Characterization of coke deposited on catalysts by carbon K-edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy

Abstract

C K-edge NEXAFS spectra could distinguish between the structures of coke on the catalysts used in fluid catalytic cracking, hydrotreatment and dry reforming of methane from the characteristic ;π* features. A particular advantage of NEXAFS spectroscopy was found in the characterization of highly aromatic coke that could not be analyzed by cross-polarization 13C-NMR due to the lack of magnetization transfer from 1H to 13C. The NEXAFS results elucidated two different structures of coke on Ni catalysts used in dry reforming of methane; one with a graphitic structure formed at lower temperatures and the other with a non-graphitic structure formed at higher temperatures.