由硅铝酸盐前驱物水热合成介孔分子筛SAN-01及其孔道结构的表征

Synthesis and Pore Structural Characterization of Mesoporous Molecular Sieves SAN-01

以微斜长石制备的硅铝酸盐前驱物为主要原料,以13X沸石晶核剂为孔壁结构导向剂,水热合成了含有13X沸石基本结构单元的硅铝酸盐介孔分子筛SAN-01。在该方法中,首先微斜长石与Na2CO3按物质的量比为1:1.05的比例混合后,在820℃下焙烧2h。焙烧物料室温下在0.01mol/L的NaOH水溶液陈化24h后,与50mL的十六烷基三甲基溴化铵(C16TMABr)水溶液(含7.4gC16TMABr)混合、再经105℃下晶化48h、过滤、水洗和焙烧等工艺,合成了硅铝酸盐介孔分子筛。当假定孔结构为球形散射体时,小角散射(small-angleX-rayscattering,SAXS)给出的样品平均壁间距的统计平均值为5.42nm,比XRD给出的结果偏大8.8%。SAXS给出的SAN-01的壁间距分布介于0.2～11.3nm之间,N2吸附与XRD联合给出的壁间距分布介于3.8～4.9nm之间,即SAXS给出的壁间距分布范围较N2吸附与XRD联合给出的壁间距分布范围宽。该差别可能源于样品中存在的部分闭孔结构,或N2分子与分子筛表面的不饱和羟基之间的分子间力。

Mesoporous molecular sieves, named SAN-01, were hydrothermally synthesized with microcline, a natural ore, as starting material, and the seeds of 13X zeolite as pore-wall＇s crystal source. During the process, the mixture of microcline and Na2 CO3 with a molar ratio of 1 ： 1.05 was first calcined at 820℃ for 2h; the calcined materials were then dissolved in 0.01mol/L NaOH aqueous solution and aged for 24h at room temperature; the as-prepared Si, Al sources and 50mL cetyhrimethylammonium bromide （C16TMABr） aqueous solution （containing 7.4g C16TMABr） were mixed, crystallized at 105℃ for 48h, centrifuged and washed 3 times with water. The powder was calcined at 550℃ for 10h, resulting in mesoporous molecular sieves. When pores in SAN-01 were supposed to be spheroid, the mean porewall distance of SAN-01 calculated by SAXS （small-angle X-ray scattering） is about 5.42nm; which is bigger than that determined by XRD about 8.8%. The pore-wall distance distribution determined by SAXS （0.2-11.3nm） is wider than that by N2 adsorption and XRD （3.8-5.6nm）. The difference above mentioned maybe caused by closed porous structure, or the force between N2 molecules and OH groups on the pore-surface. SAXS can also be used to characterize the pore structure of samples with template, but N2 adsorption cannot be used to do so.