Analysis of the Temperature and Pressure Dependence of the ¹²⁹Xe NMR Chemical Shift and Signal Intensity for the Derivation of Basic Parameters of Adsorption as Applied to Zeolite ZSM-5

Abstract

Temperature and pressure dependences of the ¹²⁹Xe NMR chemical shift and the signal intensity have been investigated using ZSM-5 as an adsorbent under routine conditions without using any high-pressure or especially high-temperature facilities. The use of a rigorously shielded system and a calibration sample for the signal intensity was found to be valuable to obtain reliable data about the chemical shift and the signal intensity. The ¹²⁹Xe NMR data obtained between 0.05 and 1.5 atm and from 24 to 80°C were analyzed based on the Dubinin-Radushkevich equation as well as the Langmuir type equation. In both analyses, chemical shift data succeeded only partially in providing the profile of adsorption, such as energetic aspects, surface area, saturated amount of Xe adsorption and specific parameters of ¹²⁹Xe chemical shift. It was shown that the reliable total analysis was achieved when the chemical shift data were used together with the intensity data. Such an analysis of the chemical shift data, aided by the intensity data, will be useful in performing nano-material analysis on ¹²⁹Xe NMR without invoking the traditional methodology of gravimetric or volumetric adsorption experiments.