Read Full Article    Cited by

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 106, NO. D6, PAGES 5517–5529, 2001

Heterogeneous reactions of volatile organic compounds on oxide particles of the most abundant crustal elements: Surface reactions of acetaldehyde, acetone, and propionaldehyde on SiO₂, Al₂O₃, Fe₂O₃, TiO₂, and CaO

P. Li

K. A. Perreau

E. Covington

C. H. Song

G. R. Carmichael

V. H. Grassian

Abstract

The heterogeneous reactivity of volatile organic compounds (VOCs) on oxide particles has been investigated. Oxide particles composed of the most abundant elements present in the Earth's crust were used to identify potentially important reactions of VOCs on mineral dust. In particular, heterogeneous reactions of acetaldehyde, acetone, and propionaldehyde on α-Al₂O₃, α-Fe₂O₃, TiO₂, CaO, and SiO₂ particle surfaces have been investigated. Fourier transform infrared and UV/visible spectroscopic measurements show that these carbonyl compounds weakly and reversibly adsorbed on SiO₂. However, on the more basic and acidic oxides investigated, the data show that these carbonyl compounds irreversibly adsorb and can, in part, react on the surface to form larger molecular weight compounds. The kinetics of the heterogeneous reaction of acetaldehyde, acetone, and propionaldehyde on α-Al₂O₃, α-Fe₂O₃, TiO₂, CaO, and SiO₂ were measured with a Knudsen cell reactor at a gas concentration of 6 × 10¹⁰ molecules/cm³. Using the Brunauer-Emmett-Teller surface area of the powdered sample, initial uptake coefficients were determined to be in the 10⁻⁴ to 10⁻⁶ range for the adsorption of carbonyl compounds on the oxides at 298 K. By using these values for the uptake coefficient, it is found that the heterogeneous loss of these trace volatile organic compounds is comparable to that due to photolysis and reaction with OH in the middle to upper troposphere. Although surface adsorption can occur, the measured second-order pressure dependence to form higher molecular weight compounds suggests that these reaction products will less likely form under atmospheric conditions.

Received 26 May 2000; accepted 1 September 2000.

Read Full Article    Cited by

Citation: Li, P., K. A. Perreau, E. Covington, C. H. Song, G. R. Carmichael, and V. H. Grassian (2001), Heterogeneous reactions of volatile organic compounds on oxide particles of the most abundant crustal elements: Surface reactions of acetaldehyde, acetone, and propionaldehyde on SiO₂, Al₂O₃, Fe₂O₃, TiO₂, and CaO, J. Geophys. Res., 106(D6), 5517–5529.

Copyright 2001 by the American Geophysical Union.