Anomalous chemical shifts of organic molecules adsorbed on spherical carbon adsorbents

Abstract

The adsorption of simple organic molecules on synthetic carbon adsorbents of the SCA brand, thermovacuum treated at 2273 K, was studied by the PMR method. It was found that adsorbed molecules appear in the PMR spectra in the form of one or several signals, shifted toward strong magnetic fields in comparison with the proton signal of molecules in the condensed phase. The strongest shielding effect on the part of the surface of the material is experienced by adsorbent molecules in the SCA micropores. It was shown that the chemical shift does not depend on the nature of the adsorbed molecules and is apparently determined by the site of coordination in the interplanar gap of the graphitized portions of the carbon material. It is suggested that the anomalous values of the chemical shift of the protons of the adsorbed molecules are due to the influence of ring currents of the graphitized surface.