In situ X-ray studies of CuOAl2O3 sorbents reacting with coal flue gas

Abstract X-ray absorption fine structure (XAFS) spectroscopy was used to study the local structure around the Cu ion in CuO Al 2 O 3 sorbents in situ . The measurements were performed between room temperature and 400 °C in a reaction cell with and without coal flue gas flow. Similar measurements were carried out using standard copper compounds. No significant changes were observed in the XAFS spectra of the sorbents when the measurements were performed in the presence of nitrogen. In contrast, new near-edge features appeared in the spectra of the sorbents in the presence of flue gas. A strong peak appeared at an energy characteristic of monovalent copper. No significant changes were detected in the Cu-O nearest-neighbour distance for any of the samples. The near-edge spectra were analysed to obtain the partial ratios of monovalent to divalent copper as a function of temperature and metal loading of the sorbents. The standard compounds showed no evidence of a reaction with the flue gas that might suggest the presence of monovalent copper. The present results indicate the complex nature of the reactions taking place on the Cu ion site during removal of SO 2 . The dominant phase after reaction gives the characteristic parameters of copper sulfates.