硅溶胶胶凝过程的分形特征  

FRACTAL OF SILICA SOL DURING SOL-GEL PROCESS

作　　者：杨丽静[1] 田辉平[1] 龙军[1] 李志宏[2] 

机构地区：[1]中国石化石油化工科学研究院,北京100083 [2]中国科学院高能物理研究所同步辐射实验室,北京100039

出　　处：《石油学报（石油加工）》2010年第6期841-845,共5页Acta Petrolei Sinica(Petroleum Processing Section)

基　　金：国家重点基础研究发展计划项目(2010CB732301)资助

摘　　要：硅基黏结剂的催化裂化催化剂可以提高汽油选择性、降低生焦产率,然而硅溶胶的不稳定性限制了其应用。硅溶胶的pH值是对其稳定性影响最大的因素。分形理论可以推测胶体粒子的生长、聚集机理。应用同步辐射小角X光散射考察了pH值对硅溶胶胶凝过程分形特征的影响。结果表明,酸性硅溶胶和碱性硅溶胶均对Porod定律形成负偏离,属于非理想两相体系。酸性硅溶胶在整个胶凝过程中都为1种结构的表面分形,聚集过程为反应控制的集团-集团聚集。而碱性硅溶胶中存在2种不同结构的表面分形,其中簇团聚集过程为反应控制的集团-集团聚集,初级粒子的形成则由扩散控制转为反应控制。FCC catalysts with silica sol binder can enhance the selectivity to gasoline and reduce coke yield in FCC,yet the unstability of silica sols is a bottleneck of its utilization,which may be caused by the pH value of silica sol itself.Small angle X-ray scattering（SAXS） technique with synchrotron radiation was used to study fractal structures of silica sols with different pH value.The results indicated that both the acidic and alkaline silica sols presented negative deviation from Porod＇s law.Only one kind of surface fractal could be found in the acidic silica sol and the aggregation process belonged to reaction-limited colloidal aggregation（RLCA）.Whereas,in the beginning,two kinds of surface fractal could be seen in the alkaline silica sol and one of them evolved to either pore fractal or mass fractal before gelation with the other remained surface fractal.

关 键 词：硅溶胶 分形 小角X射线散射 

分 类 号：TQ039[化学工程]