Hexadecyltrimethylammonium silicate

Synthesis of organized mesoporous aluminas is based on the same approaches as those successfully used for the synthesis of mesoporous molecular sieves ( anionic , cationic , and neutral ) using aluminum alkoxide as the source of aluminum and in the absence of any silicon source. In contrast to the synthesis of siliceous MCM-41, the cationic route to organized mesoporous aluminas using hexadecyltrimethylammonium cations is the least applied and understood. Cabrera et al. [68] described the possibility to tailor the pore dimensions from 3.3 to 6.0 nm by modifying the ratio of surfactant, water and triethanolamine however, this synthesis route seems to be less reproducible compared with anionic and neutral routes. 

An example of ion exchange with complex cations is the adsorption of hexammine cobalt(in) cations [CoCNHslg] in kanemite [130]. The amount exchanged increases in the presence of hexadecyltrimethylammonium ions but still remains below the cation exchange capacity. Ion exchange reactions of [Pt(NH3)4] + ions with the crystalline silicic acid from Iler s octosilicate, aftCT calcination, provides a novel method for preparing silica-supported Pt nanoparticles of 2 to 5-nm diameter [131]. 

The first experiments on the exchange of interlayCT sodium ions by other inorganic cations (Li+, Na, Mg, Ni, Cu ) and hexadecyltrimethylammonium ions were reported by Her [12] for the 8 1 type of polysilicate (8Si02/Na20). The exchange of the interlayer cations is less pronounced and does not comprise the diversity of reactions reported for 2 1 clay minerals, in particular, smectites. Typical is the exchange by protons and transformation into crystalline silicic acids, which will be discussed in Section IV.C. 

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