Carbon Deposition by Pyrolysis Reaction of CH₄–H₂ Mixtures on Iron

Abstract

The carbon deposition behavior by pyrolysis reactions of CH₄–H₂ mixtures on iron at 1133 to 1323 K has been studied. Kinetic measurements and chemical analyses showed that the carbon deposition started when the carbon concentration in iron reached the solubility limit of graphite in austenite. Two types of carbons, filmy carbon and filamentous carbon, were observed on iron. The deposition of filmy carbon proceeded at an early stage, and particularly at temperatures above 1273 K filmy carbon spread on iron so fast that the iron surface was completely covered with it in a very short time. After some induction period filamentous carbon deposited on the iron substrate which had been covered with filmy carbon, so that it brought the film to the local break. Mechanisms are suggested for the deposition of these two types of carbons.