晶化时间、模板剂对Si-MCM-41结构的影响

以有机硅为硅源,采用碱性水热合成制备Si-MCM-41,借助XRD,N2吸附-脱附表征手段系统研究晶化时间、模板剂对其长程有序结构的影响.结果表明:晶化过程中必须调节体系的pH,样品的六方晶相才会随晶化时间的增长而不断地生长和完善.长时间的晶化有利于孔壁增厚,对于提高Si-MCM-41的稳定性是有利的,但同时比表面积呈现下降趋势.综合考虑六方有序结构的生长和完善以及孔壁的厚度、比表面积等因素,确定晶化时间为120 h.增加模板剂(template)浓度会促进Si-MCM-41孔结构形成和排列的规整性,当模板剂为c(template)/c(SiO2)=0.7,六方有序度下降,适宜的c(template)/c(SiO2)应为0.5.

Effects of crystallization time and template agent on the structure Si-MCM-41

With organic silica being used as silicon source,Si-MCM-41 is thermally synthesized by using base water,.The effects of crystallization time and template agent on the mesoporous structure of it are studied by means of N_2 adsorption-desorption isotherm analysis and XRD measurement,the results show the pH of the reaction system must be adjusted during crystallization so that the hexagonal phase can grow and become more regular with the increase of crystallization time.Long crystallization time can benefit the enhancement of pore wall thickness,which is advantageous to the stability of Si-MCM-41 structure.However,the specific surface area of Si-MCM-41 decreases.After the growth and perfection of hexagonal,the wall thickness of pore and the specific surface area are comprehensively considered,a suitable crystallization time is determined as 120 h.The formation of pore structure and the regulation of the pore arrangement of Si-MCM-41 can be promoted by means of increasing the concentration of the template agent.When the mass ratio of template agent to SiO_2 is 0.7,the regular level of the hexagonal begins to decrease.A suitable mass ratio of template agent to SiO_2 is determined as 0.5.