Syntheses with non-ionic surfactants

08-0-01 - Mesoporous MSU-X silica tuned for filtration and chromatography applications 

Institut Europeen des Membranes, L.M.P.M. (CNRS UMR 5635) C.N.R.S., 1919 Route de Mendes, F-34293 Montpellier cedex 5, FRANCE, e-mail prouzet iemm.univ-montp2.fr 

Mesoporous MSU-X silica was synthesized with a two-step pathway, that allowed us to get a high control degree on both the final material shape and the porous size distribution. These materials were developed and tested for separating applications, including HPLC chromatography and ultrafiltration membranes. Both applications show that the specific structure of the Micellar Templated Structures exhibits a new behavior in the separation applications, compared with other materials. They are explained by the combined effect of the silica nature and the specific cylindar pore shape. 

08-0-02 - Highly ordered tnesoporous silicas synthesis using deca-(oxyethylene) oleylether as surfactant variation of the weight percentage of surfactant and incorporation of transition metal cations 

Laboratoire de Chimie des Maleriaux Irtorganiques, Universite de Namur, Belgium 

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In this study, it is foimd that the effects of (CH3CH2)3N on the formation of mesopore structures and the effects of the PEG on the thermal stability of the precipitated powders are very interesting. The results show that the Ce02 powders prepared by the precipitation method are mesoporous with crystalline walls. The mesoporous structure can be maintained upon calcination up to 873K. The mesoporous Ce02 synthesized from the system in the presence of non-ionic surfactant PEG exhibits better thermal stability than that prepared using one template of (CH3CH2)3N only. 

Various mesoporous silica materials were synthesized using a non-ionic surfactant as template in the presence of different platinum salts in the synthetic gel. The salts were found to influence the structure and porosity of the solids obtained. Thus, our results show that platinum salts promote the hydrolysis of tetraethylorthosilicate (TEOS) and the presence of (NH4)2PtCl4 or H2PtCl6 leads to the formation of materials with smaller pore sizes and less condensed than those obtained in the absence of platinum salts or in the presence of (NH3)4PtCl2. 

Mesoporous TiOa has been synthesized in the presence of a non-ionic surfactant by assembly, using a Ti alkoxide as Ti source. The porous structure partially collapses upon calcination. However, this fact can be avoided by extraction of the surfactant with boiling acid/ethanol mixtures. Thus, TiOa samples with surfaces areas up to 470 m /g and pore sizes in the range 2-6 nm have been obtained. DR UV-Vis spectra of the as-synthesized samples show the presence of Ti species with both tetrahedral and octahedral coordinations, which resemble that of anatase powder. 

In general, electrostatic stabilization leads to smaller and more uniform particle size when compared with syntheses involving similar amounts of steric stabilizers. An advantage of non-ionic surfactants over electrostatic stabilization is improved humidity resistance (42). A given class of stabilizer can provide both electrostatic and steric stabilization depending on the length of the steric moieties in the surfactant molecule (43). 

The mesoporous template is synthesized in a two-step pathway using tetraethyl orthosilicate as the silica source and non-ionic surfactants following the procedure described by Boissiere et al. [16]. As a surfactant, non ionic poly(ethylene oxide) -PEO- surfactant To gitol IS-S-N was selected. Briefly, the silica source is added under stirring to the solution of the surfactant and the pH is adjusted at around 2 with HO. The solution is kept in a closed vessel for 18 h without stirring at room temperature. Then, a small amount of NaF is added to promote silica condensation. The mixture is aged for 3 days at two temperatures, 293 K and 333 K. The white precipitate obtained is filtrated, dried and calcined at 873 K. The samples arc referred to as T30 and T60, respectively. 

Various V-substituted 6-amino-6-deoxy-D-glucose derivatives, e.g. 6-8, were synthesized by reaction of the corresponding 5,6-anhydro-D-glucose derivative with secondary amines, and shown to be useful as non-ionic surfactants capable of forming reverse micelles for solubilization of amino acids in hexane. Reaction of such tertiary amines with methyl iodide provided quaternary ammonium-sugar derivatives. The 6-amino-2,5-anhydro-6-deoxy-D-gluconate derivative 10, a potential dipeptide isostere, was obtained from the C2-symmetric, D-mannitol derived bis-epoxide 9 following silica-assisted azidolysis (Scheme 3). Its enantiomer was obtained similarly from an L-iditol bis-epoxide. ... 

A variety of aluminate spinels MAI2O4 (M = Co, Ni, Cu) have been synthesized by Meyer etal. [319] via microemulsions. Non-ionic, nonylphenol-poly[(n)glycol ether] type surfactants (n = 7, 10, 15), i.e. the Tergitol series TNP-7, TNP-10 and TNP-35 were used with octan-l-ol as a co-surfactant. The oil phase was cyclohexane or n-heptane, while the aqueous phase was pure water. The individual microemulsions produced out of the above constituents were added dropwise under dry nitrogen atmosphere to isopropyl or tert-butyl alcohol solutions of the relevant heterobimetallic alkoxides to effect precipitation through hydrolysis. 

Little information is available on microemulsion-mediated synthesis of rhodium particles. Considering the importance of Rh nanoparticles in catalytic reactions, Kishida et al [426] developed a method using microemulsions. The reverse micelle was prepared with the surfactant NP-5 and cyclohexane as the continuous phase. An aqueous solution of rhodium chloride was solubilized in the micelle and hydrazine directly added to it at 25°C. The average particle size of rhodium thus obtained was about 3 nm. Kishida et al. [427] later extended the method to the use of a variety of non-ionic and ionic surfactants (C-15, i.e. polyoxyethylene(15)cetyl ether, L-23, i.e. polyoxyethylene(23)lauryl ether, NP-5 and NaAOT), as also cyclohexane or 1-hexanol (according to necessity) as the continuous phase. The reactants remained the same, i.e. rhodium chloride and hydrazine hydrate. In addition, the rhodium particles thus synthesized were coated with silica via hydrolysis-polycondensation of tetraethyl orthosilicate. The size of Rh varied in the range 1.5-4.0 nm in a typical case, a 4 nm particle was covered with a 14 nm thick layer of silica. 

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