聚烯烃催化剂硅胶载体的制备和表征

采用并流共沉淀法制备了适用于聚烯烃催化剂的硅胶载体,为减少颗粒的聚集,在制备过程中添加一种表面活性剂。利用透射电子显微镜(TEM)、比表面积测定(BET)和X射线粉末衍射(XRD)法对制备的硅胶载体进行了表征;考察了在制备硅胶载体过程中原料硅酸钠溶液的浓度、溶液pH以及焙烧温度对产物硅胶载体的物理性能的影响。实验结果表明,硅酸钠溶液的浓度影响硅胶的初始粒子的大小,溶液pH直接影响硅酸钠的水解速率,焙烧温度影响硅胶的孔结构和比表面积。当硅酸钠溶液的浓度为0．2mol／L、溶液pH为8-9、反应温度为70℃、焙烧温度为700℃时,硅胶载体的BET比表面积为242．22m2／g、最可几孔径为16．45 nm、堆密度为0．492 1g/mL,与进口硅胶(Silica Gel 955)的物理性能相近。

Synthesis and Characterization of Silica Gel Support for Polyolefin Catalyst

Silica gel support of catalyst used for polyolefin was synthesized by co-current flow coprecipitation and characterized by means of TEM,BET and XRD.A surfactant was used to abate grain aggregation of silica gel. Effects of preparation condition,namely concentration of sodium silicate, solution pH and calcination temperature,on physical properties of silica gel support were investigated. Initial grain size of silica gel,hydrolysis rate of sodium silicate,pore structure of silica gel and its specific surface area were affected by concentration of sodium silicate,solution pH and calcination temperature, correspondingly. Under following optimal preparation conditions:sodium silicate concentration 0.2 mol/L,reaction temperature 70 t,solution pH 8-9 and calcination temperature 700℃, physical properties of silica gel support were specific surface area 242.22 m2/g,most probable pore diameter 16.45 nm and bulk density 0.492 1 g/mL,which were similar to that of imported Silica Gel 955.