混合稀电解质条件下合成球状SBA-15粒子

在酸性合成法基础上, 不添加有机共溶剂和其它模板剂, 通过加入少量NH4F和Cu(NO3)2得到了分散的球状形貌SBA-15粒子. 对所得样品用小角X射线衍射(XRD)、N2吸脱附曲线、扫描电镜(SEM)进行表征, 讨论了不同电解质对样品形貌和孔结构的影响. 结果发现, 随着酸浓度增加, 得到了分散的规则六边形SBA-15粒子, 而加入一定量的氟化铵则得到了球形纠结状形貌的SBA-15. 实验表明, 氟离子在形成球状粒子的过程中起主要作用, 而Cu2+阻碍了球状粒子的纠结. 随着Cu2+浓度的增加, 部分硅源不能参与自组装生成SBA-15, 其原因可能是Cu2+与模板剂中亲水的聚氧乙烯形成PEO/Cu2+端基, 影响了硅源正常的缩聚.

Synthesis of Spherical SBA-15 Particles under Mixed and Dilute Electrolyte Conditions

Spherical SBA-15 particles were synthesized by co-addition of dilute but strong electrolytes (NH4F and Cu(NO3)2) under classical acidic conditions without an organic solvent or another template. These materials were characterized by low angle X-ray diffraction (XRD), N2 sorption isotherms, and scanning electron microscopy (SEM). Separated uniform hexagonal SBA-15 particles form in strong acidic media while an appropriate content of fluoride anions favors the synthesis of a sphere-like and highly pored ordered structure. Effects of different electrolytes on the morphology and the mesostructure of the resulting materials were discussed. We found that fluoride played the main role in the formation of sphere-like SBA-15 while the presence of the Cu2+ was beneficial for the formation of separated spherical SBA-15 particles. When the concentration of Cu2+ increases, a part of the silica does not contribute to the formation of SBA-15. This phenomenon is probably due to the formation of a PEO (polyoxyethylene)/Cu2+ head-group at the hybrid interface which affects the normal coordination and condensation of the silica source.