萘在介孔分子筛MCM-41与SBA-15上的吸附特性研究

Study on the adsorption behaviours of naphthalene on MCM-41 and SBA-15 mesoporous molecular sieves

对低浓度气相萘在两种常见介孔分子筛MCM-41和SBA-15上的吸附特性进行研究。得到了萘在两种吸附剂上的吸附等温线和不同初始浓度下的穿透曲线,并分别与吸附等温线模型(Langmuir、Freundlich、D-R)和恒定浓度波动力学模型进行了拟合。结果表明,Langmuir模型能很好描述低浓度气相萘的吸附等温线(R2均在99%以上);具有微孔结构的SBA-15对萘的吸附能力要优于仅具备介孔结构的MCM-41。动力学模型在初始浓度较低时能较好地预测萘在吸附剂上的穿透曲线,且在SBA-15上的相关系数高于MCM-41;萘在2.76 mol/L时具有较大介孔的SBA-15的总传质系数K_a更高,表明萘在SBA-15上的总传质阻力更低,更能较快达到传质平衡。

In this paper, the adsorption behaviours of naphthalene on two popular mesoporous molecular sieves, SBA-15 and MCM-41 were studied. The adsorption isotherms were obtained, and fitted with isotherm models of Langmuir, Freundlich and D-R. The breakthrough curves of naphthalene at different initial concentrations were measured, and well predicted by the constant-pattern wave model. Results show that the Langmuir model can well describe the adsorption isotherms of naphthalene at low concentration with R2 higher than 99%. The adsorption ability of SBA-15 with a microporous structure is stronger than that of MCM-41 which contains only mesoporous structures. The predictions on breakthrough curves by the constant-pattern model exhibited higher correlation coefficient for SBA-15 than for MCM-41. The overall mass transfer coefficient Ka of naphthalene on SBA-15 is higher than that on MCM-41 , indicating that there is a lower mass transfer resistance and the mass transfer equilibrium can be achieved faster over SBA-15 .