无机盐的加入对纯硅MCM-41中孔材料合成和稳定性的影响

考察了在水热条件下合成纯硅MCM-41中孔分子筛时，加入NH4Cl、NaCl和NaF对其合成及稳定性的影响。采用XRD、低温N2吸附等手段表征了合成所得样品。结果表明，采用加入无机盐的方法可调节MCM-41的孔径大小；也可导致合成产物中间相发生变化。无机盐的加入可有效地提高所合成样品XRD的特征衍射峰（100）强度和稳定性，且以NH4Cl的加入最为明显。随着NH4Cl加入量的增加，合成产物的物相由一维六方有序结构MCM-41向三维似螺旋结构KIT-1过渡。当NH4Cl与表面活性剂的摩尔比为0．2时，在130℃下水热晶化96h，能制得稳定性好的中孔材料MCM-41，可在沸水中稳定保持2h以上．而不造成孔道结构的明显变化。

EFFECT OF INORGANIC SALT ADDITION ON PORE STRUCTURE AND STABILITY OF MESOPOROUS SILICA MCM-41

MCM-41 Mesoporous silica molecular sieves were hydrothermally synthesized. The influences of inorganic salt NH_4Cl, NaCl and NaF added to the synthesis system on the crystallization and hydrothermal stability of mesoporous materials were investigated. The pore structure characterization by X-ray diffraction and low temperature nitrogen adsorption indicated that the inorganic salt addition could be used to adjust the pore diameter of MCM-41, and could result in the transformation of mesophase, which is directly depended on the concentration and nature of salt added. Addition of a suitable amount salt can enhance the diffraction peak (100) intensity of XRD and the stability of mesoporous silica notably. Among the three kinds of salts, the effect of NH_4Cl was the most outstanding. When added with NH_4Cl, the mesoporous materials experienced phase transformations in the sequence (MCM-41)KIT-1 as the molar ratio of NH_4Cl/surfactant increased. When the molar ratio NH_4Cl/surfactant was (0.2), mesoporous MCM-41 with high ordered pores and stability could be prepared by ctystallization at 130 for 96 h, and the MCM-41 maintained the mesoporous structure after hydrothermal treatment at 100 for at least 2 h in a close bottle without obvious changes in pore structure.