Abstract:

Supermicroporous materials possess pore size of 1~2 nm. They are expected to exhibit size- and shape-based separation/catalytic applications, which plays important role in modern industry. It is challenging to find an economic/simple surfactant system for the synthesis of supermicroporous materials. In this work, supermicroporous silica was synthesized using short-chain quaternary ammonium salt(decyltrimethyl ammonium bromide, denoted C₁₀TAB) surfactant system mixed with fatty acid salts as the templating agents. The samples were characterized by small-angle X-ray diffraction(XRD), N₂ adsorption-desorption, Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The results indicate that the length of alkyl chain in co-surfactant, the dosage amount, crystallization temperature have great effects on the regularity of the pore structure. We can obtain highly ordered supermicroporous silica when using sodium octanoate(denoted SO) as co-surfactant in the molar ratio of n(C₁₀TAB):n(Na₂SiO₃):n(SO):n(H₂O)=1:1.5:0.3:800, at the crystallization temperature of 80 ℃. The calcinated materials possess surface area 1300 m²/g and pore volume 0.49 cm³/g with a pore size distribution centered at about 1.90 nm.

Key words: supermicroporous silcia, short-chain quaternary ammonium salt, fatty acid salts, micellar, mixed surfactants system