Cetyltrimethylammonium bromide silicates

The surfactant, cetyltrimethylammonium bromide, was dissolved in water to obtain a clear solution, in which the first swelling agent (decane) was then added drop by drop with stirring. After ten minutes stirring at room temperature, the second swelling agent (TMB) was introduced. Sodium silicate was added to the obtained micellar solution and the pH value was adjusted with sulfuric acid. The pH value and surfactant/silicium molar ratio was fixed at 10 and 0.62 according to the protocol established previously for conventional MCM-41 synthesis... 

Organically modified porous silicates have been prepared under acidic conditions, by direct reaction of a mixture of phenyltriethoxysilane (PTES) and tetraethoxysilane (TEOS), and an aqueous solution of cetyltrimethylammonium bromide (CTAB). For a 1 4 molar ratio between PTES and TEOS, the hexagonal (2d, p6m) phase, but also a cubic phase analogous to the already reported SBA-1 phase (Pm3n), can be prepared. The surfactant can then be efficiently removed by calcination at 350°C, leading to phenyl-functionalized microporous silicates with two types of architecture. The influence of several parameters (PTES/TEOS ratio ethanol content) that affect the organization of the samples, will be discussed. 

Following the investigations of Schiith, Stucky and Unger and their co-workers, various procedures have been proposed for the preparation of M41S and other related materials. For example, Edler and White (1995) have described a method for the low-temperature synthesis of a pure silica form of MCM-41. An essential stage in their preparative route was the controlled ageing of the mixed solution of sodium silicate and cetyltrimethylammonium bromide (CTAB) before the intermediate product was filtered, washed, dried and finally calcined in air at 350°C. Comparison with standard hydrother-mally produced material revealed no significant difference in the adsorption properties. 

Phenyl functionalized silicates with cubic Pm3n and 2D p6m symmetries have been prepared by direct reaction of a mixture of phenyltriethoxysilane and tetraethoxysilane with an aqueous solution of cetyltrimethylammonium bromide, under acidic or basic conditions. Their structural characterization by XRD using synchrotron radiation, multinuclear MAS-NMR (including 2-dimensional H homonuclear correlation) and N2 adsorption-desorption isotherms will be reported in order to better describe the localization of the phenyl groups in the silicate framework. 

The influence of alkali/silica molar ratio in the synthesis of mesoporous molecular sieve materials was studied in a simple synthesis system containing tetraethylorthosilicate, water, alkali and the cetyltrimethylammonium bromide at room temperature. The resulting silicate materials were characterized by XRD, Si MAS NMR, TEM and N2 adsorption-desorption isotherms. The results suggest that the formation of different surfactant-silicate aggregation array morphology not only relies on an interaction between silicate ions and the surfactant, but also on a proportion of the silicate species to surfactant. 

A more practical precipitated silica of lower surface area that can be dried from water, yet retains an open structure with easy dispersibility, is described in detail in another patent to Alexander et al. (271). The main difference from the above is that the initial sol was made in a more concentrated solution 123 part of sodium silicate solution containing 3.71 grams SiOj per 100 cm was heated to 90 C, and 10.1 parts 13% H2SO4 solution was added in 30 min. Then added simultaneously over a 2 hr period were 119 parts of sodium silicate solution containing 8 grams SiOj per 100 cm and 111 parts 3.11% H3SO4 solution. At the end of the reaction more acid was added to reduce the pH to 7. To the product slurry, 3 parts of 1% cetyltrimethylammonium bromide solution was added to aid filtration. The recovered wet silica was washed to remove salt, the pH adjusted to 8, and the silica dried at 110 C. This... 

Similarly, chiral Cp Rh-TsDPEN was incorporated within flower-like mesoporous silica through the assembling of chiral 4-((trimethoxysilyl)ethyl)phenylsul-fonyl-l,2-diphenylethylenediamine (133) and Si(OEt)4 under a cooperative dualtemplate approach followed by complexation with the Rh complex in the presence of surfactant cetyltrimethylammonium bromide [112]. The obtained bifunction-alised sohd catalyst showed excellent catalytic efficiency in the ATH of aromatic ketones in aqueous medium. The residual surfactant within the silicate network acted as a phase transfer catalyst thus enhancing the catalytic activity, while well-... 

Synthesis of MCM-41 with Additives. The hydrothermal crystallization procedure as described earlier [10] was modified by adding additional salts like tetraalkylammonium (TAA+) bromide or alkali bromides to the synthesis gel [11]. Sodium silicate solution ( 14% NaOH, 27% Si02) was used as the silicon source. Cetyltrimethylammonium (CTA) bromide was used as the surfactant (Cl6). Other surfactants like octadecylltrimethylammonium (ODA) bromide (C,8), myristyltrimethylammonium (MTA) bromide (C,4) were also used to get MCM-41 structures with different pore diameter. Different tetralkylammonium or alkali halide salts were dissolved in little water and added to the gel before addition of the silica source. The final gel mixture was stirred for 2 h at room temperature and then transferred into polypropylene bottles and statically heated at 100°C for 4 days under autogeneous pressure. The final solid material obtained was washed with plenty of water, dried and calcined (heating rate l°C/min) at 560°C for 6 h. 

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