NaA沸石分子筛吸水性能的研究

Study of the H_2O Adsorption Property of Zeolite Molecular Sieve NaA

应用脉冲进样法和程序升温脱附技术,研究了NaA沸石分子筛在298—523K范围内对水的吸附性能和脱附再生性能,发现了NaA沸石分子筛上存在三种吸水位置。测定并讨论了NaA沸石分子筛用于气相脱水和再生的最佳操作温度和条件。

The adsorption property of H_2O on zeolite molecular sieve NaA has beer, studied by pulse syringe method and temperature programmed desorption (TPD)technique. There are three kinds of H_20 adsorption sites for zeolite NaA, namely, weak sites, medium strong sites and strong sites, corresponding to peak temperatures of 453K, 580K and 647K, respectively. Within the temperature range 350—473K, the adsorption capacity of the weak sites decreases rapidly with the elevation of adsorption temperature, while that of medium strong and strong sitos does not change appreciably. These results lead to the conclusion that 350—473K is the best temperature range for the re cycling operation of drying by adsorption of H_20 and regeneration of zeolite NaA by dehydration. According to the activation energy of desorption E_d=49.5kJ/mol and preex ponential factor k_0=4.12 x 10~3s^(-1)for the desorption of H_2O on the weak sites of zeo lite NaA, the desorption rate constant has been calculated and the basic reason for theadsorption temperature having a serious effect on the TPD peak shape of the weak sites has been revealed.