Note: This page contains sample records for the topic zeolite modification copper from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Zeolite modification II - direct fluorination  

Microsoft Academic Search

Over the past thirty years, zeolite science has grown into a major branch of chemistry. A large number of new zeolite materials have been made by both direct hydrothermal synthesis and by post-synthesis modification. This has led to a large number of new applications in such diverse fields as catalysis, adsorption and ion exchange. In synthesis alone, over one hundred

B. M. Lok; F. P. Gortsena; P. J. Izod; C. A. Messina; H. Rastelli

1982-01-01

2

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

3

The nature of 'overexchanged' copper and platinum on zeolites  

NASA Astrophysics Data System (ADS)

The uptake of platinum and copper tetra-ammine (PTA and CTA, [(NH3)4Pt]2+ and [(NH3)4Cu]2+) into zeolites was compared over silica and three zeolites (Y, MOR and MFI) with different points of zero charge and aluminium content. Adsorption was determined as a function of pH at several metal concentrations, and pH shifts relative to metal free control experiments were carefully monitored. The uptake of both metal ammine complexes onto silica is well described by electrostatic adsorption. We suggest that the metal cations interact with zeolites by two mechanisms, ion exchange at the Al exchange sites and electrostatic adsorption at silanol groups. The former is the dominant mechanism at low to mid pH, and the latter at high pH. This effect is most clearly manifested in zeolites with low aluminium content such as ZSM5; electrostatic adsorption at high pH in ZSM5 yields metal loadings much in excess of the ion exchange capacity and so gives rise to 'overexchange'. Differences between PTA and CTA can be explained by the weaker stability of the CTA complex and its response to the decrease in local pH near the adsorption plane of low PZC zeolites. This change in local pH near oxide surfaces is characteristic of electrostatic adsorption. As the local pH decreases, the CTA ion is probably converted to a dimerized copper complex, perhaps Cu2(OH)22+. A portion of the released ammonia is protonated, increasing the solution pH. In high PZC, high aluminium zeolites with high ion exchange capacity, there is relatively little contribution from electrostatic adsorption.

Schreier, Marc; Teren, Sarah; Belcher, Latonia; Regalbuto, John R.; Miller, Jeffrey T.

2005-07-01

4

Effect of modification on catalytic properties of NaY zeolites  

SciTech Connect

The effect of treatment with hydrogen, hydrogen sulfide, and steam on the catalytic properties of NaY zeolites has been studied. A mechanism has been proposed for activation of the zeolites, which explains the appearance of Broensted acid centers on modified samples. The influence of modification temperature and the degree of decationization of the zeolites on the promoting capacity of the latter in the cumene cracking reaction has been studied.

Krikorov, V.G.; Spiridonov, S.E.; Khadzhiev, S.N.

1988-04-01

5

Copper-phthalocyanine encapsulated into zeolite-Y with high Si/Al: An EPR study  

NASA Astrophysics Data System (ADS)

Copper (II) phthalocyanine (CuPc) molecules encapsulated into zeolite-Y with Si/Al ratios of 2.7 and 410 were prepared by an in situ synthesis and characterized by UV-Vis and electron paramagnetic resonance (EPR) spectroscopies. Resolved Cu-hyperfine and N-superhyperfine structures were observed in the EPR spectrum of CuPc encapsulated into zeolite-Y with a high Si/Al ratio. UV-Vis and EPR studies as well as theoretical calculations suggest that the encapsulated CuPc molecule was distorted in zeolite-Y with keeping of the square-planar symmetry around the center copper (II) ion.

Yahiro, Hidenori; Kimoto, Kunihiro; Yamaura, Hiroyuki; Komaguchi, Kenji; Lund, Anders

2005-10-01

6

Selective catalytic reduction of nitrogen monoxide by decane on copper-exchanged beta zeolites  

Microsoft Academic Search

The selective catalytic reduction (SCR) of NO by decane has been investigated on a series of copper exchanged beta zeolite (BEA), and the catalytic behaviour has been compared to Cu-MFI. The different solids were characterised by temperature programmed reduction by H2 and temperature programmed desorption of NO in order to determine the nature, reducibility and accessibility of copper species. Only

G. Delahay; B. Coq; L. Broussous

1997-01-01

7

Geometry and Framework Interactions of Zeolite-Encapsulated Copper(II)Histidine Complexes  

Microsoft Academic Search

The coordination geometry of zeolite-encapsulated copper(II)-histidine (CuHis) complexes, prepared by ion exchange of the complexes from aqueous solutions into zeolite NaY, was determined by a combination\\u000aof UV-vis-NIR diffuse reflectance spectroscopy (DRS), X-band EPR, electron-spin-echo envelope modulation (ESEEM), and high field (W-band) pulsed ENDOR techniques. X-band EPR spectroscopy detected two distinct\\u000acomplexes, A and B, which are different from the

B. M. Weckhuysen; R. Grommen; P. Manikandan; Y. Gao; T. Shane; J. J. Shane; R. A. Schoonheydt; Daniella Goldfarb

2000-01-01

8

Modification of zsm-5 zeolite with trimethyl phosphite part 1. structure and acidity  

Microsoft Academic Search

In the present work we have studied the structure and the acidic properties of HZSM-5 zeolite modified with trimethyl phosphite. The modifications were carried out by using a chemical vapour deposition method as well as impregnation from n-octane solution. Both modification techniques resulted in materials with similar acidic properties. Trimethyl phosphite reacted with both Brönsted acid sites and terminal SiOH

Pekka Tynjälä; Tuula T. Pakkanen

1998-01-01

9

Zeolite-like copper iodide framework with new 6(6) topology.  

PubMed

We have described an unprecedented three-dimensional zeolite-like copper iodide constructed from Cu4I4(DABCO)4 (DABCO = 1,4-diazabicyclo[2.2.2]octane) supertetrahedron units. This compound forms a four-connected network with new 6(6) topology. Its structure reveals one-dimensional channels along the [001] direction, and the framework displays interesting self-penetration. The title compound shows photoluminescence at room temperature in the solid state. PMID:17256998

Bi, Minghui; Li, Guanghua; Zou, Yongchun; Shi, Zhan; Feng, Shouhua

2007-02-01

10

Host-guest chemistry of copper(II)-histidine complexes encaged in zeolite Y.  

PubMed

Structural analysis has been carried out on copper(II)-histidine (Cu(2+)/His) complexes after immobilization in the pore system of the zeolites NaY and de-aluminated NaY (DAY). The aim of this study was to determine the geometrical structure of Cu(2+)/His complexes after encaging, to obtain insight into both the effect of the zeolite matrix on the molecular structure and redox properties of the immobilized complexes. In addition to N(2) physisorption and X-ray fluorescence (XRF) analyses, a combination of UV/Vis/NIR, ESR, X-ray absorption (EXAFS and XANES), IR, and Raman spectroscopy was used to obtain complementary information on both the first coordination shell of the copper ion and the orientation of the coordinating His ligands. It was demonstrated that two complexes (A and B) are formed, of which the absolute and relative abundance depends on the Cu(2+)/His concentration in the ion-exchange solution and on the Si/Al ratio of the zeolite material. In complex A, one His ligand coordinates in a tridentate facial-like manner through N(am), N(im), and O(c), a fourth position being occupied by an oxygen atom from a zeolite Brønsted site. In complex B, two His ligands coordinate as bidentate ligands; one histamine-like (N(am), N(im)) and the other one glycine-like (N(am), O(c)). In particular the geometrical structure of complex A differs from the preferred structure of Cu(2+)/His complexes in aqueous solutions; this fact implies that the zeolite host material actively participates in the coordination and orientation of the guest molecules. The tendency for complex A to undergo reduction in inert atmosphere to Cu(1+) (as revealed by dynamic XANES studies) suggests activation of complex A by the interaction with the zeolite material. EXAFS analysis confirms the formation of a distorted four coordinate geometry of complex A, suggesting that the combination of zeolite and one His ligand force the Cu(2+) complex into an activated, entactic state. PMID:16807946

Mesu, J Gerbrand; Visser, Tom; Beale, Andrew M; Soulimani, Fouad; Weckhuysen, Bert M

2006-09-18

11

Catalytic and electron spin resonance studies of propylene oxidation on copper(II)-exchanged X zeolite: Temperature dependence of copper(II) migration  

SciTech Connect

The copper(II)-catalyzed oxidation of propylene on CuK-X zeolite was studied under conditions of excess oxygen over the temperature range of 100 to 400{degree}C in a flow system to investigate the temperature dependence of the catalytic activity and the migration of copper(II) species and Cu(II) coordination complexes in the zeolite framework. It is shown that the percent of propylene conversion depends upon the reaction temperature and upon the extent of Cu(II) exchanged into the zeolite. Temperature causes the cupric ions to migrate near the six-ring window between the {alpha} and {beta} cages of the zeolite structure where they complex with propylene and induce the oxidation reaction. Arrhenius activation energies decrease with increasing copper(II) content. The decreasing activation energy with decreasing Cu(II) content is associated with different site occupancies of Cu(II) within the zeolite structure. Electron spin resonance studies show that cupric ions are initially distributed in SI hexagonal prism sites and SI{prime} sites in the {beta} cage adjacent to the hexagonal prisms in dehydrated CuK-X zeolite.

Yu, Jongsung; Kevan, L. (Univ. of Houston, TX (USA))

1990-09-20

12

Zeolite framework stabilized copper complex inspired by the 2-His-1-carboxylate facial triad motif yielding oxidation catalysts.  

PubMed

The stabilization of a mononuclear copper(II) complex with one MIm2Pr ligand [MIm2Pr = 3,3-bis(1-methylimidazol-2-yl)propionate] in the supercages of zeolite Y was attempted, and the resulting materials were tested for their activity in oxidation catalysis. The preparation procedure yielded initially two species (labeled 1 and 2) within the pore system of the zeolite material, which differ in molecular structure and chemical composition as determined by UV/vis, ESR, IR, and XAFS spectroscopy. In species 1, the copper was found to be five-coordinated, with one MIm2Pr ligand in a facial-type NNO coordination toward copper, the other two coordination sites being occupied by oxygen atoms from either the zeolite framework and/or a water molecule. The total charge of this complex is 1+. In species 2, the copper is surrounded by two MIm2Pr ligands, both in a facial-type coordination mode, identical to the homogeneous Cu(MIm2Pr)2 complex. This neutral species 2 is easily washed out of the zeolite, whereas the mononuclear species 1 remains inside the zeolite material upon washing. The spectroscopic characteristics and activity for 3,5-di-tert-butylcatechol and benzyl alcohol oxidation of species 1 compared closely with that of the zeolite-immobilized Cu(histidine) complexes but differed from that of the homogeneous Cu(MIm2Pr)2 complex. It was therefore found that encapsulation in zeolite offers a route to stabilize a 5-fold-coordinated copper complex with novel catalytic properties. This 1:1 Cu(MIm2Pr) complex is not formed in solution. PMID:16522101

Kervinen, Kaisa; Bruijnincx, Pieter C A; Beale, Andrew M; Mesu, J Gerbrand; van Koten, Gerard; Klein Gebbink, Robertus J M; Weckhuysen, Bert M

2006-03-15

13

Adsorption of oxygen on copper in Cu/HZSM5 zeolites.  

PubMed

The present study focuses on the characterization of the active sites for oxygen adsorption in both copper-free and copper-containing HZSM5 zeolites. FTIR, EPR, EXAFS and UV-Vis measurements offer insight into the initial state of the catalyst before oxygen adsorption. Both liquid and solid state ion exchanged samples contain a certain amount of Cu(ii) and Cu(i) ions in the alpha3, alpha4 and gamma6 position, their population ratio depending on the ion exchange temperature. They are accessible for interaction with the adsorbate, as the copper-oxygen spin exchange demonstrates. Both the sample magnetization and the EXAFS analysis indicate that 10-30% of the Cu(ii) exists in the form of oxygen bridged Cu-Cu pairs. UV-Vis measurements prove that two different antiferromagnetically coupled copper peroxide complexes are formed during the sample preparation process, the bis(mu-oxo)- and (mu-eta(2):eta(2)-peroxo) dimers. One of the complexes is susceptible to oxygen adsorption, which cleaves it irreversibly into two individual Cu(ii)-O(2)(-) units, while Cu(i) ions are oxidised to the same species. The Brønsted acid sites are also able to adsorb oxygen both at room and low temperatures. The presence of the different active sites may be an explanation for the high catalytic activity of the Cu/HZSM5 zeolite. The Brønsted sites near copper centers could protonate the peroxide complexes, leading to the in situ formation of hydrogen peroxide, a common oxidant. This peroxide would be a highly active species for catalytic reactions. PMID:20505852

Ene, Augusta Bianca; Bauer, Matthias; Archipov, Tanja; Roduner, Emil

2010-05-26

14

Copper active sites for the selective reduction of nitrogen monoxide by propane on Cu-MFI catalysts and non-zeolitic supported-copper solids  

Microsoft Academic Search

The selective reduction of NO by C3H8 is performed on copper-based catalysts: Cu\\/Al2O3, Cu\\/SiO2, Cu\\/SiO2–Al2O3 solids, fresh and hydrothermally-treated Cu-MFI with various Si\\/Al ratios. For all the Cu-MFI solids and for the non-zeolitic\\u000a supported-copper solids with low copper loadings, O2 promotes the reduction of NO. The C3H8–NO reaction rate correlates with the number of accessible and isolated Cun+ ions deduced

Zakaria Chajar; Valérie Le Chanu; Michel Primet; Hélène Praliaud

1998-01-01

15

Modification of Brønsted acidity of zeolites by Ga +, GaO + and AlO +: comparison for alkane activation  

Microsoft Academic Search

Modification of Brønsted acid sites in zeolites by Ga+, GaO+ and AlO+ ions profoundly changes the way of alkane activation. Over Brønsted acid protons propane is activated via a carbonium ion mechanism resulting in propylene, methane and ethylene as hydrocarbon products. Over Ga+ ions, heterolytic dissociation of propane takes place over the Lewis acid-base pair formed by the Ga+ ion

E. J. M. Hensen; E. A. Pidko; N. Rane; R. A. van Santen

2007-01-01

16

The leading role of association in framework modification of highly siliceous zeolites with adsorbed methylamine.  

PubMed

Affinity index (AT value), adsorption heat, X-ray diffraction (XRD), and 13C and 29Si magic-angle spinning (MAS) NMR, FTIR, and Raman spectroscopies were used to study the interaction of highly siliceous MFI-, FAU-, and FER-type zeolites with adsorbed methylamine (MA). Compared with the data for methanol, the much higher AT values and adsorption heats, and significant changes in XRD patterns, 29Si MAS NMR spectra, and FTIR spectra for the zeolites after adsorption of MA, revealed a strong hydrogen-bonding interaction between the perfect framework of the zeolites and the adsorbed MAs. This interaction results from the fact that the H atom of the amine group attacks the [Si-O] framework to form a Si-OHN bond, which leads to the appearance of Si-N bonds in the zeolites at 323 K. Therefore, the zeolite framework can be modified with MA under mild conditions. The highly siliceous MFI zeolite and the H-ZSM-5 zeolite with SiO2/Al2O3=31:1 were modified with MA and investigated by temperature-programmed desorption of CO2. The modified zeolites exhibited greatly enhanced basic properties in comparison with those of the raw materials. The influence of defects in the zeolite on the adsorption and the interaction with MA is discussed. PMID:16456902

Han, Ai-Jie; Guo, Juan; Yu, Hui; Zeng, Yu; Huang, Yue-Fang; He, He-Yong; Long, Ying-Cai

2006-03-13

17

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

18

Modification of surface properties of copper-refractory metal alloys  

DOEpatents

The surface properties of copper-refractory metal (CU-RF) alloy bodies are modified by heat treatments which cause the refractory metal to form a coating on the exterior surfaces of the alloy body. The alloys have a copper matrix with particles or dendrites of the refractory metal dispersed therein, which may be niobium, vanadium, tantalum, chromium, molybdenum, or tungsten. The surface properties of the bodies are changed from those of copper to that of the refractory metal.

Verhoeven, John D. (Ames, IA); Gibson, Edwin D. (Ames, IA)

1993-10-12

19

Size-selective voltammetry: modification of the interface between two immiscible electrolyte solutions by zeolite Y.  

PubMed

Size- and charge-selective ion transfer across the zeolite-Y-modified interface between two immiscible electrolyte solutions (ZM-ITIES) is described. The zeolite-Y membrane is prepared from pressed disks by healing with tetraethyl orthosilicate (TEOS). Size- and charge-selective transfer of the tetraethylammonium cation, size-selective exclusion of tetrabutylammonium cation, and charge-selective exclusion of the tetrafluoroborate and perchlorate anions are demonstrated at the ZM-ITIES. The exclusion studies suggest that the membrane is coherent and contains a low density of pinholes, after healing with TEOS. Various factors affecting the ion transfer such as analyte concentration, supporting electrolyte concentration, and scan rate are investigated. The diffusion coefficient of tetraethylammonium ions within the zeolite-Y pores is found to be on the order of 10(-8) cm2 s(-1). PMID:17279783

Senthilkumar, S; Dryfe, Robert A W; Saraswathi, R

2007-02-06

20

Modification of medical metals by ion implantation of copper  

NASA Astrophysics Data System (ADS)

The effect of copper ion implantation on the antibacterial activity, wear performance and corrosion resistance of medical metals including 317 L of stainless steels, pure titanium, and Ti Al Nb alloy was studied in this work. The specimens were implanted with copper ions using a MEVVA source ion implanter with ion doses ranging from 0.5 × 1017 to 4 × 1017 ions/cm2 at an energy of 80 keV. The antibacterial effect, wear rate, and inflexion potential were measured as a function of ion dose. The results obtained indicate that copper ion implantation improves the antibacterial effect and wear behaviour for all the three medical materials studied. However, corrosion resistance decreases after ion implantation of copper. Experimental results indicate that the antibacterial property and corrosion resistance should be balanced for medical titanium materials. The marked deteriorated corrosion resistance of 317 L suggests that copper implantation may not be an effective method of improving its antibacterial activity.

Wan, Y. Z.; Xiong, G. Y.; Liang, H.; Raman, S.; He, F.; Huang, Y.

2007-10-01

21

Local ammonia storage and ammonia inhibition in a monolithic copper-beta zeolite SCR catalyst  

Microsoft Academic Search

Selective catalytic reduction of NO with NHâ was studied on a Cu-beta zeolite catalyst, with specific focus on the distributed NHâ capacity utilization and inhibition. In addition, several other relevant catalyst parameter distributions were quantified including the SCR zone, or catalyst region where SCR occurs, and NO and NHâ oxidation. We show that the full NHâ capacity (100% coverage) is

Xavier P Auvray; William P Partridge Jr; Jae-Soon Choi; Josh A Pihl; Alex Yezerets; Krishna Kamasamudram; Neal Currier; Louise Olsson

2012-01-01

22

Surface modifications of natural clinoptilolite-dominated zeolite for phenolic pollutant mitigation  

Microsoft Academic Search

A novel carbonized clinoptilolite-rich tuff was studied for phenol removal from water. Zeolite sample carbonization was accomplished\\u000a in a plasmachemical reactor (pyrolytic chamber) using several types of waste, here specifically waste vegetable residues and\\u000a starch. Phenol adsorption experiments were performed in the batch system. An industrial activated charcoal and a clinoptilolite-rich\\u000a tuff hydrofobized with an organic ammonium base were used

E. Chmielewska; K. Pilchowski

2006-01-01

23

A study of copper-exchanged mordenite natural and ZSM-5 zeolites as SCR–NO x catalysts for diesel road vehicles: Simulation by neural networks approach  

Microsoft Academic Search

Copper-catalysts, based on the ZSM-5 (CuZSM5) and Cuban natural Mordenite (CuMORD) zeolites have been prepared by a conventional ion-exchange method and their catalytic activity in the selective catalytic reduction (SCR) of NO was studied using ammonia in presence of H2O and SO2. A commercial catalyst SCR (CATCO) based on V2O5–WO3–TiO2, was also studied as reference. This paper presents experimental results

Mona Lisa Moura de Oliveira; Carla Monteiro Silva; Ramon Moreno-Tost; Tiago Lopes Farias; Antonio Jiménez-López; Enrique Rodríguez-Castellón

2009-01-01

24

Selective catalytic reduction of NO with propene over CuMFI zeolites: dependence on Si\\/Al ratio and copper loading  

Microsoft Academic Search

Selective catalytic reduction of nitrogen oxide by propene in an oxidising atmosphere was studied on several CuMFI catalysts with different Si\\/Al ratios (11 ? Si\\/Al ? 100) and different copper loadings (between 0 and 5.5 wt.-%). From the results it was observed that the influence of zeolite Si\\/Al ratio on CuMFI catalytic activity for NO SCR by propene is dependent

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

1997-01-01

25

Investigation of PCDD/F emissions from mobile source diesel engines: impact of copper zeolite SCR catalysts and exhaust aftertreatment configurations.  

PubMed

This study investigated the impact of copper zeolite selective catalytic reduction (SCR) catalysts and exhaust aftertreatment configurations on the emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from mobile source diesel engines. Emissions of PCDD/Fs, reported as the weighted sum of 17 congeners called the toxic equivalency quotient (TEQ), were measured using a modified EPA Method 0023A in the absence and presence of exhaust aftertreatment. Engine-out emissions were measured as a reference, while aftertreatment configurations included various combinations of diesel oxidation catalyst (DOC), diesel particulate filter (DPF), Cu-zeolite SCR, Fe-zeolite SCR, ammonia oxidation catalyst (AMOX), and aqueous urea dosing. In addition, different chlorine concentrations were evaluated. Results showed that all aftertreatment configurations reduced PCDD/F emissions in comparison to the engine-out reference, consistent with reduction mechanisms such as thermal decomposition or combined trapping and hydrogenolysis reported in the literature. Similarly low PCDD/F emissions from the DOC-DPF and the DOC-DPF-SCR configurations indicated that PCDD/F reduction primarily occurred in the DOC-DPF with no noticeable contribution from either the Cu- or Fe-zeolite SCR systems. Furthermore, experiments performed with high chlorine concentration provided no evidence that chlorine content has an impact on the catalytic synthesis of PCDD/Fs for the chlorine levels investigated in this study. PMID:21446770

Liu, Z Gerald; Wall, John C; Barge, Patrick; Dettmann, Melissa E; Ottinger, Nathan A

2011-02-28

26

Removal of sulfonamide antibiotics from water: Evidence of adsorption into an organophilic zeolite Y by its structural modifications.  

PubMed

Sulfonamide antibiotics are persistent pollutants of aquatic bodies, known to induce high levels of bacterial resistance. We investigated the adsorption of sulfadiazine, sulfamethazine, and sulfachloropyridazine sulfonamides into a highly dealuminated faujasite zeolite (Y) with cage window sizes comparable to sulfonamide dimensions. At maximal solubility the antibiotics were almost completely (>90%) and quickly (t<1min) removed from the water by zeolite. The maximal amount of sulfonamides adsorbed was 18-26% DW of dry zeolite weight, as evidenced by thermogravimetric analyses and accounted for about one antibiotic molecule per zeolitic cage. The presence of this organic inside the cage was revealed by unit cell parameter variations and structural deformations obtained by X-ray structure analyses carried out using the Rietveld method on exhausted zeolite. The most evident deformation effects were the lowering of the Fd-3m real symmetry in the parent zeolite to Fd-3 and the remarkable deformations which occurred in the 12-membered ring cage window after sulfadiazine or sulfachloropyridazine adsorption. After sulfamethazine adsorption, zeolite deformation caused a lowering in symmetry up to the monoclinic P2/m space group. The effective and irreversible adsorption of sulfonamides into organophylic Y zeolite makes this cheap and environmentally friendly material a suitable candidate for removing sulfonamides from water. PMID:20133061

Braschi, Ilaria; Blasioli, Sonia; Gigli, Lara; Gessa, Carlo E; Alberti, Alberto; Martucci, Annalisa

2010-01-18

27

A new active zeolite structure for the selective catalytic reduction (SCR) of nitrogen oxides: ITQ7 zeolite  

Microsoft Academic Search

The activity of a new zeolite material, ITQ7, has been studied for the selective catalytic reduction (SCR) of NO. The pore topology of this material is similar to the structure of a beta zeolite, with a tridirectional system with 12-member rings. ITQ7 exchanged with copper or cobalt shows a catalytic behaviour very similar to a beta zeolite exchanged with copper

Antonio E Palomares; J. G Prato; A Corma

2002-01-01

28

Selective deposition of conductive copper films on glass surfaces using femtosecond laser surface modification and electroless plating  

NASA Astrophysics Data System (ADS)

In this paper, selective deposition of conductive copper films on glass surfaces is demonstrated with the assistance of femtosecond laser surface modification followed by electroless plating. Irradiation of femtosecond laser makes it possible to selectively deposit copper films in the irradiated area on glass surfaces coated with silver nitrate films. The influence of the laser direct writing parameters and the electroless plating process on the formation of copper films is discussed. Meanwhile, the electric properties of copper films are investigated, which confirms that copper films are conductive. A tentative mechanism of the selective deposition process is also proposed. In addition, the potential application of this technique for integrating electrical and thermal functions into microdevices is discussed.

Xu, Jian; Liao, Yang; Zeng, Huidan; Zhou, Zenghui; Sun, Haiyi; Song, Juan; Wang, Xinshun; Cheng, Ya; Xu, Zhizhan; Sugioka, Koji; Midorikawa, Katsumi

2008-03-01

29

Copper  

MedlinePLUS

... form. Copper is often added to vitamin and mineral supplements. But most people are able to get ... arthritis. Today, many multivitamins and other herbal and mineral supplements include copper. What is the evidence? Copper ...

30

Zealous zeolites  

SciTech Connect

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 a specific size and shape. This high selectivity makes zeolites a good alterative to some of the conventional products used for chemical reaction and filtration. One of the most potentially lucrative markets for zeolites is chemical catalyst replacements for liquid acids, such as hydrofluoric acid and sulfuric acid, and aluminum chloride in a number of alkylation and acrylation reactions. Zeolites are also being considered for oligomerization,isomerization, amination and condensation processes for the manufacture of chemical intermediates. The paper discusses the market and manufacturers of zeolites, justifying the cost of converting to zeolite catalysts, and natural zeolites.

Hairston, D.W.

1996-07-01

31

Copper.  

PubMed

Copper is an essential trace element, which is an important catalyst for heme synthesis and iron absorption. Following zinc and iron, copper is the third most abundant trace element in the body. Copper is a noble metal, like silver and gold. Useful industrial properties include high thermal and electrical conductivity, low corrosion, alloying ability, and malleability. Most of the metallic copper appears in electrical applications. Copper is a constituent of intrauterine contraceptive devices and the release of copper is necessary for their contraceptive effects. The average daily intake of copper in the US is about 1 mg Cu with the primary source being the diet. The bioavailability of copper from the diet is about 65-70% depending on a variety of factors including chemical form, interaction with other metals, and dietary components. The biological half-life of copper from the diet is 13-33 days with bilary excretion being the major route of elimination. Copper sulfate is a gastric irritant that produces erosion of the lining of the gastrointestinal tract. Chronic copper toxicity is rare and primarily affects the liver. Wilson's disease and Indian childhood cirrhosis are examples of severe chronic liver disease that results from the genetic predisposition to the hepatic accumulation of copper. The serum copper concentration ranges up to approximately 1.5 mg/L in healthy persons. Gastrointestinal symptoms occur at whole blood concentrations near 3 mg Cu/L. Chelating agents (CaNa2EDTA, BAL) are recommended in severe poisoning, but there are little pharmacokinetic data to evaluate the effectiveness of these agents. PMID:10382557

Barceloux, D G

1999-01-01

32

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

33

Influence of Chemical Surface Characteristics of Natural Zeolite on Catalytic Ozone Abatement  

Microsoft Academic Search

In this article, the effect of zeolite chemical surface properties on gaseous ozone removal was investigated. Zeolite samples with different surface chemical composition were prepared from a Chilean natural zeolite. Such treatments included acid de-alumination, and thermal treatment at 400 °C and 550 °C prior to contact with ozone. Chemical modification of natural zeolite showed that the generation of new

Héctor Valdés; Eder E. Padilla; Claudio A. Zaror

2011-01-01

34

Modification of current-voltage characteristics of planar organic systems by nm-thick copper phthalocyanine or perylene dye interlayer  

NASA Astrophysics Data System (ADS)

The effect of a nm-thick interlayer of copper phthalocyanine (CuPc) or perylene dye (MePTCDI) on currentvoltage characteristics of planar organic systems is discussed in this work. The MePTCDI layer in the ITO/MePTCDI/CuPc/Au system strongly reduces reverse dark current by blocking injection of holes from ITOinto CuPc leading to high values of rectification ratio. The CuPc interlayer in the ITO/CuPc/MePTCDI/Ag system causes a strong reduction in electron injection from ITOand reverses a forward polarity. Modification of current-voltage characteristics of illuminated systems with an interlayer of MePTCDI or CuPc is associated with a strong photovoltaic effect. This results from efficient excition dissociation at the CuPc/MePTCDI interface. Saturation current, determined by this process of charge carrier photogeneration, can be observed at particular voltage polarity.

Signerski, Ryszard; Jarosz, Gra?yna

2013-02-01

35

Copper- and magnesium protoporphyrin complexes inhibit oxidative modification of LDL induced by hemin, transition metal ions and tyrosyl radicals.  

PubMed

The oxidative modification of LDL may play an important role in the early events of atherogenesis. Thus the identification of antioxidative compounds may be of therapeutic and prophylactic importance regarding cardiovascular disease. Copper-chlorophyllin (Cu-CHL), a Cu(2+)-protoporphyrin IX complex, has been reported to inhibit lipid oxidation in biological membranes and liposomes. Hemin (Fe(3+)-protoporphyrin IX) has been shown to bind to LDL thereby inducing lipid peroxidation. As Cu-CHL has a similar structure as hemin, one may assume that Cu-CHL may compete with the hemin action on LDL. Therefore, in the present study Cu-CHL and the related compound magnesium-chlorophyllin (Mg-CHL) were examined in their ability to inhibit LDL oxidation initiated by hemin and other LDL oxidizing systems. LDL oxidation by hemin in presence of H(2)O(2) was strongly inhibited by both CHLs. Both chlorophyllins were also capable of effectively inhibiting LDL oxidation initiated by transition metal ions (Cu(2+)), human umbilical vein endothelial cells (HUVEC) and tyrosyl radicals generated by myeloperoxidase (MPO) in presence of H(2)O(2) and tyrosine. Cu- and Mg-CHL showed radical scavenging ability as demonstrated by the diphenylpicrylhydracylradical (DPPH)-radical assay and estimation of phenoxyl radical generated diphenyl (dityrosine) formation. As assessed by ultracentrifugation the chlorophyllins were found to bind to LDL (and HDL) in serum. The present study shows that copper chlorophyllin (Cu-CHL) and its magnesium analog could act as potent antagonists of atherogenic LDL modification induced by various oxidative stimuli. As inhibitory effects of the CHLs were found at concentrations as low as 1 mumol/l, which can be achieved in humans, the results may be physiologically/therapeutically relevant. PMID:16298745

Kapiotis, Stylianos; Hermann, Marcela; Exner, Markus; Laggner, Hilde; Gmeiner, Bernhard M K

2005-11-01

36

Simultaneous SO{sub 2}/NO{sub x} abatement using zeolite-supported copper. Progress report, April 1--June 30, 1995  

SciTech Connect

Several catalysts for NO decomposition have been reported in the literature to include the following: Cu/ZSM-5; Cu/Zeolite-Y; Cu/mordenite; Cu/{beta} zeolite; Cu/alumina; and Cu/silica which have been studied less than Cu/ZSM-5. The catalytic properties for NO conversion are found to be different on these samples with the ZSM-5 supported catalysts showing the highest activity in a dry environment free from sulfur oxides. One of the goals of this study is to have a better fundamental understanding on the different roles of Cu and the support in the catalytic reaction. The authors use stable, cationic metal complexes in non-aqueous solvents as sources of the Cu ions in producing model catalysts for which the fate of the source molecule is known and is controlled during the ion exchange/impregnation. Molecular models of these systems can be used to identify the possible configurations of the metal complexes within the zeolite support. The authors compare the performance of the model catalysts to one prepared by aqueous impregnation of ZSM-5 zeolite. The performance of the dinuclear metal complex on silica is compared to the same complex in ZSM-5 and Y-zeolites.

Mitchell, M.B.; White, M.G.

1995-12-31

37

Synthesis and Characterization of Copper(II) Complex Nanoparticles ([Cu([18]py}2N4)], [Cu([20]py}2N4)], [Cu(Bzo2[18]py2N4)], [Cu(Bzo2[20]py2N4)]) Encapsulated within the Zeolite-Y  

Microsoft Academic Search

Copper(II) complexes with 18- and 20-membered hexaaza macrocyclic ligands “[Cu([18]py2N4)], [Cu([20]py2N4)], [Cu(Bzo2[18]py2N4)] and [Cu(Bzo2[20]py2N4)]” were entrapped in the nanocavity of zeolite-Y by a two-step process in the liquid phase: (i) adsorption of [bis(diamine)copper(II)] (diamine = 1,2-diaminoethane, 1,3-diaminopropane, 1,2-diaminobenzene, 1,3-diaminobenzene); [Cu(N-N)2]@NaY; within the zeolite, and (ii) in situ template condensation of the copper(II) precursor complex with 2,6-diacetylpyridine. The obtained new complex

Masoud Salavati-Niasari; Fatemeh Davar

2010-01-01

38

Protection of copper corrosion by modification of self-assembled films of Schiff bases with alkanethiol  

Microsoft Academic Search

The corrosion protection of self-assembled films derived from Schiff bases, including N-2-hydroxyphenyl-(3-methoxy-salicylidenimine) (V-bso), N-2-hydroxyphenyl-(salicylidenimine) (S-bso) and N,N?-o-phenylen-bis(salicylidenimine) (S-o-ph-S), on copper surfaces have been probed by electrochemical techniques in an aqueous electrolyte. These studies suggest that the pure films of Schiff bases possess some unfilled defect sites. However, when the films were modified by 1-dodecanethiol (C12H25SH, abbreviated as DT), the quality

Zhenlan Quan; Shenhao Chen; Shulan Li

2001-01-01

39

Plating of Copper Layers on Polyimides Using Electroless Plating by Surface Modification  

NASA Astrophysics Data System (ADS)

This work describes electroless deposition of copper layers onto a polyimide (PI) film. The film was modified by etching with 1.0 M KOH solution treatment, and an activated Ag thin film was developed on this surface using 0.1 M AgNO3. The Cu layers were coated on the activated surface of polyimide films by electroless plating method. The thickness and surface morphology of Cu layers on the PI films were characterized with atomic force microscopy. The surface properties of PI film were identified with contact angle measurements.

Ji, Eun Sun; Kim, Young Hwan; Kang, Yong Cheol; Kang, Young Soo; Ahn, Byung Hyun

40

Preparation and characterization of ton type zeolite catalysts  

Microsoft Academic Search

The reduction of air pollutants emitted at the engine exhaust is an imperative goal for the coming years. The traditional Pt-Rh three-way catalysts are not able to operate in lean burn condition working engines. Copper and cobalt zeolites show high activity and selectivity for both reduction of NOx and hydrocarbon combustion. The TON type zeolite presents a high hydrophobicity and

F. Cosentino; A. Katovic; G Giordano; P. Lentz; J. B. Nagy

1999-01-01

41

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

42

Zeolite advances in the chemical and fuel industries: a technical perspective  

SciTech Connect

New zeolite synthesis and characterization studies reported in 174 publications are reviewed in this article. The review presents a technological perspective for the zeolite advances in the chemical and fuel industries. Particular emphasis is placed on the following aspects: milestones in zeolite catalysis, synthesis, ZSM-type structure, acidity and modification, shape selectivity, and future directions of research. (BLM)

Whyte, T.E. Jr.; Dalla Betta, R.A.

1982-01-01

43

Quantifying defects in zeolites and zeolite membranes  

NASA Astrophysics Data System (ADS)

Zeolites are crystalline aluminosilicates that are frequently used as catalysts to transform chemical feedstocks into more useful materials in a size- or shape-selective fashion; they are one of the earliest forms of nanotechnology. Zeolites can also be used, especially in the form of zeolite membranes (layers of zeolite on a support), to separate mixtures based on the size of the molecules. Recent advances have also created the possibility of using zeolites as alkaline catalysts, in addition to their traditional applications as acid catalysts and catalytic supports. Transport and catalysis in zeolites are greatly affected by physical and chemical defects. Such defects can be undesirable (in the case of zeolite membranes), or desirable (in the case of nitrogen-doped alkaline zeolites). Studying zeolites at the relevant length scales requires indirect experimental methods such as vapor adsorption or atomic-scale modeling such as electronic structure calculations. This dissertation explores both experimental and theoretical characterization of zeolites and zeolite membranes. Physical defects, important in membrane permeation, are studied using physical adsorption experiments and models of membrane transport. The results indicate that zeolite membranes can be modeled as a zeolite powder on top of a support---a "supported powder," so to speak---for the purposes of adsorption. Mesoporosity that might be expected based on permeation and confocal microscopy measurements is not observed. Chemical defects---substitutions of nitrogen for oxygen---are studied using quantum mechanical models that predict spectroscopic properties. These models provide a method for simulating the 29Si NMR spectra of nitrogendefected zeolites. They also demonstrate that nitrogen substitutes into the zeolite framework (not just on the surface) under the proper reaction conditions. The results of these studies will be valuable to experimentalists and theorists alike in our efforts to understand the versatile and complicated materials that are zeolites.

Hammond, Karl Daniel

44

Simultaneous SO{sub 2}/NO{sub x} abatement using zeolite-supported copper. Quarterly progress report, January 1, 1995--March 31, 1995  

SciTech Connect

We have significantly improved on our earlier results with a copper-impregnated alumina, obtaining reproducible results for the impregnation procedure and linear behavior with solution concentration of the precursor. The copper acetylacetonate precursor is adsorbed molecularly onto the alumina surface, with no noticeable decomposition. The adsorbed complex appears to form layers on the alumina surface, similar to results found using the same complex with a silica substrate. The materials start out as light blue powders, and after oxidation are light green. Using infrared spectroscopy, we have examined the in situ adsorption and oxidation of SO{sub 2} on the oxidized sorbent, which is dispersed copper oxide supported on aluminum oxide, and have observed that the initial species formed correspond to aluminum sulfate and aluminum sulfate. The sulfate is formed at temperatures much lower than similar experiments studying SO{sub 2} adsorption on alumina and sodium-doped alumina. As a result of oxidation, the adsorbed sulfur species, which begin as aluminum sulfate and sulfate, are converted to copper sulfate.

Mitchell, M.B.; White, M.G.

1995-12-01

45

Preparation of a Versatile Bifunctional Zeolite for Targeted Imaging Applications  

PubMed Central

Bifunctional zeolite Y was prepared for use in targeted in vivo molecular imaging applications. The strategy involved functionalization of the external surface of zeolite Y with chloropropyltriethoxysilane followed by reaction with sodium azide to form azide-functionalized NaY, which is amenable to copper(1) catalyzed click chemistry. In this study, a model alkyne (4-pentyn-1-ol) was attached to the azide-terminated surface via click chemistry to demonstrate feasibility for attachment of molecular targeting vectors (e.g., peptides, aptamers) to the zeolite surface. The modified particle efficiently incorporates the imaging radioisotope gallium-68 (68Ga) into the pores of the azide-functionalized NaY zeolite to form a stable bifunctional molecular targeting vector. The result is a versatile “clickable” zeolite platform that can be tailored for future in vivo molecular targeting and imaging modalities.

Ndiege, Nicholas; Raidoo, Renugan; Schultz, Michael K.; Larsen, Sarah

2011-01-01

46

Preparation of a Versatile Bifunctional Zeolite for Targeted Imaging Applications.  

PubMed

Bifunctional zeolite Y was prepared for use in targeted in vivo molecular imaging applications. The strategy involved functionalization of the external surface of zeolite Y with chloropropyltriethoxysilane followed by reaction with sodium azide to form azide-functionalized NaY, which is amenable to copper(1)-catalyzed click chemistry. In this study, a model alkyne (4-pentyn-1-ol) was attached to the azide-terminated surface via click chemistry to demonstrate feasibility for attachment of molecular targeting vectors (e.g., peptides, aptamers) to the zeolite surface. The modified particle efficiently incorporates the imaging radioisotope gallium-68 ((68)Ga) into the pores of the azide-functionalized NaY zeolite to form a stable bifunctional molecular targeting vector. The result is a versatile "clickable" zeolite platform that can be tailored for future in vivo molecular targeting and imaging modalities. PMID:21306141

Ndiege, Nicholas; Raidoo, Renugan; Schultz, Michael K; Larsen, Sarah

2011-02-01

47

Ring conversion of ?-butyrolactone into N-methyl-2-pyrrolidone over modified zeolites  

Microsoft Academic Search

Catalytic activities of metal ion exchanged zeolites for the ring conversion of ?-butyrolactone (GBL) with methylamine (MA) into N-methyl-2-pyrrolidone (NMP) were investigated using a continuous fixed bed reactor system. Among the zeolites tested, cation exchanged Na-BEA zeolite was more active than cation exchanged Na-X or Na-Y. Copper or calcium ion exchanged catalysts showed the highest yield among the cation exchanged

Young-Seek Yoon; Hyun Khil Shin; Byong-Sung Kwak

2002-01-01

48

Zeolite-based materials for the selective catalytic reduction of NO x with hydrocarbons  

Microsoft Academic Search

This review covers all aspects of the selective catalytic reduction of nitrogen oxides with hydrocarbons (HC-SCR) over zeolite catalysts, mainly from the viewpoint of their potential for a practical application in exhaust gases from lean-burn engines. Emphasis is placed on HC-SCR over metal-containing zeolites with the exception of copper zeolites. Other items which are addressed are the combination of various

Yvonne Traa; Beate Burger; Jens Weitkamp

1999-01-01

49

Methods of using structures including catalytic materials disposed within porous zeolite materials to synthesize hydrocarbons  

DOEpatents

Catalytic structures include a catalytic material disposed within a zeolite material. The catalytic material may be capable of catalyzing a formation of methanol from carbon monoxide and/or carbon dioxide, and the zeolite material may be capable of catalyzing a formation of hydrocarbon molecules from methanol. The catalytic material may include copper and zinc oxide. The zeolite material may include a first plurality of pores substantially defined by a crystal structure of the zeolite material and a second plurality of pores dispersed throughout the zeolite material. Systems for synthesizing hydrocarbon molecules also include catalytic structures. Methods for synthesizing hydrocarbon molecules include contacting hydrogen and at least one of carbon monoxide and carbon dioxide with such catalytic structures. Catalytic structures are fabricated by forming a zeolite material at least partially around a template structure, removing the template structure, and introducing a catalytic material into the zeolite material.

Rollins, Harry W. (Idaho Falls, ID); Petkovic, Lucia M. (Idaho Falls, ID); Ginosar, Daniel M. (Idaho Falls, ID)

2011-02-01

50

Zeolite collapse and polyamorphism  

Microsoft Academic Search

The phenomenology of zeolite collapse is outlined, drawing on recent synchrotron x-ray diffraction experiments and computer simulations of low density cage structures like zeolite A and zeolite Y. Attention is drawn to the importance of polyamorphism in destabilizing this type of microporous crystal and its role in order disorder as well as amorphous amorphous transitions, together with associated differences in

G. Neville Greaves; F. Meneau; F. Kargl; D. Ward; P. Holliman; F. Albergamo

2007-01-01

51

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...

52

Zeolite catalysis: technology  

SciTech Connect

Zeolites have been used as catalysts in industry since the early nineteen sixties. The great majority of commercial applications employ one of three zeolite types: zeolite Y; Mordenite; ZSM-5. By far the largest use of zeolites is in catalytic cracking, and to a lesser extent in hydrocracking. This paper reviews the rapid development of zeolite catalysis and its application in industries such as: the production of gasoline by catalytic cracking of petroleum; isomerization of C/sub 5/ and C/sub 6/ paraffin hydrocarbons; alkylation of aromatics with olefins; xylene isomerization; and conversion of methanol to gasoline.

Heinemann, H.

1980-07-01

53

Effects of Surface Modifications on the Peel Strength of Copper Based Polymer\\/Metal Interfaces with Characteristic Morphologies  

Microsoft Academic Search

This paper summarizes a study on the effect of changes in surface chemistry on the peel strength of copper\\/polymer interfaces. Two different surface topographics were created and evaluated, one produced by cleaning and etching in sodium persulfate, the other by etching then mechanically roughening using 180 grit sandpaper. Both surfaces were then oxidized in an alkaline\\/oxidizing treatment to form cupric

B. J. Love; P. F. Packman

1993-01-01

54

Artificial neural network model in surface modification by EDM using tungsten–copper powder metallurgy sintered electrodes  

Microsoft Academic Search

Electro-discharge machining (EDM) is a widely accepted nontraditional machining process used mostly for machining materials\\u000a difficult to machine by conventional shearing process. Surface modification by powder metallurgy sintered tools is an uncommon\\u000a aspect of EDM. Of late, it is being explored by many researchers. In the present paper, attempts have been made to model the\\u000a surface modification phenomenon by EDM

Promod Kumar Patowari; Partha Saha; P. K. Mishra

2010-01-01

55

Theoretical investigation of CO interaction with copper sites in zeolites: periodic DFT and hybrid quantum mechanical/interatomic potential function study.  

PubMed

Periodic DFT and combined quantum mechanics/interatomic potential function (QM-pot) models were used to describe the interaction of CO with the Cu+ sites in FER. The CO stretching frequencies were calculated using omega(CO)(CCSD(T))/r(CO)(DFT) scaling method relating frequencies determined using a high-level quantum-chemical (coupled clusters) method for simple model carbonyls to CO bond lengths calculated using periodic DFT and QM-pot methods for the Cu+-zeolite system. Both periodic DFT and QM-pot models together with omega(CO)/r(CO) scaling describe the CO stretching dynamics with the "near spectroscopic accuracy", giving nu(CO) = 2156 cm(-1) in excellent agreement with experimental data. Calculations for various Cu+ sites in FER show that both types of Cu+ sites in FER (channel-wall sites and intersection sites) have the same CO stretching frequencies. Thus, the CO stretching frequencies are not site-specific in the CO/Cu+/FER system. The convergence of the results with respect to the model size was analyzed. When the same exchange-correlation functional is used the adsorption energies from periodic DFT and QM-pot are in good agreement (about 2 kcal/mol difference) but substantially larger than those of the experiment. The adsorption energy calculated with the B3LYP functional agrees with available experimental data. The overestimation of the adsorption energy in DFT calculations (periodic or QM-pot) is related to a red-shift of the CO stretching mode, both result from an underestimation of the HOMO(5sigma)-LUMO(2pi) gap of CO and the consequent overestimation of the Cu(+)(d)-CO(2pi*) back-donation. For the adsorption energy, this can be overcome by the use of hybrid B3LYP exchange-correlation functional. For the frequency calculations, the DFT problem can be overcome by the use of the omega(CO)(CCSD(T))/r(CO)(DFT) correlation. PMID:16852159

Bludský, Ota; Silhan, Martin; Nachtigall, Petr; Bucko, T; Benco, L; Hafner, J

2005-05-19

56

Zeolite membranes from kaolin  

SciTech Connect

Zeolite films are sought as components of molecular sieve membranes. Different routes used to prepare zeolite composite membranes include growing zeolite layers from gels on porous supports, depositing oriented zeolites on supports, and dispersing zeolites in polymeric membranes. In most cases, it is very difficult to control and avoid the formation of cracks and/or pinholes. The approach to membrane synthesis is based on hydrothermally converting films of layered aluminosilicates into zeolite films. The authors have demonstrated this concept by preparing zeolite A membranes on alumina supports from kaolin films. The authors have optimized the process parameters not only for desired bulk properties, but also for preparing thin (ca. 5 {micro}m), continuous zeolite A films. Scanning electron microscopy shows highly intergrown zeolite A crystals over most of the surface area of the membrane, but gas permeation experiments indicate existence of mesoporous defects and/or intercrystalline gaps. It has been demonstrated that the thickness of the final zeolite A membrane can be controlled by limiting the amount of precursor kaolin present in the membrane.

Karle, B.G. [Univ. of New Mexico, Albuquerque, NM (United States). Center for Micro-Engineered Ceramics; Brinker, C.J. [Univ. of New Mexico, Albuquerque, NM (United States). Center for Micro-Engineered Ceramics]|[Sandia National Labs., Albuquerque, NM (United States); Phillips, M.L.F. [Sandia National Labs., Albuquerque, NM (United States)

1996-07-01

57

The interface formation of copper and low dielectric constant fluoro-polymer: Plasma surface modification and its effect on copper diffusion  

NASA Astrophysics Data System (ADS)

The bulk and surface diffusion of Cu deposited on a treated low dielectric constant fluoropolymer (FLARE™ 1.0, AlliedSignal) was studied using x-ray photoelectron spectroscopy. Copper was found to be relatively unreactive on untreated, N2 and O2 plasma treated, and Ar+ sputtered surfaces. Shifts in the Cu 2p3/2 binding energy showed that larger Cu islands formed when Cu was evaporated on the untreated surface. Because sputter deposition of Cu damaged the fluoropolymer and formed nucleation sites for Cu islands, many smaller islands were found for Cu sputter deposited on untreated polymer. The competition between bulk and surface diffusion also plays a role in Cu island size: Plasma treatments and sputtering limit diffusion of Cu into the bulk of the polymer below the glass transition temperature Tg. The plasma treatments increase the surface reactivity and the plasma treatments and sputtering increase the cross linking in the surface region. Above Tg, no treatment was found to effectively limit diffusion into the bulk. Bulk diffusion during Cu deposition, however, is found to limit island size.

Du, M.; Opila, R. L.; Donnelly, V. M.; Sapjeta, J.; Boone, T.

1999-02-01

58

Modification of jet-properties in ultrarelativistic deuteron+gold, copper+copper, and gold+gold collisions at center of mass energy = 200GeV  

NASA Astrophysics Data System (ADS)

A transition from hadronic matter to a plasma of deconfined quarks and gluons (QGP) is predicted to occur for energy densities epsilon ? 0.6--1.0 GeV/fm3 [Kar02] by Quantum Chromodynamics (QCD), the theory of strong interactions. Such a plasma is believed to have existed only a few mus after the Big Bang. The production and study of the QGP is the subject of very intense research currently undertaken at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. Prior to fragmentation into a jet of hadrons, a hard scattered parton can lose energy as it propagates through the high energy density matter formed in heavy ion collisions at RHIC. This energy loss is expected to be sensitive to several properties of the medium including its gluon density, formation time and the path length traversed. The energy loss also results in the modification of jet topologies and yields which in turn serve as a powerful tomographic short-wavelength probe of the collision medium. In this work, the method of two-particle azimuthal correlation functions is used to measure the correlations due to jets and elliptic flow in d+Au, Cu+Cu and Au+Au collisions at sNN = 200GeV. The jet correlations measured in Cu+Cu and Au+Au collisions, are separated via a novel decomposition technique to obtain the jet associated particles per trigger hadron. These distributions show evidence for strong centrality dependent shape modifications for particles of intermediate transverse momentum produced in Cu+Cu and Au+Au collisions but not for d+Au. They also indicate that jet associated protons and mesons (pions and kaons) are similarly modified by the medium. This discovery is compatible with several recent theoretical predictions for jet modification in a strongly interacting QGP, including the formation of jet-induced "mach cones", reminiscent of the sonic boom produced in a fluid when the speed of sound is exceeded. These new experimental results provide an important basis for further study of the transport properties of the high energy density matter produced in heavy ion collisions at RHIC.

Holzmann, Wolf Gerrit

59

Zeolite collapse and polyamorphism  

NASA Astrophysics Data System (ADS)

The phenomenology of zeolite collapse is outlined, drawing on recent synchrotron x-ray diffraction experiments and computer simulations of low density cage structures like zeolite A and zeolite Y. Attention is drawn to the importance of polyamorphism in destabilizing this type of microporous crystal and its role in order disorder as well as amorphous amorphous transitions, together with associated differences in entropy and density between polyamorphic phases and the precursor zeolite. Magic angle spinning NMR and inelastic x-ray scattering are used to highlight changes in structural order and mechanical rigidity between the starting zeolite and the final high density polyamorph. In conclusion, two-level systems detected with inelastic neutron scattering are described and their involvement in dictating the dynamics of the collapse of zeolitic cage structures.

Neville Greaves, G.; Meneau, F.; Kargl, F.; Ward, D.; Holliman, P.; Albergamo, F.

2007-10-01

60

Sequential color change on copper surfaces via micro/nano structure modification induced by a picosecond laser  

NASA Astrophysics Data System (ADS)

A surface micro/nano structuring technique was demonstrated for colorizing metal surfaces with a picosecond laser. Sequential color change from black to pink was realized on copper surfaces by simply changing the ps laser scanning speeds. Systematic analyses on the spectral response and microstructure characteristics were reported. The spectrum shifting effect corresponding to color change was explained through the surface plasmon resonance mechanism. The current research shows that a high power and high repetition rate ps laser is capable of structuring metal surfaces with a speed up to several meters per second, presenting an efficient and affordable candidate for practical industrial applications.

Fan, Peixun; Zhong, Minlin; Li, Lin; Schmitz, Patrick; Lin, Cheng; Long, Jiangyou; Zhang, Hongjun

2013-08-01

61

Determination of copper binding in Pseudomonas putida CZ1 by chemical modifications and X-ray absorption spectroscopy  

Microsoft Academic Search

Previously performed studies have shown that Pseudomonas putida CZ1 biomass can bind an appreciable amount of Cu(II) and Zn(II) ions from aqueous solutions. The mechanisms of Cu- and Zn-binding\\u000a by P. putida CZ1 were ascertained by chemical modifications of the biomass followed by Fourier transform infrared and X-ray absorption\\u000a spectroscopic analyses of the living or nonliving cells. A dramatic decrease

XinCai Chen; JiYan Shi; YingXu Chen; XiangHua Xu; LiTao Chen; Hui Wang; TianDou Hu

2007-01-01

62

Effect of soil ph modification on DTPA?extractable copper, manganese, and zinc in a northern Idaho soil  

Microsoft Academic Search

Soils in the Kootenai River Valley of northern Idaho are both high in organic matter and pH (>7.0). This combination causes a tendency for crops to exhibit micronutrient deficiencies. Since soil pH is a dominant factor affecting micronutrient availability in soils, this study was designed to: (1) evaluate the effect of amendments [elemental S and Ca(OH)2] on soil pH modification

G. C. Li; R. L. Mahler

1993-01-01

63

Modification on the melting of aluminum nanoclusters by a copper atom: heat capacities of CuAln-1^- nanoalloys  

NASA Astrophysics Data System (ADS)

The melting of alloyclusters is currently of great interest and emerging as an important research area. In this talk, we report the synthesis and melting transition of CuAln-1^- nanoalloy clusters (n = 49 -- 62). Heat capacities and melting behaviors have been determined for CuAln-1^- nanoalloy clusters using a novel collision induced dissociation method and are compared with those of pure aluminum cluster Aln^+. All these nanoalloys present a first order melting transition at temperatures well-below the melting temperature of the bulk aluminum and the eutectic temperature of their bulk alloys. No eutectic characteristic is detected for these nanoalloyclusters. Upon substitution of Al with a single copper atom, the melting of pure aluminum clusters has been altered considerably. Size and charge effects of the doping atom on the melting of host nanoclusters are discussed.

Cao, Baopeng; Neal, Colleen M.; Starace, Anne M.; Jarrold, Martin F.

2008-03-01

64

Sodium clusters in zeolites  

NASA Astrophysics Data System (ADS)

The method of loading sodium clusters in zeolites, consisting of the controlled thermal decomposition of physisorbed sodium azide, is discussed. The influence of the azide loading, the azide decomposition rate and the sintering process on the amount of ionic and metallic sodium clusters in zeolite Y was followed by ESR. The method is compared to other metal deposition techniques.

Grobet, P. J.; Martens, L. R. M.; Vermeiren, W. J. M.; Huybrechts, D. R. C.; Jacobs, P. A.

1989-03-01

65

Structural modification on copper(I)-pyridylpyrimidine complexes for modulation of rotational dynamics, redox properties, and phototriggered isomerization.  

PubMed

The redox properties of copper pyridylpyrimidine complexes, which undergo linkage isomerism based on pyrimidine ring rotation, were compared under different coordination environments. A newly synthesized compound, [Cu(Mepypm)(L(Mes))]BF4 (1·BF4, Mepypm = 4-methyl-2-(2'-pyridyl)pyrimidine, L(Mes) = 2,9-dimesityl-1,10-phenanthroline) was compared with previously reported complexes of [Cu(MepmMepy)(L(Mes))]BF4 (2·BF4, MepmMepy = 4-methyl-2-(6'-methyl-2'-pyridyl)pyrimidine), Cu(Mepypm)(DPEphos)]BF4 (3·BF4, DPEphos = bis[2-(diphenylphosphino)phenyl]ether), [Cu(Mepypm)(L(Anth))]BF4 (4·BF4, L(Anth) = 2,9-bis(9-anthryl)-1,10-phenanthroline), and [Cu(Mepypm)(L(Macro))]BF4 (5·BF4). Isomer ratios, isomerization dynamics, redox properties, and photoelectron conversion functions varied with the coordination structure. Methyl substituents on the 6-position of the pyridine moiety increased steric repulsion and contributed to quicker rotation, enhanced photoluminescence, and increased photodriven rotational isomerization. PMID:23883176

Nishikawa, Michihiro; Takara, Yusuke; Hattori, Yohei; Nomoto, Kuniharu; Kusamoto, Tetsuro; Kume, Shoko; Nishihara, Hiroshi

2013-07-24

66

Modification and Catalytic Application of Zeolite Beta.  

National Technical Information Service (NTIS)

The Dutch Institute for Catalysis Research (NIOK) subsidises the catalysis research efforts conducted at national universities and gives impetus to the development of more environmentally benign and more efficient chemical production processes. The resear...

P. Kunkeler

1998-01-01

67

Characterization of lead sorption by the natural and Fe(III)-modified zeolite  

NASA Astrophysics Data System (ADS)

The influence of contact time, temperature and particle size on lead sorption by the natural and Fe(III)-modified zeolites was investigated. Characterization of the natural and Fe(III)-modified zeolite before and after lead sorption was performed by determination of textural properties, by scanning electron microscopy and X-ray spectroscopy in energy-dispersive mode (SEM–EDS), transmission electron microscopy (TEM) and X-ray powder diffraction (XRPD) analysis. Lead sorption kinetics at 303–333 K, best represented by the pseudo-second order model and activation energy (13.5 and 8.5 kJ/mol for the natural and Fe(III)-modified zeolite respectively) confirmed an activated chemical sorption. Desorption experiments indicated that lead was irreversibly sorbed on both zeolites. XRPD, TEM and SEM results showed that modification of the natural zeolite with Fe(III) ions did not change its crystal structure and iron is mainly located at the zeolite surface, likely in form of amorphous iron oxy-hydroxides. Specific surface area significantly increases after modification of the natural zeolite with Fe(III) ions (from 30.2 for the natural to 52.5 m2/g for Fe(III)-modified zeolite). Characterization of both lead saturated sorbents suggested that besides ion exchange, lead is both chemisorbed and precipitated at their surfaces, and presence of amorphous iron in Fe(III)-modified zeolite favors sorption of lead.

Kragovi?, Milan; Dakovi?, Aleksandra; Markovi?, Marija; Krsti?, Jugoslav; Gatta, G. Diego; Rotiroti, Nicola

2013-10-01

68

Development of low-cost integrated zeolite collector, supplement  

NASA Astrophysics Data System (ADS)

A low cost zeolite collector was built and the experimental data from the collectors at the different test sites in the USA were analyzed. The suitability of different methods of corrosion protection of low cost materials was studied. It is found that the phenolic coating which is suitable is more expensive than the copper it replaces. Fiber glass epoxy is suitable as a container material for the zeolite, however, there are some problems with the vacuum seal due to the mismatch of thermal expansion coefficients. Low cost collectors were constructed and tested. Cost reduction of a factor of six is possible in mass production.

Tchernev, D. I.

1983-02-01

69

Properties of Natural Zeolites.  

National Technical Information Service (NTIS)

Samples of the naturally occuring zeolites phillipsote, clinoptilolite, erionite, and chabazite have been surveyed for their gas adsorption, ion exchange, and other characteristics. Chabazite and erionite, which are generally more stable, also have higher...

R. A. Munson

1973-01-01

70

Selective sorption by zeolites  

SciTech Connect

An improved adsorptive separation process by the selective sorption properties of certain members of a novel class of zeolites is provided. The novel class of zeolites is characterized by a silica to alumina mole ratio greater than 12 and a Constraint Index within the approximate range of greater than 2 to about 12. The process of this invention involves selective separation of waxy paraffinic compounds in admixture with stocks containing paraffinic compounds, e.g. crude oils, heavy oils, distillate oils and lube base oils, by contacting the mixture with a zeolite having a SiO/sub 2//Al/sub 2/O/sub 3/ mole ratio of at least about 12 and a Constraint Index within the range of greater than 2 to about 12 to effect the selective sorption of said waxy paraffinic compounds by said zeolite.

Dessau, R.M.

1984-05-15

71

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

72

Zeolites for reforming catalysts  

Microsoft Academic Search

This patent describes a reforming catalyst exhibiting enhanced selectivity, activity, and activity maintenance. It comprises: zeolite crystals having a pH within the range of 9.4 to 10.0, wherein the pH is determined by measuring pH of supernatent liquid from a mixture of one part of the zeolite crystals with ten parts of dionized water by weight, and comprising exchangeable cations

J. L. Kao; M. Nadler; M. J. Potter; R. V. Martir

1991-01-01

73

Analysis of results of studies of modified type NaA zeolites for cryogenic removal of oxygen from argon  

Microsoft Academic Search

With the goal of designing systems for removal of oxygen from argon for high-capacity air-fractionatin g equipment, an integrated set of investigations has been carried out on the adsorption properties of modified type NaA zeolites [i-5]. As a result of investigation of the dynamics of adsorption of oxygen by modified samples of type NaA zeolites, we determined modifications of zeolites

A. N. Fedorov

1992-01-01

74

Bromides in zeolite synthesis \\/ zeolites in bromide synthesis and conversion  

Microsoft Academic Search

Quaternary ammonium bromides and hydroxides (quats) are applied as templates in the synthesis of zeolites with relatively high Si\\/Al ratio. Examples will be given of the use of mon-, di-, poly- and associated quats as templates in zeolite growth. Templated zeolites of the MFI-type can be grown in a lateral or in an axial way onto metal supports, providing promising

H. Van Bekkum

1995-01-01

75

Preparation of functionalized zeolitic frameworks  

SciTech Connect

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

76

The influence of zeolitic water on the rate of butadiene dimerization  

SciTech Connect

Zeolites find widespread usage as catalysts for a variety of chemical transformations. Frequently, the catalytically active agent is a transition metal ion located at an exchange site in contact with the zeolitic surface. Although the extraframework cation positions and relative populations can often be determined by spectroscopic methods, the influence of cation sitting and adsorbed reactant induced migration under reaction conditions is less well understood. This note describes the role which water exerts on the activity of copper-exchanged zeolite Y for the dimerization of butadiene to 4-vinylcyclohexene (4-VCH). 12 refs., 1 fig., 1 tab.

NONE

1995-02-01

77

Adamantanes from petroleum with zeolites  

Microsoft Academic Search

Experiments with zeolite Beta and zeolite Y demonstrate that adamantane and methyl adamantanes can be isolated very effectively from modern refinery streams by mild hydrocracking over Pt-and Pd-containing large pore zeolites. Yield depends importantly on individual refinery crude source and process configuration. Heavy crudes and refineries with conventional hydrocracking and FCC feed hydrotreater facilities are particularly desirable, and an ideal

L. Deane Rollmann; Larry A. Green; Robert A. Bradway; Hye Kyung C. Timken

1996-01-01

78

Zeolite-Hydraulic Cement Containment Medium.  

National Technical Information Service (NTIS)

The invention generally relates to a zeolite-hydraulic cement containment medium for hazardous wastes. In particular, the invention relates to a process for preparing a zeolite-portland cement containment medium from a paste prepared by mixing zeolite in ...

P. M. Brown M. A. Maginnis C. R. Furlong M. G. Bakker G. L. Turner

1994-01-01

79

Novel modified zeolites for energy-efficient hydrocarbon separations.  

SciTech Connect

We present synthesis, characterization and testing results of our applied research project, which focuses on the effects of surface and skeletal modification of zeolites for significant enhancements in current hydrocarbon (HC) separations. Zeolites are commonly used by the chemical and petroleum industries as catalysts and ion-exchangers. They have high potential for separations owing to their unique pore structures and adsorption properties and their thermal, mechanical and chemical properties. Because of zeolites separation properties, low cost, and robustness in industrial process, they are natural choice for use as industrial adsorbents. This is a multidisciplinary effort to research, design, develop, engineer, and test new and improved materials for the separation of branched vs. linear organic molecules found in commercially important HC streams via adsorption based separations. The focus of this project was the surface and framework modification of the commercially available zeolites, while tuning the adsorption properties and the selectivities of the bulk and membrane separations. In particular, we are interested with our partners at Goodyear Chemical, on how to apply the modified zeolites to feedstock isoprene purification. For the characterization and the property measurements of the new and improved materials powder X-ray diffraction (PXRD), Residual Gas Analyzer-Mass Spectroscopy (RGA-MS), Electron Microscopy (SEM/EDAX), temperature programmed desorption (TPD) and surface area techniques were utilized. In-situ carbonization of MFI zeolite membranes allowed for the maximum separation of isoprene from n-pentane, with a 4.1% enrichment of the binary stream with n-pentane. In four component streams, a modified MFI membrane had high selectivities for n-pentane and 1-3-pentadiene over isoprene but virtually no separation for the 2-methyl-2-butene/isoprene pair.

Arruebo, Manuel (University of Colorado, Boulder, CO); Dong, Junhang; Anderson, Thomas (Burns and McDonnell, Kansas City, MO); Gu, Xuehong; Gray, Gary (Goodyear Chemical Company, Akron, OH); Bennett, Ron (Goodyear Chemical Company, Akron, OH); Nenoff, Tina Maria; Kartin, Mutlu; Johnson, Kaylynn (Goodyear Chemical Company, Akron, OH); Falconer, John (University of Colorado, Boulder, CO); Noble, Richard (University of Colorado, Boulder, CO)

2006-11-01

80

Gas chromatography on zeolites using moist carrier gas  

SciTech Connect

Ion-exchangeable forms of dehydrated zeolites are widely used adsorbents for isolation, concentration and gas chromatographic determination of a variety of air pollutants. The authors thought it of interest to study gas chromatographic properties of molecular sieves using moistened carrier gas, assuming that modification of zeolites by water can markedly influence their properties by changing the selectivity and efficiency of separation. The goal of this report was a systematic study of the chromatographic behavior of organic and also oxygen and nitrogen containing gases using controlled humidification of KY zeolite and carrier gas over a wide range of temperature (40-300/sup 0/C) and relative humidity (0-100% at 20/sup 0/C). The KY sample was prepared from powdered zeolite (part Nay P-1298) with 89% substitution of the sodium by potassium cations by multiple treatment with a 0.1 M solution of potassium chloride. Increase of partial water vapor pressure in zeolite-adsorbate systems leads to decreased separation of the eluted materials and also influences the separation efficiency and causes a narrowing of chromatographic bands.

Banakh, O.S.; Berezkin, V.G.; Ya Golos, I.

1986-08-01

81

Characterization of zeolite L nanoclusters  

Microsoft Academic Search

Zeolite L (structure code LTL) crystals are synthesized starting from homogeneous potassium aluminosilicate solutions. Particle size and shape of the formed zeolite L are examined by high-resolution transmission electron microscopy, field emission-scanning electron microscopy, X-ray diffraction, and dynamic light scattering. The synthesis conditions reported lead to nanoclusters of aligned zeolite crystalline domains of dimensions â¼40 nm in the channel direction

Michael Tsapatsis; Mark Lovallo; Masayoshi Sadakata; Mark E. Davis

1995-01-01

82

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

83

Thermally stable chromium-exchanged zeolites and method of making same  

SciTech Connect

A method is described of making a thermally stable Cu-Cr zeolite, said method comprising: (a) providing a Y zeolite having an alkali content of less than about 0.5% by weight based on the oxide, and having a SiO[sub 2] to Al[sub 2]o[sub 3] mole ratio of about 3 to about 200, and copper and chromium ions exchanged therein, wherein said alkali content is provided at least before the Cr ions are exchanged therein, the weight ratio of Cu:Cr being about 1:1 to about 1:4; and (b) heat-treating said Cu-Cr-exchanged zeolite to produce said thermally stable Cu-Cr zeolite wherein the BET surface area of said thermally stable zeolite upon exposure to temperatures of up to about 1000 C is at least about 50% of the BET surface area of said starting zeolite at about room temperature, prior to said exposure to temperatures of up to about 1,000 C. A Cu-Cr-exchanged zeolite produced by the method of claim 1 is also described.

Swaroop, S.H.; Wusirika, R.R.

1993-08-10

84

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

85

Metallo-hydrazone complexes immobilized in zeolite Y: Synthesis, identification and acid violet-1 degradation  

NASA Astrophysics Data System (ADS)

Copper(II), cobalt(II) and nickel(II) complexes of hydrazone ligand (SAPH) derived from salicylaldehyde and phenylhydrazine have been encapsulated in zeolite-Y super cages via ship-in-a-bottle synthesis. Detailed characterization of the intrazeolitic complexes were performed by elemental analysis, spectral (FT-IR, UV-Vis.) studies, magnetic measurements and X-ray diffraction. Furthers, surface texture and thermal analysis (TG, DTG, DTA) have provided further evidence for successful immobilization of the metal complexes inside zeolite Y. Investigation of the stereochemistry of these incorporated chelates pointed out that, SAPH ligand is capable to coordinate with the central metal through the (CN), phenolic (OH) and (NH) groups forming polynuclear structures. The involvement of zeolite oxygen in coordination was postulated in the hybrid materials. The intrazeolitic copper, cobalt and nickel-SAPH complexes have distorted tetrahedral, octahedral and square-pyramidal configurations, respectively. The zeolite encapsulated complexes are thermally stable up to 800 °C except Cu(II) sample which is thermally stable up to midpoint 428 °C. The assessment of the catalytic activity was performed by the use of the photo-degradation of acid violet-1 dye as a probe reaction in presence of H2O2 as an oxidant. Decolorization of acid violet-1 dye was examined under the same conditions whereas the unpromoted zeolite and CuII, CoII, NiII-hydrazone complexes supported on zeolite showed 13% and 76%, 53%, 43% color removal, respectively. The results revealed that, the zeolite encapsulated Cu(II) complex generally exhibited better catalytic efficiency (76%) compared with other investigated zeolite encapsulated metal-hydrazone samples.

Ahmed, Ayman H.; Thabet, M. S.

2011-12-01

86

Two stage process for improving the catalyst life of zeolites in the synthesis of lower olefins from alcohols and their ether derivatives  

SciTech Connect

A process is described for converting an alcohol and/or ether feed as hereinafter defined to a hydrocarbon mixture rich in olefins which comprises contacting, under conversion conditions at a conversion reaction temperature of from about 300/sup 0/ to 350/sup 0/C., a feed comprising one or more monohydric alcohols having from about 1 to about 4 carbon atoms, ethers derived therefrom, or mixtures of the alcohols and ethers, with a modified crystalline metalosilicate shape selective acidic zeolite. The metalosilicate is selected from the group consisting of aluminum, gallium, and mixtures thereof, and the zeolite, prior to modification and in the absence of any coke deposited thereon, possesses: (a) the capability of catalyzing the alcohol and/or other conversion reaction; (b) a channel size and structure such as to permit (i) entry of the feed into the zeolite and diffusion to the active acid sites within the zeolite, and (ii) formation of olefin products within the zeolite and diffusion of the products out of the zeolite; and (c) hydrothermal stability at temperatures of at least about 290/sup 0/C. The modification of the zeolite is conducted in a manner sufficient to increase the catalyst life of the zeolite, relative to the absence of the modification when the zeolite is employed as a catalyst for the alcohol and/or ether conversion reaction.

Pieters, W.J.M.; Okumura, Y.

1987-01-20

87

A novel catalyst with high activity for polyhydric alcohol oxidation: nanosilver/zeolite film.  

PubMed

A novel catalyst of silver nanoparticles over a zeolite film-coated copper grid (SZFC) has been fabricated via an in situ electrolytic method; it exhibited high catalytic activity and selectivity at a relatively low temperature for the partial oxidation of 1,2-propylene glycol to methyl glyoxal. PMID:15599453

Shen, Jiang; Shan, Wei; Zhang, Yahong; Du, Junming; Xu, Hualong; Fan, Kangnian; Shen, Wei; Tang, Yi

2004-11-15

88

Resonant diffusion of normal alkanes in zeolites: effect of the zeolite structure and alkane molecule vibrations  

Microsoft Academic Search

Diffusion of normal alkanes in one-dimensional zeolites is theoretically studied on the basis of the stochastic equation formalism. The calculated diffusion coefficient accounts for the vibrations of the diffusing molecule and zeolite framework, molecule-zeolite interaction, and specific structure of the zeolite. It is shown that when the interaction potential is predominantly determined by the zeolite pore structure, the diffusion coefficient

Roumen Tsekov; Panagiotis G. Smirniotis

1998-01-01

89

Improved zeolitic isocracking catalysts  

SciTech Connect

Chevron Research Company introduced the first low pressure, low temperature catalytic hydrocracking process--ISOCRACKING--in 1959. Within the last four years, Chevron has developed and commercialized three new zeolitic ISOCRACKING catalysts. ICR 209 is Chevron`s latest noble metal ISOCRACKING catalyst. It offers improved liquid yield stability, longer life, and superior polynuclear aromatics control compared to its predecessor. ICR 209`s high hydrogenation activity generates the highest yields of superior quality jet fuel of any zeolitic ISOCRACKING catalyst. The second new ISOCRACKING catalyst, ICR 208, is a base metal catalyst which combines high liquid selectivity and high light naphtha octane in hydrocrackers operating for maximum naphtha production. ICR 210 is another new base metal catalyst which offers higher liquid yields and longer life than ICR 208 by virtue of a higher hydrogenation-to-acidity ratio. Both ICR 208 and ICR 210 have been formulated to provide higher liquid yield throughout the cycle and longer cycle length than conventional base metal/zeolite catalysts. This paper will discuss the pilot plant and commercial performances of these new ISOCRACKING catalysts.

Dahlberg, A.J.; Habib, M.M.; Moore, R.O. [Chevron Research and Technology Co., Richmond, CA (United States); Law, D.V. [Chevron International Oil Co., San Francisco, CA (United States); Convery, L.J. [ABB Lummus Crest, Bloomfield, NJ (United States)

1995-09-01

90

Parameters influencing zeolite incorporation in PDMS membranes  

Microsoft Academic Search

The incorporation of several types of zeolite in PDMS membranes is studied, by measuring the tensile strength, xylene sorption, and density of the membranes. The zeolite is shown to be involved in the cross-linking of the membrane. The interaction between the PDMS matrix and the zeolites results in reinforced membranes in the case of zeolite Y. The parameters influencing the

Ivo F. J. Vankelecom; Else Scheppers; Robin Heus; Jan B. Uytterhoeven

1994-01-01

91

Zeolitic basanite from southeastern California  

Microsoft Academic Search

In a belt of Quaternary volcanism within the Mojave Desert, California, lavas of alkali-olivine basalt have been extruded from many centers. Also three small volcanoes erupted alkaline lavas similar to basanite, except that the zeolites phillipsite and chabazite crystallized in the groundmass instead of the usual feldspathoid. These zeolite-bearing lavas, more alkaline than the olivine basalts, brought many peridotitic nodules

W. S. Wise

1966-01-01

92

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

1997-04-15

93

Inhibition of copper corrosion by self-assembled films of new Schiff bases and their modification with alkanethiols in aqueous medium  

Microsoft Academic Search

The inhibitive action of self-assembled films derived from two ligands Schiff bases, including N,N?-ethylen-bis (salicylidenimine) and N,N?-ortho-phenylen-bis (salicylidenimine) on copper surface has been studied by electrochemical techniques in chloride and acidic solutions. It was found that when the concentration of the inhibitors was increased the inhibition efficiency was increased, too. The results of the electrochemical studies have illustrated that the

M. Ehteshamzade; T. Shahrabi; M. G. Hosseini

2006-01-01

94

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

95

Adjusting the host–guest interaction to promote KNO 3 decomposition and strong basicity generation on zeolite NaY  

Microsoft Academic Search

A new strategy was utilized to prepare strongly basic zeolite through precoating MgO on the zeolite NaY prior to KNO3 modification. By controlling the loading amount of the precursor magnesium acetate, MgO could be well dispersed on NaY as long as its content did not exceed 12wt%. The precoated MgO layer played a significant role in enhancing the basicity of

Lin Bing Sun; Fang Na Gu; Yuan Chun; Jia Hui Kou; Jing Yang; Ying Wang; Jian Hua Zhu; Zhi Gang Zou

2008-01-01

96

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 ...

97

Zeolitic basanite from southeastern California  

Microsoft Academic Search

In a belt of Quaternary volcanism within the Mojave Desert, California, lavas of alkali-olivine basalt have been extruded\\u000a from many centers. Also three small volcanoes erupted alkaline lavas similar to basanite, except that the zeolites phillipsite\\u000a and chabazite crystallized in the groundmass instead of the usual feldspathoid. These zeolite-bearing lavas, more alkaline\\u000a than the olivine basalts, brought many peridotitic nodules

W. S. Wise

1966-01-01

98

Zeolites in complex nitrogen biofertilizers  

Microsoft Academic Search

A novel technology for producing complex, ecologically safe biofertilizer, combining advantageous properties of both zeolites and nitrogen-fixing microorganisms has been developed. The resulted biofertilizer is a complex of high-activity nitrogen-fixing strain of Azotobacter chroococcum, isolated from the soil in Armenia and the local zeolite modified by the new technology considering the specific features of this microorganism. The new technology for

Anahit Chakhalyan; Gayane Avetisova; Ashot Saghiyan; Leyli Chil-Akopyan; Lusine Melkonyan; Rudolf Gevorkyan; Hakob Sargsyan; Liana Ghazarian

2008-01-01

99

Inhibition of copper corrosion by self-assembled films of new Schiff bases and their modification with alkanethiols in aqueous medium  

NASA Astrophysics Data System (ADS)

The inhibitive action of self-assembled films derived from two ligands Schiff bases, including N,N?-ethylen-bis (salicylidenimine) and N,N?-ortho-phenylen-bis (salicylidenimine) on copper surface has been studied by electrochemical techniques in chloride and acidic solutions. It was found that when the concentration of the inhibitors was increased the inhibition efficiency was increased, too. The results of the electrochemical studies have illustrated that the inhibition efficiency of S-o-ph-S is higher than S-E-S. Both the Schiff bases obeyed the Langmuir isotherm and thermodynamics calculations revealed that S-o-ph-S had larger adsorption constant and more negative free energy of adsorption with respect to S-E-S. When the films were modified by propanethiol and 1-dodecanethiol, the corrosion resistance of mixed films was significantly increased.

Ehteshamzade, M.; Shahrabi, T.; Hosseini, M. G.

2006-02-01

100

Nature of active species in copper-based catalysts and their chemistry of transformation of nitrogen oxides  

Microsoft Academic Search

Copper-based catalysts are active in a wide range reactions of transformation of nitrogen oxides and represent an useful model system to better understand the fundamental aspects of the chemistry and mechanism of reaction of catalytic transformation of these pollutants. After an introduction on the reactivity of copper-based catalysts (supported and unsupported copper oxide, Cu-zeolites, cuprates and other copper compounds) in

Gabriele Centi; Siglinda Perathoner

1995-01-01

101

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

102

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.  

PubMed

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. PMID:22564733

Kajikawa, Takao; Kataoka, Kunishige; Sakurai, Takeshi

2012-04-30

103

Flexibility of ideal zeolite frameworks.  

PubMed

We explore the flexibility windows of the 194 presently-known zeolite frameworks. The flexibility window represents a range of densities within which an ideal zeolite framework is stress-free. Here, we consider the ideal zeolite to be an assembly of rigid corner-sharing perfect tetrahedra. The corner linkages between tetrahedra are hard-sphere oxygen atoms, which are presumed to act as freely-rotating, force-free, spherical joints. All other inter-tetrahedral forces, such as coulomb interactions, are ignored. Thus, the flexibility window represents the null-space of the kinematic matrix that governs the allowable internal motions of the ideal zeolite framework. We show that almost all of the known aluminosilicate or aluminophosphate zeolites exhibit a flexibility window. Consequently, the presence of flexibility in a hypothetical framework topology promises to be a valuable indicator of synthetic feasibility. We describe computational methods for exploring the flexibility window, and discuss some of the exceptions to this flexibility rule. PMID:20589266

Kapko, V; Dawson, C; Treacy, M M J; Thorpe, M F

2010-06-29

104

Parameters influencing zeolite incorporation in PDMS membranes  

SciTech Connect

The incorporation of several types of zeolite in PDMS membranes is studied, by measuring the tensile strength, xylene sorption, and density of the membranes. The zeolite is shown to be involved in the cross-linking of the membrane. The interaction between the PDMS matrix and the zeolites results in reinforced membranes in the case of zeolite Y. The parameters influencing the dispersion of the zeolite in the membrane are investigated, as well as several aspects of the preparation method. Finally, the idea of cross-linking is applied to explain the results of water/ethanol pervaporation. 25 refs., 9 figs., 4 tabs.

Vankelecom, I.F.J.; Scheppers, E.; Heus, R.; Uytterhoeven, J.B. (Katholieke Universiteit Leuven (Belgium))

1994-11-24

105

Selective reduction of nitrogen oxides by C 3 -C 4 hydrocarbons on metal zeolite catalysts  

Microsoft Academic Search

A study was carried out on the activity of high silicon cation-exchanged zeolites containing Period IV metals (Fe, Cu, Zn, and Co) and lanthanides (La and Ce) in the reduction of nitrogen oxides by C3-C4 hydrocarbons in an oxidizing atmosphere and the kinetics of this process for the copper and cerium catalysts, which display the highest activity. The catalyst activity

S. N. Orlik; V. L. Struzhko; V. P. Stasevich; M. G. Martsenyuk-Kukharuk

1995-01-01

106

Metallo-hydrazone complexes immobilized in zeolite Y: Synthesis, identification and acid violet-1 degradation  

Microsoft Academic Search

Copper(II), cobalt(II) and nickel(II) complexes of hydrazone ligand (SAPH) derived from salicylaldehyde and phenylhydrazine have been encapsulated in zeolite-Y super cages via ship-in-a-bottle synthesis. Detailed characterization of the intrazeolitic complexes were performed by elemental analysis, spectral (FT-IR, UV–Vis.) studies, magnetic measurements and X-ray diffraction. Furthers, surface texture and thermal analysis (TG, DTG, DTA) have provided further evidence for successful immobilization

Ayman H. Ahmed; M. S. Thabet

107

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

2008-10-11

108

A novel concept for photovoltaic cells: clusters of titanium dioxide encapsulated within zeolites as photoactive semiconductors.  

PubMed

Discrete clusters of TiO(2) (of only a few titanium atoms) are prepared within the internal micropore space of zeolite Y (4.8 wt % Ti loading) and characterized by Raman spectroscopy (rutile- and anatase-like structures), electron microscopy combined with elemental analyses (coincident Si and Ti spatial distribution), and X-ray diffraction (minor zeolite crystallinity decrease). The parent TiO(2)@Y sample is modified either by adsorption of acid-organic compounds (benzoic and 4-aminobenzoic acids or catechol) or by nitrogen doping. After modification, the optical UV/Vis spectrum of the parent TiO(2)@Y (onset of the absorption band at wavelengths <300 nm and bandgap of 4.2 eV) changes, and the appearance of new bands expanding to the visible region is observed. In contrast to the inactive zeolite Y matrix, all the zeolite-encapsulated TiO(2) species exhibit a photovoltaic response. The influence of the I(2)/I(3) (-) concentration in the electrolyte solution on the temporal profile of the photovoltage clearly shows that I(2)/I(3) (-) is also a suitable carrier for the positive charge in zeolite-based photovoltaic devices. The photocurrent response and the efficiency of the photovoltaic cell based on zeolite-encapsulated TiO(2) materials depend on the nature of the organic modifier and on the N-doping. The most efficient photovoltaic cell is that based on N-doped TiO(2)@Y, which exhibits a V(OC) (voltage at open circuit) of 270 mV, an I(SC) of 5.8 muA (current at short circuit), and a fill factor (FF) of 0.4. Although these values are low compared to current dye-sensitized TiO(2) solar cells, our findings could open up a promise for a stimulating research on the photovoltaic activity of zeolite-based host-guest solids. PMID:16921574

Alvaro, Mercedes; Carbonell, Esther; Atienzar, Pedro; García, Hermenegildo

2006-09-11

109

Structural characteristics of modified natural zeolite  

Microsoft Academic Search

Natural zeolite of Slovak provenience has been modified with magnetic nanoparticles at selected temperatures of 20, 50 and\\u000a 85 °C with the aim to enhance its sorption properties. The pore, surface and structural properties of zeolite\\/iron oxide composite\\u000a were characterized using nitrogen adsorption measurements, electron probe microanalysis and powder X-ray diffraction. The\\u000a crystallinity of the host zeolite was strongly influenced by

Annamária Mockov?iaková; Marek Matik; Zuzana Orolínová; Pavol Hudec; Erika Kmecová

2008-01-01

110

Treating Coalbed Natural Gas Produced Water for Beneficial Use By MFI Zeolite Membranes  

SciTech Connect

Desalination of brines produced from oil and gas fields is an attractive option for providing potable water in arid regions. Recent field-testing of subsurface sequestration of carbon dioxide for climate management purposes provides new motivation for optimizing efficacy of oilfield brine desalination: as subsurface reservoirs become used for storing CO{sub 2}, the displaced brines must be managed somehow. However, oilfield brine desalination is not economical at this time because of high costs of synthesizing membranes and the need for sophisticated pretreatments to reduce initial high TDS and to prevent serious fouling of membranes. In addition to these barriers, oil/gas field brines typically contain high concentrations of multivalent counter cations (eg. Ca{sup 2+} and SO{sub 4}{sup 2-}) that can reduce efficacy of reverse osmosis (RO). Development of inorganic membranes with typical characteristics of high strength and stability provide a valuable option to clean produced water for beneficial uses. Zeolite membranes have a well-defined subnanometer pore structure and extreme chemical and mechanical stability, thus showing promising applicability in produced water purification. For example, the MFI-type zeolite membranes with uniform pore size of {approx}0.56 nm can separate ions from aqueous solution through a mechanism of size exclusion and electrostatic repulsion (Donnan exclusion). Such a combination allows zeolite membranes to be unique in separation of both organics and electrolytes from aqueous solutions by a reverse osmosis process, which is of great interest for difficult separations, such as oil-containing produced water purification. The objectives of the project 'Treating Coalbed Natural Gas Produced Water for Beneficial Use by MFI Zeolite Membranes' are: (1) to conduct extensive fundamental investigations and understand the mechanism of the RO process on zeolite membranes and factors determining the membrane performance, (2) to improve the membranes and optimize operating conditions to enhance water flux and ion rejection, and (3) to perform long-term RO operation on tubular membranes to study membrane stability and to collect experimental data necessary for reliable evaluations of technical and economic feasibilities. Our completed research has resulted in deep understanding of the ion and organic separation mechanism by zeolite membranes. A two-step hydrothermal crystallization process resulted in a highly efficient membrane with good reproducibility. The zeolite membranes synthesized therein has an overall surface area of {approx}0.3 m{sup 2}. Multichannel vessels were designed and machined for holding the tubular zeolite membrane for water purification. A zeolite membrane RO demonstration with zeolite membranes fabricated on commercial alpha-alumina support was established in the laboratory. Good test results were obtained for both actual produced water samples and simulated samples. An overall 96.9% ion rejection and 2.23 kg/m{sup 2}.h water flux was achieved in the demonstration. In addition, a post-synthesis modification method using Al{sup 3+}-oligomers was developed for repairing the undesirable nano-scale intercrystalline pores. Considerable enhancement in ion rejection was achieved. This new method of zeolite membrane modification is particularly useful for enhancing the efficiency of ion separation from aqueous solutions because the modification does not need high temperature operation and may be carried out online during the RO operation. A long-term separation test for actual CBM produced water has indicated that the zeolite membranes show excellent ion separation and extraordinary stability at high pressure and produced water environment.

Robert Lee; Liangxiong Li

2008-03-31

111

Process for preparing silicon substituted zeolite compositions  

SciTech Connect

This patent describes the process for substituting silicon into the crystal lattice of zeolites in place of extracted lattice aluminum atoms to achieve zeolite products of higher silicon content. It comprises: providing a starting aluminosilicate zeolite having a framework SiO{sub 2}/Al{sub 2}O{sub 3} molar ratio of at least 2 and pore diameters of at least 3 Angstroms; contacting the starting zeolite at a temperature of 25{degrees} C. to 95{degrees} C. with an aqueous solution of a fluorosilicate salt containing from 0.5 to 1.5 moles per liter of the fluorosilicate salt dissolved therein, the proportions of zeolite and fluorosilicate salt being at least 0.1 moles of salt per 100 grams of anhydrous zeolite; maintaining contact between the zeolite and the salt solution for a period not in excess of 5 hours; removing from contact with the zeolite the liquid medium containing at least 90 percent of the by-product fluoroaluminate salt produced by the reaction of the fluorosilicate salt with the zeolite.

Skeels, G.W.

1991-02-26

112

Nanotransfer printing for patterning conductive copper features  

NASA Astrophysics Data System (ADS)

The drive for low-cost electronics creates a need for new techniques to directly and inexpensively pattern copper features in the 1-100?m range. We have developed a solventless, additive approach for printing permanent, conductive copper features at ambient conditions. Our technique is analogous to previously established nanotransfer printing (nTP) procedures for patterning gold with one marked difference. When copper is deposited onto a poly(dimethylsiloxane), PDMS, stamp, residual oligomers from the stamp penetrate between copper grains. This penetration disrupts the conductive pathway between copper grains; the printed copper patterns are electrically insulating as a consequence. This phenomenon is not observed with nanotransfer printing of gold features. A simple modification to the patterning procedure -- leaching the PDMS stamps in boiling toluene for 2-3 days to remove uncrosslinked oligomers -- results in printed copper patterns that are electrically conductive, with an average resistivity of 31?ohms-cm.

Dickey, Kimberly; Sun, Yangming; Loo, Yueh Lin

2006-03-01

113

Assignment of Nonclassical [Cu(CO)(n)](+) (n = 1, 2) Complex Ions in Zeolite Cages.  

PubMed

A time-resolved FT-IR technique combined with an isotopic tracer method has been applied to study CO adsorbates on Cu(+) ions in copper ion-exchanged zeolites. Three kinds of monocarbonyl species were found to adsorb strongly on Cu-zeolite samples after admission and subsequent evacuation of gas phase CO at room temperature. Their absorption bands were observed at 2146-2160, 2128-2150, and 2097-2129 cm(-1), respectively, dependent on the zeolite structures. In the presence of gaseous CO, the monocarbonyl species at 2146-2160 cm(-1) (so called nonclassical [Cu(CO)](+) complexes) could react with a CO molecule to form a dicarbonyl species [Cu(CO)(2)](+) with nu(sym) bands at 2169-2180 cm(-1). The reactivity of the nonclassical [Cu(CO)](+) complexes was dependent on the zeolite structures, ferrierite > mordenite > ZSM-5 > X-type left harpoon ovet right harpoon offretite/erionite left harpoon ovet right harpoon Y-type > L-type. The remaining two types of monocarbonyl species have little been affected by gas phase CO. PMID:11666867

Iwamoto, Masakazu; Hoshino, Yasuyuki

1996-11-20

114

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

115

Zeolite-based discriminating gas sensors  

Microsoft Academic Search

The use of zeolites to enhance the discriminating power of solid state gas sensors is demonstrated. Screen printed tungsten trioxide (WO3) and chromium titanium oxide (CTO) thick films overlaid and admixed (CTO only) with different forms of zeolites are shown to give different and in some cases, enhanced responses to a variety of gases. We attempt to rationalise the noted

Sheena Dungey; Ayo Afonja; Dewi W. Lewis; Russell Binions; Ivan P. Parkin; Themis Paraskeva; David E. Williams

2008-01-01

116

Hydrophilic and hydrophobic adsorption on Y zeolites  

Microsoft Academic Search

The uniform large micropores of hydrothermally stable Y zeolites are used widely to confine both polar and non-polar molecules. This paper compares the physisorption of water, methanol, cyclohexane, benzene and other adsorbates over various Y zeolites. These adsorbents are commercial products with reproducibly controllable physical and chemical characteristics. Results indicate that the type I isotherms typical for micropore adsorption can

Istvan Halasz; Song Kim; Bonnie Marcus

2002-01-01

117

The flexibility of zeolites for Hydrogen storage  

NASA Astrophysics Data System (ADS)

The flexibility window is a newly discovered theoretical measure which can provide a valuable selection criterion when evaluating hypothetical zeolite framework structures as potential synthetic targets. Today synthetic zeolites are the most important catalysts in petrochemical refineries. There have been considerable efforts to synthesize new zeolites with specific pore geometries, to add to the 167 available at present. Millions of hypothetical structures have been generated on the basis of energy minimization, and there is an ongoing search for criteria capable of predicting new zeolite structures. The flexibility window appears to be a property of existing zeolite frameworks not shared by many hypothetical structures. It provides a valuable selection criterion when evaluating hypothetical zeolite framework structures as potential synthetic targets. We are investigating the use of zeolites as hydrogen storage materials, as small molecules such as molecular hydrogen and ammonia can be easily absorbed into a flexible framework of zeolites. An exiting possibility is the use of framework flexibility to control hydrogen uptake, storage and release. This would allow a safe use of hydrogen for fuel cells.

Sartbaeva, Asel; Wells, Stephen Anthony; Edwards, Peter P.

2008-03-01

118

Chemical Interactions in Multimetal\\/Zeolite Catalysts  

Microsoft Academic Search

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

Sachtler; Wolfgang M. H

2004-01-01

119

Influence of the porous structure of zeolite-containing catalysts on their activity and selectivity. Zeolite-containing catalysts based on a Y zeolite  

SciTech Connect

The catalytic activity and selectivity of zeolite-containing catalysts based on zeolite CaY-78 and amorphous aluminosilicates with various compositions and porous structures in the conversion of n-hexane at 400/sup 0/C have been determined. The differences in the activity and selectivity of the zeolite in the zeolite-containing catalysts in comparison to the zeolite without a matrix have been attributed to the blocking of part of the zeolite by the matrix material and matrix-zeolite cation jumps, whose rate is influenced by the macroporous structure of the matrix. The activity and selectivity of such zeolite-containing catalysts with an inactive matrix are determined by the effects of a mixture of CaY zeolites with different cationic compositions.

Rosolovskaya, E.N.; Barsukov, O.V.

1985-10-01

120

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

121

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

122

Design of zeolite by inverse sigma transformation  

NASA Astrophysics Data System (ADS)

Although the search for new zeolites has traditionally been based on trial and error, more rational methods are now available. The theoretical concept of inverse ? transformation of a zeolite framework to generate a new structure by removal of a layer of framework atoms and contraction has for the first time been achieved experimentally. The reactivity of framework germanium atoms in strong mineral acid was exploited to selectively remove germanium-containing four-ring units from an UTL type germanosilicate zeolite. Annealing of the leached framework through calcination led to the new all-silica COK-14 zeolite with intersecting 12- and 10-membered ring channel systems. An intermediate stage of this inverse ? transformation with dislodged germanate four-rings still residing in the pores could be demonstrated. Inverse ? transformation involving elimination of germanium-containing structural units opens perspectives for the synthesis of many more zeolites.

Verheyen, Elke; Joos, Lennart; van Havenbergh, Kristof; Breynaert, Eric; Kasian, Nataliia; Gobechiya, Elena; Houthoofd, Kristof; Martineau, Charlotte; Hinterstein, Manuel; Taulelle, Francis; van Speybroeck, Veronique; Waroquier, Michel; Bals, Sara; van Tendeloo, Gustaaf; Kirschhock, Christine E. A.; Martens, Johan A.

2012-12-01

123

Entropic inflation of ideal zeolitic frameworks  

NASA Astrophysics Data System (ADS)

Ideal zeolites can be viewed as flexible networks of rigid, corner-sharing tetrahedra. Recent studies have shown that such systems can exist at a range of densities (termed the "flexibility window") without breaking topology or deforming the comprising tetrahedra. They also have shown that densities of real zeolites almost always correspond to the lowest densities within this range. This anomalous behavior is usually attributed to coulombic repulsion between oxygen atoms in framework cavities and channels. In this paper we show that the inflation of ideal zeolites can be driven by entropy. This effect is closely related to displacive phase transitions often observed in zeolites and related materials like quartz, which cannot be explained by potential energy minimization alone. We show that periodicity and high symmetry in ideal zeolites is a result of entropy maximization. An estimation of entropy using a harmonic oscillator model with a realistic force field is given.

Kapko, Vitaliy; Dawson, Colby; Treacy, Michael

2011-03-01

124

Physicochemical properties and different sequence of metal loading (CuFe) over nanoporous of SUZ-4 zeolite.  

PubMed

Different sequence of Cu and Fe loading over nanoporous SUZ-4 zeolite were prepared by incipient wetness impregnation method. K/SUZ-4 zeolite was prepared with SiO2:Al2O3 molar ratio of 21.2 under hydrothermal process at 150 degrees C, 250 rpm for 1 day using tetraethylammonium hydroxide (TEAOH) as a template. Copper(II) and Iron(III) were loaded in K/SUZ-4 with 2.3 and 5.5 wt.% of Copper(II) and 1.0 and 5.0 wt.% of Iron(III). The physico-chemical characterization of CuFe/SUZ-4 were investigated using X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), BET-N2 adsorption, Scanning electron microscopy (SEM) and chemical element analysis. The results show the several types of sequential loading of Cu and Fe metals did not change the structure and pore size of nanoporous SUZ-4 zeolite. The obtained CuFe/SUZ-4 zeolites has a narrow pore size distribution with approximately 0.06 microm diameter with 0.66 microm length of needle crystal shape. PMID:23763208

Pornrattanapimolchai, Choompoonut; Worathanakul, Patcharin

2013-04-01

125

SELECTIVE TOLUENE-METHANOL ALKYLATION OVER MODIFIED ZSM-5 ZEOLITE CATALYSTS  

Microsoft Academic Search

H-ZSM-5 zeolite was modified with divalent elements of groups 11 and VIII of periodic system. The modifications were achieved by impregnating H-2SM-5, containing 35 wt% of alumina as a binder, with metal precursors of Mg, Sr, Ba, Co and Ni. Structure of the modified catalysts was characterized by means of XRD and FTIR techniques. The distribution and strength of different

S. Faramawy

1999-01-01

126

Behavior modification.  

PubMed

Attention deficit/hyperactivity disorder (ADHD) is a chronic and substantially impairing disorder. This means that treatment must also be chronic and substantial. Behavior Modification, and in many cases, the combination of behavior modification and stimulant medication, is a valid, useful treatment for reducing the pervasive impairment experienced by children with ADHD. Based on the research evidence reviewed, behavior modification should be the first line of treatment for children with ADHD. PMID:10944662

Pelham, W E; Fabiano, G A

2000-07-01

127

Influence of the size of extraframework monovalent cations in X-type zeolite on their thermal behavior  

Microsoft Academic Search

Pure and well crystalline NaX zeolite with Si\\/Al=1.5 was prepared by hydrothermal crystallization from the Na2O–Al2O3–SiO2–H2O system. The hydrothermal crystallization was carried out under autogeneous pressure and at static condition at 368K. The post-synthesis modification was achieved by following conventional ion-exchange technique to obtain K+, Rb+ and Cs+-exchanged forms of NaX zeolite. Compositional and structural investigations of parent sample and

U. D. Joshi; P. N. Joshi; S. S. Tamhankar; V. P. Joshi; B. B. Idage; V. V. Joshi; V. P. Shiralkar

2002-01-01

128

Thermodynamics of CO probe molecule adsorption on Cu–FER-zeolite comparison of TPD, FTIR, and microcalorimetry results  

Microsoft Academic Search

The existence of the new type of the adsorption complexes of carbon monoxide, where CO molecule interacts simultaneously with\\u000a both copper and potassium cation, formed on so-called heterogeneous dual adsorption sites was detected by the FTIR spectroscopy\\u000a and temperature programmed desorption technique (TPD) in the Cu, K–FER zeolite samples. The time-resolved IR spectroscopy\\u000a and TPD experiments also proved their lower

Pavel ?i?manec; Roman Bulánek; Karel Frolich

129

Zeolite inorganic supports for BSA immobilization: comparative study of several zeolite crystals and composite membranes.  

PubMed

Zeolites due to their low toxicity and high compatibility are considered new biomaterials for medical applications. The surface adsorption behaviour of zeolite crystals and composite membranes was discussed in this research. The zeolite materials were synthesized by hydrothermal syntheses using different reaction gels to modulate the Brönsted acidity of the microporous structures. Spectrophotometric analyses were used to evaluate protein adsorption on these surfaces. This study revealed that zeolite chemical composition and structure influenced the kinetics of protein adsorption. Zeolite Y surface adsorbed greater amount of BSA than the other structures. The percentage of adsorption increases with temperature and depends on the pH of the solution, being highest at the pI of the protein. The influence of the membrane configuration on the protein adsorption was studied using different zeolite structures and crystallization types. It seems that the observed differences could depend on the type of hydrothermal crystallization inside the inorganic support. PMID:17194574

Tavolaro, Adalgisa; Tavolaro, Palmira; Drioli, Enrico

2006-11-17

130

Zeolite catalyst deactivation by coking  

SciTech Connect

Deactivation of a lanthanum exchanged zeolite Y catalyst for isopropylbenzene (cumene) cracking was studied with a thermobalance. The kinetics of coke formation and the main reaction were determined. The Froment Bischoff approach to modeling catalyst deactivation was used. The deactivation function giving the best fit to both the cracking and coking reaction data was an exponential one related to the coke content of the catalyst. The kinetic mechanism for coking that gave the best fit was one in which parallel and consecutive coking reactions occurred simultaneously. Apparently, more coke forms from products than reactants, especially at higher temperature.

Lin, C.C.; Hatcher, W.J.; Park, S.W.

1983-10-01

131

17O NMR Studies of Zeolites  

NASA Astrophysics Data System (ADS)

Multiple-quantum magic-angle spinning (MQMAS) and double rotation (DOR) techniques were applied in the fields of 17.6 T and 11.7 T to the study the 17O NMR of oxygen-17 enriched zeolites A, LSX and sodalite. In addition, some 29Si and 1H MAS NMR experiments were performed. Zeolites with the ratio Si/Al = 1 were chosen, in order to have an alternating distribution of silicon and aluminum atoms. A linear correlation between the isotropic value of the chemical shift and the Si-O-Al bond angle (taken from X-ray data) could be found for the zeolites A and LSX, but not for sodalites. Hydration of the zeolites causes a downfield 17O NMR chemical shift of about 8 ppm with respect to the dehydrated zeolites. Ion exchange of the hydrated zeolites generates stronger chemical shift effects. The increase of the basicity of the oxygen framework of the zeolite LSX is reflected by a downfield shift of ca. 10 ppm going from the lithium to the cesium form, and the substitution of sodium by thallium in the zeolite A causes a shift of 34 ppm for the O3 site. 17O DOR NMR spectra are superior to 17O 3QMAS NMR spectra, featuring a resolution increase by a factor of two and are about equal with respect to the sensitivity. The residual linewidths of the signals in the 17O DOR and 17O 5QMAS NMR spectra can be explained by a distribution of the Si-O-Al angles in the zeolites.

Freude, Dieter; Loeser, Thomas

132

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

133

Photochemical charge separation in zeolites: Electron transfer dynamics, nanocrystals and zeolitic membranes. Final technical report  

SciTech Connect

Aluminosilicate zeolites provide an excellent host for photochemical charge separation. Because of the constraints provided by the zeolite, the back electron transfer from the reduced acceptor to the oxidized sensitizer is slowed down. This provides the opportunity to separate the charge and use it in a subsequent reaction for water oxidation and reduction. Zeolite-based ruthenium oxide catalysts have been found to be efficient for the water splitting process. This project has demonstrated the usefulness of zeolite hosts for photolytic splitting of water.

Dutta, Prabir K.

2001-09-30

134

Role of structural similarity between starting zeolite and product zeolite in the interzeolite conversion process.  

PubMed

GIS- and LTL- (the three capital characters indicate the framework type-code) type zeolites were obtained by organic structure-directing agent free hydrothermal conversion of FAU-type zeolite at 125 degrees C in the presence of NaOH and KOH, respectively. MOR-type zeolite was found coexisting with GIS-type when the hydrothermal conversion with NaOH was carried out at 140 degrees C. There was a common building unit consisting of four-membered ring chain such as d6r, dsc, and dcc (the three characters indicate the composite building unit-code) units present in both the starting zeolite (FAU-type zeolite) and the product zeolites (GIS- and LTL-type zeolites), which was the crucial factor for crystal growth through interzeolite conversion. In the case of severe hydrothermal synthesis conditions such as high temperature, however, the crystallization behavior was similar to that observed in conventional hydrothermal synthesis using amorphous materials because the starting zeolite was excessively decomposed. The hypothesis was confirmed by successful interzeolite conversion of *BEA- to MFI-type zeolite which shared the common composite building unit mor. PMID:23763196

Honda, Koutaro; Itakura, Masaya; Matsuura, Yumiko; Onda, Ayumu; Ide, Yusuke; Sadakane, Masahiro; Sano, Tsuneji

2013-04-01

135

Photoinduced electron transfer reactions in zeolite cages  

SciTech Connect

This report summarizes work in the two areas of zeolites and layered double hydroxides. Results of studies on structural aspects of Ru(bpy)[sub 3][sup 2+]-zeolite Y are summarized. Photoinduced electron transfer between entrapped Ru(bpy)[sub 3][sup 2+] and methylviologen (MV) in neighboring supercages was examined. Benzylviologen was also used. Since molecules larger than 13 [angstrom] cannot be accomodated in zeolite cages, the layered double metal hydroxides (LDH) LiAl[sub 2](OH)[sub 6][sup +]X[sup [minus

Dutta, P.K.

1992-01-01

136

Synthesis, characterization and energetics of zeolites  

NASA Astrophysics Data System (ADS)

Zeolites are microporous aluminosilicates, and Al or Si can be substituted by other elements, such as Ge, Ga, or P. Zeolites have been studied for more than two hundred years, because of their wide application and importance in mineralogy and technology. With high acidity and special pore system, zeolite beta (IZA code BEA) receives much attention. In the dissertation, the formation and dehydration enthalpy of cation exchanged zeolite beta, Li/Na/K/Rb/Cs/Mg/Ca/Sr/Ba -BEA 14 (14 is the Si/Al ratio), Mg/Ca - BEA 4 (4 is the Si/Al ratio), were studied by high-temperature oxide melt solution calorimetry. From an energetic point of view, zeolites beta are less stable than other zeolites of similar Si/Al ratio and cation content. Their enthalpies of formation and dehydration become more endothermic with increasing average ionic potential of the cations in the channels. The unfavorable enthalpy of low silica Mg-BEA 4 and Ca-BEA 4 suggests a possible energy barrier in their direct synthesis. The formation and partial molar dehydration enthalpy of Li-BEA 3 and Na-BEA 3.67 are also investigated by high temperature calorimetry. The partial molar dehydration enthalpies are a linear function of water content. Molecular mechanics simulations explore the cation and water molecule positions in the framework at several water contents. Ga substitution is of great interest due to the special catalytic character of Ga zeolites and the directing agent effect of Ga atoms. The energetics of gallosilicate zeolites Ga-NaSOD, Ga-NaFAU, Ga-NaNAT, Ga-KNAT, Ga-KLTL and Ga-KTUN-1 were studied. The lattice parameters and adsorbed water content increase after Ga substitution of Al. Compared to analogous aluminosilicate zeolites, the gallosilicate zeolites have a similar dehydration enthalpy per mole of tetrahedra, but a less endothermic dehydration enthalpy per mole of water. The gallosilicate zeolites also have less exothermic formation enthalpies from oxide components. The energetics of Ga zeolites are further discussed in terms of Si/Ga ratio, framework density and cation effects.

Sun, Pingping

137

Zeolite based arsine storage and delivery system  

SciTech Connect

A method of storing and subsequently delivering arsine is described, which comprises the steps of: (a) contacting arsine at a temperature of between about -30/sup 0/C and about +30/sup 0/C with a zeolite having a pore size of between about 5 and about 15 angstroms to provide arsine-adsorbed zeolite suitable to be stored, and (b) heating the arsine-adsorbed zeolite to an elevated temperature of no greater than about 175/sup 0/C for a time sufficient to release at least a portion of the adsorbed arsine to provide free arsine.

Knollmueller, K.O.

1988-05-17

138

Gas adsorption isotherm for dealuminated zeolites  

SciTech Connect

Adsorption is a current technique to remove volatile organic compounds from process gas streams. In industrial applications hydrophobic dealuminated zeolites are often used as adsorbents, because of their specific advantages in comparison to activated carbon or polar zeolites. A new equation for complex adsorption isotherms was developed by using a mathematical method well-known in control engineering. On the basis of this analogy, it is possible to describe the transitional region between Langmuir isotherms and isotherms following Henry`s law. Development and verification of the equation are based on experimental data of the system zeolite DAY-ethanol-air.

Bathen, D.; Schmidt-Traub, H.; Simon, M. [Univ. of Dortmund (Germany). Dept. of Chemical Engineering

1997-09-01

139

Luminescence quenching measurements on zeolite L monolayers  

NASA Astrophysics Data System (ADS)

The luminescence quenching of the oxygen sensitive Ru2+ complex (Ru-ph4-TMS) used as a stopcock and attached to a zeolite L monolayer has been investigated. The luminescence lifetime of the attached Ru-ph4-TMS was the same under N2 and under O2 atmosphere. This remarkable result is attributed to the shielding provided by the channels of the zeolite L crystals arranged as a monolayer. The emitting 3MLCT state of the Ru-ph4-TMS stopcock is localized on the ligand bearing the phenyl groups forming the tail of this complex, which deeply penetrates into the zeolite L channel.

Albuquerque, Rodrigo Q.; Zabala Ruiz, Arantzazu; Li, Huanrong; De Cola, Luisa; Calzaferri, Gion

2006-05-01

140

An x-ray diffraction study of zeolite-containing metal silicates  

SciTech Connect

An x-ray diffraction study of zeolites and zeolite-containing metal silicates showed that a reaction occurs in the preparation of zeolite-containing systems between the zeolite crystallites and the metal silicate base, which depends on the means of the introduction of the zeolite in the chemical composition of the base and the zeolite.

Mel'nikov, V.B.; Chukin, G.D.; Netedov, B.K.

1986-10-01

141

The effects of surface modification on the speciation of metal ions intercalated into aluminosilicates  

SciTech Connect

Microporous aluminosilicates, including clay minerals and zeolites, are ion-exchange materials. In their most common forms, they have the ability to incorporate cationic species within their matrices. Because of this property, microporous aluminosilicates have been proposed as storage media for hazardous waste. In this paper the authors use X-ray absorption spectroscopy (XAS) to examine the structure of cations held within smectite clay minerals and to determine how modification of the surface of the clay using an organic monolayer affects the coordination of the stored cation. The effects of hydrothermal and thermal processing on the coordination of the ions contained within these systems are also investigated. The presence of the monolayer changes the surface of the clay from hydrophilic to hydrophobic. It inhibits the interlayer ions from exchanging freely into environmental water and reduces the leach rate of cations out of the clay by approximately a factor of 20. Significant changes are observed when these coated samples are treated under hydrothermal and thermal conditions. Reductions of uranium (VI), in the form of uranyl, and cupric ions occur. In addition, the uranium aggregates, forming small particles that appear similar to UO{sub 2}. Comparable conglomeration occurs with lead cations and with the reduced copper species.

Wasserman, S.R.; Giaquinta, D.M.; Yuchs, S.E.; Soderholm, L. [Argonne National Lab., IL (United States). Chemistry Div.

1996-12-31

142

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

143

Chemical modification  

Treesearch

Nature is programmed to recycle wood in a timely way through biological, ... This process is reversible, and the fiber shrinks as it loses moisture below the FSP. ... Typical uses for each of these modification technologies are also covered.

144

Behavior Modification  

Microsoft Academic Search

\\u000a Behavioral problems may be associated with disorders of the central nervous system. The therapy of choice for such problems\\u000a is often a behavior modification program possibly supplemented by psychoactive medications. Behavior modification should be\\u000a done by health care personnel with appropriate training and competence. It is essential that all staff involved in a behavior-change\\u000a program have a clear understanding of

Robert M. Anderson

145

Methylcyclohexane conversion over ZSM-11 zeolite  

Microsoft Academic Search

ZSM-11 zeolite samples differing by their active sites (H+ and Zn2+) have been studied in the conversion of methylcyclohexane. It was observed that both the conversion and the selectivity to aromatic hydrocarbons are increased with the zinc content. It has been shown that dehydrogenation of the hydrocarbon, leading directly to toluene, is the initial stage for Zn-ZSM-11 zeolite showing very

Oscar A. Anunziata; Liliana B. Pierella; Raul G. Marino

1995-01-01

146

Strategies for high throughput, templated zeolite synthesis  

Microsoft Academic Search

The design and redesign of high throughput experiments for zeolite synthesis are addressed. A model that relates materials function to the chemical composition of the zeolite and the structure directing agent is introduced. Using this model, several Monte Carlo-like design protocols are evaluated. Multi-round protocols are bound to be effective, and strategies that use a priori information about the structure-directing

Ligang Chen; Michael W. Deem

2002-01-01

147

Template synthesis and characterization of mesoporous zeolites  

Microsoft Academic Search

Well-crystalline ZSM-5 and zeolite Y having uniform mesopores were synthesized with template route method using carbon aerogels of different mesoporosities. These mesoporous zeolites were characterized with X-ray diffraction, FT-IR spectroscopy, field emission scanning electron microscopy, and N2 adsorption. ZSM-5 having mesopore volume of 0.2–1cm3g?1 was obtained. Mesoporous ZSM-5 synthesized by heating at 423K for 96h was well-crystalline, which had mesopores

Yousheng Tao; H Kanoh; Y Hanzawa; K Kaneko

2004-01-01

148

Zeolite-based catalysts for hydrocracking  

SciTech Connect

A zeolite/amorphous dual catalyst system was developed which effectively hydrocracked feeds with wide boiling range to extinction. In this dual catalyst system, the zeolite and the amorphous catalysts operate complementally. The good character of zeolite catalyst can be realized without its bad features. Feeds with higher nitrogen content can be hydrocracked, and product yield with good selectivity for naphthas can be obtained. This scheme was derived from diagnosis of the problems associated with zeolite-based hydrocracking catalysts. A zeolitic hydrocracking catalyst, nickel tungsten on rare earth exchanged X-type zeolite (NiW/REX), was found to be ineffective for extinction recycle hydrocracking of feeds containing heavy components. The process performance was poor as indicated by high catalyst aging rate and poor naphtha selectivity and high hydrogen consumption. The polynuclear ring compounds are refractory to NiW/REX due to steric hindrance resulting from the small pore size of the catalyst, but they are easily hydrocracked with high selectivity to naphtha by amorphous catalyst.

Yan, T.Y.

1983-01-01

149

Preparation of an asymmetric zeolite L film  

SciTech Connect

Zeolites and molecular sieves are widely used for catalysis and gas separations. An elusive but highly rewarding goal is the fabrication of zeolite films for selective membranes, electrodes, sensors, and optoelectronic devices. Recently, a variety of techniques tailored to specific applications has emerged (postsynthesis preparations as well as in situ film deposition); however, to date, no general preparative methods exist. Here we report on a new processing scheme which involves the use of zeolite nanosols (colloidal suspensions of zeolite nanoparticles) for film casting, combined with controlled secondary growth of the nanoparticles. Decoupling film deposition from crystal growth provides added flexibility for tailoring the film microstructure and ease for scaleup. Implementation of this scheme, using zeolite L nanosols, led to the preparation of self-supported asymmetric zeolite L films. These films exhibit a regular decrease in crystal grain size and an increase in interzeolitic porosity proceeding from the intergrown surface of the film down into the bulk of the film. In this regard, we refer to these films as asymmetric, using the term as applied in membrane technology. 35 refs., 4 figs.

Lovallo, M.C.; Tsapatsis, M. [Univ. of Massachusetts, Amherst, MA (United States); Okubo, T. [Univ. of Tokyo (Japan)

1996-08-01

150

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

151

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

152

Comparison absorption of new methylene blue dye in zeolite and nanocrystal zeolite  

Microsoft Academic Search

Mordenite and mordenite nanocrystal, were employed as effective adsorbents for new methylene blue (NMB) from an aqueous solution. The adsorption kinetics was investigated. The adsorption capacity of mordenite nanocrystal zeolite for NMB dye is more than that of the mordenite zeolite. Kinetic and adsorption isotherm studies demonstrate that the adsorption follows the pseudo second-order kinetics. The intraparticle diffusion rate coefficient

Sh. Sohrabnezhad; A. Pourahmad

2010-01-01

153

Activated cation motions in zeolites  

NASA Astrophysics Data System (ADS)

We apply a Monte Carlo technique specialized for the simulation of rare events to study the activated counterions motions in the aluminosilicate Na+-mordenite. Mean activation barriers are obtained from minimum energy paths calculated on realistic potential energy surfaces by using a Metropolis algorithm. Energy barriers for Na+ hops calculated for lattices with various Si/Al ratio are found in good agreement with the Na+ detrapping energies measured by thermally stimulated current spectroscopy. One shows that the dielectric activated motions of Na+ proceed between degenerated many-body ground states with different dipolar moment by either sequential or collective hopping motions. This provides a first microscopic description of dielectric relaxation measured in zeolites.

Maurin, G.; Devautour, S.; Henn, F.; Giuntini, J. C.; Senet, P.

2002-07-01

154

Copper sulfide coated polysulfone films  

NASA Astrophysics Data System (ADS)

The modification of polysulfone surface was used to obtain effective interactions between an organic polymeric surface and an inorganic specie. A previous treatment of the polymer surface with modifiers is required in order to provide adherence. Our objective was the synthesis and the surface characterization of copper sulfide coated polysulfone (CuS PSf) films. SEM micrographs showed a homogeneous distribution of copper sulfide, which contributes to increasing electrical conductivity. X-ray analysis showed a decrease in copper sulfide particles (covellite porcelain) when compared with other polymeric composites prepared under similar conditions. The measured surface conductivity of the CuS PSf films was higher than those of other similar systems, ca. 800 S cm-1.

Kunita, M. H.; Rinaldi, A. W.; Girotto, E. M.; Radovanovic, E.; Muniz, E. C.; Rubira, A. F.

2006-03-01

155

Surface modification of composites with metal nanoparticles  

Microsoft Academic Search

This work examines the possibility of using copper, nickel, and cobalt nanoparticles in the electrodeposition of nickel coatings\\u000a and for surface modification of porous silicon, and also colloidal silver particles for surface modification of silver-containing\\u000a polymer-matrix composites. It is shown that the deposition of metal nanoparticles may influence the morphology, electronic\\u000a structure, and phase composition of the surface and the

N. V. Sotskaya; S. V. Makarov; O. V. Dolgikh; V. M. Kashkarov; A. S. Len’shin; E. A. Kotlyarova

2010-01-01

156

Zeolites US market to reach $1 billion by 2000  

SciTech Connect

This article describes the growth of the U.S. market for zeolites, specifically sodium aluminosilicate. The largest application for zeolites is for petrochemical and petroleum catalysts; however, detergents are also a specific application addressed in the article.

Morris, G.D.L.

1997-02-05

157

Determination of water content in natural zeolites by reflection method.  

National Technical Information Service (NTIS)

Water content in natural zeolites collected from different site places in Cuba has been determined by neutron reflection method. Results show that it is possible to separate the minerals abundant in zeolite from the surrounding barren rocks. Water content...

L. P. Sarria V. Desdin Garcia V. Freixas Lemus O. Dominguez Ley G. Csikai

1989-01-01

158

Dual zeolite fluid cracking catalyst composition for improved gasoline octane  

SciTech Connect

A fluid cracking catalyst is described useful for the production of high octane gasoline comprising a hydrothermally or chemically stabilized Y zeolite component and a stabilized Omega zeolite component having a silica to alumina ratio greater than 15 wherein the weight ratio of the Y zeolite to the stabilized Omega zeolite is 1:3 to 20: 1, said catalyst not having a hydrogenation component. A fluid cracking catalyst is described according to claim 1, wherein the fluid cracking catalyst comprises either (a) a composite of a Y zeolite and a stabilized Omega zeolite in an inorganic matrix, or (b) a mixture of a matrixed Y zeolite component and a matrixed stabilized Omega zeolite component.

Gatte, R.R.

1993-08-17

159

Catalytic Oxidation by Transition Metal Ions in Zeolites.  

National Technical Information Service (NTIS)

The regular cavities of zeolites form a unique environment for carrying out both stoichiometric and catalytic oxidation reactions. Transition metal ions such as molybdenum and cobalt may be introduced into the zeolite, and, as well, the acidity may be var...

J. H. Lunsford

1988-01-01

160

Experiments on Photochemical Energy Storage with Metal-Coated Zeolites.  

National Technical Information Service (NTIS)

Photo-oxidation of water to oxygen using silver zeolite catalysts resulted in a pH-dependence and inherent sensitivity of the photo-redox system depending on the type of zeolite used. (ERA citation 09:037443)

B. Sulzberger

1983-01-01

161

Evaluation of modes of catalyst deactivation by coking for cumene cracking over zeolites  

SciTech Connect

The deposition of coke deactivates a catalyst by the suppression of active sites and/or by choking of pores. The so-called Constant-Coke Arrhenius Plot technique can assess the magnitudes of these two modes of deactivation using reaction experiments under process conditions. For cumene cracking over REY zeolite, a TGA has been used as a continuous-flow microreactor to monitor coke levels, with activity measured by an on-line GC. Using modifications described previously for small-pore catalysts, the authors show that both temperature and coke level influence the relative importance of site suppression and pore choking in the deactivation of the zeolite. At relatively high temperatures, site suppression is predominant at all coke levels studied here. At lower temperatures, pore choking is more important at low levels of coke, with site suppression increasing in importance at the higher coke levels. The results are consistent with a physical model developed. 21 refs., 12 figs.

Bellare, A.; Dadyburjor, D.B. (West Virginia Univ., Morgantown (United States))

1993-04-01

162

The structure of actinide ions exchanged into native and modified zeolites and clays  

SciTech Connect

X-ray absorption spectroscopy (XAS) has been used to investigate the structure and valence of thorium (Th{sup 4+}) and uranyl (UO{sub 2}{sup 2+}) cations exchanged into two classes of microporous aluminosilicate minerals: zeolites and smectite clays. XAS is also employed to examine the fate of the exchanged cations after modification of the mineral surface using self-assembled organic films and/or exposure to hydrothermal conditions. These treatments serve as models for the forces that ultimately determine the chemical fate of the actinide cations in the environment. The speciation of the cations depends on the pore size of the aluminosilicate, which is fixed for the zeolites and variable for the smectites.

Wasserman, S. R.; Soderholm, L.; Giaquinta, D. M.

2000-02-16

163

Absorption and desorption characteristic of zeolites in gas sensor system  

Microsoft Academic Search

Nanosized zeolites as a novel absorbent were investigated targeting for the nerve agent sarin stimulant gas DMMP. Quartz crystal microbalance (QCM) gas sensors modified with Silicalite-1 or Cu-ZSM-5 zeolites synthesized as micro-porous absorbents were fabricated and their gas response characteristics were examined to study the absorption capability of zeolites. The results indicated that Cu-ZSM-5 zeolite has stronger absorption capacity than

Wei Yao; Yuanyuan Hu; Xinming Ji; Nan Ren; Jia Zhou; Yiping Huang; Yi Tang

2008-01-01

164

Zeolite catalysis in the synthesis of isobutylene from hydrous ethanol  

Microsoft Academic Search

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

Cory Bernard Phillips

1999-01-01

165

Basic sites in zeolites followed by IR studies of NO +  

Microsoft Academic Search

The basic properties of zeolitic oxygens were examined by IR studies of NO+ ions. NO+ were formed by the disproportionation of N2O4 (N2O4?NO++NO3?). NO+ were stabilized by zeolitic oxygens and NO3? by the zeolitic cations or positively charged extraframework Al species. The spectra of NO+ in zeolite NaY show three maxima that indicate the presence of oxygens of various negative

Barbara Gil; Karolina Mierzy?ska; Monika Szczerbi?ska; Jerzy Datka

2007-01-01

166

Zeolites as transformation elements in discriminating semiconductor metal oxide sensors  

Microsoft Academic Search

The effectiveness of using zeolites as a method of introducing variance in the gas responses of semiconductor metal oxide gas sensors is demonstrated. Screen printed tungsten trioxide (WO3) and chromium titanium oxide (CTO) thick films overlaid with the hydrogen form of different zeolites were exposed to organic vapours with similar functional groups. The composite metal oxide-zeolite gas sensors responses exhibit

A. Afonja; R. Binions; S. Dungey; I. P. Parkin; D. W. Lewis; D. E. Williams

2010-01-01

167

Adsorption, Diffusion and Reaction Studies of Hydrocarbons on Zeolite Catalysts  

Microsoft Academic Search

Zeolites are crystalline microporous materials that are widely applied as catalysts in industries like oil refining, basic petrochemistry and fine chemistry. The major benefit of the use of zeolites as catalysts lies in their unique microporous structures. However, in some cases the presence of micropores limits the catalytic performance of zeolites due to diffusion limitation. This is caused by the

Sander van Donk

2002-01-01

168

Computer modeling of the infrared spectra of zeolite catalysts  

Microsoft Academic Search

The paper describes the applications of computer modeling methods to the interpretation of the infrared spectra of zeolite frameworks. The correlation of the breathing vibration of ring structures in zeolitic lattices with their infrared spectra was investigated by the molecular dynamics method. The calculations reveal that in periodic zeolite lattices the ring-breathing vibrations participate in many normal modes. Despite the

Konstantin S. Smirnov; Daniel Bougeard

2001-01-01

169

Nanostructured zeolite 4A molecular sieving air separation membranes.  

PubMed

A novel membrane forming strategy is reported to probe the intrinsic O2/N2 selectivity of zeolite 4A membrane and to fabricate highly selective nanocomposite membranes by using a nanocrystal-derived hierarchical porous zeolite 4A membrane whose non-zeolitic mesoporsity is filled with a nonpermeable polymer material (polyfurfuryl alcohol). PMID:12196960

Wang, Huanting; Huang, Limin; Holmberg, Brett A; Yan, Yushan

2002-08-21

170

Synthesis of ionic liquid templated zeolite like structures  

Microsoft Academic Search

This study describes the utilization of the alkyl substituted imidazolium based ionic liquid as a structure directing agent of the MFI type zeolite structure in water rich environment. The resulted zeolite like structure presents some similarities with the parent MFI structure, but grows preferentially in 1D leading to zeolite like nanofibers.

Amando Martín; Svetlana Ivanova; Francisca Romero Sarria; Miguel Ángel Centeno; Jose Antonio Odriozola

2010-01-01

171

Formation of NaA and -X zeolites from waste solutions in conversion of coal fly ash to zeolites  

Microsoft Academic Search

Na-A and -X zeolites were synthesized from waste solutions in conversion of coal fly ash (Fa) to zeolite. The amorphous SiO2 and Al2O3 of Fa were completely dissolved to form Po, Pt, and Pc type zeolites in NaOH solutions at 85°C. Only 24% of Si4+ eluted from Fa were converted to the zeolites and the remaining waste solutions contained high

Hidekazu Tanaka; Yasuhiko Sakai; Ryozi Hino

2002-01-01

172

On the exceptional time-on-stream stability of HZSM-12 zeolite: relation between zeolite pore structure and activity  

Microsoft Academic Search

ZSM-12 and several other 12-membered ring large-pore zeolites have been tested for the reforming of naphthenic hydrocarbon\\u000a mixtures. It was found that ZSM-12 possesses a surprisingly higher coking resistance than other large pore zeolites tested\\u000a such as USY, L-zeolite, mordenite, and ?=zeolite for reforming of hydrocarbon mixtures. This superior performance is due to\\u000a the unique non-interconnecting tubular-like linear channels of

Wenmin Zhang; Panagiotis G. Smirniotis

1999-01-01

173

Sulphurous acid as anodic depolarizer in copper electrowinning Part II  

Microsoft Academic Search

The growing interest in the electrowinning of copper has lead to several modifications including anodic reactions proposed to reduce the high energy requirement. The addition of sulphurous acid to a copper sulphate electrolyte has been studied to avoid oxygen evolution at the anode which requires a potential in excess of 2?V. In particular, the effect of different anode materials, concentration

T. Subbaiah; P. Singh; G. Hefter; D. Muir; R. P. Das

2000-01-01

174

Molecular simulations and experimental studies of zeolites  

NASA Astrophysics Data System (ADS)

Zeolites are microporous aluminosilicate tetrahedral framework materials that have symmetric cages and channels with open-diameters between 0.2 and 2.0 nm. Zeolites are used extensively in the petrochemical industries for both their microporosity and their catalytic properties. The role of water is paramount to the formation, structure, and stability of these materials. Zeolites frequently have extra-framework cations, and as a result, are important ion-exchange materials. Zeolites also play important roles as molecular sieves and catalysts. For all that is known about zeolites, much remains a mystery. How, for example, can the well established metastability of these structures be explained? What is the role of water with respect to the formation, stabilization, and dynamical properties? This dissertation addresses these questions mainly from a modeling perspective, but also with some experimental work as well. The first discussion addresses a special class of zeolites: pure-silica zeolites. Experimental enthalpy of formation data are combined with molecular modeling to address zeolitic metastability. Molecular modeling is used to calculate internal surface areas, and a linear relationship between formation enthalpy and internal surface areas is clearly established, producing an internal surface energy of approximately 93 mJ/m2. Nitrate bearing sodalite and cancrinite have formed under the caustic chemical conditions of some nuclear waste processing centers in the United States. These phases have fouled expensive process equipment, and are the primary constituents of the resilient heels in the bottom of storage tanks. Molecular modeling, including molecular mechanics, molecular dynamics, and density functional theory, is used to simulate these materials with respect to structure and dynamical properties. Some new, very interesting results are extracted from the simulation of anhydrous Na6[Si6Al 6O24] sodalite---most importantly, the identification of two distinct oxygen sites (rather than one), and formation of a new supercell. New calorimetric measurements of enthalpy are used to examine the energetics of the hydrosodalite family of zeolites---specifically, formation enthalpies and hydration energies. Finally, force-field computational methods begin the examination of water in terms of energetics, structure, and radionuclide containment and diffusion.

Moloy, Eric C.

175

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

176

Molecular simulation of alkene adsorption in zeolites  

NASA Astrophysics Data System (ADS)

The adsorption isotherms of various alkenes and their mixtures in zeolites such as silicalite-1 (MFI-type), theta-1 (TON-type), and deca-dodecasil 3R (DDR-type) were calculated using the grand canonical Monte Carlo (GCMC) approach. Additionally, the adsorption of alkene-alkane mixtures was simulated. The GCMC approach was combined with the configurational-bias Monte Carlo (CBMC) method. Effective Lennard-Jones parameters for the interaction between the oxygen atoms of all-silica zeolites and the sp2-hybridized groups of linear alkenes were determined using a united atom force field. They were adjusted to the experimental adsorption data of silicalite-1 (MFI). The inflection behaviour of the 1-heptene isotherm was investigated in detail. It is shown that, in the inflection region, the 1-heptene molecules alter their end-to-end length depending on their location. The occurrence of a maximum in the mixture adsorption isotherms is attributed to two effects: entropic effects and non-ideality effects. From the mixture simulations some general conclusions concerning the separation of hydrocarbons with silicalite-1 can be drawn. The transferability of the Lennard-Jones parameters to other zeolites was investigated. Simulations of adsorption isotherms in the zeolites theta-1 and DD3R and their comparison with experimental data indicate the possibility of transferring the parameters to other all-silica zeolites.

Jakobtorweihen, Sven; Hansen, Niels; Keil, Frerich J.

177

Molecular recognition in cation-exchanged zeolites  

NASA Astrophysics Data System (ADS)

The concepts of confinement- and molecular recognition-driven chemical reactivity of cation-exchanged zeolites is illustrated by our recent results from periodic and cluster density functional theory (DFT) calculations. The reactivity of alkali-earth- and alkaline-exchanged low-silica zeolites for selective photo-oxidation of alkenes with molecular oxygen and for N2O4 disproportionation is shown to be mainly due to the specific arrangement and the size of the cations in the zeolite cage. An attempt is made to separate the effects of basicity of the framework, the Lewis acidity of the extra-framework cations and the electrostatic field in the zeolite cage as well as its geometrical properties for the respective reactions. The importance of the favorable adsorption fashion of the reagents controlled by noncovalent interactions with the microporous matrix is shown. The role of the weak interactions with the zeolite walls and the factors, which determine the preference for a particular adsorption mode, are discussed by the example of light alkanes adsorption to Mg- and Ca-exchanged faujasites.

Pidko, Evgeny A.; van Santen, Rutger A.

178

Phenylalanine and arginine adsorption in zeolites X, Y, and Beta.  

PubMed

This paper documents a continuation of work published in Langmuir 2005, 21, 8743-8750. We report new aspects of this amino acid adsorption study, including the effect of changing zeolite framework type and results from adsorption of mixed amino acids. In single-amino-acid adsorption experiments, zeolite Y (Si/Al=2.5) was found to adsorb no phenylalanine while admitting arginine to a similar extent as observed with zeolite beta. Using this zeolite Y, we measured mixed-amino-acid separation selectivities for arginine/phenylalanine as large as 25,000 or 2 orders of magnitude larger than the corresponding selectivities measured with zeolite beta. PMID:17042553

Krohn, John E; Tsapatsis, Michael

2006-10-24

179

Capturing Ultrasmall EMT Zeolite from Template-Free Systems  

NASA Astrophysics Data System (ADS)

Small differences between the lattice energies of different zeolites suggest that kinetic factors are of major importance in controlling zeolite nucleation. Thus, it is critical to control the nucleation kinetics in order to obtain a desired microporous material. Here, we demonstrate how careful investigation of the very early stages of zeolite crystallization in colloidal systems can provide access to important nanoscale zeolite phases while avoiding the use of expensive organic templates. We report the effective synthesis of ultrasmall (6- to 15-nanometer) crystals of the large-pore zeolite EMT from template-free colloidal precursors at low temperature (30°C) and very high yield.

Ng, Eng-Poh; Chateigner, Daniel; Bein, Thomas; Valtchev, Valentin; Mintova, Svetlana

2012-01-01

180

Natural zeolite reactivity towards ozone: the role of compensating cations.  

PubMed

Among indoor pollutants, ozone is recognised to pose a threat to human health. Recently, low cost natural zeolites have been applied as alternative materials for ozone abatement. In this work, the effect of compensating cation content of natural zeolite on ozone removal is studied. A Chilean natural zeolite is used here as starting material. The amount of compensating cations in the zeolite framework was modified by ion exchange using an ammonium sulphate solution (0.1 mol L(-1)). Characterisation of natural and modified zeolites were performed by X-ray powder diffraction (XRD), nitrogen adsorption at 77K, elemental analysis, X-ray fluorescence (XRF), thermogravimetric analysis coupled with mass spectroscopy (TGA-MS), and temperature-programmed desorption of ammonia (NH(3)-TPD). Ozone adsorption and/or decomposition on natural and modified zeolites were studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Results show that the zeolite compensating cation content affects ozone interaction with zeolite active sites. Ammonium ion-exchange treatments followed by thermal out-gassing at 823 K, reduces ozone diffusion resistance inside the zeolite framework, increasing ozone abatement on zeolite surface active sites. Weak and strong Lewis acid sites of zeolite surface are identified here as the main active sites responsible of ozone removal. PMID:22633878

Valdés, Héctor; Alejandro, Serguei; Zaror, Claudio A

2012-05-05

181

Endo- to exo-isomerization of tetrahydrodicyclopentadiene catalyzed by commercially available zeolites  

Microsoft Academic Search

This paper presents the results of catalytic endo- to exo-isomerization of tetrahydrodicyclopentadiene. Several zeolites were tested and influences of calcinations temperatures, Si\\/Al ratio and cations of the zeolites on the reaction were investigated. The results showed that HY zeolites were more active than other zeolites and Y zeolites with other cations, because of its large pore size and relative strong

Enhui Xing; Zhentao Mi; Chengwei Xin; Li Wang; Xiangwen Zhang

2005-01-01

182

Effect of Zeolite Chemical Surface Properties on Catalytic Ozonation of Methylene Blue Contaminated Waters  

Microsoft Academic Search

Heterogeneous catalytic ozonation using natural zeolite has been recently reported. However, there is a lack in the information related to the influence of zeolite active surface sites in this combined system. This work presents experimental results on the effect of zeolite chemical surface properties on catalytic ozonation. Zeolite samples with different chemical surface compositions were prepared from natural zeolite. The

Héctor Valdés; Rolando F. Tardón; Claudio A. Zaror

2010-01-01

183

Home modification.  

PubMed

Almost 50 million Americans--about one in five--live with a mental or physical disability, many in homes that are inconvenient, restrictive, or dangerous for them. Modifying the home using universal (barrier-free) design, architectural accessibility, and other such concepts can reduce the risk of falls and improve overall function. Nurses can be involved by assessing patients' living quarters and recommending specific modifications. PMID:17016095

McCullagh, Marjorie Cook

2006-10-01

184

Methane dehydro?aromatization over a Mo\\/phosphoric rare earth?containing penta?sil type zeolite in the absence of oxygen  

Microsoft Academic Search

The dehydro?aromatization of methane over a Mo?modified penta?sil type high?silica zeolite containing phosphoric and rare\\u000a earth oxide (abbreviated as Mo\\/HZRP?1) was investigated. As a modification of HZSM?5, HZRP?1 is also a good support for the\\u000a preparation of Mo?based zeolite catalysts, and is active for methane dehydro?aromatization. Mo\\/HZRP?1 catalysts are more active\\u000a at high Mo loadings compared with Mo\\/HZSM?5 catalysts. 27Al

Yuying Shu; Ding Ma; Xinhe Bao; Yide Xu

2000-01-01

185

COPPER AND BRAIN FUNCTION  

Technology Transfer Automated Retrieval System (TEKTRAN)

Increasing evidence shows that brain development and function are impaired when the brain is deprived of copper either through dietary copper deficiency or through genetic defects in copper transport. A number of copper-dependent enzymes whose activities are lowered by copper deprivation form the ba...

186

Zeolites as supports for enzymatic hydrolysis reactions. Comparative study of several zeolites  

Microsoft Academic Search

Fusarium solani pisi recombinant cutinase was immobilised by adsorption on different zeolites and its activity towards the hydrolysis reaction of tricaprylin was measured. It was observed that the enzyme immobilised over most of the zeolites used (NaA, NaX, NaY, NaUSY and modified forms) was active for this reaction, although the specific activity depended strongly on the structure and composition of

A. P. V. Gonçalves; J. M. Lopes; F. Lemos; F. Ramôa Ribeiro; D. M. F. Prazeres; J. M. S. Cabral; M. R. Aires-Barros

1996-01-01

187

Electrical properties of zeolitized volcaniclastic materials  

Microsoft Academic Search

The interpretation of electromagnetic anomalies associated with volcanic activity requires a good understanding of two rock properties, the electrical conductivity and the streaming potential coupling coefficient. We measured these properties on 22 consolidated tuff samples containing clays and zeolites typically found in hydrothermal systems or in other areas of high water-rock interactions associated with active volcanic areas. These rocks exhibit

A. Revil; D. Hermitte; E. Spangenberg; J. J. Cochemé

2002-01-01

188

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

189

Multicomponent liquid ion exchange with chabazite zeolites  

SciTech Connect

In spite of the increasing commercial use of zeolites for binary and multicomponent sorption, the understanding of the basic mass-transfer processes associated with multicomponent zeolite ion-exchange systems is quite limited. This study was undertaken to evaluate Na-Ca-Mg-Cs-Sr ion exchange from an aqueous solution using a chabazite zeolite. Mass-transfer coefficients and equilibrium equations were determined from experimental batch-reactor data for single and multicomponent systems. The Langmuir isotherm was used to represent the equilibrium relationship for binary systems, and a modified Dubinin-Polyani model was used for the multicomponent systems. The experimental data indicate that diffusion through the microporous zeolite crystals is the primary diffusional resistance. Macropore diffusion also significantly contributes to the mass-transfer resistance. Various mass-transfer models were compared to the experimental data to determine mass-transfer coefficients. Effective diffusivities were obtained which accurately predicted experimental data using a variety of models. Only the model which accounts for micropore and macropore diffusion occurring in series accurately predicted multicomponent data using single-component diffusivities. Liquid and surface diffusion both contribute to macropore diffusion. Surface and micropore diffusivities were determined to be concentration dependent.

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

1993-10-01

190

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

191

Adsorption of pyridine on dealuminated zeolite HY  

Microsoft Academic Search

Infrared spectra showed that over 80% of aluminum atoms on the surface of zeolite HY were extracted by a exposure of SiCl4 vapor at elevated temperatures. The dealumination of the HY surface resulted in an appreciable change in its acidic properties. Infrared spectra of adsorbed pyridine indicated the formation of various kinds of Lewis acid sites on the delauminated HY

H. Paul Wang

1999-01-01

192

On the templating of curvature in zeolites  

Microsoft Academic Search

The cage and tunnel descriptions of some zeolite crystal structures have previously been shown to be succinctly described as structural networks lying on periodic minimal surfaces, which are saddle-shaped surfaces whose average curvature vanishes everywhere on the surface. The authors establish here that the vanishing average curvature of these structures is due to the templating effect of typical cations (e.g.,

Z. Blum; S. Hyde

2009-01-01

193

Polyphosphonium Salts as Templates for New Zeolites  

Microsoft Academic Search

Zelites have conventionally been prepared using quaternary ammonium salts as templates which control the pore size nnd structure of the resulting material. A range of polyammonium and -phoaphonium salts of the types shown have been prepared for evaluation in directing the formation of new zeolite structiires, particularly those with large pore sizes which may be useful a, ciitalysts for organic

R. Alan Aitken; Véronique Patinec; Paul A. Wright

1999-01-01

194

Zeolite synthesis from pre-treated coal fly ash in presence of soil as a tool for soil remediation  

Microsoft Academic Search

The study reports the synthesis of zeolites from pre-treated coal fly ash in presence of a natural agricultural soil. The synthetic process of zeolites formation in soil was studied for a period of 6 months at 30 and 60 °C. The synthesis of zeolite P (zeolite belonging to the Gismondine series) and zeolite X (zeolite belonging to the Faujasite series)

R. Terzano; M. Spagnuolo; L. Medici; F. Tateo; P. Ruggiero

2005-01-01

195

Deactivation Behavior of Bifunctional Pt\\/H-Zeolite Catalysts during Cyclopentane Hydroconversion  

Microsoft Academic Search

Cyclopentane hydroconversion was used as a probe reaction to study the coking behavior of selected large-pore zeolites loaded with 0.5% Pt under identical conditions. The zeolites studied, namely, Y zeolite, zeolite beta, mordenite, LTL, and ZSM-12, were also tested at several different Si\\/Al ratios. The zeolite pore structure was the most important factor determining the deactivation behavior. Zeolites like Y

Srikant Gopal; Panagiotis G. Smirniotis

2002-01-01

196

Preparing Copper Powder from Cemented Copper.  

National Technical Information Service (NTIS)

Techniques were developed for preparing metallurgical-grade copper powder from industrially produced cement copper. Flotation was used for rejecting discrete gangue particles, acid leaching to remove residual iron and aluminum, hydrogen reduction to elimi...

J. K. Winter L. G. Evans R. D. Groves

1971-01-01

197

Copper allergy from dental copper amalgam?  

PubMed

A 65-year-old female was investigated due to a gradually increasing greenish colour change of her plastic dental splint, which she used to prevent teeth grinding when sleeping. Furthermore, she had noted a greenish/bluish colour change on the back of her black gloves, which she used to wipe her tears away while walking outdoors. The investigation revealed that the patient had a contact allergy to copper, which is very rare. She had, however, had no occupational exposure to copper. The contact allergy may be caused by long-term exposure of the oral mucosa to copper from copper-rich amalgam fillings, which were frequently used in childhood dentistry up to the 1960s in Sweden. The deposition of a copper-containing coating on the dental splint may be caused by a raised copper intake from drinking water, increasing the copper excretion in saliva, in combination with release of copper due to electrochemical corrosion of dental amalgam. The greenish colour change of the surface of the splint is probably caused by deposition of a mixture of copper compounds, e.g. copper carbonates. Analysis by the X-ray diffraction technique indicates that the dominant component is copper oxide (Cu2O and CuO). The corresponding greenish/bluish discoloration observed on the back of the patient's gloves may be caused by increased copper excretion in tears. PMID:12083714

Gerhardsson, Lars; Björkner, Bert; Karlsteen, Magnus; Schütz, Andrejs

2002-05-01

198

Density of mechanisms within the flexibility window of zeolites.  

PubMed

By treating idealized zeolite frameworks as periodic mechanical trusses, we show that the number of flexible folding mechanisms in zeolite frameworks is strongly peaked at the minimum density end of their flexibility window. 25 of the 197 known zeolite frameworks exhibit an extensive flexibility, where the number of unique mechanisms increases linearly with the volume when long wavelength mechanisms are included. Extensively flexible frameworks therefore have a maximum in configurational entropy, as large crystals, at their lowest density. Most real zeolites do not exhibit extensive flexibility, suggesting that surface and edge mechanisms are important, likely during the nucleation and growth stage. The prevalence of flexibility in real zeolites suggests that, in addition to low framework energy, it is an important criterion when searching large databases of hypothetical zeolites for potentially useful realizable structures. PMID:22107389

Kapko, V; Dawson, C; Rivin, I; Treacy, M M J

2011-10-12

199

Zeolite and swine inoculum effect on poultry manure biomethanation  

NASA Astrophysics Data System (ADS)

Poultry manure is an ammonia-rich substrate that inhibits methanogenesis, causing severe problems to the anaerobic digestion process. In this study, the effect of different natural zeolite concentrations on the mesophilic anaerobic digestion of poultry waste inoculated with well-digested swine manure was investigated. A significant increase in methane production was observed in treatments where zeolite was added, compared to the treatment without zeolite.Methane production in the treatment with 10 g dm-3 of natural zeolite was found to be 109.75% higher compared to the treatment without zeolite addition. The results appear to be influenced by the addition of zeolite, which reduces ammonia toxicity in anaerobic digestion and by the ammonia-tolerant swine inoculum.

Kougias, P. G.; Fotidis, I. A.; Zaganas, I. D.; Kotsopoulos, T. A.; Martzopoulos, G. G.

2013-03-01

200

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

201

Behavior and sitting of sodium ion in ZSM-5 zeolite  

Microsoft Academic Search

The behavior of sodium ion in ZSM-5 zeolite was studied by MAS-NMR, ion-exchange, thermal analyses and energy dispersive X-ray analysis (EDX). The samples used were free from surface defects and hence the Na ion in the zeolite was not present in a form of Si-O-Na. In the ion-exchange of the Na ion in the ZSM-5 zeolite with tetramethylammonium (TMA) or

Tatsuo Ohgushi; Toshiyuki Niwa; Hiromi Araki; Satomi Ichino

1997-01-01

202

Raman spectroscopic study of the synthesis of zeolite Y  

SciTech Connect

The formation of zeolite Y from colloidal silica and soluble silicate species was investigated by Raman spectroscopy. The role of aging of the reactant mixture was studied. During the nucleation period, the solid amorphous phase consists of predominantly six-membered aluminosilicate rings, which act as building blocks for the formation of zeolite Y. It is essential to have polymeric, highly condensed silicate units as a reactant if zeolite Y crystallization is to take place.

Dutta, P.K.; Shieh, D.C.; Puri, M.

1987-04-23

203

Separation of water\\/UDMH mixtures using hydroxysodalite zeolite membranes  

Microsoft Academic Search

Dehydration of water\\/1-1-dimethylhydrazine (UDMH) mixtures using hydroxysodalite (HS) zeolite membranes is presented and its performance during separation of water\\/UDMH mixtures was evaluated. HS zeolite was coated on an external surface of porous supports by hydrothermal synthesis. The tubular supports were made of mullite. Water\\/UDMH mixtures were separated at ambient temperature and atmospheric pressure by pervaporation using the HS zeolite membranes.

Mansoor Kazemimoghadam; Toraj Mohammadi

2005-01-01

204

Preparation and characterization of antibacterial zeolite-polyurethane composites  

Microsoft Academic Search

In this study, antibacterial properties were induced in polyurethane (PU) films by the incorporation of Agþ-loaded zeolites as fillers. The mechanical and ther- mal properties of the prepared composites were also investigated. For this purpose, two different types of zeo- lite microparticles, high-silica zeolite beta crystals and low-silica zeolite A crystals, were synthesized. Agþ was added by ion exchange, and

K. Kamõsog; E. A. Aksoy; B. Akata; N. Hasirci; N. Bac

2008-01-01

205

Effects of zeolites on cultures of marine micro-algae  

Microsoft Academic Search

Goal, Scope and Background  The cation-exchange capacity of zeolites is well known and has been increasingly explored in different fields with both economic\\u000a and environmental successes. In aquatic medium with low salinity, zeolites have found multiple applications. However, a review\\u000a of the literature on the applications of zeolites in salt waters found relatively few articles, including some recently published\\u000a papers. The

Adriano Fachini; Maria Teresa S. D. Vasconcelos

2006-01-01

206

Retention of molecular oxygen in zeolites at high temperature  

Microsoft Academic Search

X-ray photoelectron spectroscopy and residual gas analysis experiments were carried out on NaY zeolite at temperatures between -196 and 400°C. The objective of this work was to further understand the 0 1s transition for zeolites since contributions can arise from zeolitic oxygen as well as trapped water. The residual gas analysis data show that molecular oxygen is retained by NaY

S. L. Suib; B. E. Morse

2009-01-01

207

Tetrahedrally coordinated cupric ion in A-zeolites  

Microsoft Academic Search

Electron spin resonance and electron spin echo studies on Cu2+ in four A-zeolites exchanged with K+, Cs+ and NH4+ indicate the formation of a new tetrahedral species, Cu(Oz)3(H2O)2+ where Oz is a zeolite oxygen and the water molecule is probably in the beta cage. The preferential formation of this tetrahedral species in these zeolites instead of the usually observed Cu(H2O)62+

M. Narayana; L. Kevan

1983-01-01

208

Reactivity of trimethyltin manganese pentacarbonyl in zeolite cavities  

Microsoft Academic Search

The anchoring chemistry, thermal stability, and reactivity of MeâSnMn(CO)â in zeolite NaY and acid forms of zeolite Y was studied with X-ray absorption spectroscopy (Sn, Mn edge EXAFS) and in situ FTIR\\/TPD-MS techniques. In the NaY host, the precursor is physically adsorbed from hexane solution into the dehydrated zeolite cages at room temperature without further chemical reaction. Symmetry changes of

A. Borvornwattananont; Thomas Bein

1992-01-01

209

Influence of zeolite additive on properties of autoclaved aerated concrete  

Microsoft Academic Search

In this experimental study, the effect of zeolite on the properties of autoclaved aerated concrete (AAC) was investigated. Zeolite was used as a quartzite replacement in conventional AAC mixtures. The zeolite containing AAC (ZAAC) specimens were prepared at bulk densities of 270–500kg\\/m3. The specimens were examined by X-ray diffraction, X-ray fluorescence, and thermal analysis. Bulk density, compressive strength and thermal

Mustafa Albayrak; Abdulkerim Yörüko?lu; Serdar Karahan; Sema Atl?han; H. Y?lmaz Arunta?; ?smail Girgin

2007-01-01

210

Copper and prion disease  

Microsoft Academic Search

The prion protein is a cell surface glyco-protein expressed by neurones. Its function has remained elusive until it was recently shown to be a copper binding protein. There is now strong evidence that the prion protein has a role in normal brain copper metabolism. Prion protein expression alters copper uptake into cells and enhances copper incorporation into superoxide dismutase. Furthermore

David R Brown

2001-01-01

211

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...

212

Preparation, characterization and catalytic properties of Pd-Fe-zeolite and Pd-Ce-zeolite composite catalysts.  

PubMed

Highly effective composite catalysts for removal of CO by catalytic oxidation have been designed through constructing active centers on the support of zeolite. Performances of the derived Pd-Fe-zeolite and Pd-Ce-zeolite composite catalysts for CO removal under different heterogeneous conditions were studied. The results indicate that the two kinds of promoted catalysts, including special chemical states of Pd and surface active oxygen, show high catalytic activities not only for the low temperature oxidation of CO, but also for CO electro-oxidation. The typical light-off temperatures of Pd-Fe-zeolite and Pd-Ce-zeolite for low temperature CO oxidation are 270 and 273 K. Their characteristic peak potentials for CO electro-oxidation are both around 0.70 V. The promotional effects are associated with the special interaction among Pd, modifier and zeolite, which can be firmly supported by the detailed characterizations using XRD, BET, XPS, TPD and TPR. PMID:22727393

Bi, Yu-Shui; Dang, Guang-Yao; Zhao, Xiao-Hong; Meng, Xian-Feng; Lu, Hui-Jie; Jin, Jian-Tao

2012-06-06

213

Ion exchange properties of Japanese natural zeolites in seawater.  

PubMed

Ion exchange properties of five different Japanese natural zeolites in seawater were examined. Sodium ions could be reduced by all zeolites, although anions, Cl(-) and SO(4)(2-), in seawater showed barely changes. Natural zeolite desalination treatment mainly depends on the ion exchange between Na(+), K(+) and Mg(2+) in seawater and Ca(2+) in natural zeolite. This study found that mordenite is superior to clinoptilolite for use in Na(+) reduction. Mordenite with high cation exchange capacity containing Ca(2+) resulted in the highest Na(+) reduction from seawater. PMID:23303099

Wajima, Takaaki

2013-01-01

214

Regeneration of zeolite catalysts of isobutane alkylation with butenes  

SciTech Connect

The industrial adoption of alkylation of isoalkanes with alkenes is held back by the rapid and irreversible deactivation of the zeolite catalysts appropriate to the process. This paper is aimed specifically at the restoration of the catalytic activity and increase in the service life of zeolite alkylation catalysts. The catalyst chosen for the investigation was HLaCaNaX zeolite both unmodified and modified with various multivalence cations. The thermochemical and oxidative regeneration process as well as the equipment utilized are described. Both the advantages and the drawbacks of the method are given; explanations for the possibly irreversible losses of the catalytic properties in the regenerated zeolites are also put forward.

Manza, I.A.; Tsupryk, I.N.; Bartyshevskii, V.A.; Gaponenko, O.I.; Petrilyak, K.I.

1986-12-10

215

Influencing the selectivity of zeolite Y for triglycine adsorption.  

PubMed

In prior work we studied the adsorption of triglycine on zeolite Y under reference conditions. This study aims to solve the question of which adsorbent properties and process conditions influence the adsorption triglycine from an aqueous solution by zeolite Y. Relevant zeolite parameters to study are: the amount of acidic sites (Si/Al(2) ratio), counter ion, micropore structure. Process conditions that may influence triglycine adsorption are pH, other components such as sugars, amino acids and salts, and temperature. Adsorption of triglycine on zeolite HY is dominated by ionic interaction. The capacity and selectivity of zeolite HY for triglycine can be changed by choosing different Si/Al(2) ratios or changing the counter ion. The presence of cations and basic anions in solutions reduces triglycine adsorption. Fructose and glycine have no significant influence on triglycine adsorption. Temperature only has a slight influence. The pore structure of zeolite Y is not a critical factor for triglycine adsorption, provided pores are accessible to triglycine and in the micropore range (<2 nm). While this allows other zeolites than zeolite Y to be applied, the presence of the supercage structure of zeolite Y is beneficial to obtain better adsorption of triglycine in its neutral form. PMID:17092513

Wijntje, R; Bosch, H; de Haan, A B; Bussmann, P J T

2006-11-07

216

Dry method for recycling iodine-loaded silver zeolite  

DOEpatents

Fission product iodine is removed from a waste gas stream and stored by passing the gas stream through a bed of silver-exchanged zeolite until the zeolite is loaded with iodine, passing dry hydrogen gas through the bed to remove the iodine and regenerate the bed, and passing the hydrogen stream containing the hydrogen iodide thus formed through a lead-exchanged zeolite which adsorbs the radioactive iodine from the gas stream and permanently storing the lead-exchanged zeolite loaded with radioactive iodine.

Thomas, Thomas R. (Idaho Falls, ID); Staples, Bruce A. (Idaho Falls, ID); Murphy, Llewellyn P. (Idaho Falls, ID)

1978-05-09

217

Copper(I)-catalyzed three component reaction of sulfonyl azide, alkyne, and nitrone cycloaddition/rearrangement cascades: a novel one-step synthesis of imidazolidin-4-ones.  

PubMed

A novel one-pot azide-alkyne/ketenimine-nitrone cycloaddition sequence that is induced by copper(I) and allows the transformation of sulfonyl azides, alkynes, and nitrones to highly substituted imidazolidin-4-ones is described. The corresponding heterogeneous version utilizing Cu(I)-modified zeolites as recyclable heterogeneous catalysts shows marginally improved yield and diastereoselectivity. PMID:21992587

Namitharan, Kayambu; Pitchumani, Kasi

2011-10-12

218

Electrical Response of PEDOT-PSS/FAU Zeolite Composites toward SO2: Controlling the Adsorption Properties of FAU Zeolite  

NASA Astrophysics Data System (ADS)

In our work, we propose to combine a conductive polymer, Poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonic acid) (PEDOT-PSS), with FAU zeolites to investigate the potential of the composites for use as SO2 sensing materials.Composites with PEDOT-PSS as a matrix containing faujasite zeolites of various cation types (divalent transition metal ions: Fe^2+, Co^2+, Ni^2+ and Cu^2+), were fabricated to investigate the effect of the cation type of the faujasite zeolites on the electrical conductivity response when exposed to SO2. The composite was tested through repeated sensing and recovery processes to investigate the reversibility and reproducibility. During the recovery process, the electrical conductivity of the composites were recovered, which proves that the sensing characteristics are repeatable. Responses and the interaction mechanism of the conductive polymer/zeolite composites were investigated. The composite with 20% (v/v) of zeolite content gives the highest sensitivity. The electrical conductivity responses of PEDOT-PSS/Zeolite composites can be altered due to the available adsorption sites for gas molecules. The addition of zeolites to the pristine PEDOT-PSS improved the electrical conductivity sensitivity of the composites by enhancing the interaction between PEDOT-PSS and SO2. The type of cation in the zeolite pores effected the sensitivity of the composites, depending on the acidity of the ion-exchanged zeolites.

Chanthaanont, Pojjawan; Sirivat, Anuvat

2012-02-01

219

Directing zeolite structures into hierarchically nanoporous architectures.  

PubMed

Crystalline mesoporous molecular sieves have long been sought as solid acid catalysts for organic reactions involving large molecules. We synthesized a series of mesoporous molecular sieves that possess crystalline microporous walls with zeolitelike frameworks, extending the application of zeolites to the mesoporous range of 2 to 50 nanometers. Hexagonally ordered or disordered mesopores are generated by surfactant aggregates, whereas multiple cationic moieties in the surfactant head groups direct the crystallization of microporous aluminosilicate frameworks. The wall thicknesses, framework topologies, and mesopore sizes can be controlled with different surfactants. The molecular sieves are highly active as catalysts for various acid-catalyzed reactions of bulky molecular substrates, compared with conventional zeolites and ordered mesoporous amorphous materials. PMID:21764745

Na, Kyungsu; Jo, Changbum; Kim, Jeongnam; Cho, Kanghee; Jung, Jinhwan; Seo, Yongbeom; Messinger, Robert J; Chmelka, Bradley F; Ryoo, Ryong

2011-07-15

220

Electron impact single ionization of copper  

NASA Astrophysics Data System (ADS)

Electron impact single ionization cross sections of copper have been calculated in the binary encounter approximation using accurate expression for s DE as given by Vriens and Hartree--Fock momentum distribution for the target electron. The BEA calculation based on the usual procedure does not show satisfactory agreement with experiment in this case but a striking modification is found to be successful in explaining the experimental observations. The discrepancy is linked with the ionization of the 3d10 electrons and probably effective single ionization does not take place from 3d shell of copper leading to smaller values of experimental cross sections.

Jha, L. K.; Roy, O. P.; Roy, B. N.

2000-09-01

221

Zeolitic catalyst with improved regeneration properties  

Microsoft Academic Search

An experimental batch of Tseokar-4 bead catalyst was prepared from the zeolitic catalyst Tseokar-2 by adding 0.15% chromic oxide by weight. Finds that the use of the Tseokar-4 (with better regeneration properties because of the addition of chromium), in a commercial unit made it possible to increase the coke burnoff rate in the regenerator quite substantially, particularly in the upper

V. R. Zinovev; L. V. Bryzgalina; S. N. Khadzhiev; A. P. Kosolapova

1983-01-01

222

Solar energy application of natural zeolites  

Microsoft Academic Search

The utilization of solar energy for cooling is usually achieved by means of sorption-refrigeration cycles. However, the conventional cycles using ammonia-water or lithium bromide-water solutions are inefficient because of the low solution temperatures obtainable with solar radiation and the high condenser temperatures required by air-cooled condensers. Zeolites provide a unique opportunity for a solid-gas adsorption cooling system because of their

D. I. Tchernev

1978-01-01

223

Zeolite compositions as proxies for eruptive paleoenvironment  

NASA Astrophysics Data System (ADS)

We report chemical compositions of authigenic alteration minerals in subglacially erupted hyaloclastite breccias from James Ross Island, Antarctica, which provide a geochemical proxy for paleoenvironment. Analyses of zeolites (phillipsite and chabazite) from several lava-fed deltas on the island were compared with published compositions of zeolites from known freshwater and marine environments. Using values of (Na + K)/Ca = 3.0 (for phillipsites) and 1.0 (for chabazites), the data successfully distinguish between marine and freshwater alteration. However, our study also suggests that volcanic breccias may not be sealed to fluids, even when the pore spaces are completely filled. The James Ross Island data show that, at higher elevations in lava-fed deltas, the zeolites preserve their original freshwater-influenced (i.e., glacial) compositions, whereas at lower elevations, (Na + K)/Ca ratios are generally higher and indicate a later marine influence. We suggest that water may penetrate several kilometers into the volcanic pile by movement along fractures and/or grain boundaries.

Johnson, Joanne S.; Smellie, John L.

2007-03-01

224

Anchoring strategies for bimetallic species in zeolites  

SciTech Connect

We explore a new approach by introducing heterobinuclear organometallic compounds for linking catalytic functions to zeolite frameworks. With two different metals present, the complexes are being anchored to the support via one oxophilic metal, ligand exchange and catalytic reactions may proceed at the second metal center. Anchoring chemistry, thermal stability and reactivity of Me[sub 3]SnMn(CO)[sub 5] in zeolite NaY and acid forms of zeolite Y was studied with X-ray absorption spectroscopy (Sn, Mn edge EXAFS) and in-situ FTIR/TPD-MS techniques. Subsequently, the tin-cobalt complex Me[sub 3]SnCo(CO)[sub 4] has been a focus of detailed synthetic and spectroscopic studies. The reactivity of tricarbonyl (cyclopentadienyl) (trimethylstannyl) molybdenum in new mesoporous hosts has been explored. A recent development is the design of vanadium oxo species in different micro- and mesoporous hosts. These are of great interest for the selective reduction of nitrogen oxides by ammonia, and selective oxidation of different hydrocarbons, such as xylenes, olefines and alkanes. Combination analytical techniques used to probe local structural changes at the molecular level, include EXAFS (Extended X-Ray Absorption Fine Structure) spectroscopy utilizing synchrotron radiation, in situ FT-IR coupled to thermodesorption/MS, UV-NIR, and CCD Raman.

Bein, T.

1993-03-01

225

Solar energy storage by natural zeolites: I. Dehydration of zeolitic tuff  

SciTech Connect

In the perspective of a possible utilization of natural zeolites in the solar energy exploitation as materials suitable for heat storage, the behaviours of chabazitic and phillipsitic tuffs in the isothermal dehydration have been studied, evaluating the influence of temperature, heating rate and cationic form of the zeolite on the water desorption process. The possibility of achieving an almost complete desorption at temperatures of 200/250/sup 0/C in times of the order of two hours or less has been emphasized and indications on the heat amount storable by a chabazitic tuff in its original cationic form have been at last given.

Nastro, A.; Aiello, R.; Colella, C.; Conte, M.; Fittipaldi, F.

1980-12-01

226

Cracking Activity of Zeolite Y Catalysts Synthesised from a South African Kaolinite.  

National Technical Information Service (NTIS)

The following catalysts were prepared from ceramic microspheres which contained 24% NaY zeolites: rare earth cation exchanged zeolite Y, rare earth-acidic exchanged zeolite Y and ultrastable zeolite Y with or without exchanged rare earth cations. A prelim...

M. G. Howden

1981-01-01

227

Influence of zeolites in PDMS membranes. Pervaporation of water\\/alcohol mixtures  

Microsoft Academic Search

A strong influence of the zeolite was found on the pervaporation of alcohol\\/water mixtures using filled PDMS membranes. In all cases, the zeolites reduced the swelling of the PDMS. Incorporation of the hydrophilic zeolite Y increased water fluxes, while ZSM-5 reduced both water and alcohol fluxes due to a partial retention of these molecules in the zeolite. For branched alcohols,

Ivo F. J. Vankelecom; Dirk Depre; Stijn De Beukelaer; Jan B. Uytterhoeven

1995-01-01

228

Removal of Ca and Zn from aqueous solutions by zeolites NaP and KP  

Microsoft Academic Search

Zeolites P in sodium (NaP) and potassium (KP) forms were used as adsorbents for the removal of calcium (Ca) and zinc (Zn) 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

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

2010-01-01

229

Separation of 1-butanol\\/2,3-butanediol using ZSM-5 zeolite-filled polydimethylsiloxane membranes  

Microsoft Academic Search

Mixed matrix membranes were prepared by incorporating ZSM-5 zeolite particles into polydimethylsiloxane. A uniform dispersion of the zeolite in the membrane was obtained. The membranes were characterized with scanning electron microscopy, and the effects of zeolite loading on membrane performance were evaluated. It was found that 80wt.% ZSM-5 loading was optimal for selectivity. Further increase in the zeolite loading either

Pinghai Shao; Ashwani Kumar

2009-01-01

230

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

231

Use of natural zeolite as a supplementary cementitious material  

Microsoft Academic Search

Natural zeolite, a type of frame-structured hydrated aluminosilicate mineral, is used abundantly as a type of natural pozzolanic material in some regions of the world. In this work, the effectiveness of a locally quarried zeolite in enhancing mechanical and durability properties of concrete is evaluated and is also compared with other pozzolanic admixtures. The experimental tests included three parts: In

Babak Ahmadi; Mohammad Shekarchi

2010-01-01

232

Support effects on CO hydrogenation over Ru/zeolite catalysts  

SciTech Connect

Hydrogenation of carbon monoxide at 101.3 kPa has been studied over a series of ion-exchanged Ru catalysts supported on NaX, NaY, KL, Na mordenite, and HY zeolites. The type of zeolite had pronounced effects on the activity and selectivity of the Ru. The specific activity would appear to be related to the dispersion of reduced ruthenium in the zeolite. Methane selectivity, however, seems to be strongly influenced by the type and concentration of alkali cations remaining in the ion-exchanged zeolite. These cations appear to promote chain growth much as traditional alkali promoters would, though perhaps more indirectly. Due to bifunctional properties of the zeolite-supported catalysts, a significant fraction of C/sub 4/ was in the form of isobutane. Formation of isobutane seems to be related to either the Si/Al ratio in the zeolites or the concentration of the remaining alkali cations, but not to the OH concentration. In addition, H/sub 2/ chemisorption at 25/sup 0/C was increasingly suppressed as the Se/Al ratio of the zeolite support increased. Both the formation of isobutane and the suppression of H/sub 2/ chemisorption may be related to the acid strength of the OH groups present, which is a function of the Si/Al ratio of the zeolite.

Chen, Y.W.; Wang, H.T.; Goodwin, J.G. Jr.

1984-02-01

233

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

234

The adsorption of SOâ by zeolites synthesized from fly ash  

Microsoft Academic Search

Zeolites X, Y, and Na-Pl (90 C) and analcime and sodalite (150 C) were synthesized from Class F fly ash using 3 M sodium hydroxide solutions and autogenous pressures. The partially zeolitized fly ashes were dried overnight in air at room temperature and then characterized using X-ray diffraction and SEM. On occasion, a few samples were dried to constant weight

Anand Srinivasan; Michael W. Grutzeck

1999-01-01

235

Zeolitic coatings and their potential use in catalysis  

Microsoft Academic Search

The formation of zeolitic coatings and their properties, such as the thickness, continuity and orientation of the crystals, are related to the presence and macro-organization of a precursor phase. Based on this view, preshaped zeolitic coatings can be prepared which may be either active catalysts themselves or an inert thin membrane on an existing catalyst. They can be applied in

J. C. Jansen; J. H. Koegler; H. van Bekkum; H. P. A. Calis; C. M. van den Bleek; F. Kapteijn; J. A. Moulijn; E. R. Geus; N. van der Puil

1998-01-01

236

Investigation of zeolites by solid state quadrapole NMR.  

National Technical Information Service (NTIS)

The subject of this thesis is the NMR investigation of zeolites. The nature and properties of zeolites are discussed. Some of the basic priniples of NMR techniques on quadrupole nuclei are presented. A special technique, namely a two-dimensional nutation ...

R. Janssen

1990-01-01

237

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

238

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

239

Co-ZSM-5 Zeolites: Characterization and Magnetic Properties  

Microsoft Academic Search

ZSM-5 zeolites modified with Co cations were synthesized. They were characterized by AA, XRD, Raman Spectroscopy, TPR, FTIR and BET. The Co ions were introduced in the zeolitic matrix by wet impregnation or ion-exchange methods, followed by thermal treatments. The incorporation of cobalt ions into ZSM-5 does not affect the high degree of purity, cristallinity and orthorhombic symmetry of the

L. B. Pierella; M. Fernández García; P. Bercoff; H. R. Bertorello

240

Adsorption of Pb and Cd by amine-modified zeolite  

Microsoft Academic Search

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

Ulla Wingenfelder; Bernd Nowack; Gerhard Furrer; Rainer Schulin

2005-01-01

241

Antibacterial activity of heavy metal-loaded natural zeolite.  

PubMed

The antibacterial activity of natural zeolitized tuffs containing 2.60wt.% Cu(2+), 1.47 Zn(2+) or 0.52 Ni(2+) were tested. Antibacterial activities of the zeolites against Escherichia coli and Staphylococcus aureus were tested after 1h and 24h of exposure to 1g of the zeolite in 100mL of three different media, namely Luria Bertani, synthetic wastewater and secondary effluent wastewater. The antibacterial activities of the zeolites in Luria Bertani medium were significantly lower than those in the other media and negatively correlated with the chemical oxygen demand of the media. The Ni-loaded zeolite showed high leaching of Ni(2+) (3.44-9.13wt.% of the Ni(2+) loaded) and weak antibacterial activity in the effluent water. Since Cu-loaded zeolite did not leach Cu(2+) and the leaching of Zn(2+) from Zn-loaded zeolite was low (1.07-1.61wt.% of the Zn(2+) loaded), the strong antibacterial activity classified the Cu- and Zn-loaded zeolite as promising antibacterial materials for disinfection of secondary effluent water. PMID:22178285

Hrenovic, Jasna; Milenkovic, Jelena; Ivankovic, Tomislav; Rajic, Nevenka

2011-12-01

242

Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen  

Microsoft Academic Search

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

H. Frei; F. Blatter; H. Sun

1999-01-01

243

CHARACTERISTICS OF ZEOLITE WASHCOATS ON CORDIERITE MONOLITHS FOR ENVIRONMENTAL APPLICATIONS  

Microsoft Academic Search

Several preparation variables were analyzed which might affect the characteristics of zeolite coatings on cordierite monolith structures obtained by was hcoating. It was found that zeolite type, suspension concentration, number of immersions, solvent, particle size, and additives impinge on coating quality. When the suspension concentration is increased, a non-linear increment of the load is obtained. At the same time, the

J. M. Zamaro; M. A. Ulla; E. E. Miró

244

Exploratory study of mesopore templating with carbon during zeolite synthesis  

Microsoft Academic Search

Here we present an exploratory study on the generation of mesopores in zeolite crystals by templating with carbon during synthesis. With nitrogen physisorption, scanning electron microscopy and (three-dimensional) transmission electron microscopy we have studied the influence of the carbon source and zeolite synthesis conditions on the mesopores generated after the carbon has been burned off. In particular, silicalite-1 crystals have

A. H. Janssen; I. Schmidt; C. J. H. Jacobsen; A. J. Koster; K. P. de Jong

2003-01-01

245

Raman studies of the templated synthesis of zeolites  

Microsoft Academic Search

The application of confocal Raman and FT-Raman in the understanding of zeolite synthesis is a goal that can be reached by studying different levels of complexity. First, the Raman properties of TEOS and its polymerization products under acid conditions is investigated. Structural characterization of zeolite framework vibrations is related to their building blocks such as prisms and sodalite cages. The

P. P. H. J. M. Knops-Gerrits; M. G. L. J. Cuypers

2000-01-01

246

Structure descriptors for organic templates employed in zeolite synthesis  

Microsoft Academic Search

A structural analysis has been carried out upon 130 organic templating agents employed in the synthesis of zeolites from 18 different framework types. The orthogonal principal axes of inertia of these molecules provide quantitative structure descriptors which can be plotted to produce three-dimensional ‘shape-space’ diagrams. Groups of templates which produce different zeolite framework architectures plot in discrete areas of these

R. E. Boyett; A. P. Stevens; M. G. Ford; P. A. Cox

1997-01-01

247

In-situ x-ray absorption study of copper films in ground watersolutions  

SciTech Connect

This study illustrates how the damage from copper corrosion can be reduced by modifying the chemistry of the copper surface environment. The surface modification of oxidized copper films induced by chemical reaction with Cl{sup -} and HCO{sub 3}{sup -} in aqueous solutions was monitored by in situ X-ray absorption spectroscopy. The results show that corrosion of copper can be significantly reduced by adding even a small amount of sodium bicarbonate. The studied copper films corroded quickly in chloride solutions, whereas the same solution containing 1.1 mM HCO{sub 3}{sup -} prevented or slowed down the corrosion processes.

Kvashnina, K.O.; Butorin, S.M.; Modin, A.; Soroka, I.; Marcellini, M.; Nordgren, J.; Guo, J.-H.; Werme, L.

2007-10-29

248

Adsorption kinetics and equilibrium of phenol drifts on three zeolites  

NASA Astrophysics Data System (ADS)

In this study, the sorption of phenol drifts was studied by performing batch kinetic sorption experiments. The equilibrium kinetic data was analyzed using the pseudo-second-order kinetic model. Fowler-Guggenheim model gives a perfect fitting with the isotherm data. The influence of porous structure of a zeolite particle on phenol adsorption from aqueous solutions is analyzed and discussed. The adsorption for phenol drifts on zeolite was proved to be an exothermic process. Thus the solubility of the phenolic compound and the pH of the solution play also an important role in adsorption phenomena. The relative affinity of the phenolic compound toward the zeolite was related to the electron donor-acceptor complexes that were formed between the basic sites on the zeolite (oxygen) and hydrogens (acidic site) of the phenols. Finally zeolite seems to be an efficient adsorbent; it can be easily regenerated by methanol leaching.

Koubaissy, Bachar; Toufaily, Joumana; El-Murr, Maya; Jean Daou, T.; Hafez, Hala; Joly, Guy; Magnoux, Patrick; Hamieh, Tayssir

2012-09-01

249

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.

Vernimmen, Jarian; Cool, Pegie

2011-01-01

250

Dye house wastewater treatment through advanced oxidation process using Cu-exchanged Y zeolite: a heterogeneous catalytic approach.  

PubMed

Catalytic wet hydrogen peroxide oxidation of an anionic dye has been explored in this study. Copper(II) complex of NN'-ethylene bis(salicylidene-aminato) (salenH2) has been encapsulated in super cages of zeolite-Y by flexible ligand method. The catalyst has been characterized by Fourier transforms infra red spectroscopy, X-ray powder diffractograms, Thermo-gravimetric and differential thermal analysis and nitrogen adsorption studies. The effects of various parameters such as pH, catalyst and hydrogen peroxide concentration on the oxidation of dye were studied. The results indicate that complete removal of color has been obtained after a period of less than 1h at 60 degrees C, 0.175M H2O2 and 0.3g l(-1) catalyst. More than 95% dye removal has been achieved using this catalyst for commercial effluent. These studies indicate that copper salen complex encapsulated in zeolite framework is a potential heterogeneous catalyst for removal of color from wastewaters. PMID:17727914

Fathima, Nishtar Nishad; Aravindhan, Rathinam; Rao, Jonnalagadda Raghava; Nair, Balachandran Unni

2007-08-28

251

PEMISAHAN KOMPONEN TAR BATUBARA DENGAN KOLOM FRAKSINASI MENGGUNAKAN FASA DIAM ZEOLIT-Mn (Separation of Coal Tar Compounds by Fractionation Column Using Zeolit-Mn as The Stationary Phase)  

Microsoft Academic Search

Separation of coal tar process has been done by fractionation column using zeolite -Mn as stationary phase. Zeolite -Mn was produced with natural zeolite from Wonosari as raw material and was processes by ion exchange technique of Mn2+ to substitute the cation in the pore of zeolite. The zeolite was made in varying of particle size i.e. 20 - 28,

Bambang Setiaji

252

Molecular chemistry in a zeolite: genesis of a zeolite Y-supported ruthenium complex catalyst.  

PubMed

Dealuminated zeolite Y was used as a crystalline support for a mononuclear ruthenium complex synthesized from cis-Ru(acac)2(C2H4)2. Infrared (IR) and extended X-ray absorption fine structure spectra indicated that the surface species were mononuclear ruthenium complexes, Ru(acac)(C2H4)2(2+), tightly bonded to the surface by two Ru-O bonds at Al(3+) sites of the zeolite. The maximum loading of the anchored ruthenium complexes was one complex per two Al(3+) sites; at higher loadings, some of the cis-Ru(acac)2(C2H4)2 was physisorbed. In the presence of ethylene and H2, the surface-bound species entered into a catalytic cycle for ethylene dimerization and operated stably. IR data showed that at the start of the catalytic reaction, the acac ligand of the Ru(acac)(C2H4)2(2+) species was dissociated and captured by an Al(3+) site. Ethylene dimerization proceeded approximately 600 times faster with a cofeed of ethylene and H2 than without H2. These results provide evidence of the importance of the cooperation of the Al(3+) sites in the zeolite and the H2 in the feed for the genesis of the catalytically active species. The results presented here demonstrate the usefulness of dealuminated zeolite Y as a nearly uniform support that allows precise synthesis of supported catalysts and detailed elucidation of their structures. PMID:18785737

Ogino, Isao; Gates, Bruce C

2008-09-12

253

Electrical conductivity of polyaniline\\/zeolite composites and synergetic interaction with CO  

Microsoft Academic Search

The effects of zeolite content, pore size and ion exchange capacity on electrical conductivity response to carbon monoxide (CO) of polyaniline\\/zeolite composites were investigated. Zeolite Y, 13X, and synthesized AlMCM41, all having the common cation Cu2+, were dry mixed with synthesized maleic acid (MA) doped polyaniline and compressed to form polyaniline (PANI)\\/zeolite pellet composites. The Y, 13X and AlMCM41 zeolite

Nataporn Densakulprasert; Ladawan Wannatong; Datchanee Chotpattananont; Piyanoot Hiamtup; Anuvat Sirivat; Johannes Schwank

2005-01-01

254

Investigation on the effect of zeolite precursor on the formation process of MCM-41 containing zeolite Y building units.  

PubMed

The formation process of MCM-41 containing zeolite Y building units has been investigated by UV Raman spectroscopy, (29)Si and (27)Al MAS NMR spectroscopy, X-ray diffraction (XRD), N2 adsorption and electron microscopy (SEM and TEM). It is found that the precursor containing zeolite Y secondary building units promotes the formation of a metastable mesopore structure just after mixing the zeolite precursors with CTAB. In contrast, the low-polymerized aluminosilicates and well-crystallized zeolite crystals cannot be assembled with CTAB at this stage. The result supports that the zeolite secondary building units should promote to the formation of the mesopore wall. This has been ascribed to its high anionic charge density as well as the appropriate multidentate coordination. Lowering down the pH value to 9.3 facilitates the further polymerization of the aluminosilicate species to build up a stable mesoporous phase. PMID:23434547

Li, Peng; Xiong, Guang; Liu, Liping; Wang, Longlong

2013-02-01

255

Photophysical properties of pyrene in zeolites: Adsorption and distribution of pyrene molecules on the surfaces of zeolite L and mordenite  

SciTech Connect

Adsorption of pyrene on the surfaces of zeolites L and mordenite is investigated using photophysical techniques. Although the internal surfaces of both zeolites are polar, their external surfaces may not be the same. A difference is observed for mordenite. No pyrene excimers can be produced in mordenite, while excimers are readily formed in zeolite L. Due to structural constraints, 30-35% of pyrene adsorbed in mordenite cannot be quenched by O{sub 2}. Rotational movement of pyrene molecules in mordenite is also restricted by the zeolite structure. Laser photolysis produces pyrene cation and anion radicals, the former having a larger yield than the latter in both zeolites. 31 refs., 5 figs., 2 tabs.

Liu, Xinsheng; Thomas, J.K. [Univ. of Notre Dame, IN (United States)

1994-12-01

256

Copper metabolism of astrocytes  

PubMed Central

This short review will summarize the current knowledge on the uptake, storage, and export of copper ions by astrocytes and will address the potential roles of astrocytes in copper homeostasis in the normal and diseased brain. Astrocytes in culture efficiently accumulate copper by processes that include both the copper transporter Ctr1 and Ctr1-independent mechanisms. Exposure of astrocytes to copper induces an increase in cellular glutathione (GSH) content as well as synthesis of metallothioneins, suggesting that excess of copper is stored as complex with GSH and in metallothioneins. Furthermore, exposure of astrocytes to copper accelerates the release of GSH and glycolytically generated lactate. Astrocytes are able to export copper and express the Menkes protein ATP7A. This protein undergoes reversible, copper-dependent trafficking between the trans-Golgi network and vesicular structures. The ability of astrocytes to efficiently take up, store and export copper suggests that astrocytes play a key role in the supply of neurons with copper and that astrocytes should be considered as target for therapeutic interventions that aim to correct disturbances in brain copper homeostasis.

Dringen, Ralf; Scheiber, Ivo F.; Mercer, Julian F. B.

2013-01-01

257

Copper metabolism of astrocytes.  

PubMed

This short review will summarize the current knowledge on the uptake, storage, and export of copper ions by astrocytes and will address the potential roles of astrocytes in copper homeostasis in the normal and diseased brain. Astrocytes in culture efficiently accumulate copper by processes that include both the copper transporter Ctr1 and Ctr1-independent mechanisms. Exposure of astrocytes to copper induces an increase in cellular glutathione (GSH) content as well as synthesis of metallothioneins, suggesting that excess of copper is stored as complex with GSH and in metallothioneins. Furthermore, exposure of astrocytes to copper accelerates the release of GSH and glycolytically generated lactate. Astrocytes are able to export copper and express the Menkes protein ATP7A. This protein undergoes reversible, copper-dependent trafficking between the trans-Golgi network and vesicular structures. The ability of astrocytes to efficiently take up, store and export copper suggests that astrocytes play a key role in the supply of neurons with copper and that astrocytes should be considered as target for therapeutic interventions that aim to correct disturbances in brain copper homeostasis. PMID:23503037

Dringen, Ralf; Scheiber, Ivo F; Mercer, Julian F B

2013-03-14

258

Copper dynamics and impact on microbial communities in soils of variable organic status.  

PubMed

The effect of soil organic status on copper impact was investigated by means of a microcosm study carried out on a vineyard soil that had been amended with varying types of organic matter during a previous long-term field experiment. Soil microcosms were contaminated at 250 mg Cu kg(-1) and incubated for 35 days. Copper distribution and dynamics were assessed in the solid matrix by a sequential extraction procedure and in the soil solution by measuring total and free exchangeable copper concentrations. Copper bioavailability was also measured with a whole-cell biosensor. Modifications of microbial communities were assessed by means of biomass-C measurements and characterization of genetic structure using ARISA (automated-ribosomal-intergenic-spacer-analysis). The results showed that copper distribution, speciation, and bioavailability are strongly different between organically amended and nonamended soils. Surprisingly, in solution, bioavailable copper correlated with total copper but not with free copper. Similarly the observed differential copper impact on micro-organisms suggested that organic matter controlled copper toxicity. Bacterial-ARISA modifications also correlated with the estimated metal bioavailability and corresponded to the enrichment of the Actinobacteria. Contrarily, biomass-C and fungal-ARISA measurements did not relate trivially to copper speciation and bioavailability, suggesting that the specific composition of the indigenous-soil communities controls its sensitivity to this metal. PMID:18497129

Lejon, David P H; Martins, Jean M F; Lévêque, Jean; Spadini, Lorenzo; Pascault, Noémie; Landry, David; Milloux, Marie-Jeanne; Nowak, Virginie; Chaussod, Rémi; Ranjard, Lionel

2008-04-15

259

[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

260

Imperfect wetting of hydrogen in zeolite  

SciTech Connect

We have considered the theoretical dependencies of the amount of supercooling of liquid hydrogen as a function of pore size for constrained geometries in order to compare the different mechanisms for supercooling that can be observed: notably the inhibition of nucleation in small geometries and the use of surfaces for which there is imperfect wetting. Analysis of the dependence of the observed supercooling reported elsewhere for molecular hydrogen and hydrogen deuteride on the pore size in zeolites supports the view that imperfect wetting occurs for small pores that have rough surfaces and dimension less than approximately 10{angstrom}.

Sullivan, N.S.; Rall, M. [Univ. of Florida, Gainesville, FL (United States)

1995-11-01

261

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

2010-04-26

262

The role of zeolites in wastewater treatment of printing inks.  

PubMed

The adsorption of residual organic pollutants from flocculated printing ink wastewater onto several synthetic zeolites was investigated as a finishing method for additional reduction of TOC. The nonselective removal of total organic content was studied. The amount of adsorbed organics was largest for ZSM-5 and NH4-Beta while the other zeolites studied showed lower efficiency, suggesting that adsorption is independent of pore structure. The adsorption rates of organic pollutants were fast. Although the TOC removal increases with increasing amount of zeolite, because of the necessity of additional filtration to lower turbidity to required levels, 5.0 g/L of zeolite was found to be optimum. The 88% reduction of TOC obtained with a single flocculation treatment was improved with the combination of flocculation and adsorption with ZSM-5 which resulted in the overall TOC efficiency of 95%. The addition of zeolites in decantated supernatant water, obtained after flocculation, was also studied in order to assess the effect of floc on zeolite capacity. A decrease in adsorption capacity occurred only if a coagulant concentration less than optimal was applied. Removal efficiency then decreased by around 10%. It was concluded that flocculation followed by adsorption with zeolites is an effective treatment method for this kind of wastewater. PMID:15276754

Metes, A; Kovacevi?, D; Vujevi?, D; Papi?, S

263

Gold Nanoclusters Confined in a Supercage of Y Zeolite for Aerobic Oxidation of HMF under Mild Conditions.  

PubMed

Au nanoclusters with an average size of approximately 1?nm size supported on HY zeolite exhibit a superior catalytic performance for the selective oxidation of 5-hydroxymethyl-2-furfural (HMF) into 2,5-furandicarboxylic acid (FDCA). It achieved >99?% yield of 2,5-furandicarboxylic acid in water under mild conditions (60?°C, 0.3?MPa oxygen), which is much higher than that of Au supported on metal oxides/hydroxide (TiO2 , CeO2 , and Mg(OH)2 ) and channel-type zeolites (ZSM-5 and H-MOR). Detailed characterizations, such as X-ray diffraction, transmission electron microscopy, N2 -physisorption, and H2 -temperature-programmed reduction (TPR), revealed that the Au nanoclusters are well encapsulated in the HY zeolite supercage, which is considered to restrict and avoid further growing of the Au nanoclusters into large particles. The acidic hydroxyl groups of the supercage were proven to be responsible for the formation and stabilization of the gold nanoclusters. Moreover, the interaction between the hydroxyl groups in the supercage and the Au nanoclusters leads to electronic modification of the Au nanoparticles, which is supposed to contribute to the high efficiency in the catalytic oxidation of HMF to FDCA. PMID:23999985

Cai, Jiaying; Ma, Hong; Zhang, Junjie; Song, Qi; Du, Zhongtian; Huang, Yizheng; Xu, Jie

2013-09-02

264

Modified Copper Soap Solvent Extraction Method for Measuring Free Fatty Acids in Milk  

Microsoft Academic Search

A modified copper soap method was developed to provide a sensitive, rapid method for determining the free fatty acids in milk and estimating the intensity of lipolyzed flavor. The modification is simpler and more rapid than the original copper soap method. Only a small sample (.5 ml) of milk is needed for this colori- metric test, so it would be

W. F. Shipe; G. F. Senyk; K. B. Fountain

1980-01-01

265

Pipes and wiring: the regulation of copper uptake and distribution in yeast.  

PubMed

Copper is required for processes as conserved as respiration and as specialized as protein modification. Recent exciting findings from studies in yeast cells have revealed the presence of specific pathways for copper transport, trafficking and signal transduction that maintain the delicate balance of this essential yet toxic metal ion. PMID:10603486

Labbé, S; Thiele, D J

1999-12-01

266

Synthesis of NaY zeolite on preformed kaolinite spheres. Evolution of zeolite content and textural properties with the reaction time  

SciTech Connect

The synthesis of NaY zeolite was carried out on fired kaolinite microspheres. Changes in porosity, chemical composition, and crystallinity of the solid show zeolite growth on both internal and external microsphere surfaces. It was also observed that, as a consequence of the alkaline treatment, the SiO[sub 2]/Al[sub 2]O[sub 3] ratio in the solid diminishes prior to the appearance of the zeolite, but increases when the zeolite begins to crystallize.

Basaldella, E.I.; Bonetto, R.; Tara, J.C. (Centro de Investigacion y Desarrollo en Procesos Cataliticos, La Plata (Argentina))

1993-04-01

267

A correlation of the acidity and catalytic activity of zeolites  

SciTech Connect

This paper obtains the acidity spectra of modernites and SVK-zeolites from the heats of adsorption of NH/sub 3/ at 300 C and compares the catalytic activity of these zeolites with the cracking of n-octane and the isomerization of o-xylene. It is shown that the calculation of the specific catalytic activity of centers of different strengths by the method of regional rates allows one to predict the activity of the zeolites from the acidity spectra. It follows from the calculation that only the centers of Bronsted acidity are active towards cracking but that the centers of Lewis acidity are also active towards isomerization.

Klyachko, A.L.; Brveva, T.R.; Glonti, G.O.; Kapustin, G.I.; Rubinshtein, A.M.

1985-12-01

268

Zeolite-filled PDMS membranes. 1. Sorption of halogenated hydrocarbons  

SciTech Connect

Aiming at a more thorough understanding of the influence of zeolite fillers in PDMS membranes on the pervaporation of chlorinated hydrocarbons from aqueous solutions, the sorption aspect of this separation process was studied. Firstly, the sorption of water and five different chlorinated hydrocarbons was investigated in the zeolite and the polymer separately. Secondly, the composite system was considered and conclusions were drawn concerning interactions at the zeolite-polymer interphase. Finally, the sorption results obtained on the self-synthesized membranes were compared with measurements on commercially available PDMS membranes (GFT). 23 refs., 11 figs., 3 tabs.

Vankelecom, I.F.J.; Dotermont, C.; Morobe, M.; Uytterhoeven, J.B.; Vandecasteele, C. [Katholieke Universiteit Leuven (Belgium)

1997-03-20

269

Low-frequency modes of ferrocene in zeolite Y  

NASA Astrophysics Data System (ADS)

Using the position of ferrocene in zeolite Y as found from diffraction, we calculate the vibration modes of the ferrocene molecule as a whole, and the internal rotation of the ferrocene C5H5 rings with respect to each other of a ferrocene molecule in a Y-type zeolite using density functional theory. We compare our computational results with inelastic neutron scattering. We are able to identify two translational modes. The other modes lie at higher energies and are overlaid by motions arising from the flexibility of the zeolite framework.

Kemner, E.; de Vroege, C. F.; Telling, M.; de Schepper, I. M.; Kearley, G. J.

270

Adsorption of volatile hydrocarbons on natural zeolite-clay material  

Microsoft Academic Search

This study investigated the vapor-phase sorption of hydrocarbons (HC) of various chemical nature (n-hexane, iso-octane, benzene,\\u000a toluene and p-xylene) on zeolite-clay material (ZCM) of Tatarsky-Shatrashansky deposit (Tatarstan, Russia). For comparison,\\u000a we also studied HC sorption on natural high-grade zeolite (Z) of St. Cloud Mine (New Mexico, USA), two local bentonite clays\\u000a and synthetic zeolite-molecular sieve Ms5A. As a result, sorption

Irina Breus; Alexandra Denisova; Sergey Nekljudov; Vladimir Breus

2008-01-01

271

Method of preparing sodalite from chloride salt occluded zeolite A  

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 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

272

The influence of zinc ions discharged in a non-aqueous cell on a copper catalyst on the rate of cyclohexanol dehydrogenation reaction  

Microsoft Academic Search

Results of studies on the influence of a copper catalyst modification with zinc ions on the activity in the reaction of cyclohexanol dehydrogenation are presented. The modification has been performed by electrochemical discharging-insertion of zinc ions on a copper electrode in a non-aqueous cell. It has been demonstrated that the catalyst activity depends on the amount of discharged zinc ions

Andrzej Stokiosa; Janusz ZajÇcki; Grzegorz Wilczy?ski; Anna Wójtowicz; Stefan S. Kurek

1996-01-01

273

Evaluation of natural zeolite as microorganism support medium in nitrifying batch reactors: influence of zeolite particle size.  

PubMed

An evaluation of natural zeolite as a microorganism carrier in nitrifying reactors operated in batch mode was carried out. Specifically, the influence of zeolite particle sizes of 0.5, 1.0 and 2.0 mm in diameter on microorganism adherence to zeolite, ammonium adsorption capacity and the identification of microbial populations were assessed. The greatest amount of total biomass adhered was observed for a zeolite particle size of 1 mm (0.289 g) which was achieved on the 12th day of operation. The highest ammonium adsorption capacity was observed for a zeolite particle size of 0.5 mm, which was 64% and 31% higher than that observed for particle sizes of 1.0 and 2.0 mm, respectively. The maximum de-sorption values were also found for a zeolite particle size of 0.5 mm, although when equilibrium was reached the ammonium concentrations were similar to those observed for a zeolite particle size of 1.0 mm. It was also found that the experimental data on ammonium adsorption fitted very well to the Freundlich isotherm for the three particle sizes studied. Finally, the nitrifying reactors showed similar microbial populations independently of the particle size used as microorganism carrier. The dominant bacterial community was Gammaproteobacteria making up 80% of the total population found. Betaproteobacteria were also identified and made up 12% approx. of the total population. Ammonium Oxidant Betaproteobacteria and Nitrobacter were also detected. PMID:22320694

Mery, C; Guerrero, L; Alonso-Gutiérrez, J; Figueroa, M; Lema, J M; Montalvo, S; Borja, R

2012-01-01

274

Crystalline galliosilicate with the zeolite omega structure  

SciTech Connect

This patent describes a process for preparing a crystalline, galliosilicate molecular sieve free of an organic templating agent and having the zeolite omega structure. It comprises mixing a hydrogel free of an organic templating agent and having the following oxide mole ratios of components: SiO{sub 2}/Ga{sub 2}O{sub 3} = 5 to 40, M{sub 2}O/Ga{sub 2}O{sub 3} = 2 to 10, H{sub 2}O/Ga{sub 2}O{sub 3} = 80 to 800 with a galliosilicate solution free of an organic templating agent and substantially free of alumina, the solution having the following oxide mole ratios of components SiO{sub 2}/Ga{sub 2}O{sub 3} = 5 to 30, M{sub 2}O/Ga{sub 2}O{sub 3} = 6 to 20, H{sub 2}O/Ga{sub 2}O{sub 3} = 200 to 800 to form a mixture of the hydrogel and the solution, wherein M is an alkali metal and the mixture has oxide mole ratios of components falling within the same ranges as the oxide mole ratios of components in the hydrogel; and crystallizing the mixture to form a galliosilicate molecular sieve free of an organic templating agent and having the zeolite omega structure.

Occelli, M.L.

1991-07-09

275

Gallium Zeolites for Light Paraffin Aromatization  

SciTech Connect

The primary original goal of this project was to investigate the active state of gallium-containing MFI catalysts for light paraffin aromatization, in particular the state of gallium in the active material. Our original hypothesis was that the most active and selective materials were those which contained gallium zeolitic cations, and that previously reported conditions for the activation of gallium-containing catalysts served to create these active centers. We believed that in high silica materials such as MFI, ion-exchange is most effectively accomplished with metals in their 1+ oxidation state, both because of the sparsity of the anionic ion-exchange sites associated with the zeolite, and because the large hydration shells associated with aqueous 3+ cations hinder transport. Metals such as Ga which commonly exist in higher oxidation states need to be reduced to promote ion-exchange and this is the reason that reduction of gallium-containing catalysts for light paraffin aromatization often yields a dramatic enhancement in catalytic activity. We have effectively combined reduction with ion-exchange and we term this combined process ''reductive solid-state ion-exchange''. Our hypothesis has largely been proven true, and a number of the papers we have published directly address this hypothesis.

Price, G.L.; Dooley, K.M.

1999-02-10

276

Electron hole formation in acidic zeolite catalysts  

NASA Astrophysics Data System (ADS)

The formation of an electron hole on an AlO4H center of the H-ZSM-5 zeolite has been studied by a hybrid quantum mechanics/shell-model ion-pair potential approach. The Becke-3-Lee-Yang-Parr (B3LYP) and Becke-Half&Half-Lee-Yang-Parr (BHLYP) hybrid density functionals yield electron holes of different nature, a delocalized hole for B3LYP and a hole localized on one oxygen atom for BHLYP. Comparison with coupled cluster calculations including single and double substitutions and with perturbative treatment of triple substitutions CCSD(T) and with experimental data for similar systems indicate that the localized description obtained with BHLYP is more accurate. Generation of the electron hole produces a substantial geometry relaxation, in particular an elongation of the Al-O distance to the oxygen atom with the unpaired electron. The zeolite framework stabilizes the positive charge by long-range effects. Our best estimates for the vertical and adiabatic ionization energies are 9.6-10.1 and 8.4-8.9 eV, respectively. Calculations for silicalite, the all-silica form of ZSM-5, also yield a localized electron hole, but the energy cost of the process is larger by 0.6-0.7 eV. The deprotonation energy of H-ZSM-5 is found to decrease from 12.86 to 11.40 eV upon electron hole formation.

Solans-Monfort, Xavier; Branchadell, Vicenç; Sodupe, Mariona; Sierka, Marek; Sauer, Joachim

2004-09-01

277

Molecular simulations of adsorption isotherms of small alkanes in FER, TON, MTW and DON-type zeolites  

Microsoft Academic Search

Computer simulations are a useful tool in the study of the adsorption of alkanes in zeolites, provided the zeolite–alkane interactions are described in an adequate manner. MFI-type zeolites are among the most frequently studied types of zeolite. Consequently, zeolite specific force fields are often parameterized using experimental data obtained on MFI-type zeolites. In this paper we examine whether these force

Jean-Marie B Ndjaka; Gooitzen Zwanenburg; Berend Smit; Merijn Schenk

2004-01-01

278

Sodium removal and catalytic properties of HNaZSM-20 zeolite. Comparison with Y zeolite  

Microsoft Academic Search

A series of HNaZSM-20 catalysts with a varying amount of sodium cations were studied. The samples were prepared by ion exchange starting with a NaZSM-20 sample. The observedammonium-sodium exchange efficiency was slightly higher for ZSM-20 than for Y zeolite. The HNaZSM-20 series presentedhigher cracking activities in then-heptane transformation than the corresponding HNaY series. A decrease in theselectivity for coke deposition

J. M. Lopes; F. Lemos; E. Derouane; F. Ramôa Ribeiro

1996-01-01

279

Zeolites: Their Synthesis and Conditions of Formation in Nature.  

National Technical Information Service (NTIS)

The book offers extensive discussion of physicochemical aspects of zeolite formation, phase interactions, crystallization patterns, syntheses, and definitions of conditions conducive to their formation in natural environments. Based on comparison between ...

E. E. Senderov N. I. Khitarov

1973-01-01

280

Anchoring strategies for bimetallic species in zeolites. Progress report.  

National Technical Information Service (NTIS)

We explore a new approach by introducing heterobinuclear organometallic compounds for linking catalytic functions to zeolite frameworks. With two different metals present, the complexes are being anchored to the support via one oxophilic metal, ligand exc...

T. Bein

1993-01-01

281

Applications of NMR spectroscopy to the Study of Zeolite Synthesis.  

National Technical Information Service (NTIS)

NMR spectroscopy is a powerful technique for identifying the structure and concentration of silicate and aluminosilicate anions in gels and solution used for zeolite synthesis. A review is presented of the types of species that have been observed and the ...

A. T. Bell

1989-01-01

282

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

2007-05-31

283

Surface Properties of Offretite and ZSM-34 Zeolites.  

National Technical Information Service (NTIS)

Offretite and ZSM-34 zeolites, with nominally the same crystal structure, have been synthesized and their catalytic behavior toward conversion of methanol to hydrocarbons determined. ZSM-34 is found to be highly selective toward conversion to ethylene rel...

M. L. Occelli R. A. Innes T. M. Apple B. C. Gerstein

1983-01-01

284

Metal loaded zeolite adsorbents for hydrogen cyanide removal.  

PubMed

Metal (Cu, Co, or Zn) loaded ZSM-5 and Y zeolite adsorbents were prepared for the adsorption of hydrogen cyanide (HCN) toxic gas. The results showed that the HCN breakthrough capacity was enhanced significantly when zeolites were loaded with Cu. The physical and chemical properties of the adsorbents that influence the HCN adsorption capacity were analyzed. The maximal HCN breakthrough capacities were about the same for both zeolites at 2.2 mol of HCN/mol of Cu. The Cu2p XPS spectra showed that the possible species present were Cu2O and CuO. The N1s XPS data and FT-IR spectra indicated that CN(-) would be formed in the presence of Cu+/Cu2+ and oxygen gas, and the reaction product could be adsorbed onto Cu/ZSM-5 zeolite more easily than HCN. PMID:23923791

Ning, Ping; Qiu, Juan; Wang, Xueqian; Liu, Wei; Chen, Wei

2013-04-01

285

Prediction of Zeolite Types Based on Structural Data.  

NASA Astrophysics Data System (ADS)

Application of knowledge discovery methods in the search of information contained in databases is an emerging field in materials science that plays an important role on facilitating data analysis. In this study we propose a model for identification of the zeolite mineral type based on the topological analysis of the underlying crystal structure. High-throughput generation of topological descriptors is derived from the Delaunay tessellation of zeolite supercells. Based on these descriptors, our Zeolite-Structure-Predictor is trained for classifying zeolite crystals into twenty two different types of minerals and is based on a random forest model constructed with attributes that include tetrahedrality index, in-sphere volume, average edge, frequency of occurrence and probability of oxygen rich selected simplices. The underlying crystal structure data used for this study are included in the Inorganic Crystal Structural Database (ICSD).

Lach-Hab, M.; Carr, D. A.; Vaisman, I.; Blaisten-Barojas, E.

2008-03-01

286

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

287

Benzylation of benzene with benzyl alcohol on zeolite catalysts  

Microsoft Academic Search

The catalytic liquid phase benzylation of benzene to diphenylmethane (DPM) with benzyl alcohol (BnOH) was investigated over various zeolite catalysts (HSZ 600 mordenite, CBV 20A mordenite, H-beta zeolites with Si\\/Al of 10.8 and 35.8, respectively) at 353–423K and under atmospheric pressure, using three reaction methodologies: (A) by adding all benzyl alcohol at the beginning of the reaction, (B) by dropwise

N. Candu; M. Florea; S. M. Coman; V. I. Parvulescu

2011-01-01

288

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

289

Synthesis of mesoporous zeolite single crystals with cheap porogens  

Microsoft Academic Search

Mesoporous zeolite (silicalite-1, ZSM-5, TS-1) single crystals have been successfully synthesized by adding soluble starch or sodium carboxymethyl cellulose (CMC) to a conventional zeolite synthesis system. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption analysis, 27Al magic angle spinning nuclear magnetic resonance (27Al MAS

Haixiang Tao; Changlin Li; Jiawen Ren; Yanqin Wang; Guanzhong Lu

2011-01-01

290

Stability of silver cluster in zeolite A and Y catalysts  

NASA Astrophysics Data System (ADS)

Chemical state analysis of silver species in Ag+ exchanged zeolite A and Y catalysts were carried out by means of XAFS and UV-Vis spectroscopies. Order of thermal stability of silver cluster was Ag(50%)-Y > Ag(60%)-A > Ag(100%)-A, which was consistent with the previous 1H NMR study for stability of chemisorbed hydrogen species. The three shell model (Ag-O, Ag-Ag, and Ag-Al/Si) of silver cluster in zeolites was proposed.

Yamamoto, Takashi; Takenaka, Sakae; Tanaka, Tsunehiro; Baba, Toshihide

2009-11-01

291

Structured carbon adsorbents from clay, zeolite and mesoporous aluminosilicate templates  

Microsoft Academic Search

Porous carbons templated from inorganic materials such as zeolites and mesoporous molecular sieves received considerable attention in the last decade. In this context, we discuss the effects of different templating structures on the carbons yielded. We describe templating using a commercial cationic clay (Wyoming bentonite), a commercial zeolite (Tosoh H-Beta) and a synthetic mesoporous aluminosilicate (Al-MCM-48), as exemplars of the

P. M Barata-Rodrigues; T. J Mays; G. D Moggridge

2003-01-01

292

Zeolites and mesoporous materials as advanced functional material  

Microsoft Academic Search

With their unique regular channel system, porous materials offer a wide range of applications as host-guest system ranging from membranes with a molecular sieve function to devices with laser or sensor function. The state of the art of the development of zeolites and zeolite-like materials as advanced materials with (i) separation, (ii) electric\\/electronic, and (iii) optical functions is evaluated.

2004-01-01

293

Adsorption of cobalt on some natural zeolites occurring in ?SFR  

Microsoft Academic Search

The subject of this paper was to study Co2+-ion removal from aqueous solutions by means of natural mordenite and clinoptilolite. The mentioned zeolites were of Slovak origin (SFR). The static and dynamic equilibrium adsorption of Co2+-ions by zeolites, the influence of pH, quality and quantity of interfering ions on adsorbate\\/adsorbent system were investigated. The influence of flow rate, activation and

E. Chmielewská-Horváthová; J. Lesný

1992-01-01

294

Isomerization of ?-pinene over dealuminated ferrierite-type zeolites  

Microsoft Academic Search

Isomerization of ?-pinene was performed on a series of dealuminated ferrierite (FER)-type zeolites in liquid phase at 363 K using a batch reactor. The course of zeolite dealumination was followed in detail using 29Si, 27Al, 1H MAS NMR, XRD, FTIR, and sorption of nitrogen. The ammonium form of FER was dealuminated with aqueous solutions of HCl. While retaining the crystallinity

Rafal Rachwalik; Zbigniew Olejniczak; Jian Jiao; Jun Huang; Michael Hunger; Bogdan Sulikowski

2007-01-01

295

Skeletal isomerization of 1?butene on synthetic clinoptilolite zeolite  

Microsoft Academic Search

A pure, highly crystalline clinoptilolite (CLI) zeolite with a Si\\/Al ratio of 5.8 has been synthesized using a small amount\\u000a (1%) of seed crystals and tested as a catalyst for the skeletal isomerization of 1?butene at 623–723 K at atmospheric pressure.\\u000a The catalytic results are compared to those obtained from a ferrierite (FER) zeolite with a Si\\/Al ratio of 7.6.

Gon Seo; Byung Joon Ahn; Suk Bong Hong; Young Sun Uh

1998-01-01

296

Thermodynamics of nitrogen adsorption on the zeolite H-FER  

Microsoft Academic Search

Adsorption (at a low temperature) of nitrogen on the protonic zeolite H-FER results in hydrogen bonding of the adsorbed N2 molecules with the zeolite Si(OH)Al Brønsted acid groups. This hydrogen bonding interaction leads to activation, in the IR, of the fundamental NN stretching mode, which appears at 2331 cm-1. From the infrared spectra taken over a temperature range, while simultaneously

M. Rodríguez Delgado; C. Otero Areán

2007-01-01

297

Thermodynamics of nitrogen adsorption on the zeolite H-FER  

Microsoft Academic Search

Adsorption (at a low temperature) of nitrogen on the protonic zeolite H-FER results in hydrogen bonding of the adsorbed N2 molecules with the zeolite Si(OH)Al Brønsted acid groups. This hydrogen bonding interaction leads to activation, in the IR, of the fundamental NN stretching mode, which appears at 2331cm?1. From the infrared spectra taken over a temperature range, while simultaneously recording

M. Rodríguez Delgado; C. Otero Areán

2007-01-01

298

Tissue engineering scaffolds containing embedded fluorinated-zeolite oxygen vectors  

Microsoft Academic Search

Efficient oxygen supply is a continuing challenge for the fabrication of successful tissue engineered constructs with clinical relevance. In an effort to enhance oxygen delivery we report the feasibility of using fluorinated zeolite particles embedded in three-dimensional (3-D) polyurethane scaffolds as novel oxygen vectors. First, 1H,1H,2H,2H-perfluorodecyltriethoxysilane was successfully coupled to zeolite framework particles to examine the dose-dependent dissolved oxygen concentration.

Dawit G. Seifu; Tayirjan T. Isimjan; Kibret Mequanint

2011-01-01

299

Expanded-Volume Phases of Silicon: Zeolites without Oxygen  

Microsoft Academic Search

By reducing the (4;2)-connected regular 3D nets of zeolites to 4-connected nets, we introduce a variety of new expanded structures of elemental Si. An ab-initio molecular dynamics method is used to determined the optimized geometries, energetics, and electronic properties of the proposed structures. It is found that Si structures derived from those of Group 6 (5-ring) zeolites, are particularly low

Alexander A. Demkov; Otto F. Sankey

1996-01-01

300

Surface modified zeolite, a novel carrier material for Azotobacter chroococcum  

Microsoft Academic Search

A new immobilization matrix based on zeolite has been developed to immobilize Azotobacter chroococcum, for fixing nitrogen, with an intention to hold the cells in the root zone of the plants and to protect them under stressful\\u000a conditions. The matrix has been developed by modifying the surface of the zeolite with surfactant. This enhances the hydrophobicity\\u000a of the material and

Prachi Joshi; Sadhana Rayalu; Amit Bansiwal; Asha A. Juwarkar

2007-01-01

301

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

302

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

303

An analysis of commerical zeolite catalysts by multinuclear NMR  

SciTech Connect

This work involves studying two commercial hydrocracking catalysts by solid state multinuclear NMR silicon 29 and aluminum 27 with the goal of developing a method of determining the fraction zeolite in the catalysts. The zeolite fraction is known to be one of the faujasite zeolites type X or Y. The clay matrix of the catalyst is assumed to be kaolinite. Fresh, air-exposed commercial hydrocracking catalysts were provided by Phillips Petroleum. Sample 33351-86 was known to be a physical mixture of a Y zeolite and a clay matrix. The other catalyst, 33351-20, was composed of a faujasite zeolite grown within a clay matrix. Both were suspected of being about 20 wt % zeolite. Nothing is known about the state of pretreatment or cation exchange. A portion of each catalyst was calcined in a porcelain crucible in air at 500{degree}C for two hours with a hour heating ramp preceding and a two hour cooling ramp following calcination. 64 refs., 21 figs., 8 tabs.

Flanagan, L.

1990-09-21

304

Chloroform vapour sensor based on copper\\/polyaniline nanocomposite  

Microsoft Academic Search

Chemically synthesised copper\\/polyaniline (PANi) nanocomposite has been utilised as a chloroform sensor for ppm level vapour concentration. The response in terms of increase in dc electric resistance on exposure to chloroform vapours has been observed. The FT–IR spectra of nanocomposite on exposure to chloroform show remarkable modifications in the far IR region indicating the interaction of chloroform with metal cluster.

Satish Sharma; Chetan Nirkhe; Sushama Pethkar; Anjali A. Athawale

2002-01-01

305

Recovery of copper powder from copper bleed electrolyte of an Indian copper smelter by electrolysis  

Microsoft Academic Search

Copper bleed solution generated from an Indian Copper smelter contains high amount of copper and nickel along with several impurities. Attempts have been made to develop a new process for the production of pure copper powder from such streams. The purity of the electrolytic copper powder produced from such bleed streams was found to be 99.93%. Properties such as compact

Archana Agrawal; Sarita Kumari; D. Bagchi; V. Kumar; B. D. Pandey

2007-01-01

306

How Bacteria Handle Copper  

Microsoft Academic Search

Copper in biological systems presents a formidable problem: it is essential for life, yet highly\\u000a reactive and a potential source of cell damage. Tight control of copper is thus a cellular necessity.\\u000a To meet this challenge, cells have evolved pumps for transmembranous transport, chaperones for intracellular\\u000a routing, oxidases and reductases to change the oxidation state of copper, and regulators to control gene\\u000a expression

David Magnani; Marc Solioz

307

The effect of Al content of zeolite template on the properties and hydrogen storage capacity of zeolite templated carbons  

Microsoft Academic Search

We report on the effectiveness of faujasite (Y type) zeolites, with varying Al content, as template for the nanocasting of high surface area zeolite templated carbon (ZTC) via well established chemical vapour deposition routes. The Al content (in the Si\\/Al ratio range of 1.36–15) was found to have a significant effect on the porosity, nature and hydrogen uptake of the

Nurul Alam; Robert Mokaya

2011-01-01

308

Encapsulation of gases by zeolites. 2. Encapsulation of nitrogen and oxygen by small-cavity type a zeolites  

Microsoft Academic Search

1.It has been established experimentally that at 740 K and ~90 MPa, approximately three molecules of N2 or O2 are adsorbed in a small cavity of NaA zeolite.2.Analysis of the desorption curves indicates that for CsNaA zeolite (degree of exchange of Na+ by Cs+ 70%) it is impossible to distinguish quantitatively between adsorption in the large and the small cavities.

I. A. Kalinnikova; A. A. Pribylov; V. V. Serpinskii; T. N. Ivanova; S. M. Kalashnikov

1988-01-01

309

Effect of zeolite geometry for propane selective oxidation on cation electrostatic field of Ca 2+ exchanged zeolites  

Microsoft Academic Search

The effects of zeolite geometry on propane selective oxidation were studied by in situ infrared spectrometry on Ca2+ exchanged Y, MOR and ZSM5 zeolites. Oxygen and propane adsorption at room temperature, revealed that the electrostatic field of Ca2+ increased in the order CaY

Jiang Xu; Barbara L. Mojet; Leon Lefferts

2006-01-01

310

Zeolite cryopumps for hydrogen isotopes transportation  

SciTech Connect

Cryosorption pump is very convenient means for hydrogen isotope transportation, since a cryopump combines a vacuum pump, compressor and temporary storage reservoir of hydrogen isotopes. We have studied zeolites as the cryosorbent for hydrogen isotope fore-vacuum pumping. The prototype of the cryosorption pump was designed, made and tested. It is shown that synthetic chabazite CaET-4B has the highest adsorption capacity in relation to hydrogen isotopes in the low pressure region. The equation of the adsorption isotherms was obtained. The results of the testing and operation of the cryopump for hydrogen isotopes transport are described. The pump is simple, reliable and allows to reduce the losses of deuterium and exclude tritium release to atmosphere and the formation of tritium wastes. 13 refs., 4 figs., 2 tabs.

Alekseev, I.A.; Karpov, S.P.; Trenin, V.D. [Petersburg Nuclear Physics Inst., Gatchina (Russian Federation)

1995-10-01

311

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

312

Mitigation of copper corrosion and agglomeration in APS process water systems.  

SciTech Connect

Copper corrosion has been observed in process water (PW) systems at the Advanced Photon Source (APS) dating to the early postcommissioning phase of the project. In time, copper corrosion products agglomerated significantly in certain preferred locations. Significant agglomerations (or deposits) can occur in copper cooling passages such as magnet conductors and x-ray absorbers having relatively large length-to-diameter ratios and where heat is removed by water cooling. Such agglomerations also occur at restrictions found in noncopper system components such as valve seats, fixed orifices, pump seal faces, etc. Modifications to the APS process water system that significantly reduce the rate of copper corrosion are discussed. These modifications have not prevented corrosion altogether. Other means used to prevent component clogging and malfunction as a result of current copper corrosion rates are listed.

Dortwegt, R.; Putnam, C.; Swetin, E.

2002-10-10

313

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

2007-03-23

314

Case Series Describing Thermal Injury Resulting From Zeolite Use for Hemorrhage Control in Combat Operations.  

National Technical Information Service (NTIS)

Four cases are presented to illustrate cutaneous burns sustained with the use of zeolite in the treatment of major hemorrhage secondary to combat wounds. Zeolite, a microporous crystalline aluminosilicate granular hemostatic agent, can cause secondary the...

A. Pusateri J. McManus K. J. Knoop T. Hurtado

2007-01-01

315

Mesostructured Zeolitic Materials, and Methods of Making and Using the Same.  

National Technical Information Service (NTIS)

One aspect of the present invention relates to mesostructured zeolites. The invention also relates to a method of preparing mesostructured zeolites, as well as using them as cracking catalysts for organic compounds and degradation catalysts for polymers.

J. Y. Ying J. G. Martinez

2004-01-01

316

Neutron Diffraction Studies of the Hydrogen Bonding and Water Molecules in Zeolites.  

National Technical Information Service (NTIS)

Neutron diffraction studies have been completed at different temperatures for all of the fibrous zeolites (natrolite, scolecite, edingtonite, thomsonite) and completed or in progress for several other zeolites with ordered or disordered frameworks (brewst...

G. Artioli J. V. Smith A. Kvick J. J. Pluth K. Stahl

1984-01-01

317

Control of CO2 adsorption heats by the Al distribution in FER zeolites.  

PubMed

Proper combination of template and optimized reaction conditions provides zeolite FER with homogeneous distribution of Al in the framework; this results in a new zeolite adsorbent exhibiting a constant heat of CO(2) adsorption. PMID:22134383

Nachtigall, Petr; Grajciar, Lukáš; Pérez-Pariente, Joaquín; Pinar, Ana B; Zukal, Arnošt; ?ejka, Ji?í

2011-12-01

318

Conversion of coal fly ash into zeolite and heavy metal removal characteristics of the products  

Microsoft Academic Search

Fly ash obtained from a power generation plant was used for synthesizing zeolite. Zeolites could be readily synthesized from\\u000a the glassy combustion residues and showed potential for the removal of heavy metal ions. By the use of different temperatures\\u000a and NaOH concentration, five different zeolites were obtained: Na-P1, faujasite, hydroxy sodalite, analcime, and cancrinite.\\u000a The synthesized zeolites had greater adsorption

Min-Gyu Lee; Gyeongbeom Yi; Byoung-Joon Ahn; Felicity Roddick

2000-01-01

319

PENGARUH KANDUNGAN Ca PADA CaO-ZEOLIT TERHADAP KEMAMPUAN ADSORPSI NITROGEN  

Microsoft Academic Search

In industry, Ca zeolite is used as nitrogen selective adsorbent with the use of PSA (Pressure Swing Adsorption)\\/VSA (Vacuum Swing Adsorption) methods. Natural zeolite modified to be Cao-zeolite by ion exchange process using Ca(OH)2. Adsorption test was done on CaO-zeolite with different Ca concentration to understand how it's adsorption phenomena on oxygen and nitrogen. Adsorption test has been done for

M. Nasikin; Tania Surya; Utami dan Agustin

320

Modified zeolite membrane reactor for high temperature water gas shift reaction  

Microsoft Academic Search

A porous ?-alumina tube supported MFI-type zeolite membrane was modified by depositing molecular silica species in the zeolitic channels via in situ catalytic cracking of methyl diethoxysilane at a limited number of active sites. The modified zeolite membrane exhibited a H2\\/CO2 perm-selectivity of 68.3 with H2 permeance of 2.94×10?7mol\\/m2sPa at 550°C. The modified zeolite membrane tube was packed with a

Zhong Tang; Seok-Jhin Kim; Gunugunuri K. Reddy; Junhang Dong; Panagiotis Smirniotis

2010-01-01

321

Methylammonium-FAU zeolite: Investigation of the basic sites in base catalyzed reactions and its performance  

Microsoft Academic Search

The basicity of methylammonium-faujasite zeolites (FAU) was evaluated in the Knoevenagel and Claisen–Schmidt condensation reactions and in the alcoholysis of propylene oxide with methanol. The basic character of FAU zeolites (Y zeolite with Si\\/Al=2.5 and X zeolite with Si\\/Al=1.4) was systematically altered by incorporating cesium and methylammonium cations, which were located in charge compensation sites. In all three reactions, methylammonium-FAU

Leandro Martins; Wolfgang Hölderich; Dilson Cardoso

2008-01-01

322

Zeolite-filled polyimide membrane containing 2,4,6-triaminopyrimidine  

Microsoft Academic Search

Interfacial void-free Matrimid polyimide (PI) membranes filled with zeolites were prepared by introducing 2,4,6-triaminopyrimidine (TAP). TAP enhanced the contact of zeolite particles with polyimide chains presumably by forming hydrogen bonding between them. The threshold amount of TAP, needed to depress totally the void formation, varied with zeolite type in the order of zeolite 4A?13X

Hyun Hang Yong; Hyun Chae Park; Yong Soo Kang; Jongok Won; Woo Nyun Kim

2001-01-01

323

Two Ethylenediamine-Templated Zeolite-Type Structures in Zinc Arsenate and Cobalt Phosphate Systems  

Microsoft Academic Search

Hydrothermal syntheses and X-ray crystal structures of two zeolite-type structures encapsulating protonated ethylenediamine and consisting of three-dimensional 8-ring channels are presented. UCSB-3 and ACP-3 are isostructural and have zeolite-type topologies. The framework consists of cross-linked bifurcated hexagonal-square (bhs) chains, similar to that found in the zeolite-type structure, AlPO4-D. Alternatively, like a number of zeolite structures such as ABW, gismondine, merlinoite,

Xianhui Bu; Pingyun Feng; Thurman E. Gier; Galen D. Stucky

1998-01-01

324

Reaction of propionaldehyde over Rh-Y zeolite  

SciTech Connect

During the desorption of propionaldehyde from the Rh-Y zeolite into a He-CO(10%) stream, the concentration of propionaldehyde decreased with desorption time. n-Propanol formation was enhanced in the desorption of propionaldehyde into a He-H/sub 2/(10%) stream, while no appreciable enhancement was observed in the desorption into a He-H/sub 2/(10%)-CO(10%) stream. A faster decrease in the concentration of propionaldehyde was observed during the desorption into a helium stream than the desorption into the He-CO stream. In the desorption into the helium stream, formation of pentene was observed. However, no formation of pentene was observed in the desorption into a He-C/sub 2/H/sub 4/(10%) stream. In the desorption into a He-C/sub 3/H/sub 6/(10%) stream, the rate of pentene formation was lower than that in the desorption into the helium stream. These results suggest that the pentene is not formed by ethylene-propylene codimerization. The reduced RhCl/sub 3//SiO/sub 2/ catalyst which was physically mixed with the Na-Y zeolite showed comparable activity for pentene formation to that of Rh-Y zeolite in the reaction of propionaldehyde. However, neither the RhCl/sub 3//SiO/sub 2/ catalyst nor the Na-Y zeolite was effective by itself for pentene formation. The reduced RhCl/sub 3//SiO/sub 2/ and Rh-Y zeolite catalysts also showed activity for pentene formation in the reaction of 2-methyl-2-pentenal which is the product of aldol condensation of propionaldehyde. On the basis of the results, two sequential reactions, aldol condensation of propionaldehyde by the zeolite support followed by decarbonylation of 2-methyl-2-pentenal by rhodium metal particles, are proposed as a reaction path for the formation of pentene over the Rh-Y zeolite.

Takahashi, N.; Takizawa, M.; Sato, Y.

1986-03-01

325

Catalytic desulfurization of organic sulfur compounds over zeolite catalysts  

SciTech Connect

Various kinds of zeolites, such as Na-zeolites, MeY and HY, showed catalytic activity for the dehydrosulfurization of ethanethiol. The catalytic activity of MeY in the dehydrosulfurization of ethanethiol at 400/sup 0/C was changed by the kind of metal ions in the zeolites and a volcano shape order was observed between the catalytic activity and the electronegativity, Xi, of the metal ions. The order of the catalytic activity was NaX>NaY>NaA. The changes in the activity of HY in ethanethiol dehydrosulfurization and cumene dealkylation by calcination agreed with the decrease in the Bronsted acidity determined by Ward but was independent of Lewis acidity. Me/sup 0/Y, such as Co/sup 0/Y, Ni/sup 0/Y, Cu/sup 0/Y and Ag/sup 0/Y, showed higher catalytic activity than a commercial hydrodesulfurization catalyst and the order of the activity was Ni/sup 0/Y>Co/sup 0/Y>Cu/sup 0/Y>Ag/sup 0/Y. Reduced and presulfided Me/sup 0/Y zeolites showed selective hydrodesulfurization activity for thiophene. The remarkable promoting effect of NiO and MoO/sub 3/ upon the catalytic activity of Me/sup 0/Y was not observed in the hydrodesulfurization of thiophene. Zeolite catalysts have a possibility of use as effective hydrodesulfurization catalysts for petroleum if further improvement in catalyst deactivation of Me/sup 0/Y zeolite is accomplished. The investigation of the hydrodesulfurization of thiophene over Me/sup 0/Y zeolites would become a good model to clarify the mechanism of the hydrodesulfurization of petroleum.

Sugioka, M.; Aomura, K.

1980-03-01

326

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...

327

Corrosion of Copper Pipes  

Microsoft Academic Search

Rapid pitting of the walls of copper pipes used in plumbing has resulted in several controversial overtones. The results of a study of the problem in southern California are now available in this article and should benefit the water purveyor, who is, after all, responsible for taking reasonable measures to prevent unnecessary corrosion to copper service lines

Henry Cruse; Richard D. Pomeroy

1974-01-01

328

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

329

Microwave-assisted zeolite synthesis from coal fly ash in hydrothermal process  

Microsoft Academic Search

Coal fly ashes, which include much amount of silica and alumina, can be converted into zeolite by hydrothermal alkaline treatment. In the present work, the effect of microwave irradiation on the zeolite formation was investigated with emphasis on the change in yield of zeolite during the reaction. The fly ash was mixed with 2M NaOH solution and heated by oil

Miki Inada; Hidenobu Tsujimoto; Yukari Eguchi; Naoya Enomoto; Junichi Hojo

2005-01-01

330

Hydrocarbon cracking with catalyst containing a CO oxidation promoter in ultra-stable zeolite particles  

Microsoft Academic Search

A cracking catalyst for promoting the oxidation of carbon monoxide to carbon dioxide during regeneration of the catalyst by the burning of coke therefrom, comprises two distinct crystalline aluminosilicate zeolite particles embedded in an inorganic porous oxide matrix material. The first zeolite is the ultra-stable variety of Y-type zeolite which contains a CO oxidation promoter, such as a Group VIII

Gladrow

1979-01-01

331

Competitive adsorption of malachite green and Pb ions on natural zeolite  

Microsoft Academic Search

A natural zeolite was employed as adsorbent for removal of malachite green and Pb2+ ions from aqueous solution. A batch system was applied to study the adsorption behaviour of the dye and heavy metal in single and binary systems on the natural zeolite. Kinetic studies indicate that malachite green and Pb2+ adsorption on the natural zeolite in a single component

Shaobin Wang; Eko Ariyanto

2007-01-01

332

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

333

Microprobe study of the surface of a zeolite-containing zirconium-silicate catalyst  

SciTech Connect

X-ray microprobe techniques have been used to study the chemical and phase compositions of a zeolite-containing zirconium-silicate catalyst synthesized by introducing crystallites of the zeolite into the hydrosol and hydrogel of the zirconium silicate. It is shown that dispersion of the zeolite crystallites occurs in this process.

Mel'nikov, V.B.; Chukin, G.D.; Nefedov, B.K.

1987-02-01

334

Design and development of new zeolitic materials based on natural clinoptilolite  

Microsoft Academic Search

This paper reviews research of “natural zeolites engineering” in Cuba during the last 25 years. It is remarked that a good application derives from a deep knowledge of the natural zeolite from a particular deposit starting from the geological survey. The mining and beneficiation steps of the mineral processing are fundamental to obtain a zeolite raw material with homogeneous properties.

G. Rodríguez-Fuentes

2007-01-01

335

Preparation and characterization of mesoporous carbons using a Turkish natural zeolitic template\\/furfuryl alcohol system  

Microsoft Academic Search

The template carbonization method was utilized for the production of mesoporous carbons using a Turkish natural zeolite as a template. The major carbon precursor used was furfuryl alcohol. Furfuryl alcohol was polymerized and carbonized between 700°C and 1000°C in the channels of the natural zeolite. The structure of the zeolite template and carbons were investigated by surface analysis techniques, scanning

Billur Sakintuna; Yuda Yürüm

2006-01-01

336

Reaction Mechanisms of Lean-Burn Hydrocarbon SCR over Zeolite Catalysts  

Microsoft Academic Search

Acid zeolites loaded with transition metals have been intensively investigated as catalysts for selective catalytic reduction of NOx using hydrocarbons. Detailed insight into reaction mechanisms and zeolite effects was reached through experimentation in minireactors with simulated exhaust gas and compressed zeolite powder, detailed reaction product analysis and in situ spectroscopic investigations. Irrespective of the nature of the transition metal (Fe,

Roald Brosius; Johan A. Martens

2004-01-01

337

BETA zeolite nanowire synthesis under non-hydrothermal conditions using carbon nanotubes as template  

Microsoft Academic Search

The properties of carbon nanotubes, used as a nanometric template and as a reactor for the synthesis of BETA zeolite, have been investigated. The confinement effect of the carbon nanotubes, induced by the high aspect ratio of the tubes could be effectively used for the synthesis of one-dimensional nanowire zeolitic materials under non-hydrothermal macroscopic conditions. Zeolite material is easily recovered

Cuong Pham-Huu; Gauthier Winé; Jean-Philippe Tessonnier; Marc-Jacques Ledoux; Séverine Rigolet; Claire Marichal

2004-01-01

338

Zeolite catalysts and their use in selective catalytic reduction of NOx  

Microsoft Academic Search

The invention is directed to catalyst compositions comprising a zeolite, as well as to processes for the reduction of nitrogen oxides (NOx) employing these catalyst compositions. The catalyst compositions of the invention comprise a zeolite of the ferrierite type (FER), which zeolite is ion exchanged with Ce, in particular Ce-H-FER and are very active in the selective catalytic reduction of

G. B. F. Seijger; C. M. Van den Bleek; H. P. A. Calis

2003-01-01

339

Bactericidal activity of Ag–zeolite mediated by reactive oxygen species under aerated conditions  

Microsoft Academic Search

The bactericidal activity induced by the introduction of silver ions into zeolite was studied. Escherichia coli was used as the test microorganism. Silver ions were loaded into zeolite by the ion-exchange method. Silver-loaded zeolite was demonstrated the strong bactericidal activity. Dissolved oxygen was an essential factor for the occurrence of the bactericidal activity because the activity was observed only under

Yoshihiro Inoue; Masanobu Hoshino; Hiroo Takahashi; Tomoko Noguchi; Tomomi Murata; Yasushi Kanzaki; Hajime Hamashima; Masanori Sasatsu

2002-01-01

340

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

Microsoft Academic Search

Zeolites, crystalline porous aluminosilicates, are valued for their ability to absorb ions and molecules as well as function as catalysts. A number of laboratory experiments using zeolites filtered from a suspension of powdered laundry detergent are described. The various experiments illustrate the myriad uses of zeolites as desiccants, ion exchange materials, and catalysts.

David A. Lindquist; Alison L. Smoot

1997-01-01

341

Adsorption of carbon dioxide on alkali-modified zeolite 13X adsorbents  

Microsoft Academic Search

Shaped zeolite 13X adsorbent with kaolin as binder was hydrothermally modified in sodium hydroxide solution to improve its adsorption performance. The characterization of the product by XRD, N2 adsorption–desorption and water vapour adsorption displayed that kaolin component in zeolite adsorbent can be converted into zeolite during the alkali treatment, resulting in the modified adsorbent consisting entirely of effectual adsorption composition.

Zhonglin Zhao; Xingyu Cui; Jinghong Ma; Ruifeng Li

2007-01-01

342

In which way alkaline-earth cations enhance the nucleation of alkali-templated zeolites?  

Microsoft Academic Search

The addition of Mg2+ cations to the synthesis medium of zeolite L favours the zeolite nucleation in the same way as Ag+, an heterogeneous nucleation agent, but slows down crystal growth in the same way as other alkaline earth cations. Comparison with the synthesis of zeolite Y indicates that the promotion of nucleation by Mg2+ is related to the presence

Fatiha Hamidi; Satoshi Ohtake; Abdelkader Bengueddach; Francesco Di Renzo

2008-01-01

343

Low-temperature ozone treatment for organic template removal from zeolite membrane  

Microsoft Academic Search

The effectiveness of low temperature ozone treatment for organic template removal from MFI zeolite membranes was investigated. The aim is to establish a convenient and reliable method for zeolite membrane activation that will ensure not only high gas permselectivity but also more importantly, good reproducibility. Fifty ZSM-5 zeolite membranes were prepared for the study. The effects of ozone concentration, treatment

Samuel Heng; Prudence Pui Sze Lau; King Lun Yeung; Malik Djafer; Jean-Christophe Schrotter

2004-01-01

344

Ionic liquids and eutectic mixtures as solvent and template in synthesis of zeolite analogues  

Microsoft Academic Search

The challenges associated with synthesizing porous materials mean that new classes of zeolites (zeotypes)-such as aluminosilicate zeolites and zeolite analogues-together with new methods of preparing known zeotypes, continue to be of great importance. Normally these materials are prepared hydrothermally with water as the solvent in a sealed autoclave under autogenous pressure. The reaction mixture usually includes an organic template or

Emily R. Cooper; Christopher D. Andrews; Paul S. Wheatley; Paul B. Webb; Philip Wormald; Russell E. Morris

2004-01-01

345

Fabrication of high wettability gradient on copper substrate  

NASA Astrophysics Data System (ADS)

Copper is one of the most widely used materials in condensation heat transfer. Recently there has been great interest in improving the condensation heat transfer efficiency through copper surface modification. In this study, we describe the fabrication processes of how copper surfaces were modified to be superhydrophilic (CA ? 10°) and superhydrophobic (CA > 150°) by means of H2O2 immersion and fluorination with Teflon. The wettability gradient of copper surfaces with contact angles (CA) changing from superhydrophilic to superhydrophobic are also demonstrated. Unlike previous studies on gradient surfaces in which the wettability gradient is controlled either non-precisely or entirely uncontrolled, in this study, the contact angles along wettability gradient copper surfaces vary with a precisely designed gradient. It is demonstrated that a high wettability gradient copper surface can be successfully fabricated using photolithography to define the area ratios between superhydrophilic and superhydrophobic patterns within a short distance. The fabricated wettability gradient of copper surfaces is expected to be able to enhance the condensation heat transfer efficiency.

Huang, Ding-Jun; Leu, Tzong-Shyng

2013-09-01

346

Erythrocyte membrane proteins in copper-deficient rats  

SciTech Connect

Increased osmotic stability and decreased survivability of erythrocytes caused by Cu deficiency suggest that low copper status may lead to modification in the organization of erythrocyte membrane proteins. Accordingly Cu deficiency was produced in rats by feeding a diet containing < 1 ppm Cu. The effects of low copper status on erythrocyte membrane proteins were assessed by sodium dodecyl sulfate polyacylamide electrophoresis. A 170,000 dalton protein (170K) amounted to 2.68 +/- 0.11% of the total membrane protein in erythrocytes from copper-deficient rats (n = 25) and 1.42 +/- 0.10% in erythrocytes from rats fed adequate Cu. When erythrocyte membranes from copper-deficient rats were extracted with 0.5% (v/v) Triton X-100, 170K remained associated with the cytoskeletal proteins, spectrin and actin. Thus, copper deficiency can alter the composition of the erythrocyte cytoskeleton. Furthermore, hematocrit levels in copper-deficient rats were negatively correlated to the amount of 170K suggesting that alteration of the erythrocyte cytoskeleton may be a factor that contributes to the anemia associated with copper deficiency.

Johnson, W.T.; Kramer, T.R.

1987-05-01

347

Oxidation resistant copper  

NASA Astrophysics Data System (ADS)

Oxidation resistant particles composed of copper and at least one metal having a valence of +2 or +3 and having an intermediate lattice energy for the metal in its hydroxide form are presented. The metal is selected from nickel, cobalt, iron, manganese, cadmium, zinc, tin, magnesium, calcium and chromium. In one embodiment, the phases of copper and at least one metal in the particles are separate and the concentration of the metal is greater near the surface of the particles than inwardly thereof. Process for making the oxidation resistant copper particles includes the steps of dissolving a copper salt and a salt of at least one of the metals in a suitable solvent or diluent; forming primary particles of copper and at least one metal in basic form by mixing a base and the salt solution; separating, washing and drying the primary particles; reducing the primary particles to metallic form; and heat treating the particles in metallic form at an elevated temperature.

Edelstein, Alan S.; Kaatz, Forrest H.; Harris, Vincent G.

1993-11-01

348

Proton (3 MeV) and copper (120 MeV) ion irradiation effects in low-density polyethylene (LDPE)  

Microsoft Academic Search

Low-density polyethylene (LDPE) was irradiated with proton (3MeV) and copper (120MeV) ions to analyze the induced modifications with respect to optical and structural properties. In the present investigation, the fluence for proton irradiation was varied up to 2×1015protonscm?2, while that for copper beam was kept in the range of 1×101 to 1×1013ionscm?2 to study the swift heavy ion-induced modifications in

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

2008-01-01

349

Use of synthetic zeolites for arsenate removal from pollutant water.  

PubMed

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 at room temperature. Experiments have been conducted to examine the extent of arsenic removal as a function of pH. The effect of initial arsenic concentration and liquid to solid ratio in the batch reactions has also been studied. Zeolite NH4+/Y (NY6) showed significant arsenate removal capacity over a wide initial pH range of 2-12. Zeolite NY6 achieved this performance by buffering the initial pH to within a range of 3.5 < pH < 7 where uptake of arsenate onto aluminol surface groups is at a maximum. The high aluminum content of NY6 (i.e. low Si/Al ratio) was an important factor governing the improved performance of this zeolite relative to other tested zeolites with higher Si/Al ratio. The pH buffering capacity of NY6 could lead to savings in cost and process time for industrial effluent treatment due to avoidance of a pH pre-conditioning step prior to arsenate removal. PMID:15276735

Shevade, Siddhesh; Ford, Robert G

350

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

351

Ion exchangers in radioactive waste management: natural Iranian zeolites.  

PubMed

Five samples of natural zeolites from different parts of Iran were chosen for this study. In order to characterize and determine their structures, X-ray diffraction and infrared spectrometry were carried out for each sample. The selective absorption properties of each zeolite were found by calculating the distribution coefficient (K(d)) of various simulated wastes which were prepared by spiking the radionuclides with (131)I, (99)Mo, (153)Sm, (140)La and (147)Nd. All the zeolite samples used in this study had extremely high absorption value towards (140)La; clinoptolite from Mianeh and analsite from Ghalehkhargoshi showed good absorption for (147)Nd; clinoptolite from Semnan and clinoptolite from Firozkoh showed high absorption for (153)Sm; mesolite from Arababad Tabas showed good absorption for (99)Mo; and finally mesolite from Arababad Tabas, clinoptolite from Semnan and clinoptolite from Firozkoh could be used to selectively absorb (131)I from the stimulated waste which was prepared. The natural zeolites chosen for these studies show a similar pattern to those synthetic ion exchangers in the literature and in some cases an extremely high selectivity towards certain radioactive elements. Hence the binary separation of radioactive elements could easily be carried out. Furthermore, these zeolites, which are naturally occurring ion exchangers, are viable economically and extremely useful alternatives in this industry. PMID:16099667

Nilchi, A; Maalek, B; Khanchi, A; Ghanadi Maragheh, M; Bagheri, A; Savoji, K

2005-08-15

352

Novel Modifications in RNA  

PubMed Central

The last several years have seen numerous reports of new chemical modifications for use in RNA. In addition, in that time period, we have seen the discovery of several previously unknown naturally occurring modifications that impart novel properties on the parent RNAs. In this review, we describe recent discoveries in these areas with a focus on RNA modifications that introduce spectroscopic tags, reactive handles, or new recognition properties.

Phelps, Kelly; Morris, Alexi; Beal, Peter A.

2012-01-01

353

Techniques of copper recovery from Mexican copper oxide ore  

Microsoft Academic Search

Mexican copper ore is a mixed ore containing mainly copper oxide and some copper sulfide that responds well to flotation. The joint techniques of flotation and leaching were studied. The results indicate that an ore containing 19.01% copper could be obtained at a recovery ratio of 35.02% by using sodium sulfide and butyl xanthate flotation. Over 83.33% of the copper

Zhan-fang CAO; Hong ZHONG; Guang-yi LIU; Shu-juan ZHAO

2009-01-01

354

Copper sensitivity of Gonyaulax tamarensis  

Microsoft Academic Search

The copper sensitivity of the dinoflagellate Gonyaulax tamarensis was examined in artificial seawater medium. Two short term responses of the organism to copper toxicity are rapid loss of motility and reduced photosynthetic carbon fixation. The chelators tris(hydroxymethylamino)methane (Tris) and ethylenedinitrilotetraacetic acid (EDTA) were used to demonstrate that copper toxicity is a unique function of cupric ion activity. Copper additions to

D. M. Anderson; F. M. M. Morel

1978-01-01

355

Copper accumulation by cultured astrocytes.  

PubMed

To study copper transport in brain astrocytes, we have used astrocyte-rich primary cultures as model system. Cells in these cultures contained a basal copper content of 1.1+/-0.4 nmol per mg protein. The cellular copper content increased strongly after application of copper chloride in a time and concentration-dependent manner. Analysis of the linear copper accumulation during the first 5 min of copper exposure revealed that cultured astrocytes accumulated copper with saturable kinetics with apparent K(M)- and V(max)-values of 9.4+/-1.8 microM and 0.76+/-0.13 nmol/(min x mg protein), respectively. In contrast, incubation of astrocytes with copper in the presence of ascorbate caused a linear increase of the copper accumulation rates for copper concentrations of up to 30 microM. In addition, copper accumulation was strongly inhibited by the presence of an excess of zinc or of various other divalent metal ions. The presence of mRNA and of immunoreactivity of the copper transport protein Ctr1 in astrocyte cultures suggests that Ctr1 contributes to the observed copper accumulation. However, since some characteristics of the observed copper accumulation are not consistent with Ctr1-mediated copper transport, additional Ctr1-independent mechanism(s) are likely to be involved in astrocytic copper accumulation. PMID:20004225

Scheiber, Ivo F; Mercer, Julian F B; Dringen, Ralf

2009-12-11

356

Vibration frequencies of NCO species as an intermediate for selective reduction of nitrogen monoxide over copper ion-exchanged ZSM-5  

Microsoft Academic Search

Vibration frequencies of the NCO stretching mode were calculated for model molecules of the copper ion-exchanged ZSM-5 catalytic system, Cu(OH2)3Xn+ (X = NCO, NCO? and HNCO, n = 1 or 2) by use of ab initio molecular orbital calculations. The complexes, Al(OH)3(NCO), Al(OH)3(NCO?) and Al(OH)3(OCNH) were adopted as the models of the zeolite framework. According to the present calculations, the

Hideyuki Oka; Tadashi Okada; Kenzi Hori

1996-01-01

357

Formation and characterization of inorganic membranes from zeolite-silica microcomposites  

SciTech Connect

Small crystals of zeolites (500-1000 nm) with two- and three-dimensional channel systems (faujasite and ZSM-5 structures) were embedded in amorphous thin films derived from TEOS hydrolyzed in alcoholic solution. Scanning electron microscopy studies show that the zeolites can be quite evenly dispersed in the membrane, resulting in single layers of zeolite crystals protruding out of the amorphous matrix. In situ FT-IR studies with a series of probe molecules revealed that in most membranes the zeolites were 100% accessible from the gas phase. The membranes excluded molecules which are larger than the pore openings of the zeolite embedded in the composite.

Bein, T.; Brown, K.; Enzel, P.; Brinker, C.J.

1988-01-01

358

COPPER CABLE RECYCLING TECHNOLOGY  

SciTech Connect

The United States Department of Energy (DOE) continually seeks safer and more cost-effective technologies for use in deactivation and decommissioning (D&D) of nuclear facilities. The Deactivation and Decommissioning Focus Area (DDFA) of the DOE's Office of Science and Technology (OST) sponsors large-scale demonstration and deployment projects (LSDDPs). At these LSDDPs, developers and vendors of improved or innovative technologies showcase products that are potentially beneficial to the DOE's projects and to others in the D&D community. Benefits sought include decreased health and safety risks to personnel and the environment, increased productivity, and decreased costs of operation. The Idaho National Engineering and Environmental Laboratory (INEEL) generated a list of statements defining specific needs and problems where improved technology could be incorporated into ongoing D&D tasks. One such need is to reduce the volume of waste copper wire and cable generated by D&D. Deactivation and decommissioning activities of nuclear facilities generates hundreds of tons of contaminated copper cable, which are sent to radioactive waste disposal sites. The Copper Cable Recycling Technology separates the clean copper from contaminated insulation and dust materials in these cables. The recovered copper can then be reclaimed and, more importantly, landfill disposal volumes can be reduced. The existing baseline technology for disposing radioactively contaminated cables is to package the cables in wooden storage boxes and dispose of the cables in radioactive waste disposal sites. The Copper Cable Recycling Technology is applicable to facility decommissioning projects at many Department of Energy (DOE) nuclear facilities and commercial nuclear power plants undergoing decommissioning activities. The INEEL Copper Cable Recycling Technology Demonstration investigated the effectiveness and efficiency to recycle 13.5 tons of copper cable. To determine the effectiveness of separating out radioactive contamination, the copper cable was coated with a surrogate contaminant. The demonstration took place at the Bonneville County Technology Center in Idaho Falls, Idaho.

Chelsea Hubbard

2001-05-01

359

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

360

Solid State NMR Investigations of Zeolite - Intercalate Structures  

SciTech Connect

We will describe two topics in which structural information on complexes of zeolites is obtained from solid state NMR. In the first, recent work on the determination of the complete three-dimensional structures of the complexes of zeolites with organic sorbates will be briefly reported. The method has been optimized and the presentation of the results systematized. In the second topic, we will describe how solid state NMR can be used in the reverse sense to probe for the existence and structures of “nanocrystals” whose dimensions are too small to give proper Bragg scattering and which have been proposed to be the synthesis route for the formation of zeolite ZSM-5. In this study, the spectral parameters of “probe” template molecules are used as being diagnostic of whether the local environment of the framework has been formed. These are independent of the “crystal” dimensions and this general approach may be applicable to other similar “nano” systems.

Fyfe, Colin A.; Diaz, Anix; Brouwer, Darren H.; Lee, Joseph; Schneider, Celine M.; Scheffler, Franziska A.; Darton, Richard J.

2006-07-24

361

In situ atomic force microscopy of zeolite A dissolution.  

PubMed

In the present study, the {100} surface of zeolite A was exposed to a range of solutions and the response was monitored in real-time by means of atomic force microscopy (AFM). The zeolite dissolves by a well-defined layer process that is characterised by uncorrelated dissolution of units that are structurally unconnected and terrace retreat when building units are inter-connected. This process was observed to be coupled with the formation of nano-squares that are stabilized at the zeolite surface for a period before complete dissolution. Theoretical work suggests that three terminating structures are central to understanding the dissolution mechanism. Stripping the surface of the secondary building unit, the single 4-ring, is predicted to be a rate-determining step in dissolution, but this process occurs by removing monomeric rather than oligomeric units. PMID:18701954

Itzel Meza, L; Anderson, Michael W; Slater, Ben; Agger, Jonathan R

2008-06-27

362

Production of tertiary alkyl ether using improved zeolite catalyst  

SciTech Connect

A process is described for reducing the formation of olefinic oligomer by-products and improving tertiary ether selectivity in the production of high octane alkyl tertiary alkyl ether employing acid zeolite beta catalyst particles having alpha value greater than 300, comprising: steaming or hydrothermally treating said zeolite catalyst particles at elevated temperature to provide treated acid zeolite beta catalyst particles having a reduced alpha value of less than 300; and contacting alkanol and a hydrocarbon feed stream rich in iso-olefins with said steamed or hydrothermally treated catalyst particles under iso-olefin etherification conditions sufficient to provide at least 70 weight percent conversion of said iso-olefins, whereby a product containing at least 95 weight percent of said alkyl tertiary alkyl ether is produced while the formation of olefinic oligomer-by-product is not more than 5 weight percent.

Bell, W.K.; Haag, R.O.

1993-07-06

363

Luminescence of ordered silver iodide nanoclusters inside zeolite host  

NASA Astrophysics Data System (ADS)

Ordered silver iodide nanoclusters inside zeolite Y host were prepared by using a thermal diffusion method. The Y-AgI samples were characterized with powder X-ray diffraction, differential thermal analysis, X-ray photoelectron spectroscopy, adsorption technique and chemical analysis. The results show that silver iodide nanoclusters were situated in the ordered cages of the zeolite Y host. The results on the luminescence of the nanocomposites Y-AgI suggest that when the sizes of silver iodide nanoclusters are were very small, non-radiation surface recombination exceeds radiation process and the luminescence efficiency increases as the size of the silver iodide nanoclusters increaseds As the sizes of AgI nanoclusters increased, non-radiative surface recombination effect become equal to the radiation effect of the excitons. As the size of the nanoclusters of AgI in zeolite host further increases, the surface recombination of the nanoclusters becomes a major process.

Zhai, Qing-Zhou; Hu, Wei-Hua; Guan, Xin; Jiang, Tian-Su; Qiu, Shilun; Zou, Ming-Qiang

2002-11-01

364

NO trapping in biological systems with a functionalized zeolite network.  

PubMed

Zeolite-Y powder has been functionalized with ferric iron-diethyldithiocarbamate complexes and applied to trap nitric oxide radicals in liquids and biological systems. The complexes have been assembled in situ in the pores of zeolite-Y and act as traps for nitric oxide radicals. The resulting mononitrosyl-iron complexes form a mixture of diamagnetic ferric and paramagnetic ferrous complexes. The yield of trapped NO may be determined ex situ using electron paramagnetic resonance. The material may be anchored on solid surfaces, mixed into a composite or compressed into small pellets. The material was used to detect endogenous NO in endothelial cell cultures and spinach leaves. The sensitivity of the functionalized zeolite is significantly better than that achieved in conventional trapping of NO with iron-diethyldithiocarbamate complexes. PMID:16458549

van Faassen, E; Vanin, A

2006-02-03

365

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

366

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

2012-12-19

367

Formulation of cracking catalyst based on zeolite and natural clays  

SciTech Connect

Domestically manufactured cracking catalysts are based on a synthetic amorphous aluminosilicate matrix and Y zeolite. A multistage {open_quotes}gel{close_quotes} technology is used in manufacturing the catalysts. The process includes mixing solutions of sodium silicate and acidic aluminum sulfate, forming, syneresis, and activation of the beaded gel. In the manufacture of bead catalysts, the next steps in the process are washing, drying, and calcining; in the manufacture of microbead catalysts, the next steps are dispersion and formation of a hydrogel slurry, spray-drying, and calcining. The Y zeolite is either introduced into the alumina-silica sol in the stage of forming the beads, or introduced in the dispersion stage. With the aim of developing an active and selective cracking catalyst based on Y zeolite and natural clays, with improved physicomechanical properties, the authors carried out a series of studies, obtaining results that are set forth in the present article.

Aliev, R.R.; Lupina, M.I.

1995-11-01

368

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

2013-09-25

369

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

370

Ring opening of methylcyclohexane over platinum-loaded zeolites.  

PubMed

The activity of different platinum-loaded zeolites (Mordenite, ZSM-12, ZSM-5, ZSM-23) was investigated in the hydroconversion of methylcyclohexane (MCH), in the context of upgrading highly aromatic distillates for fuel blending. In all cases, conversion of MCH proceeds according to a pathway where the primary products are a mixture of dimethylcyclopentanes and ethylcyclopentane formed by isomerization and ring contraction of MCH. The primary products undergo consecutive ring-opening reactions with formation of n- and isoheptanes. The latter further react to form lower-molecular-weight n- and isoalkanes. The selectivity and distribution of products deriving from ring-contraction and ring-opening reactions are strongly affected by the pore size and topology of the zeolites. ZSM-5 exhibits a strong reactant shape-selectivity effect on ring-opening products. The evaluated zeolites show the following order of activity in the conversion of methylcyclohexane: Mordenite>ZSM-12>ZSM-5>ZSM-23. PMID:18702154

Calemma, Vincenzo; Carati, Angela; Flego, Cristina; Giardino, Roberto; Gagliardi, Federica; Millini, Roberto; Bellussi, Giuseppe

2008-01-01

371

Highly selective zeolite membranes as explosive preconcentrators.  

PubMed

Highly selective thin zeolite MFI membranes are synthesized on porous stainless steel and ?-alumina supports using a seeded growth method. An ultraviolet (UV) light treatment is employed as a low temperature alternative to remove the organic structure-directing agent (SDA) to avoid membrane cracking. The feasibility of the use of the MFI membranes as an explosive preconcentrator is examined by measuring the permeation of nitrogen (N(2), an air surrogate) and 1,3,5-trimethylbenzene (TMB) (a 2,4,6-trinitrotoluene (TNT) surrogate) in a mixture of N(2) and TMB. High N(2)/TMB selectivity (>10,000) and reasonable N(2) flux (13.5 mmol/m(2)·s) are observed. On the basis of the flux, a hollow fiber array based preconcentrator is proposed and estimated to provide 1000× concentration within about 1 min using a hollow fiber with a 50 ?m internal radius. This high performance explosive preconcentrator may open a new venue for the detection of subppb or lower level of explosives simply in conjunction with conventional explosives detectors. PMID:22830561

Zhao, Jie; Luo, Ting; Zhang, Xiangwen; Lei, Yu; Gong, Ke; Yan, Yushan

2012-07-19

372

Proton-loaded zeolites. 1. HX (X = Cl, Br, I) in sodium zeolite Y archetype: Packaged acids on the rod to intrazeolite semiconductors  

Microsoft Academic Search

This series of three papers is concerned with an in-depth investigation of proton-loaded zeolites (packaged acids), a novel class of controlled microporosity, solid-state Broensted acids. Proton-loaded zeolites are formed from the reaction between anhydrous Broensted acids and dehydrated zeolites. Initial experiments focus attention on the chemistry, spectroscopy, diffraction, and dynamics of the sorption and desorption of anhydrous hydrogen halides (HX)

G. A. Ozin; S. Oezkar; G. D. Stucky

1990-01-01

373

Effects of TS1 zeolite structures on physical properties and enzymatic degradation of Poly (butylene succinate) (PBS)\\/TS1 zeolite hybrid composites  

Microsoft Academic Search

The objective of this study was to investigate how the water uptake features and carrier characteristics of the TS-1 zeolite affected the physical and rheological properties, morphological parameters, and enzymatic hydrolysis of Poly (butylene succinate) (PBS). The introduction of TS-1 zeolite as catalyst was developed for the preparation of PBS\\/TS-1 zeolite hybrid composites (PTHC) without heavy metal toxic substance in

Sung Yeon Hwang; Eui Sang Yoo; Seung Soon Im

2011-01-01

374

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

375

Bicontinuous zeolite polymer composite membranes prepared via float casting.  

PubMed

We prepared bicontinuous composite membranes comprising zeolite A particles. The particles form a monolayer which is embedded in a polymer sheet in such a way that each particle penetrates both surfaces of the polymer sheet. Preparation was done via "float casting"; a mixture of hydrophobized zeolite particles and an appropriate volume of a nonvolatile polymerizable organic liquid monomer was applied onto a water surface. The monomer was solidified via photopolymerization to form the above-mentioned membrane. In as-prepared state (without extensive drying), this membrane is permeable for water vapor (in case of zeolite 4A permeance = 8 × 10(-9) mol m(-2) s(-1) Pa(-1), permeability = 1.65 × 10(-14) mol m(-1) s(-1) Pa(-1) = 49 barrer) but impermeable for nitrogen (permeance below detection limit of 5 × 10(-12) mol m(-2) s(-1) Pa(-1), permeability below detection limit of 1 × 10(-17) mol m(-1) s(-1) Pa(-1) = 0.03 barrer). The permeance for water vapor increases with increasing pore size of the zeolite (in case of zeolite 5A, all other parameters being unchanged, permeance = 12 × 10(-9) mol m(-2) s(-1) Pa(-1), permeability = 2.4 × 10(-14) mol m(-1) s(-1) Pa(-1) = 72 barrer). These observations indicate that the water molecules are predominantly transported through the zeolite channels and at the same time block the passage of other molecules. The impermeability for nitrogen in as-prepared state indicates a low amount of defects that are not blocked by water. Furthermore, the composite nature of the membrane gives rise to a reduced brittleness; membranes can be handled manually without support structure and thus might be promising candidates for separation technology. PMID:23398555

Kiesow, Ina; Marczewski, Dawid; Reinhardt, Lutz; Mühlmann, Marcel; Possiwan, Mario; Goedel, Werner A

2013-03-07

376

The origin of strong acidity in dealuminated zeolite-Y  

SciTech Connect

The commercial utilization of dealuminated Y-type zeolites has generated renewed interest in the origin of strong acidity in these materials. It is now evident that a carefully prepared H-Y zeolite, with its full complement of protons but with no extraframework Al, exhibits very little activity for acid-catalyzed reactions such as the dealkylation of cumene or the cracking of hexane. If these zeolites are dealuminated to ca. 32 framework Al concentration corresponds to a Si/Al ratio of 5.0 or a unit cell dimension, a{sub 0}, of 24.54 {angstrom}. Even if zeolites are not purposely dealuminated at the outset, they become dealuminated to an equilibrium level during their regeneration in a catalytic cracking unit. Early theoretical arguments of Dempsey and also of Mikovsky and Marshall suggested that the acid strength was related to the Al distribution in the framework and that only Al{sub f} atoms with no second-neighbor Al{sub f} atoms in the 4-rings are responsible for strong Broensted acidity. The number of aluminum atoms with 0, 1, 2, and 3 aluminum second neighbors in the 4-rings has been calculated by Beagley et al. The dealumination process, whether by steaming or by treatment with SiCl{sub 4}, not only changes the Al{sub f} distribution but also introduces extraframework Al into the zeolite cavities. It is the purpose of this review to summarize these results and to suggest a model of strong acidity that appears to fit much of the available data. The data include catalytic results on faujasite-type zeolites prepared by several methods, poisoning studies, and infrared studies of hydroxyl groups.

Lunsford, J.H. (Texas A and M Univ., College Station, TX (United States))

1990-08-01

377

Permit application modifications  

SciTech Connect

This document contains the Permit Application Modifications for the Y-12 Industrial Landfill V site on the Oak Ridge Reservation. These modifications include the assessment of stability of the proposed Landfill V under static and loading conditions. Analyses performed include the general slope stability, veneer stability of the bottom liner and cover system, and a liquefaction potential assessment of the foundation soils.

NONE

1995-11-01

378

Thermodynamics of nitrogen adsorption on the zeolite H-FER  

NASA Astrophysics Data System (ADS)

Adsorption (at a low temperature) of nitrogen on the protonic zeolite H-FER results in hydrogen bonding of the adsorbed N2 molecules with the zeolite Si(OH)Al Brønsted acid groups. This hydrogen bonding interaction leads to activation, in the IR, of the fundamental NN stretching mode, which appears at 2331 cm-1. From the infrared spectra taken over a temperature range, while simultaneously recording integrated IR absorbance, temperature and nitrogen equilibrium pressure, the thermodynamics of the adsorption process was studied. The standard adsorption enthalpy and entropy resulted to be ?H° = -20(±1) kJ mol-1 and ?S° = -131(±10) J mol-1 K-1, respectively.

Rodríguez Delgado, M.; Otero Areán, C.

2007-04-01

379

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

380

Synthesis of heterocyclic compounds using basic zeolite Cs?  

Microsoft Academic Search

The application of the basic zeolite Cs? as catalyst for the interaction of methyl vinyl ketone (MVK) with 5-methoxybenzimidazole-2-thiol\\u000a leads to a Michael heteroreaction exclusively at the N-nucleophilic center with the formation of a fairly unusual product\\u000a of di-addition of MVK to thiol. The reaction of 1,2,4-triazole-3-thiol with MVK in the presence of zeolite Cs? proceeds both\\u000a at the S-

E. V. Suslov; D. V. Korchagina; K. P. Volcho; N. F. Salakhutdinov

2009-01-01

381

Canine models of copper toxicosis for understanding mammalian copper metabolism.  

PubMed

Hereditary forms of copper toxicosis exist in man and dogs. In man, Wilson's disease is the best studied disorder of copper overload, resulting from mutations in the gene coding for the copper transporter ATP7B. Forms of copper toxicosis for which no causal gene is known yet are recognized as well, often in young children. Although advances have been made in unraveling the genetic background of disorders of copper metabolism in man, many questions regarding disease mechanisms and copper homeostasis remain unanswered. Genetic studies in the Bedlington terrier, a dog breed affected with copper toxicosis, identified COMMD1, a gene that was previously unknown to be involved in copper metabolism. Besides the Bedlington terrier, a number of other dog breeds suffer from hereditary copper toxicosis and show similar phenotypes to humans with copper storage disorders. Unlike the heterogeneity of most human populations, the genetic structure within a purebred dog population is homogeneous, which is advantageous for unraveling the molecular genetics of complex diseases. This article reviews the work that has been done on the Bedlington terrier, summarizes what was learned from studies into COMMD1 function, describes hereditary copper toxicosis phenotypes in other dog breeds, and discusses the opportunities for genome-wide association studies on copper toxicosis in the dog to contribute to the understanding of mammalian copper metabolism and copper metabolism disorders in man. PMID:22147205

Fieten, Hille; Leegwater, Peter A J; Watson, Adrian L; Rothuizen, Jan

2011-12-07

382

Copper Containing Ballistic Additives.  

National Technical Information Service (NTIS)

In accordance with this invention, it has been found that the addition of certain copper compounds to solid propellant composition can materially increase the burning rate of the propellant grains while simultaneously reducing the pressure exponent in the...

R. C. Corley

1981-01-01

383

Electrodeposition of Copper.  

National Technical Information Service (NTIS)

The patent application consists of a method for electrowinning or electrorefining of metals, particularly copper, comprising electro-depositing the metal from an electrolyte solution under conditions comprising high cathode and anode current densities and...

Schlain McCawley Smith

1976-01-01

384

Stabilized Electroless Copper Solution.  

National Technical Information Service (NTIS)

The electroless copper plating solution contains Fehling's solution, a reducing agent such as formaldehyde and a stabilizing amount of 2-mercapto-benzothiazole. The solution is more stable than prior solutions.

F. Pearlstein

1965-01-01

385

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

386

Entrainment behavior of copper and copper matte in copper smelting operations  

Microsoft Academic Search

In copper smelting, the loss of copper to the slag due to entrainment is largely influenced by the flotation of copper metal\\u000a and\\/or matte in the slag phase. To evaluate this behavior, the surface tension of copper as a function of temperature and\\u000a oxygen pressure and the interfacial tension of the copper-iron matte-slag system as a function of matte grade

S. W. Ip; J. M. Toguri

1992-01-01

387

Copper tolerance and copper accumulation of herbaceous plants colonizing inactive California copper mines  

SciTech Connect

Herbaceous plant species colonizing four copper mine waste sites in northern California were investigated for copper tolerance and copper accumulation. Copper tolerance was found in plant species colonizing soils with high concentrations of soil copper. Seven of the eight plant species tested were found at more than one copper mine. The mines are geographically isolated, which makes dispersal of seeds from one mine to another unlikely. Tolerance has probably evolved independently at each site. The nontolerant field control population of Vulpia microstachya displays significantly higher tolerance to copper at all copper concentration levels tested than the nontolerant Vulpia myrous population, and the degree of copper tolerance attained by V. microstachya at the two copper mines was much greater than that found in V. myrous. It suggests that even in these two closely related species, the innate tolerance in their nontolerant populations may reflect their potential for evolution of copper tolerance and their ability to initially colonize copper mine waste sites. The shoot tissue of the copper mine plants of Arenaria douglasii, Bromous mollis, and V. microstachya accumulated less copper than those plants of the same species from the field control sites when the two were grown in identical conditions in nutrient solution containing copper. The root tissue of these mine plants contain more copper than the roots of the nonmine plants. This result suggests that exclusion of copper from the shoots, in part by immobilization in the roots, may be a feature of copper tolerance. No difference in the tissue copper concentration was detected between tolerant and nontolerant plants of Lotus purshianus, Lupinus bicolor, and Trifolium pratense even though the root tissue had more copper than the leaves.

Kruckeberg, A.L.; Wu, L. (Department of Environmental Horticulture, University of California, Davis (United States))

1992-06-01

388

Copper deficiency myelopathy  

Microsoft Academic Search

Acquired copper deficiency has been recognised as a rare cause of anaemia and neutropenia for over half a century. Copper\\u000a deficiency myelopathy (CDM) was only described within the last decade, and represents a treatable cause of non-compressive\\u000a myelopathy which closely mimics subacute combined degeneration due to vitamin B12 deficiency. Here, 55 case reports from the\\u000a literature are reviewed regarding their

Stephan R. JaiserGavin; Gavin P. Winston

2010-01-01

389

Copper and Copper Alloy Powders. Seminar Held on 18th December 1976.  

National Technical Information Service (NTIS)

This report contains the following papers: Types, Properties and Uses of Copper Powder; Production of Copper & Copper Alloy Powders for General Engineering Applications; Bronze Powders; Atomized Copper and Copper Based Powders; Process and Equipment for t...

1976-01-01

390

Localization of copper and copper transporters in the human brain.  

PubMed

Disturbances in brain copper result in rare and severe neurological disorders and may play a role in the pathogenesis and progression of multiple neurodegenerative diseases. Our current understanding of mammalian brain copper transport is based on model systems outside the central nervous system and no data are available regarding copper transport systems in the human brain. To address this deficit, we quantified regional copper concentrations and examined the distribution and cellular localization of the copper transport proteins Copper transporter 1, Atox1, ATP7A, and ATP7B in multiple regions of the human brain using inductively coupled plasma-mass spectrometry, Western blot and immunohistochemistry. We identified significant relationships between copper transporter levels and brain copper concentrations, supporting a role for these proteins in copper transport in the human brain. Interestingly, the substantia nigra contained twice as much copper than that in other brain regions, suggesting an important role for copper in this brain region. Furthermore, ATP7A levels were significantly greater in the cerebellum, compared with other brain regions, supporting an important role for ATP7A in cerebellar neuronal health. This study provides novel data regarding copper regulation in the human brain, critical to understand the mechanisms by which brain copper levels can be altered, leading to neurological disease. PMID:23076575

Davies, Katherine M; Hare, Dominic J; Cottam, Veronica; Chen, Nicholas; Hilgers, Leon; Halliday, Glenda; Mercer, Julian F B; Double, Kay L

2013-01-01

391

Copper deficiency in celiac disease.  

PubMed

Copper deficiency is an uncommonly reported complication of celiac disease that has not received much attention in recent years. Copper deficiency may result in anemia and thrombocytopenia and also irreversible myeloneuropathy if it is not detected and treated appropriately. The prevalence of copper deficiency in patients with celiac disease is unknown. We describe 5 patients with celiac disease and associated copper deficiency diagnosed at our institution in recent years. All 5 patients had neurologic complications of copper deficiency and 3 patients also presented with hematologic abnormalities. We also review the literature regarding copper deficiency in celiac disease. PMID:18496230

Halfdanarson, Thorvardur R; Kumar, Neeraj; Hogan, William J; Murray, Joseph A

2009-02-01

392

Electrowinning of Copper from Chloride Solutions.  

National Technical Information Service (NTIS)

Electrowinning of copper from chloride solutions was studied in a diaphragm cell. The copper powder product was shaken periodically from the cathode and removed from the bottom of the cell. The effects of copper concentration, brine concentration, copper ...

R. E. Mussler R. S. Olsen T. T. Campbell

1975-01-01

393

Hydrophobic Fe-Zeolites for Removal of MTBE from Water by Combination of Adsorption and Oxidation.  

PubMed

Several zeolites were evaluated as adsorbents for the removal of MTBE from water in a screening process. It was observed that the SiO(2)/Al(2)O(3) molar ratio is a decisive factor for the adsorption properties, at least in the case of ZSM5 zeolites. ZSM5 zeolites with SiO(2)/Al(2)O(3) ratios >200 were found to provide the best sorption properties for MTBE. To design a combined sorption/reaction method, regeneration of the loaded zeolites by selected advanced oxidation processes (AOP) was studied: (1) Fenton treatment using H(2)O(2) with dissolved iron salts and (2) heterogeneous Fenton-like oxidation with Fe immobilized on the zeolites. The first was ineffective in regenerating loaded zeolites. However, heterogeneous catalysis using Fe species immobilized on the zeolite by liquid ion exchange was markedly more effective. Although these hydrophobic zeolites have a low ion exchange capacity, resulting in iron loadings of ?0.09 wt %, it was possible to obtain sufficiently active catalysts. Hydrophobic Fe-zeolites can therefore be regarded as promising materials for the removal of MTBE from water, since they allow the combination of efficient adsorption and oxidative degradation of MTBE by H(2)O(2). In contrast to the homogeneous catalysis by dissolved iron ions, these heterogeneous catalysts work at near-neutral pH and can be easily reused. Fe-zeolites as adsorbents/catalysts showed a good stability in both batch and column experiments. PMID:23346998

Gonzalez-Olmos, Rafael; Kopinke, Frank-Dieter; Mackenzie, Katrin; Georgi, Anett

2013-02-14

394

Low acidity alumina-bound zeolites containing tetrahedral boron, gallium, indium and/or thallium  

SciTech Connect

This patent describes a method of preparing a composition comprising a zeolite and a matrix comprising alumina wherein the composition exhibits an alpha value of the zeolite, wherein the zeolite has a SiO/sub 2//Al/sub 2/O/sub 3/ molar ratio of at least about 10, ahs an alpha value of less than about 100 and contains a framework tetrahedral element selected from the group consisting of B, Ga, In and Tl, wherein the method comprises: (a) providing the zeolite containing an alkylammonium salt; (b) ion exchanging the zeolite to replace alkali metal cations with ammonium cations; (c) binding the zeolite with an aluminum containing material; and (d) calcining the zeolite containing aluminum material to decompose organic material and convert the zeolite to the acid or hydrogen form, and thereby producing the composition having the alpha value which is the alpha value of the zeolite in the acid or hydrogen form, absent the matrix. The method of claim 1, wherein the zeolite containing aluminum material is dried to eliminate excess water, prior to calcining.

Degman, T.F. Jr.; Lutner, J.D.; Chen, N.Y.

1988-11-29

395

The conversion of methanol and other O-compounds to hydrocarbons over zeolite [beta  

SciTech Connect

The conversion of alcohols, ethers, and carbonyl compounds using zeolite [beta], zeolite ZSM-5, and zeolite Y are compared and contrasted. The proton form of zeolite [beta] is found to be as active as H-ZSM-5 for this reaction, whereas zeolite Y is much less active. Zeolite [beta] gives isobutane as the major product from methanol conversion under all reaction conditions tested, together with significant selectivities to C[sub 2] and C[sub 3] hydrocarbons. The conversions of ethanol and propanol over zeolite [beta] lead to the almost exclusive formation of the corresponding alkene via water elimination. This is in contrast to ZSM-5, and hence zeolite [beta] does not exhibit the rapid secondary conversion reactions typified by ZSM-5 for alcohol conversion reactions. The high selectivity to iso-C[sub 4] hydrocarbons is also found for zeolite [beta] for the conversion of acetone and acetic acid. The results are discussed in terms of the possible mechanisms for the formation of iso-C[sub 4] hydrocarbons in high selectivity for zeolite [beta]. 28 refs., 7 figs., 5 tabs.

Hutchings, G.J.; Johnston, P.; Lee, D.F.; Warwick, A.; Williams, C.D.; Wilkinson, M. (Univ. of Liverpool (United Kingdom))

1994-05-01

396

Effect of Yucca schidigera and Natural Zeolite on Broiler Performance  

Microsoft Academic Search

The effects of dietary supplementation of Yucca schidigera and natural zeolite on broile r performance, ammonia concentration of broiler house, litter moisture, fecal dry matter and fecal crude ash were investigated. One day-old, nine hundred and sixty unsexed broiler chicks obtained from a commercial hatchery were divided into 4 treatment groups of 240 birds each. Birds were randomly assigned to

2004-01-01

397

Ammonium removal from wastewaters using natural New Zealand zeolites  

Microsoft Academic Search

Ammoniacal nitrogen (ammonia and ammonium) in agricultural wastewaters can promote eutrophication of receiving waters and be potentially toxic to fish and other aquatic life. Zeolites, which are hydrated aluminum?silicate minerals, have an affinity for ammonium ions (NH4 ) and are, therefore, potentially useful in removing this contaminant from wastewaters. The major objectives of this study were to evaluate the capacity

M. L. Nguyen; C. C. Tanner

1998-01-01

398

Use of synthetic zeolites for arsenate removal from pollutant water  

Microsoft Academic Search

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 at room temperature. Experiments have been conducted to examine the extent of arsenic

Siddhesh Shevade; Robert G. Ford

2004-01-01

399

Synthesis and Properties of Nano Zeolitic Imidazolate Frameworks  

SciTech Connect

Nano sized zeolitic imidazolate frameworks [nZIF-8] with excellent chemical and thermal stability has been synthesized at room temperature by simple mixing of 2-methylimidazole and zinc nitrate hexahydrate in methanol/ 1% high molecular weight poly(diallyldimethylammonium chloride) solution for 24 hrs

Nune, Satish K.; Thallapally, Praveen K.; Dohnalkova, Alice; Wang, Chong M.; Liu, Jun; Exarhos, Gregory J.

2010-07-21

400

The role of zeolite pore structure during deactivation by coking  

SciTech Connect

Residues accumulating within the cavities of a small-pore zeolite, isolated by extraction, are composed of a series of aromatics up to a distinct cutoff at pyrene. Similar analysis of partially-regenerated catalyst reveal pathways by which residue oxidation can occur and pathways by which these residues can participate during methanol decomposition.

MaLaughlin, K.W.; Anthony, R.G.

1985-06-01

401

Synthesis of mesoporous zeolite single crystals with cheap porogens  

NASA Astrophysics Data System (ADS)

Mesoporous zeolite (silicalite-1, ZSM-5, TS-1) single crystals have been successfully synthesized by adding soluble starch or sodium carboxymethyl cellulose (CMC) to a conventional zeolite synthesis system. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption analysis, 27Al magic angle spinning nuclear magnetic resonance (27Al MAS NMR), temperature-programmed desorption of ammonia (NH3-TPD) and ultraviolet-visible spectroscopy (UV-vis). The SEM images clearly show that all zeolite crystals possess the similar morphology with particle size of about 300 nm, the TEM images reveal that irregular intracrystal pores are randomly distributed in the whole crystal. 27Al MAS NMR spectra indicate that nearly all of the Al atoms are in tetrahedral co-ordination in ZSM-5, UV-vis spectra confirm that nearly all of titanium atoms are incorporated into the framework of TS-1. The catalytic activity of meso-ZSM-5 in acetalization of cyclohexanone and meso-TS-1 in hydroxylation of phenol was also studied. The synthesis method reported in this paper is cost-effective and environmental friendly, can be easily expended to prepare other hierarchical structured zeolites.

Tao, Haixiang; Li, Changlin; Ren, Jiawen; Wang, Yanqin; Lu, Guanzhong

2011-07-01

402

Multitechnique Analysis of the Lattice Structures of Highly Siliceous Zeolites  

Microsoft Academic Search

The combined use of high-resolution solid state NMR techniques (both 1D and 2D) with synchrotron-based powder x-ray diffraction studies yields detailed information on the lattice structures of highly siliceous zeolites. The two methods are complementary, the former probing short range ordering and structures while the latter is sensitive to long range orderings and periodicities.

C. A. Fyfe; H. Gies; G. T. Kokotailo; Y. Feng; H. Strobl; B. Marler; D. E. Cox

1999-01-01

403

Mobil/Badger to market zeolite-based cumene technology  

SciTech Connect

Badger (Cambridge, MA) and Mobil (Fairfax, VA) are ready to jointly license a new cumene technology that they say achieves higher yields and product purity than existing processes. The zeolite-based technology is scheduled to be introduced at next month's DeWitt Petrochemical Review in Houston. The Mobil/Badger technology aims to challenge the dominant position of UOP's (Des Plaines, IL) solid phosphoric acid (SPA) catalyst process - which accounts for 80%-90% of the world's cumene production. In addition, Monsanto/Kellogg's aluminum chloride-based technology has gained significant momentum since its introduction in the 1980s. And late last year, ABB Lummus Crest (Bloomfield, NJ) also began marketing a zeolite-based cumene technology. While all the technologies make cumene via the alkylation of benzene with propylene, the Mobil/Badger process uses a zeolite-containing catalyst designed by Mobil to selectively catalyze the benzene/propylene reaction, avoiding unwanted propylene oligomerization. Because the olefin reactions are so fast, says Frank A. Demers, Badger's v.p./technology development and marketing, other zeolite technologies are forced to use complex reactor arrangements to stop the propylene-propylene reactions. However, he says, Mobil has designed a catalyst that wants to react benzene with propylene to make cumene.'

Rotman, D.

1993-02-24

404

Dehydration of alcohols on synthetic zeolite of structure Y  

Microsoft Academic Search

1.A study was made of the dehydration of the C2-C4 alcohols and cyclohexanol on zeolite CaY, with a SiO2\\/Al2O3 ratio equal to 3.4.2.The optimum temperatures at which the alcohols are completely dehydrated to the corresponding olefins were determined.

Kh. M. Minachev; V. I. Garanin; Ya. I. Isakov

1964-01-01

405

NQRS Data for Zeolite Y (Subst. No. 2533)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume B 'Substances Containing C10H16 … Zn' of Volume 48 'Nuclear Quadrupole Resonance Spectroscopy Data' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains an extract of Section '3.2 Data tables' of the Chapter '3 Nuclear quadrupole resonance data' providing the NQRS data for Zeolite Y (Subst. No. 2533)

Chihara, H.; Nakamura, N.

406

Multitechnique Analysis of the Lattice Structures of Highly Siliceous Zeolites  

SciTech Connect

The combined use of high-resolution solid state NMR techniques (both 1D and 2D) with synchrotron-based powder x-ray diffraction studies yields detailed information on the lattice structures of highly siliceous zeolites. The two methods are complementary, the former probing short range ordering and structures while the latter is sensitive to long range orderings and periodicities.

Fyfe, C. A.; Gies, H.; Kokotailo, G. T.; Feng, Y.; Strobl, H.; Marler, B.; Cox, D. E.

1999-08-26

407

Electro-Magnetorheological Fluids Dispersing Zeolite Particles Containing Iron  

Microsoft Academic Search

Some functional fluids that respond to both magnetic and electric fields have been prepared and their characteristics are described. In this study, an electro-magnetorheological fluid (EMRF) dispersing zeolite particles containing metallic iron by reducing precipitated magnetite has been investigated. When the viscosity is measured by cone plate viscometer and cylindrical viscometer, electric and magnetic fields are applied both between cone

A. Shibayama; T. Miyazaki; K. Yamaguchi; K. Murakami; T. Fujita

2002-01-01

408

Machine learning approach for structure-based zeolite classification  

Microsoft Academic Search

Application of knowledge discovery methods to crystal structure databases is an emerging research area of materials science that is playing an important role in facilitating data analysis. This study is aimed at combining computational geometry methods with machine learning algorithms for classification of inorganic solid materials of known structure. Zeolite crystals are used for the pilot study where a model

D. Andrew Carr; Mohammed Lach-hab; Shujiang Yang; Iosif I. Vaisman; Estela Blaisten-Barojas

2009-01-01

409

An ordered mesoporous aluminosilicate with completely crystalline zeolite wall structure.  

PubMed

An ordered mesoporous aluminosilicate with completely crystalline zeolite pore wall structure, denoted as OMZ-1, was successfully synthesized by recrystallization of SBA-15 using in situ formed CMK-5 as the hard template. The role of carbon material not only serves as a hard template to preserve ordered mesoporous structure but also kinetically controls the crystallization process to form large crystals. PMID:16910631

Fang, Yunming; Hu, Haoquan

2006-08-23

410

Association of Indigo with Zeolites for Improved Color Stabilization  

NASA Astrophysics Data System (ADS)

The durability of an organic colour and its resistance against external chemical agents and exposure to light can be significantly enhanced by hybridizing the natural dye with a mineral. In search for stable natural pigments, the present work focuses on the association of indigo blue with several zeolitic matrices (LTA zeolite, mordenite, MFI zeolite). The manufacturing of the hybrid pigment is tested under varying oxidising conditions, using Raman and UV-visible spectrometric techniques. Blending indigo with MFI is shown to yield the most stable composite in all of our artificial indigo pigments. In absence of defects and substituted cations such as aluminum in the framework of the MFI zeolite matrix, we show that matching the pore size with the dimensions of the guest indigo molecule is the key factor. The evidence for the high colour stability of indigo@MFI opens a new path for modeling the stability of indigo in various alumino-silicate substrates such as in the historical Maya Blue pigment.

Dejoie, Catherine; Martinetto, Pauline; Dooryhée, Eric; van Elslande, Elsa; Blanc, Sylvie; Bordat, Patrice; Brown, Ross; Porcher, Florence; Anne, Michel

2010-10-01

411

The environmental applications of activated carbon\\/zeolite composite materials  

Microsoft Academic Search

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

K. Y. Foo; B. H. Hameed

2011-01-01

412

Keggin anions promoted synthesis of zeolites and mesoporous materials  

Microsoft Academic Search

A rapid and convenient route to synthesize microporous (zeolites e.g. FAU, MFI and FER) and mesoporous (MCM-41 and MCM-48) materials employing Keggin anions as novel promoters has been reported. The catalytic use of these promoters not only reduces the syntheses time by 3 to 4 folds but also produces uniform and very small (nanosized) crystallites of the materials. Various Keggin

K. Mukhopadhyay; A. Ghosh; R. Kumar

2004-01-01

413

Confinement effects in the adsorption of simple bases by zeolites  

Microsoft Academic Search

An analysis of the heats of adsorption of ammonia and several simple amines on zeolites MOR and MFI, based on recent literature data, shows that these adsorption heats are determined by both chemical (heat of protonation) and physical (confinement) factors. Confinement effects which arise from van der Waals interactions cannot be ignored as they may represent up to 40% of

Eric G Derouane; Clarence D Chang

2000-01-01

414

High-pressure alchemy on a small-pore zeolite  

NASA Astrophysics Data System (ADS)

While an ever-expanding variety of zeolites with a wide range of framework topology is available, it is desirable to have a way to tailor the chemistry of the zeolitic nanopores for a given framework topology via controlling both the coordination-inclusion chemistry and framework distortion/relaxation. This is, however, subjected to the ability of a zeolitic nanopore to allow the redistribution of cations-water assembly and/or insertion of foreign molecules into the pores and channels. Small-pore zeolites such as natrolite (Na16Al16Si24O80x16H2O), however, have been known to show very limited capacity for any changes in the confinement chemistry. We have recently shown that various cation-exchanged natrolites can be prepared under modest conditions from natural sodium natrolite and exhibit cation-dependent volume expansions by up to 18.5% via converting the elliptical channels into progressively circular ones. Here, we show that pressure can be used as a unique and clean tool to further manipulate the chemistry of the natrolite nanopores. Our recent crystallographic and spectroscopic studies of pressure-insertion of foreign molecules, trivalent-cation exchange under pressure, and pressure-induced inversion of cation-water coordination and pore geometry in various cation-exchanged natrolites will be presented.

Lee, Y.

2011-12-01

415

Two stage pyrolysis of oil shale using a zeolite catalyst  

Microsoft Academic Search

Oil shales were pyrolysed in a fixed bed reactor and the chemical composition of the oils and gases from the pyrolysis of the oil shales were characterised. The reactor system was then modified to incorporate a second reactor where the derived vapours from oil shale pyrolysis were upgraded on-line using zeolite ZSM-5 catalyst at low pressure. The influence of catalyst

Paul T. Williams; Hafeez M. Chishti

2000-01-01

416

A study of localised galvanic replacement of copper and silver films with gold using scanning electrochemical microscopy  

Microsoft Academic Search

Galvanic replacement represents a highly significant process for the fabrication of bimetallic materials, but to date its application has been limited to either modification of large area metal surfaces or nanoparticles in solution. Here, the localised surface modification of copper and silver substrates with gold through the galvanic replacement process is reported. This was achieved by generation of a localised

Anthony P. O'Mullane; Samuel J. Ippolito; Alan M. Bond; Suresh K. Bhargava

2010-01-01

417

Bacterial Killing by Dry Metallic Copper Surfaces?  

PubMed Central

Metallic copper surfaces rapidly and efficiently kill bacteria. Cells exposed to copper surfaces accumulated large amounts of copper ions, and this copper uptake was faster from dry copper than from moist copper. Cells suffered extensive membrane damage within minutes of exposure to dry copper. Further, cells removed from copper showed loss of cell integrity. Acute contact with metallic copper surfaces did not result in increased mutation rates or DNA lesions. These findings are important first steps for revealing the molecular sensitive targets in cells lethally challenged by exposure to copper surfaces and provide a scientific explanation for the use of copper surfaces as antimicrobial agents for supporting public hygiene.

Santo, Christophe Espirito; Lam, Ee Wen; Elowsky, Christian G.; Quaranta, Davide; Domaille, Dylan W.; Chang, Christopher J.; Grass, Gregor

2011-01-01

418

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

419

Modification of Wood.  

National Technical Information Service (NTIS)

Contents: Theory of chemical plasticization; Properties of plasticized non-ground and ground wood; Technological problems of plasticized non-ground, laminated and ground wood; Some data on the process of pressing of wood-particle boards; Wood modification...

T. A. Darzinsh

1976-01-01

420

Physical and Mechanical Properties of Copper and Copper Alloys  

SciTech Connect

High strength, high conductivity copper alloys are prime candidates for high heat flux applications in fusion energy systems. This chapter reviews the physical and mechanical properties of pure copper and copper alloys with the focus on precipitation-hardened CuCrZr and dispersion-strengthened CuAl25 alloys. The effect of neutron irradiation on copper and copper alloys is reviewed in terms of radiation effects on physical properties and mechanical properties (tensile properties, fracture toughness, fatigue and creep-fatigue), irradiation creep and void swelling. The effect of irradiation on the microstructure of copper and copper alloys and dislocation channeling is also presented. Joining techniques for copper alloys in fusion plasma facing components are briefly discussed.

Li, Meimei [Argonne National Laboratory (ANL); Zinkle, Steven J [ORNL

2012-01-01

421

Male genital modification  

Microsoft Academic Search

By modifying the body in meaningful ways, human beings establish their identity and social status. Lip plugs, ear plugs, penis\\u000a sheaths, cosmetics, ornaments, scarification, body piercings, and genital modifications encode and transmit messages about\\u000a age, sex, social status, health, and attractiveness from one individual to another. Through sociocultural sexual selection,\\u000a male genital modification plays an important role as a sociosexual

Raven Rowanchilde

1996-01-01

422

Selective divalent copper chelation for the treatment of diabetes mellitus.  

PubMed

Oxidative stress and mitochondrial dysfunction have been identified by many workers as key pathogenic mechanisms in ageing-related metabolic, cardiovascular and neurodegenerative diseases (for example diabetes mellitus, heart failure and Alzheimer's disease). However, although numerous molecular mechanisms have been advanced to account for these processes, their precise nature remains obscure. This author has previously suggested that, in such diseases, these two mechanisms are likely to occur as manifestations of a single underlying disturbance of copper regulation. Copper is an essential but highly-toxic trace metal that is closely regulated in biological systems. Several rare genetic disorders of copper homeostasis are known in humans: these primarily affect various proteins that mediate intracellular copper transport processes, and can lead either to tissue copper deficiency or overload states. These examples illustrate how impaired regulation of copper transport pathways can cause organ damage and provide important insights into the impact of defects in specific molecular processes, including those catalyzed by the copper-transporting ATPases, ATP7A (mutated in Menkes disease), ATP7B (Wilson's disease), and the copper chaperones such as those for cytochrome c oxidase, SCO1 and SCO2. In diabetes, impaired copper regulation manifests as elevations in urinary CuII excretion, systemic chelatable-CuII and full copper balance, in increased pro-oxidant stress and defective antioxidant defenses, and in progressive damage to the blood vessels, heart, kidneys, retina and nerves. Linkages between dysregulated copper and organ damage can be demonstrated by CuII-selective chelation, which simultaneously prevents/reverses both copper dysregulation and organ damage. Pathogenic structures in blood vessels that contribute to binding and localization of catalytically-active CuII probably include advanced glycation end products (AGEs), as well as atherosclerotic plaque: the latter probably undergoes AGE-modification itself. Defective copper regulation mediates organ damage through two general processes that occur simultaneously in the same individual: elevation of CuII-mediated pro-oxidant stress and impairment of copper-catalyzed antioxidant defence mechanisms. This author has proposed that diabetes-evoked copper dysregulation is an important new target for therapeutic intervention to prevent/reverse organ damage in diabetes, heart failure, and neurodegenerative diseases, and that triethylenetetramine (TETA) is the first in a new class of anti-diabetic molecules, which function by targetting these copper-mediated pathogenic mechanisms. TETA prevents tissue damage and causes organ regeneration by acting as a highly-selective CuII chelator which suppresses copper-mediated oxidative stress and restores anti-oxidant defenses. My group has employed TETA in a comprehensive programme of nonclinical studies and proof-of-principle clinical trials, thereby characterizing copper dysregulation in diabetes and identifying numerous linked cellular and molecular mechanisms though which TETA exerts its therapeutic actions. Many of the results obtained in nonclinical models with respect to the molecular mechanisms of diabetic organ damage have not yet been replicated in patients' tissues so their applicability to the human disease must be considered as inferential until the results of informative clinical studies become available. Based on evidence from the studies reviewed herein, trientine is now proceeding into the later stages of pharmaceutical development for the treatment of heart failure and other diabetic complications. PMID:22455587

Cooper, G J S

2012-01-01

423

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

424

Hydrogenation of pentynes on cationic forms of zeolite Y  

SciTech Connect

Hydrogenation of the acetylenic hydrocarbons, 1-pentyne and 2-pentyne, on the cationic forms of a type Y zeolite were studied to refine the specific traits of the catalytic action of zeolites in hydrogenation reactions. The employed flow equipment was run under pressure and the 1-pentyne and 2-pentyne were 99% pure. The 2-pentyne was obtained by the isomerization of 1-pentyne in the presence of KOH and subsequent fractional distillation through a column with an efficiency of 20 theoretical plates. For reaction a mixture of the pentyne and n-hexane in a 1:2 ratio was used. The experiments were run in the range 140-220/sup 0/C at 30 atm. Samples were taken at 15 min intervals during experiment, which were analyzed by the GLC method. The amount of catalyst, charged into the reactor, was 5 ml. As catalysts we used zeolite NaY (SiO/sub 2//Al/sub 2/O/sub 3/ = 5.0) and also the Li/sup +/, K/sup +/, Ca/sup 2 +/, and La/sup 3 +/ forms of this zeolite, which were prepared by the ion exchange method. Prior to experiment the catalysts were heated for 5 h in an air stream at 500/sup 0/. The yield of the hydrogenation products remained constant during the time of experiment, or in some cases it decreased somewhat. Results indicated that cis addition of hydrogen to the triple bond occurs when 2-pentyne is hydrogenated and that the specific activity of a zeolite in the hydrogenation of pentynes is determined by the higher ionization potential of the cation.

Kharlamov, V.V.; Kharatishvili, N.G.; Minachev, Kh.M.

1982-04-20

425

Copper Proteins and Oxygen  

PubMed Central

A comprehensive survey of the interaction of the copper proteins and oxygen is presented including a correlation of structure, function, and other properties of the known copper oxidases and of hemocyanin. The origin of their blue color and the structure of copper complexes and copper proteins are related to the oxidation state of copper ion and relevant electronic transitions probably arising from the formation of charge transfer complexes. The oxygen reactions of hemocyanin, ceruloplasmin, and cytochrome oxidase show half-saturation values far below the other Cu enzymes. The formation of hydrogen peroxide as a reaction product is associated with the presence of one Cu atom per oxidase molecule or catalytic system. Water is the corresponding product of the other Cu oxidases with four or more Cu atoms per molecule, except for monoamine oxidase. Mechanisms for the oxidase action of the two and four electron transfer Cu oxidases and tyrosinase are proposed. These reactions account for the number, the oxidation-reduction potential, and the oxidation state of Cu in the resting enzyme, the cyclical change from Cu(II) to Cu(I), the diatomic nature of O2, the sequence of the oxidation and reduction reactions, and other salient features. The catalytic reactions involved in the oxidation of ascorbic acid by plant ascorbate oxidase, ceruloplasmin, and Cu(II) are compared. Finally the substrate specificity, inhibitory control, and the detailed mechanism of the oxidase activity of ceruloplasmin are summarized.

Frieden, Earl; Osaki, Shigemasa; Kobayashi, Hiroshi

1965-01-01

426

Catalytic dehydrocondensation of methane towards benzene and naphthalene on transition metal supported zeolite catalysts: templating role of zeolite micropores and characterization of active metallic sites  

Microsoft Academic Search

The catalytic dehydrocondensation of methane to benzene and naphthalene with a bulky of hydrogen on transition metal supported zeolite catalysts is one of strategies for the catalytic conversion of methane and a challenging topic in heterogeneous catalysis. This paper is dealt with the current progress in catalytic dehydrocondensation of methane towards benzene and naphthalene on transition metal supported zeolite catalysts,

Yuying Shu; Masaru Ichikawa

2001-01-01

427

Effect of the Si\\/Al ratio and of the zeolite structure on the performance of dealuminated zeolites for the reforming of hydrocarbon mixtures  

Microsoft Academic Search

Various 12-membered ring pore zeolites were employed for the reforming of synthetic hydrocarbon mixtures which simulate industrial naphthas. All the zeolites were dealuminated to various extents. It was found that, under the present conditions over the samples which are slightly dealuminated, bimolecular-condensation reactions followed by recracking are responsible for the relatively large selectivities of Câ paraffins. The monomolecular cracking (via

Panagiotis G. Smirniotis; Wenmin Zhang

1996-01-01

428

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

429

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

430

Synchrotron x-ray and optical studies of the structure of HgSe semiconductor nanoclusters confined in zeolite L and zeolite Y  

NASA Astrophysics Data System (ADS)

HgSe semiconductor nanoclusters were fabricated in nearly spherical pores of zeolite Y and one-dimensional (1D) tubular pores of zeolite L. Anomalous x-ray scattering (AXS) data sets were collected on both HgSe/zeolite Y and HgSe/zeolite L systems, together with optical studies (Raman and UV-visible absorption). Two distinct structural models were determined by performing the Rietveld refinement on AXS data sets. Given the existence of a pronounced diffuse scattering in both filled zeolites and our refined models without the observed diffuse background, for each system, we propose the existence of an average HgSe nanocluster or a 1D nanostructure and the related disorder within the nanocluster which gives off the diffuse scattering. Optical studies were used to complement our x-ray structural work.

Abeykoon, A. M. M.; Castro-Colin, M.; Anokhina, E. V.; Iliev, M. N.; Donner, W.; Jacobson, A. J.; Moss, S. C.

2008-02-01

431

Synchrotron X-ray and Optical Studies of the Structure of HgSe Semiconductor Nanoclusters Confined in Zeolite L and Zeolite Y  

SciTech Connect

HgSe semiconductor nanoclusters were fabricated in nearly spherical pores of zeolite Y and one-dimensional (1D) tubular pores of zeolite L. Anomalous x-ray scattering (AXS) data sets were collected on both HgSe/zeolite Y and HgSe/zeolite L systems, together with optical studies (Raman and UV-visible absorption). Two distinct structural models were determined by performing the Rietveld refinement on AXS data sets. Given the existence of a pronounced diffuse scattering in both filled zeolites and our refined models without the observed diffuse background, for each system, we propose the existence of an average HgSe nanocluster or a 1D nanostructure and the related disorder within the nanocluster which gives off the diffuse scattering. Optical studies were used to complement our x-ray structural work.

Abeykoon,A.; Castro-Colin, M.; Anokhina, E.; Iliev, M.; Donner, W.; Jacobson, A.; Moss, S.

2008-01-01

432

Systems Biology Approach in Chlamydomonas Reveals Connections between Copper Nutrition and Multiple Metabolic Steps[C][W][OA  

PubMed Central

In this work, we query the Chlamydomonas reinhardtii copper regulon at a whole-genome level. Our RNA-Seq data simulation and analysis pipeline validated a 2-fold cutoff and 10 RPKM (reads per kilobase of mappable length per million mapped reads) (~1 mRNA per cell) to reveal 63 CRR1 targets plus another 86 copper-responsive genes. Proteomic and immunoblot analyses captured 25% of the corresponding proteins, whose abundance was also dependent on copper nutrition, validating transcriptional regulation as a major control mechanism for copper signaling in Chlamydomonas. The impact of copper deficiency on the expression of several O2-dependent enzymes included steps in lipid modification pathways. Quantitative lipid profiles indicated increased polyunsaturation of fatty acids on thylakoid membrane digalactosyldiglycerides, indicating a global impact of copper deficiency on the photosynthetic apparatus. Discovery of a putative plastid copper chaperone and a membrane protease in the thylakoid suggest a mechanism for blocking copper utilization in the chloroplast. We also found an example of copper sparing in the N assimilation pathway: the replacement of copper amine oxidase by a flavin-dependent backup enzyme. Forty percent of the targets are previously uncharacterized proteins, indicating considerable potential for new discovery in the biology of copper.

Castruita, Madeli; Casero, David; Karpowicz, Steven J.; Kropat, Janette; Vieler, Astrid; Hsieh, Scott I.; Yan, Weihong; Cokus, Shawn; Loo, Joseph A.; Benning, Christoph; Pellegrini, Matteo; Merchant, Sabeeha S.

2011-01-01

433

Preparation of zeolite A and faujasite membranes from a clear solution  

SciTech Connect

Zeolite A and faujasite- (FAU-)type zeolite membranes were prepared under identical conditions from solutions of the same composition, with the only difference being the seed crystal used. The zeolite A membrane was formed on a substrate seeded with zeolite A crystals, while the FAU membrane was formed with zeolite Y seeds. The induction period of clear solution was used to prevent the influence of precipitated crystals that will eventually form in the clear solution and to keep the composition of the synthesis solution constant. Zeolite crystals increased in size with synthesis time and formed a continuous membrane on a porous substrate. Selectivity in a liquid mixture separation by pervaporation increased as crystals grew, indicating a decrease in intercrystalline region size.

Kumakiri, Izumi; Yamaguchi, Takeo; Nakao, Shinichi

1999-12-01

434

Effects of surface and morphological properties of zeolite on impedance spectroscopy-based sensing performance.  

PubMed

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 (CeO(2)) 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

2012-10-01

435

Removal of trimethylamine by adsorption over zeolite catalysts and deodorization of fish oil.  

PubMed

Trimethylamine (TMA) is the main agent for the odor often associated with fouling fish, some infections, and bad breath. This study focused on the adsorption of TMA over various microporous zeolites for application in the low-temperature deodorization of fishy odor from raw fish oil. The faujasite (Si/Al=3) zeolite exhibited the high adsorption ability, which, in combination with its wide surface area and pore volume, may have induced the high adsorption ability. The H-mordenite (Si/Al=10) zeolite exhibited a large TMA adsorption. It was considered to have generated more attractive adsorption with TMA ions, because TMA interacted briskly with cations of acid sites on the zeolites. The fishy odor of raw fish oil was considerably reduced by low-temperature adsorption on the zeolites. The surface area of the zeolites retained most of the TMA adsorption ability, and their acid strength further enhanced the adsorption ability. PMID:19692177

Chung, Kyong-Hwan; Lee, Ki-Young

2009-07-28

436

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

2009-05-04

437

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.

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

2012-01-01

438

Selective oxidation of olefins within organic dye cation-exchanged zeolites  

SciTech Connect

This paper reports selectivity in the products during single oxygen mediated oxidation of olefins included within dye-exchanged X and Y zeolites. Singlet oxygen is generated within a zeolite by irradiating a thiazine dye exchanged into zeolites. Oxazine and thiazine dye molecules can be readily exchanged for alkali cations present in the interior of faujasite (X and Y) zeolites. Depending on the status of hydration, these dye molecules exist either in monomeric or dimeric forms. We show here that when a thiazine dye molecule is present in its monomeric form within a zeolite, it serves as an excellent singlet oxygen sensitizer. Utilizing zeolite supercages as `active reaction cavities`, we have directed the reactive oxygen toward a particular face of the olefin and obtained a high selectivity in the products of oxidation. 18 refs., 4 figs.

Li, X.; Ramamurthy, V. [Tulane Univ., New Orleans, LA (United States)

1996-10-30

439

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...

440

Multilevel Dual Damascene copper interconnections  

Microsoft Academic Search

Copper has been acknowledged as the interconnect material for future generations of ICs to overcome the bottlenecks on speed and reliability present with the current Al based wiring. A new set of challenges brought to the forefront when copper replaces aluminum, have to be met and resolved to make it a viable option. Unit step processes related to copper technology

S. Lakshminarayanan

1997-01-01

441

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

442

A high-silica zeolite with a 14-tetrahedral-atom pore opening  

Microsoft Academic Search

ZEOLITES (microporous aluminosilicates) and related molecular sieves have found wide application as catalysts, sorbents and ion-exchange materials. New zeolites with large pores are much in demand1-4, and have been sought for several decades4-7. All known zeolites, both natural and synthetic, contain pores comprised of 12 or fewer tetrahedrally coordinated silicon or aluminium atoms (T-atoms), but several microporous aluminophosphates with wider

C. C. Freyhardt; M. Tsapatsis; R. F. Lobo; K. J. Balkus; M. E. Davis

1996-01-01

443

Pharmacokinetic Study of Zeolite A, Sodium Aluminosilicate, Magnesium Silicate, and Aluminum Hydroxide in Dogs  

Microsoft Academic Search

Zeolite A is a synthetic zeolite which may have therapeutic utility in osteoporotic individuals because of its ability to stimulate bone formation. A study of Zeolite A (30 mg\\/kg), sodium aluminosilicate (16 mg\\/kg), magnesium trisilicate (20 mg\\/kg), and aluminum hydroxide (675 mg) was designed in beagle dogs. The purpose of this study was to compare the oral bioavailability of silicon

Eugenio A. Cefali; Joseph C. Nolan; William R. McConnell; Denise Lowe Walters

1995-01-01

444

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

445

The enthalpy of occlusion of the (lithium chloride + potassium chloride) eutectic salt in zeolite 4A  

Microsoft Academic Search

The molar enthalpy of occlusion of the (lithium chloride + potassium chloride) eutectic salt in zeolite 4A at the salt melting temperature ?occHm(Tfus) was measured using differential scanning calorimetry. It was found that up to a mole fraction of the salt x= 0.931 in the (salt + zeolite) mixture, which is near the expected zeolite occlusion limit, ?occHm(Tfus) was negative

Dusan Lexa

1999-01-01

446

Effect of some additives on synthesis of zeolite from coal fly ash  

Microsoft Academic Search

Hydrothermal conversion of fly ash into zeolites was conducted and the effects of the addition of sodium halide and waste solutions produced after zeolitization of fly ash, as well as the adjustment of the Si\\/Al ratio prior to synthesis process on the formation and cation exchange capacity (CEC) of zeolite product were evaluated. Both the addition of NaCl and NaF

Deyi Wu; Bohua Zhang; Li Yan; Hainan Kong; Xinze Wang

2006-01-01

447

Synthesis of zeolite from coal fly ashes with different silica–alumina composition  

Microsoft Academic Search

Coal fly ashes can be converted into zeolites by hydrothermal alkaline treatment. This study focuses on the effect of Si\\/Al molar ratio of the fly ash source on the type of formed zeolite, which also is affected by the alkaline condition. The fly ashes were mixed with an aqueous NaOH solution and hydrothermally treated at about 100°C. Zeolite Na–P1 and\\/or

Miki Inada; Yukari Eguchi; Naoya Enomoto; Junichi Hojo

2005-01-01

448

n-Pentane\\/ i-pentane separation by using zeolite–PDMS mixed matrix membranes  

Microsoft Academic Search

The performances of various zeolite filled polymeric membranes in the separation of n-pentane from i-pentane were investigated as a function of zeolite loading and various experimental conditions. Polydimethylsiloxane (PDMS) was chosen as the polymer phase and HZSM-5, NaZSM-5, 4A and 5A were used as zeolite fillers. Different Si\\/Al ratios and different activation temperatures were tested for ZSM-5 and A type

?. Birgül Tantekin-Ersolmaz; Lara ?enorkyan; Niso Kalaonra; Melkon Tatl?er; Ay?e Erdem-?enatalar

2001-01-01

449

Experimental Research of Ammonia Nitrogen in Micro-Polluted Water by Zeolite with Enhanced Coagulation  

Microsoft Academic Search

Organic matter and turbidity in micro-polluted water could influence adsorption result of zeolite. Enhanced coagulation could remove organic matter and turbidity effectively, reduce the competition between organic matter and ammonia nitrogen, increase ammonia nitrogen strain away rate. By adding zeolite powder after adding coagulants, when coagulant dose achieve 3mg\\/L, the strain away rate of zeolite could increase 7%. The removal

Fu Hong-yuan; Cheng Guan-wen; Xu Zi-han; Jiang Chu-cheng; Ye Qing-wang; Zhang Li-hui

2012-01-01

450

Removal of Ammonia-nitrogen from Micro-polluted Raw Water by O3Biological Zeolite  

Microsoft Academic Search

O3-biological zeolite processes was used to treat micro-polluted raw water, The results show that zeolite modified by NaCl is efficiency on ammonia-nitrogen removal, at pH 6~9 and 150min stirring time, the ammonia-nitrogen removal rate is 71.2%;During the culture of biofilm, ammonia-nitrogen removal rate of water treated by biological zeolite increased after decreasing .When the biofilm is mature, the removal rate

Tan Wanchun; Pan Zhengke; Wang Yunbo; Wang Qiuyun

2011-01-01

451

Pervaporation dehydration of isopropanol-water mixtures using chitosan zeolite-a membranes  

Microsoft Academic Search

Pervaporation (PV) dehydration of isopropanol (IPA) using modified chitosan membranes was studied. The membranes were prepared from chitosan and were modified by using zeolite-A. Pre-weighed amount of zeolite-A was added into acidic solvent and stirred to produce homogeneous solution. Chitosan flakes were then added into the solution and stirred overnight. Various ratios of zeolite-A and chitosan from 1:20 to 1:2

Ngoc Tram

452

Gas sensing with zeolite-coated quartz crystal microbalances—principal component analysis approach  

Microsoft Academic Search

Three different zeolites, which are zeolite A, silicalite-1 and sodalite, were deposited on quartz crystal microbalance (QCM) oscillators with fundamental resonance frequency of 4.7MHz. Three QCMs, as well as one without zeolites as a reference, were exposed to single gases such as NO, SO2 and H2O in He at 443K. The frequency shifts and their differential values to time were

Isao Sasaki; Hiroshi Tsuchiya; Masateru Nishioka; Masayoshi Sadakata; Tatsuya Okubo

2002-01-01

453

Zeolite\\/rock phosphate—a novel slow release phosphorus fertiliser for potted plant production  

Microsoft Academic Search

A glasshouse study was undertaken to determine if the zeolite mineral clinoptilolite from an Australian deposit in combination with rock phosphate (RP) could significantly enhance the uptake of P by sunflowers. The zeolite\\/RP combination was intended to act as an exchange-fertiliser, with Ca2+ exchanging onto the zeolite in response to plant uptake of nutrient cations (NH4+ or K+) enhancing the

Harry W. Pickering; Neal W. Menzies; Malcolm N. Hunter

2002-01-01

454

Comparative investigations on plasma catalytic methane conversion to higher hydrocarbons over zeolites  

Microsoft Academic Search

Zeolites are an important class of industrial catalyst. In this investigation, the application of zeolites for plasma catalytic methane conversion (PCMC) to higher hydrocarbons at very low gas temperatures (room temperature to 200°C) has been addressed. Zeolites NaY, HY, NaX, NaA, Linde Type 5A and Na-ZSM-5 have been tested for the application in PCMC. The products contain C2 hydrocarbons (acetylene,

Chang-jun Liu; Richard Mallinson; Lance Lobban

1999-01-01

455

Investigation of mircroorganisms colonising activated zeolites during anaerobic biogas production from grass silage  

Microsoft Academic Search

The colonisation of activated zeolites (i.e. clinoptilolites) as carriers for microorganisms involved in the biogas process was investigated. Zeolite particle sizes of 1.0–2.5mm were introduced to anaerobic laboratory batch-cultures and to continuously operated bioreactors during biogas production from grass silage. Incubation over 5–84days led to the colonisation of zeolite surfaces in small batch-cultures (500ml) and even in larger scaled and

S. Weiß; A. Zankel; M. Lebuhn; S. Petrak; W. Somitsch; G. M. Guebitz

2011-01-01

456

Surface-modified Y zeolite-filled chitosan membrane for direct methanol fuel cell  

Microsoft Academic Search

Hybrid membranes composed of chitosan (CS) as organic matrix and surface-modified Y zeolite as inorganic filler are prepared and their applicability for DMFC is demonstrated by methanol permeability, proton conductivity and swelling property. Y zeolite is modified using silane coupling agents, 3-aminopropyl-triethoxysilane (APTES) and 3-mercaptopropyl-trimethoxysilane (MPTMS), to improve the organic–inorganic interfacial morphology. The mercapto group on MPTMS-modified Y zeolite is

Hong Wu; Bin Zheng; Xiaohong Zheng; Jingtao Wang; Weikang Yuan; Zhongyi Jiang

2007-01-01

457

Catalytic Activity of Boron-Beta Zeolite Modified with Indium in the Epoxidation of Cinnamyl Alcohol  

Microsoft Academic Search

Liquid-phase epoxidation of cinnamyl alcohol was carried out with hydrogen peroxide as oxidizing agent using indium-containing boron- and aluminium-beta zeolites. It was proved that InO+ ions, created by oxidation of univalent indium cations incorporated into beta zeolite by reductive solid-state ion exchange, play an important role in the activation of hydrogen peroxide. The indium-hydroperoxo complex formed in beta zeolite pores

Rayna Dimitrova; Yanka Neinska; Magdolna R. Mihályi; Tanya Tsoncheva; Maya Spassova

2001-01-01

458

Experimental and theoretical approaches to the study of TMI-zeolite (TM = Fe, Co, Cu)  

Microsoft Academic Search

Transition metal ions in zeolites TMI-zeolite (TM=Fe, Co, Cu) attract great attention due to their potentialities as catalysts. In the recent years, the high efficiency of TMI-zeolites for the selective catalytic reduction (SCR) of contaminated flue gases has been demonstrated. It has been shown that the structure of the framework, the nature and location of extraframework cation species play a

Dorothée Berthomieu; Nicolas Jardillier; Gérard Delahay; Bernard Coq; Annick Goursot

2005-01-01

459

Environmental Applications of Natural Zeolitic Materials Based on Their Ion Exchange Properties  

Microsoft Academic Search

\\u000a Present and potential use of natural zeolites as cation exchangers in environmental protection is reviewed. Siliceous zeolites,\\u000a such as chabazite, clinoptilolite, mordenite and phillipsite, exhibit good selectivities for cations with low charge density,\\u000a e.g., Cs+ and NH4\\u000a +, and for cations with low hydration energy, such as Pb2+. Zeolitised tuffs, containing the mentioned zeolites, may therefore be utilised for removing

C. Colella; Piazza Ie; V. Tecchio

460

Calorimetric Study of Adsorption of Alkanes in High-Silica Zeolites  

Microsoft Academic Search

Isosteric heats and adsorption isotherms were measured for combinations of three alkanes (methane, ethane, propane) on a series of six high-silica zeolites (TON, MTW, UTD-1, MFI, FER, FAU). Three of these zeolites (TON, MTW, UTD-1) have one-dimensional channels, two (MFI, FER) have two-dimensional intersecting channels, and FAU has spherical cavities. Since the adsorbate molecules are nonpolar and the zeolites possess

Scott Savitz; Flor Siperstein; Raymond J. Gorte; Alan L. Myers

1998-01-01

461

Effect of the framework structure on the dealumination–realumination behavior of zeolite  

Microsoft Academic Search

The dealumination–realumination processes of MOR, MFI, FER and BEA zeolites were investigated by means of XRD, 27Al MAS NMR, FT-IR and N2 adsorption. Framework aluminums of BEA zeolite were easily removed from the framework by HCl treatment. Dealumination of MOR zeolite was performed by a combination of calcination in air and HCl treatment. However, in the case of MFI and

Y Oumi; S Nemoto; S Nawata; T Fukushima; T Teranishi; T Sano

2003-01-01

462

The influence of catalyst regeneration on the composition of zeolite-upgraded biomass pyrolysis oils  

Microsoft Academic Search

The composition of oils derived from the on-line, low pressure zeolite upgrading of biomass pyrolysis oils from a fluidized bed pyrolysis unit have been investigated in relation to the regeneration of the zeolite catalyst. The catalyst used was H-ZSM-5 zeolite. The gases were analysed by packed column gas chromatography. The composition of the oils before catalysis and after catalyst upgrading

Paul T. Williams; Patrick A. Horne

1995-01-01

463

Reduction of NO by C 1 -C 4 hydrocarbons at cobalt-containing zeolites  

Microsoft Academic Search

Data are given on the activity of high-silicon zeolites in the reduction of nitrogen oxides by methane and C2-C4 hydrocarbons (paraffins and olefins). It was shown that the highest degree of conversion of NO during selective catalytic reduction is obtained at the mixed forms of Co-containing zeolites at temperatures 100°C lower than at the usual Co-containing zeolites of the ZSM-5

S. N. Orlik; V. L. Struzhko; V. P. Stasevich; M. G. Martsenyuk-Kukharuk

1996-01-01

464

Zeolites modified by CuCl for separating CO from gas mixtures containing CO 2  

Microsoft Academic Search

Although zeolites such as NaY and 13X adsorb CO2 much more than CO, the adsorption amount of CO2 and CO can be reversed if the zeolites are modified with CuCl. When zeolite NaY or 13X is mixed with CuCl and heated, high\\u000a CO adsorption selectivity and capacity can be obtained. Isotherms show the adsorbents have CO capacity much higher than

Youchang Xie; Jiaping Zhang; Jianguo Qiu; Xianzhong Tong; Jinping Fu; Ge Yang; Haojie Yan; Youqi Tang

1997-01-01

465

Template-removal-associated microstructural development of porous-ceramic-supported MFI zeolite membranes  

Microsoft Academic Search

Defect-free thin MFI zeolite films were synthesized on porous ?-alumina and yttria-doped zirconia (YZ) substrates by an in situ crystallization method using tetrapropylammonium hydroxide (TPAOH) as a template. The microstructure evolution of the supported zeolite films during calcination for template removal was studied by high-temperature X-ray diffraction and in situ gas permeance. Removal of the template from the zeolite films

Junhang Dong; Y. S Lin; Michael Z.-C Hu; Roberta A Peascoe; E. Andrew Payzant

2000-01-01

466

Hollow shells of high surface area graphitic N-doped carbon composites nanocast using zeolite templates  

Microsoft Academic Search

Hollow shells of porous nitrogen-doped carbon materials with high surface area have been prepared using zeolite templates (zeolite ? or silicalite-I) and acetonitrile as carbon source via chemical vapour deposition (CVD) performed at between 800 and 1000°C. The nitrogen content varies between 3.0 and 7.9wt.% depending on the zeolite template and CVD temperature. The carbon materials generally retain the particle

Zhuxian Yang; Yongde Xia; Robert Mokaya

2005-01-01

467

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

468

Posttranslational modifications regulate microtubule function  

Microsoft Academic Search

The ??-tubulin heterodimer, the building block of microtubules, is subject to a large number of post-translational modifications, comparable in diversity to the intensively studied histone modifications. Although these unusual modifications are conserved throughout evolution, their functions have remained almost completely elusive. Recently, however, important advances in the understanding of how tubulin modifications regulate function and organization have been made.

Klaus Weber; Stefan Westermann

2003-01-01

469

Stability of catalytic activity and selectivity of zeolites differing in chemical composition  

SciTech Connect

The authors determine the operating time limits for a number of ZSM zeolites in relation to the contents of Al and Na cations. The authors have established that the zeolites operate stably for a limited time, and that the zeolite operating time for a given crystal structure decreases with increase content of Al. After the period of stable operation, the activity drops off quickly. The authors examine three alternative hypotheses in order to explain the fact that coke formation reactions do not take place in the ZSM zeolites.

Echevskii, G.V.; Ione, K.G.; Leonov, V.E.; Nosyreva, G.N.; Zubenko, A.E.

1986-02-10

470

Influence of zeolites in PDMS membranes. Pervaporation of water/alcohol mixtures  

SciTech Connect

A strong influence of the zeolite was found on the pervaporation of alcohol/water mixtures using filled PDMS membranes. In all cases, the zeolites reduced the swelling of the PDMS. Incorporation of the hydrophilic zeolite Y increased water fluxes, while ZSM-5 reduced both water and alcohol fluxes due to a partial retention of these molecules in the zeolite. For branched alcohols, the extreme importance of diffusion led to a strong dependency of selectivity and flux on temperature. Compared with commercially available PDMS membranes, better results were realized with the self-prepared membranes. 19 refs., 7 figs., 1 tab.

Vankelecom, I.F.J.; Depre, D.; De Beukelaer, S.; Uytterhoeven, J.B. [Centrum voor Oppervlaktechemie en Katalyse, Leuven (Belgium)

1995-08-31

471

[Preparation and evaluation of in-situ synthesis zeolite gas-liquid modified columns].  

PubMed

A new kind of NaA zeolite column has been prepared by in-situ synthesis technique. In comparing with traditional coating method, the in-situ NaA zeolite carrier is much more uniform and rigid. Several kinds of zeolite gas-liquid modified columns have been prepared with this in-situ technology, which showed satisfactory features in separation property and thermal stability. The successful utilization of mini-length and wide-bore columns showed good practical prospect of this new kind of zeolite column. PMID:12545470

Kou, D M; Wu, J M; Li, Z Y; Liu, M; Xiang, S H

2001-11-01

472

Electrical Conductivity Response toward Ketone Vapors of Poly(Para-Phenylene Vinylene)/Zeolite Y Composites  

NASA Astrophysics Data System (ADS)

Investigation of the effect of 3 different types of cation types in Zeolite Y; Zeolite Y(Si/Al=5.1, Na+), Zeolite Y(Si/Al=5.1, NH3+), Zeol