A study of SO2 interaction with sodium carbonates by X-ray photoelectron spectroscopy

Sodium carbonates and their interaction with SO2 and SO2 containing gas mixtures have been investigated by X-ray photoelectron spectroscopy. The samples studied included NaHCO3, NaHCO3·Na2CO3·2H2O, Na2CO3·H2O, Na2CO3·10H2O and anhydrous Na2CO3 prepared from the above compounds by controlled thermal decomposition and/or dehydration. Clean surfaces of anhydrous Na2CO3 are found to be enriched in sodium. The adsorption of SO2 on sodium carbonates yields surface species containing S4+ and S6+ valence states of sulphur. The composition of the typical products of desulphurization reactions carried out with anhydrous carbonates has also been measured. On the basis of the binding energy data sulphite and sulphate are identified in the products. Their distribution has been shown to be dependent on the parent compound used for anhydrous carbonate preparation. The lack of activity of some carbonates is explained in terms of blocking of the active surface by a layer of reaction products.