Oxidation sulfur dioxide in polluted atmospheres. Review

Abstract

6 Parentheses were used in Reactions 2 and 9 to designate that either chemical change or relaxation to ground-state molecules was occurring. » The rate constant for Reaction 9 was calculated by Rao et al. (1969a) from the data of Strickier and Howell (1968).

Particle formation from homogeneous reactions of sulphur dioxide and nitrogen dioxide

“…0 3 kO.OlS% hr-1 has been estimated for low concentrations of SO, a t 23+2OC (Cox, 1972). This value, which is considered to be an upper limit for atmospheric SO,, is lower than previous experimental estimates of the rate (Bufalini, 1971); evidently reaction (2) is very inefficient if it occurs at all.…”

Environmental Combustion Considerations

“…A secondary reaction route to SO 3 The important reducing effect of the SO 2 with respect to different polluted atmospheres mentioned in the introduction of this section becomes evident from these reactions. Some work [5] has been performed on the photochemical reaction between sulfur dioxide and hydrocarbons, both paraffi ns and olefi ns.…”

“…Just as mobile and stationary combustion sources emit some small quantities of NO 2 as well as NO, so do they emit some small quantities of SO 3 when they burn sulfurcontaining fuels. Leighton [2] also discusses the oxidation of SO 2 in polluted atmospheres and an excellent review by Bulfalini [3] has appeared. This section draws heavily from these sources.…”

“…The precise roles of the excited singlet and triplet states in the photochemistry of SO 2 are still unclear [3] . Nevertheless, this point need not be one of great concern since it is possible to write the reaction sequence…”

Some new thermal data and interpretations for the system SO₂-NHS-H₂O-O₂

“…A good deal of study has gone into the oxidation rates of SO, by atmospheric oxygen under many conditions, including the effects of catalysts and pH, as well as of ultraviolet radiation (Bufalini, 1971). Ammonia has been recognized as having a role in the SO, removal process because of its effect in changing the pH of solution droplets in which oxidation takes place, as well as in supplying the cation for the product sulfate (Junge & Ryan, 1958).…”