Carbon-carbon dioxide reaction: Kinetics at low pressures and hydrogen inhibition

✍ Scribed by D.L. Biederman; A.J. Miles; F.J. Vastola; P.L. Walker Jr.

• Publisher: Elsevier Science
• Year: 1976
• Tongue: English
• Weight: 542 KB
• Volume: 14
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(76)90009-9

✦ Synopsis

The gasification of a very high purity naturalgraphite was studied at temperatures between960and 1120°C and at CO, pressures below 108 millitorr. For CO, depletion up to at least 90%, gasification rates were lirst order in CO, pressure, that is with no inhibition by CO observed. The activation energy for the rate constant for the oxygen transfer step (103.5 + 5.8 kcahmole) agreed within experimental error with that found from kinetic studies at intermediate CO, pressures where CO does inhibit the reaction. The rate of the oxygen transfer reaction is markedly inhibited by the presence of low pressures of H,. As H, pressure is increased up to 3 millitorr, the gasification rate in CO, at 1100°C monotonically decreases. Further increase in H, pressure, has a negligible effect on rate. From measurements of hydrogenuptakeatreactiontemperature,itisclearthatinhibitioniscaused bydissociativechemisorptionof hydrogenon to active sites. Inhibition by hydrogen is even more marked for the Graphon-CO, reaction and is attributed not only to its chemisorbing on carbon sites but also on to impurity catalyst sites. It is doubtful if true rate constants for the C-CO, reaction, uninhibited by hydrogen, have ever been reported.