Probing the structural organisation of sp2 carbons obtained by the Boudouard reaction using in situ Raman scattering in reducing conditions

The catalytic decomposition of carbon monoxide from a mixture of CO and H2 in the presence of iron or iron oxides has been the subject of many studies since the end of 1950s. The Boudouard reaction (2CO → CO2 + C) produces solid carbon deposition in many high temperature industrial processes in which carbon monoxide is a reactant. The aim of this study was to determine whether the oxidation degree of iron has a significant effect in the quantity and in the morphology of carbon deposit. Original in situ Raman device using controlled temperature and gas mixture was developed to explore the evolution of the morphology of the carbon formation during Boudouard's reaction. The results show two types of carbon morphologies (well-structurally organized sp2 carbons in the form of shells and nano-fibers) depending on the content of H2 in the gas mixture. The abundant production of carbon nano-fibers could be responsible for the destruction of refractory materials operating in CO + H2 atmospheres. This study is of outstanding importance to provide helpful observation and basic information on the involved mechanisms for solving this industrial problem.