Kinetic study of esterification of sulfuric acid with alcohols in aerosol bulk phase

摘要

In this study, we hypothesize that the formation of organosulfates throughthe reactions between sulfuric acid and alcohols in the aerosol bulk phase ismore efficient than that in solution chemistry. To prove this hypothesis, thekinetics of the organosulfate formation was investigated for both aliphaticalcohol with single OH group (e.g., 1-heptanol) and the multialcohols rangingfrom semivolatiles (e.g., hydrated-glyoxal and glycerol) to nonvolatiles(e.g., sucrose) using analytical techniques directly monitoring aerosol bulkphase. Both the forward () and the backward () reaction rateconstants of organosulfate formation via the particle phase esterification of1-heptanol with sulfuric acid were estimated using a Fourier TransformInfrared (FTIR) spectrometer equipped with a flow chamber under varyinghumidities. Both and are in orders of10 L mol min, which are three orders of magnitudehigher than the reported values obtained in solution chemistry. The formationof organosulfate in the HSO aerosol internally mixed withmultialcohols was studied by measuring the proton concentration of theaerosol collected on the filter using a newly developed Colorimetryintegrated with a Reflectance UV-Visible spectrometer (C-RUV). The formationof organosulfate significantly decreases aerosol acidity due to thetransformation of HSO into dialkylsulfates. The forwardreaction rate constants for the dialkylsulfate formation in themultialcohol-HSO aerosols were also three orders of magnitudegreater than the reported values in solution chemistry. The water content(O) in the multialcohol-HSO particle wasmonitored using the FTIR spectrometer. A large reduction ofO accords with the high yield of organosulfate in aerosol.Based on this study, we conclude that organosulfate formation in atmosphericaerosol, where both alcohols and sulfuric acid are found together, issignificant.