- Three-dimensional mesoporous gallosilicate with Pm3n symmetry and its unusual catalytic performances
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Three-dimensional, mesoporous-cage-type, GaSBA-1 materials with different nSi/NGa ratios have been successfully prepared for the first time by using a low hydrochloric acid to silicon (nHCl/n Si) molar ratio in
- Srinivasu, Pavuluri,Vinu, Ajayan
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- Investigation of catalytic activity of CrSBA-1 materials obtained by direct method in the dehydrogenation of propane with CO2
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A series of the Cr-containing SBA-1 (xCrSBA1) cubic mesoporous catalysts with various Cr/Si molar ratios have been prepared by direct method using cetyltriethylammonium bromide, ammonium dichromate, tetraethyl orthosilicate and hydrochloric acid. The obtained materials have been characterized by different physicochemical techniques including ICP, XRD, UV-vis DRS, H2-TPR and N2-adsorption. XRD and N2-adsorption results have revealed that xCrSBA1 materials possess well organized three-dimensional pore structure. However, incorporation of Cr into the SBA-1 framework leads to small perturbation of the structural order. ICP results have shown that the amount of Cr incorporation in SBA-1 can be controlled by adjustment of the molar ratio of (NH4)2Cr2O7 to Si(C2H5O)4 in the gel. Finally, the catalytic activity of pure SBA-1 and Cr-containing SBA-1 materials were investigated in the dehydrogenation of propane with CO2. In the case of the most active, 0.04CrSBA1 catalyst, the effect of various reaction parameters such as, reaction temperature, reaction time and feed gas composition on the conversion of propane, yield and selectivity to propene as well as on molar ratio of CO/H2 has been evaluated. Moreover, stability of the catalyst during the dehydrogenation/regeneration conditions was studied as well. It has been found that during the fourth consecutive cycle the catalyst undergoes two types of deactivation processes - reversible and irreversible. The former is caused mainly by the coke deposition, which can easily overcome by air treatment of the catalyst at 550 °C. The latter one, insignificant, is due to partial collapse of mesoporous structure of the catalysts.
- Michorczyk, Piotr,Ogonowski, Jan,Niemczyk, Marta
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- Effect of Head-Group Size on Micellization and Phase Behavior in Quaternary Ammonium Surfactant Systems
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The micellization and phase equilibria in aqueous solutions of cationic quaternary ammonium bromide surfactants of the type alkyltrimethyl-, -ethyl-, -propy-, -butyl-, and -pentylammonium bromide have been investigated as a function of alkyl chain length, electrolyte concentration, and temperature.A large isotropic (micellar) phase is observed in triethyl- and tripropylammonium surfactants, which demixes into two conjugate phases on warming in the case of the alkyltributylammonium bromides.Liquid-liquid phase separation is also observed for tetradecyltripentylammonium bromide.Critical micelle concentrations are found to decrease with increasing hydrophobicity of the surfactant ion, but the free energy of micellization of tetradecyltributylammonium bromide is the same as that of tetradecyltrimethylammonium bromide over a range of temperatures.Some evidence is found for the formation of premicellar aggregates in tributylammonium surfactants at elevated temperatures, consistent with significant polydispersity and changing monomer concentrations observed previously.The results are discussed in terms of the hydrophobic and electrostatic contributions of the free energy of micellization, and some interferences are drawn regarding the nature of the interactions which give rise to phase separation.
- Buckingham, Scott A.,Garvey, Christopher J.,Warr, Gregory G.
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- Investigation on the drying induced phase transformation of mesoporous silica; A comprehensive understanding toward mesophase determination
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Phase transformation of mesoporous silica during the drying process is investigated. Assynthesized hexagonal p6mm obtained under the conditions used in this study is transformed to cubic Ia3d as drying proceeds, even at room temperature. Prolonged synthes
- Ogura, Masaru,Miyoshi, Hayato,Naik, Sajo P.,Okubo, Tatsuya
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- In situ NMR and XRD studies of the growth mechanism of SBA-1
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In situ 17O, 14N and 29Si nuclear magnetic resonance (NMR) coupled with in situ energy dispersive X-ray diffraction (EDXRD) have been used to investigate the growth of the siliceous mesoporous material, SBA-1, synthesised
- Egger,Anderson,Tiddy,Casci
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- New chemical family of [n-CxH(2X+1)Net3][BeT3Me] showing ionic plastic-crystal (x = 4, 5), rotator-crystal (x = 6, 7) and liquid-crystal phases (X = 816)
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New ionic liquid crystals of [n-CxH(2x+1)NEt3][BEt3Me] (abbreviated to [CxNEt3][BEt3Me]) were detected for species with even numbers of 8 ˉ x ˉ 16. In contrast, plastic- and rota
- Yamada, Yudai,Kashimoto, Erina,Honda, Hisashi
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p. 1289 - 1298
(2019/09/18)
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- Acetalization of heptanal over Al-SBA-1 molecular sieve
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Al-SBA-1 (Si/Al = 40, 80 and 120) and Al,Mg-SBA-1 (Si/(Al + Mg) = 40 and 80) molecular sieves were synthesized and characterized. Acetalization of n-heptanal with methanol was studied under autogenous pressure between 80 and 150 °C. Since protonation of n
- Venkatachalam,Palanichamy,Murugesan
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p. 299 - 303
(2011/07/31)
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- USE OF QUATERNARY AMMONIUM COMPOUNDS AS SPECIFIC BLOCKERS OF TRANSPORT THROUGH AQUAPORIN, COMPOSITIONS COMPRISING THE COMPOUNDS AND METHOD OF SELECTING THE COMPOUNDS
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The present invention relates to the use of quaternary ammonium compounds for the preparation of a composition for specifically blocking transport through a particular type of aquaporin. The invention further relates to compositions comprising such quaternary ammonium compounds for use in various applications.
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Page/Page column 17-18
(2008/06/13)
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- Synthesis of ω-hydroxy quaternary ammonium bolaform surfactants
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Several members of a novel class of ω-substituted asymmetric bolaform surfactants have been synthesized in order to investigate their surfactant and biological properties. The ω-hydroxy trialkylammonium and pyridinium surfactants have significant antimicrobial and antifungal activity relative to their conventional analogues. For conventional quaternary ammonium alkyl surfactants, increasing the hydrocarbon chain length causes a decrease in the surfactant monomer solubility and a corresponding decrease in the biological activity. No such trend is observed for the ω-hydroxy quaternary ammonium bromide series.
- Davey, Tim W.,Hayman, Alan R.
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p. 581 - 586
(2007/10/03)
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- Enantioselective cleavage of esters by histidine-containing tripeptides in micellar solutions of various hexadecyltrialkylammonium bromide surfactants
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Cleavage of chiral p-nitrophenyl esters derived from the amino acid phenylalanine by histidine-containing tripeptides has been studied in micellar solutions of four quaternary ammonium surfactants.Enzyme-like enantioselectivities up to kL/kD = 131 (at 0 deg C) are observed.The enantioselectivity can be rationalized by assuming a hydrophobically driven stabilizing hydrogen bond between the L enantiomer of the ester and the tripeptide in the transition state of the reaction.This hydrogen bond is absent in the reaction with the D enantiomer of the ester.The transition state has an amphipolar character and is stabilized by the micellar environment.The hydrophilic-hydrophobic balance of the reactants, which affects the transition state, was optimized by varying the composition of the tripeptide and the length of the N-protecting groups in the tripeptide and the substrate.The activities and enantioselectivities depend on the structure of the quaternary ammonium surfactant headgroup.Increasing the size of this headgroup leads to an increase in rate of hydrolysis of the L ester and hence to an increase in enantioselectivity.This effect is attributed to a change in the degree of ion-pair formation with a carboxylate group that is present in the peptides.Compared to previous studies the results indicate that a chiral surfactant is not required for obtaining high enantioselectivities.
- Cleij, Marco C.,Drenth, Wiendelt,Nolte, Roeland J. M.
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- Micellar Enhancements of Rates of SN2 Reactions of Halide Ions. The Effect of Headgroup Size
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Observed first-order rate constants for reaction of methyl naphthalene-2-sulfonate with Cl- or Br- in micelles of cetyltrialkylammonium halide (C16H33NR3X, R = Me,Et,n-Pr,n-Bu, X=Cl,Br) increase monotonically with increasing surfactant and halide ion concentrations and tend to limiting values.The variation of rate constants with concentrations of surfactant and halide ions can be fitted to an equation that accounts for the distribution of both reactants between water and micelles.Fractional micellar ionization, α, increases, i.e., the affinity of the micelles for the halide ion decreases, with increasing bulk of the N-alkyl groups, but the second-order rate constants at the micellar surface and the overall rate constants increase.The rate effects of the micelles of the bromide ion surfactants can be understood in terms of NMR evidence on the micellar binding of the reactants and their location at the micellar surface.The reactivity increase with increasing headgroup bulk is related to the disruption of the hydration of Br- and to the electrostatic interaction of the naphthalene ?-system with cationic nitrogen.
- Bacaloglu, Radu,Bunton, Clifford A.,Ortega, Francisco
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p. 1497 - 1502
(2007/10/02)
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- Hair rinse composition
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A hair rinse composition having improved rinsing performance and a process specified to prepare the same. The composition according to the invention comprises (A) 0.05 to 0.5 wt % of cationic surface active agent, and (B) a higher alcohol or a glycerine mono fatty acid ester having a melting point not lower than 45° C. The ingredient (B) should be contained in an amount of 3 to 15 times by weight to ingredient (A). The composition is prepared by diluting a highly concentrated emulsified product containing 0.4 to 34 wt % of ingredient (A) and (B) in total with 1 to 20 times by weight to the emulsified product of water.
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- The Effect of Cationic Detergents on the Spectral Properties of Pontachrome Azur blue and its Metal(III)-complexes - Micell Effect or Ternary Complex Formation ?
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The results of studies of the metachromasy effect of pontachrome azur blue and its lakes, preferably with aluminium, and hexadecyl-, tetradecyl-, dodecyl- and decyltriethyl-ammonium-bromide, respectively can be explained on the basis of ternary complex formation.The surfactants can be applied at concentrations far below its critical micelle concentrations thus excluding micelle effects.
- Seidel, A.,Hoyer, E.
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p. 299 - 308
(2007/10/02)
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- PHOSPHORORGANISCHE VERBINDUNGEN 95. Beschleunigte Hydrolyse von Organophosphorverbindungen durch Phasentransferkatalyse und H2O2 als Supernucleophil
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The alkaline hydrolyses of the physiologically active phosphor compounds: butyl-phenylfluorophosphonate 1 and di-isopropyl-fluorophosphate were studied under phase-transfer (PT) conditions.The influence of pH, the structure of the phase-transfer catalyst, the nature of the organic phase and the use of the supernucleophile HO2- on the hydrolysis was investigated.The hydrolysis of 1 is accelerated by a factor of ca. 550 (toluene) resp. ca. 520 (tetrachloroethylene) compared with the uncatalysed reaction.In concrete terms, the compound 1 can be completely hydrolysed in three (tuloene) resp. in one minute (tetrachloroethylene) under optimal conditions.
- Horner, Leopold,Kappa, H. Wilfried
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p. 339 - 348
(2007/10/02)
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