Critical Evaluation of Henry’s Law Constants for Nitrogen on the NaX (13X) Zeolite

Abstract

Henry’s constants are evaluated from 164 isotherms from 64 published studies with the goal of providing information for use in the design of PSA, TSA, and adsorption columns. The isotherms are inspected using the linear virial isotherm as a probe mechanism. Five different categories of isotherms may be identified by this technique. Henry’s law constants, K′ in g/100gZ/kPa and dimensionless K, are given by and where −ΔU 0 = 18.55 kJ/mol and −ΔH 0 = 20.53 kJ/mol. The values of −ΔH 0 are comparable to most literature values, but some idiosyncratic data are identified. Heats of adsorption and entropy changes are evaluated from the Henry constants. Consideration of the heats of adsorption indicates homogeneous adsorption in the α cage for much of the isotherm and for most forms of 13X zeolites studied. The isosteric heat of adsorption data in the literature revealed that adsorption of nitrogen on the 13X zeolite is primarily homogeneous in the large cavity at ≈19 kJ/mol. There are exceptions, such as inhomogeneous loading and adsorption in the β cage. Evaluation of entropy changes upon adsorption indicates that order increases from the vapor phase to the adsorbed phase in the α cage and even more so in the β cage. The entropy of adsorption between the gas phase and adsorbed phase indicated a decrease of 35 J/mol·K for adsorption in the large cavity and 59 J/mol·K on adsorption into the sodalite cage.

Experimental Investigation of Adsorption and CO2/CH4Separation Properties of 13X and JLOX-500 Zeolites during the Purification of Liquefied Natural Gas

“…Henry’s law constant was an affinity constant for the adsorbate molecules toward the adsorbent and correlated with their interaction between each other, the accurate calculation of which was critical to the design of the PSA, TSA, and column. , When the pressure was sufficiently low (i.e., in Henry’s law region), the Langmuir equation usually used to obtain Henry’s constant was reduced to the linear Henry’s law equation given by eq . , …”