Kinetic and product study of the atmospheric photooxidation of 1,4-dioxaneand its main reaction product ethylene glycol diformate

A FTIR kinetic and product study of the OH-radical initiated oxidation of 1 ,4-dioxane (DOX) has been performed in a quartz-glass photoreactor in the l aboratory under different conditions and also in the outdoor EUPHORE simula tion chamber in Valencia, Spain. Using the relative kinetic technique, a ra te coefficient of k = (1.24 +/- 0.04) x 10(-11) cm(3) molecule(-1) s(-1) wa s determined for the reaction at 298 K in 1000 mbar of synthetic air, which is in good agreement with other published values. The major reaction produ ct both in the presence and absence of NO was ethylene glycol diformate (ED F). This compound has been synthesized, and authentic samples have been use d for calibration. Integrated band intensities have been calculated for the three strongest bands of EDF: (4.99 +/- 0.06) x 10(-17) cm molecule(-1) fo r 1100-1225 cm(-1), (3.90 +/- 0.05) x 10(-17) cm molecule(-1) for 1670-1820 cm(-1), (9.34 +/- 0.11) x 10(-18) cm molecule(-1) for 2775-3075 cm(-1). In the laboratory reactor, yields for EDF of 87 +/- 9 and 95 +/- 10 mol % wer e obtained using the photolysis of MeONO/NO/air and N2O2/NO/air as the OH r adical sources, respectively. Using only the photolysis of H2O2/air as the ON source resulted in a molar yield of 55 +/- 5 mol % for EDF. In the outdo or EUPHORE simulation chamber a yield of 95 +/- 10 mol % was obtained from irradiation of a DOX/NOx/air mixture. The OH-radical- and Cl-atom-initiated oxidation of EDF has also been investigated. Rate coefficients of k(OH) = (4.72 +/- 0.31) x 10(-13) cm(3) molecule(-1) s(-1) and k(Cl) = (3.52 +/- 0. 09) x 10(-12) cm(3) molecule(-1) s(-1) have been determined for the reactio n of EDF with OH radicals and C1 atoms, respectively, at 298 K and 1000 mba r total pressure. The products determined in the Cl-initiated oxidation in the presence of NOx were formic acid anhydride (FAA), formic acid (FA), and carbon monoxide (CO) with yields of 173 +/- 34 mol %, 45 +/- 9 mol %, and 41 +/- 8 mol %, respectively. Formation of a peroxy formyl nitrate was also observed. In the absence of NOx the yields of FAA, FA and CO were 144 +/- 29 mol %, 39 +/- 8 mol %, and 22 +/- 4 mol %, respectively.