Flue gas desulphurization by activated carbon fibers obtained from polyacrylonitrile by-product

By pyrolysis of a polyacrylonitrile textile by-product, subsequent activation by CO, and treatment (at high temperature) with a N-2 flow containing a low percentage of O-2 or of NH3, three carbonaceous matrices are obtained having a high surface area and surface sites with basic characteristics. The SO2 sorption properties of these carbon samples (in the temperature range between 100 and 160 degreesC) from gaseous mixtures having a similar composition to flue gases, seems to be promoted by nitrogen bonded to carbon. The SO2 adsorbed by the carbons can be divided, by suitable extraction with distilled water, into: (i) desorbable, such as SO2 or H2SO3, (ii) desorbable, such as SO3 or H2SO4, (iii) non-desorbable. Following 10 SO2 adsorption and desorption cycles, the surface area values of the activated carbons remain practically constant, while both the content of the acidic surface sites and the amount of non-desorbable SO2 increase; this results in the decrease in the SO, carbon sorption property seeming to be even more marked for the carbon sample containing nitrogen. (C) 2002 Elsevier Science Ltd. All rights reserved.