利用粉煤灰制备活性SiO_2工艺研究

以粉煤灰为硅源制备高比表面积的活性SiO2。根据所用高铝粉煤灰的化学与物相组成的特点,确立了利用NaOH溶液提取非晶态硅的工艺路线,并利用正交试验法确定了提取非晶态SiO2最佳工艺条件:NaOH浓度8 mol/L,灰碱质量比2∶1,反应温度95℃,反应时间6 h。然后采用CO2气体沉淀法制备高比表面积的SiO2,该法制备的活性SiO2比表面积可达730 m2/g。较理想的碳分条件为硅质量浓度30 g/L,温度30℃,该条件下通入CO2气体制备出的活性SiO2比表面积大,孔分布窄且均匀,性能稳定。

Preparation of active SiO2 from fly ash

The active SiO2 with high specific surface was prepared with fly ash as the raw material.According to the chemical and mineralogical composition of the high-alumina fly ash,the extraction technical route of amorphous SiO2 with NaOH solution was determined.The optimum extraction conditions were determined by orthogonal experiments and necessary complementary experiments.The optimum conditions were as follows: concentrations of NaOH solution 8 mol/L;mass ratio of ash to alkali: 2∶1;reaction temperature 95 ℃,and reaction time 6 h.The SiO2 with high specific surface was prepared by precipitation method with CO2.The BET surface area of active SiO2 prepared by this method can reach 730 m2/g.Under the suitable condition of SiO2 mass concentration 30 g/L,temperature 30 ℃,the active SiO2 prepared has high specific surface,which is well-distributed and has stable performance.