摘要
采用溶胶-凝胶法制备Al2O3含量为30%的SiO2-Al2O3复合氧化物,借助热重-差热分析(TG-DTA)、N2物理吸附、X射线粉末衍射(XRD)、傅里叶变换红外(FTIR)、氨程序升温脱附(NH3-TPD)以及吡啶吸附红外(Py-IR)光谱研究了500～900℃范围的热处理过程对SiO2-Al2O3结构、织构、酸性质的影响规律,并与四氢呋喃(THF)聚合性能进行关联.结果表明,经500℃热处理的SiO2-Al2O3拥有高的比表面积、大量的Si—O—Al键以及丰富的酸性中心.随着热处理温度升至700℃,SiO2-Al2O3的织构性质无显著变化,Si—O—Al键数量减少,SiO2-Al2O3总酸量和酸密度下降,强酸中心消失.至900℃时,比表面积和孔体积急剧下降,平均孔径显著增加,酸量和酸密度进一步减少.聚合反应结果表明,产品的收率和分子量均随热处理温度的升高呈现上升趋势.900℃时,产品收率最高,可达47%,聚合物分子量(Mn)为1710.
SiO2-Al2O3 with 30% Al2O3 content has been synthesized via sol-gel procedures. The evolution of their surface properties during the heat treatment process from 500 -900 ℃ has been characterized by Thermal gravity- Differential thermal analysis （TG-DTA）, N2 adsorption, X-ray diffraction （XRD）, Fourier transform infrared （FT- IR） spectroscopy, FTIR spectroscopy of adsorbed Pyridine （Py-IR） , and temperature programmed desorption of N H3 （NH3-TPD）. The catalytic performances were examined for the polymerization of tetrahydrofuran （THF）. The experimental results indicated that high specific surface area, numerous Si--O--Al bonds and abundant acid sites were obtained at 500 ℃. As the temperature of heat treatment increased to 700 ℃, the textural parameters of SiO2- A1203 did not exhibit obvious change, while the amount of Si--O--Al bonds, total acid sites and acid density decreased. The strong acid sites became absent at this temperature. At 900 ℃, the specific surface area and pore volume decreased sharply and the pore size increased significantly. The amount of Si--O--Al bonds, total acid sites and acid density further decreased. The evaluation results showed that the yield and molecular weight （Mn） of the polytetrahydrofuran （PTHF） increased as the temperature increased. At 900 ℃, SiO2-Al2O3 displayed the highest acidity （47%） and the largest Mn （1710）.
出处
《分子催化》
EI
CAS
CSCD
北大核心
2013年第2期166-172,共7页
Journal of Molecular Catalysis(China)
基金
山西省科技重大专项(20111101010)
