The effect of diffusion and bulk gas flow on the thermal oxidation of porous carbons—III. Ungraphitised carbons

✍ Scribed by P Hawtin; J.A Gibson

• Publisher: Elsevier Science
• Year: 1966
• Tongue: English
• Weight: 603 KB
• Volume: 4
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(66)90065-0

✦ Synopsis

A previously published mathematical model of the effect of in-pore mass transport resistance on the kinetics of reactions between porous solids and gases has been verified by a study of the oxidation of a baked carbon tube at temperatures in the range 300-420"C. The baked carbon used in these studies had a higher reactivity than the nuclear graphite employed in earlier work. Evidence of the diffusional effect was obtained from gas concentrations in the bore and at the external surface. The effect of superimposed bufk flow of gas through the walls of the carbon tube was examined. Good agreement between the observed results and those calculated from the theory was obtained.

An energy of activation of 55.2 kcalfg. atom was determined for the carbon oxygen reaction. The value of the energy of activation fell markedly at the lower temperatures examined. This reduction was tentatively ascribed to catalysis of the oxidation by the impurities in the carbon which is more important at these lower temperatures.

The order of reaction was determined as 0.78 from measurements carried out at 450°C in the inpore diffusion control regime.