C_5烷烃分子在AlPO_4-5分子筛中吸附的分子模拟研究

Molecular simulation of C_5 paraffins sorption in AlPO_4-5 Molecular sieves

采用分子水平计算机模拟方法研究了环戊烷、正戊烷和2-甲基丁烷在AlPO4 5分子筛中的吸附,得到了有关吸附平衡常数、吸附热、吸附等温线以及平均势能等。结果表明,在373K,2-甲基丁烷的饱和吸附量高于其他两种异构体;473K,环戊烷的饱和吸附量高于其他两种异构体;573K,在所测试的压力范围内,环戊烷的吸附量都高于其他两种异构体,2-甲基丁烷的吸附量高于正戊烷。C5烷烃分子在AlPO4 5中吸附量的不同是由于他们在分子筛中的排列方式不同而引起的。低吸附量时C5烷烃分子平均势能不随吸附量变化;高吸附量时平均势能随着吸附量的增加而降低;而2-甲基丁烷和环戊烷分子的平均势能变化更加明显。

The sorption of C_5 paraffins in AlPO_4-5 molecular sieves at 303K～675K was simulated by Monte Carlo method with Cerius^2 developed by MSI. The Henry constant, the isotherms and the average potential energy of C_5 in the framework were obtained. It was observed that the sorption capacity of 2-methylbutane was higher than that of cyclopentane at 373K, and this sequence was reversed at 473K; the sorption loading of cyclopentane was higher than that of 2-methylbutane and n-pentane at 573K under 0～20kPa, which could be well interpreted based on the packing fashion of sorbates in the channel of AlPO_4-5 molecular sieves. Moreover, the average potential energy of C_5 decreased with the increase of the loadings at higher loadings. A sharp decrease of average potential energy was found for both of 2-methylbutane and cyclopentane when the loading was higher than 1 molecule/unit cell.