以短链季铵盐/脂肪酸盐为模板合成超微孔二氧化硅

超微孔材料具有1～2 nm的孔径,在分离、催化应用中有望展现出择形催化的能力。寻找经济、简便的合成超微孔材料的表面活性剂体系是一项有意义的工作。本研究以短链季铵盐(十烷基三甲基溴化铵,记为C₁₀TAB)和不同链长脂肪酸酸盐混合胶束为模板剂,硅酸钠为硅源,成功制备出高度有序超微孔SiO_2。通过小角X射线衍射、N_2吸附-脱附、傅里叶变换红外光谱、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等技术手段对产品的结构和性能进行了表征。结果表明,合成体系中脂肪酸盐碳链长、加入量、晶化温度等对产物孔道有序性有很大影响。当选择正辛酸钠(SO)为助表面活性剂,当n(C₁₀TAB)∶n(Na_2SiO_3)∶n(SO)∶n(H_2O)=1∶1.5∶0.3∶800,晶化温度为80℃时,可以得到高度有序超微孔SiO_2。煅烧后样品比表面积为1300 m^2/g,孔体积0.49 cm^3/g,孔径分布在1.90 nm。

Synthesis of Ordered Supermicroporous Silica Using Short-Chain Quaternary Ammonium/Fatty Acid Salts as Template

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.