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用Micromeritics ASAP 2400仪对多种沸石分子筛材料进行了低温氮吸附等温线的测定。通过BJH法和MP法的孔分布计算表明,可以用2.0nm(BJH法)或1.5nm(MP法)作为区分沸石晶体骨架结构中的微孔和次级孔的孔径界限值。对四种具有相近晶粒外形尺寸的Y型沸石样品的测定和MP法的计算表明,它们在1.6～2.4nm范围内分别有0.0035,0.0381,0.101和0.184mL/g次级孔,这种显著差别说明沸石中存在着晶粒内次级孔。在沸石晶体骨架结构微孔中的内扩散起控制作用的场合,可采用与球形颗粒比表面积相当的晶粒当量直径来反映晶内扩散时从中心到边缘的平均距离。上述四种样品的晶粒当量直径分别为0.66,0.085,0.037和0.023μm。
A variety of zeolitic molecular sieve materials were subjected to a low-temperature nitrogen adsorption isotherm using a Micromeritics ASAP 2400 instrument. The pore distribution calculation by BJH method and MP method shows that 2.0 nm (BJH method) or 1.5 nm (MP method) can be used as the aperture limit for distinguishing the micropores and the secondary pores in the zeolite crystal framework structure. The determination of the four Y zeolite samples with similar grain size and the calculation of the MP method show that they have 0.0035, 0.0381, 0.101 and 0.184 mL / g secondary pores in the range of 1.6 to 2.4 nm, respectively, which is significant The difference indicates that there are intragranular secondary pores in the zeolite. Where the internal diffusion in the pores of the zeolite crystal framework plays a controlling role, the equivalent diameter of the grains corresponding to the specific surface area of the spherical particles can be used to reflect the average distance from the center to the edge of the crystal when it diffuses. The grain equivalent diameters of the above four samples were 0.66, 0.085, 0.037 and 0.023 μm, respectively.