Accretion reactions of octanal catalyzed by sulfuric acid : Product identification, reaction pathways, and atmospheric implications

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

12 Scopus Citations
View graph of relations

Author(s)

Detail(s)

Original languageEnglish
Pages (from-to)7138-7145
Journal / PublicationEnvironmental Science and Technology
Volume42
Issue number19
Publication statusPublished - 1 Oct 2008
Externally publishedYes

Abstract

Atmospheric accretion reactions of octanal with sulfuric acid as a catalyst were investigated in bulk liquid-liquid experiments and gas-particle experiments. In bulk studies, trioxane, α,β-unsaturated aldehyde, and trialkyl benzene were identified by gas chromatography-mass spectrometry as major reaction products with increasing sulfuric acid concentrations (0-86 wt%). Cyclotrimerization and one or multiple steps of aldol condensation are proposed as possible accretion reaction pathways. High molecular weight (up to 700 Da) oligomers were also observed by electrospray ionization-mass spectrometry in reactions under extremely high acid concentration conditions (86 wt%). Gas-particle experiments using a reaction cell were carried out using both high (∼20 ppmv) and low (∼900 ppbv) gas-phase octanal concentrations under a wide range of relative humidity (RH, from 80 wt% to 43 wt% H2SO4) and long reaction durations (24 h). One or multiple steps of aldol condensation occurred under low RH (80 wt% and 64 wt% H2SO4, respectively) and high octanal concentration (∼20 ppmv) conditions. No cyclotrimerization was observed in the gas-particle experiments even under RH conditions corresponding to similar sulfuric acid concentration conditions that favor cyclotrimerization in bulk studies. No accretion reaction product was found in the low octanal concentration (∼900 ppbv) experiments, which indicates that the accretion reactions are not significant as expected when the gas-phase octanal concentration is low. A kinetic analysis of the first-step aldol condensation product was performed to understand the discrepancies between the bulk and gas-particle experiments and between the high and low octanal concentrations in the gas-particle experiments. The comparisons between experimental results and kinetic estimations suggest that caution should be exercised in the extrapolation of laboratory experiment results to ambient conditions. © 2008 American Chemical Society.

Citation Format(s)

Accretion reactions of octanal catalyzed by sulfuric acid : Product identification, reaction pathways, and atmospheric implications. / Yong, Jie Li; Lee, Alex K. Y.; Lau, Arthur P. S.; Chan, Chak K.

In: Environmental Science and Technology, Vol. 42, No. 19, 01.10.2008, p. 7138-7145.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review