氢气在A和X型沸石上超临界吸附的格子密度函数模型

采用基于三维Ono-Kondo方程的格子密度函数理论(LDFT)模型模拟了氢气在A和X型微孔沸石上的超临界吸附等温线. 根据沸石孔的尺寸和形状, LDFT模型将氢分子在孔中的吸附位分布近似为简单立方、面心立方和体心立方的团簇结构. 模拟结果表明, LDFT模型可有效地用于描述氢气在A和X型沸石上的单层或多层超临界吸附行为. 模拟所得的吸附等温线与实验测定结果吻合. 特别是, LDFT模型中的氢-沸石作用势能参数的准确性得到了Lennard-Jones(12-6)势能方法的有效验证. 因此, LDFT模型被用于预测了更宽温度和压力范围内氢气在X沸石上的超临界吸附.

Modeling the Supercritical Adsorption of Hydrogen on A- and X-Type Zeolites with a Lattice Density Function

Adsorption isotherms of hydrogen on the microporous zeolites A and X under supercritical conditions were modeled using lattice density function theory (LDFT) based on the three-dimensional Ono-Kondo equation. According to the sizes and shapes of the zeolite pores, the local arrangement of adsorption sites within the pores in the LDFT models were simulated by the clusters of simple cubic lattice, face-centered cubic lattice, and body-centered cubic lattice structures. Results indicate that the LDFT models appear to be effective in describing the multilayer or monolayer adsorption of hydrogen on zeolites A and X under supercritical conditions and the calculated adsorption isotherms agree well with the experimental isotherms measured previously. In particular, the hydrogen-zeolite interaction energy parameters used in LDFT models were verified by the Lennard-Jones (12-6) potential model for cylindrical pores based on a thermodynamics method. These results confirm the reliability of LDFT models in describing hydrogen adsorption on zeolite adsorbents. Using the obtained parameters, adsorption isotherms for hydrogen on zeolite X were predicted using the LDFT model over a wider range of temperatures and pressures.