为了实现粉煤灰回收利用的新途径,研究了一种利用粉煤灰为硅源常压干燥合成SiO2气凝胶的工艺.通过正交实验研究粉煤灰与氢氧化钠反应生成水玻璃的最佳工艺条件;所得水玻璃溶液通过硫酸催化或树脂交换碱催化法获得水凝胶,利用三甲基氯硅烷/乙醇/正己烷对水凝胶进行改性处理,在常压干燥下制备了SiO2气凝胶.利用BET、SEM和FTIR对气凝胶的微观结构及性质进行了研究,结果表明,所得气凝胶的比表面积为362.2～907.9m2/g、孔体积为0.738～4.875cm3/g、平均孔径为7.69～24.09nm,其中树脂交换碱催化法所得气凝胶的比表面积可达907.9m2/g,孔体积达4.875cm3/g.
In order to achieve a new method of reclaimed use of fly ash,the present research aims to develop a synthesis process of SiO2 aerogel using fly ash as silica source via ambient pressure drying route.The best process conditions of the hydrothermal reaction of fly ash with sodium hydroxide for obtaining water glass are investigated by orthogonal experiment.The obtained water glass is treated using vitriol catalysis or resin exchange-alkali catalysis method to form SiO2 wet gel.The obtained wet gel is modified with trimethylchlorosilane/ethanol/hexane and dried under the ambient pressure,then silica aerogel is obtained.The microstructure and property of silica aerogels are analyzed by SEM,FTIR and BET.The results indicate that the specific surface area and pore volume of the synthesized silica aerogels are 362.2～907.9m2/g and 0.738～4.875cm3/g,respectively.The average pore diameter is 7.69～24.09nm.Especially,the specific surface area and pore volume of the silica aerogels synthesized by resin exchange-alkali catalysis method can attain to 907.9 m2/g and 4.875cm3/g,respectively.
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