Surface Studies of Carbide Formation in Iron Synthesis Catalysts. Technical Progress Report, October 1-December 31, 1984

摘要

This project involves the use of x-ray photoelectron and Auger electron spectroscopy to investigate the catalytically active surfaces formed on bulk and silica-supported iron during Fischer-Tropsch synthesis. The initial phase of the research demonstrated how this technique can be used to identify the various chemical states of iron likely to be present on catalyst surfaces. Representative core level and Auger spectra were measured for a number of materials, including various forms of iron metal, oxides, and carbides. Results of these studies are presently being compiled by the graduate research assistant as a thesis for the Master of Science degree. Core level measurements for metal and oxide samples were in good agreement with XPS studies in the literature and the various iron oxidation states were readily identified by their characteristic Fe(2p) spectra. A procedure for estimating the composition of surfaces which consist of multiple phases (metal and/or oxides) was also developed. The method involves determining the relative contributions of each iron oxidation state to the core level spectrum by a least squares fitting procedure which uses spectra for the single iron species. Analysis of reduced and carburized iron samples indicated that the metal and carbide (chi-Fe sub 5 C sub 2 ) phase can be distinguished by their characteristic Auger line shapes, and by differences in their core level binding energies. (ERA citation 10:015834)