表面活性剂对纳米MCM-41分子筛分散性的影响

Role of surfactant on dispersing nanospherical MCM-41 mesoporous molecular sieves

采用聚乙二醇为分散剂,十六烷基三甲基溴化铵为模板剂,正硅酸乙酯为硅源,在室温碱性条件下合成了粒径为40-60 nm的单分散纳米球形MCM-41分子筛.利用XRD、TEM和N2吸附脱附等手段研究了聚乙二醇用量对纳米球形MCM-41的分散性和介孔结构的影响.结果表明,表面活性剂PEG的加入,可以明显改善纳米颗粒的分散性并且对颗粒形貌影响不大;表面活性剂PEG的加入,样品的六方结构有序性和孔尺寸发生变化.PEG量在1％-20％范围内,样品仍具有较高的六方孔道有序性;PEG量过大(60％)有序性明显下降.随着PEG加入量的增加,纳米MCM-41的晶面间距增大,孔尺寸增大.适量的聚乙二醇可以得到有序性好、比表面积大、孔径均一和孔隙率大的单分散纳米球形MCM-41分子筛.

Using polyethylene glycol (PEG) as dispersant, cetyltrimethylammonium bromide (CTAB) as template and tetraethylorthosilicate (TEOS) as silica source, the monodispersing nanospherical MCM-41 mesoporous molecular sieves with the particle size of 40-60 nm were synthesized under basic media conditions. The influence of the PEG concentration on mesoporous structure and the dispersion of nanospheres were systemically studied. It showed that the morphology of particles changed little, but the dispersion of particles improved greatly. When PEG was added, the mesoporous structure of samples including hexagonal order and the pore size changed. The samples still show perfect long-range order of hexagonal mesoporous structures. With the increase of PEG concentration, the d100 values of samples in the XRD patterns enlarge. With the suitable PEG concentration, the monodispersing nanospherical MCM-41 mesoporous molecular sieves with uniform diameters, single-pore distribution, huge pore volume, huge surface area and high order mesoporous structure could be obtained.