Mechanism and Thermochemistry of Coal Char Oxidation and Desorption of Surface Oxides

Gianluca Levi, Mauro Causà, Paolo Lacovig, Piero Salatino, Osvalda Senneca*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review


The present study investigates the coal char combustion by a combination of thermochemical and X-ray photoemission spectroscopy (XPS) analyses. Thermoanalytical methods (differential thermogravimetry, differential scanning calorimetry, and temperature-programmed desorption) are used to identify the key reactive steps that occur upon oxidation and heating of coal char (chemisorption, structural rearrangement and switchover of surface oxides, and desorption) and their energetics. XPS is used to reveal the chemical nature of the surface oxides that populate the char surface and to monitor their evolution throughout thermochemical processing. XPS spectra show the presence on the carbon surface of three main components. It is shown that the most abundant oxygen functionality in the raw char is epoxy. It decreases with preoxidation at 300°C and even more at 500°C, where carboxyl and ether oxygen functionalities prevail. The rearrangement of epoxy during preoxidation goes together with activation of the more stable and less reactive carbon sites. Results are in good agreement with semi-lumped kinetic models of carbon oxidation, which include (1) formation of "metastable" surface oxides, (2) complex switchover, and (3) desorption into CO and CO2.

Original languageEnglish
JournalEnergy and Fuels
Issue number3
Pages (from-to)2308-2316
Number of pages9
Publication statusPublished - 16 Mar 2017


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