Mass accommodation coefficients of phenol, 2-nitrophenol, and 3-methylphenol over the temperature range 278-298 K

B Muller, Mathew R. Heal

Research output: Contribution to journalArticlepeer-review

Abstract

The reactive uptake of phenol, 2-nitrophenol, and 3-methylphenol (m-cresol) was measured in a vertical wetted-wall flow reactor over the temperature range 278-298 K using bromine as an aqueous phase scavenger. First-order decays in gas-phase concentration as a function of increased gas-liquid contact time in the reactor were monitored by UV absorption downstream of the contact zone. Mass accommodation coefficients, (x, were derived from measured uptake coefficients by correcting for limitations to mass transfer from radial gas-phase diffusion. Temperature-dependent expressions fitted to the data yielded values of a that decrease from 3.7 x 10(-2) to 6.6 x 10(-3) for phenol, 1.5 x 10(-2) to 1.1 X 10(-3) for 2-nitrophenol, and 1.0 x 10(-2) to 5.1 x 10(-3) for m-cresol over the range 278 K to 298 K. (Estimated overall uncertainty in alpha values of similar to+/-30%). These are the first published accomodation data for the latter two aromatic species. The thermodynamic data derived from the values of alpha were interpreted in terms of the critical cluster model for mass accommodation, yielding average critical cluster sizes of 3.2 +/- 0.6, 4.1 +/- 1.0, and 2 +/- 0.5, for phenol, 2-nitrophenol, and in-cresol, respectively. The larger critical cluster size for 2-nitrophonol is likely attributable to its strong intramolecular hydrogen bonding which significantly reduces the hydrogen bonding strength of this species relative to the other two phenols. It is also demonstrated that the magnitude of the observed enthalpy of mass accommodation for these aromatic compounds correlates well with their excess energy of dissolution. The studied aromatic compounds are important intermediates in the tropospheric oxidation of monoaromatics and react readily in the aqueous phase, Thus knowledge of the mass accommodation coefficient is required to accurately quantify their rate of aqueous phase oxidation.

Original languageEnglish
Pages (from-to)5120-5127
Number of pages8
JournalThe Journal of Physical Chemistry A
Volume106
Issue number20
DOIs
Publication statusPublished - 23 May 2002

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