Tropospheric reactivity of 2-ethoxyethanol with OH and NO3 radicals and Cl atoms. Kinetic and mechanistic study

Abstract

Recent studies reveal that 2-ethoxyethanol (2EE) (CH3CH2OCH2CH2OH) is emitted from diesel/biodiesel blends used in vehicles. This compound has also been investigated in blends with diesel fuel for the reduction of CO emissions, hydrocarbons and particulate matter. In the work described here, rate coefficients for the reactions of OH and NO3 radicals and Cl atoms with 2EE have been determined at (298 ± 2) K and a total pressure of ~700 torr using a relative rate method with SPME/GC-MSTOF (Solid Phase Microextraction/Gas Chromatography-Mass Spectrometry Time of Flight Detection) and FTIR (Fourier Transform Infrared Spectroscopy) as detection techniques. The following rate coefficients (in cm3 molecule−1 s−1) have been obtained: (2.02 ± 0.19) × 10−10, (2.17 ± 0.11) × 10−11 and (4.80 ± 0.48) × 10−15 for Cl, ·OH and ·NO3 reactions, respectively. The product formation has also been investigated. Ethylene glycol monoacetate, ethylene glycol monoformate, formaldehyde, ethyl glycolate and ethyl formate have been identified as major products for·OH and Cl reactions. The formation of nitrated compounds has also been observed for the reactions with ·NO3 and with Cl in the presence of NO. The products are explained by a mechanism involving initial attack of the oxidant at the methylene groups followed by subsequent reactions of the resulting alkyl and alkoxy radicals. The atmospheric lifetimes calculated for 2EE reveal that the dominant loss process for this compound is clearly the daytime reaction with the OH radical.