화학공학소재연구정보센터
Journal of Physical Chemistry A, Vol.112, No.7, 1552-1560, 2008
Formation of volatile organic compounds in the heterogeneous oxidation of condensed-phase organic films by gas-phase OH
The yield of volatile organic compounds (VOCs) from the heterogeneous oxidation of condensed-phase organic and hydrocarbon soot films by gas-phase OH has been studied in a coated-wall flow tube at room temperature. Simultaneously, OH concentrations are measured using a chemical-ionization mass spectrometer (CIMS) operated in negative ion mode and VOCs are measured using a commercial proton-transfer-reaction mass spectrometer (PTR-MS). It is observed that a variety of aldehydes/carbonyls and carboxylic acids are formed. Specifically, detailed experiments were conducted with stearic acid, where products are observed that contain as many as 13 carbon atoms with the average carbon number of the products between 3 and 5. The yield of VOCs, relative to the loss of OH radicals, is strongly dependent on the partial pressure of O-2 in the carrier gas, ranging from 0.08+/-0.03 in a nominally pure He carrier gas to 0.34+/-0.14 in 6 Torr of pure O-2. Yields from other organics are somewhat lower than those from stearic acid, ranging in conditions of pure O-2 from 0.10+/-0.04 for BES (bis(ethylhexyl)sebacate), to 0.03+/-0.01 for n-hexane soot, to 0.01+/-0.005 for pyrene. Under atmospheric conditions, OH oxidation of select organics may be an efficient source of small VOCs. In particular, formic acid is formed in significant yield from all the surfaces.