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

Abstract

Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) has been used to investigate the reaction of SO 2 , in He with CaO and CaCO 3 particles at temperatures between 25 and 900°C. The reaction of SO 2 with CaO occurs at 25°C, while the reaction of CaCO 3 with SO 2 is first evident at 550°C. The initial product of both of these reactions is CaSO 3 . The CaSO 3 then further reacts with SO 2 to form CaSO 4 , CaS 2 O 3 , and CaS at higher temperatures. At 900°C and above, the net production of SO 4 = and S 2 O 3 = is decreased because of the decomposition of SO 3 = . FT-IR/PAS depth-profiling experiments indicate the formation of a reaction-limiting product layer of SO 3 = and SO 4 = from the above reactions on the surface of the CaO and CaCO 3 particles.