Decomposition of fluorinated diethers on the clean iron surface

Polymeric perfluoroalkylethers are being considered for use as lubricants in high temperature applications, but have been observed to catalytically decompose in the presence of metals. X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD) were used to explore the decomposition of three model fluorinated ethers on clean iron surfaces. Low temperature adsorption of the model fluorinated ethers was molecular. Defluorination of the three model compounds was observed at remarkably low temperatures, 155 K and below, with formation of iron fluoride. Preferential C-F bond scission occurred at methoxy, CF₃O, of perfluoro-1-methoxy-2-ethoxy ethane and perfluoro-1-methoxy-2-ethoxy propane and at CF₃ CF₂O of perfluo-o-1,3-diethoxy propane. The reactivity of the iron toward perfluoroalkylether decomposition when compared to other metals is due to the strength of the iron fluoride bond and the strong electron donating ability of the metallic iron.