Thermal Treatment of Lignite for Carbon Molecular Sieve Production

Abstract

Carbon molecular sieves (CMS) were prepared from Greek lignite by a thermal treatment technique involving three sequential stages: carbonization, followed by activation with an oxidizing agent, and aperture modification by coke deposition. Adsorption of N₂ at 77 K and CO₂ at 298 K was used for the characterization of products. Molecular sieving properties were examined by measuring the adsorption kinetic curves of CO₂ and CH₄ at room temperature. Activated samples with the highest surface area were selected for CMS production by employing a propylene cracking technique. High temperatures resulted in the production of materials with large differences in their BET and CO₂ surface areas. CO₂-CH₄ selectivity ratios estimated from the adsorption kinetic curves were high for these samples.