Comparison of new thermal and reactant gas blending methods for the controlled oxidation of carbon

Two approaches to sample controlled thermal analysis (SCTA) used preparativ ely were contrasted using the air activation of a nutshell derived carbon. The rate of reaction, corresponding to the level of evolved carbon dioxide, was monitored using a quadrupole mass spectrometer and controlled via soft ware using a feedback loop. In the first approach, control of the rate was achieved via temperature under a constant concentration of oxygen in nitrog en, while in the second the reactant gas concentration (oxygen/nitrogen rat io) was changed while the furnace was held isothermally. Due to the exother mic nature of the carbon-oxygen reaction, temperature control of the activa tion process at high reaction rates was difficult and produced oscillatory behaviour, while good control of the process could be achieved using the ga s concentration method at higher reaction rates. By using oxygen rather tha n the more usual CO2 or H2O activation at 800-1000 degrees C, the reaction takes place at 200-300 degrees C with a consequent significant saving in en ergy costs. Published by Elsevier Science B.V.