BaX型分子筛上对二甲苯吸附选择性影响因素研究

为获得较高的对二甲苯选择性，采用脉冲实验对BaX分子筛进行评价，系统研究了分子筛骨架硅铝比、钠离子交换度和含水率对分离系数的影响规律。结果表明：分子筛骨架硅铝比从2.01增加至2.53时，对二甲苯相对于间二甲苯（βP/M）、邻二甲苯（βP/O）的分离系数均先增大后减小，骨架硅铝比为2.2~2.4时二者达到最高点；对二甲苯相对于乙苯（βP/E）的分离系数呈线性减小趋势；钠离子交换度越高，分离系数βP/E，βP/M，βP/O随之增大，钠离子交换度大于94.3%时三者达到最大值；BaX分子筛的含水率从2.0%增加至8.2%时，分离系数βP/E，βP/M，βP/O均先增大后减小，含水率为4.0%~5.0%时选择性最佳；在二元混合体系下通过静态吸附平衡测定对二甲苯相对于对二乙苯（βPX/PDEB）的分离系数，较高骨架硅铝比BaX分子筛的βPX/PDEB随对二甲苯质量分数的变化较小，且更接近于1.0。

INFLUENCE FACTORS OF PARA-XYLENE SELECTIVE ADSORPTION ON BaX-TYPE ZEOLITE

In order to achieve high para-xylene (PX) selectivity, pulse test was employed to evaluate the performance of BaX-type zeolite, the influences of the framework SiO2/Al2O3 molar ratio of X zeolite, Na+ exchange ratio and water content on the PX selectivity were investigated systematically. It was found that with the increasing of the framework SiO2/Al2O3 molar ratio from 2.01 to 2.53, the separation factors of PX to meta-xylene (βP/M) and ortho-xylene (βP/O) increased firstly, and then decreased. The two separation factors reached the highest point within the framework SiO2/Al2O3 molar ratio of 2.20-2.40. The separation factor of PX to ethylbenzene (βP/E) exhibited alinearly decreased trend with the increase of the framework SiO2/Al2O3 molar ratio. All of βP/M, βP/O and βP/E increased with the increase of Na+ exchange ratio, and maintained stable when Na+ exchange ratio was higher than 94.3%. As the water content in the BaX zeolite increased from 2.0% to 8.2%, βP/M, βP/O and βP/E increased firstly and then decreased, with the highest points in the water content range of 4.0-5.0%. The separation factor of PX to para-diethyl benzene (βPX/PDEB) in PX-PDEB binary mixture was also studied using static adsorption equilibrium experiment.The result showed that βPX/PDEBvaried with the changing of PX concentration in PX-PDEB mixture, and theX zeolite with high SiO2/Al2O3 molar ratio favored a small changing range of βPX/PDEB, the value of which was very close to 1.