A micro-FTIR study of carbon deposition on metal surfaces from thermal decomposition of jet fuel and n-paraffins

Deposition of carbonaceous solids on metal surfaces from thermal decomposition of jet fuel has become a subject of interest for the development of thermally stable fuels for advanced aircraft. Various microscopic techniques have been used to examine the structure of carbonaceous deposits to elucidate solid formation and deposition mechanisms. In this study, micro-FTIR was used to characterize the deposits formed on three metal substrates, nickel, copper, and stainless steel, from thermal decomposition of jet fuel (JP-8) and n-paraffins. The results show that the chemical constitution of the deposits collected on different metal substrates is different, depending on the reactants, reaction conditions, and the surface morphology of the metal substrate. Heterogeneous surface reactions on nickel and stainless steel substrates govern solid deposition from n-alkanes at high temperatures (>550°C) in a flow reactor, indicating catalysis of solid deposition, which results in the formation of filamentous carbon. Under the same conditions copper surface does not show any catalytic activity. In contrast, the copper surface catalyzes the formation of peculiar fibrous deposits from thermal decomposition of jet fuel in the flow reactor, indicating a different activity of the copper surface compared to those of nickel and stainless steel surfaces.