摘要
Adsorption rates of n-hexane on the 5A zeolite at 100 to 300 ℃ and 0.01 to 10 kPa are determined by an intelligent gravimetric analyzer （IGA-100）, and the adsorption diffusion performance of n-hexane on 5A zeolite pellets with different secondary pore distributions is analyzed. The results indicate that 5A-1 and 5A-6 zeolites have similar micropore and mesopore size distribution, while the 5A-6 zeolite has a larger secondary pore volume when the pore diameter is between 0.1 and 1 μm and more secondary pores when the pore diameter is less than 0.01 μm. The effective diffusion coefficient of nhexane on the 5A-6 zeolite pellet is 10 ^-6 to 10 4 cm^2/s, about 2 to 5 times higher than that on the 5A-1 zeolite. The effective diffusion coefficient of n-hexane on the 5A-1 zeolite pellet improves from 5 × 10^-7 to 2 × 10 6cm^2/s when the temperature increases from 100 to 300 ~C. However, the effective diffusion coefficient of n-hexane on the 5A-6 zeolite remains almost unchanged at different temperatures. The molecular average free path of n-hexane decreases from 627.15-963.28 to 0.63-0, 96 Ixm with the adsorption pressure increasing from 0.01 to 10 kPa. Such a flee path is close to the secondary pore diameter, resulting in significant Knudsen diffusion in the secondary pores. Thus, the effective diffusion coefficient of n-hexane on the 5A zeolite pellets increases before 1 kPa and decreases after 1 kPa.
采用IGA-100型智能重力分析仪测定在100～300℃,0.01～10kPa下,5A分子筛对正己烷的吸附速率曲线,分析了不同二次孔分布的成型5A分子筛颗粒5A-1和5A-6对正己烷的吸附扩散性能.结果表明:5A-1与5A-6分子筛具有相近的微孔和中孔孔径分布;5A-6分子筛在孔径0.1～1μm范围内拥有相对更大的二次孔孔容,而在孔径小于0.01μm时拥有更丰富的二次孔分布;丰富的二次孔分布使得正己烷在5A-6分子筛上的有效扩散系数De为10-6～10-4cm2/s,是5A-1分子筛的2～5倍;随着吸附温度从100℃增大至300℃,5A-1分子筛上的有效扩散系数从5×10-7～2×10-6cm2/s增大至2×10-5cm2/s,而在5A-6分子筛上的有效扩散系数随着吸附温度变化不明显;吸附压力从0.01kPa升高至10kPa,引起正己烷分子平均自由程从627.15～963.28μm下降至0.63～0.96μm,并与分子筛二次孔孔径相当,引起Knudsen扩散加剧,从而使正己烷在5A分子筛上的有效扩散系数于压力1kPa前后呈现先上升后下降的变化趋势.
基金
The National Natural Science Foundation of China ( No.20876074)
