CO-2-REACTIVITY OF EUCALYPTUS KRAFT LIGNIN CHARS

CO2-gasification of four chars prepared from slow pyrolysis of eucalyptus kraft lignin at temperatures ranging from 823 to 1673 K has been studied by isothermal thermogravimetric experiments. The reactivity versus conversion curves at temperatures between 1023 and 1223 K have been obtained. A substantial decrease in reactivity results from increasing the severity of pyrolysis conditions which can be attributed to a decrease of active site concentration for both catalysed and uncatalysd reaction. The inorganic impurities of the chars, primarily Na, showed an important catalytic effect at comparatively low Na/C atomic ratios, most probably due to a fine dispersion throughout the carbon matrix related to the origin of the starting material. Both catalysed and uncatalysed gasification can be well represented by an apparent activation energy value of 230 +/- 15 kJ/mol.