Fourier Transform Infrared Photoacoustic Spectroscopy Characterization of Sulfur-Oxygen Species Resulting from the Reaction of SO₂ with CaO and CaCO₃

Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) has been used to investigate the reaction of SO, in He with CaO and CaCO particles at temperatures between 25 and 900°C. The reaction of SO with CaO occurs at 25°C, while the reaction of CaCO with SO is first evident at 550°C. The initial product of both of these reactions is CaSO. The CaSO then further reacts with SO to form CaSO, CaSO, and CaS at higher temperatures. At 900°C and above, the net production of SO and SO is decreased because of the decomposition of SO. FT-IR/PAS depth-profiling experiments indicate the formation of a reaction-limiting product layer of SO and SO from the above reactions on the surface of the CaO and CaCO particles.