and Complementary Therapies. New York, NY: W.W. Norton; 1998. Castillo-Durán C, Fisberg M, ...

39

Effect of Sliding Speed on Surface Modification and Tribological Behavior of Copper–Graphite Composite  

Microsoft Academic Search

In practice, the sliding speed is an important parameter for materials applied in sliding condition. We have conducted an\\u000a experimental study to explore the effect of sliding speed on friction and wear performance of a copper–graphite composite.\\u000a The sliding tests were carried out over a wide range of speeds with a pin-on-disc configuration. The results show that there\\u000a is a

Wenlin Ma; Jinjun Lu

2011-01-01

40

Modification of H-ZSM-5 zeolites with phosphorus. 1. Identification of aluminum species by 27Al solid-state NMR and characterization of their catalytic properties  

Microsoft Academic Search

Aluminum species in P-ZSM-5 zeolites were identified and quantified using 27Al MAS and MQMAS NMR methods. Samples containing between 0% and 15% P2O5 were studied after calcination or calcination followed by steaming. In addition to the tetrahedral framework aluminum, Altet-f, and the octahedral aluminum, Aloct, we also observed significant quantities of highly distorted aluminum with tetrahedral coordination, Altet-dis, and octahedrally

S. M. Cabral de Menezes; Y. L. Lam; K. Damodaran; M. Pruski

2006-01-01

41

Design and fabrication of zeolite macro- and micromembranes  

NASA Astrophysics Data System (ADS)

The chemical nature of the support surface influences zeolite nucleation, crystal growth and elm adhesion. It had been demonstrated that chemical modification of support surface can significantly alter the zeolite film and has a good potential for large-scale applications for zeolite membrane production. The incorporation of titanium and vanadium metal ions into the structural framework of MFI zeolite imparts the material with catalytic properties. The effects of silica and metal (i.e., Ti and V) content, template concentration and temperature on the zeolite membrane growth and morphology were investigated. Single-gas permeation experiments were conducted for noble gases (He and Ar), inorganic gases (H2, N2, SF6) and hydrocarbons (methane, n-C4, i-C4) to determine the separation performance of these membranes. Using a new fabrication method based on microelectronic fabrication and zeolite thin film technologies, complex microchannel geometry and network (<5 mum), as well as zeolite arrays (<10 mum) were successfully fabricated onto highly orientated supported zeolite films. The zeolite micropatterns were stable even after repeated thermal cycling between 303 K and 873 K for prolonged periods of time. This work also demonstrates that zeolites (i.e., Sil-1, ZSM-5 and TS-1) can be employed as catalyst, membrane or structural materials in miniature chemical devices. Traditional semiconductor fabrication technology was employed in micromachining the device architecture. Four strategies for the manufacture of zeolite catalytic microreactors were discussed: zeolite powder coating, uniform zeolite film growth, localized zeolite growth, and etching of zeolite-silicon composite film growth inhibitors. Silicalite-1 was also prepared as free-standing membrane for zeolite membrane microseparators.

Chau, Lik Hang Joseph

2001-07-01

42

Kinetics of zeolite dealumination in steam  

SciTech Connect

Zeolite dealumination is a well known phenomenon that contributes to the deactivation or activation of catalysts in several different applications. The most obvious effect is in acid catalysis where dealumination under reaction conditions removes the Broensted sites, thus deactivating the catalyst. The authors are interested in the use of cation exchanged zeolites as selective reduction catalysts for removal of NO{sub x} from exhaust streams, particularly from automotive exhaust. In this case, copper exchanged ZSM-5 has been shown to be an effective catalyst for the generic reaction of NO{sub x} with hydrocarbons. However, high temperature and steam in combustion exhaust causes dealumination and consequent migration of copper out of the zeolite structure resulting in rapid deactivation of the catalyst. Dealumination of zeolites has been reported by many authors in uncountable papers and cannot be reviewed here. However, to the authors` knowledge there are no reports on the kinetics of dealumination under varying conditions of temperature and steam. By measuring the kinetics of dealumination with different zeolites and exchange cations they expect to develop working models of the dealumination process that will allow control of zeolite deactivation. This manuscript is a description of the basic techniques used and a progress report on the very beginning of this study.

Hughes, C.D.; Labouriau, A.; Crawford, S.N.; Romero, R.; Quirin, J.; Earl, W.L.

1998-08-01

43

Atomic hydrogen modification of copper surfaces studied by helium atom scattering  

NASA Astrophysics Data System (ADS)

The structure and bonding of single crystal copper surfaces under irradiation by H atoms is investigated by helium atom scattering under UHV conditions. The effect of H atoms on Cu?Cu bonding is deduced from the temperature dependence of the intensity of the specular He reflection from a clean Cu(110) surface and for irradiation with an effusive H atom beam. The Debye temperature deduced from the attenuation of the specular reflection decreases from 340 ± 10 K to 287 ± 10 K upon exposure to hydrogen atoms, implying a decrease in the surface Rayleigh phonon frequency by the H?Cu interaction. Also, the chemical reduction of a Cu(100)-(2 2× 2) R45°- O surface by irradiation with H atoms at 723 K is investigated. H atoms are shown to be an effective means for removing oxide impurities from Cu surfaces.

Miyake, T.; Petek, H.

1997-11-01

44

Modified zeolites as catalysts in the Friedel-Crafts acylation  

Microsoft Academic Search

Modified zeolites were found to be active catalysts in the Friedel-Crafts acylation of anisole by acetyl chloride and acetic anhydride. The effect of two different modifications of the zeolites were tested; lanthanum-exchange and varying the SiAl ratio. For the rare-earth modified zeolites, the activity was found to be dependent on the lanthanum content, and the yield increased with the level

Kristin Gaare; Duncan Akporiaye

1996-01-01

45

Relative importance of calcium and magnesium in hardness-based modification of copper toxicity  

SciTech Connect

Because of the relationship between water hardness and the toxicity of many metals, total hardness is used as a model parameter to calculate ambient water quality criteria for copper and other metals. However, the relative contribution of the Ca and Mg components of total hardness as modifiers of metals toxicity is not considered in the water quality criteria. Acute Cu toxicity was measured in rainbow trout (Oncorhynchus mykiss) and chinook salmon (O. tshawytscha) swim-up fry in laboratory waters that were formulated to have similar total hardness and alkalinity but different Ca and Mg concentrations. Experiments were performed at nominal total hardness values of 40 and 90 mg/L (as CaCO{sub 3}). In four paired toxicity tests, acute Cu toxicity was significantly lower, i.e., 96-h LC50s were higher, in laboratory waters containing proportionately more Ca (Ca:Mg molar ratios of 1.5--5.2) than in waters containing less Ca (Ca:Mg molar ratios of 0.2--0.8). the relative increase in the 96-h Cu LC50 at higher Ca concentrations, but similar total hardness concentrations, was between 29 and 86% when the low Ca treatment was similar to American Society for Testing and Materials laboratory water. Failure to account for differences in Ca when matching or adjusting for total hardness thus exerts an important influence on the prediction of metal toxicity. These differences must be addressed in water-effect ratio testing in which paired tests with laboratory and site waters are conducted.

Welsh, P.G.; Lipton, J.; Chapman, G.A.; Podrabsky, T.L.

2000-06-01

46

Investigation of the possibility of intermediate formation of allyl alcohol in the process of oxidative acetoxylation of propylene on a palladium-copper zeolite catalyst  

SciTech Connect

The formation of allyl acetate in reactions of oxidative acetoxylation of propylene by labeled acetic acid and esterification of labeled acetic acid by allyl alcohol on a Pd, Cu-zeolite catalyst occur with complete conservation of the labeled oxygen of the original labeled acetic acid in the reaction product. The authors propose a reaction scheme for the oxidative acetoxylation of propylene, providing for the formation of allyl alcohol as an intermediate compound, present in a chemisorbed state in the form of a complex with a Pd atom. The gas-phase oxidative acetoxylation of propylene is an industrial method of producing allyl acetate.

Minachev, K.M.; Chizhov, O.S.; Kadentsev, V.I.; Kharlamov, V.V.; Nefedov, O.M.; Rodin, A.N.

1985-12-10

47

Layered zeolitic materials: an approach to designing versatile functional solids.  

PubMed

Relevant layered zeolites have been considered in this perspective article from the point of view of the synthesis methodologies, materials characterization and catalytic implications, considering the unique physico-chemical characteristics of lamellar materials. The potential of layered zeolitic precursors to generate novel lamellar accessible zeolites through swelling, intercalation, pillarization, delamination and/or exfoliation treatments is studied, showing the chemical, functional and structural versatility exhibited by layered zeolites. Recent approaches based on the assembly of zeolitic nanosheets which act as inorganic structural units through the use of dual structural directing agents, the selective modification of germanosilicates and the direct generation of lamellar hybrid organic-inorganic aluminosilicates are also considered to obtain layered solids with well-defined functionalities. The catalytic applications of the layered zeolites are also highlighted, pointing out the high accessibility and reactivity of active sites present in the lamellar framework. PMID:24457617

Díaz, Urbano; Corma, Avelino

2014-07-21

48

Interfacial studies of bimetallic corrosion in copper/ruthenium systems and silicon surface modification with organic and organometallic chemistry  

NASA Astrophysics Data System (ADS)

To form Cu interconnects, dual-damascene techniques like chemical mechanical planarization (CMP) and post-CMP became inevitable for removing the "overburden" Cu and for planarizing the wafer surface. During the CMP processing, Cu interconnects and barrier metal layers experience different electrochemical interactions depending on the slurry composition, pH, and ohmic contact with adjacent metal layers that would set corrosion process. Ruthenium as a replacement of existing diffusion barrier layer will require extensive investigation to eliminate or control the corrosion process during CMP and post CMP. Bimetallic corrosion process was investigated in the ammonium citrate (a complexing agent of Cu in CMP solutions) using micro test patterns and potentiodynamic measurements. The enhanced bimetallic corrosion of copper observed is due to noble behavior of the ruthenium metal. Cu formed Cu(II)-amine and Cu(Il)citrate complexes in alkaline and acidic solutions and a corrosion mechanism has been proposed. The currently used metallization process (PVD, CVD and ALD) require ultra-high vacuum and are expensive. A novel method of Si surface metallization process is discussed that can be achieved at room temperature and does not require ultra-high vacuum. Ruthenation of Si surface through strong Si-Ru covalent bond formation is demonstrated using different ruthenium carbonyl compounds. RBS analysis accounted for monolayer to sub-monolayer coverage of Si surface. Interaction of other metal carbonyl (like Fe, Re, and Rh) is also discussed. The silicon (111) surface modifications with vinyl terminated organic compounds were investigated to form self-assembled monolayers (SAMs) and there after these surfaces were further functionalized. Acrylonitrile and vinylbenzophenone were employed for these studies. Ketone group of vinylbenzophenone anchored to Si surface demonstrated reactivity with reducing and oxidizing agents.

Nalla, Praveen Reddy

49

ZEOLITES: EFFECTIVE WATER PURIFIERS  

EPA Science Inventory

Zeolites are known for their adsorption, ion exchange and catalytic properties. Various natural zeolites are used as odor and moisture adsorbents and water softeners. Due to their acidic nature, synthetic zeolites are commonly employed as solid acid catalysts in petrochemical ind...

50

BTX abatement using Chilean natural zeolite: the role of Brønsted acid sites.  

PubMed

In wastewater treatment facilities, air quality is not only affected by conventional unpleasant odour compounds; toxic volatile organic compounds (VOCs) are also found. In this study, the adsorptive capacity of Chilean natural zeolite toward VOC removal was evaluated. Moreover, the influence of zeolite chemical surface properties on VOC elimination was also investigated. Three modified zeolite samples were prepared from a natural Chilean zeolite (53% clinoptilolite, 40% mordenite and 7% quartz). Natural and modified zeolite samples were characterised by nitrogen adsorption at 77 K, elemental analyses and X-ray fluorescence (XRF). Chemical modifications of natural zeolite showed the important role of Brønsted acid sites on the abatement of VOCs. The presence of humidity has a negative effect on zeolite adsorption capacity. Natural zeolites could be an interesting option for benzene, toluene and xylene vapour emission abatement. PMID:22907462

Alejandro, S; Valdés, H; Manero, M-H; Zaror, C A

2012-01-01

51

Metal Oxide/Zeolite Combination Absorbs H2S  

NASA Technical Reports Server (NTRS)

Mixed copper and molybdenum oxides supported in pores of zeolite found to remove H2S from mixture of gases rich in hydrogen and steam, at temperatures from 256 to 538 degree C. Absorber of H2S needed to clean up gas streams from fuel processors that incorporate high-temperature steam reformers or hydrodesulfurizing units. Zeolites chosen as supporting materials because of their high porosity, rigidity, alumina content, and variety of both composition and form.

Voecks, Gerald E.; Sharma, Pramod K.

1989-01-01

52

Kesetimbangan Adsorpsi Optional Campuran Biner Cd(II) dan Cr(III) dengan Zeolit Alam Terimpregnasi 2-merkaptobenzotiazol  

Microsoft Academic Search

Natural zeolite is one of adsorbents widely used in adsorption processes to treat water polution caused by heavy metal waste. In some cases, the modification of the zeolit active surface is important to improve its adsorpability and its selectivity. Characteristic of modified natural zeolite can be obtained from the analysis of adsorption equilibrium data which useful for adsorption process design.

Amun Amri; M Fahrurozi; Lab. Pemisahan; Dan Pemurnian

53

Plasmon-Related Modification of Spectral Kinetic Properties of Copper Phthalocyanine Thin Films in the Presence of Silver Nanoparticles*  

NASA Astrophysics Data System (ADS)

We have studied the relaxation dynamics for hot electrons in hybrid layered nanocomposites based on island films of silver and copper phthalocyanine. Using femtosecond kinetic spectroscopy, we have shown that the fast component of the bleaching relaxation kinetics in the spectral region corresponding to the absorption bands of copper phthalocyanine correlates with the recovery kinetics for surface plasmon resonance absorption of the silver nanoparticles. This suggests that the fast relaxing bleaching recorded in the absorption bands of copper phthalocyanine and its dynamics are not due to a change in the populations of the energy states of copper phthalocyanine but rather to a change in the state of the plasmon nanoparticles, as a result of their excitation by femtosecond pulses and subsequent relaxation.

Buganov, O. V.; Zamkovets, A. D.; Ponyavina, A. N.; Tikhomirov, S. A.

2014-03-01

54

Single step modification of copper electrode for the highly sensitive and selective non-enzymatic determination of glucose  

Microsoft Academic Search

A non-enzymatic sensor was developed for the determination of glucose in alkaline medium by anodisation of copper in sodium\\u000a potassium tartrate solution. The morphology of the modified copper electrode was studied by scanning electron microscopy,\\u000a and its electrochemical behavior by cyclic voltammetry and electrochemical impedance spectroscopy. The electrode enables direct\\u000a electrocatalytic oxidation of glucose on a CuO\\/Cu electrode at 0.7

T. G. Satheesh Babu; T. Ramachandran; Bipin Nair

2010-01-01

55

Assessment of the Antiviral Properties of Zeolites Containing Metal Ions  

Microsoft Academic Search

The antiviral properties of zeolite (sodium aluminosilicate) powders amended with metal ions were assessed using human coronavirus\\u000a 229E, feline infectious peritonitis virus (FIPV), and feline calicivirus F-9. Zeolites containing silver and silver\\/copper\\u000a caused significant reductions of coronavirus 229E after 1 h in suspension. The silver\\/copper combination yielded a >5.13-log10 reduction within 24 h. It was also the most effective (>3.18-log10) against FIPV

Kelly R. Bright; Enue E. Sicairos-Ruelas; Patricia M. Gundy; Charles P. Gerba

2009-01-01

56

A novel urea conductometric biosensor based on zeolite immobilized urease.  

PubMed

A new approach was developed for urea determination where a thin film of silicalite and zeolite Beta deposited onto gold electrodes of a conductometric biosensor was used to immobilize the enzyme. Biosensor responses, operational and storage stabilities were compared with results obtained from the standard membrane methods for the same measurements. For this purpose, different surface modification techniques, which are simply named as Zeolite Membrane Transducers (ZMTs) and Zeolite Coated Transducers (ZCTs) were compared with Standard Membrane Transducers (SMTs). Silicalite and zeolite Beta with Si/Al ratios 40, 50 and 60 were used to modify the conductometric electrodes and to study the biosensor responses as a function of changing zeolitic parameters. During the measurements using ZCT electrodes, there was no need for any cross-linker to immobilize urease, which allowed the direct evaluation of the effect of changing Si/Al ratio for the same type of zeolite on the biosensor responses for the first time. It was seen that silicalite and zeolite Beta added electrodes in all cases lead to increased responses with respect to SMTs. The responses obtained from ZCTs were always higher than ZMTs as well. The responses obtained from zeolite Beta modified ZMTs and ZCTs increased as a function of increasing Si/Al ratio, which might be due to the increased hydrophobicity and/or the acid strength of the medium. PMID:21807206

Kirdeciler, Salih Kaan; Soy, Esin; Oztürk, Seçkin; Kucherenko, Ivan; Soldatkin, Oleksandr; Dzyadevych, Sergei; Akata, Burcu

2011-09-15

57

Removal of Ca2+ and Zn2+ from aqueous solutions by zeolites NaP and KP.  

PubMed

Zeolites P in sodium (NaP) and potassium (KP) forms were used as adsorbents for the removal of calcium (Ca2+) and zinc (Zn2+) cations from aqueous solutions. Zeolite KP was prepared by ion exchange of K+ with Na+ which neutralizes the negative charge of the zeolite P framework structure. The ion exchange capacity of K+ on zeolite NaP was determined through the Freundlich isotherm equilibrium study. Characterization of zeolite KP was determined using infrared spectroscopy and X-ray diffraction (XRD) techniques. From the characterization, the structure of zeolite KP was found to remain stable after the ion exchange process. Zeolites KP and NaP were used for the removal of Ca and Zn from solution. The amount of Ca2+ and Zn2+ in aqueous solution before and after the adsorption by zeolites was analysed using the flame atomic absorption spectroscopy method. The removal of Ca2+ and Zn2+ followed the Freundlich isotherm rather than the Langmuir isotherm model. This result also revealed that zeolite KP adsorbs Ca2+ and Zn2+ more than zeolite NaP and proved that modification of zeolite NaP with potassium leads to an increase in the adsorption efficiency of the zeolite. Therefore, the zeolites NaP and KP can be used for water softening (Ca removal) and reducing water pollution/toxicity (Zn removal). PMID:20232677

Yusof, Alias Mohd; Malek, Nik Ahmad Nizam Nik; Kamaruzaman, Nurul Asyikin; Adil, Muhammad

2010-01-01

58

Zeolite-modified microcantilever gas sensor for indoor air quality control  

Microsoft Academic Search

To control indoor air quality, a novel freon gas sensor of piezoelectric microcantilever coated with zeolite has been developed in this paper. Excited by an ac voltage, the microcantilever is employed to detect the concentration of sample freon-12 gas ranged from 0 to 100ppm by the effect of the specific MFI zeolite modification. High selectivity and sensitivity combined with excellent

Jia Zhou; Po Li; Song Zhang; Yingcai Long; Feng Zhou; Yiping Huang; Pengyuan Yang; Minhang Bao

2003-01-01

59

Studies of anions sorption on natural zeolites.  

PubMed

This work presents results of FT-IR spectroscopic studies of anions-chromate, phosphate and arsenate - sorbed from aqueous solutions (different concentrations of anions) on zeolites. The sorption has been conducted on natural zeolites from different structural groups, i.e. chabazite, mordenite, ferrierite and clinoptilolite. The Na-forms of sorbents were exchanged with hexadecyltrimethylammonium cations (HDTMA(+)) and organo-zeolites were obtained. External cation exchange capacities (ECEC) of organo-zeolites were measured. Their values are 17mmol/100g for chabazite, 4mmol/100g for mordenite and ferrierite and 10mmol/100g for clinoptilolite. The used initial inputs of HDTMA correspond to 100% and 200% ECEC of the minerals. Organo-modificated sorbents were subsequently used for immobilization of mentioned anions. It was proven that aforementioned anions' sorption causes changes in IR spectra of the HDTMA-zeolites. These alterations are dependent on the kind of anions that were sorbed. In all cases, variations are due to bands corresponding to the characteristic Si-O(Si,Al) vibrations (occurring in alumino- and silicooxygen tetrahedra building spatial framework of zeolites). Alkylammonium surfactant vibrations have also been observed. Systematic changes in the spectra connected with the anion concentration in the initial solution have been revealed. The amounts of sorbed CrO4(2-), AsO4(3-) and PO4(3-) ions were calculated from the difference between their concentrations in solutions before (initial concentration) and after (equilibrium concentration) sorption experiments. Concentrations of anions were determined by spectrophotometric method. PMID:25002191

Barczyk, K; Mozgawa, W; Król, M

2014-12-10

60

Adsorption of Pb and Cd by amine-modified zeolite.  

PubMed

Natural zeolites, known for their excellent sorption properties towards metal cations, are widely used for the purification of wastewaters. The selectivity of clinoptilolite, a common zeolite mineral, for Pb is known to be particularly high, whereas its selectivity for Cd is often lower. Extraordinarily high sorption capacities for soft metal cations were observed in the case of thiol-functionalized silica gels and clays. In order to enhance the zeolites' sorption capacity for Cd, we treated natural heteroionic and Na-clinoptilolite in aqueous suspensions with cysteamine and propylamine solutions and investigated the sorption of Cd and Pb to amine-modified zeolite by a series of batch experiments. Stability constants for amine sorption on all zeolite samples at room temperature and 50 degrees C were obtained. Partial dimerization of cysteamine explains the enhanced sorption of this compound. In contrast, amine treatment did not enhance the adsorption capacity or selectivity of the clinoptilolite towards Cd and Pb. Instead, the amounts of adsorbed heavy metals decreased stoichometrically with increasing sorption of cysteamine and propylamine. This reduction can be explained by the blockage of channels by amine molecules and revealed that the modification of zeolites with mercaptoamines does not enhance the sorption capacity of zeolite for Cd and Pb. PMID:15996705

Wingenfelder, Ulla; Nowack, Bernd; Furrer, Gerhard; Schulin, Rainer

2005-09-01

61

Diagram of Zeolite Crystals  

NASA Technical Reports Server (NTRS)

The Center for Advanced Microgravity Materials Processing (CAMMP) in Cambridge, MA, a NASA-sponsored Commercial Space Center, is working to improve zeolite materials for storing hydrogen fuel. CAMMP is also applying zeolites to detergents, optical cables, gas and vapor detection for environmental monitoring and control, and chemical production techniques that significantly reduce by-products that are hazardous to the environment. Depicted here is one of the many here complex geometric shapes which make them highly absorbent. Zeolite experiments have also been conducted aboard the International Space Station

2003-01-01

62

Lithium modified zeolite synthesis for conversion of biodiesel-derived glycerol to polyglycerol  

NASA Astrophysics Data System (ADS)

Basic zeolite has received significant attention in the catalysis community. These zeolites modified with alkaline are the potential replacement for existing zeolite catalysts due to its unique features with added advantages. The present paper covers the preparation of lithium modified zeolite Y (Li-ZeY) and its activity for solvent free conversion of biodiesel-derived glycerol to polyglycerol via etherification process. The modified zeolite was well characterized by X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and Nitrogen Adsorption. The SEM images showed that there was no change in morphology of modified zeolite structure after lithium modification. XRD patterns showed that the structure of zeolite was sustained after lithium modification. The surface properties of parent and modified zeolite was also observed N2 adsortion-desorption technique and found some changes in surface area and pore size. In addition, the basic strength of prepared materials was measured by Hammet indicators and found that basic strength of Li-ZeY was highly improved. This modified zeolite was found highly thermal stable and active heterogamous basic catalyst for conversion of solvent free glycerol to polyglycerol. This reaction was conducted at different temperatures and 260 °C was found most active temperature for this process for reaction time from 6 to 12 h over this basic catalyst in the absence of solvent.

Ayoub, Muhammad; Abdullah, Ahmad Zuhairi; Inayat, Abrar

2014-10-01

63

Composite zeolite membranes  

DOEpatents

A new class of composite zeolite membranes and synthesis techniques therefor has been invented. These membranes are essentially defect-free, and exhibit large levels of transmembrane flux and of chemical and isotopic selectivity.

Nenoff, Tina M. (Albuquerque, NM); Thoma, Steven G. (Albuquerque, NM); Ashley, Carol S. (Albuquerque, NM); Reed, Scott T. (Albuquerque, NM)

2002-01-01

64

ZEOLITE CHARACTERIZATION TESTING  

SciTech Connect

The Savannah River Site isolates tritium from its process streams for eventual recycling. This is done by catalyzing the formation of tritiated water (from process streams) and then sorbing that water on a 3A zeolite (molsieve) bed. The tritium is recovered by regenerating the saturated bed into a Mg-based water cracking unit. The process described has been in use for about 15 years. Recently chloride stress corrosion cracking (SCC) was noted in the system piping. This has resulted in the need to replace the corroded piping and associated molecular sieve beds. The source of chlorine has been debated and one possible source is the zeolite itself. Since new materials are being purchased for recently fabricated beds, a more comprehensive analysis protocol for characterizing zeolite has been developed. Tests on archived samples indicate the potential for mobile chloride species to be generated in the zeolite beds.

Jacobs, W; Herbert Nigg, H

2007-09-13

65

Study of zeolite influence on analytical characteristics of urea biosensor based on ion-selective field-effect transistors  

PubMed Central

A possibility of the creation of potentiometric biosensor by adsorption of enzyme urease on zeolite was investigated. Several variants of zeolites (nano beta, calcinated nano beta, silicalite, and nano L) were chosen for experiments. The surface of pH-sensitive field-effect transistors was modified with particles of zeolites, and then the enzyme was adsorbed. As a control, we used the method of enzyme immobilization in glutaraldehyde vapour (without zeolites). It was shown that all used zeolites can serve as adsorbents (with different effectiveness). The biosensors obtained by urease adsorption on zeolites were characterized by good analytical parameters (signal reproducibility, linear range, detection limit and the minimal drift factor of a baseline). In this work, it was shown that modification of the surface of pH-sensitive field-effect transistors with zeolites can improve some characteristics of biosensors. PMID:24636423

2014-01-01

66

Sorption effects in zeolite catalysis  

SciTech Connect

Catalysis by zeolites and other microcrystalline materials is characterized by an unusually high degree of fundamental understanding. In acid catalysis, the active sites are part of the zeolite structure, not surface defects, and their nature and number can often be accurately determined. The dynamics of adsorption and desorption of reactant and product molecules, i.e. diffusion in zeolites, has also been extensively studied. Much less emphasis has been placed on a quantitative understanding of thermodynamic equilibrium sorption phenomena in zeolite catalyzed reactions. This talk will briefly discuss the principles and experimental data for hydrocarbon sorption in a variety of zeolites. It will then describe the application of these principles to a variety of zeolite catalyzed reactions. These include rate enhancements by non-acidic zeolites in thermal Diels-Alder reactions and paraffin cracking, the effect of carbon number and of zeolite structure on the observed activation energy of catalytic cracking, and the observation of very strong rate inhibition in ethylbenzene disproportionation.

Haag, W.O.

1996-10-01

67

Preparation of functionalized zeolitic frameworks  

DOEpatents

The disclosure provides zeolitic frameworks for gas separation, gas storage, catalysis and sensors. More particularly the disclosure provides zeolitic frameworks (ZIFs). The ZIF of the disclosure comprises any number of transition metals or a homogenous transition metal composition.

Yaghi, Omar M; Hayashi, Hideki; Banerjee, Rahul; Park, Kyo Sung; Wang, Bo; Cote, Adrien P

2012-11-20

68

Preparation of functionalized zeolitic frameworks  

DOEpatents

The disclosure provides zeolitic frameworks for gas separation, gas storage, catalysis and sensors. More particularly the disclosure provides zeolitic frameworks (ZIFs). The ZIF of the disclosure comprises any number of transition metals or a homogenous transition metal composition.

Yaghi, Omar M; Furukawa, Hiroyasu; Wang, Bo

2013-07-09

69

Zeolite crystal growth in space  

NASA Technical Reports Server (NTRS)

The growth of large, uniform zeolite crystals in high yield in space can have a major impact on the chemical process industry. Large zeolite crystals will be used to improve basic understanding of adsorption and catalytic mechanisms, and to make zeolite membranes. To grow large zeolites in microgravity, it is necessary to control the nucleation event and fluid motion, and to enhance nutrient transfer. Data is presented that suggests nucleation can be controlled using chemical compounds (e.g., Triethanolamine, for zeolite A), while not adversely effecting growth rate. A three-zone furnace has been designed to perform multiple syntheses concurrently. The operating range of the furnace is 295 K to 473 K. Teflon-lined autoclaves (10 ml liquid volume) have been designed to minimize contamination, reduce wall nucleation, and control mixing of pre-gel solutions on orbit. Zeolite synthesis experiments will be performed on USML-1 in 1992.

Sacco, Albert, Jr.; Thompson, Robert W.; Dixon, Anthony G.

1991-01-01

70

[Adsorption of phenol chemicals by surfactant-modified zeolites].  

PubMed

Two kinds of zeolites were prepared from fly ash and modified by surfactant subsequently. Surfactant-modified zeolites were studied for adsorption of phenol chemicals (phenol, p-chlorphenol, bisphenol A). It showed that the adsorption affinity of zeolite to phenol chemicals was significantly improved after surfactant modification. The adsorption isotherms of phenol chemicals were well fitted by the Langmuir isotherm. For the two surfactant-surfactant modified zeolites, the maximum adsorption amounts of phenol, p-chlorphenol, and bisphenol A calculated from the Langmuir equation were 37.7, 52.36, 90.9 mg x g(-1) and 10.7, 22.83, 56.8 mg x g(-1), respectively. When pH values of solutions were higher than the pK(a) values of phenol chemicals, the removal efficiencies were getting higher with the increase of pH values. The octanol/water partition coefficient (K(ow)) was also found to be an important factor affecting adsorption of phenol chemicals by the modified zeolites. Higher K(ow) value, which means the greater hydrophobicity of the chemicals, resulted in a higher removal. PMID:23379165

Xie, Jie; Wang, Zhe; Wu, De-Yi; Li, Chun-Jie

2012-12-01

71

Deposition of oriented zeolite A films: in situ and secondary growth  

Microsoft Academic Search

Zeolite A suspensions with a monomodal, narrow particle size distribution have been prepared. The suspended particles in a TMAOH water solution at pH 9 are negatively charged with a zeta potential of ?43mV. Modification of the external surface of the zeolite particles by a silylation reaction produces particles that, when they are suspended in water, are positively charged and have

Laura C Boudreau; Julia A Kuck; Michael Tsapatsis

1999-01-01

72

Effect of zeolite on toxicity of ammonia in freshwater sediments: Implications for toxicity identification evaluation procedures  

SciTech Connect

Techniques for reducing ammonia toxicity in freshwater sediments were investigated as part of a project to develop toxicity identification and evaluation (TIE) procedures for whole sediments. Although ammonia is a natural constituent of freshwater sediments, pollution can lead to ammonia concentrations that are toxic to benthic invertebrates, and ammonia can also contribute to the toxicity of sediments that contain more persistent contaminants. The authors investigated the use of amendments of a natural zeolite mineral, clinoptilolite, to reduce concentrations of ammonia in sediment pore water. Zeolites have been widely used for removal of ammonia in water treatment and in aqueous TIE procedures. The addition of granulated zeolite to ammonia-spiked sediments reduced pore-water ammonia concentrations and reduced ammonia toxicity to invertebrates. Amendments of 20% zeolite (v/v) reduced ammonia concentrations in pore water by {ge}70% in spiked sediments with ammonia concentrations typical of contaminated freshwater sediments. Zeolite amendments reduced toxicity of ammonia-spiked sediments to three taxa of benthic invertebrates (Hyalella azteca, Lumbriculus variegatus, and Chironomus tentans), despite their widely differing sensitivity to ammonia toxicity. In contrast, zeolite amendments did not reduce acute toxicity of sediments containing high concentrations of cadmium or copper or reduce concentrations of these metals in pore waters. These studies suggest that zeolite amendments, used in conjunction with toxicity tests with sensitive taxa such as H. azteca, may be an effective technique for selective reduction of ammonia toxicity in freshwater sediments.

Besser, J.M.; Ingersoll, C.G. [Geological Survey, Columbia, MO (United States); Leonard, E.N.; Mount, D.R. [Environmental Protection Agency, Duluth, MN (United States). Mid-Continent Ecology Div.

1998-11-01

73

Effect of zeolite on toxicity of ammonia in freshwater sediments: Implications for toxicity identification evaluation procedures  

USGS Publications Warehouse

Techniques for reducing ammonia toxicity in freshwater sediments were investigated as part of a project to develop toxicity identification and evaluation (TIE) procedures for whole sediments. Although ammonia is a natural constituent of freshwater sediments, pollution can lead to ammonia concentrations that are toxic to benthic invertebrates, and ammonia can also contribute to the toxicity of sediments that contain more persistent contaminants. We investigated the use of amendments of a natural zeolite mineral, clinoptilolite, to reduce concentrations of ammonia in sediment pore water. Zeolites have been widely used for removal of ammonia in water treatment and in aqueous TIE procedures. The addition of granulated zeolite to ammonia-spiked sediments reduced pore-water ammonia concentrations and reduced ammonia toxicity to invertebrates. Amendments of 20% zeolite (v/v) reduced ammonia concentrations in pore water by ???70% in spiked sediments with ammonia concentrations typical of contaminated freshwater sediments. Zeolite amendments reduced toxicity of ammonia-spiked sediments to three taxa of benthic invertebrates (Hyalella azteca, Lumbriculus variegatus, and Chironomus tentans), despite their widely differing sensitivity to ammonia toxicity. In contrast, zeolite amendments did not reduce acute toxicity of sediments containing high concentrations of cadmium or copper or reduce concentrations of these metals in pore waters. These studies suggest that zeolite amendments, used in conjunction with toxicity tests with sensitive taxa such as H. azteca, may be an effective technique for selective reduction of ammonia toxicity in freshwater sediments.

Besser, J.M.; Ingersoll, C.G.; Leonard, E.N.; Mount, D.R.

1998-01-01

74

Solid state radioluminescent sources using zeolites  

Microsoft Academic Search

Inorganic zeolites show promise as an alternative to traditional tritium gas tube light sources. Greater proximity of tritium atoms and luminescing centers, as well as greater tritium loading density, have been obtained within the zeolite aluminosilicate matrix. Zeolites are in addition optically clear and radiation stable. The zeolite radioluminescence program is described. Procedures for obtaining light sources are presented and

John T. Gill; Daniel B. Hawkins; Clifford L. Renschler

1990-01-01

75

Solid state radioluminescent sources using zeolites  

NASA Astrophysics Data System (ADS)

Inorganic zeolites show promise as an alternative to traditional tritium gas tube light sources. Greater proximity of tritium atoms and luminescing centers, as well as greater tritium loading density, have been obtained within the zeolite aluminosilicate matrix. Zeolites are in addition optically clear and radiation stable. The zeolite radioluminescence program is described. Procedures for obtaining light sources are presented and results are discussed.

Gill, John T.; Hawkins, Daniel B.; Renschler, Clifford L.

76

Oxygen and hydrogen isotope geochemistry of zeolites  

NASA Technical Reports Server (NTRS)

Oxygen and hydrogen isotope ratios for natural samples of the zeolites analcime, chabazite, clinoptilolite, laumontite, mordenite, and natrolite have been obtained. The zeolite samples were classified into sedimentary, hydrothermal, and igneous groups. The ratios for each species of zeolite are reported. The results are used to discuss the origin of channel water, the role of zeolites in water-rock interaction, and the possibility that a calibrated zeolite could be used as a low-temperature geothermometer.

Karlsson, Haraldur R.; Clayton, Robert N.

1990-01-01

77

The synthesis of zeolites from fly ash and the properties of the zeolite products  

Microsoft Academic Search

Fly ash produced during the combustion of powdered coal could be converted up to 45% into zeolite. By varying the experimental conditions different types of zeolite were produced, e.g. zeolite Na-P1, zeolite K-G and zeolite ZK19. By this zeolitization process the cation exchange capacity (CEC) was raised from 0.02 to circa 2.4 meq\\/g. Anionic heavy metals were largely extracted by

G Steenbruggen; G. G Hollman

1998-01-01

78

Utilizing copper(I) catalyzed azide-alkyne Huisgen 1,3-dipolar cycloaddition for the surface modification of colloidal particles with electroactive and emissive moieties  

NASA Astrophysics Data System (ADS)

The development of charge-transporting and fluorescing colloidal particles that can be directly printed into electroluminescent devices may result in a broad impact on the use of electrical energy for illumination. The objective of this work was to design and synthesize electroactive & fluorescing colloidal particles; establish their optical, electronic, and thermodynamic properties; and transition them into a device format for potential applications. The original intended application of this work was to build "better" colloidally-based organic light emitting devices (OLEDs) by creating functional particles with superior electrical and optical performance relative to commercially available technologies, but through the course of the research, the particles that were developed were found to be better suited for medical applications. Nonetheless, the global objective envisioned at the onset of this research was consistent with its final outcomes. The research tasks pursued to accomplish this global objective included: (1) The design and synthesis of electroactive moieties and their conversion into organic light emitting devices; An electron-transporting monomer was synthesized that was structurally & energetically similar to the small molecule 2-biphenyl-4-yl-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD). The monomer was copolymerized with 2-(9H-carbazol-9-yl)ethyl 2-methylacrylate (CE) and the resulting copolymer was utilized in OLEDs which employed fluorescent coumarin 6 (C6) or phosphorescent tris(2-phenylpyridine)iridium(III) [Ir(ppy)3] emitters. The copolymer devices exhibited a mean luminance of ca. 400 and 3,552 cd/m2 with the C6 and Ir(ppy)3 emitters, that were stable with thermal aging at temperatures ranging from 23°C to 130°C. Comparable poly(9-vinyl-9H-carbazole)/tBu-PBD blend devices exhibited more pronounced variations in performance with thermal aging. (2) The surface-modification of colloids with electroactive & fluorescing moieties via "click" chemistry; Aqueous-phase 83 nm poly(propargyl acrylate) (PA) nanoparticles were surface-functionalized with sparingly water soluble fluorescent moieties through a copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) (i.e., "click" transformation) to produce fluoroprobes with a large Stokes shift. For moieties which could not achieve extensive surface coverage on the particles utilizing a standard click transformation procedure, the presence of beta-cyclodextrin (beta-CD) during the transformation enhanced the grafting density onto the particles. For an oxadiazole containing molecule (AO), an azide-modified coumarin 6 (AD1) and a polyethylene glycol modified naphthalimide-based emitter (AD2), respectively, an 84%, 17% and 5% increase in the grafting densities were observed, when the transformation was performed in the presence of beta-CD. In contrast, a carbazolyl-containing moiety (AC) exhibited a slight retardation in the final grafting density when beta-CD was employed. Photoluminescence studies indicated that AC & AO when attached to the particles form an exciplex. An efficient energy transfer from the exciplex to the surface attached AD2 resulted in a total Stokes shift of 180 nm for the modified particles. (3) The synthesis and characterization of near-infrared (NIR) emitting particles for potential applications in cancer therapy. PA particles were surface modified through the "click" transformation of an azide-terminated indocyanine green (azICG), an NIR emitter, and poly(ethylene glycol) (azPEG) chains of various molecular weights. The placement of azICG onto the surface of the particles allowed for the chromophores to complex with bovine serum albumin (BSA) when dispersed in PBS that resulted in an enhancement of the dye emission. In addition, the inclusion of azPEG with the chromophores onto the particle surface resulted in a synergistic nine-fold enhancement of the fluorescence intensity, with azPEGs of increasing molecular weight amplifying the response. Preliminary photodynamic therapy (PDT)

Rungta, Parul

79

Properties and applications of zeolites.  

PubMed

Zeolites are aluminosilicate solids bearing a negatively charged honeycomb framework of micropores into which molecules may be adsorbed for environmental decontamination, and to catalyse chemical reactions. They are central to green-chemistry since the necessity for organic solvents is minimised. Proton-exchanged (H) zeolites are extensively employed in the petrochemical industry for cracking crude oil fractions into fuels and chemical feedstocks for other industrial processes. Due to their ability to perform cation-exchange, in which the cations that are originally present to counterbalance the framework negative charge may be exchanged out of the zeolite by cations present in aqueous solution, zeolites are useful as industrial water-softeners, in the removal of radioactive Cs+ and Sr2+ cations from liquid nuclear waste and in the removal of toxic heavy metal cations from groundwaters and run-off waters. Surfactant-modified zeolites (SMZ) find particular application in the co-removal of both toxic anions and organic pollutants. Toxic anions such as arsenite, arsenate, chromate, cyanide and radioactive iodide can also be removed by adsorption into zeolites that have been previously loaded with co-precipitating metal cations such as Ag+ and Pb2+ which form practically insoluble complexes that are contained within the zeolite matrix. PMID:21047018

Rhodes, Christopher J

2010-01-01

80

Enantioselective dehydration of butan-2-ol using zeolite Y modified with dithiane oxides  

SciTech Connect

Modification of zeolite H-Y by dithiane oxides (2-R-1,3-dithiane 1-oxide; R = H, CH{sub 3}, C{sub 6}H{sub 5}) is shown to enhance significantly its activity for the acid catalyzed gas phase dehydration of butan-2-ol. The rate enhancement is observed for catalysts that are prepared by adding the dithiane oxide to the zeolite synthesis gel or by adsorption of the dithiane oxide onto commercial samples of zeolite H-Y. The origin of the rate enhancement is considered to result from a specific interaction between the dithiane oxide modifier with both the extra-framework and framework aluminum in the zeolite. Modification of zeolite H-Y with (R)-1,3-dithiane 1-oxide enhances the conversion of (S)-butan-2-ol compared to (R)-butan-2-ol in the temperature range 110-150{degrees}C when the two enantiomers are reacted separately. Modification with (S)-2-phenyl-1,3-dithiane 1-oxide gives a catalyst for which (R)-butan-2-ol is the most reactive of the two enantiomers. Reaction of racemic butan-2-ol over these chirally modified H-Y zeolites demonstrates that this modification procedure makes the zeolite enantiomerically discriminating and one enantiomer preferentially reacts, although both are present in the micropores under the reaction conditions. This effect is considered to be due to enantioselective rate enhancement, since, although the rate of dehydration of both enantiomers is enhanced in the chiral environment, the dehydration rate of one enantiomer is accelerated relative to the other. It is suggested that the effect is due to preferential adsorption at the chiral active site. 34 refs., 7 figs., 6 tabs.

Feast, S.; Siddiqui, H.; Bethell, D. [Univ. of Liverpool (United Kingdom)] [and others] [Univ. of Liverpool (United Kingdom); and others

1997-04-15

81

Cell Biology of Copper  

Microsoft Academic Search

\\u000a The transition metal, copper (Cu), is an essential micronutrient for normal plant growth and development. Copper is a cofactor\\u000a of proteins involved in photosynthesis, respiration, ethylene perception, removal of superoxide radicals, and cell wall modification.\\u000a The biochemical reactions catalyzed by most Cu enzymes in plants are known. However, in many cases we are not yet sure about\\u000a the biological function

Christopher M. Cohu; Marinus Pilon

82

Thin layer of Ni-modified 13X zeolite on glassy carbon support as an electrode material in aqueous solutions  

Microsoft Academic Search

A new type of an electrode material, zeolite modified by the incorporation of Ni or NiO clusters into its cavities, was synthesized\\u000a by multiple impregnation of zeolite 13X with a Ni-acetylacetonate solution followed by solvent evaporation and thermal degradation\\u000a of the nickel compound. Samples with a Ni\\/13X mass ratio within the range 0.2–1.0 were synthesized. Modification by both Ni\\u000a and

Z. Mojovic; S. Mentus; I. Krsti?

2007-01-01

83

Mixing of zeolite powders and molten salt  

Microsoft Academic Search

Transuranics and fission products in a molten salt can be incorporated into zeolite A by an ion exchange process and by a batch mixing or blending process. The zeolite is then mixed with glass and consolidated into a monolithic waste form for geologic disposal. Both processes require mixing of zeolite powders with molten salt at elevated temperatures (>700 K). Complete

C. Pereira; V. N. Zyryanov; M. A. Lewis; J. P. Ackerman

1996-01-01

84

Thermal behaviour of a zeolitic tuff  

Microsoft Academic Search

Natural zeolites undergo structural changes after heating which open their possible use in different fields, related to their chemical and physical properties, such as building stone, lightweight aggregate, ceramic foam, concrete bricks, tiles, porcelain stoneware and additive in puzzolonic cements. In this study, thermal behavior of zeolitic tuff quarried from Gördes-Manisa, region of Turkey was investigated. Zeolitic rocks were first

Ö. Ça?lar Duvarc?; Y. Akdeniz; F. Özm?hç?; S. Ülkü; D. Balköse; M. Çiftçio?lu

2007-01-01

85

Copper Test  

MedlinePLUS

... 3. What happens if I am exposed to toxic amounts of copper? Copper poisoning can cause vomiting ... Asked Questions American Cancer Society: Copper Agency for Toxic Substances and Disease Registry: Public Health Statement for ...

86

Reclaiming silver from silver zeolite  

SciTech Connect

Silver zeolite is used to capture radioiodines from air cleaning systems in some nuclear facilities at the Idaho National Engineering Laboratory. It may become radioactively contaminated and/or poisoned by hydrocarbon vapors, which diminishes its capacity for iodine. Silver zeolite contains up to 38 wt% silver. A pyrometallurgical process was developed to reclaim the silver before disposing of the unserviceable zeolite as a radioactive waste. A flux was formulated to convert the refractory aluminosilicate zeolite structure into a low-melting fluid slag, with Na{sub 2}O added as NAOH instead of Na{sub 2}CO{sub 3} to avoid severe foaming due to CO{sub 2} evolution. A propane-fired furnace was built to smelt 45 kg charges at 1300C in a carbon-bonded silicon carbide crucible. A total of 218 kg (7000 tr oz) of silver was reclaimed from 1050 kg of unserviceable zeolite. Silver recoveries of 97% were achieved, and the radioisotopes were fixed as stable silicates in a vitreous slag that was disposed of as a low level waste. Recovered silver was refined using oxygen and cast into 100 tr oz bars assaying 99.8+% silver and showing no radioactive contamination.

Reimann, G.A.

1991-10-01

87

Reclaiming silver from silver zeolite  

SciTech Connect

Silver zeolite is used to capture radioiodines from air cleaning systems in some nuclear facilities at the Idaho National Engineering Laboratory. It may become radioactively contaminated and/or poisoned by hydrocarbon vapors, which diminishes its capacity for iodine. Silver zeolite contains up to 38 wt% silver. A pyrometallurgical process was developed to reclaim the silver before disposing of the unserviceable zeolite as a radioactive waste. A flux was formulated to convert the refractory aluminosilicate zeolite structure into a low-melting fluid slag, with Na[sub 2]O added as NAOH instead of Na[sub 2]CO[sub 3] to avoid severe foaming due to CO[sub 2] evolution. A propane-fired furnace was built to smelt 45 kg charges at 1300C in a carbon-bonded silicon carbide crucible. A total of 218 kg (7000 tr oz) of silver was reclaimed from 1050 kg of unserviceable zeolite. Silver recoveries of 97% were achieved, and the radioisotopes were fixed as stable silicates in a vitreous slag that was disposed of as a low level waste. Recovered silver was refined using oxygen and cast into 100 tr oz bars assaying 99.8+% silver and showing no radioactive contamination.

Reimann, G.A.

1991-10-01

88

Kinetics of heavy metal ions removal by use of natural zeolite.  

PubMed

Kinetics of the uptake of cadmium, lead, copper, nickel and zinc ions from single ion solutions and from their mixture by zeolitic rock has been studied. Removal of ions obeyed the kinetic equation for adsorption. Corresponding adsorption constants and distribution coefficients were determined for each metal ion uptake from single ion solution or mixture. An attempt was made to explain zeolite selectivity to different metal ions and the influence of water hardness on the uptake in terms of metal ionic radii and enthalpy of hydration. It was found that lead ions were strongly immobilized by the zeolite investigated, both from single ion and mixed solutions, as well as from soft and hard water. PMID:11846275

Panayotova, Marinela; Velikov, Borislav

2002-01-01

89

Liquid-phase benzene oxidation to phenol with molecular oxygen catalyzed by Cu-zeolites  

SciTech Connect

The oxidation of benzene to form phenol using cuprous chloride as a catalyst has been reported by Sasaki and his co-workers, who used reaction system oxygen molecules as the oxidant. Takehira and his co-workers have studied benzene oxidation with molecular oxygen catalyzed by Cu(II) salts in the presence of ascorbic acid. Cu ion-exchanged zeolites have been reported to be useful as catalysts for the gas-phase oxidation of some organic materials, and copper ions in zeolites have been indicated to have redox properties according to physicochemical measurements. Armed with this knowledge, the authors have tried the liquid-phase oxidation of benzene with molecular oxygen under atmospheric pressure at room temperature using Cu ion-exchanged zeolite catalysts in the presence of ascorbic acid as a reducing reagent for Cu ions. The catalytic behavior of the Cu zeolites for the benzene oxidation was compared with that of nonanchored cupric and cuprous chloride catalysts. Also, some Cu catalysts impregnated on some amorphous oxide supports, in addition to the zeolites, were tested as catalysts for benzene oxidation with molecular oxygen. 13 refs., 5 figs., 3 tabs.

Ohtani, Tsuyoshi; Nishiyama, Satoru; Tsuruya, Shigeru [Kobe Univ. (Japan)] [and others] [Kobe Univ. (Japan); and others

1995-08-01

90

Synthesis and testing of nanosized zeolite Y  

NASA Astrophysics Data System (ADS)

This work focuses on the synthesis and testing of nanosized zeolite Y. The synthesis formulations of faujasite-type structure of zeolite Y prepared in nanosized form are described. The synthetic zeolite Y is the most widely employed for the preparation of fluid catalytic cracking (FCC) catalysts. The synthesis of zeolite Y is very complicated process. The mean particle size of zeolite Y is 1800 nm. The major challenge of this work involved reducing this average particle size to less than 500 nm. The preliminary experiments were conducted to obtain the pure zeolite Y using the soluble silicates as a silica source. This was achieved by applying the experimental design approach to study the effects of many parameters. The ageing time turned out to be the most significant variable affecting product purity. Based on the preliminary results, a detailed investigation was carried out to determine the effects of silica-alumina precursor preparations on zeolite Y synthesis. Aluminosilicate precursors were prepared by gelling and precipitation of soluble silicate. The as-prepared precursors were used for the hydrothermal synthesis of zeolite Y. The procedure of the precipitation of soluble silicate yielded pure zeolite Y at the conventional synthesis conditions. The extent of purity of zeolite Y depends on the surface areas of aluminosilicate precursors. A novel approach to zeolite Y synthesis was employed for the preparation of the pure nanosized zeolite Y. This was achieved by applying the method of impregnation of precipitated silica. This novel method of impregnation for zeolite Y preparation allows eliminating the vigorous agitation step required for the preparation of a homogeneous silica solution, thereby simplifying the synthesis of zeolite Y in one single vessel. In case of the synthesis of nanosized zeolite Y, the effect of varying the organic templates on the formation of nanosized particles of zeolite Y was investigated, while all other reaction parameters were kept constant. The extent to which the nanosized zeolite Y was formed depended on the types and amount of the organic templates as well as the ageing duration. The activity testing of four FCC catalysts prepared by using CREY (Calcined Rare Earth ion-exchanged) zeolites with different particle sizes was carried out in a fluidized bench-scale batch riser simulator reactor. The starting zeolites NaY of different particle sizes were subjected to two cycles of ion exchange treatment. The particle size of the supported zeolites was varied between 150 and 1800 nm. The preparation of FCC catalysts was conducted by mixing the CREY zeolite with silica-alumina matrix and silica sol binder. Each catalyst contained 25% zeolite. The results of catalytic cracking demonstrated the significant effect of size reduction of the starting zeolite Y on catalytic performance of FCC catalyst. Keywords. Zeolite NaY, Faujasite, Nanosized particles, Nanozeolite, Nanotechnology, Synthesis, Crystallization, Seeding, Ageing, Precipitated silica, Sylopol silica, Fumed silica, Silica sol, Soluble silicates, Alumina, SAR or SiO2/Al2O3 Ratios, Sodium hydroxide, Sodium aluminate, Organic templates, TMAOH, Surfactant (CTAB), Ammonium Sulfate, BET surface area, BJH Pore Size Distribution, Zetasizer Particle Size Distribution, Powder XRD, 27Al Solid-State NMR, Catalytic Impregnation, CREY Zeolite, Silica-Alumina Matrix, Ion Exchange, FCC Catalyst, Catalytic cracking, Riser SimulatorRTM, Steaming, Zeolite HY, Utrastable Zeolite Y (USY)

Karami, Davood

91

Modifications on the hydrogen bond network by mutations of Escherichia coli copper efflux oxidase affect the process of proton transfer to dioxygen leading to alterations of enzymatic activities  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Proton transfer pathway to dioxygen in CueO was identified. Black-Right-Pointing-Pointer Glu506 is the key amino acid to transport proton. Black-Right-Pointing-Pointer The Ala mutation at Glu506 formed a compensatory proton transfer pathway. Black-Right-Pointing-Pointer The Ile mutation at Glu506 shut down the hydrogen bond network. -- Abstract: CueO has a branched hydrogen bond network leading from the exterior of the protein molecule to the trinuclear copper center. This network transports protons in the four-electron reduction of dioxygen. We replaced the acidic Glu506 and Asp507 residues with the charged and uncharged amino acid residues. Peculiar changes in the enzyme activity of the mutants relative to the native enzyme indicate that an acidic amino acid residue at position 506 is essential for effective proton transport. The Ala mutation resulted in the formation of a compensatory hydrogen bond network with one or two extra water molecules. On the other hand, the Ile mutation resulted in the complete shutdown of the hydrogen bond network leading to loss of enzymatic activities of CueO. In contrast, the hydrogen bond network without the proton transport function was constructed by the Gln mutation. These results exerted on the hydrogen bond network in CueO are discussed in comparison with proton transfers in cytochrome oxidase.

Kajikawa, Takao; Kataoka, Kunishige [Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa 920-1192 (Japan)] [Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa 920-1192 (Japan); Sakurai, Takeshi, E-mail: tsakurai@se.kanazawa-u.ac.jp [Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa 920-1192 (Japan)] [Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa 920-1192 (Japan)

2012-05-25

92

UTILITY OF ZEOLITES IN HAZARDOUS METAL REMOVAL FROM WATER  

EPA Science Inventory

Zeolites are well known for their ion exchange, adsorption and acid catalysis properties. Different inorganic pollutants have been removed from water at room temperature by using synthetic zeolites. Zeolite Faujasite Y has been used to remove inorganic pollutants including arseni...

93

The influence of using Jordanian natural zeolite on the adsorption, physical, and mechanical properties of geopolymers products.  

PubMed

Geopolymers consist of an amorphous, three-dimensional structure resulting from the polymerization of aluminosilicate monomers that result from dissolution of kaolin in an alkaline solution at temperatures around 80 degrees C. One potential use of geopolymers is as Portland cement replacement. It will be of great importance to provide a geopolymer with suitable mechanical properties for the purpose of water storage and high adsorption capacity towards pollutants. The aim of this work is to investigate the effect of using Jordanian zeolitic tuff as filler on the mechanical performance and on the adsorption capacity of the geopolymers products. Jordanian zeolitic tuff is inexpensive and is known to have high adsorption capacity. The results confirmed that this natural zeolitic tuff can be used as a filler of stable geopolymers with high mechanical properties and high adsorption capacity towards methylene blue and Cu(II) ions. The XRD measurements showed that the phillipsite peaks (major mineral constituent of Jordanian zeolite) were disappeared upon geopolymerization. The zeolite-based geopolymers revealed high compressive strength compared to reference geopolymers that employ sand as filler. Adsorption experiments showed that among different geopolymers prepared, the zeolite-based geopolymers have the highest adsorption capacity towards methylene blue and copper(II) ions. PMID:19036505

Yousef, Rushdi Ibrahim; El-Eswed, Bassam; Alshaaer, Mazen; Khalili, Fawwaz; Khoury, Hani

2009-06-15

94

Three Mile Island zeolite vitrification demonstration program  

Microsoft Academic Search

This paper presents a brief overview of the Three Mile Island (TMI) zeolite vitrification program. The formulation of a glass suitable for immobilizing submerged demineralizer system (SDS) zeolites is discussed. A feed system that was developed to feed zeolites to the in-can melter is described. The in-can melting process and the government-owned facilities in which the demonstrations will take place

D. H. Siemens; D. E. Knowlton; M. W. Shupe

1982-01-01

95

Increased thermal conductivity monolithic zeolite structures  

DOEpatents

A monolith comprises a zeolite, a thermally conductive carbon, and a binder. The zeolite is included in the form of beads, pellets, powders and mixtures thereof. The thermally conductive carbon can be carbon nano-fibers, diamond or graphite which provide thermal conductivities in excess of about 100 W/mK to more than 1,000 W/mK. A method of preparing a zeolite monolith includes the steps of mixing a zeolite dispersion in an aqueous colloidal silica binder with a dispersion of carbon nano-fibers in water followed by dehydration and curing of the binder is given.

Klett, James (Knoxville, TN); Klett, Lynn (Knoxville, TN); Kaufman, Jonathan (Leonardtown, MD)

2008-11-25

96

Surfactant-modified zeolite as a slow release fertilizer for phosphorus.  

PubMed

The feasibility of using surfactant-modified zeolite (SMZ) as a carrier for fertilizer and for slow release of phosphorus (P) was investigated. Zeolite-A was modified by using hexadecyltrimethylammonium bromide, a cationic surfactant, to modify its surface to increase its capacity to retain anion, namely, phosphate (PO4(3-)). SMZ was thoroughly characterized using X-ray diffraction, Fourier transform infrared, and scanning electron microscopy to study the effect of surfactant modification. Zeolite-A and SMZ were then subjected to P loading by treating them with fertilizer (KH2PO4). It was observed that the P loading on SMZ increased by a factor of 4.9 as compared to the unmodified zeolite-A. A comparative study of the release of P from fertilizer-loaded unmodified zeolite-A and SMZ and from solid KH2PO4 was performed using the constant flow percolation reactor. The results show that the P supply from fertilizer-loaded SMZ was available even after 1080 h of continuous percolation, whereas P from KH2PO4 was exhausted within 264 h. The results indicate that SMZ is a good sorbent for PO4(3-), and a slow release of P was achievable. These properties suggest that SMZ has a great potential as the fertilizer carrier for slow release of P. PMID:16787027

Bansiwal, Amit Kumar; Rayalu, Sadhana Suresh; Labhasetwar, Nitin Kumar; Juwarkar, Asha Ashok; Devotta, Sukumar

2006-06-28

97

Copper deficiency myelopathy.  

PubMed

Acquired copper deficiency has been recognised as a rare cause of anaemia and neutropenia for over half a century. Copper deficiency myelopathy (CDM) was only described within the last decade, and represents a treatable cause of non-compressive myelopathy which closely mimics subacute combined degeneration due to vitamin B12 deficiency. Here, 55 case reports from the literature are reviewed regarding their demographics, aetiology, haematological and biochemical parameters, spinal imaging, treatment and outcome. The pathophysiology of disorders of copper metabolism is discussed. CDM most frequently presented in the fifth and sixth decades and was more common in women (F:M = 3.6:1). Risk factors included previous upper gastrointestinal surgery, zinc overload and malabsorption syndromes, all of which impair copper absorption in the upper gastrointestinal tract. No aetiology was established in 20% of cases. High zinc levels were detected in some cases not considered to have primary zinc overload, and in this situation the contribution of zinc to the copper deficiency state remained unclear. Cytopenias were found in 78%, particularly anaemia, and a myelodysplastic syndrome may have been falsely diagnosed in the past. Spinal MRI was abnormal in 47% and usually showed high T2 signal in the posterior cervical and thoracic cord. In a clinically compatible case, CDM may be suggested by the presence of one or more risk factors and/or cytopenias. Low serum copper and caeruloplasmin levels confirmed the diagnosis and, in contrast to Wilson's disease, urinary copper levels were typically low. Treatment comprised copper supplementation and modification of any risk factors, and led to haematological normalisation and neurological improvement or stabilisation. Since any neurological recovery was partial and case numbers of CDM will continue to rise with the growing use of bariatric gastrointestinal surgery, clinical vigilance will remain the key to minimising neurological sequelae. Recommendations for treatment and prevention are made. PMID:20232210

Jaiser, Stephan R; Winston, Gavin P

2010-06-01

98

Zeolites Remove Sulfur From Fuels  

NASA Technical Reports Server (NTRS)

Zeolites remove substantial amounts of sulfur compounds from diesel fuel under relatively mild conditions - atmospheric pressure below 300 degrees C. Extracts up to 60 percent of sulfur content of high-sulfur fuel. Applicable to petroleum refineries, natural-gas processors, electric powerplants, and chemical-processing plants. Method simpler and uses considerably lower pressure than current industrial method, hydro-desulfurization. Yields cleaner emissions from combustion of petroleum fuels, and protects catalysts from poisoning by sulfur.

Voecks, Gerald E.; Sharma, Pramod K.

1991-01-01

99

Factors affecting adsorption characteristics of Zn2+ on two natural zeolites.  

PubMed

Mining-related and industrial wastes are primary sources of heavy metal contamination in soils and groundwater. The limitation of such waste in drinking water needs to meet government requirements in order to safeguard human health and environment. Zinc, one of the most preponderant pollutants, is difficult to remove from wastewater rather than other heavy metals (i.e. lead, copper and cadmium). This paper investigates Zn2+ adsorption characteristics of two natural zeolites found in the regions of Gordes and Bigadic, in western Turkey. The results show that the Zn2+ adsorption behavior of both zeolites is highly dependent on the pH. Adsorption dependence on lower pH values (pH<4) is explained by the dissolution of crystal structure and the competition of the zinc ions with the H+. Between pH 4 and 6, the basic mechanism is the ion exchange process. The results also showed that decrease in grain size does not increase the adsorption capacity of zeolite from Gordes, yet it increases that of zeolite from Bigadic about 23%. The results also reveal that an increase in the initial concentration of Zn2+ in the system causes an increase in the adsorption capacity to a degree, then it becomes more constant at higher concentrations. With this, the removal efficiency of Gordes zeolite is two times higher than that of Bigadic zeolite. Results show that an increase in slurry concentration results in a lower uptake of Zn2+. In the final part of the paper, we compared the experimental data with the Langmuir and Freundlich isotherms. The results show that there is a good fit between the experimental data and empirical isotherms. PMID:16266781

Oren, Ali Hakan; Kaya, Abidin

2006-04-17

100

Synthesis and immobilization of quaternary ammonium cations in acidic zeolites  

Microsoft Academic Search

A general method for the synthesis of quaternary ammo- nium cations in acidic zeolites by a direct reaction of tertiary amines and alcohols is described. Zeolites and zeolite-related porous solids are ideal inorganic hosts for accommodating a large variety of guest species. 1 Bulky carbon-centered ionic intermediates, such as triar- ylmethyl cations, can be encapsulated within zeolite supercages via a

Wei Wang; Andreas Buchholz; Irina I. Ivanova; Jens Weitkampa; Michael Hunger

2003-01-01

101

The potential application of natural zeolite for greywater treatment  

Microsoft Academic Search

Natural zeolites are good potential material for water and wastewater treatment. It is due to the advantages of low cost, ion-exchange and adsorption capability of the natural zeolites. It can also be modified and regenerated. This paper thus looks at efforts made in exploring the potential application of natural zeolites and modified natural zeolites in water and wastewater treatment especially

Nurul Widiastuti; Hongwei Wu; Ming Ang; Dong-ke Zhang

2008-01-01

102

Solid state radioluminescent sources using tritium-loaded zeolites  

Microsoft Academic Search

Zeolite-based tritium lamps are a possible alternative to traditional tritium gas tube light sources. Rare earth luminescing centers may be ion-exchanged into zeolite matrices. Close proximity of tritium atoms to the rare earths can be provided by highly tritiated water sorbed within the pore structure of the zeolite aluminosilicate matrix. Zeolites are optically clear and radiation stable. Light outputs from

J. T. Gill; D. B. Hawkins; C. L. Renschler

1991-01-01

103

Synthesis of MFI zeolite membranes for water desalination  

Microsoft Academic Search

Zeolite membranes have been extensively researched for many industrial separations via gas permeation and liquid pervaporation processes. General separation mechanisms in zeolite membranes include molecular sieving and competitive adsorption and diffusion. Recently, the possibility of using zeolite membranes to remove ions from aqueous solutions by reverse osmosis (RO) has been explored. RO desalination by zeolite membranes may offer an alternative

Mansoor Kazemimoghadam; Toraj Mohammadi

2007-01-01

104

UTILITY OF ZEOLITES IN ARSENIC REMOVAL FROM WATER  

EPA Science Inventory

Zeolites are well known for their ion exchange and adsorption properties. So far the cation exchanger properties of zeolites have been extensively studied and utilized. The anion exchanger properties of zeolites are less studied. Zeolite Faujasite Y has been used to remove arseni...

105

Zeolitic materials with hierarchical porous structures.  

PubMed

During the past several years, different kinds of hierarchical structured zeolitic materials have been synthesized due to their highly attractive properties, such as superior mass/heat transfer characteristics, lower restriction of the diffusion of reactants in the mesopores, and low pressure drop. Our contribution provides general information regarding types and preparation methods of hierarchical zeolitic materials and their relative advantages and disadvantages. Thereafter, recent advances in the preparation and characterization of hierarchical zeolitic structures within the crystallites by post-synthetic treatment methods, such as dealumination or desilication; and structured devices by in situ and ex situ zeolite coatings on open-cellular ceramic foams as (non-reactive as well as reactive) supports are highlighted. Specific advantages of using hierarchical zeolitic catalysts/structures in selected catalytic reactions, such as benzene to phenol (BTOP) and methanol to olefins (MTO) are presented. PMID:21495091

Lopez-Orozco, Sofia; Inayat, Amer; Schwab, Andreas; Selvam, Thangaraj; Schwieger, Wilhelm

2011-06-17

106

Salt-thermal zeolitization of fly ash.  

PubMed

The molten-salt method has been recently proposed as a new approach to zeolitization of fly ash. Unlike the hydrothermal method, this method employs salt mixtures as the reaction medium without any addition of water. In this study, systematic investigation has been conducted on zeolitization of fly ash in a NaOH-NaNO3 system in order to elucidate the mechanism of zeolite formation and to achieve its optimization. Zeolitization of fly ash was conducted by thermally treating a powder mixture of fly ash, NaOH, and NaNO3. Zeolitization of fly ash took place above 200 degrees C, a temperature lower than the melting points of salt and base in the NaOH-NaNO3 system. However, it was uncertain whether the reactions took place in a local molten state or in a solid state. Therefore, the proposed method is renamed the "salt-thermal" method rather than the "molten-salt" method. Mainly because of difficulty in mobility of components in salt mixtures, zeolitization seems to occur within a local reaction system. In situ rearrangement of activated components seems to lead to zeolite formation. Particle growth, rather than crystal growth through agglomeration, resulted in no distinct morphologies of zeolite phases. Following are the optimal zeolitization conditions of the salt-thermal method: temperature, 250-350 degrees C; time, 3-12 h; weight ratio of NaOH/NaNO3, 0.3-0.5; weight ratio of NaNO3/fly ash, 0.7-1.4. Therefore, it is clear from this work that the salt-thermal method could be applied to massive zeolitization of fly ash as a new alternative method for recycling this waste. PMID:11452614

Choi, C L; Park, M; Lee, D H; Kim, I E; Park, B Y; Choi, J

2001-07-01

107

Energy and materials flows in the copper industry  

SciTech Connect

The copper industry comprises both the primary copper industry, which produces 99.9%-pure copper from copper ore, and the secondary copper industry, which salvages and recycles copper-containing scrap metal to extract pure copper or copper alloys. The United States uses about 2 million tons of copper annually, 60% of it for electrical applications. Demand is expected to increase less than 4% annually for the next 20 years. The primary copper industry is concentrated in the Southwest; Arizona produced 66% of the 1979 total ore output. Primary production uses about 170 x 10/sup 12/ Btu total energy annually (about 100 x 10/sup 6/ Btu/ton pure copper produced from ore). Mining and milling use about 60% of the total consumption, because low-grade ore (0.6% copper) is now being mined. Most copper is extracted by smelting sulfide ores, with concomitant production of sulfur dioxide. Clean air regulations will require smelters to reduce sulfur emissions, necessitating smelting process modifications that could also save 20 x 10/sup 12/ Btu (10 x 10/sup 6/ Btu/ton of copper) in smelting energy. Energy use in secondary copper production averages 20 x 10/sup 6/ Btu/ton of copper. If all copper products were recycled, instead of the 30% now salvaged, the energy conservation potential would be about one-half the total energy consumption of the primary copper industry.

Gaines, L.L.

1980-12-01

108

Evaluation of zeolite-sand mixtures as reactive materials protecting groundwater at waste disposal sites.  

PubMed

To recognize properties of a mixture of Vistula sand (medium sand acc. to USCS) with Slovak zeolite as reactive materials suitable for permeable reactive barriers proposed for protection of groundwater environment in vicinity of old landfills comprehensive laboratory investigations were performed. The present study investigates the removal of contaminants specific for landfill leachates onto zeolite-sand mixtures containing 20%, 50% and 80% of zeolite (ZS20, ZS50 and ZS80). Taking into account the results of batch tests it was concluded that the Langmuir isotherm best fitted the data. It was observed that the presence of ammonium, calcium and magnesium decreases the removal efficiency of copper by 32%. Column tests of contaminant migration through the attenuation zone of the reactive materials were interpreted using the software package CXTFIT, which solves a one-dimensional advection-dispersion equation. Column test results also indicate the strong influence of the presence of interfering substances on copper immobilisation; dynamic sorption capacities decrees twofold. Throughout the landfill leachate flow through ZS80 sample, a constant reduction of NH4+ (at 100%), K+ (at 93%) and Fe(total) (at an average of 86%) were observed. There was no reduction in chemical oxygen demand and biochemical oxygen demand. PMID:24520718

Joanna, Fronczyk; Kazimierz, Garbulewski

2013-09-01

109

Zeolites and Intrazeolite Chemistry: Insights from Infrared Spectroscopy  

Microsoft Academic Search

Zeolites are widely used as adsorbents, catalysts, ion exchangers and molecular sieves. However, less is known about the potential use of zeolites and related microporous solids for tailored synthesis of advanced materials. Zeolite-based host-guest nanocomposites are a type of advanced material in which zeolites act as hosts for encapsulating and organizing molecules, crystalline nano-phases and supramolecular entities inside the zeolite

C. Otero Areán

2000-01-01

110

Copper-exchanged mordenites as active catalysts for NO selective catalytic reduction by propene under oxidising conditions: Effect of Si\\/Al ratio, copper content and Brönsted acidity  

Microsoft Academic Search

CuMOR catalysts with different Si\\/Al ratios and copper contents, prepared from the acid and sodium forms, were studied in NO reduction with propene in the presence of excess oxygen. It was observed that the influence of zeolite Si\\/Al ratio on CuMOR catalytic activity for NO SCR by propene depends on the catalyst copper content, the reverse being also true. For

C. Torre-Abreu; M. F. Ribeiro; C. Henriques; F. R. Ribeiro

1997-01-01

111

Zeolites: Can they be synthesized by design  

SciTech Connect

Zeolites and zeolite-like molecular sieves are crystalline oxides that have high surface-to-volume ratios and are able to recognize, discriminate, and organize molecules with differences of < 1 [angstrom]. The close connection between the atomic structure and macroscopic properties of these materials has led to uses in molecular recognition. For example, zeolites and zeolite-like molecular sieves can reveal marvelous molecular recognition specificity and sensitivity that can be applied to catalysis, separations technology, and chemical sensing. Additionally, they can serve as hosts to organize guest atoms and molecules that endow composite materials with optoelectric and electrochemical properties. Because of the high level of structural control necessary to create high-performance materials with zeolites or zeolite-like molecular sieves, the design and synthesis of these solids with specific architectures and properties are highly desired. Although this lofty goal is still elusive, advances have been made to allow the serious consideration of designing molecular sieves. Here, the author covers two aspects of this ongoing effort. First, he discusses the feasibility of designing pore architectures through the use of organic structure-directing agents. Second, he explores the possibility of creating zeolites through ''Lego chemistry.''

Davis, M.E. (California Inst. of Technology, Pasadena, CA (United States))

1994-09-01

112

Zeolites on Mars: Prospects for Remote Sensing  

NASA Technical Reports Server (NTRS)

The Martian surface composition measured by Viking can be represented by several combinations of minerals incorporating major fractions of zeolites known to occur in altered mafic rocks and polar soils on Earth. The abundant occurrence of zeolites on Mars is consistent with what is known about both the physical and chemical environment of that planet. The laboratory reflectance spectra (0.65 to 2.55 microns) of a number of relatively pure zeolite minerals and some naturally occurring zeolite-clay soils were measured. All of the spectra measured are dominated by strong absorption near 1.4 and 1.9 microns and a steep reflectance drop longward of about 2.2 microns, all of which are due to abundant H2O. Weaker water overtone bands are also apparent, and in most cases there is spectral evidence for minor Fe(3+). In these features the zeolite spectra are similar to spectra of smectite clays which have abundant interlayer water. The most diagnostic difference between clay and zeolite spectra is the total absence in the zeolites of the weak structural OH absorption.

Gaffney, E. S.; Singer, R. B.; Kunkle, T. D.

1985-01-01

113

Interaction between zeolites and cluster compounds. Part 1.?Adsorption of iron pentacarbonyl on zeolites  

Microsoft Academic Search

Received 1 1 th November, 1982 The adsorption isotherms of Fe(CO), on Nay, HY and Linde L zeolites obtained in McBain balances show micropore adsorption, whereas additional capillary condensation is found with zeolite omega and Na-mordenite. The pores and\\/or cages of the zeolites studied are completely filled with the complex upon saturation, with the exception of Na-mordenite. Their behaviour is

Thomas Bein; Peter A. Jacobs

1983-01-01

114

Dispersion strengthened copper  

DOEpatents

A composition of matter comprised of copper and particles which are dispersed throughout the copper, where the particles are comprised of copper oxide and copper having a coating of copper oxide, and a method for making this composition of matter.

Sheinberg, Haskell (Los Alamos, NM); Meek, Thomas T. (Knoxville, TN); Blake, Rodger D. (Santa Fe, NM)

1990-01-01

115

Dispersion strengthened copper  

DOEpatents

A composition of matter comprised of copper and particles which are dispersed throughout the copper, where the particles are comprised of copper oxide and copper having a coating of copper oxide, and a method for making this composition of matter.

Sheinberg, Haskell (Los Alamos, NM); Meek, Thomas T. (Knoxville, TN); Blake, Rodger D. (Santa Fe, NM)

1989-01-01

116

Characterizing the dealumination of environmentally relevant zeolites using IR, NMR and neutron diffraction techniques  

SciTech Connect

Results of characterization studies monitoring the sequential chemical bond breaking events, local site symmetry, and long range structural modifications of specific zeolites (H-ZSM-5, TS-1) during hydrothermal treatment of these catalyst materials are described. These characterization techniques include infrared spectroscopy of selected probe molecules, magic angle spinning NMR spectroscopy, and powder neutron diffraction. Information regarding selected examples from each of these techniques is presented and the inherent strengths of each is discussed. The experimental insight into the chemical and structural modifications of high surface area microporous catalyst materials as a function of deactivation conditions (hydrothermal conditioning) is highlighted.

Paffett, M.T.; Szanyi, J.; Jacubinas, R.M.; Ott, K.C.; VonDreele, R.; Hughes, C.D.; Earl, W.L.

1997-07-01

117

Mixing of zeolite powders and molten salt  

SciTech Connect

Transuranics and fission products in a molten salt can be incorporated into zeolite A by an ion exchange process and by a batch mixing or blending process. The zeolite is then mixed with glass and consolidated into a monolithic waste form for geologic disposal. Both processes require mixing of zeolite powders with molten salt at elevated temperatures (>700 K). Complete occlusion of salt and a uniform distribution of chloride and fission products are desired for incorporation of the powders into the final waste form. The relative effectiveness of the blending process was studied over a series of temperature, time, and composition profiles. The major criteria for determining the effectiveness of the mixing operations were the level and uniformity of residual free salt in the mixtures. High operating temperatures (>775 K) improved salt occlusion. Reducing the chloride levels in the mixture to below 80% of the full salt capacity of the zeolite significantly reduced the free salt level in the final product.

Pereira, C.; Zyryanov, V.N.; Lewis, M.A.; Ackerman, J.P.

1996-05-01

118

Dehydrated Lanthanum-exchanged Type Y Zeolite  

Microsoft Academic Search

Lanthanum atoms occupy different sites in the crystal structure of dehydrated type Y zeolite as the temperature changes, probably because of the absence of residual molecules for bonding at 725° C compared with their presence at lower temperatures.

J. V. Smith; J. M. Bennett; E. M. FLANIGEN

1967-01-01

119

Factors affecting the MTW zeolite cristallization process  

SciTech Connect

The synthesis mechanism of the high silica zeolite types other than MFI is rarely studied in the open literature. This work is devoted to the role of different parameters governing the zeolite MTW crystallization process. The influence of the most important factors: the nature of the silica and alumina source, the type of the organic cation, the alkalinity of the reaction mixture and the crystallization temperature, was studied. The molar composition of the initial hydrogel was varied in other to determine the crystallization field of the zeolite MTW. The observed morphology and particle size of the crystallites are related to the corresponding reaction conditions. The competitive formation of the other zeolite types (prevalently MFI and BEA) is discussed.

Katovic, A.; Giordano, G. [Universita della Calabria, Rende (Italy)

1995-12-01

120

Solid state radioluminescent sources using tritium-loaded zeolites  

NASA Astrophysics Data System (ADS)

Zeolite-based tritium lamps are a possible alternative to traditional tritium gas tube light sources. Rare earth luminescing centers may be ion-exchanged into zeolite matrices. Close proximity of tritium atoms to the rare earths can be provided by highly tritiated water sorbed within the pore structure of the zeolite aluminosilicate matrix. Zeolites are optically clear and radiation stable. Light outputs from tritium-loaded zeolites are shown here to exceed 2 micro-W/sq cm, with good stability. Procedures for obtaining light sources are presented and results are discussed. The possible use of these luminescent materials as process monitors for zeolite absorption columns in tritium service is also discussed.

Gill, J. T.; Hawkins, D. B.; Renschler, C. L.

121

Zeolite based catalysts for hydrodenitrogenation of quinoline  

E-print Network

ZEOLITE BASED CATALYSTS FOR HYDRODENITROGENATION OF QUINOLINE A Thesis by BHAVYEN SUNAN SANGHVI submitted to the Graduate College of Texas A 6 N University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE... December 1982 Najor Subject:Chemical Engineering ZEOLITE BASED CATALYSTS FOR HYDRODENITROGENATION OF QUINOLINE A Thesis by BHAVYEN SUNAN SANGHVI Approved as to style and content by: (Chairman of ommittee) (member) (member) yg-, , rn- !' (member...

Sanghvi, Bhavyen Suman

2012-06-07

122

Metal loading and reactivity of Zeolite Y  

E-print Network

METAL LOADING AND REACTIVITY OF ZEOLITE Y A Thesis by MARC GERARD SAENZ Submitted to the Graduate College of Texas ARM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE August 1988 Major Subject...: Chemical Engineering METAL LOADING AND REACTIVITY OF ZEOLITE Y A Thesis by MARC GERARD SAENZ Approved as to style and content by: ydin Akgerma (Chairman of Co ttee) Da id L. Cocke (Member) Ahmed M. Gadalla (Member ) Raymond W. Plumer elt (Head...

Sa?enz, Marc Gerard

2012-06-07

123

Adsorption Behavior of Chlorophenols on Natural Zeolite  

Microsoft Academic Search

The adsorption of aqueous organic pollutants, i.e., phenol, monochlorophenols (2?and 4?), and dichlorophenols (2,4?and 3,5?) on natural Jordanian zeolitic tuff was studied. Three simplified kinetic models, viz., pseudo?first order, pseudo?second order, and intraparticle diffusion models were used to fit the kinetics data. The results revealed that at earlier stages of adsorption of phenols onto zeolite, the pseudo?second order and the

Rushdi I. Yousef

2007-01-01

124

Three Mile Island zeolite vitirification demonstration program  

SciTech Connect

The cleanup of the high-activity-level water at Three Mile Island (TMI) provides an opportunity to further develop waste management technology. Approximately 790,000 gallons of high-activity-level water at TMI's Unit-2 Nuclear Power Station will be decontaminated at the site using the submerged demineralizer system (SDS). In the SDS process, the cesium and strontium in the water are sorbed onto zeolite that is contained within metal liners. The Department of Energy has asked the Pacific Northwest Laboratory (PNL) to take a portion of the zeolite from the SDS process and demonstrate, on a production scale, that this zeolite can be vitrified using the in-can melting process. This paper is a brief overview of the TMI zeolite vitrification program. The first section discusses the formulation of a glass suitable for immobilizing SDS zeolite. The following section describes a feed system that was developed to feed zeolite to the in-can melter. It also describes the in-can melting process and the government owned facilities in which the demonstrations will take place. Finally, the schedule for completing the program activities is outlined.

Siemens, D.H.; Knowlton, D.E.; Shupe, M.W.

1981-06-01

125

Properties of glass-bonded zeolite monoliths  

SciTech Connect

It has been shown that mineral waste forms can be used to immobilize waste salt generated during the pyrochemical processing of spent fuel from the Integral Fast Reactor (IFR). Solid, leach resistant monoliths were formed by hot-pressing mixtures of salt-occluded zeolite A powders and glass frit at 990 K and 28 MPa. Additional samples have now been fabricated and tested. Normalized release rates for all elements, including iodide and chloride, were less than 1 g/m{sup 2}d in 28-day tests in deionized water and in brine at 363 K (90{degrees}C). Preliminary results indicate that these rates fall with time with both leachants and that the zeolite phase in the glass-bonded zeolite does not function as an ion exchanger. Some material properties were measured. The Poisson ratio and Young`s modulus were slightly smaller in glass-bonded zeolite than in borosilicate glass. Density depended on zeolite fraction. The glass-bonded zeolite represents a promising mineral waste form for IFR salt.

Lewis, M.A.; Fischer, D.F. [Argonne National Lab., IL (United States); Murphy, C.D. [Univ. of Cincinnati, OH (United States)

1994-05-01

126

Mechanism of Zeolite Crystallization and Thermochemical Properties of Some Synthetic Zeolites. Final Report.  

National Technical Information Service (NTIS)

During the period of 4/1/82 to 9/30/84, the Department of Energy has provided support for laboratory synthesis of zeolites, calorimetric determinations, and thermal analyses on synthetic zeolites. This Final Report to the DOE is written as 6 independent s...

J. G. Liou

1984-01-01

127

Salt-occluded zeolite waste forms: Crystal structures and transformability  

SciTech Connect

Neutron diffraction studies of salt-occluded zeolite and zeolite/glass composite samples, simulating nuclear waste forms loaded with fission products, have revealed complex structures, with cations assuming the dual roles of charge compensation and occlusion (cluster formation). These clusters roughly fill the 6--8 {angstrom} diameter pores of the zeolites. Samples are prepared by equilibrating zeolite-A with complex molten Li, K, Cs, Sr, Ba, Y chloride salts, with compositions representative of anticipated waste systems. Samples prepared using zeolite 4A (which contains exclusively sodium cations) as starting material are observed to transform to sodalite, a denser aluminosilicate framework structure, while those prepared using zeolite 5A (sodium and calcium ions) more readily retain the zeolite-A structure. Because the sodalite framework pores are much smaller than those of zeolite-A, clusters are smaller and more rigorously confined, with a correspondingly lower capacity for waste containment. Details of the sodalite structures resulting from transformation of zeolite-A depend upon the precise composition of the original mixture. The enhanced resistance of salt-occluded zeolites prepared from zeolite 5A to sodalite transformation is thought to be related to differences in the complex chloride clusters present in these zeolite mixtures. Data relating processing conditions to resulting zeolite composition and structure can be used in the selection of processing parameters which lead to optimal waste forms.

Richardson, J.W. Jr. [Argonne National Lab., IL (United States). Intense Pulsed Neutron Source Div.

1996-12-31

128

Tailoring the Structure of Hierarchically Porous Zeolite Beta through Modified Orientated Attachment Growth in a Dry Gel System.  

PubMed

The crystallization of zeolite beta in a dry gel system is found to follow the orientated attachment growth route, escorted with a temporal morphology change from bulky gel, through aggregation of the particulate to large zeolitic crystals. Modification of the precrystallized gel with organosilanes can be used to tune the morphology of the ultimate beta. When hexadecyltrimethoxysilane (HTS) is employed to modify precrystallized gel, a resumed secondary growth produces a hybrid mesocrystal of agglomerated nanozeolites. Combustive removal of organics leads to the formation of hierarchically porous zeolite beta of 100 to 160?nm, composed of nanocrystal building units ranging from 20 to 40?nm, with a noticeable micropore volume of 0.19?mL?g(-1) and a meso/macropore size between 5 and 80?nm. Conversely, when 1,8-bis(triethoxysilyl)octane (BTO) is utilized to modify the same precrystallized gel, assemblages of discrete beta nanozeolite of around 35?nm are generated. These assemblages construct a hierarchical zeolite beta with a micropore volume of 0.20?mL?g(-1) and auxiliary pores ranging from 5 to 100?nm. Both organosilanes bring about well-connected hierarchical pore networks. HTS has little effect on the Brønsted/Lewis acidity, whereas BTO causes a substantial reduction of strong Brønsted acid sites. The hierarchical beta zeolite-supported Pt catalyst exhibits improved catalytic performance for the hydroisomerization of n-heptane. PMID:25233842

Chen, Jiao; Hua, Weiming; Xiao, Yu; Huo, Qisheng; Zhu, Kake; Zhou, Xinggui

2014-11-01

129

2.5 Zeolites 2.5.1 Introduction  

E-print Network

). The value of zeolite catalysis to petroleum cracking is well in excess of $200 billion (MassNanoTech 2007 of zeolites' catalytic activity that is so important to the petrochemical industry. A second consequence

130

Alkylation of aniline with n -propyl alcohol over zeolites  

Microsoft Academic Search

The alkylation of aniline withn-propyl alcohol over ZSM-5 and Y zeolites has been studied. Ce-exchanged Y zeolites proved to be the most active for the alkylation of aniline byn-propyl alcohol. The reaction of N-propylaniline over zeolites has been investigated. N-alkylaniline decomposed over zeolites to aniline and alkene, which in turn rearrange to C-alkylanilines.n-Propyl derivatives were formed through an SN2 type

R. B. C. Pillai

1996-01-01

131

Salt-occluded zeolite waste forms: Crystal structures and transformability  

Microsoft Academic Search

Neutron diffraction studies of salt-occluded zeolite and zeolite\\/glass composite samples, simulating nuclear waste forms loaded with fission products, have revealed complex structures, with cations assuming the dual roles of charge compensation and occlusion (cluster formation). These clusters roughly fill the 6--8 â« diameter pores of the zeolites. Samples are prepared by equilibrating zeolite-A with complex molten Li, K, Cs, Sr,

J. W. Jr

1996-01-01

132

Transalkylation of toluene with trimethylbenzenes over large-pore zeolites  

Microsoft Academic Search

Zeolites Beta, mordenite and Y were evaluated for their activity in transalkylation reaction of toluene with trimethylbenzenes. Zeolite Beta was found to possess the highest conversion in toluene–trimethylbenzene transalkylation as well as a higher stability in time-on-stream compared with mordenite and zeolite Y. The effect of Si\\/Al ratio in zeolite Beta was evaluated and it was found that transalkylation activity

Andrea Krej?í; Sulaiman Al-Khattaf; Muhammad Ashraf Ali; Martina Bejblová; Ji?í ?ejka

2010-01-01

133

Cerium uptake by zeolite A synthesized from natural clinoptilolite tuffs  

Microsoft Academic Search

Summary  Natural clinoptilolite tuffs from the Semnan region in Iran was used for the synthesis of zeolite A. The tuffs and synthesized zeolites were characterized by XRD and XRF. The sorption behavior of the synthesized zeolite toward cerium was studied. Using the Lagergren’s equation, the absorption constant was calculated. The measured distribution coefficient values (Kd) indicated that cerium uptake is higher

H. Faghihian; M. K. Amini; A. R. Nezamzadeh

2005-01-01

134

Natural zeolites in environmentally friendly processes and applications  

Microsoft Academic Search

An outline of the occurrences, features and environmental uses of the main sedimentary zeolites, namely chabazite, clinoptilolite, mordenite and phillipsite, is presented. After pointing out that zeolite-bearing rocks should not be considered as substitutes for synthetic zeolites, as they are lacking of purity and constancy of composition, three major areas of environmental application are identified: soil amendment, cement manufacture and

Carmine Colella

1999-01-01

135

Ion exchange in a zeolite-molten chloride system  

Microsoft Academic Search

Electrometallurgical treatment of spent nuclear fuel results in a secondary waste stream of radioactive fission products dissolved in chloride salt. Disposal plans include a waste form that can incorporate chloride forms featuring one or more zeolites consolidated with sintered glass. A candidate method for incorporating fission products in the zeolites is passing the contaminated salt over a zeolite column for

R. H. Woodman; C. Pereira

1997-01-01

136

PARAMAGNETIC RESONANCE ABSORPTION OF GAMMA IRRADIATED SYNTHETIC ZEOLITES  

Microsoft Academic Search

The effect of gamma irradiation of synthetic zeolites was studied. ; Sodium X and sodium Y zeolites and also decationated samples prepared from these ; were irradiated in vacuum at room temperature with doses up to 20 megaroentgens. ; Two types of EPR signals were obtained. For the sodium Y and the sodium X ; zeolite a single line signal

D. N. Stamires; J. Turkevich

1963-01-01

137

The efficiency of Jordanian natural zeolite for heavy metals removal  

Microsoft Academic Search

The capability of Jordanian natural zeolite to remove nickel from aqueous solutions was experimentally investigated using a packed bed column. The zeolite samples were obtained from Jabal AL Aritayn in the northeast of Jordan. The effects of the initial concentration of nickel (C0), the packed bed length (L) and the zeolite grain size (Dp) on the adsorption process were considered.

Yazan Taamneh; Yazan TaamnehReyad Al Dwairi

2013-01-01

138

Zeolites as catalysts in oil refining.  

PubMed

Oil is nowadays the main energy source and this prevalent position most probably will continue in the next decades. This situation is largely due to the degree of maturity that has been achieved in oil refining and petrochemistry as a consequence of the large effort in research and innovation. The remarkable efficiency of oil refining is largely based on the use of zeolites as catalysts. The use of zeolites as catalysts in refining and petrochemistry has been considered as one of the major accomplishments in the chemistry of the XXth century. In this tutorial review, the introductory part describes the main features of zeolites in connection with their use as solid acids. The main body of the review describes important refining processes in which zeolites are used including light naphtha isomerization, olefin alkylation, reforming, cracking and hydrocracking. The final section contains our view on future developments in the field such as the increase in the quality of the transportation fuels and the coprocessing of increasing percentage of biofuels together with oil streams. This review is intended to provide the rudiments of zeolite science applied to refining catalysis. PMID:24671148

Primo, Ana; Garcia, Hermenegildo

2014-10-20

139

The ITQ-37 mesoporous chiral zeolite.  

PubMed

The synthesis of crystalline molecular sieves with pore dimensions that fill the gap between microporous and mesoporous materials is a matter of fundamental and industrial interest. The preparation of zeolitic materials with extralarge pores and chiral frameworks would permit many new applications. Two important steps in this direction include the synthesis of ITQ-33, a stable zeolite with 18 x 10 x 10 ring windows, and the synthesis of SU-32, which has an intrinsically chiral zeolite structure and where each crystal exhibits only one handedness. Here we present a germanosilicate zeolite (ITQ-37) with extralarge 30-ring windows. Its structure was determined by combining selected area electron diffraction (SAED) and powder X-ray diffraction (PXRD) in a charge-flipping algorithm. The framework follows the SrSi(2) (srs) minimal net and forms two unique cavities, each of which is connected to three other cavities to form a gyroidal channel system. These cavities comprise the enantiomorphous srs net of the framework. ITQ-37 is the first chiral zeolite with one single gyroidal channel. It has the lowest framework density (10.3 T atoms per 1,000 A(3)) of all existing 4-coordinated crystalline oxide frameworks, and the pore volume of the corresponding silica polymorph would be 0.38 cm(3) g(-1). PMID:19407798

Sun, Junliang; Bonneau, Charlotte; Cantín, Angel; Corma, Avelino; Díaz-Cabañas, María J; Moliner, Manuel; Zhang, Daliang; Li, Mingrun; Zou, Xiaodong

2009-04-30

140

Italian zeolitized rocks of technological interest  

NASA Astrophysics Data System (ADS)

Large areas of Italian territory are covered by thick and widespread deposits of zeolite-bearing volcaniclastic products. The main zeolites are phillipsite and chabazite spread over the whole peninsula, and clinoptilolite recorded only in Sardinia. A trachytic to phonolitic glassy precursor accounts for the formation of the former zeolites characterized by low Si/Al ratios (?3.00), while clinoptilolite is related to more acidic volcanism. The genesis of most of these zeolitized deposits is linked to pyroclastic flow emplacement mechanisms characterized by quite high temperatures and by the presence of abundant fluids. The main utilization of these materials has been and still is as dimension stones in the building industry. Currently, limited amounts are also employed in animal farming (dietary supplement, pet litter and manure deodorizer) and in agriculture as soil improvement and slow-release fertilizers. New fields of application have been proposed for these products on account of their easy availability, very low cost, their high-grade zeolites (50 70%), and good technological features such as high cation exchange capacities and adsorption properties.

de'Gennaro, M.; Langella, A.

1996-09-01

141

Zeolite-supported metal oxide sorbents for hot-gas desulfurization  

SciTech Connect

This paper describes the results of the development of supported mixed-metal oxide sorbents for hot-gas desulfurization capable of withstanding multiple sulfidation/regeneration cycles at 871 C (1600 F). The sorbents consisted of various combinations of copper, molybdenum, and/or manganese oxides supported on a high silica-containing zeolite. These sorbents were tested in a fixed-bed reactor with simulated coal gas at 205 kPa (15 psig). The combination of all three metal oxides displayed synergism in enhancing efficiency for H{sub 2}S removal and improved the crush strength on the pellets. Copper oxide was the most active component for reaction with H{sub 2}S, while molybdenum and manganese oxides appeared to act as catalysts/promoters. During multicycle testing, this ternary metal oxide sorbent retained its reactivity and mechanical strength.

Gasper-Galvin, L.D. [Dept. of Energy, Morgantown, WV (United States). Federal Energy Technology Center] [Dept. of Energy, Morgantown, WV (United States). Federal Energy Technology Center; Atimtay, A.T. [Middle East Technical Univ., Ankara (Turkey). Environmental Engineering Dept.] [Middle East Technical Univ., Ankara (Turkey). Environmental Engineering Dept.; Gupta, R.P. [Research Triangle Inst., NC (United States)] [Research Triangle Inst., NC (United States)

1998-10-01

142

Growth of zeolite crystals in the microgravity environment of space  

NASA Technical Reports Server (NTRS)

Zeolites are hydrated, crystalline aluminosilicates with alkali and alkaling earth metals substituted into cation vacancies. Typically zeolite crystals are 3 to 8 microns. Larger cyrstals are desirable. Large zeolite crystals were produced (100 to 200 microns); however, they have taken restrictively long times to grow. It was proposed if the rate of nucleation or in some other way the number of nuclei can be lowered, fewer, larger crystals will be formed. The microgravity environment of space may provide an ideal condition to achieve rapid growth of large zeolite crystals. The objective of the project is to establish if large zeolite crystals can be formed rapidly in space.

Sacco, A., Jr.; Sand, L. B.; Collette, D.; Dieselman, K.; Crowley, J.; Feitelberg, A.

1986-01-01

143

Hydrogen Purification Using Natural Zeolite Membranes  

NASA Technical Reports Server (NTRS)

The School of Science at Universidad del Turabo (UT) have a long-lasting investigation plan to study the hydrogen cleaning and purification technologies. We proposed a research project for the synthesis, phase analysis and porosity characterization of zeolite based ceramic perm-selective membranes for hydrogen cleaning to support NASA's commitment to achieving a broad-based research capability focusing on aerospace-related issues. The present study will focus on technology transfer by utilizing inorganic membranes for production of ultra-clean hydrogen for application in combustion. We tested three different natural zeolite membranes (different particle size at different temperatures and time of exposure). Our results show that the membranes exposured at 900 C for 1Hr has the most higher permeation capacity, indicated that our zeolite membranes has the capacity to permeate hydrogen.

DelValle, William

2003-01-01

144

Positron annihilation in zeolite 13X  

NASA Astrophysics Data System (ADS)

Results presented in previous papers on positron annihilation in zeolite 13X referred only to fully hydrated or dehydrated samples. In these investigations the dehydration process was studied based on measurements of positron lifetime spectra in zeolite 13X samples. All spectra were resolved into three or four components. Measurements show that water removal is most intensive at the beginning of pumping. For dehydration at higher temperature results suggest that the last molecules of ``zeolitic water'' are removed from the sample at a temperature of about 200 °C. It was found that independent of the stage of dehydration of the sample the intensity (I3+I4) of the two longest components in the spectrum is virtually constant (24%) and is equal to the intensity I3 of the longest component for the fully hydrated sample.

Habrowska, A. M.; Popiel, E. S.

1987-09-01

145

Quasi all-silica zeolite obtained by isomorphous degermanation of an as-made germanium-containing precursor.  

PubMed

Ge-containing ITQ-22 zeolites have been almost completely degermanated under strong acidic conditions without modifications of the framework topology. Simultaneous to Ge extraction, the framework was partially dissolved; mesopores were formed but the structure was maintained through the re-incorporation of some of silicon species at vacant sites. The presence of many defects in the degermanated framework enabled the incorporation of tetrahedral aluminum, opening the way to the preparation of new and stable acid catalysts with original topologies. PMID:24375808

Burel, Laurence; Kasian, Nataliia; Tuel, Alain

2014-01-27

146

Copper Cleanup  

NSDL National Science Digital Library

In this hands-on experiment, kids use chemistry to explore whether acids or bases are better at restoring a pennyâs shine. Kids follow the scientific process to test a common household cleaning products alongside ketchup, cola, and other kitchen staples, and may be surprised by the results! A downloadable data sheet is available on the Copper Cleanup activity resources page.

Wgbh

2010-01-01

147

Zeolite 5A Catalyzed Etherification of Diphenylmethanol  

ERIC Educational Resources Information Center

An experiment for the synthetic undergraduate laboratory is described in which zeolite 5A catalyzes the room temperature dehydration of diphenylmethanol, (C[subscript 6]H[subscript 5])[subscript 2]CHOH, producing 1,1,1',1'-tetraphenyldimethyl ether, (C[subscript 6]H[subscript 5])[subscript 2]CHOCH(C[subscript 6]H[subscript 5])[subscript 2]. The…

Cooke, Jason; Henderson, Eric J.; Lightbody, Owen C.

2009-01-01

148

POLYMER-ZEOLITE NANOCOMPOSITE HIGH-TEMPERATURE  

E-print Network

Efficiency · Industrial/Agricultural/Water End-Use Energy Efficiency · Renewable Energy TechnologiesPOLYMER-ZEOLITE NANOCOMPOSITE HIGH-TEMPERATURE PROTON-EXCHANGE-MEMBRANE FOR FUEL CELLS Prepared For: California Energy Commission Energy Innovations Small Grant Program Prepared By: Yushan Yan University

149

The poisoning of silver zeolite by organics  

Microsoft Academic Search

Silverzeolite was exposed to various organics to measure their effect on the silver zeolite's ability to subsequently adsorb iodine. The organics examined were alkanes, alkynes, aromatics, ketones, alcohols, and halocarbons (methyl and ethyl based). The reduction in iodine removal efficiency ranged from zero to 96%. Adding additional radicals to the base organic generally had the effect of decreasing the silver

J. G. Jolley; H. G. Tompkins

1984-01-01

150

Silver clusters and chemistry in zeolites  

SciTech Connect

The spectroscopic work done on silver clusters trapped in solid noble gas matrices at low temperature has been extensively reviewed by Ozin, and Henglein has done the same for photochemical studies of colloidal silver particles in solution. This article will review the chemistry of silver in zeolite hosts, including the synthesis and structures of silver clusters. 127 refs.

Sun, T.; Seff, K. (Univ. of Hawaii, Honolulu, HI (United States). Dept. of Chemistry)

1994-06-01

151

ARSENIC SEPARATION FROM WATER USING ZEOLITES  

EPA Science Inventory

Arsenic is known to be a hazardous contaminant in drinking water. The presence of arsenic in water supplies has been linked to arsenical dermatosis and skin cancer . Zeolites are well known for their ion exchange capacities. In the present work, the potential use of a variety of ...

152

ARSENIC SEPARATION FROM WATER USING ZEOLITES: SYMPOSIUM  

EPA Science Inventory

NRMRL-ADA-01134 Shevade, S, Ford*, R., and Puls*, R.W. "Arsenic Separation from Water Using Zeolites." In: 222nd ACS National Meeting, ACS Environmental Chemistry Division Symposia, Chicago, IL, 08/26-30/2001. 2001. 04/23/2001 This...

153

Dispersion enhanced metal/zeolite catalysts  

DOEpatents

Dispersion stabilized zeolite supported metal catalysts are provided as bimetallic catalyst combinations. The catalyst metal is in a reduced zero valent form while the dispersion stabilizer metal is in an unreduced ionic form. Representative catalysts are prepared from platinum or nickel as the catalyst metal and iron or chromium dispersion stabilizer.

Sachtler, W.M.H.; Tzou, M.S.; Jiang, H.J.

1987-03-31

154

Dispersion enhanced metal/zeolite catalysts  

DOEpatents

Dispersion stabilized zeolite supported metal catalysts are provided as bimetallic catalyst combinations. The catalyst metal is in a reduced zero valent form while the dispersion stabilizer metal is in an unreduced ionic form. Representative catalysts are prepared from platinum or nickel as the catalyst metal and iron or chromium dispersion stabilizer.

Sachtler, Wolfgang M. H. (Evanston, IL); Tzou, Ming-Shin (Evanston, IL); Jiang, Hui-Jong (Evanston, IL)

1987-01-01

155

MERCURY SEPARATION FROM POLLUTANT WATER USING ZEOLITES  

EPA Science Inventory

Arsenic is known to be a hazardous contaminant in drinking water that causes arsenical dermatitis and skin cancer. In the present work, the potential use of a variety of synthetic zeolites for removal of arsenic from water has been examined at room temperature. Experiments have...

156

Mechanism of methanol conversion over zeolite  

Microsoft Academic Search

Details of the reaction mechanisms of conversions of methanol to various alkanes and alkenes were investigated. A discussion of the autocatalytic phenomena of the conversion of methanol over ZSM-5 zeolite was included. The temperature dependence and acidity aspects of the reaction rate were discussed. Also the use of Nafion-H and heteropolyacids as catalysts of conversion was also included. A detailed

1983-01-01

157

UTILITY OF ZEOLITES IN REMOVAL OF INORGANIC AND ORGANIC WATER POLLUTANTS  

EPA Science Inventory

Zeolites are well known for their ion exchange, adsorption and acid catalysis properties. Different inorganic and organic pollutants have been removed from water at room temperature using various zeolites. Synthetic zeolite Faujasite Y has been used to remove inorganic pollutants...

158

CO2 SEPARATIONS USING ZEOLITE MEMBRANES  

SciTech Connect

Zeolite and other inorganic molecular sieve membranes have shown potential for separations based on molecular size and shape because of their small pore sized, typically less than 1 nm, and their narrow pore size distribution. The high thermal and chemical stability of these inorganic crystals make them ideal materials for use in high temperature applications such as catalytic membrane reactors. Most of the progress with zeolite membranes has been with MFI zeolites prepared on porous disks and tubes. The MFI zeolite is a medium pore size structure having nearly circular pores with diameters between .53 and .56 nm. Separation experiments through MFI membranes indicate that competitive adsorption separates light gas mixtures. Light gas selectivities are typically small, however, owing to small differences in adsorption strengths and their small sizes relative to the MFI pore opening. Furthermore, competitive adsorption does not work well at high temperature where zeolite membranes are stable and have potential application. Separation by differences in size has a greater potential to work at high temperature than competitive adsorption, but pores smaller than those in MFI zeolites are required. Therefore, some studies focused on the synthesis of a small, 8-membered-pore structures such as zeolite A (0.41-nm pore diameter) and SAPO-34, a chabazite (about .4-nm pore diameter with about 1.4 nm cages) analog. The small pore size of the zeolite A and SAPO-34 structures made the separation of smaller molecules by differences in size possible. Zeolite MFI and SAPO-34 membranes were prepared on the inside surface of porous alumina tubes by hydrothermal synthesis, and single gas and binary mixture permeances were measured to characterize the membrane's performance. A mathematical diffusion model was developed to determine the relative quantities of zeolite and non-zeolite pores in different membranes by modeling the permeation date of CO{sub 2}. This model expresses the total flux through the membrane as the sum of surface diffusion through zeolite pores and viscous flow and Knudsen diffusion through non-zeolite pores. As predicted by the model, the permeance of CO{sub 2} decrease with increasing pressure at constant pressure drop for membranes with few non-zeolite pores, but the permeance increased through viscous flow pores and was constant through pores allowing Knudsen diffusion. Membranes having more non-zeolite pores had lower CO{sub 2}/CH{sub 4} selectivities. The SAPO-34 membranes were characterized for light gas separation applications, and the separation mechanisms were identified. Single gas permeances of CO{sub 2}, N{sub 2}, and CH{sub 4} decreased with increasing kinetic diameter. For the best membrane at 300K, the He and H{sub 2} permeances were less than that of CO{sub 2}, because He, H{sub 2} and CO{sub 2} were small compared to the SAPO-34 pore, and differences in the heat of adsorption determined the permeance order. The small component permeated the fastest in CO{sub 2}/CH{sub 4}, CO{sub 2}/N{sub 2}, N{sub 2}/CH{sub 4}, H{sub 2}/CH{sub 4}, and H{sub 2}/N{sub 2} mixtures between 300 and 470 K. For H{sub 2}/CO{sub 2} mixtures, which were separated by competitive adsorption at room temperature, the larger component permeated faster below 400K. The room temperature CO{sub 2}/CH{sub 4} selectivity was 36 and decreased with temperature. The H{sub 2}/CH{sub 4} mixture selectivity was 8 and constant with temperature up to 480 K. Calcination, slow temperature cycles, and exposure to water vapor had no permanent effect on membrane performance, but temperature changes of approximately 30 K/min decreased the membrane's effectiveness. The effects of humidity on gas permeation were studied with SAPO-34 membranes of different qualities. Membranes with high CO{sub 2}/CH{sub 4} selectivities (greater than 20) were stable in water vapor under controlled conditions, but degradation was seen for some membranes. The degradation opened non-SAPO-34 pores that were larger than SAPO-34 pores as shown by the IC{sub 4}H{sub 10} permeance, C

Richard D. Noble; John L. Falconer

2001-06-30

159

Bioinspired conical copper wire with gradient wettability for continuous and efficient fog collection.  

PubMed

Inspired by the efficient fog collection on cactus spines, conical copper wires with gradient wettability are fabricated through gradient electrochemical corrosion and subsequent gradient chemical modification. These dual-gradient copper wires' fog-collection ability is demonstrated to be higher than that of conical copper wires with pure hydrophobic surfaces or pure hydrophilic surfaces, and the underlying mechanism is also analyzed. PMID:24038211

Ju, Jie; Xiao, Kai; Yao, Xi; Bai, Hao; Jiang, Lei

2013-11-01

160

Copper peroxide  

NASA Technical Reports Server (NTRS)

A number of oxidizing agents, including chlorine, bromine, ozone and other peroxides, were allowed to act on copper solutions with the intention of forming copper peroxide. The only successful agent appears to be hydrogen peroxide. It must be used in a neutral 50 to 30 percent solution at a temperature near zero. Other methods described in the literature apparently do not work. The excess of hydrogen must be quickly sucked out of the brown precipitate, which it is best to wash with alcohol and ether. The product, crystalline under a microscope, can be analyzed only approximately. It approaches the formula CuO2H2O. In alkaline solution it appears to act catalytically in causing the decomposition of other peroxides, so that Na2O2 cannot be used to prepare it. On the addition of acids the H2O2 is regenerated. The dry substance decomposes much more slowly than the moist but is not very stable.

Moser, L.

1988-01-01

161

Synthesis strategies in the search for hierarchical zeolites.  

PubMed

Great interest has arisen in the past years in the development of hierarchical zeolites, having at least two levels of porosities. Hierarchical zeolites show an enhanced accessibility, leading to improved catalytic activity in reactions suffering from steric and/or diffusional limitations. Moreover, the secondary porosity offers an ideal space for the deposition of additional active phases and for functionalization with organic moieties. However, the secondary surface represents a discontinuity of the crystalline framework, with a low connectivity and a high concentration of silanols. Consequently, hierarchical zeolites exhibit a less "zeolitic behaviour" than conventional ones in terms of acidity, hydrophobic/hydrophilic character, confinement effects, shape-selectivity and hydrothermal stability. Nevertheless, this secondary surface is far from being amorphous, which provides hierarchical zeolites with a set of novel features. A wide variety of innovative strategies have been developed for generating a secondary porosity in zeolites. In the present review, the different synthetic routes leading to hierarchical zeolites have been classified into five categories: removal of framework atoms, surfactant-assisted procedures, hard-templating, zeolitization of preformed solids and organosilane-based methods. Significant advances have been achieved recently in several of these alternatives. These include desilication, due to its versatility, dual templating with polyquaternary ammonium surfactants and framework reorganization by treatment with surfactant-containing basic solutions. In the last two cases, the materials so prepared show both mesoscopic ordering and zeolitic lattice planes. Likewise, interesting results have been obtained with the incorporation of different types of organosilanes into the zeolite crystallization gels, taking advantage of their high affinity for silicate and aluminosilicate species. Crystallization of organofunctionalized species favours the formation of organic-inorganic composites that, upon calcination, are transformed into hierarchical zeolites. However, in spite of this impressive progress in novel strategies for the preparation of hierarchical zeolites, significant challenges are still ahead. The overall one is the development of methods that are versatile in terms of zeolite structures and compositions, capable of tuning the secondary porosity properties, and being scaled up in a cost-effective way. Recent works have demonstrated that it is possible to scale-up easily the synthesis of hierarchical zeolites by desilication. Economic aspects may become a significant bottleneck for the commercial application of hierarchical zeolites since most of the synthesis strategies so far developed imply the use of more expensive procedures and reagents compared to conventional zeolites. Nevertheless, the use of hierarchical zeolites as efficient catalysts for the production of high value-added compounds could greatly compensate these increased manufacturing costs. PMID:23138888

Serrano, D P; Escola, J M; Pizarro, P

2013-05-01

162

Chemical Interactions in Multimetal/Zeolite Catalysts  

SciTech Connect

This two-year project has led to a significant improvement in the fundamental understanding of the catalytic action of zeolite-supported redox catalysts. It turned out to be essential that we could combine four strategies for the preparation of catalysts containing transition metal (TM) ions in zeolite cavities: (1) ion exchange from aqueous solution; (2) chemical vapor deposition (CVD) of a volatile halide onto a zeolite in its acidic form; (3) solid state ion exchange; and (4) hydrothermal synthesis of a zeolite having TM ions in its lattice, followed by a treatment transporting these ions to ''guest positions''. Technique (2) enables us to position more TM ions into cavities than permitted by the conventional technique (1).viz one positive charge per Al centered tetrahedron in the zeolite lattice. The additional charge is compensated by ligands to the TM ions, for instance in oxo-ions such as (GaO){sup +} or dinuclear [Cu-O-Cu]{sup 2+}. While technique (3) is preferred over CVD where volatile halides are not available, technique (4) leads to rather isolated ''ex lattice'' oxo-ions. Such oxo-ions tend to be mono-nuclear, in contrast to technique (2) which preferentially creates dinuclear oxo-ions of the same TM element. A favorable element for the present research was that the PI is also actively engaged in a project on the reduction of nitrogen oxides, sponsored by EMSI program of the National Science Foundation and the US Department of Energy, Office of Science. This combination created a unique opportunity to test and analyze catalysts for the one step oxidation of benzene to phenol and compare them with catalysts for the reduction of nitrogen oxides, using hydrocarbons as the reductant. In both projects catalysts have been used which contain Fe ions or oxo-ions in the cavities the zeolite MFI, often called ZSM-5. With Fe as the TM-element and MFI as the host zeolite we found that catalysts with high Fe content, prepared by technique (2) were optimal for the De-NO{sub x} reaction, but extremely unselective for benzene oxidation to phenol. Conversely, the catalysts prepared with (4) had the highest turnover frequency for benzene oxidation, but performed very poorly for NO{sub x} reduction with so-butane. In fact the Fe concentration in the former catalysts were so low that it was necessary to design a special experimental program for the sole purpose of showing that it is really the Fe which catalyzes the benzene oxidation, not some acid center as has been proposed by other authors. For this purpose we used hydrogen sulfide to selectively poison the Fe sites, without deactivating the acidic sites. In addition we could show that the hydrothermal treatment of catalysts prepared by technique (4) is essential to transform iron ions in the zeolite lattice to ''ex lattice ions'' in guest positions. That line of the work required very careful experimentation, because a hydrothermal treatment of a zeolite containing Fe ions in its cavities can also lead to agglomeration of such ions to nano-particles of iron oxide which lowers the selectivity for the desired formation of phenol. This part of the program showed convincingly that indeed Fe is responsible for the benzene oxidation catalysis. The results and conclusion of this work, including the comparison of different catalysts, was published in a number of papers in the scientific literature, listed in the attached list. In these papers also our analysis of the reaction orders and the possible mechanism of the used test reaction are given.

Sachtler, Wolfgang M. H.

2004-04-16

163

Foam flotation of zeolites: Application for zinc ion removal  

SciTech Connect

In this paper the solid/liquid separation of a NaY zeolite, a known cation exchanger, was investigated in the laboratory by foam flotation from aqueous suspensions. The main parameters affecting the process in batch experiments, such as the pH of the suspension, the type of collector, the cationic collector concentration, the zeolite concentration, and the ionic strength were examined. The optimum conditions for removal (flotation) of more than 95% of the zeolite were determined. Following flotation of the zeolite in the Na form, zinc ions were chosen to serve as an application for ion exchange by the zeolite (for metal recovery), followed by foam flotation of the exchanged form of the zeolite from solution.

Zouboulis, A.I.; Zamboulis, D.; Matis, K.A. (Aristotle Univ., Thessaloniki (Greece))

1991-01-01

164

Atomic sites and stability of Cs+ captured within zeolitic nanocavities  

PubMed Central

Zeolites have potential application as ion-exchangers, catalysts and molecular sieves. Zeolites are once again drawing attention in Japan as stable adsorbents and solidification materials of fission products, such as 137Cs+ from damaged nuclear-power plants. Although there is a long history of scientific studies on the crystal structures and ion-exchange properties of zeolites for practical application, there are still open questions, at the atomic-level, on the physical and chemical origins of selective ion-exchange abilities of different cations and detailed atomic structures of exchanged cations inside the nanoscale cavities of zeolites. Here, the precise locations of Cs+ ions captured within A-type zeolite were analyzed using high-resolution electron microscopy. Together with theoretical calculations, the stable positions of absorbed Cs+ ions in the nanocavities are identified, and the bonding environment within the zeolitic framework is revealed to be a key factor that influences the locations of absorbed cations. PMID:23949184

Yoshida, Kaname; Toyoura, Kazuaki; Matsunaga, Katsuyuki; Nakahira, Atsushi; Kurata, Hiroki; Ikuhara, Yumi H.; Sasaki, Yukichi

2013-01-01

165

Interaction of Microwaves with Synthetic Type A Zeolite Containing Water  

NASA Astrophysics Data System (ADS)

A synthetic honeycomb type A zeolite adsorbent was regenerated through microwave irradiation in a single-mode cavity microwave at 2.46 GHz. The regeneration mechanism was investigated by comparing the heating properties, thermogravimetric properties, and dielectric properties of the synthetic zeolite samples. The hydrated zeolite sample was easily heated to over 200 °C, although a difference in the impedance matching frequency of only 0.01 GHz sharply reduced the maximum heating and increased the regeneration time. The adsorbed water in the hydrated zeolite initially acted as a heating agent by absorbing microwave energy, because the dielectric loss factor of water is higher than that of synthetic zeolite around 2.45 GHz. From 50 to 250 °C, the zeolite itself also absorbed microwave energy.

Tanaka, Masahiro; Takayama, Sadatsugu; Sano, Saburo

2013-11-01

166

Transesterification of soybean oil with zeolite and metal catalysts  

Microsoft Academic Search

Transesterification of soybean oil with methanol was carried out at 60, 120, and 150°C in the presence of a series NaX faujasite zeolite, ETS-10 zeolite, and metal catalysts. The stock zeolites were exchanged with potassium and cesium; NaX containing occluded sodium oxide (NaOx\\/NaX) and occluded sodium azide (NaOx\\/NaX*). The catalysts were calcined at 500°C prior to use in order to

Galen J. Suppes; Mohanprasad A. Dasari; Eric J. Doskocil; Pratik J. Mankidy; Michael J. Goff

2004-01-01

167

Treatment of Acid Mine Drainage Using Fly Ash Zeolite  

Microsoft Academic Search

In this paper, two Indian fly ashes (from Talcher and Ramagundam) were converted into zeolites and both the raw fly ash and\\u000a zeolite were used to treat two British acidic mine waters. The results demonstrate that fly ash zeolites are more effective\\u000a than raw fly ash for treatment of acid mine drainage. Fly ash has been found effective for removal

Bably Prasad; Robert J. G. Mortimer

2011-01-01

168

Molten-salt method for the synthesis of zeolitic materials  

Microsoft Academic Search

The molten-salt method has been applied for the zeolitization of fly ash and other mineral wastes. Fly ash was converted into zeolitic materials by a simple thermal treatment at molten states of some salt mixtures without any addition of water. Various combinations of salt mixtures were employed for the zeolitization of fly ash, using NaOH, KOH, or NH4F as mineralizer,

Man Park; Choong Lyeal Choi; Woo Taik Lim; Myung Chul Kim; Jyung Choi; Nam Ho Heo

2000-01-01

169

Molten-salt method for the synthesis of zeolitic materials  

Microsoft Academic Search

Characterization of zeolitic materials synthesized by the newly developed molten-salt method was carried out. Their physicochemical properties were investigated and compared to those of zeolitic materials prepared by the conventional hydrothermal method. The molten-salt method exhibited much less elemental loss during the zeolitization process. The product yield based on the reaction weight was about twice as high in the molten-salt

Man Park; Choong Lyeal Choi; Woo Taik Lim; Myung Chul Kim; Jyung Choi; Nam Ho Heo

2000-01-01

170

Characterization of Y zeolites using sodium-23 MASNMR  

Microsoft Academic Search

Y zeolites have engendered a great deal of interest because of their large pore structure. As a result, considerable characterization work has been performed on the silica-alumina framework of Y and other zeolites. For example, the dealumination of Y zeolite has been extensively studied using various techniques including silicon-29 NMR, aluminum-27 NMR, and STEM\\/EDX analysis. In contrast, the characterization of

L. B. Welsh; S. L. Lambert

1988-01-01

171

Large zeolites - Why and how to grow in space  

NASA Technical Reports Server (NTRS)

The growth of zeolite crystals which are considered to be the most valuable catalytic and adsorbent materials of the chemical processing industry are discussed. It is proposed to use triethanolamine as a nucleation control agent to control the time release of Al in a zeolite A solution and to increase the average and maximum crystal size by 25-50 times. Large zeolites could be utilized to make membranes for reactors/separators which will substantially increase their efficiency.

Sacco, Albert, Jr.

1991-01-01

172

Cobalt nanoparticles prepared in faujasite zeolites by borohydride reduction  

Microsoft Academic Search

Metallic cobalt nanoparticles have been prepared in the faujasite zeolite by the reduction of the Co2+-exchanged zeolite with sodium borohydride aqueous solutions. The influences of the temperature used for treating the Co2+-faujasite zeolite before reduction and the concentration of NaBH4 solution on the degree of reduction and the size of cobalt particles have been investigated. Although the treatment of the

Ye Wang; Hongli Wu; Qinghong Zhang; Qinghu Tang

2005-01-01

173

Zeolite Crystal Growth in Microgravity and on Earth  

NASA Technical Reports Server (NTRS)

The Center for Advanced Microgravity Materials Processing (CAMMP), a NASA-sponsored Research Partnership Center, is working to improve zeolite materials for storing hydrogen fuel. CAMMP is also applying zeolites to detergents, optical cables, gas and vapor detection for environmental monitoring and control, and chemical production techniques that significantly reduce by-products that are hazardous to the environment. Shown here are zeolite crystals (top) grown in a ground control experiment and grown in microgravity on the USML-2 mission (bottom). Zeolite experiments have also been conducted aboard the International Space Station.

2003-01-01

174

Alkylation of o-toluidine with methanol over acidic zeolites  

Microsoft Academic Search

The catalytic property of H-beta zeolite in the methylation of o-toluidine was compared to that of other acidic zeolites, viz. HY, H-MOR, H-ZSM-5 and H-FER. The H-beta catalyst showed higher conversion of o-toluidine, the main product being 2,4-xylidine. The selectivity towards 2,4-dimethylaniline (2,4-xylidine) was about 69% (at 400°C) over H-beta zeolite and was selective than the other zeolites under study.

R Anand; R Maheswari; S. G Hegde; B. S Rao

2003-01-01

175

One-step brazing process to join CFC composites to copper and copper alloy  

NASA Astrophysics Data System (ADS)

The aim of this work is to develop a new single-step brazing technique to join carbon fibre reinforced carbon composite (CFC) to pure copper (Cu) and copper alloy (CuCrZr) for nuclear fusion applications. In order to increase the wettability of CFC by a copper-based brazing alloy containing no active metal, the composite surface was modified by direct reaction with chromium, which forms a carbide layer and allows a large reduction of the contact angle. After the CFC surface modification, the commercial Gemco ® alloy (Cu/Ge) was successfully used to braze CFC to pure copper and pure copper to CuCrZr by the same heat treatment. The shear strength of the CFC/Cu joints measured by single lap shear tests at room temperature was (34 ± 4) MPa, comparable to the values obtained by other joining processes and higher than the intrinsic CFC shear strength.

Salvo, Milena; Casalegno, Valentina; Rizzo, Stefano; Smeacetto, Federico; Ferraris, Monica; Merola, Mario

2008-02-01

176

Computational studies of water adsorption in zeolites  

SciTech Connect

We have performed high-level ab initio calculations using Hartree-Fock (HF) theory, Moller-Plesset perturbation theory (MP2), and density-functional theory (DFT) to study the geometry and energetics of the adsorption complex involving H{sub 2}O and the Bronsted acid site in the zeolite H-ZSM-5. These calculations use aluminosilicate cluster models for the zeolite framework with as many as 28 T atoms (T=Si, Al). We included geometry optimization in the local vicinity of the acid site at the MP2 and DFT levels of theory for the smallest cluster, while in the larger clusters this was done at the HF/6-31G(d) level of theory. We have also calculated corrections for zero-point energies, extensions to higher basis sets, and higher levels of electron correlation. Results for the adsorption energy and geometry of this complex are reported and compared with previous theoretical and experimental values.

Zygmunt, S.A. [Valparaiso Univ., IN (United States); Curtiss, L.A.; Iton, L.E. [Argonne National Lab., IL (United States)

1995-05-01

177

Three Mile Island zeolite vitirification demonstration program  

Microsoft Academic Search

The cleanup of the high-activity-level water at Three Mile Island (TMI) provides an opportunity to further develop waste management technology. Approximately 790,000 gallons of high-activity-level water at TMI's Unit-2 Nuclear Power Station will be decontaminated at the site using the submerged demineralizer system (SDS). In the SDS process, the cesium and strontium in the water are sorbed onto zeolite that

D. H. Siemens; D. E. Knowlton; M. W. Shupe

1981-01-01

178

Dehydrogenation of Light Alkanes over Zeolites  

Microsoft Academic Search

The conversion of light paraffins to olefins and the secondary reactions of the unsaturated compounds were investigated on H-ZSM5 and H-Y zeolites between 733 and 823 K. Steady state- and transient response-isotope tracing studies revealed that two mechanisms of dehydrogenation are operative. The main pathway is represented by monomolecular, protolytic dehydrogenation. This reaction contributes most to steady state olefin production.

Thomas F. Narbeshuber; Axel Brait; Kulathuyier Seshan; Johannes A. Lercher

1997-01-01

179

Quantitatively probing the Al distribution in zeolites.  

PubMed

The degree of substitution of Si(4+) by Al(3+) in the oxygen-terminated tetrahedra (Al T-sites) of zeolites determines the concentration of ion-exchange and Brønsted acid sites. Because the location of the tetrahedra and the associated subtle variations in bond angles influence the acid strength, quantitative information about Al T-sites in the framework is critical to rationalize catalytic properties and to design new catalysts. A quantitative analysis is reported that uses a combination of extended X-ray absorption fine structure (EXAFS) analysis and (27)Al MAS NMR spectroscopy supported by DFT-based molecular dynamics simulations. To discriminate individual Al atoms, sets of ab initio EXAFS spectra for various T-sites are generated from DFT-based molecular dynamics simulations, allowing quantitative treatment of the EXAFS single- and multiple-photoelectron scattering processes out to 3-4 atom shells surrounding the Al absorption center. It is observed that identical zeolite types show dramatically different Al distributions. A preference of Al for T-sites that are part of one or more 4-member rings in the framework over those T-sites that are part of only 5- and 6-member rings in an HBEA150 zeolite has been determined using this analysis. PMID:24815517

Vjunov, Aleksei; Fulton, John L; Huthwelker, Thomas; Pin, Sonia; Mei, Donghai; Schenter, Gregory K; Govind, Niranjan; Camaioni, Donald M; Hu, Jian Zhi; Lercher, Johannes A

2014-06-11

180

A new family of two-dimensional zeolites prepared from the intermediate layered precursor IPC-3P obtained during the synthesis of TUN zeolite.  

PubMed

The crystallization of zeolite TUN with 1,4-bis(N-methylpyrrolidinium)butane as template proceeds through an intermediate, designated IPC-3P, following the Ostwald rule of successive transformations. This apparently layered transient product has been thoroughly investigated and found to consist of MWW monolayers stacked without alignment in register, that is, disordered compared with MCM-22P. The structure was confirmed based on X-ray diffraction and high-resolution (HR)TEM analysis. The layered zeolite precursor IPC-3P can be swollen and pillared affording a combined micro- and mesoporous material with enhanced Brunauer-Emmett-Teller (BET) surface area (685?m(2) g(-1) ) and greater accessibility of Brønsted acid sites for bulky molecules. This mesoporous material was probed with 2,6-di-tert-butylpyridine (DTBP). IPC-3P and its modification create a new layered zeolite sub-family belonging to the MWW family. FTIR data indicate that (Al)MWW materials MCM-22 and IPC-3 with Si/Al ratios greater than 20 exhibit a lower relative ratio of Brønsted to Lewis acid sites than MCM-22 (with Si/Al ratios of around 13), that is, less than 2 versus more than 3, respectively. This is maintained even upon pillaring and warrants further exploration of materials like IPC-3P with a higher Al content. The unique XRD features of IPC-3P indicating misaligned stacking of layers and distinct from MCM-22P, are also seen in other MWW materials such as EMM-10P, hexamethonium-templated (HM)-MCM-22, ITQ-30, and UZM-8 suggesting the need for more detailed study of their identity and properties. PMID:24038214

Kub?, Martin; Roth, Wieslaw J; Greer, Heather F; Zhou, Wuzong; Morris, Russell E; P?ech, Jan; ?ejka, Ji?í

2013-10-01

181

Synthesis of zeolites from coal fly ash: an overview  

Microsoft Academic Search

Coal combustion by-products production in USA and EU is estimated in around 115 million tons per year. A large portion of this production is accounted for the coal fly ash (CFA). Cement and concrete manufacturing consumes most of the CFA produced. Zeolite synthesized from CFA is a minor but interesting product, with high environmental applications. Zeolites may be easily obtained

X Querol; N Moreno; J. C Umaña; A Alastuey; E Hernández; A López-Soler; F Plana

2002-01-01

182

Transport properties of alkanes through ceramic thin zeolite MFI membranes  

Microsoft Academic Search

Polycrystalline randomly oriented defect free zeolite layers on porous ?-Al2O3 supports are prepared with a thickness of less than 5 ?m by in situ crystallisation of silicalite-1. The flux of alkanes is a function of the sorption and intracrystalline diffusion. In mixtures of strongly and weakly adsorbing gases and a high loadings of the strongly adsorbing molecule in the zeolite

Z. A. E. P. Vroon; K. Keizer; M. J. Gilde; H. Verweij; A. J. Burggraaf

1996-01-01

183

Fission product removal from molten salt using zeolite  

Microsoft Academic Search

Spent nuclear fuel (SNF) can be treated in a molten salt electrorefiner for conversion into metal and mineral waste forms for geologic disposal. The fuel is dissolved in molten chloride salt. Non-transuranic fission products in the molten salt are ion-exchanged into zeolite A, which is subsequently mixed with glass and consolidated. Zeolite was found to be effective in removing fission

C. Pereira; B. D. Babcock

1996-01-01

184

Ion exchange in a zeolite-molten chloride system  

SciTech Connect

Electrometallurgical treatment of spent nuclear fuel results in a secondary waste stream of radioactive fission products dissolved in chloride salt. Disposal plans include a waste form that can incorporate chloride forms featuring one or more zeolites consolidated with sintered glass. A candidate method for incorporating fission products in the zeolites is passing the contaminated salt over a zeolite column for ion exchange. To date, the molten chloride ion-exchange properties of four zeolites have been investigated for this process: zeolite A, IE95{reg_sign}, clinoptilolite, and mordenite. Of these, zeolite A has been the most promising. Treating zeolite 4A, the sodium form of zeolite A , with the solvent salt for the waste stream-lithium-potassium chloride of eutectic melting composition, is expected to provide a material with favorable ion-exchange properties for the treatment of the waste salt. The authors constructed a pilot-plant system for the ion-exchange column. Initial results indicate that there is a direct relationship between the two operating variable of interest, temperature, and initial sodium concentration. Also, the mass ratio has been about 3--5 to bring the sodium concentration of the effluent below 1 mol%.

Woodman, R.H.; Pereira, C. [Argonne National Lab., IL (United States). Chemical Technology Div.

1997-07-01

185

ZEOLITE SYNTHESIS FROM PAPER SLUDGE ASH VIA ACID LEACHING  

Microsoft Academic Search

Paper sludge ash (PSA) typically has a low Si abundance and significant Ca content due to the presence of calcite fillers. Acid leaching with HCl was used to reduce the Ca content so that a zeolitic product with a high cation exchange capacity (CEC) could be synthesized. Zeolitic products were synthesized from raw ash and leached ash through reaction with

Takaaki Wajima; Yasuyuki Ikegami

2007-01-01

186

Removal of ammonium from greywater using natural zeolite  

Microsoft Academic Search

This paper focuses on the effectiveness of removing ammonium ion and the theoretical aspects of adsorption including adsorption isotherm, kinetics and thermodynamics as well as desorption–regeneration studies. Results have demonstrated that natural zeolite shows good performance with up to 97% for ammonium removal depending on contact time, zeolite loading, initial ammonium concentration and pH. The adsorption kinetics is best approximated

Nurul Widiastuti; Hongwei Wu; Ha Ming Ang; Dongke Zhang

2011-01-01

187

Radiation induced physical and chemical processes in zeolite materials  

Microsoft Academic Search

Ionic processes induced by high energy radiation in zeolites, including electron and hole trapping and related chemical reactions, are reviewed in this paper. Electronic structures of electrons localized in clusters of charge balancing cations and those solvated in zeolite confined water clusters are characterized by a combination of spectroscopic techniques such as ESR and transient UV–visible absorption. Reactivities of these

Guohong Zhang; Xinsheng Liu; J. Kerry Thomas

1997-01-01

188

Crewmember working on the mid deck Zeolite Crystal Growth experiment.  

NASA Technical Reports Server (NTRS)

View showing Payload Specialist Bonnie Dunbar, in the mid deck, conducting the Zeolite Crystal Growth (ZCG) Experiment in the mid deck stowage locker work area. View shows assembly of zeolite sample in the metal autoclave cylinders prior to insertion into the furnace.

1992-01-01

189

FUNDAMENTALS AND APPLICATIONS OF PERVAPORATION THROUGH ZEOLITE MEMBRANES  

EPA Science Inventory

Zeolite membranes are well suited for separating liquid-phase mixtures by pervaporation because of their molecular-sized pores and their hydrophilic/hydrophobic nature, and the first commercial application of zeolite membranes has been for dehydrating organics [1]. Because of ...

190

Zeolites in the Pine Ridge Indian Reservation, South Dakota  

USGS Publications Warehouse

Zeolites of possible commercial value occur in the Brule Formation of Oligocene age and the Sharps Formation (Harksen, 1961) of Miocene age which crop out in a wide area in the northern part of the Pine Ridge Indian Reservation. The thickness of the zeolite-bearing Interval and the extent of areas within the Interval which contain significant amounts of zeolites are far greater than was expected prior to this investigation. The shape of the zeolite-bearing Interval is tabular and the dimensions of Its exposure are roughly 10 ml x 200 mi x 150 ft (16 km x 160 km x 45 m) thick. Within the study area, there are tracts in which the zeolite resource potential is significant (see pl. 2). This report is intended to inform the Oglala Sioux Tribe of some of the most promising zeolite occurrences. Initial steps can then be taken by the Tribe toward possible development of the resources, should they wish to do so. The data contained herein identify areas of high zeolite potential, but are not adequate to establish economic value for the deposits. If development is recommended by the tribal government, we suggest that the tribal government contact companies involved in research and production of natural zeolites and provide them with the data in this report.

Raymond, William H.; Bush, Alfred L.; Gude, Arthur J., 3rd

1982-01-01

191

Synthesis of zeolite beta in fluoride media under microwave irradiation  

E-print Network

Synthesis of zeolite beta in fluoride media under microwave irradiation Dae Sung Kim a , Jong time of the material significantly, while addition of ammonium fluoride accelerated the crystallization of zeolite beta. In particular, microwave technique combined with fluoride species and seeding led to more

Kim, Ji Man

192

Selective thermal oxidation of hydrocarbons in zeolites by oxygen  

DOEpatents

A process for selective thermal oxidation of hydrocarbons adsorbed onto zeolite matrices. A highly selective thermal oxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls is carried out in solvent free zeolites under dark thermal conditions. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts.

Frei, Heinz (Berkeley, CA); Blatter, Fritz (Basel, CH); Sun, Hai (Saint Charles, MO)

2000-01-01

193

Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen  

DOEpatents

A process for selective thermal oxidation or photooxidation of hydrocarbons adsorbed onto zeolite matrices. A highly selective thermal oxidation and photooxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls in solvent free zeolites under dark thermal conditions or under irradiation with visible light. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts.

Frei, Heinz (Berkeley, CA); Blatter, Fritz (Basel, CH); Sun, Hai (Saint Charles, MO)

1999-01-01

194

Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen  

DOEpatents

A process for a combined selective thermal oxidation and photooxidation of hydrocarbons adsorbed onto zeolite matrices. A highly combined selective thermal oxidation and photooxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls in solvent free zeolites under dark thermal conditions or under irradiation with visible light. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts.

Frei, Heinz (Berkeley, CA); Blatter, Fritz (Basel, CH); Sun, Hai (Saint Charles, MO)

2001-01-01

195

Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen  

DOEpatents

A process is described for selective thermal oxidation or photooxidation of hydrocarbons adsorbed onto zeolite matrices. A highly selective thermal oxidation and photooxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls in solvent free zeolites under dark thermal conditions or under irradiation with visible light. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts. 19 figs.

Frei, H.; Blatter, F.; Sun, H.

1999-06-22

196

COPPER CORROSION RESEARCH UPDATE  

EPA Science Inventory

Copper release and corrosion related issues continue to be important to many water systems. The objective of this presentation is to discuss the current state of copper research at the USEPA. Specifically, the role of aging on copper release, use of phosphates for copper corrosio...

197

Synthesis of A-type zeolite membrane using a plate heater and its formation mechanism  

Microsoft Academic Search

The synthesis of zeolite membrane using a plate heater is described. Attempts have been made to synthesize zeolite membrane either by the static method, which is a typical zeolite synthesis method, or by the circulated solution system. In both methods, the zeolite membrane was selectively formed on the substrate that was heated with a plate heater. Liquid phase solution, which

Satoshi Yamazaki; Kazuo Tsutsumi

2000-01-01

198

Solid state radioluminescent sources using tritium-loaded zeolites, and their proposed use as process monitors  

Microsoft Academic Search

Zeolite-based tritium lamps are a possible alternative to traditional tritium gas tube light sources. Rare earth luminescing centers may be ion-exchanged into zeolite matrices. Close proximity of tritium atoms to the rate earths can be provided by highly tritiated water sorbed within the pore structure of the zeolite aluminosilicate matrix. Zeolites are optically clear and radiation stable. Light outputs up

J. T. Gill; D. B. Hawkins; C. L. Renschler

1992-01-01

199

KARAKTERISASI KOMPOSISI KIMIA, LUAS PERMUKAAN PORI DAN SIFAT TERMAL DARI ZEOLIT BAYAH, TASIKMALAYA, DAN LAMPUNG  

Microsoft Academic Search

CHARACTERIZATION OF CHEMICAL COMPOSITION, SURFACE AREA PORE, AND THERMAL PROPERTIES OF ZEOLITES FROM BAYAH, TASIKMALAYA, AND LAMPUNG. Characterization of chemical composition, surface area, pore radius, adsorption, and thermal properties of zeolites from Bayah, Tasikmalaya, and Lampung have been performed. The purpose of the characterization is to understand the characteristics of the three zeolites since different types of zeolite will yield

Dian Anggraini; Rosika Kriswarini

2007-01-01

200

Zeolites in Eocene basaltic pillow lavas of the Siletz River Volcanics, Central Coast Range, Oregon.  

USGS Publications Warehouse

Zeolites and associated minerals occur in a tholeiitic basaltic pillow lava sequence. Although the zeolite assemblages are similar to those found in other major zeolite occurrences in basaltic pillow lavas, regional zoning of the zeolite assemblages is not apparent. The formation of the different assemblages is discussed.-D.F.B.

Keith, T.E.C.; Staples, L.W.

1985-01-01

201

[Copper and copper alloys. Technology updates].  

PubMed

The correlations between copper and copper alloys and human health have been the subject of some recent and extensive scientific researches. The voluntary risks evaluation, which anticipated the EU REACH Directive application, has shown that copper is a "safe" product for human health and for environment. In addition, it could be of great help thanks to its antibacterial properties. Copper tube can contribute in a relevant way to the prevention of water systems pollution by Legionella. Also the spreading of nosocomial infections is significantly contrasted by the use of copper and copper alloys for the production of articles intended for being frequently touched by people. The Environmental Protection Agency of the United States has in fact "registered" as antibacterial over 350 of copper alloys. PMID:23213799

Loconsolo, V; Crespi, M

2012-01-01

202

Synthesis and catalytic applications of combined zeolitic/mesoporous materials  

PubMed Central

Summary In the last decade, research concerning nanoporous siliceous materials has been focused on mesoporous materials with intrinsic zeolitic features. These materials are thought to be superior, because they are able to combine (i) the enhanced diffusion and accessibility for larger molecules and viscous fluids typical of mesoporous materials with (ii) the remarkable stability, catalytic activity and selectivity of zeolites. This review gives an overview of the state of the art concerning combined zeolitic/mesoporous materials. Focus is put on the synthesis and the applications of the combined zeolitic/mesoporous materials. The different synthesis approaches and formation mechanisms leading to these materials are comprehensively discussed and compared. Moreover, Ti-containing nanoporous materials as redox catalysts are discussed to illustrate a potential implementation of combined zeolitic/mesoporous materials. PMID:22259762

Vernimmen, Jarian; Cool, Pegie

2011-01-01

203

Structural Characterization of Nanosheet-type MFI Zeolite  

NASA Astrophysics Data System (ADS)

Zeolites are microporous crystalline aluminosilicates and have ordered micropores of a few Å in the structure. Zeolites are widely used in petrochemistry and fine-chemical synthesis because strong acid sites within their uniform micropores enable size- and shape-selective catalysis. Here we show that appropriately designed bifunctional surfactants can direct the formation of zeolite structures on the mesoporous and microporous length scales simultaneously, and thus produce nanosheet-type MFI zeolite that are only 2 nm thick, which corresponds to the b-axis dimension of a single MFI unit cell. The nanosheet-type MFI zeolite showd a significantly increased surface area, high catalytic activities, and excellent thermal and hydrothermal stability.

Sakamoto, Yasuhiro; Choi, Minkee; Na, Kyungsu; Kim, Jeongnam; Park, Woojin; Ryoo, Ryong; Terasaki, Osamu

204

Rheological Influence of Synthetic Zeolite on Cement Pastes  

NASA Astrophysics Data System (ADS)

Self Compacting Concrete (SCC) is characterized by specific and particular mechanical properties, often due to the addition of components, able to modify the paste rheology. Concrete properties are strongly affected by characteristics of the fresh cement paste that is the continuous phase dispersing larger aggregates. Therefore, aiming to characterize mechanical properties of final concrete is relevant to know rheological properties of the base cement paste. In this work cement pastes for SCC were prepared by using, as additive, synthetic zeolite 5A in different amounts and they were analyzed by small amplitude oscillations. Experimental results have shown a relationship between dynamic moduli and zeolite content, identifying a proper level of zeolite addition. Moreover samples containing traditional fine additives, such as silica fume and limestone, were prepared and experimental data were compared to those obtained by using zeolite. It was found that zeolite seems to give better properties to cement paste than other additives can do.

Baldino, N.; Gabriele, D.; Frontera, P.; Crea, F.; de Cindio, B.

2008-07-01

205

Mineral resource of the month: natural and synthetic zeolites  

USGS Publications Warehouse

Robert Virta, mineral commodity specialist for the U.S. Geological Survey, prepared the following information about the zeolite industry. Volcanic rocks containing natural zeolites — hydrated aluminosilicate minerals that contain alkaline and alkaline-earth metals — have been mined worldwide for more than 1,000 years for use as cements and building stone. For centuries, people thought natural zeolites occurred only in small amounts inside cavities of volcanic rock. But in the 1950s and early 1960s, large zeolite deposits were discovered in volcanic tuffs in the western United States and in marine tuffs in Italy and Japan. And since then, similar deposits have been found around the world, from Hungary to Cuba to New Zealand. The discovery of these larger deposits made commercial mining of natural zeolite possible.

Virta, R.

2008-01-01

206

Copper Data Center Database  

NSDL National Science Digital Library

The Copper Data Center Database is provided free of charge by the Copper Development Association "to increase knowledge and awareness of copper, related technologies, and the role of copper in the environment." The database is an online bibliographic search engine of literature on copper, copper alloys and copper technology dating back to 1965 and is described as covering copper technology from smelting and hydrometallurgy through the performance of copper and copper alloys in their end-use applications and service environments. Users can search by standard methods including using keywords and titles or an impressive advanced search feature is also available. Although full text listings are not available, anyone interested in related subjects will appreciate this well designed and unique tool.

Association, Copper D.

207

Zeolitic Materials, Vol. 3, No. 1, December 2002, 29-35 Copyright 2002 Korean Zeolite Association 29  

E-print Network

trend until 0.1 M oxalic acid treatments. In the case of 0.5M and 1M oxalic acid treatments-Alumin > H-ZSM-5 > - Alumina, which was similar trend with the acid strength of catalysts. Zeolites are also to their solid acidity, constricted pore shape and redox property. We have found that beta zeolite exhibit

Kim, Ji Man

208

Zeolites as new chromatographic carriers for proteins--easy recovery of proteins adsorbed on zeolites by polyethylene glycol.  

PubMed

Zeolites are able to adsorb proteins on their surface and might be suitable as a new type of chromatographic carrier material for proteins and for their conjugates (Matsui et al., Chem. Eur. J. 7 (2001) 1555-1560). Interestingly, maximum adsorption was observed at the isoelectric point (pI) of each protein. The current study was performed to investigate the desorption of proteins from the zeolites at pI. Proteins adsorbed to zeolites could be desorbed at pI by polyethylene glycol (PEG), but not by conventional eluents. The eluted proteins still retained their activities. The zeolite Na-BEA was an especially good composite for desorption by PEG. Using this method for the adsorption and desorption of proteins at pI, we succeeded in separating various proteins. The application of zeolites to biochemistry and biotechnology is also discussed. PMID:12782034

Chiku, Hiroyuki; Matsui, Masayoshi; Murakami, Shizuka; Kiyozumi, Yoshimichi; Mizukami, Fujio; Sakaguchi, Kengo

2003-07-01

209

Dispersible Exfoliated Zeolite Nanosheets and Their Application as a Selective Membrane  

Microsoft Academic Search

Thin zeolite films are attractive for a wide range of applications, including molecular sieve membranes, catalytic membrane reactors, permeation barriers, and low-dielectric-constant materials. Synthesis of thin zeolite films using high-aspect-ratio zeolite nanosheets is desirable because of the packing and processing advantages of the nanosheets over isotropic zeolite nanoparticles. Attempts to obtain a dispersed suspension of zeolite nanosheets via exfoliation of

Kumar Varoon; Xueyi Zhang; Bahman Elyassi; Damien D. Brewer; Melissa Gettel; Sandeep Kumar; J. Alex Lee; Sudeep Maheshwari; Anudha Mittal; Chun-Yi Sung; Matteo Cococcioni; Lorraine F. Francis; Alon V. McCormick; K. Andre Mkhoyan; Michael Tsapatsis

2011-01-01

210

A study of zeolite film synthesis on porous substrates  

NASA Astrophysics Data System (ADS)

Synthetic zeolites are attractive for chemical processing applications due to their high thermal and chemical stability. Potential new applications include zeolite membranes for gas separation, catalysis, sensor application, etc. The use of zeolite ZSM-5 for gas separation has been widely used due to the intermediate pore size. The formation of a zeolite layer on the heterogeneous surface depends on several factors. This study was conducted in order to investigate the synthesis techniques and the conditions for zeolite layer formation for zeolite ZSM-5 and zeolite LTA. The synthesis of the zeolite ZSM-5 layer was performed using an electrophoretic deposition technique on alpha-alumina substrates. The effects of chemical composition and applied electrical potential were evaluated using SEM, gas permeation, and the Maxwell-Stefan model. The results show that the thickness of the layers is controlled by the synthesis concentration and electrical potential across two electrodes. This indicates that the surface charge has a strong influence on zeolite layer formation on a substrate. The evaluation of the zeolite layers was performed using gas permeation analysis and the modeling using the Maxwell-Stefan diffusion approach. This analysis reveals that small defects in less than 0.1% of the zeolite layer can give a difference of about two orders of magnitude between the membrane diffusivity and zeolite particle diffusivity, which resulted in the high gas permeation rates observed. The zeolite LTA framework is composed of an equal amount of silica and alumina arranged in a three-dimension tetrahedral structure. This high alumina content zeolite possesses a strong negative surface charge in a basic solution due to the substitution of aluminum atoms into a SiO4 tetrahedral structure making it difficult to form a continuous layer in solution. This study is conducted in order to understand the differences in the formation of the zeolite in a solution and on a surface. Synthesis parameters such as synthesis duration, chemical composition, and synthesis temperature were varied. The crystallization kinetics was carried out using the particle size measurement, percent crystallinity from XRD analysis, IR absorption of tetrahedra using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), and the exponential growth model. The relationship of the substrate variation to the zeolite layer quality was examined using SEM and gas permeation tests. The results show that the formation of the zeolite layer depends on the surface nucleation site, the mass transfer rate of the nutrient onto the surface, and the relative surface charge of the zeolite particles and substrates. The evaluation of the electrical double layer effect using the colloid particle interaction theory shows a strong repulsion between zeolite LTA particles and the substrates. Increasing the crystal size results in a stronger repulsion between particles, causing the particles to grow individually and precipitate out of the solution.

Oonkhanond, Bovornlak

211

Investigation of void-free electroplating method on copper column based solder bump for flip-chip interconnections  

Microsoft Academic Search

A void-free copper electroplating method on copper column based solder bump for flip-chip interconnection enabling reduction of the copper column void defects in the solder bump was investigated. The surface energy of the resist mask surface, which affects the wettability of the electroplating solution, was investigated by applying a surface modification technique with ultraviolet (UV) radiation treatment and oxygen plasma

Hiroshi Yamada; Komukai Toshiba-cho

2005-01-01

212

Characteristics of Lead Sorption by Zeolite Minerals  

NASA Astrophysics Data System (ADS)

Lead adsorption behavior was investigated using four Zeolite minerals (clinoptilolite, analcime, phillipsite and chabazite). The used Pb2+ concentrations were 0, 0.1, 0.5, 1.0, 2.0, 3.0 and 5 µmol mL-1. Results indicated that Pb2+ sorption followed the Langmuir adsorption isotherm, but over limited concentration ranges for clinoptilolite and analcime. The bindg energy (Kd) reached, 2.400 and 0.875 g L-1 for phillipsite and chabazite, respectively. The maximum adsorption capacity for such minerals reached 208.33 and 204.08 mg g-1 with correlation coefficient (R2) reached, 0.997 and 0.995, respectively. Meanwhile, two stages for Pb2+adsorption were observed with clinoptilolite and analcime in the low and high concentrations of the applied Pb2+. Data also was applicable to the Freundlich adsorption isotherm over the used entire Pb2+ concentration ranges. The binding energy (n) reached, 1.014, 1.005, 1.001 and 1.001 g L-1 for clinoptilolite, analcime, phillipsite and chabazite, respectively. However, the b values (maximum adsorption capacity) reached 202.582, 201.651, 207.062 and 206.871 mg g-1 with correlation coefficient (R2) nearly one for all studying minerals, respectively. Desorption data indicated that most of the sorbed Pb2+ was extractedin the 1st extraction following the adsorption experiment. The ability of the used zeolite minerals to retain Pb2+ was high and there were differences between the studied minerals in sorption of Pb2+. In conclusion, data eliminated that, zeolite minerals especially, philipsite and chabazite, could be successfully used as packing material in subsurface reactive barriers intercepting ground water plumes and for fixed bed reactors designed to remove Pb2+ from industrial wastewater.

Al-Sewailem, M. S.

213

[Zeolite catalysis in conversion of cellulosics  

SciTech Connect

To transform biomass into fermentable substrate for yeast, we are using zeolites instead of enzymes to catalyze the two bottleneck reactions in biomass conversion, xylose isomerization and ceuobiose hydrolysis. The experimental results on these reactions carried out over various zeolites and other catalysts are presented herein. The advantages and disadvantages of using these catalysts over enzymes are also discussed. Heterogeneous solid catalysts other than zeolites has been employed for cellobiose-to-glucose hydrolysis. The size and shape selectivity that makes zeoutes unique for some reactions can add diffusional hindrance. We have spent some time screening various known solid acidic catalysts. We report that a class of cationic ion exchange resins in the acidified form (e.g. Amberlite) has worked well as an acidic catalyst in hydrolyzing cellobiose to glucose. Our experimental results, together with those obtained from a homogeneous acid catalyst (e.g. sulfuric acid) for comparison are provided. Having succeeded in finding an alternative solid acid catalyst for hydrolysis, we explored other solid resin or other homogeneous but non-enzyme catalyst to carry out the xylose-to-xylulose isomerization. A fairly extensive search has been made. We explored the use of sodium aluminates in the homogeneous phase isomerization of glucose to fructose and obtained a very high conversion of glucose to fructose with the final mixture containing 85% of fructose instead of the common 45%. Fructose apparently complexes with aluminates, and its equilibrium concentration is shifted to considerably higher values than permitted by simple glucose/fructose equilibrium. We have recently found a number of catalysts capable of promoting isomerization between aldoses and ketoses. One solid resin, known as polyvinyl pyridine (PVP), is able to convert xylose to xylulose at a pH below 7. Our usage of alternative isomerization catalysts, including PVP, are described.

Tsao, G.T.

1992-01-01

214

[Zeolite catalysis in conversion of cellulosics  

SciTech Connect

To transform biomass into fermentable substrate for yeast, we are using zeolites instead of enzymes to catalyze the two bottleneck reactions in biomass conversion, xylose isomerization and ceuobiose hydrolysis. The experimental results on these reactions carried out over various zeolites and other catalysts are presented herein. The advantages and disadvantages of using these catalysts over enzymes are also discussed. Heterogeneous solid catalysts other than zeolites has been employed for cellobiose-to-glucose hydrolysis. The size and shape selectivity that makes zeoutes unique for some reactions can add diffusional hindrance. We have spent some time screening various known solid acidic catalysts. We report that a class of cationic ion exchange resins in the acidified form (e.g. Amberlite) has worked well as an acidic catalyst in hydrolyzing cellobiose to glucose. Our experimental results, together with those obtained from a homogeneous acid catalyst (e.g. sulfuric acid) for comparison are provided. Having succeeded in finding an alternative solid acid catalyst for hydrolysis, we explored other solid resin or other homogeneous but non-enzyme catalyst to carry out the xylose-to-xylulose isomerization. A fairly extensive search has been made. We explored the use of sodium aluminates in the homogeneous phase isomerization of glucose to fructose and obtained a very high conversion of glucose to fructose with the final mixture containing 85% of fructose instead of the common 45%. Fructose apparently complexes with aluminates, and its equilibrium concentration is shifted to considerably higher values than permitted by simple glucose/fructose equilibrium. We have recently found a number of catalysts capable of promoting isomerization between aldoses and ketoses. One solid resin, known as polyvinyl pyridine (PVP), is able to convert xylose to xylulose at a pH below 7. Our usage of alternative isomerization catalysts, including PVP, are described.

Tsao, G.T.

1992-12-31

215

Carbon dioxide sensitivity of zeolitic imidazolate frameworks.  

PubMed

Zeolitic imidazolate frameworks of zinc, cobalt, and cadmium, including the framework ZIF-8 commercially sold as Basolite Z1200, exhibit surprising sensitivity to carbon dioxide under mild conditions. The frameworks chemically react with CO2 in the presence of moisture or liquid water to form carbonates. This effect, which has been previously not reported in metal-organic framework chemistry, provides an explanation for conflicting reports on ZIF-8 stability to water and is of outstanding significance for evaluating the potential applications of metal-organic frameworks, especially for CO2 sequestration. PMID:24889776

Mottillo, Cristina; Friš?i?, Tomislav

2014-07-14

216

Growth of large zeolite crystals in space  

NASA Technical Reports Server (NTRS)

Synthesis studies performed using close analogs of triethanolamine (TEA) have shown that all three hydroxyl groups and the amine group in this molecule are necessary to provide nucleation suppression. Studies using C-13 nuclear magnetic resonance (NMR) revealed that the hydroxyl ions and the amine group are involved in the formation of an aluminum complex. It was also shown that silicate species fo not interact this way with TEA in an alkaline solution. These results suggest that successful aluminum complexation leads to nucleation in zeolite-A crystallization.

Sacco, A., Jr.; Dixon, A.; Thompson, R.; Scott, G.; Ditr, J.

1988-01-01

217

Electron transfer reactions within zeolites: Radical cation from benzonorbornadiene  

SciTech Connect

Zeolites are being used as solid acid catalysts in a number of commercial processes. Occasionally zeolites are also reported to perform as electron transfer agents. Recently, we observed that radical cations of certain olefins and thiophene oligomers can be generated spontaneously within ZSM-5 zeolites. We noticed that these radical cations generated from diphenyl polyenes and thiophene oligomers were remarkably stable (at room temperature) within ZSM-5 and can be characterized spectroscopically at leisure. We have initiated a program on electron transfer processes within large pore zeolites. The basis of this approach is that once a cation radical is generated within a large pore zeolite, it will have sufficient room to undergo a molecular transformation. Our aim is to identify a condition under which electron transfer can be routinely and reliably carried out within large pore zeolites such as faujasites. To our great surprise, when benzonorbornadiene A and a number of olefins were included in divalent cation exchanged faujasites. they were transformed into products very quickly (<15 min). This observation allowed us to explore the use of zeolites as oxidants. Results of our studies on benzonorbornadiene are presented in this communication. 16 refs., 1 fig.

Pitchumani, K.; Ramamurthy, V. [Tulane Univ., New Orleans, LA (United States)] [Tulane Univ., New Orleans, LA (United States); Corbin, D.R. [The Du Pont Company, Wilmington, DE (United States)] [The Du Pont Company, Wilmington, DE (United States)

1996-08-28

218

Synthesis of zeolite phases from combustion by-products.  

PubMed

Synthesis of zeolites from combustion by-products, including fly ash, bottom ash and rice husk ash, was studied. A molar ratio of SiO2/Al2O3 of 1.5 was used for the syntheses. Refluxing and hydrothermal methods were also used for synthesis for comparison. The reaction temperatures of refluxing and hydrothermal methods were 100 degrees C and 130 degrees C, respectively. Sodalite, phillipsite-K, and zeolite P1 with analcime were obtained when fly ash, bottom ash and rice husk ash were used as starting materials, respectively. With rice husk ash as a starting material, zeolite P1 was produced. This result had advantages over previous studies as there was no prior activation required for the synthesis. The concentrations and types of alkaline used in the synthesis also determined the zeolite type. The different zeolites obtained from three systems were measured for specific surface area and pore size by using BET and Hg-porosimetry, respectively. Ammonium exchange capacities of the synthesised powders containing zeolites, sodalite, zeolite P1 and phillipsite-K were 38.5, 65.0 and 154.7 meq 100 g(-1), respectively. PMID:20421244

Pimraksa, Kedsarin; Chindaprasirt, Prinya; Setthaya, Naruemon

2010-12-01

219

Zeolite Crystal Growth (ZCG) Flight on USML-2  

NASA Technical Reports Server (NTRS)

The extensive use of zeolites and their impact on the world's economy has resulted in many efforts to characterize their structure, and improve the knowledge base for nucleation and growth of these crystals. The zeolite crystal growth (ZCG) experiment on USML-2 aimed to enhance the understanding of nucleation and growth of zeolite crystals, while attempting to provide a means of controlling the defect concentration in microgravity. Zeolites A, X, Beta, and Silicalite were grown during the 16 day - USML-2 mission. The solutions where the nucleation event was controlled yielded larger and more uniform crystals of better morphology and purity than their terrestrial/control counterparts. The external surfaces of zeolite A, X, and Silicalite crystals grown in microgravity were smoother (lower surface roughness) than their terrestrial controls. Catalytic studies with zeolite Beta indicate that crystals grown in space exhibit a lower number of Lewis acid sites located in micropores. This suggests fewer structural defects for crystals grown in microgravity. Transmission electron micrographs (TEM) of zeolite Beta crystals also show that crystals grown in microgravity were free of line defects while terrestrial/controls had substantial defects.

Sacco, Albert, Jr.; Bac, Nurcan; Warzywoda, Juliusz; Guray, Ipek; Marceau, Michelle; Sacco, Teran L.; Whalen, Leah M.

1997-01-01

220

Catalytic pyrolysis using UZM-44 aluminosilicate zeolite  

DOEpatents

A new family of aluminosilicate zeolites designated UZM-44 has been synthesized. These zeolites are represented by the empirical formula Na.sub.nM.sub.m.sup.k+T.sub.tAl.sub.1-xE.sub.xSi.sub.yO.sub.z where "n" is the mole ratio of Na to (Al+E), M represents a metal or metals from zinc, Group 1, Group 2, Group 3 and or the lanthanide series of the periodic table, "m" is the mole ratio of M to (Al+E), "k" is the average charge of the metal or metals M, T is the organic structure directing agent or agents, and E is a framework element such as gallium. The process involves contacting a carbonaceous biomass feedstock with UZM-44 at pyrolysis conditions to produce pyrolysis gases comprising hydrocarbons. The catalyst catalyzes a deoxygenation reaction converting oxygenated hydrocarbons into hydrocarbons and removing the oxygen as carbon oxides and water. A portion of the pyrolysis gases is condensed to produce low oxygen biomass-derived pyrolysis oil.

Nicholas, Christopher P; Boldingh, Edwin P

2013-12-17

221

Copper-phosphorus alloys offer advantages in brazing copper  

Microsoft Academic Search

Copper-phosphorus brazing alloys are used extensively for joining copper, especially refrigeration and air-conditioning copper tubing and electrical conductors. What is the effect of phosphorus when alloyed with copper? The following are some of the major effects: (1) It lowers the melt temperature of copper (a temperature depressant). (2) It increases the fluidity of the copper when in the liquid state.

1996-01-01

222

Hierarchical zeolites from class F coal fly ash  

NASA Astrophysics Data System (ADS)

Fly ash, a coal combustion byproduct is classified as types class C and class F. Class C fly ash is traditionally recycled for concrete applications and Class F fly ash often disposed in landfills. Class F poses an environmental hazard due to disposal and leaching of heavy metals into ground water and is important to be recycled in order to mitigate the environmental challenges. A major recycling option is to reuse the fly ash as a low-cost raw material for the production of crystalline zeolites, which serve as catalysts, detergents and adsorbents in the chemical industry. Most of the prior literature of fly ash conversion to zeolites does not focus on creating high zeolite surface area zeolites specifically with hierarchical pore structure, which are very important properties in developing a heterogeneous catalyst for catalysis applications. This research work aids in the development of an economical process for the synthesis of high surface area hierarchical zeolites from class F coal fly ash. In this work, synthesis of zeolites from fly ash using classic hydrothermal treatment approach and fusion pretreatment approach were examined. The fusion pretreatment method led to higher extent of dissolution of silica from quartz and mullite phases, which in turn led to higher surface area and pore size of the zeolite. A qualitative kinetic model developed here attributes the difference in silica content to Si/Al ratio of the beginning fraction of fly ash. At near ambient crystallization temperatures and longer crystallization times, the zeolite formed is a hierarchical faujasite with high surface area of at least 360 m2/g. This work enables the large scale recycling of class F coal fly ash to produce zeolites and mitigate environmental concerns. Design of experiments was used to predict surface area and pore sizes of zeolites - thus obviating the need for intense experimentation. The hierarchical zeolite catalyst supports tested for CO2 conversion, yielded hydrocarbons up to C9, a performance attesting the hierarchal pore structure. The preliminary techno-economic feasibility assessment demonstrates a net energy saving of 75% and cost saving of 63% compared to the commercial zeolite manufacturing process.

Chitta, Pallavi

223

Method of preparing sodalite from chloride salt occluded zeolite A  

SciTech Connect

A method is described for immobilizing waste chloride salts containing radionuclides and hazardous nuclear material for permanent disposal starting with a substantially dry zeolite and sufficient glass to form leach resistance sodalite with occluded radionuclides and hazardous nuclear material. The zeolite and glass are heated to a temperature up to about 1,000 K to convert the zeolite to sodalite and thereafter maintained at a pressure and temperature sufficient to form a sodalite product near theoretical density. Pressure is used on the formed sodalite to produce the required density.

Lewis, M.A.; Pereira, C.

1995-12-31

224

Method of preparing sodalite from chloride salt occluded zeolite  

DOEpatents

A method is described for immobilizing waste chloride salts containing radionuclides and hazardous nuclear material for permanent disposal starting with a substantially dry zeolite and sufficient glass to form leach resistant sodalite with occluded radionuclides and hazardous nuclear material. The zeolite and glass are heated to a temperature up to about 1000 K to convert the zeolite to sodalite and thereafter maintained at a pressure and temperature sufficient to form a sodalite product near theoretical density. Pressure is used on the formed sodalite to produce the required density.

Lewis, M.A.; Pereira, C.

1997-03-18

225

TEM studies of zeolites and ordered mesoporous materials.  

PubMed

In the present manuscript we have reviewed recent results on transmission electron microscopy of beam sensitive materials such as zeolites and ordered mesoporous materials. The results of the investigation of the fine structure of different zeolite types as MFI, ITQ-7 and the presence of mixture of phases are shown. In addition, the incorporation of metals within the zeolitic framework and their different applications as precursors for metal nanowire growth are also described. The combination of HRTEM together with electron crystallography for solving new ordered mesoporous silica and associated analytical techniques shows the strength of electron microscopy for a full characterization of such materials. PMID:21227705

Diaz, Isabel; Mayoral, Alvaro

2011-07-01

226

Zeolite crystal growth in space - What has been learned  

NASA Technical Reports Server (NTRS)

Three zeolite crystal growth experiments developed at WPI have been performed in space in last twelve months. One experiment, GAS-1, illustrated that to grow large, crystallographically uniform crystals in space, the precursor solutions should be mixed in microgravity. Another experiment evaluated the optimum mixing protocol for solutions that chemically interact ('gel') on contact. These results were utilized in setting the protocol for mixing nineteen zeolite solutions that were then processed and yielded zeolites A, X and mordenite. All solutions in which the nucleation event was influenced produced larger, more 'uniform' crystals than did identical solutions processed on earth.

Sacco, A., Jr.; Thompson, R. W.; Dixon, A. G.

1993-01-01

227

Interaction between zeolites and cluster compounds. Part 2.?Thermal decomposition of iron pentacarbonyl on zeolites  

Microsoft Academic Search

Thermal decomposition in a thermobalance of Fe(CO), adsorbed on alkali-metal, hydrogen-Y, dealuminated Y, L and omega zeolites proceeds stepwise via slow decarbonylation at low and high temperatures, separated by a fast endothermic reaction. Average CO\\/Fe ratios have been determined after each step. From i.r. results the former intermediates are assigned to species bearing bridging CO, whereas reaction products with CO\\/Fe

Thomas Bein; Peter A. Jacobs

1984-01-01

228

Design of Composite Photocatalyst of TiO2 and Y-Zeolite for Degradation of 2-Propanol in the Gas Phase under UV and Visible Light Irradiation.  

PubMed

Hydrophobic Y-zeolite (SiO2/Al2O3 = 810) and TiO2 composite photocatalysts were designed by using two different types of TiO2 precursors, i.e., titanium ammonium oxalate and ammonium hexafluorotitanate. The porous structure, surface property and state of TiO2 were investigated by various characterization techniques. By using an ammonium hexafluorotitanate as a precursor, hydrophobic modification of the Y-zeolite surface and realizing visible light sensitivity was successfully achieved at the same time after calcination at 773 K in the air. The prepared sample still maintained the porous structure of Y-zeolite and a large surface area. Highly crystalline anatase TiO2 was also formed on the Y-zeolite surface by the role of fluorine in the precursor. The usages of ammonium hexafluorotitanate were effective for the improvement of the photocatalytic performance of the composite in the degradation of 2-propanol in the gas phase under UV and visible light (? > 420 nm) irradiation. PMID:25314607

Kamegawa, Takashi; Ishiguro, Yasushi; Kido, Ryota; Yamashita, Hiromi

2014-01-01

229

On copper peroxide  

NASA Technical Reports Server (NTRS)

The action of hydrogen superoxide on copper salts in alcoholic solutions is studied. The action of hydrogen peroxide on copper hydroxide in alcoholic suspensions, and the action of ethereal hydrogen peroxide on copper hydroxide are discussed. It is concluded that using the procedure proposed excludes almost entirely the harmful effect of hydrolysis.

Moser, L.

1988-01-01

230

Copper: Technology & Standards  

NSDL National Science Digital Library

This article explains modern copper mining, ore extraction, and casting processes and details innovative copper products, major markets, service activities, and the future of copper in industry and everyday life. It was published in the November 1998 issue of the online magazine Innovations.

Cohen, Art; Association, Copper D.

231

Solid state NMR of porous materials : zeolites and related materials.  

PubMed

Solid state NMR spectroscopy applied to the science of crystalline micro- and mesoporous silica materials over the past 10 years is reviewed. A survey is provided of framework structure and connectivity analyses from chemical shift effects of various elements in zeolites including heteroatom substitutions, framework defects and pentacoordinated silicon for zeolites containing fluoride ions. New developments in the field of NMR crystallography are included. Spatial host-guest ordering and confinement effects of zeolite-sorbate complexes are outlined, with special emphasis on NMR applications utilizing the heteronuclear dipolar interaction. The characterization of zeolite acid sites and in situ NMR on catalytic conversions is also included. Finally, the motion of extra-framework cations is investigated in two tutorial cases of sodium hopping in sodalite and cancrinite. PMID:21452082

Koller, Hubert; Weiss, Mark

2012-01-01

232

Adsorption of trichlorophenol on zeolite and adsorbent regeneration with ozone.  

PubMed

A FAU-type zeolite was studied as an adsorbent to remove 2,4,6-trichlorophenol (TCP), a frequently detected recalcitrant pollutant in water bodies. Both adsorption isotherm and kinetics were studied with TCP concentrations from 10 to 100mg/L. It was observed that TCP was effectively adsorbed onto the zeolite with a high adsorption capacity and a high kinetic rate. Freundlich model and pseudo-second-order kinetics were successfully applied to describe the experimental data. The influence of solution pH was also studied. Furthermore, ozone was applied to regenerate the loaded zeolite. It was found that an effective adsorption of TCP was kept for at least 8 cycles of adsorption and regeneration. The ozonation also increased the BET specific surface of zeolite by over 60% and consequently enhanced the adsorption capacity. PMID:24632370

Zhang, Yongjun; Mancke, Raoul Georg; Sabelfeld, Marina; Geißen, Sven-Uwe

2014-04-30

233

Characterization of a zeolite membrane for catalytic membrane reactor application  

SciTech Connect

This paper describes the morphological and transport properties of a composite zeolite (silicalite) - alumina membrane. Some advantages obtained in combining the membrane with a conventional fixed-bed catalyst are also reported.

Giroir-Fendler, A.; Peureux, J.; Mozzanega, H.; Dalmon, J.A. [Institut de Recherches sur la Catalyse, Villeurbanne (France)

1996-12-31

234

Comparative study of the removal of coke from protonic zeolites  

SciTech Connect

The transformation of methanol was carried out at 400{degrees}C on four protonic zeolites: USHY (framework Si/Al ratio equal to 5), HZSM5 (Si/Al = 45), two mordenites HMOR (Si/Al = 7.5) and HMORDA (Si/Al = 80) prepared by dealumination of HMOR through hydrothermal and acid treatments. The composition of coke determined through the method developed in the authors` laboratory depended slightly on the zeolite. The amount of coke removed for the zeolites through oxidative treatment was determined as function of the temperature and for various coke contents. The rate of coke removal depended slightly on the coke content and on the coke composition by very much on the zeolite. In particular the coke of HMORDA and of HZSM5 was eliminated at high temperature only.

Gnep, N.S.; Roger, P.; Magnoux, P.; Guisnet, M. [Laboratoire de Catalyse en Chimie Organique, Poitiers (France)

1993-12-31

235

Single and Multiple Heteroatom Incorporation in MFI Zeolites  

E-print Network

Zeolites are crystalline inorganic solids that are industrially used for adsorption, ion exchange and catalysis. As catalysts, they have been particularly successful in the hydrocarbon processing industry due to their unique activities...

Garcia Vargas, Nataly

2012-11-05

236

Investigation of Zeolite Nucleation and Growth Using NMR Spectroscopy  

E-print Network

Zeolite nucleation and growth is a complex problem that has been widely investigated but still not completely understood. However, a full understanding of this process is required in order to develop predictive models for the rational design...

Rivas Cardona, Alejandra

2012-02-14

237

Anionic Emulsion-Mediated Synthesis of Zeolite Beta  

NASA Astrophysics Data System (ADS)

Well-crystallized zeolite beta is first synthesized in the anionic emulsion systems of cyclohexane/sodium dodecylbenzenesulfonate(SDBS)/pentanol/zeolite synthesis mixture. Beta materials are then characterized by XRD, SEM, and N2-adsorption techniques. Compared to beta samples grown using the same synthesis mixture in the absence of the anionic emulsion, the as-synthesized beta presents uniform and well-defined larger crystals. Interestingly, N2-adsorption results show that such beta sample possesses both ordered mesopores at 3.9 nm and macropores centered at 60.5 nm. These pores combined with the intricate micropores of the Beta crystal comprise the hierarchical porosity. The hierarchical pore-structured zeolite beta may have potential catalysis application in reactions involving large molecules. Additionally, control experiments are also performed to ascertain the effects of the individual emulsion components. Further synthesis study finds the transformation of zeolite beta to ZSM-5 through increasing oil contents, crystallization temperature and time.

Jin, Chao; Zhang, Ying; Gao, Wei; Cui, Lishan

238

Controlled release of preservatives using dealuminated zeolite Y.  

PubMed

This study demonstrates that dealuminated zeolite Y can act as a depot after adsorption of phenol derived preservatives. Upon suspension of zeolite loaded with the preservative m-cresol, equilibrium was quickly reached between free and adsorbed m-cresol. The equilibrium concentration of m-cresol was below 1 mM; however, it was enough to kill bacteria such as Escherichia coli and Staphylococcus aureus under metabolically active conditions. Killing of bacteria was not obtained under non-proliferating conditions and m-cresol was only released from the zeolite upon bacterial activity. Together, these results demonstrate an interesting potential use of dealuminated zeolite Y containing adsorbed preservatives for preventing microbial growth in numerous applications in industry and clinical setting. PMID:17599464

Eriksson, Håkan

2008-04-24

239

Dealumination of HZSM-5 zeolites. I. Calcination and hydrothermal treatment  

SciTech Connect

The effect of calcination and hydrothermal treatments on the structure and properties of HZSM-5 zeolites with a range of aluminum contents has been investigated. Characterization of the treated zeolites was undertaken with solid-waste NMR ({sup 27}Al and {sup 29}Si), infrared, nitrogen and water adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, chemical analysis, and {sup 129}Xe NMR spectroscopy. Both calcination and hydrothermal treatment were found to cause dealumination of the zeolite lattice and formation of extralattice aluminum species of low symmetry which remain within the pores of the zeolite. HZSM-5 with low aluminum content was found to be more resistant to dealumination by either method and the degree of dealumination was greater when steam was present in the treatment. {sup 129}Xe NMR was found to be a useful probe for the presence of extralattice aluminum in the pores of lattice dealuminated HZSM-5. 35 refs., 9 figs., 3 tabs.

Campbell, S.M. [Louisana State Univ., Shreveport, LA (United States)] [Louisana State Univ., Shreveport, LA (United States); [Univ. of Auckland (New Zealand); Bibby, D.M.; Meinhold, R.H. [Industrial Research Ltd., Petone (New Zealand)] [and others] [Industrial Research Ltd., Petone (New Zealand); and others

1996-06-01

240

Xenon NMR studies of dynamics and exchange in zeolites  

SciTech Connect

We have found, despite earlier reports to the contrary, that for many microporous solids with one-dimensional channels (ZSM-12, ALPO-5, VPI-5, SSZ-24) the chemical shift has an anisotropic component. For ALPO-11, a detailed model has been developed which accounts for the loading-dependent chemical shift in terms of intraparticle exchange of statistical distributions of xenon atoms with 0, 1 or 2 nearest neighbors. A similar model can be applied to ZSM-12 up to moderate loadings. At higher loading levels 2D exchange methods show that interparticle exchange occurs as well. The same approach was used to study interparticle exchange in X and Y zeolite mixtures, exchange amongst zeolite clusters of up to 8 xenon atoms in the supercages of AgA zeolite, and main channel - side pocket exchange in mordenite. The parameters derived are directly relevant to the understanding of sorption and diffusion processes in zeolites.

Moudrakovski, I.L.; Ratcliffe, C.I.; Ripmeester, J.A. [Steacie Institute for Molecular Sciences, Ottawa, Ontario (Canada)

1996-10-01

241

Hydration and dehydration of Zeolitic Tuff from Yucca Mountain, Nevada  

NASA Astrophysics Data System (ADS)

Naturally occurring zeolites expand and contract when hydrated or dehydrated. In tuffaceous rock composed largely of such zeolites, the entire rock may swell or contract significantly as the rock becomes saturated or dries out. If such rock is constrained, significant stresses may develop as a result of hydration or dehydration. We present experimental results that substantiate this. In a zeolitized, non-welded tuff from Yucca Mountain, NV, rock permeability governs the swelling rate since the major constituent, clinoptilolite, hydrates as fast as it can be exposed to water. At Yucca Mountain, where a nuclear waste repository is proposed, strata of welded, devitrified tuff overlie non-welded, zeolitic tuff. Should the hydration state of the units change significantly over the repository lifetime, additional stresses on the same order of magnitude as now exist may develop.

Kranz, R. L.; Bish, D. L.; Blacic, J. D.

1989-10-01

242

The efficiency of Jordanian natural zeolite for heavy metals removal  

NASA Astrophysics Data System (ADS)

The capability of Jordanian natural zeolite to remove nickel from aqueous solutions was experimentally investigated using a packed bed column. The zeolite samples were obtained from Jabal AL Aritayn in the northeast of Jordan. The effects of the initial concentration of nickel ( C 0), the packed bed length ( L) and the zeolite grain size ( D p) on the adsorption process were considered. The finding indicated that these parameters named had a significant effect on the removal of nickel by the Jordanian zeolite. The characteristic breakthrough curves of the adsorption process were measured. The Klinkenberg model was adopted to explain the kinetic behavior of the adsorption phenomena, and we attempted to fit the packed bed experimental data to the breakthrough curve. The effective diffusivity was estimated and used to predict breakthrough curves under other adsorption conditions.

Taamneh, Yazan; Al Dwairi, Reyad

2013-03-01

243

Review and Bibliography on Rock Solubility and Zeolite Minerals.  

National Technical Information Service (NTIS)

A bibliography was prepared and literature reviewed on the solubility of rock and rock-forming minerals, with emphasis on laboratory methods for solubility studies and the solubility of zeolites and calcium carbonate. As solubility is dependent on many va...

G. W. DePuy

1968-01-01

244

Structure of D[sub 2] in zeolite  

Microsoft Academic Search

We have measured the structure of D[sub 2] adsorbed in zeolite 13[ital X] at temperatures in the range 5.5 to 80 K at a variety of fillings. We find that the D[sub 2] molecules adsorb into well-defined adsorbtion sites in the zeolite structure. Two distinct adsorbtion sites, with binding energies on the order of 40 and 80 K, have been

M. P. Fang; P. E. Sokol; Y. Wang

1994-01-01

245

Mathematical modeling of fixed-bed oxidative regeneration of zeolite  

Microsoft Academic Search

1.The formation of a steady-state combustion front has been demonstrated in the fixed-bed oxidative regeneration of zeolite.2.Process conditions have been investigated in relation to their effects on the basic characteristics of the process, i.e., the average coke combustion rate and the maximum temperature rise in the zeolite. This work has demonstrated the important role of these characteristics in selecting optimal

V. I. Nazarok; O. I. Gaponenko; A. S. Shmelev; K. I. Patrilyak; P. N. Galich

1975-01-01

246

Performance of Silver Zeolite in a Radioiodine Monitor  

Microsoft Academic Search

Measurement were made of the interaction of 8Kr, 133Xe, CH3I (131I) and I2 (131I) with various silver zeolites and activated charcoals under varying relative humidities and temperatures. Results show silver zeolite has significantly less interaction with noble gases and high adsorption efficiencies for CH3I making it superior to charcoal for airborne radioiodine monitoring. The penetration of airborne iodine activity into

G. Y. SooHoo; Chien-chang Lin; R. M. Norris; C. D. Wilkinson

1975-01-01

247

Molecular sieve zeolite technology - the first twenty-five years  

Microsoft Academic Search

ABSTRACT In twenty—five years molecular sieve zeolites have substantially impacted adsorption and catalytic process technology throughout the chemical,process,industries;,provided timely solutions to energy,and environmental,problems;,and grown,to over,a hundred,million,dollar industry,worldwide.,The evolution,in zeolite materials with improved or novel properties has strongly influenced the expansion of their,applications, and provided new flexibility in the design of products and processes.

Edith M. Flanigen

1980-01-01

248

Zeolites in the Cascade Range of northern Oregon  

Microsoft Academic Search

Twenty-three zeolite minerals were identified during secondary mineralogy studies of late Tertiary volcanic rock outcrop samples and\\/or late Tertiary to Quaternary geothermal drill-hole specimens in three areas of the Oregon Cascade Range (near Mount Hood, the Breiten bush-Austin Hot Springs area, and Newberry volcano). The Neogene to Holocene volcanic rocks contain euhedral to subhedral zeolite crystals in open spaces of

1997-01-01

249

Origin of strong acidity in lanthanum-exchanged zeolites  

E-print Network

of this research was to determine the factors which give rise to strong acidity in zeolites. There is a linear relation between catalytic activity and zeolite framework aluminum number in the range of' 0 to 32 aluminum atoms per unit cell, whereas at higher... amounts of framework aluminum the activity decreases. This relationship is in agreement with a theoretical model of framework aluminum distribution and acidity, in which protons associated with isolated aluminum atoms are assigned a higher acidity...

Carvajal Freese, Ralf R.

2012-06-07

250

Chromophore-bearing zeolite materials as precursors of colored ceramics  

Microsoft Academic Search

This work investigates the possibility to obtain colored ceramics by firing compacts of the synthetic zeolite A, pre-loaded with chromophore metal cations, and gives also a preliminary evaluation of their technical properties. Natural zeolite-bearing materials, i.e., clinoptilolite- and phillipsite-rich tuffs, which naturally contain chromofore agents, such as iron oxides and hydroxides, have also been considered as ceramic precursors. The results

B. Liguori; A. Cassese; C. Colella

2005-01-01

251

Commander Bowersox Tends to Zeolite Crystal Samples Aboard Space Station  

NASA Technical Reports Server (NTRS)

Expedition Six Commander Ken Bowersox spins Zeolite Crystal Growth sample tubes to eliminate bubbles that could affect crystal formation in preparation of a 15 day experiment aboard the International Space Station (ISS). Zeolites are hard as rock, yet are able to absorb liquids and gases like a sponge. By using the ISS microgravity environment to grow better, larger crystals, NASA and its commercial partners hope to improve petroleum manufacturing and other processes.

2003-01-01

252

Microstructural modifications in swift ion irradiated PET  

NASA Astrophysics Data System (ADS)

Polyethylene terephthalte (PET) was irradiated with carbon (70 MeV) and copper (120 MeV) ions to analyze the induced modifications with respect to optical, structural and thermal properties. In the present investigation, the fluence for carbon irradiation was varied from 1×10 11 to 1×10 14 ions cm -2, while that for copper beam was kept in the range of 1×10 11 to 1×10 13 ions cm -2. UV-vis, FTIR, XRD and DSC techniques were utilized to study the induced changes. The analysis of UV-vis absorption studies reveals that there is decrease of optical energy gap up to 10% on carbon ion irradiation (at 1×10 14 ions cm -2), whereas the copper beam (at 1×10 13 ions cm -2) leads to a decrease of 49%. FTIR analysis indicated the formation of alkyne end groups along with the overall degradation of polymer with copper ion irradiation. X-ray diffraction analysis revealed that the semi-crystalline PET losses its crystallinity on swift ion irradiation. It was found that the carbon beam (1×10 14 ions cm -2) decreased the crystallite size by 16% whereas this decrease is of 12% in case of the copper ion irradiated PET at 1×10 13 ions cm -2. The loss in crystallinity on irradiation has been supported by DSC thermograms.

Singh, Ravinder; Singh Samra, Kawaljeet; Kumar, Ramneek; Singh, Lakhwant

2008-05-01

253

Photochemistry without protons. Radical cation chemistry in zeolites  

SciTech Connect

The interconversion of the C{sub 7}H{sub 8} molecular framework, especially norbornadiene (NBD) and quadricyclane (Q), has been considered for photochemical energy storage. Actually, very little was known about the details of these carbon-skeleton transformations, and only one radical cation species (NBD{sup +}{center_dot}) was characterized. The authors have undertaken a thorough study of these systems using zeolite matrices. They have shown that zeolites have exceptional properties, allowing unprecedented control of chemical reactivity. In the attached scheme, they outline some of the species they were able to characterize. The crucial aspect of the zeolite matrix is that one can tune the matrix-radical cation interaction by varying the matrix polarity. The ZSM-5 zeolites of identical structure with different Si/Al ratio are ideally suited for such study. Without discussing all the transformations, the authors point that several processes, such as the reverse Diels-Alder reaction are known to occur by involvement of highly excited states. Such reactions in zeolites means that sites in the zeolite matrix are able to stabilize high electronic states of ions, significantly lowering the potential energy barrier for such reactions. Thus, they are able to thermally drive otherwise photodriven reactions.

Trifunac, A.D.; Barnabas, M.V.

1994-06-01

254

Moderate-temperature zeolitic alteration in a cooling pyroclastic deposit  

USGS Publications Warehouse

The locally zeolitized Topopah Spring Member of the Paintbrush Tuff (13 Myr.), Yucca Mountain, Nevada, U.S.A., is part of a thick sequence of zeolitized pyroclastic units. Most of the zeolitized units are nonwelded tuffs that were altered during low-temperature diagenesis, but the distribution and textural setting of zeolite (heulandite-clinoptilolite) and smectite in the densely welded Topopah Spring tuff suggest that these hydrous minerals formed while the tuff was still cooling after pyroclastic emplacement and welding. The hydrous minerals are concentrated within a transition zone between devitrified tuff in the central part of the unit and underlying vitrophyre. Movement of liquid and convected heat along fractures from the devitrified tuff to the ritrophyre caused local devitrification and hydrous mineral crystallization. Oxygen isotope geothermometry of cogenetic quartz confirms the nondiagenetic moderate temperature origin of the hydrous minerals at temperatures of ??? 40-100??C, assuming a meteoric water source. The Topopah Spring tuff is under consideration for emplacement of a high-level nuclear waste repository. The natural rock alteration of the cooling pyroclastic deposit may be a good natural analog for repository-induced hydrothermal alteration. As a result of repository thermal loading, temperatures in the Topopah Spring vitrophyre may rise sufficiently to duplicate the inferred temperatures of natural zeolitic alteration. Heated water moving downward from the repository into the vitrophyre may contribute to new zeolitic alteration. ?? 1989.

Levy, S. S.; O'Neil, J. R.

1989-01-01

255

Solvent Evaporation Assisted Preparation of Oriented Nanocrystalline Mesoporous MFI Zeolites  

SciTech Connect

A solvent evaporation route to produce hierarchically porous zeolites with an oriented MFI nanocrystalline structure has been developed, and the method is scalable and productive. In this method, hexadecyltrimethoxysilane is added to an ethanol solution containing zeolitic precursors. A hard gel is formed during the evaporation process. Subsequent hydrothermal treatments produce the hierarchically porous zeolite. High resolution transmission electron microscopy (HRTEM) studies suggest that misoriented zeolite nuclei are produced in the very early stages of the hydrothermal treatment, but further reactions lead to single crystal-like aggregates composed of intergrowth nanocrystals with a mean interparticle pore diameter of 12 nm. All Al atoms exist in tetrahedral sites, as confirmed by 27Al magic angle spinning nuclear magnetic resonance (MAS NMR). Variable temperature hyperpolarized (HP) 129Xe NMR spectroscopy suggest a fast molecular diffusion process from the interconnection between micro- and mesopores. Catalytic conversion of acetone to the isobutene reactions show comparable (with respect to conventional zeolites) selectivity to isobutene. However, hierarchically porous zeolites display enhanced activity and durability because of the more accessible acidic sites in the hierarchically porous structures.

Zhu, Kake; Sun, Junming; Liu, Jun; Wang, Li Q.; Wan, Haiying; Hu, Jian Z.; Wang, Yong; Peden, Charles HF; Nie, Zimin

2011-07-01

256

Pyrolysis of scrap tyres with zeolite USY.  

PubMed

A zeolite catalyst of ultrastable Y-type (USY) was investigated in the research of two staged pyrolysis-catalysis of scrap tyres. Scrap tyres were pyrolysed in a fixed bed reactor and the evolved pyrolysis gases were passed through a secondary catalytic reactor. The main objective of this paper was to investigate the effect of zeolite USY on the yield of products and the composition of derived oil. The influences of several parameters such as pyrolysis temperature, catalytic temperature, catalyst/tyre ratio, heating rate, etc. on the yield of the derived oil, char and gas were investigated. It showed that the increase of catalytic temperature and catalyst/tyre ratio resulted in high yield of gas at the expense of the oil yield. For example, when the catalyst/tyre ratio increased from 0.25 to 1.0, the yield of gas increased from 30.5 to 49.9 wt.%, and the oil yield decreased nearly two-fold from 31.6 to 12.7 wt.%. The concentration of light naphtha (boiling point < 160 degrees C) was also investigated in this study. And the high catalyst/tyre ratio favored to increase the concentration of light naphtha (< 160 degrees C) in oil. In order to study the composition of derived oil, a distilled fraction (< 280 degrees C), which was 92.5 wt.% of the oil obtained from catalytic pyrolysis of scrap tyre at a pyrolysis temperature, catalytic temperature and catalyst/tyre ratio of 500, 400 degrees C and 0.5, respectively, was analyzed with gas chromatography/mass spectrometry (GC/MS). The distillate was found to contain 1.23 wt.% benzene, 9.35 wt.% toluene, 3.68 wt.% ethylbenzene, 12.64 wt.% xylenes, 1.81 wt.% limonene and 13.89 wt.% PAHs, etc., where the single ring aromatics represented a significant potential use as chemicals. PMID:16704900

Shen, Boxiong; Wu, Chunfei; Wang, Rui; Guo, Binbin; Liang, Cai

2006-09-21

257

Synthesis of core-shell structured zeolite-A@mesoporous silica composites for butyraldehyde adsorption.  

PubMed

A simple sol-gel process is followed to construct a thin layer of mesoporous silica shell core-shell structure on micrometer sized and nanometer sized zeolite A (micro-zeolite A@SiO2 and nano-zeolite A@SiO2 respectively). Further thickness of the silica shells has been tuned from 20 to 50 nm while the zeolite A particle size changes from nanometer to micrometer. Pores of the silica shells arranged orderly on the crystal-faces of zeolite-A cores. Typically, adsorption amount of the butyraldehyde towards these core-shell composite materials is investigated well and is verified to be almost double than that of the pristine zeolite A. Interestingly the nano-zeolite A core containing core-shell composite absorbs maximum butyraldehyde (314 mg/g) compared to the micro-zeolite A (266 mg/g), even if the mesoporous shell thickness of the nano-zeolite A@SiO2 composites is less (20 nm) than that of micro-zeolite A@SiO2 (50 nm). Both of these values are significantly larger than the pristine zeolite A (nano-zeolite A; 151 mg/g and micro-zeolite A; 146 mg/g). PMID:24910060

Yu, Haijun; Lv, Yingying; Ma, Kuoyan; Wang, Changguo; Xue, Zhaoteng; Zhao, Yujuan; Deng, Yonghui; Dai, Ya; Zhao, Dongyuan

2014-08-15

258

Hierarchical mesoporous zeolites: direct self-assembly synthesis in a conventional surfactant solution by kinetic control over the zeolite seed formation.  

PubMed

By kinetic control over the zeolite seed formation, we report the direct fabrication of hierarchical mesoporous zeolites using hexadecyl trimethyl ammonium bromide (CTAB) as the soft template in a conventional solution route. Nanometer-sized, subnanocrystal-type zeolite seeds with a high degree of polymerization are essential to prevent the formation of a separate amorphous mesoporous phase and the phase separation between the mesophase and zeolite crystals in the presence of CTAB and a certain amount of ethanol. The mechanisms for the formation of hierarchically porous zeolites in the solution process, including the effect of mother liquid aging, formation of subnanocrystal zeolite seeds and their self-assembly effect with CTAB, and the role of ethanol are proposed and discussed in detail. The prepared mesoporous ZSM-5 zeolite showed much higher catalytic activity than conventional counterparts for aldol condensations involving large molecules, especially in the synthesis of vesidryl. PMID:22084015

Zhu, Yan; Hua, Zile; Zhou, Jian; Wang, Lijun; Zhao, Jinjin; Gong, Yun; Wu, Wei; Ruan, Meiling; Shi, Jianlin

2011-12-16

259

Adsorption of Copper (II) Ions onto Surfactant-Modified Oil Palm Leaf Powder  

Microsoft Academic Search

Oil palm leaf powder (OPLP), an agricultural solid waste was used as adsorbent for the removal of copper (II) ions after modification with an anionic surfactant, sodium dodecyl benzene sulfonate (SDBS), CH3(CH2)11C6H4SO3Na. The copper (II) ions adsorption is highly dependent on pH and maximum removal was observed at pH 6, above which copper (II) started to precipitate. The equilibrium adsorption

M. Rafatullah; O. Sulaiman; R. Hashim; M. H. M. Amini

2011-01-01

260

Diffusion of an alkane molecule in siliceous zeolite beta Matthew Aronson  

E-print Network

1 Diffusion of an alkane molecule in siliceous zeolite beta Matthew was performed to study the diffusion of an alkane molecule in siliceous zeolite beta, as a function of chain length and temperature. The alkane was modeled

Shell, M. Scott

261

Study of pure-silica Zeolite Nucleation and Growth from Solution  

E-print Network

Zeolites are microporous crystalline materials, which are widely used in catalysis, adsorption, and ion-exchange processes. However, in most cases, the synthesis of novel zeolites as functional materials still relies on trial-and-error methods...

Li, Xiang

2011-10-21

262

Novel granular materials with microcrystalline active surfaces: waste water treatment applications of zeolite/vermiculite composites.  

PubMed

The application of zeolites as adsorbents for waste water management is limited by the facts that only synthetic zeolites have sufficient capacity and only natural zeolites can be manufactured in practical sizes for application, i.e. synthetic zeolites have too small a grain size to be used and natural zeolites have low adsorption capacities. This study seeks to resolve this problem by the manufacture of synthetic zeolites upon an expanded lamella matrix (vermiculite). The synthesized composite was tested to show whether it combined the useful properties of both natural and synthetic zeolites. The study compared: hydraulic conductivity, adsorption capacity and rate of attainment of equilibrium of the synthetic composite in comparison to both a natural and a synthetic zeolite. The results demonstrate that the vermiculite-based composite shows the same hydraulic properties as a natural clinoptilolite with similar grain size (2-5mm), however, the rate of adsorption and maximum coverage were improved by a factor of 4. PMID:17360021

Johnson, Christopher D; Worrall, Fred

2007-05-01

263

Removal of heavy metals from mine waters by natural zeolites.  

PubMed

In this study, we investigated the removal of Fe, Pb, Cd, and Zn from synthetic mine waters by a natural zeolite. The emphasis was given to the zeolite's behavior toward a few cations in competition with each other. Pb was removed efficiently from neutral as well as from acidic solutions, whereas the uptake of Zn and Cd decreased with low pH and high iron concentrations. With increasing Ca concentrations in solution, elimination of Zn and Cd became poorer while removal of Pb remained virtually unchanged. The zeolite was stable in acidic solutions. Disintegration was only observed below pH 2.0. Forward- and back-titration of synthetic acidic mine water were carried out in the presence and absence of zeolite to simulate the effects of a pH increase by addition of neutralizing agents and a re-acidification which can be caused by subsequent mixing with acidic water. The pH increase during neutralization causes precipitation of hydrous ferric oxides and decreased dissolved metal concentrations. Zeolite addition further diminished Pb concentrations but did not have an effect on Zn and Cd concentrations in solution. During re-acidification of the solution, remobilization of Pb was weaker in the presence than in the absence of zeolite. No substantial differences were observed for Fe, Cd, and Zn immobilization. The immobilization of the metals during pH increase and the subsequent remobilization caused by re-acidification can be well described by a geochemical equilibrium speciation model that accounts for metal complexation at hydrous ferric oxides, for ion exchange on the zeolite surfaces, as well as for dissolution and precipitation processes. PMID:16047799

Wingenfelder, Ulla; Hansen, Carsten; Furrer, Gerhard; Schulin, Rainer

2005-06-15

264

The use Na, Li, K cations for modification of ZSM-5 zewolite to control hydrocarbon cold-start emission  

SciTech Connect

This paper addresses the problem of controlling hydrocarbon emissions from cold-start of engines by investigating the adsorbents which could adsorb the hydrocarbons at cold temperatures and hold them to 250-300 ?. The materials, that has been studied, are based on the modification of ZSM-5 (SiO{sub 2}/Al{sub 2}O{sub 3} = 35) zeolite with Li, K, Na cations. It has been shown that the introduction of Li, Na and K in an amount that is equivalent to the content of Al in zeolite results in occurrence of toluene temperature desorption peaks at high-temperatures. The toluene temperature desorption curves for 5%Li-ZSM-5 and 2.3%Na-ZSM-5 zeolites are identical and have peak toluene desorption rate between 200 to 400 ?. Upon analysis of toluene adsorption isotherms for 2.3%Na-ZSM-5 and 5%Li-ZSM-5, it was concluded that the toluene diffusion inside of the modified zeolites channels is extremely slow and the sorption capacity of 2.3%Na-ZSM-5 is higher than with 5%Li-ZSM-5. The 2.3%Na-ZSM-5 didn't change toluene temperature programmed desorption (TPD) rate of curve after the treatment in environment with 10% ?{sub 2}? at 750-800 ? for about 28 h. The 2.3%Na-ZSM-5 zeolite is very promising as adsorbent to control the cold-start hydrocarbon emissions.

Golubeva V.; Rohatgi U.; Korableva, A.; Anischenko, O.; Kustov, L.; Nissenbaum, V; Viola, M.B.

2012-08-29

265

Polycrystalline MFI zeolite membranes: xylene pervaporation and its implication on membrane microstructure  

Microsoft Academic Search

This paper reports experimental results on pervaporation of pure xylene isomers and their binary mixtures through ?-alumina-supported zeolite MFI membranes. The membranes were permeable for all xylene isomers. Intensive fouling of the zeolite membrane was observed during the pervaporation experiments due to strong interaction of xylene molecules with the zeolite pores via ?-complexation. The pervaporation flux of pure xylene isomers

Karsten Wegner; Junhang Dong; Y. S Lin

1999-01-01

266

Friedel–Crafts acylation of aromatics and heteroaromatics by beta zeolite  

Microsoft Academic Search

Friedel–Crafts acylation of aromatic compounds such as anisole, 2-methoxynaphthalene, veratrole, isobutylbenzene and aromatic heterocycle compounds such as pyrrole, furan, thiophene, benzothiophene with different acid anhydrides is carried out in the batch mode with different forms of beta zeolite. The micronized beta zeolite shows manifold activity over normal zeolite in acylation reactions of aromatics.

Mannepalli Lakshmi Kantam; Kalluri Venkata Sri Ranganath; Mutyala Sateesh; Kota Balaji Shiva Kumar; Boyapati Manoranjan Choudary

2005-01-01

267

Oxygen transport in zeolite Y measured by quenching of encapsulated tris(bipyridyl)ruthenium  

E-print Network

reserved. Keywords: Oxygen sensor; Zeolite diffusion; Zeolite confinement 1. Introduction The microporousOxygen transport in zeolite Y measured by quenching of encapsulated tris(bpy)2þ 3 ) by oxygen. Oxygen saturated solutions of Ru(bpy)2þ 3 typically show about 70% quenching (I0=I

Dutta, Prabir K.

268

Synthesis and characterization of MCM-49/ZSM-35 composite zeolites in the hexamethyleneimine and cyclohexamine system  

E-print Network

Composite zeolites, especially micro/microporous composites [1­8] and micro/mesoporous composites [9Synthesis and characterization of MCM-49/ZSM-35 composite zeolites in the hexamethyleneimine ZSM-35 Composite zeolite Hexamethyleneimine Cyclohexamine a b s t r a c t A novel route for synthesis

Bao, Xinhe

269

DOI: 10.1002/anie.200702628 Aluminum Siting in Silicon-Rich Zeolite Frameworks: A Combined  

E-print Network

Zeolites DOI: 10.1002/anie.200702628 Aluminum Siting in Silicon-Rich Zeolite Frameworks: A Combined High-Resolution 27 Al NMR Spectroscopy and Quantum Mechanics/Molecular Mechanics Study of ZSM-5- graphic position of aluminum in zeolite frameworks governs the location of the active sites, which in turn

Sklenak, Stepan

270

Zeolites in catalysis. (Latest citations from the EI Compendex plus database). Published Search  

SciTech Connect

The bibliography contains citations concerning the preparation, properties, and activity of zeolites used as catalysts in chemical reactions and chemical apparatus. Topics include catalytic cracking, reduction, processing, and various catalytic effects of zeolites and zeolite-containing compounds for a wide variety of applications. (Contains 250 citations and includes a subject term index and title list.)

Not Available

1993-08-01

271

Exploration of molecular sieve zeolites for the cooling of building with solar energy  

Microsoft Academic Search

The usefulness of molecular sieve zeolites for solar sorption heating and cooling has been investigated. Two different approaches have been used, one in which the temperature of the zeolite is uniform, the other in which a temperature gradient is established across the zeolite. With one-square-foot test panels using the uniform temperature approach, overall engineering efficiencies as high as 75% for

D. I. Tchernev

1977-01-01

272

Penentuan kapasiti dan jenis pencerapan Zeolit asli terhadap bahan pencelup sintetik  

Microsoft Academic Search

Abstrak. Zeolit yang dikenali sebagai penapis molekul mempunyai sifat keliangan dan luas permukaan tinggi telah digunakan sebagai bahan penjerap untuk menjerap bahan pencelup daripada air sisa berwarna. Zeolit mordenit asli yang berasal dari Indonesia telah diubahsuai kepada bentuk yang bersifat bes dan dikaji sifat penjerapannya terhadap bahan pencelup sintetik bes kuning 11. Seterusnya, jenis penjerapan sampel zeolit terhadap bahan pencelup

Chai Mee Kin; Asiah Hussain; Pengajian Sains; Jalan Kajang-Puchong

273

Extrusion of zeolites: Properties of catalysts with a novel aluminium phosphate sintermatrix  

Microsoft Academic Search

A novel type of mechanically strong zeolite extrudates is introduced, in which the zeolite crystals, here ZSM-5, are embedded in a sintermatrix of aluminium phosphate with the crystal structure of tridymite. The pore size distribution in the matrix can be tailored through both, the choice of the size of the embedded particles and their amount in the extrudates. At zeolite

Jens Freiding; Florina-Corina Patcas; Bettina Kraushaar-Czarnetzki

2007-01-01

274

MINERALOGY AND PETROGRAPHY OF NEW OCCURENCES DEPOSITS OF THE ZEOLITIC TUFF IN NORTHEAST JORDAN  

Microsoft Academic Search

The occurrences deposits of the zeolitic tuff were studied in four areas through detailed geological mapping at a scale 1:50.000 in northeast Jordan and through exploration project. These deposits covered large areas and characterized by rich content, lateral and vertical homogenous distribution of the zeolite minerals. The zeolites are an abundant constituent in these deposits, which form more than 50%

K. Tarawneh

275

Properties of Zeolite A Obtained from Powdered Laundry Detergent: An Undergraduate Experiment.  

ERIC Educational Resources Information Center

Presents experiments that introduce students to the myriad properties of zeolites using the sodium form of zeolite A (Na-A) from laundry detergent. Experiments include extracting Na-A from detergent, water softening properties, desiccant properties, ion-exchange properties, and Zeolite HA as a dehydration catalyst. (JRH)

Smoot, Alison L.; Lindquist, David A.

1997-01-01

276

ZEOLITE PERFORMANCE AS AN ANION EXCHANGER FOR ARSENIC SEQUESTRATION IN WATER  

EPA Science Inventory

Zeolites are well known for their use in ion exchange and acid catalysis reactions. The use of zeolites in anion or ligand exchange reactions is less studied. The NH4+ form of zeolite Y (NY6, Faujasite) has been tested in this work to evaluate its performance for arsenic removal...

277

Toward a Database of Hypothetical Zeolite Structures David J. Earl, and Michael W. Deem*,  

E-print Network

Toward a Database of Hypothetical Zeolite Structures David J. Earl, and Michael W. Deem the sampling. We discuss construction of a database of hypothetical zeolite frameworks with this approach and discuss how the database may be used to search for new zeolite structures with specific material

Earl, David J.

278

SO2 REMOVAL FROM FLUE GASES USING UTILITY SYNTHESIZED ZEOLITES  

SciTech Connect

It is well known that natural and synthetic zeolites (molecular sieves) can adsorb gaseous SO{sub 2} from flue gas and do it more efficiently than lime based scrubbing materials. Unfortunately their cost ($500-$800 per ton) has deterred their use in this capacity. It is also known that zeolites are easy to synthesize from a variety of natural and man-made materials. The overall objective of the current work has been to evaluate the feasibility of having a utility synthesize its own zeolites, on-site, from fly ash and other recycled materials and then use these zeolites to adsorb SO{sub 2} from their flue gases. Work to date has shown that the efficiency of the capture process is related to the degree of crystallinity and the type of zeolite that forms in the samples. Normally, those samples cured at 150 C contained a greater proportion of zeolite and as such were more SO{sub 2} adsorptive than their low-temperature counterparts. However, in order for the project to be successful, on site synthesis must remain an option, i.e. 100 C synthesis. In light of this, the experimental focus now has two aspects. First, compositions of the starting materials are being altered by blending the current suite of fly ashes with ground glass cullet and silica fume to promote the formation and growth of well crystallized and highly adsorptive zeolites. Second, greater degrees of reaction at significantly lower temperatures are being promote by ball milling the fly ash prior to use, by the use of more concentrated caustic solutions, and by the addition of zeolite seeds to the reactants. In all cases studies will focus on the effect of structure type and degree of conversion on SO{sub 2} adsorption. Future work will concentrate on the study of the effect of weathering on the suitability of converting fly ash into zeolites. This is an especially important study, considering the acres of fly ash now in storage throughout the US.

Michael Grutzeck

1999-04-30

279

SO2 REMOVAL FROM FLUE GASES USING UTILITY SYNTHESIZED ZEOLITES  

SciTech Connect

It is well known that natural and synthetic zeolites (molecular sieves) can adsorb gaseous SO2 from flue gas and do it more efficiently than lime based scrubbing materials. Unfortunately their cost ($500-$800 per ton) has deterred their use in this capacity. It is also known that zeolites are easy to synthesize from a variety of natural and man-made materials. The overall objective of the current work has been to evaluate the feasibility of having a utility synthesize its own zeolites, on-site, from fly ash and other recycled materials and then use these zeolites to adsorb SO2 from their flue gases. Work to date has shown that the efficiency of the capture process is related to the degree of crystallinity and the type of zeolite that forms in the samples. Normally, those samples cured at 150°C contained a greater proportion of zeolite and as such were more SO2 adsorptive than their low-temperature counterparts. However, in order for the project to be successful, on site synthesis must remain an option, i.e. _100°C synthesis. In light of this, the experimental focus now has two aspects. First, compositions of the starting materials are being altered by blending the current suite of fly ashes with other fly ashes, ground glass cullet and silica fume to promote the formation and growth of well crystallized and highly adsorptive zeolites. Second, greater degrees of reaction at significantly lower temperatures are being promote by ball milling the fly ash prior to use, by the use of more concentrated caustic solutions, and by the addition of zeolite seeds to the reactants. In all cases studies will focus on the effect of structure type and degree of conversion on SO2 adsorption. Future work will concentrate on the study of the effect of weathering on the suitability of converting fly ash into zeolites. This is an especially important study, considering the acres of fly ash now in storage throughout the country.

MICHAEL GRUTZECK

1998-10-31

280

A high acid mesoporous USY zeolite prepared by alumination  

NASA Astrophysics Data System (ADS)

A high-acidity HUSY zeolite with mesoporous structure was prepared by alumination with a dilute aqueous NaAlO2 solution and characterized by XRD, N2 adsorption, IR framework vibration and 29Si MAS NMR methods. The results indicated the extra-framework aluminum was reinserted into the tetrahedral framework through isomorphic substitution of framework Si (0Al) sites by Al ions, whereas the crystal and micropore structure were unaltered. FTIR spectra of hydroxyl vibrations and pyridine adsorbed on realuminated zeolites showed that the number of Brønsted acid sites and strong Lewis acid sites increased whereas weak Lewis acid sites decreased twice. The mesoporous structure composed of inter-and intra-crystalline pores in the aluminated HUSY increased the external surface area of the zeolite, improving accessibility of molecules to the active sites and enhancing its catalytic ability. The realuminated HUSY zeolite supported with Ru catalyst exhibited a higher catalytic activity for benzene hydrogenation than the parent HUSY zeolite; the reaction rate in comparison to the mesozeolite increased by 5.5 times.

Ma, Jinghong; Kang, Yuhong; Ma, Ning; Hao, Wenming; Wang, Yan; Li, Ruifeng

2013-01-01

281

Risk assessment for the transportation of radioactive zeolite liners  

SciTech Connect

The risk is estimated for the shipment of radioactive zeolite liners in support of the Zeolite Vitrification Demonstration Program currently underway at Pacific Northwest Laboratory under the sponsorship of the US Department of Energy. This program will establish the feasibility of zeolite vitrification as an effective means of immobilizing high-specific-activity wastes. In this risk assessment, it is assumed that two zeolite liners, each loaded around July 1, 1981 to 60,000 Ci, will be shipped by truck around January 1, 1982. However, to provide a measure of conservatism, each liner is assumed to initially hole 70,000 Ci, with the major radioisotopes as follow: /sup 90/Sr = 3000 Ci, /sup 134/Cs = 7000 Ci, /sup 137/Cs = 60,000 Ci. Should shipment take place with essentially no delay after initial loading (regardless of loading date), the shipment loading would be only 2.7% higher than that for the assumed six-month delay. This would negligibly affect the overall risk. As a result of this risk assessment, it is concluded that the transport of the radioactive zeolite liners from TMI to PNL by truck can be conducted at an insignificant level of risk to the public.

Not Available

1982-01-01

282

Biogenic nanoparticles: copper, copper oxides, copper sulphides, complex copper nanostructures and their applications.  

PubMed

Copper nanoparticles have been the focus of intensive study due to their potential applications in diverse fields including biomedicine, electronics, and optics. Copper-based nanostructured materials have been used in conductive films, lubrification, nanofluids, catalysis, and also as potent antimicrobial agent. The biogenic synthesis of metallic nanostructured nanoparticles is considered to be a green and eco-friendly technology since neither harmful chemicals nor high temperatures are involved in the process. The present review discusses the synthesis of copper nanostructured nanoparticles by bacteria, fungi, and plant extracts, showing that biogenic synthesis is an economically feasible, simple and non-polluting process. Applications for biogenic copper nanoparticles are also discussed. PMID:23690046

Rubilar, Olga; Rai, Mahendra; Tortella, Gonzalo; Diez, Maria Cristina; Seabra, Amedea B; Durán, Nelson

2013-09-01

283

High adherence copper plating process  

DOEpatents

A process for applying copper to a substrate of aluminum or steel by electrodeposition and for preparing an aluminum or steel substrate for electrodeposition of copper. Practice of the invention provides good adhesion of the copper layer to the substrate.

Nignardot, Henry (Tesuque, NM)

1993-01-01

284

Zeolite-inspired low-k dielectrics overcoming limitations of zeolite films.  

PubMed

Spin-on zeolite films deposited from Silicalite-1 nanocrystal suspensions prepared by hydrothermal treatment of clear solutions have the required properties for insulating media in microelectronics. However, on the scale of the feature sizes in on-chip interconnects of a few tens of nanometers, their homogeneity is still insufficient. We discovered a way to overcome this problem by combining the advantages of the clear solution approach of Silicalite-1 synthesis with a sol-gel approach. A combination of tetraethyl orthosilicate and methyltrimethoxysilane silica sources was hydrolyzed and cocondensed in the presence of an aqueous tetraalkylammonium hydroxide template. The resulting suspension of nanoparticles of a few nanometers in size together with residual oligomeric silica species were spun onto support. The final zeolite-inspired low-k films (ZLK) with respect to pore size and homogeneity satisfied all requirements and presented excellent hydrophobicity, stiffness, and dielectric constant. The size and content of initially formed nanoparticles and the spatial hindrance promoted by occluded tetraalkylammonium molecules were found to be crucial elements in the definition of the final pore network. PMID:19053487

Eslava, Salvador; Urrutia, Jone; Busawon, Abheesh N; Baklanov, Mikhail R; Iacopi, Francesca; Aldea, Steliana; Maex, Karen; Martens, Johan A; Kirschhock, Christine E A

2008-12-24

285

Catalytic pyrolysis using UZM-39 aluminosilicate zeolite  

DOEpatents

A new family of coherently grown composites of TUN and IMF zeotypes has been synthesized and show to be effective catalysts for catalytic pyrolysis of biomass. These zeolites are represented by the empirical formula. Na.sub.nM.sub.m.sup.n+R.sub.rQ.sub.qAl.sub1-xE.sub.xSi.sub.yO.s- ub.z where M represents zinc or a metal or metals from Group 1, Group 2, Group 3 or the lanthanide series of the periodic table, R is an A,.OMEGA.-dihalosubstituted paraffin such as 1,4-dibromobutane, Q is a neutral amine containing 5 or fewer carbon atoms such as 1-methylpyrrolidine and E is a framework element such as gallium. The process involves contacting a carbonaceous biomass feedstock with UZM-39 at pyrolysis conditions to produce pyrolysis gases comprising hydrocarbons. The catalyst catalyzes a deoxygenation reaction converting oxygenated hyrdocarbons into hydrocarbons removing the oxygen as carbon oxides and water. A portion of the pyrolysis gases is condensed to produce low oxygen biomass-derived pyrolysis oil.

Nicholas, Christpher P; Boldingh, Edwin P

2013-12-17

286

Behavior Modification is not...  

ERIC Educational Resources Information Center

Identified are misconceptions of behavior modification procedures according to which behavior modification is connected mistakenly with noncontingent reinforcement, partial change of a teacher's behavior, decelerations of inappropriate behaviors only, dependency producing technology, teacher dominated activity, a single type of classroom…

Tawney, James W.; And Others

1973-01-01

287

Graphene synthesis and characterization on copper  

NASA Astrophysics Data System (ADS)

Graphene, two dimensional sheet of carbon atoms has recently gained attention as some of its properties are promising for electronics applications e.g. higher mobility that translates to higher operating frequency for devices geared towards radio frequency applications. Excellent optical transmittance combined with its semi metallic behavior makes it an important material for transparent contacts in solar cells. To bring graphene to the production level, synthesis methods are needed for its growth on wafer scale. It has been shown that chemical vapor deposition (CVD) is one of the techniques that can potentially synthesize wafer scale graphene. Recently copper has gained popularity as an important substrate material for graphene growth due to its lower carbon solubility, which allows better control over number of graphene layers. Here we report optimization of graphene growth on copper foils with our home made atmospheric pressure chemical vapor deposition (APCVD) setup. Graphene growth on copper under APCVD was non self-limiting similar to other reports. It was found that apart from growth parameters surface texture plays a very important role in graphene growth. In fact, few layer and bilayer graphene were obtained on the regions where copper surface was not uniform, confirmed by Raman spectroscopy. To improve copper surface texture thin layer of copper film was evaporated by electron beam evaporation before the graphene growth process. After this modification, monolayer graphene was obtained on areas as large as 300 microm x 300 microm confirmed by Raman area maps. Graphene transfer procedure was also optimized so that graphene on metal surface could be transferred to insulating substrate.

Mohsin, Ali

288

Synthetic Zeolites and Other Microporous Oxide Molecular Sieves  

NASA Astrophysics Data System (ADS)

Use of synthetic zeolites and other microporous oxides since 1950 has improved insulated windows, automobile air-conditioning, refrigerators, air brakes on trucks, laundry detergents, etc. Their large internal pore volumes, molecular-size pores, regularity of crystal structures, and the diverse framework chemical compositions allow "tailoring" of structure and properties. Thus, highly active and selective catalysts as well as adsorbents and ion exchangers with high capacities and selectivities were developed. In the petroleum refining and petrochemical industries, zeolites have made possible cheaper and lead-free gasoline, higher performance and lower-cost synthetic fibers and plastics, and many improvements in process efficiency and quality and in performance. Zeolites also help protect the environment by improving energy efficiency, reducing automobile exhaust and other emissions, cleaning up hazardous wastes (including the Three Mile Island nuclear power plant and other radioactive wastes), and, as specially tailored desiccants, facilitating the substitution of new refrigerants for the ozone-depleting chlorofluorocarbons banned by the Montreal Protocol.

Sherman, John D.

1999-03-01

289

Redeposited zeolitic rocks from the NE Rhodopes, Bulgaria  

NASA Astrophysics Data System (ADS)

The redeposited zeolitic rocks of Early Oligocene age in the NE Rhodopes, Bulgaria, are composed of zeolitic rock fragments. Material for the study was collected from four sections situated to the north of the Arda river, Haskovo district. These rocks occurred in a rhythmic series of sediments, occupying the interval between the products of two episodes of acidic volcanism (Lower Oligocene). They consist predominantly of subangular to subrounded clinoptilolitic rock fragments in which are preserved the specific relict textures of earlier zeolitized volcanic glass shards. The clinoptilolite content, which has been determined both under the microscope and by X-ray diffraction, varies between 10% and 80% but is usually about 50% by volume. Implications for the paleogeographic and tectonic regime of the area are considered.

Djourova, E. G.; Milakovska-Vergilova, Z. I.

1996-09-01

290

Computer simulations of benzene in faujasite-type zeolites  

SciTech Connect

The exact nature of the cation-benzene ring interaction is not yet known. In order to remedy this, energy minimization and Monte Carlo methods were used to probe the location and energetics of benzene in sodium zeolite-X and -Y. Sorption energies for the six-ring binding site in each of the zeolite models with the two forcefields (cff91 and cvff) are tabulated as function of Si/Al ratio. Both forcefields predict similar binding sites for each system; however, the final energies are sensitive to form and parameterization of the forcefield. Further work is needed to refine the forcefield for zeolite-sorbate interactions. 5 figs, 21 refs, 2 tabs.

Henson, N.J.; Cheetham, A.K. [California Univ., Santa Barbara, CA (United States). Dept. of Materials; Redondo, A. [Los Alamos National Lab., NM (United States); Levine, S.M.; Newsam, J.M. [Biosym Technologies Inc., San Diego, CA (United States)

1994-03-01

291

Mechanochemical approach for preparation of Mo-containing ?-zeolite  

NASA Astrophysics Data System (ADS)

The catalytically active solid materials were prepared by mechanochemical synthesis and impregnation. The starting material used as a support was ?-zeolite with a ratio SiO2/Al2O3=66. The molybdenum precursor was 12-molybdophosphoric heteropoly acid (HPMo). The samples were characterized by TPR and IR methods. The test reaction was thiophene hydrodesulfurization at atmospheric pressure. The interaction between HPMo and ?-zeolite in the catalyst sample, prepared by mechanochemical synthesis, is a weak one compared to that in the sample obtained on the basis of impregnation. The hydrodesulfurization activity of the milling sample is stabilized at a level about 50% higher than that of the sample prepared by impregnating HPMo on ?-zeolite. The higher hydrogenating activity of the mechanochemically treated sample is an additional advantage.

Kostova, N. G.; Spojakina, A. A.; Dutková, E.; Baláž, P.

2007-05-01

292

Multiple zeolite structures from one ionic liquid template.  

PubMed

This study reports the use of 1-butyl-3-methyl imidazolium methanesulfonate ionic liquid as a template in the synthesis of zeolites. It is found that the silicon source determines the formation of beta (BEA), mordenite framework inverted (MFI), or analcime (ANA) zeolites. Depending on this source, different preorganized complexes are obtained that drive the formation of the different zeolite structures. In the presence of ethanol, the ionic liquid form preorganized complexes that drive the formation of MFI. In its absence, BEA is obtained. Whereas, the large amount of sodium present when using sodium metasilicate leads to ANA formation. A molecular simulation study of the relative stability of the template-framework system and location of the template provides further insight into the mechanism of synthesis. PMID:23255393

Martínez Blanes, José María; Szyja, Bart?omiej M; Romero-Sarria, Francisca; Centeno, Miguel Ángel; Hensen, Emiel J M; Odriozola, José Antonio; Ivanova, Svetlana

2013-02-01

293

The environmental applications of activated carbon/zeolite composite materials.  

PubMed

Over the past couple of years, the resurgence of placing an effective and sustainable amendment to combat against the auxiliary industrial entities, remains a highly contested agenda from a global point. With the renaissance of activated carbon, there has been a steadily growing interest in the research field. Recently, the adoption of zeolite composite, a prestigious advanced catalyst which formulates the enhancement of adsorption rate and hydrogen storage capability, has fore fronted to be a new growing branch in the scientific community. Confirming the assertion, this paper presents a state of art review of activated carbon/zeolite composite technology, its fundamental background studies, and environmental implications. Moreover, its major challenges together with the future expectation are summarized and discussed. Conclusively, the expanding of activated carbon/zeolite composite represents a potentially viable and powerful tool, leading to the plausible improvement of environmental preservation. PMID:21035101

Foo, K Y; Hameed, B H

2011-02-17

294

Hot isostatic pressing of glass-zeolite composites  

SciTech Connect

Glass-zeolite waste forms are being developed for immobilizing the chloride waste salt generated from the electrometallurgical treatment of spent fuel. Glass-zeolite composites with high densities were made using hot isostatic pressing (HIP) techniques. Processing parameters were investigated to yield desirable structural ceramic properties such as mechanical, chemical, and thermal stability. Limits for these parameters were determined by differential thermal and thermogravimetric analysis. The resulting ceramic properties such as bulk density, open or apparent porosity, and leach resistance were determined. In addition, phase equilibria and particle-size distribution were observed by optical light and electron microscopy. Pre-HIP processing techniques were also studied to ensure intimate mixing of the glass and zeolite powders. Particle size distributions resulting from dry blending procedure are appropriate for needed flow and packing characteristics.

Hash, M.C.; Pereira, C.; Lewis, M.A. [and others

1996-05-01

295

Water adsorption in hydrophilic zeolites: experiment and simulation.  

PubMed

We have measured experimental adsorption isotherms of water in zeolite LTA4A, and studied the regeneration process by performing subsequent adsorption cycles after degassing at different temperatures. We observed incomplete desorption at low temperatures, and cation rearrangement at successive adsorption cycles. We also developed a new molecular simulation force field able to reproduce experimental adsorption isotherms in the range of temperatures between 273 K and 374 K. Small deviations observed at high pressures are attributed to the change in the water dipole moment at high loadings. The force field correctly describes the preferential adsorption sites of water at different pressures. We tested the influence of the zeolite structure, framework flexibility, and cation mobility when considering adsorption and diffusion of water. Finally, we performed checks on force field transferability between different hydrophilic zeolite types, concluding that classical, non-polarizable water force fields are not transferable. PMID:24022609

Castillo, Juan Manuel; Silvestre-Albero, Juaquin; Rodriguez-Reinoso, Francisco; Vlugt, Thijs J H; Calero, Sofia

2013-10-28

296

Influence of Crystal Expansion/Contraction on Zeolite Membrane Permeation  

SciTech Connect

X-ray diffraction was used to measure the unit cell parameters of B-ZSM-5, SAPO-34, and NaA zeolite powders as a function of adsorbate loading at 303 K, and in one case, at elevated temperatures. Most adsorbates expanded the zeolite crystals below saturation loading at 303 K: n-hexane and SF6 in B-ZSM-5, methanol and CO2 in SAPO-34, and methanol in NaA zeolite. As the loadings increased, the crystals expanded more. Changes in the unit cell volumes of B-ZSM-5 and SAPO-34 zeolite powders correlated with changes in permeation through zeolite membranes defects. When the zeolite crystals expanded or contracted upon adsorption, the defect sizes decreased or increased. In B-ZSM-5 membranes, the fluxes through defects decreased dramatically when n-hexane or SF6 adsorbed. In contrast, i-butane adsorption at 303 K contracted B-ZSM-5 crystals at low loadings and expanded them at higher loadings. Correspondingly, the flux through B-ZSM-5 membrane defects increased at low i-butane loadings and decreased at high loading because the defects increased in size at low loading and decreased at high loadings. At 398 K and 473 K, n-hexane expanded the B-ZSM-5 unit cell more as the temperature increased from 303 to 473 K. The silicalite-1 and B-ZSM-5 unit cell volumes expanded similarly upon n-hexane adsorption at 303 K; boron substitution had little effect on volume expansion.

Sorenson, Stephanie G [University of Colorado, Boulder; Payzant, E Andrew [ORNL; Noble, Richard D [University of Colorado, Boulder; Falconer, John L. [University of Colorado, Boulder

2010-01-01

297

COPPER RESEARCH UPDATE  

EPA Science Inventory

This presentation provides an update and overview of new research results and remaining research needs with respect to copper corrosion control issues. The topics to be covered include: occurrence of elevated copper release in systems that meet the Action Level; impact of water c...

298

Effect of natural and modified zeolite addition on anaerobic digestion of piggery waste.  

PubMed

The effect of natural and modified zeolites on the anaerobic degradation of acetate and methanol was evaluated by the determination of specific methane productivity (SMP) in batch minidigesters of 50 mL at doses of 0.01, 0.05 and 0.1 g of zeolite/g of VSS. The effects of the different zeolite concentrations were determined by the results of the SMP. A kinetic characterization with data of accumulated methane gas volume was also carried out. In the second phase of the study, the effects of natural and nickel zeolite concentrations were tested with piggery waste in laboratory scale digesters of 2.5 L operating at semi continuous mode, by increasing the organic load applied from 0.2 to 22.0 g TCOD/d corresponding to organic loading rates (OLR) of 0.1-8.8 g TCOD/l x d. A greater effect of modified zeolite on SMP was observed, with an increase of 8.5 times with magnesium zeolite, 4.4 times with cobalt zeolite and 2.8 times with nickel zeolite. Two phases were defined in the kinetic study and an increase of more than 2 times the apparent constant of digesters with modified zeolites was observed in the second phase when compared to unmodified natural zeolite. Modified natural zeolite addition to digesters can allow an increase in the potential biodegradability of piggery waste solid fraction and/or a considerable reduction of digestion volume. PMID:14640227

Milán, Z; Villa, P; Sánchez, E; Montalvo, S; Borja, R; Ilangovan, K; Briones, R

2003-01-01

299

Improved thermal stability of an organic zeolite by fluorination  

Microsoft Academic Search

The thermal stability of an organic zeolite material, namely 2,4,6-tris(4-bromo-3,5-difluorphenoxy)-1,3,5-triazin (Br-3,5-DFPOT),\\u000a was improved by fluorination of 2,4,6-tris(4-bromophenoxy)-1,3,5-triazin (BrPOT). The open pore structure (van der Waals diameter\\u000a of 10.5 Å) of the modified zeolite was observed up to 110 °C in comparison to 70 °C for BrPOT. Nitrogen sorption at low temperature\\u000a showed a type I isotherm and derived pore volumes thereof are in

Katharina Reichenbächer; Gaëtan Couderc; Antonia Neels; Karl Krämer; Edwin Weber; Jürg Hulliger

2008-01-01

300

Zeolite catalysis in the synthesis of isobutylene from hydrous ethanol  

NASA Astrophysics Data System (ADS)

This work deals with the synthesis of isobutylene from a hydrous ethanol feedstock over zeolites. The synthesis is accomplished in three steps: (1) low-temperature direct ethanol conversion to ethylene on H-ZSM-5 zeolite, (2) ethylene conversion to butene products over metal-exchanged zeolites, and (3) butene skeletal rearrangement to isobutylene over FER zeolites. The key to understanding and optimizing each synthesis step lies in the ability to control and regulate the zeolite acidity (Bronsted and Lewis)---both strength and number. Therefore, the continuous temperature programmed amine desorption (CTPAD) technique was further developed to simultaneously count the Bronsted acid sites and quantitatively characterize their strength. The adsorption of ethanol, reaction products, amines, coke and ethanol-derived residue (EDR) were monitored gravimetrically using the highly sensitive, novel Tapered Element Oscillating Microreactor (TEOM) apparatus. The TEOM was also used also in conjunction with CTPAD to characterize Bronsted acidity which is a new application for the instrument. For the first synthesis step, a parallel reaction exists which simultaneously produces diethyl ether and ethylene directly over H-ZSM-5. The reaction rates for each pathway were measured directly using a differential reactor operating at low temperatures (<473 K). Water in the ethanol feed enhances the rate of ethylene formation. A mechanism and kinetic expression are proposed for this reaction over H-ZSM-5, with diethyl-ether desorption and ethylene formation as the rate limiting steps. Heat of adsorption values measured from the independent microcalorimetry work reported in the literature are incorporated into the kinetic analysis which reduces the number of regressed parameters. For the remaining synthesis steps, several zeolite structures (ZSM-5, Y, FER) partially exchanged with Pd, Ti, Ni and Au were prepared and tested. It was determined from this screening study that the zeolites containing Pd are the most efficient catalysts for the dimerization reaction. Characterization results from x-ray diffraction (XRD), electron paramagnetic resonance (EPR) spectroscopy, and CTPAD suggest a stable, Pd species with a low oxidation state as part of the active site in Pd-exchanged zeolites. Isobutylene was present in the C4 fraction at reasonable quantities for most of the catalyst candidates, especially those containing an alkali metal co-cation.

Phillips, Cory Bernard

1999-11-01

301

Organization of zeolite microcrystals for production of functional materials.  

PubMed

This Account summarizes various methods of organizing zeolite microcrystals into two-dimensional functional entities such as monolayers, multilayers, and patterned monolayers on various substrates and three-dimensional functional entities such as microballs and protein-zeolite composite fibrils. In the case of monolayer assembly, various types of linkages and substrates, factors that govern the rate, degree of coverage, degree of close packing, degree of uniform orientation, and average binding strength between each crystal and the substrate are described. The current and future applications of the organized products are also discussed. PMID:17226943

Yoon, Kyung Byung

2007-01-01

302

Zeolites replacing plant fossils in the Denver formation, Lakewood, Colorado.  

USGS Publications Warehouse

Well-developed crystals of heulandite and stilbite, within fossil wood, occur in sedimentary rocks in Lakewood, Jefferson County. The rocks belong to the Denver formation, a locally fossiliferous deposit of fluvial claystone, siltstone, sandstone and conglomerate, containing some volcanic mudflows (andesitic) of late Cretaceous to Palaeocene age. Altered volcanic glass released Na and Ca into the ground-water and subsequently zeolites were crystallized in the open spaces between grains and within fossil plant structures. Minor pyrite, quartz (jasper), calcite and apatite also occur as replacements of fossil wood. Similar zeolite occurrences in other areas are reviewed.-R.S.M.

Modreski, P.J.; Verbeek, E.R.; Grout, M.A.

1984-01-01

303

Mechanical durability of superhydrophobic and oleophobic copper meshes  

NASA Astrophysics Data System (ADS)

We developed a simple and inexpensive method to prepare the superhydrophobic and oleophobic copper meshes with rough structures fabrication and chemical modification. The achieved surfaces displayed liquid-repellent toward water and several organic liquids (such as hexadecane), which possessed much lower surface tension than that of water. Liquid repellency of the fabricated superhydrophobic copper mesh was demonstrated by visible experiment results and contact angle measurements. Even if the superhydrophobic copper mesh was rolled up, it still kept the superhydrophobicity. The mechanical durability was investigated by finger touch and mechanical abrasion tests. The results indicated that the copper mesh can maintain its superhydrophobicity against an abrasion length of 300 cm under a high pressure (77.2 kPa). The superhydrophobicity and oleophobicity, combined with mechanical durability, would promote the superhydrophobic surface to practical application in industry in the future.

Yin, Linting; Yang, Jin; Tang, Yongcai; Chen, Lin; Liu, Can; Tang, Hua; Li, Changsheng

2014-10-01

304

Effect of crystal size on physical and catalytic properties of ZSM-5 type zeolites  

NASA Astrophysics Data System (ADS)

Diffusion of C6-alkanes in zeolite ZSM-5 and its aluminum free variant silicate-1 receives the greatest attention in the thesis. A physical property of zeolite like the ability to sorb, in particular, nonpolar compounds, was utilized in studying hydrocarbon diffusion by performing adsorption and desorption experiments. The diffusional behavior of the zeolite ZSM-5 and of aluminated silicate-1 at catalytically relevant temperatures was studied by way of a catalytic property of the zeolite. Descriptions of physical studies on nitrogen sorption in ZSM 5 type zeolites and of catalytic studies on the conversion of ethanol to hydrocarbons complete the thesis which tries to give a better understanding of adsorptive, diffusional, and catalytic behavior by describing experiments in which only one parameter has been varied, the zeolite crystal size. Discussions and conclusions are directed towards the industrial application of zeolite ZSM-5, as a catalyst.

Voogd, P.

1991-09-01

305

[Biodegradation and adsorption of bio-zeolite on pyridine and quinoline].  

PubMed

The study was to explore the treatment of pyridine, quinoline and their transformation product, NH(4+) -N, by the biodegradation and adsorption of a natural and a modified bio-zeolites. The experiment results demonstrated that the mixed bacteria on the bio-zeolites, a pyridine-degrading bacterium and a quinoline-degrading bacterium, could degrade pyridine and quinoline simultaneously. The NH(4+) -N transformed from pyridine and quinoline could be adsorbed by the natural and modified zeolites. The adsorption capacity of the modified zeolite was lower than that of the natural zeolite. However, more microorganisms could attach on the surface of the modified zeolite, so the application of the modified bio-zeolite has a better prospect in actual treatment of pyridine and/ or quinoline pollution. PMID:21072937

Bai, Yao-Hui; Sun, Qing-Hua; Xing, Rui; Wen, Dong-Hui; Tang, Xiao-Yan

2010-09-01

306

Zeolite coatings on metal alloys for corrosion resistance, hydrophilicity, and microbiocidal activity  

NASA Astrophysics Data System (ADS)

The recent advent of polycrystalline zeolite coatings on metal alloys has heralded a paradigm shift in zeolitic application and function as well as their requisite synthesis. The prevailing paradigm for zeolite utilization and employment was through the exploitation of their uniform microporosity. We have demonstrated the utility of the non-porous as-synthesized form of high-silica-zeolite (HSZ) MFI coatings on aluminum alloys for corrosion resistance. A single chemical formulation was able to generate excellent corrosion-resistant HSZ MFI coatings on all aluminum alloys studied. Functional zeolite coatings have traditionally been synthesized as coatings comprised of single zeolite species. We have successfully generated functional zeolite hybrid coatings comprised of disparate zeolite species with controlled composition. A three-layer zeolite coating was developed to apply a low-silica-zeolite (LSZ), zeolite Y (ZY), to aluminum substrates. The middle layer was a zeolite hybrid coating of ZY crystals embedded within a MFI matrix. The mixed zeolite middle layer allowed for the adhesion of the single species HSZ MFI bottom layer to the single species LSZ ZY, top layer. A two-layer hydrophilic and antimicrobial hybrid zeolite coating on aluminum alloys was also developed. The base layer was a HSZ MFI coating and the top layer consisted of zeolite A (ZA) crystals embedded within a matrix of HSZ MFI. The ZA crystals are still present at the surface of the hybrid layer, as such; their hydrophilicity is accessible and can be exploited for their hydrophilic and antimicrobial potential. The great utility of the zeolite hybrid layer is realized with the formation of single-layer hybrid coatings on metal alloys. The hybrid coating is made of mixed inorganic crystalline species imbedded in a matrix of HSZ MFI. The inorganic species used is not limited to zeolite types; other inorganic crystalline species can be used. We have generated hybrid coatings made from LSZ ZY and HSZ MR, and hybrid coatings made from hydrotalcite, an inorganic crystalline species distinctly different from zeolite, and HSZ MFI. The single layer hybrid coatings have great utility and their function and application can be easily tuned by changing the zeolite or crystalline inorganic species used to generate them.

Beving, Derek Eugene

307

Copper corrosion issue and analysis on copper damascene process  

Microsoft Academic Search

As semiconductor device features shrink into deep-submicron regime, copper metallization is taking the place of aluminum (Al)-tungsten (W) metallization because of the higher electrical conductivity and electromigration resistance of copper. However, it is very difficult for copper to be etched by dry etching method, thus copper metallization is created with damascene process. In this process, chemical mechanical polishing (CMP) is

Zhigang Song; Soh Ping Neo; Chong Khiam Oh; Shailesh Redkar; Yuan-Ping Lee

2005-01-01

308

The growth of zeolites A, X and mordenite in space  

NASA Technical Reports Server (NTRS)

Zeolites are a class of crystalline aluminosilicate materials that form the backbone of the chemical process industry worldwide. They are used primarily as adsorbents and catalysts and support to a significant extent the positive balance of trade realized by the chemical industry in the United States (around $19 billion in 1991). The magnitude of their efforts can be appreciated when one realizes that since their introduction as 'cracking catalysts' in the early 1960's, they have saved the equivalent of 60 percent of the total oil production from Alaska's North Slope. Thus the performance of zeolite catalysts can have a profound effect on the U.S. economy. It is estimated that a 1 percent increase in yield of the gasoline fraction per barrel of oil would represent a savings of 22 million barrels of crude oil per year, representing a reduction of $400 million in the United States' balance of payments. Thus any activity that results in improvement in zeolite catalyst performance is of significant scientific and industrial interest. In addition, due to their 'stability,' uniformity, and, within limits, their 'engineerable' structures, zeolites are being tested as potential adsorbents to purify gases and liquids at the parts-per-billion levels needed in today's electronic, biomedical, and biotechnology industries and for the environment. Other exotic applications, such as host materials for quantum-confined semiconductor atomic arrays, are also being investigated. Because of the importance of this class of material, extensive efforts have been made to characterize their structures and to understand their nucleation and growth mechanisms, so as to be able to custom-make zeolites for a desired application. To date, both the nucleation mechanics and chemistry (such as what are the 'key' nutrients) are, as yet, still unknown for many, if not all, systems. The problem is compounded because there is usually a 'gel' phase present that is assumed to control the degree of supersaturation, and this gel undergoes a continuous 'polymerization' type reaction during nucleation and growth. Generally, for structure characterization and diffusion studies, which are useful in evaluating zeolites for improving yield in petroleum refining as well as for many of the proposed new applications (e.g., catalytic membranes, molecular electronics, chemical sensors) large zeolites (greater than 100 to 1000 times normal size) with minimum lattice defects are desired. Presently, the lack of understanding of zeolite nucleation and growth precludes the custom design of zeolites for these or other uses. It was hypothesized that the microgravity levels achieved in an orbiting spacecraft could help to isolate the possible effects of natural convection (which affects defect formation) and minimize sedimentation, which occurs since zeolites are twice as dense as the solution from which they are formed. This was expected to promote larger crystals by allowing growing crystals a longer residence time in a high-concentration nutrient field. Thus it was hypothesized that the microgravity environment of Earth orbit would allow the growth of large, more defect-free zeolite crystals in high yield.

Sacco, Albert, Jr.; Bac, N.; Coker, E. N.; Dixon, A. G.; Warzywoda, J.; Thompson, R. W.

1994-01-01

309

Computational studies of polyelectrolytes containing zeolite fragments.  

SciTech Connect

The structures and sodium affinities of a series of zeolitic fragments [H{sub 3}Al(OCH{sub 3}){sub x}(OSiH{sub 3}){sup -}{sub 1-x}, 2T, H{sub 2}Al(OCH{sub 3}){sub x}(OSiH{sub 3}){sup -}{sub 2-x}, 3T, Al(OCH3){sub x}(OSiH{sub 3}){sup -}{sub 4-x}, 5T] that mimic the charge sites in polyelectrolytes are calculated by ab initio molecular orbital methods at different levels of theory. At the HF/6-31G* level, the decrease in the sodium affinity due to the substitution of an OCH{sub 3} group by an OSiH{sub 3} group is about 8 kcal/mol in the 2T and 3T systems. In the 5T systems, the replacement of a sodium-coordinated OCH{sub 3} group by an OSiH{sub 3} group causes a decrease of 7 kcal/mol in the sodium affinity, while the substitution for a non-sodium-coordinated OCH{sub 3} group results in a 2.7 kcal/mol decrease. The lower sodium affinity indicates a weaker Coulombic interaction, suggesting an enhanced ionic conductivity with the substitution of carbon by silicon, consistent with experimental results. Natural bond orbital (NBO) analyses show that silicon-bonded oxygen atoms have smaller lone-pair dipole moments, resulting in a lower sodium affinity. The substitution of aluminum by boron leads to a higher sodium affinity, although the effect of replacing an OCH{sub 3} group by an OSiH{sub 3} group still reduces the sodium affinity. The effect of the sodium cation on the bond angles in these systems is also investigated.

Lee, Y.-C.; Curtiss, L. A.; Ratner, M. A.; Shriver, D. F.; Northwestern Univ.

1999-08-05

310

Computational studies of polyelectrolytes containing zeolitic fragments  

SciTech Connect

The structures and sodium affinities of a series of zeolitic fragments [H{sub 3}Al(OCH{sub 3}){sub x}(OSiH{sub 3}){sub 1{minus}x}{sup {minus}}, 2T, H{sub 2}Al(OCH{sub 3}){sub x}(OSiH{sub 3}){sub 2{minus}x}{sup {minus}}, Al(OCH{sub 3}){sub x}(OSiH{sub 3}){sub 4{minus}x}{sup {minus}}, 5T], that mimic the charge sites in polyelectrolytes are calculated by ab initio molecular orbital methods at different levels of theory. At the HF/6-31G{sup *} level, the decrease in the sodium affinity due to the substitution of an OCH{sub 3} group by an OSiH{sub 3} group is about 8 kcal/mol in the 2T and 3T systems. In the 5T systems, the replacement of a sodium-coordinated OCH{sub 3} group by an OSiH{sub 3} group causes a decrease of 7 kcal/mol in the sodium affinity, while the substitution for a non-sodium-coordinated OCH{sub 3} group results in a 2.7 kcal/mol decrease. The lower sodium affinity indicates a weaker Coulombic interaction, suggesting an enhanced ionic conductivity with the substitution of carbon by silicon, consistent with experimental results. Natural bond orbital (NBO) analyses show that silicon-bonded oxygen atoms have smaller lone-pair dipole moments, resulting in a lower sodium affinity. The substitution of aluminum by boron leads to a higher sodium affinity, although the effect of replacing an OCH{sub 3} group by an OSiH{sub 3} group still reduces the sodium affinity. The effect of the sodium cation on the bond angles in these systems is also investigated.

Lee, Y.C.; Ratner, M.A.; Shriver, D.F. [Northwestern Univ., Evanston, IL (United States)] [Northwestern Univ., Evanston, IL (United States); Curtiss, L.A. [Argonne National Lab., IL (United States). Materials Science Div.] [Argonne National Lab., IL (United States). Materials Science Div.

1999-08-05

311

Characterization of natural chabazite and 5A synthetic zeolites  

Microsoft Academic Search

An investigation was begun to characterize the thermal, outgassing, adsorption, surface areas, and porosity properties of these materials. Samples of Linde and Davison 5A synthetic zeolites were also characterized for comparison purposese. This paper discusses the results of this investigation.

J. L. Stakebake; J. Fritz

1984-01-01

312

Friedel-Crafts Acylation of Aromatic Hydrocarbons Using Zeolites  

Microsoft Academic Search

A convenient heterogeneous catalytic methodology for Friedel-Crafts acylation of benzene and toluene using various aliphatic carboxylic anhydrides over zeolites at 250 °C is described. An interesting para selectivity is observed in the case of acylation of toluene over HZSM-5.

R. Sreekumar; Raghavakaimal Padmakumar

1997-01-01

313

Transport of aromatic molecules in NaY zeolite powders  

SciTech Connect

This paper reports on Xenon-120 NMR that is used to probe macroscopic distributions of aromatic molecules adsorbed in a packed bed of 1-{mu}m NaY zeolite particles. Relative rates of guest transport through the intracrystalline (micro) and intercrystalline (macro) pores play a unique role in the axial distribution of sorbate molecules, such as hexamethylbenzene, in a zeolite powder. Xenon-129 NMR spectra show that a sharp HMB adsorption front advances through a bed of dehydrated NaY crystallites at 523 K. However, at 573 K or in the presence of coadsorbed water, HMB species disperse through the bed without forming a sharp boundary between adsorption zones. When guest transport is controlled by pseudosteady-state diffusion in the macropores, axial penetration of the bed by vapor-phase guest species occurs in a sharp adsorption front. A shrinking-core transport model then quantitatively estimates the intracrystalline diffusivities of HMB in dehydrated and partially hydrated NaY zeolite of 10{sup {minus}11} and 10{sup {minus}13} m{sup 2}/s, respectively, at 523 K. Xenon- 129 NMR proves to be a powerful tool for probing adsorbed guest distribution in zeolites, allowing relative time scales to be established for transport of molecular guests in NaY powders.

Chmelka, B.F.; Gillis, J.V.; Petersen, E.E.; Radke, C.J.

1990-10-01

314

Zeolite formation from coal fly ash and its adsorption potential.  

PubMed

The possibility in converting coal fly ash (CFA) to zeolite was evaluated. CFA samples from the local power plant in Prachinburi province, Thailand, were collected during a 3-month time span to account for the inconsistency of the CFA quality, and it was evident that the deviation of the quality of the raw material did not have significant effects on the synthesis. The zeolite product was found to be type X. The most suitable weight ratio of sodium hydroxide (NaOH) to CFA was approximately 2.25, because this gave reasonably high zeolite yield with good cation exchange capacity (CEC). The silica (Si)-to-aluminum (Al) molar ratio of 4.06 yielded the highest crystallinity level for zeolite X at 79% with a CEC of 240 meq/100 g and a surface area of 325 m2/g. Optimal crystallization temperature and time were 90 degrees C and 4 hr, respectively, which gave the highest CEC of approximately 305 meq/100 g. Yields obtained from all experiments were in the range of 50-72%. PMID:19842322

Ruen-ngam, Duangkamol; Rungsuk, Doungmanee; Apiratikul, Ronbanchob; Pavasant, Prasert

2009-10-01

315

Removal of petroleum products from water using natural sorbent zeolite  

Microsoft Academic Search

An experimental investigation on the removal of petroleum products (PP) from wastewater by natural sorbent zeolite was carried out in a laboratory on a pilot?scaled test bench. The pilot test bench consisted of: a tank in which gasoline (1 portion) and diesel (1 portion) were mixed mechanically with water; a pump for supplying the mixture to a filter model; a

Aušra Mažeikiene; Mindaugas Rimeika; Marina Valentukevi?iene; Vytautas Oškinis; Neringa Paškauskaite; Evelina Brannvall

2005-01-01

316

Acidity of H-Y zeolites: Role of extralattice aluminum  

SciTech Connect

The nature of extralattice aluminum and its effect on acidity in zeolites was studied. A series of zeolites (some commercial), dealuminated by various methods, were obtained having Si/Al ratios between 1.5 and 20. These were characterized using volumetric sorption, XRD, AA, NMR, and reaction studies. Samples dealuminated using ammonium hexafluorosilicate were found to contain little or no extralattice aluminum. In contrast, steam-dealuminated zeolites had large amounts of extralattice aluminum. In some cases a significant portion of the extralattice aluminum was unobservable by [sup 27]Al NMR, suggesting the existence of an aluminum species of low symmetry. Proton NMR indicated that all the protons were associated with the lattice aluminum atoms. Depending on the preparation history, different groups of H-Y zeolites exhibited different maxima in catalytic activity as a function of aluminum content. The maxima in catalytic activity for n-pentane cracking was found to be a function of both lattice and extralattice aluminum contents. 29 refs., 6 figs., 3 tabs.

Shertukde, P.V.; Hall, W.K.; Dereppe, J.M.; Marcelin, G. (Univ. of Pittsburgh, PA (United States))

1993-02-01

317

Synthesis of Na-zeolites from fly ash  

Microsoft Academic Search

The present study focuses on the synthesis of zeolites after fly ash activation, the major objectives being: (a) to study the activation processes; (b) to elucidate the activation conditions for maximum synthesis efficiency; (c) to optimize the conditions for the monomineral synthesis; and (d) to test synthesis efficiencies for different fly ash types. Fly ash was activated by NaOH and

Xavier Querol; Felicià Plana; Andrés Alastuey; Angel López-Soler

1997-01-01

318

Natural Zeolites and Application in Liquid Waste Treatment  

NASA Astrophysics Data System (ADS)

Zeolite-clinoptilolite minerals crystal structures and their main properties are presented depending on property structure relation particular attention is given on irradiated clinoptilolite properties in connection w3ith application for radioactive waste water treatment. It was shown the high effiency for reducing the radioactivity of waters by electron irradiated Armenian clinoptilolite more than 1700 times.

Yeritsyan, H. N.; Sahakyan, A. A.; Harutunyan, V. V.; Nikoghosyan, S. K.; Hakhverdyan, E. A.; Grigoryan, N. E.

319

Electrochemical regeneration of zeolites and the removal of ammonia.  

PubMed

The electrochemical regeneration of zeolites was investigated with the objective of removing ammonia from water harmlessly and reusing the regeneration solution in an undivided electrochemical cell assembled with a Ti/IrO(2)-Pt anode and a Cu/Zn cathode. Zeolites could be completely regenerated through the electrochemical method in this study. With NaCl as a supporting electrolyte, the conversion rate of ammonia adsorbed by the zeolites into nitrogen gas was more that 96%, while the conversion rate to nitrate was less than 4%; no ammonia or nitrite was detected in the solution after electrolysis. The surface of the cathode appeared to be rougher after electrolysis than before. More nitrate was produced when the amount of NaCl was raised or when the current density was increased to the range of 20-60 mA/cm(2). The regeneration solution can be repeatedly reused over a long period of time with the proper amount of NaCl added to the solution. Even after the solution was reused for five times, it could still completely regenerate the zeolites, saving both water resources and the chemical reagent. PMID:19411139

Lei, Xiaohui; Li, Miao; Zhang, Zhenya; Feng, Chuanping; Bai, Wei; Sugiura, Norio

2009-09-30

320

USE OF SYNTHETIC ZEOLITES FOR ARSENATE REMOVAL FROM POLLUTANT WATER  

EPA Science Inventory

Arsenic is known to be a hazardous contaminant in drinking water that causes arsenical dermatitis and skin cancer. In the present work, the potential use of a variety of synthetic zeolites for removal of arsenic from water below the current and proposed EPA MCL has been examined...

321

Highly double selective nitration of nitrostilbenes over zeolite.  

PubMed

A feasible zeolite-assisted ortho C-H nitration of nitrostilbenes has been developed for the first time, which can be used in situ. It uses acetyl nitrate as a mild, easily handled and commercially available nitrating reagent, leading to the synthesis of polynitrostilbenes with double selectivities and in good yields. PMID:25083515

Xu, Jun-Hui; Wei, Jian-Ping; Hao, Zheng; Ma, Qing-Guo; Peng, Xin-Hua

2014-09-21

322

Selective photooxidation of hydrocarbons in zeolites by oxygen  

DOEpatents

A selective photooxidation process for the conversion of hydrocarbon molecules to partially oxygenated derivatives, which comprises the steps of adsorbing a hydrocarbon and oxygen onto a dehydrated zeolite support matrix to form a hydrocarbon-oxygen contact pair, and subsequently exposing the hydrocarbon-oxygen contact pair to visible light, thereby forming a partially oxygenated derivative.

Frei, Heinz (Berkeley, CA); Blatter, Fritz (Berkeley, CA); Sun, Hai (Berkeley, CA)

1998-01-01

323

ADSORPTION AND CATALYTIC DESTRUCTION OF TRICHLOROETHYLENE IN HYDROPHOBIC ZEOLITES  

EPA Science Inventory

Several chromium exchanged ZSM-5 zeolites of varying SiO2/Al2O3 ratio were prepared and investigated for ambient (23 ?C) adsorption and subsequent oxidative destruction (250-400 ?C) of gaseous trichloroethylene (TCE, Cl2C=CHCl) in a humid air stream. With an increase in the SiO2...

324

Fabricating Copper Nanotubes by Electrodeposition  

NASA Technical Reports Server (NTRS)

Copper tubes having diameters between about 100 and about 200 nm have been fabricated by electrodeposition of copper into the pores of alumina nanopore membranes. Copper nanotubes are under consideration as alternatives to copper nanorods and nanowires for applications involving thermal and/or electrical contacts, wherein the greater specific areas of nanotubes could afford lower effective thermal and/or electrical resistivities. Heretofore, copper nanorods and nanowires have been fabricated by a combination of electrodeposition and a conventional expensive lithographic process. The present electrodeposition-based process for fabricating copper nanotubes costs less and enables production of copper nanotubes at greater rate.

Yang, E. H.; Ramsey, Christopher; Bae, Youngsam; Choi, Daniel

2009-01-01

325

Modification of acid sites in ZSM-5 by ion-exchange: An in-situ FTIR study  

NASA Astrophysics Data System (ADS)

A study of the acid sites in Mn+-ZSM-5 zeolites (Mn+ = H+, Al3+, Ca2+, and Ba2+), synthesized by ion-exchange from the NH4+ form, has been carried out using X-ray diffraction, 27Al MAS NMR, and in-situ FTIR spectroscopy. X-ray diffraction data indicate that the crystalline structure of ZSM-5 is maintained on ion-exchange. 27Al MAS NMR spectroscopy confirms that Lewis acid sites in all of the Mn+-ZSM-5 zeolites are mainly located on the tetrahedral aluminum atoms in the zeolite framework. However, octahedral extra-framework aluminum is another source of Lewis acid sites in H+-ZSM-5 and Al3+-ZSM-5. Brønsted acid sites are identified as originating from the hydroxyl groups that bridge Al and Si atoms. The acid sites in Mn+-ZSM-5 have been characterized by in-situ FTIR spectroscopy with pyridine as the probe molecule. FTIR spectroscopy demonstrated that the number of accessible acid sites and ratio of Lewis to Brønsted acid sites in Mn+-ZSM-5 can be effectively modified by ion-exchange. The number of acid sites in Mn+-ZSM-5 increases in the same order as the acidity of cations with Ba2+ < Ca2+ < NH4+ < Al3+ < H+. Though the strength of both Lewis and Brønsted acid sites is virtually identical for all Mn+-ZSM-5 zeolites, the ratio of Brønsted to Lewis acid sites varies as a result of the loaded cation. In addition, modification of acid sites in Mn+-ZMS-5 by loading different cations is discussed in terms of the accessibility of the surface of the zeolite channels and the reactivity of the cations with Brønsted acid hydroxyls. We conclude that larger cations can effectively constrict the zeolite channels and impede the ability of pyridine to access acid sites on the surface of the channels.

Wu, Weiqiang; Weitz, Eric

2014-10-01

326

Shear stress prediction in shock loaded copper  

SciTech Connect

The stress-strain behavior during the shock rise of a 30 kbar and 54 kbar shock in copper is modeled using a plastic constitutive model that includes rate and temperature dependent hardening and accounts for the transition from thermally activated to viscous drag controlled deformation at high strain rates. A slight modification to the treatment of the mobile dislocation density within the model from that originally proposed leads to better agreement with the shock data than achieved previously. The results indicate that the deformation mechanism during the shock rise is a drag mechanism. 9 refs., 4 figs.

Follansbee, P.S.

1991-01-01

327

Exploitation of Unique Properties of Zeolites in the Development of Gas Sensors  

PubMed Central

The unique properties of microporous zeolites, including ion-exchange properties, adsorption, molecular sieving, catalysis, conductivity have been exploited in improving the performance of gas sensors. Zeolites have been employed as physical and chemical filters to improve the sensitivity and selectivity of gas sensors. In addition, direct interaction of gas molecules with the extraframework cations in the nanoconfined space of zeolites has been explored as a basis for developing new impedance-type gas/vapor sensors. In this review, we summarize how these properties of zeolites have been used to develop new sensing paradigms. There is a considerable breadth of transduction processes that have been used for zeolite incorporated sensors, including frequency measurements, optical and the entire gamut of electrochemical measurements. It is clear from the published literature that zeolites provide a route to enhance sensor performance, and it is expected that commercial manifestation of some of the approaches discussed here will take place. The future of zeolite-based sensors will continue to exploit its unique properties and use of other microporous frameworks, including metal organic frameworks. Zeolite composites with electronic materials, including metals will lead to new paradigms in sensing. Use of nano-sized zeolite crystals and zeolite membranes will enhance sensor properties and make possible new routes of miniaturized sensors. PMID:22666081

Zheng, Yangong; Li, Xiaogan; Dutta, Prabir K.

2012-01-01

328

Catalase-like activity studies of the manganese(II) adsorbed zeolites  

NASA Astrophysics Data System (ADS)

Preparation of manganese(II) adsorbed on zeolite 3A, 4A, 5A. AW-300, ammonium Y zeolite, organophilic, molecular sieve and catalase-like enzyme activity of manganese(II) adsorbed zeolites are reported herein. Firstly zeolites are activated at 873 K for two hours before contact manganese(II) ions. In order to observe amount of adsorption, filtration process applied for the solution. The pure zeolites and manganese(II) adsorbed zeolites were analysed by FT-IR. As a result according to the FT-IR spectra, the incorporation of manganese(II) cation into the zeolite structure causes changes in the spectra. These changes are expected particularly in the pseudolattice bands connected with the presence of alumino and silicooxygen tetrahedral rings in the zeolite structure. Furthermore, the catalytic activities of the Mn(II) adsorbed zeolites for the disproportionation of hydrogen peroxide were investigated in the presence of imidazole. The Mn(II) adsorbed zeolites display efficiency in the disproportion reactions of hydrogen peroxide, producing water and dioxygen in catalase-like activity.

?içek, Ekrem; Dede, Bülent

2013-12-01

329

Complexation of porphyrins with silver and zeolite nanoparticles  

NASA Astrophysics Data System (ADS)

It is known that nanoparticles of colloidal silver and zeolites due to the porosity have an extremely large specific surface, which is an order of magnitude increases their sorption capacity. Previously we synthesized a set of water-soluble cationic porphyrins and metalloporphyrins and in the laboratory in vitro had shown their high effectiveness against the various cancer cell lines, and against a variety of microorganisms. The aim of this work was to study of processes sorption/desorption of porphyrins on nanoparticles of silver and zeolites. The interaction of cationic porphyrins with silver nanoparticles of 20 nm diameter was studied in the visible spectrum, in the range 350-800 nm. Investigation of sorption dynamics of porphyrins in the silver nanoparticles using two porphyrins: a) meso-tetra (4-N-butyl pyridyl) porphyrin (TBut4PyP), b) Ag-TBut4PyP, as well as of photosensitizer Al-phthalocyanine was carried out. Analysis of the dynamics of change in the absorption spectra for porphyrins TBut4PyP, Ag-TBut4PyP, Zn-TBut4PyP and Zn-TOEt4PyP by adding of nanoparticles of colloidal silver and zeolites leads to the conclusions: 1. nanoparticles of colloidal silver and zeolites are promising adsorbents for cationic porphyrins (sorption of 55-60% and 90-95%, respectively); 2. sorbents stable long (at least 24 hours) keeps the cationic porphyrins; 3. on nanoparticles of colloidal silver and zeolites an anionic and neutral porphyrins not be adsorbed or adsorbed bad.

Gyulkhandanyan, Anna G.; Ghazaryan, Robert K.; Gasparyan, Vardan K.; Sargsyan, Hakob O.; Madoyan, Roza A.; Gyulkhandanyan, Aram G.; Paronyan, Marina H.; Stasheuski, Alexandr S.; Knyukshto, Valery N.; Dzhagarov, Boris M.; Gyulkhandanyan, Grigor V.

2013-05-01

330

Drinking Water Problems: Copper  

E-print Network

management strategy, consider treating your water or seeking an alternative drink- ing-water supply such as bottled water. Treatment options for reducing copper concentrations in water include (1) reverse osmosis, (2) distillation or (3) ion exchange. Reverse... management strategy, consider treating your water or seeking an alternative drink- ing-water supply such as bottled water. Treatment options for reducing copper concentrations in water include (1) reverse osmosis, (2) distillation or (3) ion exchange. Reverse...

Dozier, Monty; McFarland, Mark L.; Lesikar, Bruce J.

2006-01-25

331

Transport of engineered zeolite and natural nanoparticles in porous media  

NASA Astrophysics Data System (ADS)

There are many natural nanoparticles (NPs) that are ubiquitous in the environment such as soil and sediment colloids. In addition, many new engineered NPs, such as tailored zeolites, are being developed for applications in which they may be released into the environment. The fate and transport of the NPs is very much related with contaminant fate and transport. This study focused on transport of engineered zeolite nanoparticles (NPs) and natural soil and sediment colloidal NPs within porous media under saturated conditions. Clean medium-sized sand grains were used as the porous media and NPs were injected into the column as a pulse. KCl or CaCl2 with varying concentrations was used as background electrolyte. The results showed that, interestingly, the zeta- potential of the natural colloids and Zeolite-Ca decreased (more negative) with increasing KCl concentration while increased (less negative) with increasing CaCl2 concentration. This unexpected results was attributed to the fact that the natural colloids and Zeolite-Ca are saturated with divalent cations (Ca2+ and/or Mg2+) originally and the replacement of these divalent cations with K+ on the colloid surfaces caused the zeta-potential to drop with increasing KCl concentrations. The zeta-potential measurement of Zeolite-K increased with either KCl or CaCl2 concentration. Consistently early breakthrough was observed for NP compared with conservative tracers (KCL or CaCl2) and the effect was more pronounced with higher water flowrate. Zeolite-K showed significantly higher degree of transport (defined as percent of NPs transported out of the column) than Zeolite-Ca under the otherwise same conditions. With KCl as the background electrolyte, the significantly higher NP transport was observed than with CaCl2. Overall, as the ionic strength of the flowing fluid increased, the transport of the NPs decreased, largely due to the compressed double layer under the higher ionic strength. Besides, as the flow rate of the flowing fluid increased, the transport of the NPs increased due to less interaction time between the NPs and the porous media. Analysis of NP transport data showed that Zeolite-Ca fell into the same category as natural colloids while Zeolite-K deviated significantly from the others, suggesting the cations on the cation exchange capacity (CEC) sites play a large role in NP transport. Our results also revealed that the CEC/(surface area) can be a good indicator for predicting relative transport of the NP within the same group. An empirical model was developed to predict NP transport under the experimental conditions. The model parameters include flow rate, ionic strength of the solution, charge density (CEC/surface area). In sum, for the hydrophilic colloids, the chemistry (such as cation species) on the colloids surfaces and flowing fluid is important for predicting their transport in the environment.

Keller, A. A.; Wang, P.

2007-12-01

332

Effects of Surface and Morphological Properties of Zeolite on Impedance Spectroscopy-Based Sensing Performance  

PubMed Central

Measurement by impedance spectroscopy of the changes in intrazeolitic cation motion of pressed pellets of zeolite particles upon adsorption of dimethylmethylphosphonate (DMMP) provides a strategy for sensing DMMP, a commonly used simulant for highly toxic organophosphate nerve agents. In this work, two strategies for improving the impedance spectroscopy based sensing of DMMP on zeolites were investigated. The first one is the use of cerium oxide (CeO2) coated on the zeolite surface to neutralize acidic groups that may cause the decomposition of DMMP, and results in better sensor recovery. The second strategy was to explore the use of zeolite Y membrane. Compared to pressed pellets, the membranes have connected supercages of much longer length scales. The zeolite membranes resulted in higher sensitivity to DMMP, but recovery of the device was significantly slower as compared to pressed zeolite pellets. PMID:23201996

Zhang, Jianwei; Li, Xiaogan; White, Jeremy; Dutta, Prabir K.

2012-01-01

333

Salt-occluded zeolites as an immobilization matrix for chloride waste salt  

SciTech Connect

The pyrometallurgical processing of spent fuel from the integral fast reactor (IFR), an advanced reactor under development at Argonne National Laboratory, will generate a chloride salt waste containing the alkali-metal, alkaline-earth, and some of the rare-earth fission products. Salt-occluded zeolite A, formed by equilibrating simulated molten waste salt and zeolite A, has been investigated as an immobilization matrix for this salt waste. In this concept, the chloride waste salt is loaded into the zeolite cavities, and cesium and strontium from the salt are preferentially sorbed by the zeolite. Experiments showed that the salt occluded zeolite powders are leach resistant and radiation stable. The conclusion is that the salt-occluded zeolite is a promising immobilization matrix for the IFR waste salt.

Lewis, M.A.; Fischer, D.F.; Smith, L.J. (Argonne National Lab., IL (United States). Chemical Technology Div.)

1993-11-01

334

Progress in the remediation of hazardous heavy metal-polluted soils by natural zeolite.  

PubMed

Hazardous heavy metal pollution of soils is an increasingly urgent problem all over the world. The zeolite as a natural amendment has been studied extensively for the remediation of hazardous heavy metal-polluted soils with recycling. But its theory and application dose are not fully clear. This paper reviews the related aspects of theory and application progress for the remediation of hazardous heavy metal-polluted soils by natural zeolite, with special emphasis on single/co-remediation. Based on the comments on hazardous heavy metal behavior characteristics in leaching and rhizosphere and remediation with zeolite for heavy metal-polluted soils, it indicated that the research of rhizosphere should be strengthened. Theory of remediation with natural zeolite could make breakthroughs due to the investigation on synthetic zeolite. Co-remediation with natural zeolite may be applied and studied with more prospect and sustainable recycling. PMID:19464110

Shi, Wei-yu; Shao, Hong-bo; Li, Hua; Shao, Ming-an; Du, Sheng

2009-10-15

335

?-? interaction of aromatic groups in amphiphilic molecules directing for single-crystalline mesostructured zeolite nanosheets  

NASA Astrophysics Data System (ADS)

One of the challenges in material science has been to prepare macro- or mesoporous zeolite. Although examples of their synthesis exist, there is a need for a facile yet versatile approach to such hierarchical structures. Here we report a concept for designing a single quaternary ammonium head amphiphilic template with strong ordered self-assembling ability through ?-? stacking in hydrophobic side, which stabilizes the mesostructure to form single-crystalline mesostructured zeolite nanosheets. The concept is demonstrated for the formation of a new type of MFI (zeolite framework code by International Zeolite Association) nanosheets joined with a 90° rotational boundary, which results in a mesoporous zeolite with highly specific surface area even after calcination. Low binding energies for this self-assembling system are supported by a theoretical analysis. A geometrical matching between the arrangement of aromatic groups and the zeolitic framework is speculated for the formation of single-crystalline MFI nanosheets.

Xu, Dongdong; Ma, Yanhang; Jing, Zhifeng; Han, Lu; Singh, Bhupendra; Feng, Ji; Shen, Xuefeng; Cao, Fenglei; Oleynikov, Peter; Sun, Huai; Terasaki, Osamu; Che, Shunai

2014-06-01

336

Modifications of mitosis  

SciTech Connect

Chapter 15, discusses modifications of mitosis, including endoreduplication, polyteny, endomitosis, C-mitosis, restitution, amitosis and multipolar mitoses. Apart from multipolar mitosis, all other mitotic modifications are characterized by an absent or defective spindle, and in most cases these result in the duplication of the chromosome number. 29 refs., 4 figs.

NONE

1993-12-31

337

Histone onco-modifications  

Microsoft Academic Search

Post-translational modification of histones provides an important regulatory platform for processes such as gene expression, DNA replication and repair, chromosome condensation and segregation and apoptosis. Disruption of these processes has been linked to the multistep process of carcinogenesis. We review the aberrant covalent histone modifications observed in cancer, and discuss how these epigenetic changes, caused by alterations in histone-modifying enzymes,

J Füllgrabe; E Kavanagh; B Joseph

2011-01-01

338

Friedel–Crafts acylation of anisole over hybrid zeolitic-mesostructured materials  

Microsoft Academic Search

The application of hybrid zeolitic-mesostructured materials (HZM) as catalysts in Friedel–Crafts acylation has been investigated and compared with the behaviour of standard ordered mesoporous Al-MCM-41 and nanocrystalline ZSM-5 samples. Hybrid zeolitic-mesoporous samples were prepared from zeolite seeds obtained in different stages of ZSM-5 crystallization by assembling around cetyltrimethyl ammonium bromide (CTAB) micelles to obtain materials having a combination of both

D. P. Serrano; R. A. García; D. Otero

2009-01-01

339

Adsorption of nitrogen oxides by the moisture-saturated zeolites in gas stream  

Microsoft Academic Search

This investigation examined the instantaneous adsorption of NOx by moisture-saturated zeolites at ambient temperature. Among the zeolites studied, Faujasite exhibited the highest adsorption capacity owing to its relatively large pore size. Besides, the influence of cation was demonstrated by comparing the adsorption of zeolites with different cation densities (NaX vs. NaY, mesoporous silica MCM-48-like vs. Faujasite) and treatments (ion exchange

Jing Yang; Ting Ting Zhuang; Feng Wei; Yu Zhou; Yi Cao; Zheng Ying Wu; Jian Hua Zhu; Chuan Liu

2009-01-01

340

Zeolitization of mineral wastes by molten-salt method: NaOH–KNO 3 system  

Microsoft Academic Search

Salt-thermal method exhibits several features such as high production yield, large-scale conversion, low elemental loss, and\\u000a environmentally benign nature. This study has investigated the optimization of the NaOH–KNO3 system for the zeolitization of fly ash and elucidated the characteristics of the resulting zeolitic materials. The following\\u000a are the optimal reaction conditions for zeolitization of fly ash in NaOH–KNO3 system: a

Choong Lyeal Choi; Man Park; Dong Hoon Lee; Sridhar Komarneni; Young Hun Kim; Woo Taik Lim

2007-01-01

341

Role of framework on NH 4NO 3 occlusion in zeolite pores  

Microsoft Academic Search

Salt occlusion in zeolites is a unique phenomenon and plays an important role in solid and molten state reactions. To elucidate its mechanism, the NH4NO3 occlusion was studied with various zeolites that exhibit diversity in pore shape (channel and cavity), window size, and composition and charge of framework. We also attempted to classify NH4NO3 introduced into zeolite pores by characterizing

Man Park; Seung Chan Shin; Choong Lyeal Choi; Dong Hoon Lee; Woo Taik Lim; Sridhar Komarneni; Myung Chul Kim; Jyung Choi; Nam Ho Heo

2001-01-01

342

Conversion of methanol and other O-compounds to hydrocarbons over zeolite catalysts  

Microsoft Academic Search

Experimental data show that Mobil Research and Development Corp.'s new gasoline synthesis from methanol on zeolites of pore dimensions intermediate between faujasites and zeolite A (described in patent literature) gives similar product distributions from methanol, tert.-butanol and 1-heptanol. The shape-selective zeolite produces essentially no hydrocarbons above Cââ, mainly isoparaffins, isoolefins, and methylsubstituted benzenes. Xylenes are produced in equilibrium amounts, but

C. D. Chang; A. J. Silvestri

1977-01-01

343

Pillared MWW zeolites MCM-36 prepared by swelling MCM-22P in concentrated surfactant solutions  

Microsoft Academic Search

Lamellar zeolite forms like layered MCM-22 precursor, MCM-22P, offer unprecedented opportunities for creating diversity of more open zeolite structures prepared post-synthesis by expanding and modifying the interlamellar space. This is a relatively unexplored area with regard to procedures ensuring easy, least destructive and most efficient expansion of layered zeolites. Herein we explore concentrated surfactant solutions with high pH for their

Pavla Chlubná; Wieslaw J. Roth; Arnošt Zukal; Martin Kub?; Jana Pavlatová

344

Preparation and characterization of surface-modified zeolite-polyamide thin film nanocomposite membranes for desalination  

Microsoft Academic Search

NaA type zeolites were surface modified with octadecyltrichlorosilane (OTS) and then added in polyamide layer of thin film composite (TFC) membranes to prepare surface-modified zeolite-polyamide thin film nanocomposite (TFN) membranes for desalination. The zeolites were characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The properties of membranes were characterized by scanning electron microscopy (SEM), contact angle measurement,

Hang Dong; Xin-Ying Qu; Lin Zhang; Li-Hua Cheng; Huan-Lin Chen; Cong-Jie Gao

2011-01-01

345

High capacity cation exchanger by hydrothermal zeolitization of coal fly ash  

Microsoft Academic Search

During; hydrothermal treatment in NaOH medium coal fly ash partially transformed to zeolite P and\\/or hydroxysodalite, while quartz slowly dissolved and mullite remained stable. Residual coal favored the formation of zeolite P. The relative proportion of the two zeolites could be changed by seeding. During fusion of fly ash with NaOH an endothermic reaction at 170–180°C occurred, resulting in formation

V. Berkgaut; A. Singer

1996-01-01

346

ZEOLITE COATING SYSTEM FOR CORROSION CONTROL TO ELIMINATE HEXAVALENT CHROMIUM FROM DOD APPLICATIONS  

Microsoft Academic Search

Zeolites are microporous crystalline aluminosilicates with uniform and molecular sized pores. They are non-toxic and have been explored for medical applications. We have been investigating the application of zeolite films as chromium-free protective coatings on aluminum alloys. We have shown that as-synthesized organic template containing high-silica-zeolite (HSZ) MFI coatings on AA-2024-T3 are non-porous and have excellent corrosion resistance in strong

Derek E. Beving; Cory R. O'Neill; Yushan Yan; Nicole Anderson

347

Zeolite-supported precious metal catalysts for NO x reduction in lean burn engine exhaust  

Microsoft Academic Search

The effects of the zeolite-supported precious metal catalysts on NOx reduction in oxygen-rich exhaust have been investigated. It became clear that NOx conversion related the number of NO adsorption sites of precious metal and the number of HC (C3H6) adsorption of support (zeolite). Pt?Ir?Rh\\/MFI zeolite catalyst showed higher performance and durability than the current Pt?Rh supported on alumina and ceria

A. Takami; T. Takemoto; H. Iwakuni; K. Yamada; M. Shigetsu; K. Komatsu

1997-01-01

348

Characterisation and environmental application of an Australian natural zeolite for basic dye removal from aqueous solution  

Microsoft Academic Search

An Australian natural zeolite was collected, characterised and employed for basic dye adsorption in aqueous solution. The natural zeolite is mainly composed of clinoptiloite, quartz and mordenite and has cation-exchange capacity of 120meq\\/100g. The natural zeolite presents higher adsorption capacity for methylene blue than rhodamine B with the maximal adsorption capacity of 2.8×10?5 and 7.9×10?5mol\\/g at 50°C for rhodamine B

Shaobin Wang; Z. H. Zhu

2006-01-01

349

Antibacterial and anti-adhesive zeolite coatings on titanium alloy surface  

Microsoft Academic Search

To reduce the incidence of peri-implant infections, zeolite coatings on titanium alloy surface have been prepared and their antibacterial as well as anti-adhesive properties were studied. Continuous zeolite A thin films of 1–4?m thickness were coated onto titanium alloy surface through in situ crystallization method under hydrothermal conditions. Small amount of silver ions (ca. 2wt.%) was incorporated into the zeolite

Jincheng Wang; Zhuopeng Wang; Song Guo; Jingyu Zhang; Yang Song; Xiaoming Dong; Xiaonan Wang; Jihong Yu

2011-01-01

350

Silver confined within zeolite EMT nanoparticles: preparation and antibacterial properties  

NASA Astrophysics Data System (ADS)

The preparation of pure zeolite nanocrystals (EMT-type framework) and their silver ion-exchanged (Ag+-EMT) and reduced silver (Ag0-EMT) forms is reported. The template-free zeolite nanocrystals are stabilized in water suspensions and used directly for silver ion-exchange and subsequent chemical reduction under microwave irradiation. The high porosity, low Si/Al ratio, high concentration of sodium and ultrasmall crystal size of the EMT-type zeolite permitted the introduction of a high amount of silver using short ion-exchange times in the range of 2-6 h. The killing efficacy of pure EMT, Ag+-EMT and Ag0-EMT against Escherichia coli was studied semi-quantitatively. The antibacterial activity increased with increasing Ag content for both types of samples (Ag+-EMT and Ag0-EMT). The Ag0-EMT samples show slightly enhanced antimicrobial efficacy compared to that of Ag+-EMT, however, the differences are not substantial and the preparation of Ag nanoparticles is not viable considering the complexity of preparation steps.The preparation of pure zeolite nanocrystals (EMT-type framework) and their silver ion-exchanged (Ag+-EMT) and reduced silver (Ag0-EMT) forms is reported. The template-free zeolite nanocrystals are stabilized in water suspensions and used directly for silver ion-exchange and subsequent chemical reduction under microwave irradiation. The high porosity, low Si/Al ratio, high concentration of sodium and ultrasmall crystal size of the EMT-type zeolite permitted the introduction of a high amount of silver using short ion-exchange times in the range of 2-6 h. The killing efficacy of pure EMT, Ag+-EMT and Ag0-EMT against Escherichia coli was studied semi-quantitatively. The antibacterial activity increased with increasing Ag content for both types of samples (Ag+-EMT and Ag0-EMT). The Ag0-EMT samples show slightly enhanced antimicrobial efficacy compared to that of Ag+-EMT, however, the differences are not substantial and the preparation of Ag nanoparticles is not viable considering the complexity of preparation steps. Electronic supplementary information (ESI) available: Zeta potential data of Ag-EMT suspensions, pore-size distributions and antibacterial data for Ag-EMT 2 h samples. See DOI: 10.1039/c4nr03169e

Dong, B.; Belkhair, S.; Zaarour, M.; Fisher, L.; Verran, J.; Tosheva, L.; Retoux, R.; Gilson, J.-P.; Mintova, S.

2014-08-01

351

Fabrication of silver nanoparticles doped in the zeolite framework and antibacterial activity  

PubMed Central

Using the chemical reduction method, silver nanoparticles (Ag NPs) were effectively synthesized into the zeolite framework in the absence of any heat treatment. Zeolite, silver nitrate, and sodium borohydride were used as an inorganic solid support, a silver precursor, and a chemical reduction agent, respectively. Silver ions were introduced into the porous zeolite lattice by an ion-exchange path. After the reduction process, Ag NPs formed in the zeolite framework, with a mean diameter of about 2.12–3.11 nm. The most favorable experimental condition for the synthesis of Ag/zeolite nanocomposites (NCs) is described in terms of the initial concentration of AgNO3. The Ag/zeolite NCs were characterized by ultraviolet-visible spectroscopy, powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray fluorescence, and Fourier transform infrared. The results show that Ag NPs form a spherical shape with uniform homogeneity in the particle size. The antibacterial activity of Ag NPs in zeolites was investigated against Gram-negative bacteria (ie, Escherichia coli and Shigella dysentriae) and Gram-positive bacteria (ie, Staphylococcus aureus and methicillin-resistant Staphylococcus aureus) by disk diffusion method using Mueller–Hinton agar at different sizes of Ag NPs. All of the synthesized Ag/zeolite NCs were found to have antibacterial activity. These results show that Ag NPs in the zeolite framework can be useful in different biological research and biomedical applications. PMID:21383858

Shameli, Kamyar; Ahmad, Mansor Bin; Zargar, Mohsen; Yunus, Wan Md Zin Wan; Ibrahim, Nor Azowa

2011-01-01

352

Assessing different zeolitic adsorbents for their potential use in Kr and Xe separation  

NASA Astrophysics Data System (ADS)

Separation of Kr from Xe is an important problem in spent nuclear fuel fission gas management. The energy intensive and expensive cryogenic distillation method is currently used to separate these gases. In this thesis, we have carried out the research into appropriate sorbents for the separation of Kr and Xe using pressure swing adsorption. We have examined zeolites using gas adsorption studies as they have the potential to be more cost effective than other sorbents. Zeolites are microporous aluminosilicates and have ordered pore structures. The pores in zeolites have extra-framework cations are substantially free to move. The mobility of cations and the uniformity in pore size permits the separation and removal of gases in zeolites. In our experiment, first, we have measured adsorption isotherms with same zeolitic framework but with different cations. Second, we have measured the adsorption isotherm with different zeolitic frameworks but with same cation. Using these adsorption isotherms, we have calculated the initial heats of adsorption to find out the strength of interaction between the zeolitic framework and the gases. Finally, we have compared the difference in the initial heats of adsorption to find the suitable zeolite that has the highest selectivity of Xe over Kr. In conclusion, we have found out that K LSX seems to have higher potential among the zeolites that we have compared for the separation of Kr from Xe with the differential heats of adsorption for Xe vs Kr as ˜7.4 kJ/mol.

Alagappan, Breetha

353

Improved Catalysts for Heavy Oil Upgrading Based on Zeolite Y Nanoparticles Encapsulated Stable Nanoporous Host  

SciTech Connect

The objective of this project is to synthesize nanocrystals of highly acidic zeolite Y nanoclusters, encapsulate them within the channels of mesoporous (nanoporous) silicates or nanoporous organosilicates, and evaluate the 'zeolite Y/Nanoporous host' composites as catalysts for the upgrading of heavy petroleum feedstocks. In comparison to conventionally-used zeolite Y catalysts of micron size particles, the nanocrystals (< 100 nm particle size) which contain shorter path lengths, are expected to allow faster diffusion of large hydrocarbon substrates and the catalysis products within and out of the zeolite's channels and cages (<1 nm size). This is expected to significantly reduce deactivation of the catalyst and to prolong their period of reactivity. Encapsulating zeolite Y nanocrystals within the nanoporous materials is expected to protect its external surfaces and pore entrances from being blocked by large hydrocarbon substrates, since these substrates will initially be converted to small molecules by the nanoporous host (a catalyst in its own right). The project consisted of four major tasks as follows: (1) synthesis of the nanoparticles of zeolite Y (of various chemical compositions) using various techniques such as the addition of organic additives to conventional zeolite Y synthesis mixtures to suppress zeolite Y crystal growth; (2) synthesis of nanoporous silicate host materials of up to 30 nm pore diameter, using poly (alkylene oxide) copolymers which when removed will yield a mesoporous material; (3) synthesis of zeolite Y/Nanoporous Host composite materials as potential catalysts; and (4) evaluation of the catalyst for the upgrading of heavy petroleum feedstocks.

Conrad Ingram; Mark Mitchell

2007-09-30

354

Application of zeolites for radium removal from mine water.  

PubMed

For removal of radium from saline waters in Upper Silesian mines, several methods of purification have been developed. The most efficient one is based on application of barium chloride, which was implemented in full technical scale in two Polish coal mines several years ago. Very good results of purification have been achieved-the removal efficiency exceeding 95% of the initial activity. Another possibility for the removal of different ions from salty waters and brines is the application of zeolites. We found that technique as a very promising method for removal of not only radium isotopes from mine waters but also other ions (barium, iron, manganese). Treatment of several various water samples has been done to assess the removal efficiency for natural radionuclides. Preliminary results show very good effects for radium isotopes as well as for barium ions. In the paper, a short description of laboratory results of the purification of mine waters with application of synthetic zeolites is presented. PMID:23881589

Cha?upnik, Stanis?aw; Franus, Wojciech; Wysocka, Ma?gorzata; Gzyl, Grzegorz

2013-11-01

355

Kinetics of oxidation of coke deposits on zeolitic cracking catalyst  

SciTech Connect

The widespread introduction of zeolitic cracking catalysts into commercial practice and the use of heavy feedstocks have created a need for further improvements in the efficiency of oxidative regeneration of coked catalysts. In order to develop new and highly efficient regeneration processes, data must be available on the kinetics of coke burnoff from the surface of zeolitic catalysts at 570-700/sup 0/C. Experimental studies were performed in a micropilot unit that included a spherical quartz reactor with a vibrofluidized catalyst bed. The free volume of the reactor was 30 cm/sup 3/. The gas compositions at the reactor inlet and outlet were determined chromatographically. In these studies they used methods based on the application of gradientless and differential reactors. The main advantage of these methods is in the direct determination of reaction rates.

Solyar, B.Z.; Zhitomirskii, B.M.; Melik-Akhnazarov, T.K.; Terekhov, N.I.

1987-07-01

356

Fission product removal from molten salt using zeolite  

SciTech Connect

Spent nuclear fuel (SNF) can be treated in a molten salt electrorefiner for conversion into metal and mineral waste forms for geologic disposal. The fuel is dissolved in molten chloride salt. Non-transuranic fission products in the molten salt are ion-exchanged into zeolite A, which is subsequently mixed with glass and consolidated. Zeolite was found to be effective in removing fission product cations from the molten salt. Breakthrough of cesium and the alkaline earths occurred more rapidly than was observed for the rare earths. The effluent composition as a function of time is presented, as well as results for the distribution of fission products along the length of the column. Effects of temperature and salt flow rate are also discussed.

Pereira, C.; Babcock, B.D.

1996-10-01

357

Inelastic X-ray Scattering Studies of Zeolite Collapse  

SciTech Connect

In situ inelastic x-ray scattering (IXS) experiments have been used to probe heterogeneity and deformability in zeolte Y as this thermally collapses to a high density amorphous (HDA) aluminosilicate phase. The Landau-Placzek ratio R{sub LP} falls slowly as amorphisation advances, increasing in the later stages of collapse clearly showing how homogeneity improves non-linearly--behaviour linked closely with the decline in molar volume V{sub Molar}. The Brillouin frequency {omega}{sub Q} also decreases with amorphisation in a similar fashion, signifying a non-uniform decrease in the speed of sound v{sub l}. All of these changes with zeolite amorphisation infer formation of an intermediate low density amorphous (LDA) phase. This low entropy or 'perfect glass' has mechanical properties which are closer to the zeolite rather to the HDA glass--notably a very small value of Poisson's Ratio signifying unusually low resistance to deformation.

Greaves, G. Neville; Kargl, Florian; Ward, David [Centre for Advanced Functional Materials and Devices, Institute of Mathematics and Physics, Aberystwyth University, Aberystwyth SY23 3BZ (United Kingdom); Holliman, Peter [Centre for Advanced Functional Materials and Devices, College of Physical and Applied Sciences, Bangor University, Bangor LL57 2UW (United Kingdom); Meneau, Florian [Centre for Advanced Functional Materials and Devices, SOLEIL, Orme des Merisiers, Batiment A, Saint Aubin, BP 48, 91192, Gif sur Yvette Cedex (France)

2009-01-29

358

Copper and copper-nickel alloys as zebra mussel antifoulants  

SciTech Connect

Copper has been used in the marine environment for decades as cladding on ships and pipes to prevent biofouling by marine mussels (Mytilus edulis L.). This motivated the present investigation into the possibility of using copper to prevent biofouling in freshwater by both zebra mussels and quagga mussels (Dreissena polymorpha and D. bugensis collectively referred to as zebra mussels). Copper and copper alloy sheet proved to be highly effective in preventing biofouling by zebra mussels over a three-year period. Further studies were conducted with copper and copper-nickel mesh (lattice of expanded metal) and screen (woven wire with a smaller hole size), which reduced the amount of copper used. Copper screen was also found to be strongly biofouling-resistant with respect to zebra mussels, while copper mesh reduced zebra mussel biofouling in comparison to controls, but did not prevent it entirely. Preliminary investigations into the mechanism of copper antifouling, using galvanic couples, indicated that the release of copper ions from the surface of the exposed metal into the surrounding water is directly or indirectly responsible for the biofouling resistance of copper.

Dormon, J.M.; Cottrell, C.M.; Allen, D.G.; Ackerman, J.D.; Spelt, J.K. [Univ. of Toronto, Ontario (Canada)

1996-04-01

359

Purification of metal electroplating waste waters using zeolites  

Microsoft Academic Search

The sorption behaviour of natural (clinoptilolite) and synthetic (NaP1) zeolites has been studied with respect to Cr(III), Ni(II), Zn(II), Cu(II) and Cd(II) in order to consider its application to purify metal finishing waste waters. The batch method has been employed using metal concentrations in solution ranged from 10 to 200mg\\/l and solid\\/liquid ratios ranged from 2.5 to 10g\\/l. The Langmuir

E Álvarez-Ayuso; A Garc??a-Sánchez; X Querol

2003-01-01

360

Hydrogenation properties of ruthenium sulfide clusters in acidic zeolites  

SciTech Connect

Catalysts of ruthenium sulfide, dispersed in a series of Y zeolites with various acidic properties, were prepared by ion exchange and subsequent sulfidation. The activities for the reactions of hydrogenation of tetralin and toluene, carried out in the presence of H{sub 2}S (1.9%), vary widely according to the nature of the zeolites. Ruthenium sulfide catalysts are much more active when using acidic zeolite, HY and HYd (dealuminated), and a partially potassium-exchanged KHYd sample, than when using the KY support. The acidic properties of the sulfided RuY catalysts were determined in situ using infrared spectroscopy and the conversion of isooctane. Both methods gave similar rankings of catalyst acidity. The electronic properties of the ruthenium sulfide phase were examined by means of the infrared study of the adsorption of CO. A low-frequency shift of 15 cm{sup -1} was observed for CO adsorbed on RuKY by reference to CO adsorbed on all other samples. The increase in activity for the hydrogenation of aromatics is related to the electron- deficient character of the sulfide particles in the acidic zeolites; as has been proposed, in the literature, for metal catalysts. A superimposed influence of the acidic sites on the adsorption of the aromatic molecule may also occur which could explain the amplitude of the effect (difference of activity between the most and less active catalysts {approximately}200 times) and the variations of activity observed within the series of the acidic catalysts. 33 refs., 10 figs., 7 tabs.

Breysse, M.; Cattenot, M.; Kougionas, V. [Institut de Recherches sur la Catalyse, Villeurbanne (France)] [and others] [Institut de Recherches sur la Catalyse, Villeurbanne (France); and others

1997-06-01

361

Thorium and uranium uptake by natural zeolitic materials  

Microsoft Academic Search

The thorium and uranium uptake from their aqueous solutions by unpretreated and NaCl-pretreated zeolite-bearing volcanoclastic rock samples from Metaxades (Thrace, Greece) has been studied using a batch-type method. The concentration of the solutions varied between 50 and 20 000 mg\\/l. The NaCl pretreatment of the materials improved the thorium but not the uranium uptake. The absolute thorium uptake by the

P. Misaelides; A. Godelitsas; A. Filippidis; D. Charistos; I. Anousis

1995-01-01

362

Photosensitization of europium ions by silver clusters in zeolite  

NASA Astrophysics Data System (ADS)

Photosensitization of europium (Eu) ions by silver (Ag) clusters was achieved by simultaneously doping Eu and Ag in zeolite cages. The photoluminescence (PL) due to the D?F transition of Eu ions at 613 nm is significantly increased by the presence of Ag clusters. The excitation wavelength dependence of the PL intensity coincided well with the absorption spectrum of Ag clusters, indicating that Eu ions are excited by the energy transfer from Ag clusters.

Rong gui, Sa chu; Imakita, Kenji; Fujii, Minoru; Hayashi, Shinji

2014-03-01

363

Copper alloys for industrial hardware  

SciTech Connect

Copper and its alloys are widely used because of their excellent electrical and thermal conductivities, outstanding resistance to corrosion, and ease of fabrication. Lifecycle costs are another important reason for new and expanding applications for copper and copper alloys. For example, lifecycle cost analyses favor the use of copper-nickel for automotive brake tubes, and copper alloys in molds for plastic parts. However, copper also competes very well on a first-cost basis in the brazed copper-and-brass radiator, and in free-cutting brass machined components. This article highlights four specific applications in which advanced copper alloys and fabrication techniques enhance the performance of industrial hardware, based largely on conductivity, corrosion resistance, and lifecycle costs.

Peters, D.T. [Copper Development Association Inc., New York, NY (United States)

1996-10-01

364

Synthetic zeolites and other microporous oxide molecular sieves  

PubMed Central

Use of synthetic zeolites and other microporous oxides since 1950 has improved insulated windows, automobile air-conditioning, refrigerators, air brakes on trucks, laundry detergents, etc. Their large internal pore volumes, molecular-size pores, regularity of crystal structures, and the diverse framework chemical compositions allow “tailoring” of structure and properties. Thus, highly active and selective catalysts as well as adsorbents and ion exchangers with high capacities and selectivities were developed. In the petroleum refining and petrochemical industries, zeolites have made possible cheaper and lead-free gasoline, higher performance and lower-cost synthetic fibers and plastics, and many improvements in process efficiency and quality and in performance. Zeolites also help protect the environment by improving energy efficiency, reducing automobile exhaust and other emissions, cleaning up hazardous wastes (including the Three Mile Island nuclear power plant and other radioactive wastes), and, as specially tailored desiccants, facilitating the substitution of new refrigerants for the ozone-depleting chlorofluorocarbons banned by the Montreal Protocol. PMID:10097059

Sherman, John D.

1999-01-01

365

Design of zeolite ion-exchange columns for wastewater treatment  

SciTech Connect

Oak Ridge National Laboratory plans to use chabazite zeolites for decontamination of wastewater containing parts-per-billion levels of {sup 90}Sr and {sup 137}Cs. Treatability studies indicate that such zeolites can remove trace amounts of {sup 90}Sr and {sup 137}Cs from wastewater containing high concentrations of calcium and magnesium. These studies who that zeolite system efficiency is dependent on column design and operating conditions. Previous results with bench-scale, pilot-scale, and near-full-scale columns indicate that optimized design of full-scale columns could reduce the volume of spent solids generation by one-half. The data indicate that shortcut scale-up methods cannot be used to design columns to minimize secondary waste generation. Since the secondary waste generation rate is a primary influence on process cost effectiveness, a predictive mathematical model for column design is being developed. Equilibrium models and mass-transfer mechanisms are being experimentally determined for isothermal multicomponent ion exchange (Ca, Mg, Na, Cs, and Sr). Mathematical models of these data to determine the breakthrough curves for different column configurations and operating conditions will be used to optimize the final design of full-scale treatment plant. 32 refs., 6 figs., 3 tabs.

Robinson, S.M.; Arnold, W.D.; Byers, C.H.

1991-01-01

366

Skeletal isomerization of 1-butene on MCM-22 zeolite catalyst  

SciTech Connect

The skeletal isomerization of 1-butene has been studied on two MCM-22 zeolite catalysts synthesized with different Si/Al ratios, i.e., 15 and 47, under a wide range of operating conditions. Product yields are a function of n-butene conversion, and a maximum of isobutene yield is found at ca. 50% conversion. Besides isobutene, propylene and pentanes, which are formed by dimerization-cracking reactions products. Isobutene also takes part, together with the n-butenes, in the formation of by-products thorough dimerization and/or codimerization processes, which would also lead to a lower isobutene selectivity. Moreover, the yield of isobutene increases with increasing reaction temperature and decreasing 1-butene partial pressure, while the contrary holds for the formation of by-products. On the basis of these results the mechanism of formation of isobutene and the different by-products on MCM-22 is discussed. Finally, the selectivity to isobutene is strongly improved by increasing the Si/Al ratio of the zeolite, which is explained by a decrease of the undesired consecutive reactions when decreasing the density of Broensted acid sites of the zeolite. 24 refs., 6 figs., 6 tabs.

Asensi, M.A.; Corma, A.; Martinez, A. [Universidad Politecnica de Valencia (Spain)] [Universidad Politecnica de Valencia (Spain)

1996-02-01

367

Purification of metal electroplating waste waters using zeolites.  

PubMed

The sorption behaviour of natural (clinoptilolite) and synthetic (NaP1) zeolites has been studied with respect to Cr(III), Ni(II), Zn(II), Cu(II) and Cd(II) in order to consider its application to purify metal finishing waste waters. The batch method has been employed using metal concentrations in solution ranged from 10 to 200 mg/l and solid/liquid ratios ranged from 2.5 to 10 g/l. The Langmuir model was found to describe well all sorption processes, allowing to establish metal sorption sequences from which the main retention mechanism involved for each metal has been inferred. Synthetic zeolite exhibited about 10 times greater sorption capacities (b(Cr)=0.838 mmol/g, b(Ni)=0.342 mmol/g, b(Zn)=0.499 mmol/g, b(Cu)=0.795 mmol/g, b(Cd)=0.452 mmol/g) than natural zeolite (b(Cr)=0.079 mmol/g, b(Ni)=0.034 mmol/g, b(Zn)=0.053 mmol/g, b(Cu)=0.093 mmol/g, b(Cd)=0.041 mmol/g), appearing, therefore, as most suitable to perform metal waste water purification processes. This mineral showed the same high sorption capacity values when used in the purification of metal electroplating waste waters. PMID:14604631

Alvarez-Ayuso, E; García-Sánchez, A; Querol, X

2003-12-01

368

Correlations for adsorption of oxygenates onto zeolites from aqueous solutions.  

PubMed

Henry's constants (K(ads)) for adsorption of C(3) polyfunctional molecules onto zeolites from aqueous solutions at 278 K were obtained and compared with the octanol-water partition coefficients, K(ow), which were calculated using the prevalent ClogP group contribution method. K(ads) increases linearly with K(ow) for these adsorbates on H-ZSM-5 (MFI), FAU, BEA, and ITQ-1 (MWW). K(ads) values for C(2)-C(6) diol adsorption at 278 K are also linearly correlated with K(ow) regardless of interactions in the bulk phase as measured by the solution activity coefficient. Exceptions to the correlation established between K(ads) and K(ow) are the adsorption of 1,2,?-triols with carbon number greater than three on H-ZSM-5 and adsorption of all oxygenates studied on FER, which we postulate to be due to the effect of changing adsorption configuration with adsorbate/zeolite structure which cannot be captured by K(ow) alone. These results enable the prediction of separation selectivities of biomass-derived compounds on zeolite adsorbents. PMID:21916446

Mallon, Elizabeth E; Babineau, Ian J; Kranz, Joshua I; Guefrachi, Yasmine; Siepmann, J Ilja; Bhan, Aditya; Tsapatsis, Michael

2011-10-01

369

CO2 adsorption in amine-grafted zeolite 13X  

NASA Astrophysics Data System (ADS)

The adsorption of CO2 on Zeolite 13X functionalized with amino groups was studied. Adsorbent functionalization was carried out by grafting with different loads of monoethanolamine (MEA). The adsorbents were characterized by N2 adsorption/desorption isotherms at 77 K, x-ray diffraction, TGA, in situ FTIR, XPS and adsorption microcalorimetry. CO2 isotherms were studied in a gravimetric device up to 10 bar at 298 and 348 K. It was found that increasing loads of amine to the adsorbent tend to reduce micropore volume of the resulting adsorbents by pore blocking with MEA. There is experimental evidence that part of the loaded MEA is effectively covalently bonded to the zeolitic structure, whereas there is also physisorbed excess MEA which will eventually be desorbed by raising the temperature beyond MEA boiling point. Heats of adsorption at nearly zero coverage indicate that some of the adsorbed CO2 reacts with available amino groups, which agrees with the finding that the adsorption capacity increases with increasing temperature for the modified zeolite with the highest MEA load.

Bezerra, Diôgo P.; Silva, Francisco W. M. da; Moura, Pedro A. S. de; Sousa, Allyson G. S.; Vieira, Rodrigo S.; Rodriguez-Castellon, Enrique; Azevedo, Diana C. S.

2014-09-01

370

Silver confined within zeolite EMT nanoparticles: preparation and antibacterial properties.  

PubMed

The preparation of pure zeolite nanocrystals (EMT-type framework) and their silver ion-exchanged (Ag(+)-EMT) and reduced silver (Ag(0)-EMT) forms is reported. The template-free zeolite nanocrystals are stabilized in water suspensions and used directly for silver ion-exchange and subsequent chemical reduction under microwave irradiation. The high porosity, low Si/Al ratio, high concentration of sodium and ultrasmall crystal size of the EMT-type zeolite permitted the introduction of a high amount of silver using short ion-exchange times in the range of 2-6 h. The killing efficacy of pure EMT, Ag(+)-EMT and Ag(0)-EMT against Escherichia coli was studied semi-quantitatively. The antibacterial activity increased with increasing Ag content for both types of samples (Ag(+)-EMT and Ag(0)-EMT). The Ag(0)-EMT samples show slightly enhanced antimicrobial efficacy compared to that of Ag(+)-EMT, however, the differences are not substantial and the preparation of Ag nanoparticles is not viable considering the complexity of preparation steps. PMID:25117582

Dong, B; Belkhair, S; Zaarour, M; Fisher, L; Verran, J; Tosheva, L; Retoux, R; Gilson, J-P; Mintova, S

2014-09-21

371

Mesopore quality determines the lifetime of hierarchically structured zeolite catalysts  

NASA Astrophysics Data System (ADS)

Deactivation due to coking limits the lifetime of zeolite catalysts in the production of chemicals and fuels. Superior performance can be achieved through hierarchically structuring the zeolite porosity, yet no relation has been established between the mesopore architecture and the catalyst lifetime. Here we introduce a top-down demetallation strategy to locate mesopores in different regions of MFI-type crystals with identical bulk porous and acidic properties. In contrast, well-established bottom-up strategies as carbon templating and seed silanization fail to yield materials with matching characteristics. Advanced characterization tools capable of accurately discriminating the mesopore size, distribution and connectivity are applied to corroborate the concept of mesopore quality. Positron annihilation lifetime spectroscopy proves powerful to quantify the global connectivity of the intracrystalline pore network, which, as demonstrated in the conversions of methanol or of propanal to hydrocarbons, is closely linked to the lifetime of zeolite catalysts. The findings emphasize the need to aptly tailor hierarchical materials for maximal catalytic advantage.

Milina, Maria; Mitchell, Sharon; Crivelli, Paolo; Cooke, David; Pérez-Ramírez, Javier

2014-05-01

372

Synthetic zeolites and other microporous oxide molecular sieves.  

PubMed

Use of synthetic zeolites and other microporous oxides since 1950 has improved insulated windows, automobile air-conditioning, refrigerators, air brakes on trucks, laundry detergents, etc. Their large internal pore volumes, molecular-size pores, regularity of crystal structures, and the diverse framework chemical compositions allow "tailoring" of structure and properties. Thus, highly active and selective catalysts as well as adsorbents and ion exchangers with high capacities and selectivities were developed. In the petroleum refining and petrochemical industries, zeolites have made possible cheaper and lead-free gasoline, higher performance and lower-cost synthetic fibers and plastics, and many improvements in process efficiency and quality and in performance. Zeolites also help protect the environment by improving energy efficiency, reducing automobile exhaust and other emissions, cleaning up hazardous wastes (including the Three Mile Island nuclear power plant and other radioactive wastes), and, as specially tailored desiccants, facilitating the substitution of new refrigerants for the ozone-depleting chlorofluorocarbons banned by the Montreal Protocol. PMID:10097059

Sherman, J D

1999-03-30

373

Competitive adsorption of dyes and heavy metals on zeolitic structures.  

PubMed

The adsorption of Acid blue 25, basic blue 9, basic violet 3, Pb(2+), Ni(2+), Zn(2+) and Cd(2+) ions has been studied in single and dye-metal binary solutions using two mineral materials: Clinoptilolite (CL) and ER (Erionite). These zeolites were characterized by FT-IR spectroscopy; potentiometric titration and nitrogen adsorption isotherms at 77 K to obtain their textural parameters. Results indicated that ER has an acidic character and a high specific surface (401 m(2) g(-1)) in contrast with the zeolite CL (21 m(2) g(-1)). Surprisingly, the removal of dyes was very similar for the two zeolites and they showed a considerable selectivity by the basic dyes in comparison with the acid dyes. In the case of heavy metals, ER was more effective in the adsorption process showing a selectivity of: Pb(2+) > Ni(2+) > Zn(2+) > Cd(2+). In the multicomponent adsorption experiments an antagonistic effect was observed in the removal of basic dyes and heavy metals. Particularly, the adsorbed amount of basic violet 3 decreased more significantly when the heavy metals are presents in contrast with the basic blue 9. PMID:23321372

Hernández-Montoya, V; Pérez-Cruz, M A; Mendoza-Castillo, D I; Moreno-Virgen, M R; Bonilla-Petriciolet, A

2013-02-15

374

The mineralogy of copper electrorefining  

NASA Astrophysics Data System (ADS)

The impurities in copper anodes occur both in solid solution in the copper metal matrix and in discrete inclusions at the copper grain boundaries. During electrorefining, all the impurities undergo extensive chemical and/or morphological changes. These changes impact significantly on anode passivation, cathode quality, electrolyte purification and, of course, the subsequent recovery of by-products from the anode slimes. Recently, mineralogical studies have been undertaken to characterize the various impurities and elucidate their transformations during copper electrorefining.

Chen, T. T.; Dutrizac, J. E.

1990-08-01

375

Friedel–Crafts acylation of anisole and toluene with acetic anhydride over nano-sized Beta zeolites  

Microsoft Academic Search

Nano-sized Beta zeolites, with a crystal size of 80–100 nm, were synthesized via surface wet method. The nano-sized HBeta\\u000a zeolites exhibit much higher activity and stability in the Friedel–Crafts acylation of anisole and toluene with acetic anhydride\\u000a than the conventional zeolites of large particle size. The small crystal size of nano-sized zeolites may bring on more accessible\\u000a active sites and then

Xiangfei Ji; Zhangfeng Qin; Mei Dong; Guofu Wang; Tao Dou; Jianguo Wang

2007-01-01

376

Energetic behavior of the pure silica ITQ-12 (ITW) zeolite under high pressure water intrusion.  

PubMed

Experimental water intrusion-extrusion isotherms were obtained at room temperature on pure silica ITW-type zeolites (ITQ-12 zeosil). The water intrusion is obtained by applying a high hydraulic pressure corresponding to the intrusion step. When the pressure is released, the water extrusion occurs at a similar pressure to that of the intrusion one. Therefore, the "ITW zeosil-water" system behaves like a spring and the phenomenon is reproducible over several cycles. Several characterization techniques have been performed before and after water intrusion-extrusion experiments in order to reveal the presence or the lack of defects after such experiments. Structural modifications at the long range order cannot be observed by XRD analysis after three water intrusion-extrusion cycles. However, solid state NMR spectroscopy provides evidence of the presence of Q3 groups revealing the breaking of some siloxane bridges after the intrusion step. The "ITW zeosil-water" system can restore 100% of the stored energy corresponding to about 8 J g(-1). PMID:24169538

Khay, Ismail; Tzanis, Lydie; Daou, T Jean; Nouali, Habiba; Ryzhikov, Andrey; Patarin, Joël

2013-12-14

377

Tyrosine Modifications in Aging  

E-print Network

must continue, especially given the expanding list of known modifications. Emerging approaches, such as genetic and metabolic incorporation of unnatural amino acids, hold promise for additional focused studies of this kind. Antioxid. Redox Signal. 17...

Feeney, Maria B.; Schö neich, Christian

2012-12-01

378

Notes on Behavior Modification.  

ERIC Educational Resources Information Center

The author reviews three topics featured in his first Behavior Modification column: pupil management, social validation, and nondiscriminatory testing. Two new topics are also discussed: data and decisions, and program evaluation. (Author)

Lovitt, Thomas C.

1981-01-01

379

High adherence copper plating process  

SciTech Connect

A process is described for applying copper to a substrate of aluminum or steel by electrodeposition and for preparing an aluminum or steel substrate for electrodeposition of copper. Practice of the invention provides good adhesion of the copper layer to the substrate.

Mignardot, H.

1992-12-31

380

SOURCES OF COPPER AIR EMISSIONS  

EPA Science Inventory

The report gives results of a study to update estimates of atmospheric emissions of copper and copper compounds in the U.S. Source categories evaluated included: metallic minerals, primary copper smelters, iron and steel making, combustion, municipal incineration, secondary coppe...

381

High adherence copper plating process  

DOEpatents

A process is described for applying copper to a substrate of aluminum or steel by electrodeposition and for preparing the surface of an aluminum or steel substrate for the electrodeposition of copper. Practice of the invention provides good adhesion of the copper layer to either substrate.

Nignardot, H.

1993-09-21

382

Migration of copper and some other metals from copper tableware  

SciTech Connect

Intake of heavy metals is an important problem in human health. Certain heavy metals are avoided with regard to their use for utensils or tableware coming into contact with food, although copper is widely used in food processing factories or at home. The use of copper products for the processing, cooking or serving of foods and beverages is considered to be a cause of a copper contamination. Although copper is essential element, its excess ingestion is undesirable. In this study, the migration of copper from tin-plated or non-plated copperware under several experimental conditions was investigated using food-simulating solvents.

Ishiwata, H.; Inoue, T.; Yoshihira, K.

1986-11-01

383

Brazing copper to dispersion-strengthened copper  

SciTech Connect

The Advanced Photon Source (APS) is a state-of-the-art synchrotron light source that will produce intense x-ray beams, which will allow the study of smaller samples and faster reactions and processes at a greater level of detail that has been possible to date. The beam is produced by using third-generation insertion devices in a 7 GeV electron/positron storage ring that is 1100 meters in circumference. The heat load from these intense high power devices is very high and certain components must sustain total heat loads of 3 to 15 kW and heat fluxes of 30 W/mm{sup 2}. Because the beams will cycle on and off many times, thermal shock and fatigue will be a problem. High heat flux impinging on a small area causes a large thermal gradient that results in high stress. GlidCop{reg_sign}, a dispersion strengthened copper, is the desired material because of its high thermal conductivity and superior mechanical properties as compared to copper and its alloys. GlidCop is not amenable to joining by fusion welding, and brazing requires diligence because of high diffusivity. Brazing procedures were developed using optical and scanning electron microscopy.

Ryding, D.G.; Allen, D.; Lee, R.

1996-08-01

384

Tyrosine Modifications in Aging  

PubMed Central

Abstract Significance: The understanding of physiological and pathological processes involving protein oxidation, particularly under conditions of aging and oxidative stress, can be aided by proteomic identification of proteins that accumulate oxidative post-translational modifications only if these detected modifications are connected to functional consequences. The modification of tyrosine (Tyr) residues can elicit significant changes in protein structure and function, which, in some cases, may contribute to biological aging and age-related pathologies, such as atherosclerosis, neurodegeneration, and cataracts. Recent Advances: Studies characterizing proteins in which Tyr has been modified to 3-nitrotyrosine, 3,4-dihydroxyphenylalanine, 3,3?-dityrosine and other cross-links, or 3-chlorotyrosine are reviewed, with an emphasis on structural and functional consequences. Critical Issues: Distinguishing between inconsequential modifications and functionally significant ones requires careful biochemical and biophysical analysis of target proteins, as well as innovative methods for isolating the effects of the multiple modifications that often occur under oxidizing conditions. Future Directions: The labor-intensive task of isolating and characterizing individual modified proteins must continue, especially given the expanding list of known modifications. Emerging approaches, such as genetic and metabolic incorporation of unnatural amino acids, hold promise for additional focused studies of this kind. Antioxid. Redox Signal. 17, 1571–1579. PMID:22424390

Feeney, Maria B.

2012-01-01

385

Synthesis of ZSM-5 zeolite from expanded perlite\\/kaolin and its catalytic performance for FCC naphtha aromatization  

Microsoft Academic Search

A hydrothermal synthesis method for ZSM-5 preparation was investigated by using expanded perlite (or kaolin) as the only alumina source. The ZSM-5 zeolites from the expanded perlite (or kaolin) have a distinctive pore systems which were a combination of a medium pore ZSM-5 zeolite and a large pore matrix perlite (or kaolin). The ZSM-5 zeolites from the expanded perlite (or

Ping Wang; Baojian Shen; Dongdong Shen; Tong Peng; Jinsen Gao

2007-01-01

386

Comparative study of the initial surface absorption and chloride diffusion of high performance zeolite, silica fume and PFA concretes  

Microsoft Academic Search

Zeolite, a type of natural pozzolanic material, has been used in producing blended cement and concrete in China. The purpose of this study is to evaluate the effectiveness of zeolite in enhancing the performance of concrete in comparison with silica fume and pulverized fuel ash (PFA). In the first series of experiments, zeolite, silica fume, and PFA were all used

Sammy Y. N Chan; Xihuang Ji

1999-01-01

387

Human Rights and Behavior Modification  

ERIC Educational Resources Information Center

Criticisms of behavior modification, which charge that it violates ethical and legal principles, are discussed and reasons are presented to explain behavior modification's susceptibility to attack. (GW)

Roos, Philip

1974-01-01

388

High-temperature decomposition of solid solutions of beta-tantalum with copper in films  

NASA Astrophysics Data System (ADS)

Using high-temperature X-ray diffractometry and electron microprobe analysis decomposition of alloys of beta-tantalum with copper produced by codeposition of sputtered ultradisperse particles of tantalum and copper has been established. At a temperature of 900°C, the precipitation of copper from the solid solution into an individual phase starts, and its diffusion onto the film surface with the formation of globular particles and simultaneous transition of the matrix ?-modification into ?-tantalum. The suggested mechanism of decomposition of solid solutions includes the following stages: the precipitation of copper into an individual phase, its diffusion onto the surface because of lattice pressure and the concentration gradient inside and outside the tantalum matrix, the coalescence of nanosized formations into drops at the coating surface, and the subsequent evaporation of copper from them in a vacuum.

Tuleushev, Yu. Zh.; Volodin, V. N.; Zhakanbaev, E. A.

2014-05-01

389

Earth's anthrobiogeochemical copper cycle  

Microsoft Academic Search

An “anthrobiogeochemical” copper cycle, from Earth's core to the Moon, combining natural biogeochemical and human anthropogenic stocks and flows is derived for the mid-1990s. Although some aspects of the quantification have moderate to high uncertainty, the anthropogenic mining, manufacturing, and use flows (on the order of 104 Gg Cu\\/yr) clearly dominate the cycle. In contrast, the natural repositories of Earth's

J. N. Rauch; T. E. Graedel

2007-01-01

390

Hydrogen Transport in Copper  

SciTech Connect

Hydrogen interaction with oxygen in copper exerts a significant influence on the apparent hydrogen diffusivity and the quantity of hydrogen absorbed. Correlation of the amount of absorbed tritium with oxygen content and dependence of permeation transients on both oxygen content and prior treatment indicate that both reversible and irreversible interactions occur between hydrogen and dissolved oxygen. This paper discusses results of that study.

Caskey, G.R. Jr.

2001-10-23

391

Interaction of Dimethylmethylphosphonate with Zeolite Y: Impedance-Based Sensor for Detecting Nerve Agent Simulants  

E-print Network

Interaction of Dimethylmethylphosphonate with Zeolite Y: Impedance-Based Sensor for Detecting Nerve Dimethylmethylphosphonate (DMMP) is a simulant for the highly toxic organophosphate nerve agent Sarin (GB). The influence of 3000 Hz allows for the use of Na+ -exchanged zeolite Y as a sensor for detecting ppm level of DMMP

Dutta, Prabir K.

392

Carbon dioxide capture utilizing zeolites synthesized with paper sludge and scrap-glass.  

PubMed

The present work introduces the study of the CO2 capture process by zeolites synthesized from paper sludge and scrap glass. Zeolites ZSM-5, analcime and wairakite were produced by means of two types of Structure Directing Agents (SDA): tetrapropilamonium (TPA) and ethanol. On the one hand, zeolite ZSM-5 was synthesized using TPA; on the other hand, analcime and wairakite were produced with ethanol. The temperature programmed desorption (TPD) technique was performed for determining the CO2 sorption capacity of these zeolites at two sorption temperatures: 50 and 100°C. CO2 sorption capacity of zeolite ZSM-5 synthesized at 50°C was 0.683 mmol/g representing 38.2% of the value measured for a zeolite ZSM-5 commercial. Zeolite analcime showed a higher CO2 sorption capacity (1.698 mmol/g) at 50°C and its regeneration temperature was relatively low. Zeolites synthesized in this study can be used in the purification of biogas and this will produce energy without increasing the atmospheric CO2 concentrations. PMID:25398410

Espejel-Ayala, F; Corella, R Chora; Pérez, A Morales; Pérez-Hernández, R; Ramírez-Zamora, Rm

2014-12-01

393

Conversion of oil shale ash into zeolite for cadmium and lead removal from wastewater  

Microsoft Academic Search

A by-product fly ash from oil shale processing was converted into zeolite by alkali hydrothermal activation using sodium hydroxide. The activation was performed at different activation temperatures using 8 M sodium hydroxide. The obtained cation exchange capacity (CEC) showed that the best condition for synthesis of zeolite performed in a closed reactor at 160 °C for 24 h. Powder patterns

Reyad Shawabkeh; Adnan Al-Harahsheh; Malik Hami; Abdelaziz Khlaifat

2004-01-01

394

Zeolite with tunable intracrystal mesoporosity synthesized with carbon aerogel as a secondary template  

Microsoft Academic Search

In this paper, carbon aerogel was investigated as a potential template for generating size controllable intracrystal mesopore system in zeolite. For this purpose zeolite samples were synthesized with carbon aerogels having different structural parameters as secondary template, and characterized with XRD, FT-IR, SEM, TEM as well as low-temperature nitrogen adsorption. Results indicated that the carbon aerogel synthesized by simple ambient

Yunming Fang; Haoquan Hu; Guohua Chen

2008-01-01

395

Theoretical Simulation of n-Alkane Cracking on Zeolites Joseph A. Swisher,,|  

E-print Network

Theoretical Simulation of n-Alkane Cracking on Zeolites Joseph A. Swisher,,| Niels Hansen,,| Theo of alkane cracking in zeolites MFI and FAU have been simulated theoretically from first principles. The apparent rate coefficient for alkane cracking was described as the product of the number of alkane

Bell, Alexis

396

Dual templating function of Equisetum arvense in the preparation of zeolite macrostructures  

Microsoft Academic Search

Biomimetic microporous structures were prepared by in situ laboratory zeolitization of a silica-rich plant, member of the Equisetophyta family. Leaves and stems of the dry plant were subjected to hydrothermal treatment into a clear ZSM-5 precursor solution. Highly reactive biomorphic silica deposited at the epidermal surface of the plant successfully promoted zeolite growth and provided composites containing up to 70

V. Valtchev; M. Smaihi; A. C. Faust; L. Vidal

2004-01-01

397

Water sorption in faujasite- and chabazite type zeolites of varying lattice composition for heat storage applications  

Microsoft Academic Search

The water sorption properties of faujasite type zeolites with different Si\\/Al ratios as well as of natural chabazite and two different SAPO-34 molecular sieves have been investigated systematically by thermogravimetry (TG), differential scanning calorimetry (DSC), microcalorimetry, and isotherm measurements. Via changing the lattice chemistry of the zeolites by dealumination and isomorphous substitution of T atoms the energetics of the water

Jochen Jänchen; Helmut Stach; Udo Hellwig

2008-01-01

398

Removal of Boron from Aqueous Solutions by Adsorption Using Fly Ash, Zeolite, and Demineralized Lignite  

Microsoft Academic Search

In the present study for the purpose of removal of boron from water by adsorption using adsorbents like fly ash, natural zeolite, and demineralized lignite was investigated. Boron in water was removed with fly ash, zeolite, and demineralized lignite with different capacities. Ninety-four percent boron was removed using fly ash. Batch experiments were conducted to test the removal capacity, to

Seren Yüksel; Yuda Yürüm

2009-01-01

399

Pillared MFI zeolite nanosheets of a single-unit-cell thickness.  

PubMed

Zeolite MFI nanosheets of 2-nm thickness have been hydrothermally synthesized via cooperative assembly between silica and an organic surfactant, which is functionalized with a diquaternary ammonium group. The zeolite nanosheets have been further assembled into their ordered multilamellar mesostructure through hydrophobic interactions between the surfactant tails located outside the zeolite nanosheet. This assembly process involves successive transformations from an initially hexagonal mesophase to a multilamellar mesophase without crystallinity and then to a lamellar mesophase with a crystalline zeolite framework. The mesopore volume in the interlamellar space could be retained by supporting the zeolite nanosheets with silica pillars, as in pillared clays, even after surfactant removal by calcination. The mesopore diameters could be controlled according to the surfactant tail lengths. Due to the interlamellar structural coherence, the hierarchically mesoporous/microporous zeolite could exhibit small-angle X-ray diffraction peaks up to the fourth-order reflections corresponding to the interlayer distance. In addition, an Ar adsorption analysis and transmission electron microscopic investigation indicated that the pillars were highly likely to be built with an MFI structure. The present approach using a zeolite structure-directing functional group contained in a surfactant would be suitable for the synthesis of other related nanomorphous zeolites in the future. PMID:20136135

Na, Kyungsu; Choi, Minkee; Park, Woojin; Sakamoto, Yasuhiro; Terasaki, Osamu; Ryoo, Ryong

2010-03-31

400

A Novel Route to Zeolite-Templated ZnO Quantum Wires  

Microsoft Academic Search

ZnO nanoparticles were synthesised within the pores of the zeolite ferrierite (FER) by a novel molten salt impregnation method and compared to a traditional wet impregnation method. The structure and optical properties were characterised by powder XRD, photoluminescence and UV-visible diffuse reflectance spectroscopy. The XRD results reveal a distinct difference in the effect of the impregnation method on the zeolite

G. J. Baker; F. F. Ouali; G. B. Hix

2010-01-01

401

Removal of humic acid from aqueous solution by cetylpyridinium bromide modified zeolite.  

PubMed

Natural zeolite was modified by loading cetylpyridinium bromide (CPB) to create more efficient sites for humic acid (HA) adsorption. The natural and CPB modified zeolites were characterized with X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and elemental analysis. The effects of various experimental parameters such as contact time, initial HA concentration, solution pH and coexistent Ca2+, upon HA adsorption onto CPB modified zeolites were evaluated. The results showed that natural zeolite had negligible affinity for HA in aqueous solutions, but CPB modified zeolites exhibited high adsorption efficiency for HA. A higher CPB loading on natural zeolites exhibited a larger HA adsorption capacity. Acidic pH and coexistent Ca2+ were proved to be favorable for HA adsorption onto CPB modified zeolite. The kinetic process was well described by pseudo second-order model. The experimental isotherm data fitted well to Langmuir and Sips models. The maximum monolayer adsorption capacity of CPB modified zeolite with surfactant bilayer coverage was found to be 92.0 mg/g. PMID:21174962

Zhan, Yanhui; Zhu, Zhiliang; Lin, Jianwei; Qiu, Yanling; Zhao, Jianfu

2010-01-01

402

Effects of preparation and experimental conditions on removal of phenol by surfactant-modified zeolites.  

PubMed

The removal of phenol from aqueous solutions using surfactant-modified clinoptilolite-rich tuffs (SMZ) prepared from two Mexican zeolitic tuffs (Chihuahua and Oaxaca) was investigated. Sodium homoionization of the zeolitic rocks was performed before they were modified with the surfactants: hexadecyltrimethylammonium chloride or bromide and bencylcetildimethylammonium chloride. The surfactants in the modified zeolitic materials were determined considering the total carbon in the samples. The phenol removal was determined in a batch system taking into consideration the different quantities of surfactants in the zeolitic tuffs, contact time, pH and initial phenol concentration. The phenol was determined in the aqueous solutions by UV/Vis spectroscopy. Results showed that the formation of a hemimicelle or admicelle on the zeolites depended on the initial surfactant concentration and they were responsible for the type of interactions between the phenol and the surfactant-modified zeolites. Phenol adsorption by the surfactant-modified zeolites was carried out in approximately three hours. Phenol adsorption data was best adjusted to the pseudo-second order kinetic model. Both, surface properties of the surfactant-modified zeolites and pH of solution play an important role in the removal of this pollutant from aqueous solutions and they are responsible for the type of mechanism involved. PMID:18975855

Díaz-Nava, C; Olguín, M T; Solache-Ríos, M; Alarcón-Herrera, M T; Aguilar-Elguezabal, A

2008-11-01

403

Zeolite Salt Occlusion: A Potential Route for the Immobilisation of Iodine-129? Neil C. Hyatt,1*  

E-print Network

Zeolite ­ Salt Occlusion: A Potential Route for the Immobilisation of Iodine-129? Neil C. Hyatt,1 examined as possible starting routes to the long term immobilisation of iodine-129. Heating the salts, where the iodide salt migrates into the zeolite pores. Detailed studies of the Na-A / 5AgI complex

Sheffield, University of

404

NMR and X-ray Study Revealing the Rigidity of Zeolitic Imidazolate William Morris,  

E-print Network

NMR and X-ray Study Revealing the Rigidity of Zeolitic Imidazolate Frameworks William Morris and Graduate School of EEWS (WCU), Korea *S Supporting Information ABSTRACT: NMR relaxation studies and aluminum oxygen units in zeolites. ZIFs are of great interest for numerous applications including gas

Yaghi, Omar M.

405

Experimental investigation of a solid adsorption chiller based on a heat exchanger coated with hydrophobic zeolite  

Microsoft Academic Search

In this paper, the experimental results of a lab scale adsorption chiller working with hydrophobic Y zeolite–methanol are presented and discussed. The main feature of this chiller is the innovative adsorbent bed consisting of a shell and tube heat exchanger in which the finned tubes are coated with a zeolite layer. In this way, the interesting sorption properties of the

G. Restuccia; A. Freni; F. Russo; S. Vasta

2005-01-01

406

On the effective thermal conductivity of wetted zeolite under the working conditions of an adsorption chiller  

Microsoft Academic Search

This paper presents a theoretical model for predicting the effective thermal conductivity of wetted zeolite. The model comprises the thermal conductivities of the zeolite crystal as well as of the adsorbed water. The temperature dependence of both thermal conductivities is considered. Moreover, the contribution to the effective thermal conductivity due to vapor conductance is also taken into account. The effective

B. Dawoud; M. Imroz Sohel; A. Freni; S. Vasta; G. Restuccia

2011-01-01

407

A mesostructured Y zeolite as a superior FCC catalyst--lab to refinery.  

PubMed

A mesostructured Y zeolite was prepared by a surfactant-templated process at the commercial scale and tested in a refinery, showing superior hydrothermal stability and catalytic cracking selectivity, which demonstrates, for the first time, the promising future of mesoporous zeolites in large scale industrial applications. PMID:22945549

García-Martínez, Javier; Li, Kunhao; Krishnaiah, Gautham

2012-12-18

408

Skeletal isomerization of n-butylenes to isobutylene on boron-beta zeolites  

SciTech Connect

A process is described for producing iso-olefins which comprises contacting a feedstock comprising at least one n-olefin with a catalyst comprising a boron-beta zeolite containing sufficient boron to provide sufficient acidity in said zeolite to catalyze the structural isomerization of said n-alkene to iso-alkenes.

O'Young, C.; Hazen, J.; Casey, D.G.

1993-07-13

409

A two-step process for the synthesis of zeolites from coal fly ash  

Microsoft Academic Search

The conversion of fly ash into zeolites by incubation of the fly ash with alkaline solutions is a well known process which, however, usually results in a zeolitic product which still contains significant amounts of residual fly ash. Presented here is a method by which part of the silicon in fly ash can be used for the synthesis of a

G. G Hollman; G Steenbruggen; M Janssen-Jurkovi?ová

1999-01-01

410

Synthesis of a novel zeolite through a pressure-induced reconstructive phase transition process.  

PubMed

The first pressure-induced solid-phase synthesis of a zeolite has been found through compression of a common zeolite, ITQ-29 (see scheme, Si yellow, O red). The new microporous structure, ITQ-50, has a unique structure and improved performance for propene/propane separation with respect the parent material ITQ-29. PMID:23913399

Jordá, Jose L; Rey, Fernando; Sastre, German; Valencia, Susana; Palomino, Miguel; Corma, Avelino; Segura, Alfredo; Errandonea, Daniel; Lacomba, Raúl; Manjón, Francisco J; Gomis, Óscar; Kleppe, Annette K; Jephcoat, Andrew P; Amboage, Mónica; Rodríguez-Velamazán, J Alberto

2013-09-27

411

Pure silica ITQ-32 zeolite allows separation of linear olefins from paraffins.  

PubMed

ITQ-32 is able to separate propene from propane and represents a clear improvement with respect to previous zeolites in achieving the separation of trans-2-butene and 1-butene from the C(4) fraction using only one zeolite. PMID:17356766

Palomino, Miguel; Cantín, Angel; Corma, Avelino; Leiva, Sandra; Rey, Fernando; Valencia, Susana

2007-03-28

412

Use of Jordanian natural zeolite as sorbent for removal of cadmium from aqueous solutions  

Microsoft Academic Search

This study considers Jordanian zeolite as adsorbent for the removal of cadmium from aqueous solution. Zeolite collected from a geographic zone in Jordan valley was assesses for its ability to adsorb heavy metal after preliminary treatment. Kinetics and equilibrium of cadmium uptake by this new adsorbent were followed in this investigation. The experimental results showed that the adsorption of Cd

Mamdouh Allawzi; Sameer Al-Asheh

2010-01-01

413

The authigenic zeolites of the Aritayn Volcaniclastic Formation, north-east Jordan  

Microsoft Academic Search

In the Aritayn Volcaniclastic Formation, the formation of zeolites is associated with the transformation of sideromelane into palagonite by reaction with percolating water in an open hydrological system. Three vertical zones are described, characterised by fresh sideromelane at the top (zone 1), palagonite-smectite in the middle (zone 2), and zeolites at the bottom (zone 3). Within zone 3, a phillipsite-chabazite

K. Ibrahim; A. Hall

1996-01-01

414

A comparison of basic dye adsorption onto zeolitic materials synthesized from fly ash  

Microsoft Academic Search

This investigation reveals the adsorption characteristics of two basic dyes, thionine (TH) and safranine T (ST), onto fly ash (FA) and its three zeolitized products prepared at different hydrothermal conditions. Typical two-step isotherms were observed for TH adsorption onto four adsorbents, whereas the isotherms of the larger ST molecules were S-shaped. The adsorption capacities of the zeolitized fly ash (ZFA)

Gülten Atun; Gül Hisarl?; Ay?e Engin Kurto?lu; Nihat Ayar

2011-01-01

415

ZEOLITE STRUCTURE ANALYSIS WITH POWDER X-RAY DIFFRACTION AND SOLID-STATE NMR TECHNIQUES  

Microsoft Academic Search

Large advances in the development of catalytic materials were made with the synthesis of zeolites, which are porous crystalline materials that can be used as catalysts, catalyst supports, sorbents and ion exchangers. Zeolite structures consist of T-atoms tetrahedrally coordinated to oxygen atoms, where T can be AI, Si, or any other element capable of isomorphous substitution for Si. The unavailability

G. T. KOKOTAILO; C. A. FYFE

416

Experiments for the Undergraduate Laboratory that Illustrate the Size-Exclusion Properties of Zeolite Molecular Sieves  

ERIC Educational Resources Information Center

Experiments are presented that demonstrate the size-exclusion properties of zeolites and reveal the reason for naming zeolites "molecular sieves". If an IR spectrometer is available, the adsorption or exclusion of alcohols of varying sizes from dichloromethane or chloroform solutions can be readily demonstrated by monitoring changes in the…

Cooke, Jason; Henderson, Eric J.

2009-01-01

417

Presenilin Promotes Dietary Copper Uptake  

PubMed Central

Dietary copper is essential for multicellular organisms. Copper is redox active and required as a cofactor for enzymes such as the antioxidant Superoxide Dismutase 1 (SOD1). Copper dyshomeostasis has been implicated in Alzheimer’s disease. Mutations in the presenilin genes encoding PS1 and PS2 are major causes of early-onset familial Alzheimer’s disease. PS1 and PS2 are required for efficient copper uptake in mammalian systems. Here we demonstrate a conserved role for presenilin in dietary copper uptake in the fly Drosophila melanogaster. Ubiquitous RNA interference-mediated knockdown of the single Drosophila presenilin (PSN) gene is lethal. However, PSN knockdown in the midgut produces viable flies. These flies have reduced copper levels and are more tolerant to excess dietary copper. Expression of a copper-responsive EYFP construct was also lower in the midgut of these larvae, indicative of reduced dietary copper uptake. SOD activity was reduced by midgut PSN knockdown, and these flies were sensitive to the superoxide-inducing chemical paraquat. These data support presenilin being needed for dietary copper uptake in the gut and so impacting on SOD activity and tolerance to oxidative stress. These results are consistent with previous studies of mammalian presenilins, supporting a conserved role for these proteins in mediating copper uptake. PMID:23667524

Southon, Adam; Greenough, Mark A.; Ganio, George; Bush, Ashley I.; Burke, Richard; Camakaris, James

2013-01-01

418

The development of a zeolite system for upgrade of the Process Waste Treatment Plant  

SciTech Connect

Studies have been undertaken to design an efficient zeolite ion exchange system for use at the ORNL Process Waste Treatment Plant to remove cesium and strontium to meet discharge limits. This report focuses on two areas: (1) design of column hardware and pretreatment steps needed to eliminate column plugging and channeling and (2) development of equilibrium models for the wastewater system. Results indicate that zeolite columns do not plug as quickly when the wastewater equalization is performed in the new Bethel Valley Storage Tanks instead of the former equalization basin where suspended solids concentration is high. A down-flow column with spent zeolite was used successfully as a prefilter to prevent plugging of the zeolite columns being used to remove strontium and cesium. Equilibrium studies indicate that a Langmuir isotherm models binary zeolite equilibrium data while the modified Dubinin-Polyani model predicts multicomponent data.

Robinson, S.M.; Kent, T.E.; Arnold, W.D.; Parrott, J.R. Jr.

1993-10-01

419

Performance of a zeolite column system in removing fission products from molten salt  

SciTech Connect

Spent nuclear fuel is dissolved in molten chloride salt and treated in a molten salt electrorefiner for conversion into metal and mineral waste forms for geologic disposal. Non-TRU fission products in the molten salt are removed by ion-exchange in a continuous process using a zeolite column system. The salt-loaded zeolite is subsequently mixed with glass and consolidated. The zeolite was effective at removing fission products from the molten salt. Cesium was removed relatively rapidly; alkaline earths and rare earths were more strongly held by the zeolite, but the rate of exchange was much slower. Four parameters were varied during these tests: type of zeolite used, temperature, flow rate, and composition of the salt. The effects of these parameters on the effluent composition and on the distribution of fission products along the length of the column are presented and discussed. Results are used to test a computer model of the system.

Babcock, B.; Pereira, C.; Hutter, J. [Argonne National Lab., IL (United States)

1996-10-01

420

Gas phase synthesis of MTBE from methanol and isobutene over dealuminated zeolites  

SciTech Connect

Gas phase synthesis of MTBE from methanol and isobutene has been investigated over different zeolites. It is shown that bulk Si/Al ratio has a marked influence on the formation of MTBE. H-beta zeolite was found to be as active as acid Amberlyst-15 (reference catalyst), and noticeably superior to non- and dealuminated forms of H-Y, H-ZSM-5, zeolite omega, and H-mordenites. Screening test results obtained over other catalysts (SAPOs and pillared clays) are briefly commented. The contribution of the external surface of the zeolites to the reaction is discussed. In the case of H-Y zeolites, it is shown that extra framework Al species ({sup 27}Al NMR signal at 30 ppm) have a detrimental effect on the reaction. 64 refs., 12 figs., 3 tabs.

Collignon, F.; Mariani, M.; Moreno, S.; Remy, M.; Poncelet, G. [Universite Catholique de Louvain (Belgium)] [Universite Catholique de Louvain (Belgium)

1997-02-01

421

Acid zeolites as alcohol racemization catalysts: screening and application in biphasic dynamic kinetic resolution.  

PubMed

Acid zeolites were screened as heterogeneous catalysts for racemization of benzylic alcohols. The most promising zeolites appeared to be H-Beta zeolites, for which the optimal reaction conditions were studied in further detail. The zeolite performance was compared to that of homogeneous acids and acid resins under similar reaction conditions. In a second part of the research, H-Beta zeolites were applied in dynamic kinetic resolution (DKR) of 1-phenylethanol, which was conducted by means of a two-phase approach and which resulted in yields smoothly crossing the 50% border up to 90%, with an enantiomeric excess of >99%. To explore the applicability of this biphasic methodology, several other substrates were examined in the standard racemization reaction and in the biphasic dynamic kinetic resolution. PMID:15565578

Wuyts, S; De Temmerman, K; De Vos, D E; Jacobs, P A

2004-12-17

422

Investigations of adsorbed organic molecules in Na-Y zeolite by xenon-129 NMR  

SciTech Connect

The adsorption of n-hexane, benzene, and trimethylbenzene in Na-Y zeolite supercages has been investigated by use of xenon-129 NMR. As shown by Fraissard and co-workers, xenon-129 is an excellent probe of its environment in zeolites and is sensitive to the number of adsorbed guest molecules. The xenon-129 chemical shift, when extrapolated to zero effective xenon pressure, is 89.7 {plus minus} 0.1 ppm for benzene, 89.0 {plus minus} 1.3 ppm for trimethylbenzene, and 107.7 {plus minus} 1.2 ppm for n-hexane at a concentration of two guest molecules per zeolite supercage compared to 58.9 {plus minus} 0.5 ppm for empty Na-Y zeolite supercages. This approach is useful for determining the number of adsorbed molecules inside zeolite supercages and given information about their arrangement within the supercages.

de Menorval, L.C.; Raftery, D.; Liu, S.B.; Takegoshi, K.; Ryoo, R.; Pines, A. (Lawrence Berkeley Lab., CA (USA))

1990-01-11

423

In situ studies of zeolite syntheses using powder diffraction methods: Crystallization of ``instant zeolite A`` powder and CoAPO-5  

SciTech Connect

A series of hydrothermal zeolite synthesis were performed on a powder diffractometer using synchrotron radiation and a position sensitive detector. Direct observation of the induction period (nucleation stage), crystallization and transformation of zeolite 4A (Na-LTA) was possible due to the intense X-ray beam which allows fast data collection. High pressure experiments were performed, allowing observation of hydrothermal synthesis of a cobalt substituted AlPO{sub 4}-zeolite, CoAPO-5, up to 165{degrees}C. The temperature dependence of crystallization rates of CoAPO-5 was studied. This is to our knowledge the first time resolved powder diffraction studies of zeolite syntheses using angle dispersive synchrotron powder diffraction.

Norby, P. [Odense Univ. (Denmark). Dept. of Chemistry; Christensen, A.N. [Aarhus Univ. (Denmark). Dept. of Chemistry; Hanson, J.C. [Brookhaven National Lab., Upton, NY (United States)

1994-02-01

424

Experimental Investigation of the Effect Of Zeolite Coating Thickness on the Performance of a Novel Zeolite-Water Adsorption Heat Pump Module  

E-print Network

A novel zeolite-water absorption heat pump module comprising an adsorber, an evaporator and a condenser heat exchanger as well as a module non-return valve in a hermetically sealed vessel is introduced. The investigated adsorber heat exchanger...

Dawoud, B.; Hofle, P.; Chmielewski, S.

2010-01-01

425

Modifications of gravity.  

PubMed

General relativity (GR) is a phenomenologically successful theory that rests on firm foundations, but has not been tested on cosmological scales. The deep mystery of dark energy (and possibly even the requirement of cold dark matter (CDM)) has increased the need for testing modifications to GR, as the inference of such otherwise undetected fluids depends crucially on the theory of gravity. Here, I discuss a general scheme for constructing consistent and covariant modifications to the Einstein equations. This framework is such that there is a clear connection between the modification and the underlying field content that produces it. I argue that this is mandatory for distinguishing modifications of gravity from conventional fluids. I give a non-trivial example, a simple metric-based modification of the fluctuation equations for which the background is exact ?CDM, but differs from it in the perturbations. I show how this can be generalized and solved in terms of two arbitrary functions. Finally, I discuss future prospects and directions of research. PMID:22084286

Skordis, Constantinos

2011-12-28

426

Recommended nomenclature for zeolite minerals: report of the subcommittee on zeolites of the International Mineralogical Association, Commission of New Minerals and Mineral Names  

USGS Publications Warehouse

This report embodies recommendations on zeolite nomenclature approved by the International Mineralogical Association Commission of New Minerals and Mineral Names. In a working definition of a zeolite mineral used for review, interrupted tetrahedral framework structures are accepted where other zeolitic properties prevail, and complete substitution by elements other than Si and Al is allowed. Separate species are recognized in topologically distinctive compositional series in which different extra-framework cations are the most abundance in atomic proportions. To name these, the appropriate chemical symbol is attached by a hyphen to the series name as a suffix except for the names harmotome, pollucite and wairakite in the phillipsite and analcime series. Differences in space-group symmetry and in order-disorder relationships in zeolites having the same topologically distinctive framework do not in general provide adequate grounds for recognition of separate species. Zeolite species are not to be distinguished solely on Si:Al ratio except for heulandite (Si:Al < 4.0) and clinoptilolite (Si:Al ??? 4.0). Dehydration, partial hydration, and over-hydration are not sufficient grounds for the recognition of separate species of zeolites. Use of the term 'ideal formula' should be avoided in referring to a simplified or averaged formula of a zeolite. Newly recognized species in compositional series are as follows: brewsterite-Sr.-Ba: chabazite-Ca.-Na.-K; clinoptilolite-K, -Na, -Ca: dachiardite-Ca, -Na; erionite-K, -Ca: faujasite-Na, -Ca, -Na: paulingite-K. -Ca; phillipsite-Na, -Ca, -Ka; stilbite-Ca, -Na. Key references, type locality, origin of name, chemical data. IZA structure-type symbols, space-group symmetry; unit-cell dimensions, and comments on structure are listed for 13 compositional series, 82 accepted zeolite mineral species, and three of doubtful status. Herschelite, leonhardite, svetlozarite, and wellsite are discredited as mineral species names. Obsolete and discredited names are listed.

Coombs, D.S.; Alberti, A.; Armbruster, T.; Artioli, G.; Colella, C.; Galli, E.; Grice, J.D.; Liebau, F.; Mandarino, J.A.; Minato, H.; Nickel, E.H.; Passaglia, E.; Peacor, D.R.; Quartieri, S.; Rinaldi, R.; Ross, M.; Sheppard, R.A.; Tillmanns, E.; Vezzalini, G.

1998-01-01

427

Social Aspects of Weather Modification  

Microsoft Academic Search

A description of the social context and citizen response to three weather modification projects provides an introduction to the discussion of a variety of social and economic issues related to planned weather modification. Various interest groups have markedly different perspectives on weather modification. Most persons subject to the consequences of weather modification have no opportunity to participate in the associated

J. Eugene Haas

1973-01-01

428

Selective chemical protein modification.  

PubMed

Chemical modification of proteins is an important tool for probing natural systems, creating therapeutic conjugates and generating novel protein constructs. Site-selective reactions require exquisite control over both chemo- and regioselectivity, under ambient, aqueous conditions. There are now various methods for achieving selective modification of both natural and unnatural amino acids--each with merits and limitations--providing a 'toolkit' that until 20 years ago was largely limited to reactions at nucleophilic cysteine and lysine residues. If applied in a biologically benign manner, this chemistry could form the basis of true Synthetic Biology. PMID:25190082

Spicer, Christopher D; Davis, Benjamin G

2014-01-01

429

Role of copper in IUDs.  

PubMed

This report analyzes the contraceptive potential of copper IUDs. The antifertility action of copper in IUDs is considered to involve 1) inhibition of zinc-containing metalloenzymes in the uterus, 2) reduced activity in the endometrial steroid receptor, 3) production of low levels of human chorionic gonadotropin in the luteal phase, 4) depression of ovum transport through the uterine tubes and inhibition of the penetration of cervical mucus by sperm, 5) elevation of the fibrinoloytic activity of the endometrium, and 6) depression of the synthesis of prostaglandins. These biochemical and physiological changes in response to copper released from the IUD are thought to cause only a local effect and systemic accumulation of copper from the device is considered unlikely. The rate of release of copper varies during the time the device remains in the uterus, declining exponentially during the 1st 2 years of use and then increasing as a result of destabilization and fragmentation of the accumulated layer of copper corrosion products. Accelerated copper loss is associated with menorrhagis, higher parity, and the presence of a cervical lesion at the time of IUD insertion. However, accelerated loss of the copper coil does not seem to cause either copper toxicity or decreased contraceptive efficiency. Women with insulin-dependent diabetes may manifest a different copper corrosion process and possibly a higher incidence of contraceptive failure. Since copper IUDs must be replaced more often than inert devices, there is a risk of increased incidence of pelvic inflammatory disease, reported to occur more frequently after replacement of an IUD. The longterm retention of copper IUDs probably has the same risk of infection as that associated with inert devices, and there is no evidence to link the presence of copper with any bacteriostatic or bactericidal action in vivo. The probability of fragmentation is reduced by new types of devices in which the copper wire is replaced by copper bands or a core of an inert metal is included inside the copper wire. It is concluded that copper IUDs, especially the newer devices with a more stable copper component, provide a successful fertility control method. PMID:12266319

Chantler, E N

1984-08-01

430

Gold Nanoclusters Entrapped in the alpha-Cages of Y Zeolites: Structural Characterization by X-ray Absorption Spectroscopy  

SciTech Connect

Au(CH{sub 3}){sub 2}(C{sub 5}H{sub 7}O{sub 2}) was used as a precursor to synthesize mononuclear gold complexes in faujasites, NaY zeolite, and dealuminated Y zeolite. Treatment of these supported complexes in flowing helium as the temperature was increased led to the gradual reduction of the gold and formation of gold nanoclusters in each zeolite, which were characterized by X-ray absorption spectroscopy. After treatment at the highest temperature, 573 K, the average diameters of the gold clusters were approximately 10 and 8 {angstrom} in NaY zeolite and dealuminated Y zeolite, respectively; these clusters are smaller than the diameters of the {alpha}-cages of the zeolite. The results indicate that the supported clusters were trapped within these cages and that the cages limited their sizes; in contrast, clusters formed similarly on the surfaces of metal oxides are significantly larger than those formed in the zeolites.

Fierro-Gonzalez,J.; Hao, Y.; Gates, B.

2007-01-01

431

Gold Nanoclusters Entrapped in the Alpha-Cages of Y-Zeolites: Structural Characterization By X-Ray Absorption Spectroscopy  

SciTech Connect

Au(CH{sub 3}){sub 2}(C{sub 5}H{sub 7}O{sub 2}) was used as a precursor to synthesize mononuclear gold complexes in faujasites, NaY zeolite, and dealuminated Y zeolite. Treatment of these supported complexes in flowing helium as the temperature was increased led to the gradual reduction of the gold and formation of gold nanoclusters in each zeolite, which were characterized by X-ray absorption spectroscopy. After treatment at the highest temperature, 573 K, the average diameters of the gold clusters were approximately 10 and 8 {angstrom} in NaY zeolite and dealuminated Y zeolite, respectively; these clusters are smaller than the diameters of the {alpha}-cages of the zeolite. The results indicate that the supported clusters were trapped within these cages and that the cages limited their sizes; in contrast, clusters formed similarly on the surfaces of metal oxides are significantly larger than those formed in the zeolites.

Fierro-Gonzalez, J.C.; Hao, Y.; Gates, B.C.

2009-06-03

432

Adsorption of zearalenone by organomodified natural zeolitic tuff.  

PubMed

Adsorption of zearalenone (ZEN) by natural zeolitic tuff, modified with different numbers of octadecyldimethylbenzylammonium (ODMBA) ions, was investigated. The results of solid-state 1H NMR analysis of the starting material suggested that zeolitic tuff is rich in mineral clinoptilolite, confirming the results of previous thermal stability study. Three organozeolites (OZ-2, OZ-5, and OZ-10) were prepared with ODMBA surface coverages of 20, 50, and 100 mmol/100 g. The mechanism of ZEN sorption by the three organozeolites was investigated through the determination of the adsorption isotherms at pH 3, 7, and 9. Adsorption of ZEN by organozeolites was best represented by a linear type of isotherm at pH 3, while at pH 7 and 9, adsorption of ZEN by organozeolites followed a nonlinear (Langmuir) type of isotherm. The different shape of the ZEN adsorption isotherms for the three organozeolites with different levels of ODMBA at the zeolitic surface at different pH values suggests that the adsorption mechanism may be dependent on the form of ZEN in solution. Since, at pH 3, ZEN exists in solution as the neutral form, the linear isotherms at pH 3 suggested that hydrophobic interactions are probably responsible for adsorption of neutral, hydrophobic ZEN onto the hydrophobic surface of the organozeolites. At pH 7, the phenolate anion is present in water solution, while at pH 9, ZEN is almost entirely in the anionic form. The nonlinear isotherms obtained for ZEN adsorption by the three organozeolites suggest that sorption appears to be the result of the adsorption process as well as partitioning. PMID:17368471

Dakovi?, Aleksandra; Matijasevi?, Srdan; Rottinghaus, George E; Dondur, Vera; Pietrass, Tanja; Clewett, Catherine F M

2007-07-01

433

Copper@polypyrrole nanocables  

PubMed Central

A simple hydrothermal redox reaction between microcrystalline CuOHCl and pyrrole leads to the isolation of striking nanostructures formed by polypyrrole-coated copper nanocables. These multicomponent cables that feature single-crystalline face-centered cubic Cu cores (ca. 300 nm wide and up to 200 ?m long) are smoothly coated by conducting polypyrrole, which in addition to its functionality, offers protection against oxidation of the metal core. PMID:23009710

2012-01-01

434

Selective toluene disproportionation over pore size controlled MFI zeolite  

SciTech Connect

Selective disproportionate of toluene to p-xylene was studied over modified MFI aluminosilicate. The relationship between extent of silica deposition and para selectivity was established. The effect of reaction parameters such as temperature and weight hourly space velocity (WHSV) on para selectivity was considered. Kinetics of reaction in the temperature range 723--773 K was carried out. The estimated activation energy value is lower than reported for toluene disproportionation in the literature. This has been explained on the basis of enhanced intracrystalline diffusion in the modified zeolite.

Das, J.; Bhat, Y.S.; Halgeri, A.B. (Indian Petrochemicals Corp. Ltd., Gujarat (India). Research Centre)

1994-02-01

435

Adsorption of water and ethanol in MFI-type zeolites.  

PubMed

Water and ethanol vapor adsorption phenomena are investigated systematically on a series of MFI-type zeolites: silicalite-1 samples synthesized via both alkaline (OH(-)) and fluoride (F(-)) routes, and ZSM-5 samples with different Si/Al ratios as well as different charge-balancing cations. Full isotherms (0.05-0.95 activity) over the range 25-55 °C are presented, and the lowest total water uptake ever reported in the literature is shown for silicalite-1 made via a fluoride-mediated route wherein internal silanol defects are significantly reduced. At a water activity level of 0.95 (35 °C), the total water uptake by silicalite-1 (F(-)) was found to be 0.263 mmol/g, which was only 12.6%, 9.8%, and 3.3% of the capacity for silicalite-1 (OH(-)), H-ZSM-5 (Si/Al:140), and H-ZSM-5 (Si/Al:15), respectively, under the same conditions. While water adsorption shows distinct isotherms for different MFI-type zeolites due to the difference in the concentration, distribution, and types of hydrophilic sites, the ethanol adsorption isotherms present relatively comparable results because of the overall organophilic nature of the zeolite framework. Due to the dramatic differences in the sorption behavior with the different sorbate-sorbent pairs, different models are applied to correlate and analyze the sorption isotherms. An adsorption potential theory was used to fit the water adsorption isotherms on all MFI-type zeolite adsorbents studied. The Langmuir model and Sircar's model are applied to describe ethanol adsorption on silicalite-1 and ZSM-5 samples, respectively. An ideal ethanol/water adsorption selectivity (?) was estimated for the fluoride-mediated silicalite-1. At 35 °C, ? was estimated to be 36 for a 5 mol % ethanol solution in water increasing to 53 at an ethanol concentration of 1 mol %. The adsorption data demonstrate that silicalite-1 made via the fluoride-mediated route is a promising candidate for ethanol extraction from dilute ethanol-water solutions. PMID:22568830

Zhang, Ke; Lively, Ryan P; Noel, James D; Dose, Michelle E; McCool, Benjamin A; Chance, Ronald R; Koros, William J

2012-06-12

436

Vapor-phase esterification catalyzed by decationized Y zeolites  

SciTech Connect

The kinetics of acetic acid esterification with ethyl alcohol, in vapor phase, have been studied in the presence of decationized Y zeolite catalysts. Two kinetic models have been considered: a Rideal model and a bimolecular surface reaction model. Both of these models satisfactorily fit the experimental data. The choice of the better model has been made on the basis of the physical significance of the parameters obtained by nonlinear regression analysis of the data. Suggestions are given on the mechanism of the reaction, which appears to be similar to that occurring under homogeneous liquid-phase conditions.

Santacesaria, E.; Gelosa, D.; Danise, P.; Carra, S.

1983-04-01

437

Direct Production of Copper  

NASA Astrophysics Data System (ADS)

The use of commercially pure oxygen in flash smelting a typical chalcopyrite concentrate or a low grade comminuted matte directly to copper produces a large excess of heat. The heat balance is controlled by adjusting the calorific value of the solid feed. A portion of the sulfide material is roasted to produce a calcine which is blended with unroasted material, and the blend is then autogeneously smelted with oxygen and flux directly to copper. Either iron silicate or iron calcareous slags are produced, both being subject to a slag cleaning treatment. Practically all of the sulfur is contained in a continuous stream of SO2 gas, most of which is strong enough for liquefaction. A particularly attractive feature of these technologies is that no radically new metallurgical equipment needs to be developed. The oxygen smelting can be carried out not only in the Inco type flash furnace but in other suitable smelters such as cyclone furnaces. Another major advantage stems from abolishion of the ever-troublesome converter aisle, which is replaced with continuous roasting of a fraction of the copper sulfide feed.

Victorovich, G. S.; Bell, M. C.; Diaz, C. M.; Bell, J. A. E.

1987-09-01

438

Heteroleptic Copper Switches  

PubMed Central

Heteroleptic copper compounds have been designed and synthesized on solid supports. Chemical redox agents were used to change the oxidation state of the SiO2-immobilized heteroleptic copper compounds from Cu(I) to Cu(II) and then back to Cu(I). Optical spectroscopy of a dimethyl sulfoxide (DMSO) suspension demonstrated the reversibility of the Cu(I)/Cu(II) SiO2-immobilized compounds by monitoring the metal-to-ligand charge transfer (MLCT) peak at about 450 nm. EPR spectroscopy was used to monitor the isomerization of Cu(I) tetrahedral to Cu(II) square planar. This conformational change corresponds to a 90° rotation of one ligand with respect to the other. Conductive AFM (cAFM) and macroscopic gold electrodes were used to study the electrical properties of a p+ Si-immobilized heteroleptic copper compound where switching between the Cu(I)/Cu(II) states occurred at ?0.8 and +2.3 V. PMID:20964417

Kabehie, Sanaz; Xue, Mei; Stieg, Adam Z.; Liong, Monty; Wang, Kang L.

2013-01-01

439

Personalizing Behavior Modification.  

ERIC Educational Resources Information Center

Process reinforcement is proposed as a reinforcement method that is more comfortable, personal, comprehensive, and interactive than traditional behavior modification. Process reinforcement strengthens desired behaviors by engaging learners in a one-on-one examination of how they achieved correct responses and by practicing comfortable eye contact…

White, Debra G.; And Others

1987-01-01

440

Soviet ionospheric modification research  

Microsoft Academic Search

Soviet published literature in ionospheric modification research by high-power radio waves is assessed, including an evaluation of its impact on and applications to future remote-sensing and telecommunications systems. This assessment is organized to place equal emphasis on basic research activities, designed to investigate both the natural geophysical environment and fundamental plasma physics; advanced research programs, such as those studying artificial

L. M. Duncan; H. C. Carlson; F. T. Djuth; J. A. Fejer; N. C. Gerson; T. Hagfors; D. B. Newman Jr.; R. L. Showen

1988-01-01

441

The RNA modification database  

Microsoft Academic Search

The RNA modification database provides a com- prehensive listing of post-transcriptionally modified nucleosides from RNA and is maintained as an updated version of the initial printed report. Informa- tion provided includes: type(s) of RNA in which found and phylogenetic distribution; common chemical names and symbols; Chemical Abstracts registry numbers and index names; chemical structures; initial literature citations for structural characterization

Pamela F. Crain; James A. Mccloskey

1996-01-01

442

Chemical modification of biocatalysts  

Microsoft Academic Search

Although several powerful methods exist for the redesign of enzyme structure and function these are typically limited to the 20 most abundant proteinogenic amino acids. The use of chemical modification overcomes this limitation to allow virtually unlimited alteration of amino acid sidechain structures. If heterogeneous mixtures of enzyme products are to be avoided, however, the required chemistry should be efficient,

Benjamin G Davis

2003-01-01

443

Benign Weather Modification.  

National Technical Information Service (NTIS)

Weather modification is a technology once embraced by the U.S. military as a tool to help both wartime and peacetime missions. However, interest in the ability to modify weather has waned over recent years and is now nearly non-existent. This study examin...

B. E. Coble

1996-01-01

444

Benign Weather Modification.  

National Technical Information Service (NTIS)

Weather modification is a technology once embraced by the United States (US) military as a tool to help both wartime and peacetime missions. However, interest in the ability to modify weather has waned over recent years and is now nearly nonexistent. This...

B. B. Coble

1997-01-01

445

Hierarchical zeolites: enhanced utilisation of microporous crystals in catalysis by advances in materials design.  

PubMed

The introduction of synthetic zeolites has led to a paradigm shift in catalysis, separations, and adsorption processes, due to their unique properties such as crystallinity, high-surface area, acidity, ion-exchange capacity, and shape-selective character. However, the sole presence of micropores in these materials often imposes intracrystalline diffusion limitations, rendering low utilisation of the zeolite active volume in catalysed reactions. This critical review examines recent advances in the rapidly evolving area of zeolites with improved accessibility and molecular transport. Strategies to enhance catalyst effectiveness essentially comprise the synthesis of zeolites with wide pores and/or with short diffusion length. Available approaches are reviewed according to the principle, versatility, effectiveness, and degree of reality for practical implementation, establishing a firm link between the properties of the resulting materials and the catalytic function. We particularly dwell on the exciting field of hierarchical zeolites, which couple in a single material the catalytic power of micropores and the facilitated access and improved transport consequence of a complementary mesopore network. The carbon templating and desilication routes as examples of bottom-up and top-down methods, respectively, are reviewed in more detail to illustrate the benefits of hierarchical zeolites. Despite encircling the zeolite field, this review stimulates intuition into the design of related porous solids (116 references). PMID:18949124

Pérez-Ramírez, Javier; Christensen, Claus H; Egeblad, Kresten; Christensen, Christina H; Groen, Johan C

2008-11-01

446

Amphiphilic organosilane-directed synthesis of crystalline zeolite with tunable mesoporosity.  

PubMed

Zeolites are a family of crystalline aluminosilicate materials widely used as shape-selective catalysts, ion exchange materials, and adsorbents for organic compounds. In the present work, zeolites were synthesized by adding a rationally designed amphiphilic organosilane surfactant to conventional alkaline zeolite synthesis mixtures. The zeolite products were characterized by a complementary combination of X-ray diffraction (XRD), nitrogen sorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The analyses show that the present method is suitable as a direct synthesis route to highly mesoporous zeolites. The mesopore diameters could be uniformly tailored, similar to ordered mesoporous silica with amorphous frameworks. The mesoporous zeolite exhibited a narrow, small-angle XRD peak, which is characteristic of the short-range correlation between mesopores, similar to disordered wormhole-like mesoporous materials. The XRD patterns and electron micrographs of the samples taken during crystallization clearly showed the evolution of the mesoporous structure concomitantly to the crystallization of zeolite frameworks. The synthesis of the crystalline aluminosilicate materials with tunable mesoporosity and strong acidity has potentially important technological implications for catalytic reactions of large molecules, whereas conventional mesoporous materials lack hydrothermal stability and acidity. PMID:16892049

Choi, Minkee; Cho, Hae Sung; Srivastava, Rajendra; Venkatesan, Chithravel; Choi, Dae-Heung; Ryoo, Ryong

2006-09-01

447

Recovery of oxygenated ignitable liquids by zeolites, Part II: Dual-mode heated passive headspace extraction.  

PubMed

Previous studies performed by our research group have suggested that zeolites are a suitable adsorbent for the recovery of oxygenates from fire debris through heated passive headspace extraction. Zeolite 13X, in particular, has been shown to be effective for recovering analytes with molecular diameters smaller than 10Å. The primary aim of this study was to evaluate the addition of zeolite 13X to heated headspace extraction for the recovery of ignitable liquids. Comparative recoveries of petroleum and alcohol-based ignitable liquid mixtures were studied utilizing activated charcoal strips and zeolites, individually and in tandem. In the presence of both adsorption media within the same sample can, activated charcoal strips recovered the majority of gasoline components, while zeolites recovered the majority of oxygenated compounds. This phenomenon was attributed to the size exclusion properties, polarity, and available surface area of zeolites. This research supports the use of zeolites with activated charcoal strips in a "dual-mode" preparation for casework in which the presence of an ignitable liquid is suspected. The described method allows for the recovery and concentration of ignitable liquid residues in a single extraction procedure, whether the ignitable liquid is petroleum-based or oxygenated in nature. PMID:24811978

Rodgers, Corissa L; St Pierre, Kathryne A; Hall, Adam B

2014-07-01

448

Evaluation of synthetic zeolites as oral delivery vehicle for anti-inflammatory drugs  

PubMed Central

Objective(s): In this research, zeolite X and zeolite Y were used as vehicle to prepare intestine targeted oral delivery systems of indomethacin and ibuprofen. Materials and Methods: A soaking procedure was implemented to encapsulate indomethacin or ibuprofen within synthetic zeolites. Gravimetric methods and IR spectra of prepared formulations were used to assess drug loading efficiencies into zeolite structures. Scanning Electron Microscopy (SEM) was also utilized to determine morphologies changes in synthetic zeolites after drug loading. At the next stage, dissolution studies were used to predict the in vivo performance of prepared formulations at HCl 0.1 N and PBS pH 6.5 as simulated gastric fluid (SGF) and simulated intestine fluid (SIF), respectively. Results: Drug loadings of prepared formulations was determined between 24-26 % w/w. Dissolution tests at SGF were shown that zeolites could retain acidic model drugs in their porous structures and can be able to limit their release into the stomach. On the other hand, all prepared formulations completely released model drugs during 3 hr in simulated intestine fluid. Conclusion: Obtained results indicated zeolites could potentially be able to release indomethacin and ibuprofen in a sustained and controlled manner and reduced adverse effects commonly accompanying oral administrations of NSAIDs. PMID:24967062

Khodaverdi, Elham; Honarmandi, Reza; Alibolandi, Mona; Baygi, Roxana Rafatpanah; Hadizadeh, Farzin; Zohuri, Gholamhossein

2014-01-01

449

Densification of salt-occluded zeolite a powders to a leach-resistant monolith  

SciTech Connect

Pyrochemical processing of spent fuel from the Integral Fast Reactor (IFR) yields a salt waste of LiCl-KCl that contains approximately 6 wt% fission products, primarily as CsCl and SrCl{sub 2}. Past work has shown that zeolite A will preferentially sorb cesium and strontium and will encapsulate the salt waste in a leach-resistant, radiation-resistant aluminosilicate matrix. However, a method is sill needed to convert the salt-occluded zeolite powders into a form suitable for geologic disposal. We are thus investigating a method that forms bonded zeolite by hot pressing a mixture of glass frit and salt-occluded zeolite powders at 990 K (717{degree}C) and 28 MPa. The leach resistance of the bonded zeolite was measured in static leach tests run for 28 days in 363 K (90{degree}C) deionized water. Normalized release rates of all elements in the bonded zeolite were low, <1 g/m{sup 2} d. Thus, the bonded zeolite may be a suitable waste form for IFR salt waste.

Lewis, M.A.; Fischer, D.F.; Murhpy, C.D.

1993-10-01

450

Properties of diclofenac sodium sorption onto natural zeolite modified with cetylpyridinium chloride.  

PubMed

In this study an investigation of a model drug sorption onto cationic surfactant-modified natural zeolites as a drug formulation excipient was performed. Natural zeolite was modified with cetylpyridinium chloride in amounts equivalent to 100, 200 and 300% of its external cation-exchange capacity. The starting material and obtained organozeolites were characterized by Fourier transform infrared spectroscopy, zeta potential measurements and thermal analysis. In vitro sorption of diclofenac sodium as a model drug was studied for all surfactant/zeolite composites by means of sorption isotherm measurements in aqueous solutions (pH 7.4). The modified zeolites with three levels of surfactant coverage within the short activation time were prepared. Zeta potential measurements and thermal analysis showed that when the surfactant loading level was equal to external cation-exchange value, almost monolayer of organic phase were present at the zeolitic surface while higher amounts of surfactant produced less extended bilayers, ordered bilayers or admicelles at the zeolitic surface. Modified zeolites, obtained in this manner, were effective in diclofenac sodium sorption and the organic phase derived from adsorbed cetylpyridinium chloride was the primary sorption phase for the model drug. The Langmuir isotherm was found to describe the equilibrium sorption data well over the entire concentration range. The separate contributions of the adsorption and partition to the total sorption of DS were analyzed mathematically. Results revealed that that adsorption and partitioning of the model drug take place simultaneously. PMID:21134730

Krajišnik, Danina; Dakovi?, Aleksandra; Milojevi?, Maja; Malenovi?, An?elija; Kragovi?, Milan; Bogdanovi?, Danica Bajuk; Dondur, Vera; Mili?, Jela

2011-03-01

451

Fabrication of Poly(p-Phenylene)/Zeolite Composites and Their Responses Towards Ammonia  

PubMed Central

Poly(p-phenylene) (PPP) was chemically synthesized via oxidative polymerization using benzene and doped with FeCl3. The electrical conductivity response of the doped PPP (dPPP) towards CO, H2 and NH3 is investigated. dPPP shows no electrical conductivity response towards the first two gases (CO and H2), but it shows a definite negative response towards NH3. The electrical conductivity sensitivity of dPPP increases linearly with increasing NH3 concentration. To improve the sensitivity of the sensor towards NH3, ZSM-5 zeolite is added into the conductive polymer matrix. The electrical sensitivity of the sensor increases with increasing zeolite content up to 30%. The effect of the type of cation in the zeolite pores is investigated: namely, Na+, K+, NH4+ and H+. The electrical conductivity sensitivity of the composites with different cations in the zeolite can be arranged in this order: K+ < no zeolite < Na+ < NH4+ < H+. The variation in electrical sensitivity with cation type can be described in terms of the acid-base interaction, the zeolite pore size and surface area. The PPP/Zeolite composite with H+ possesses the highest electrical sensitivity of ?0.36 since H+ has the highest acidity, the highest pore volume and surface area, which combine to induce a more favorable NH3 adsorption and interaction with the conductive polymer. PMID:22408492

Phumman, Pimchanok; Niamlang, Sumonman; Sirivat, Anuvat

2009-01-01

452

Shear Rheology of Suspensions of Porous Zeolite Particles in Concentrated Polymer Solutions  

NASA Astrophysics Data System (ADS)

We present experimental data on the shear rheology of Ultem (polyetherimide)/NMP(l-methyl-2-pyrrolidinone) solutions with and without suspended surface-modified porous/nonporous zeolite (ZSM-5) particles. We found that the porous zeolite suspension