Synthesis and characterisation of carbon molecular sieves. High-ash Indian coal

Abstract

The development of carbon molecular sieves (CMS) for use in conjunction with zeolites has gained much importance in the recent past. Much of the information is either patented or confidential. For the present investigation, typical high-ash bituminous coal available indigenously was acid-washed to reduce the ash content. Carbonisation was carried out at 600 and 800°C and the coal was later ground and pelletised with sulphite pulp liquor. The pellets were subjected to activation with steam in fluidisation conditions at 600 and 800°C and for different residence times. The product samples were subjected to adsorption of CO₂, O₂ and N₂ at –196, –183, –93 and 25 °C for characterisation in accordance with the Dubinin–Astakhov equation and with respect to surface area and pore-size distribution. The results indicate that the samples had micropores of size <5 Å. Adsorption was in the order CO₂ > O₂ > N₂ at any given adsorption temperature. A higher temperature and a higher time of activation favoured increasing adsorption capacity or number of microphores in the product samples.