Trace Level Adsorption of Toxic Sulfur Compounds, Carbon Dioxide, and Water from Methane

Abstract

This paper presents breakthrough curves and isotherms of the adsorption of sulfur compounds, carbon dioxide, and water from a carrier gas (methane) on a fixed solid bed at 298 K and 1.3 bar. For the investigation two industrial adsorbents (silica–alumina gel, zeolite 5A) were used. The adsorptives were prepared in trace level concentrations up to 2000 mol-ppm. Common isotherm equations were fitted to the adsorption capacities which were obtained from breakthrough curves by mass balances. Binary systems (one adsorptive in methane) and ternary systems (two adsorptives in methane) are included. Methane is used to duplicate conditions of industrial scale natural gas treatment as far as possible. Though methane is a very weak adsorptive on oxidic adsorbents the reported adsorptive capacities might be slightly lower than pure component loadings accessible from a volumetric or gravimetric method. The adsorption isotherms of the binary systems show distinctly different capacities depending on the polarity of the adsorptive and the structure of the adsorbent. The investigation of the ternary systems reveals significant coadsorption and displacement as well as kinetic effects due to the presence of competing adsorptives.