高硅Y沸石“二次孔”结构的物理吸附法研究

用低温氮物理吸附法研究了化学法和水热法相结合制备的两个系列Y沸石的孔结构性质。研究结果表明, 用不同化学试剂处理Y沸石形成的孔结构有明显差别。但是, 当把由此得到的Y沸石在相同条件下交替进行水热处理和化学处理时, 孔结构却呈现类似的变化趋势, 即总比表面积、微孔比表面积和微孔体积是先下降后上升, 经第二次水热和化学处理是再次下降再次回升。而过程中产生的“二次孔”比表面积却呈现先上升后下降, 又回升又下降的相反的变化趋势。这种变化趋势, 可能与水热处理和化学处理过程中非骨架铝物种的形成与消失有关。

THE STUDIES OF PORE STRUCTURES OF HIGH-SILICA Y ZEOLITES BY N_2 ADSORPTION

The properties of pore structure of high-silica Y zeolites prepared by combinedhydrothermal-chemical treatments have been characterized by measuring N_2 adsorption-desorption isotherms at 77.4K. The surface area and micropore volume for the sam-ples have been calculated by means of t-method and MP method. It has been foundthat two zeolites Y samples dealuminated by different chemical agents have apparentdifferences in their pore structures.But,when these two samples are further submittedto hydrothermal treatments combined chemical treatments, an evolution with similartendencies in pore structure has been observed, namely, their total surface area, thesurface area of micropores and micropore volume have reduced after hydrothermaltreatments and increased after chemical treatments. On the contrary, the surface areaof the secondary pore systems has been increased after hydrothermal treatments andreduced after chemical treatments. This evolution of pore structure may be related tothe formation and elimination of non-framework aluminium species.