Preparation and Characterization of Activated Carbons for SO2 Adsorption from Taixi Anthracite

An attempt was made to convert Taixi anthracite into microporous activated carbons for use as SO₂ adsorbents from flue gas. In this work the activated carbons (ACs) were produced by physical activation with CO₂ and steam, respectively. Specifically, the effects of activation temperature and burn-off degree on the physico-chemical properties of two series were comparatively studied. The surface area and porosity of different AC samples were studied by N₂ adsorption at 77 K. The surface chemistry was evaluated by FTIR. The preparation by steam activation (at 850°C) produces activated carbons showing micropore volume and surface area larger than those prepared by CO₂ activation with similar burn-off degree. With an increase in the degree of burn-off, all types of porosity increase. The CO₂ activation leads to samples with continuous evolution of ultramicropore volumes, while there is a slightly increase of that in the case of steam activation. At higher activation temperature, the decrease of micropore volume is attributed to an external burn-off for series C. For all the AC samples, the amount of the basic surface sites always appears much higher than the amount of the acidic surface sites. The activated carbons prepared with higher micropore volumes and quantity of the basic surface sites present better SO₂ sorption properties.