酸性条件下纯硅六方介孔分子筛的合成(Ⅱ)合成温度、时间的影响及其与碱性合成的比较

Synthesis of Hexagonal Mesoporous Silica in Acidic Medium (Ⅱ) Effect of Synthetic Temperature and Time, and a Comparison with the Synthesis in Basic Medium

本文以十六烷基三甲基溴化铵为模板剂，正硅酸乙酯为硅源，考察了反应温度和时间对酸性条件下合成纯硅六方介孔分子筛的影响，并与碱性合成路径相比较。结果表明，由于无机物种与表面活性剂之间的相互作用不同，六方介孔分子筛的酸性合成经历了与碱性合成完全不同的机理。对酸性合成来说，由于六方结构的形成取决于稳定的模板胶束的存在，并不特别依赖于硅物种的缩合，故高温、长反应时间等有利于缩合的因素对提高产品质量几乎没有促进作用，较高的反应温度甚至起反作用。因此，酸性合成宜采用室温条件。

Hexagonal mesoporous silica were synthesized in acid medium by using cetyltrimethylammonium bromide (C16TMABr) as template and tetramethyl orthoslicate (TEOS) as silica source. The effect of synthetic temperature and time were investigated. The results were further compared with the synthesis in base medium. It is shown that the mechanism for acid synthesis of hexagonal mesoporous silica is different from that for base synthesis since different interaction occurs between inorganic species and surfactants in these two routes. For the acid synthesis, the formation of hexagonal structure depends on the existence of stable surfactant micelle other than the condensation of silica species, thus, the factors favorable to the condensation, such as high temperature and long reaction time, are not able to improve the quality of the samples. High temperature is even an adverse condition. Therefore, the acid synthesis should be performed at room temperature.