碱处理对5A分子筛孔结构和氢吸附行为的影响

Effect of Alkaline Treatment on Pore Strcture and Hydrogen Absorption Behavior of 5A Molecular Sieves

采用SEM、EDS、BET和气相色谱等分析方法,研究了NaOH碱处理对5A分子筛显微形貌、成分、比表面积、孔容和氢吸附性能的影响。结果表明,NaOH碱处理降低了5A分子筛骨架中硅铝比,增大分子筛比表面积、孔容和平均孔径,提高了分子筛活化温度。在77K温度及100KPa压力下,碱处理5A分子筛对含0.1vol%H2/He混合气体吸附后尾气氢浓度小于1ppm,氢吸附容量为6.9ml/g。碱处理增加了5A分子筛介孔数量和比表面积及平均孔径,但因为孔径增大,吸附中心周围阳离子对H2分子的作用减弱,碱处理5A分子筛低分压氢吸附容量并无增加。

The effects of alkaline treatment on morphology,composition,specific surface area,pore volume and hydrogen adsorption property of 5A molecular sieve were analysed by SEM,EDS,BET and gas chromatography.The results show that the alkaline treatment decreases the ratio of Si/Al and increases the specific surface area,the pore volume and the average pore diameter of the 5A molecular sieve.The activation temperature of alkaline treated sample also increases.NaOH treated 5A molecular sieve could adsorb 0.1vol.% H2 from He purge gas effectively,the residual hydrogen is lower than 1ppm,at 77 K,100KPa,and the saturated hydrogen adsorption capacity is 6.9ml/g.This is because NaOH treatment introduces mesopores into the framework of the 5A molecular sieve.However,the increasing of pore diameter diminishes electrostatic attraction from nearby cations,so that the hydrogen adsoption capacity of NaOH treated sample does not improve.