Carbon deposition on iron–manganese–chromium spinels

Abstract

Previous studies have indicated that carbon is deposited on spinel-type oxides containing manganese, iron, nickel and chromium. Such deposits are often associated with particles containing iron, nickel or manganese. To identify the role played by manganese, spinels containing this element in combination with iron and chromium have been exposed to CO₂–(1%)CO atmospheres in a γ-cell at 550 and 650 °C. Examination of these surfaces by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) has shown that manganese–iron spinels (together with MnO) promote the formation of both filamentary and dense carbon, but that the presence of chromium inhibits this behaviour.