The chemistry of sodium with sulfur in flames

An experimental and analytical program of sodium/sulfur chemistry has been conducted in a series of fuel rich and lean H₂/O₂/N₂ flames, with and without added sulfur, and covering a wide range of temperatures and stoichiometries. Fluorescence measurements of OH and Na profiles together with sodium line reversal temperature profiles provided a broad data base for kinetic modeling. Analysis indicated NaSO₂ to be the only significant sodium/sulfur product formed in the lean flames. NaOS is dominant in the rich flames, coupled with small contributions from NaSO₂, NaSH, NaS and NaS₂. A bond dissociation energy of D₀(Na---SO₂) = 197 ± 20 kJ mol^?1 is derived. Calculations indicate that the linear or triangular structures for NaOS both co-exist in approximately equal proportions in flames. Analyses based on results developed in the study show that Na₂SO₄ formation is kinetically limited and cannot be a significant gas phase flame product at sodium levels much below 100 ppm. Na₂SO₄ induced corrosion in combustion systems must result from heterogeneously formed Na₂SO₄.