Kinetic, Mechanistic, and Modeling Study of the OH-Radical-Initiated Oxidation of Di-n-butoxymethane (DNBM)

FTIR product studies of the OH-radical-initiated oxidation of di- n -butoxymethane (DNBM) in the presence of NO x were performed in an indoor photoreactor and in the outdoor simulation chamber EUPHORE in Valencia, Spain. The reaction products observed in both reaction chambers were n -butoxymethyl formate (NBMF), propionaldeyhde, and di- n -butyl carbonate (DNBC) . In the indoor reactor yields for NBMF and propionaldeyhde of 77 ± 15 and 78 ± 16 mol % were obtained in the system DNBM/MeONO/NO x /air/ h ν and 88 ± 18 and 69 ± 14 mol % in the system DNBM/H 2 O 2 /NO x /air/ h ν, respectively. In the outdoor chamber, yields of 80 ± 8 and 44 ± 11 mol % were obtained after sunlight irradiation of a DNBM/NO x /HONO/air mixture. For di- n -butyl carbonate (DNBC), an upper limit of ≤10 mol % was estimated for both reaction chambers. In the indoor photoreactor small amounts of n -butyl formate (NBF) and n -butoxymethyl butyrate (NBMB) were also detected with upper limits of 3 mol % for each compound. Bimolecular rate coefficients for the reactions of NBMF and DNBC with OH radicals were determined in the indoor photoreactor using the relative rate technique. Values of k OH+NBMF = (8.00 ± 0.91) × 10 -12 cm 3 s -1 and k OH+DNBC = (7.07 ± 1.64) × 10 -12 cm 3 s -1 were obtained. NBMF was synthesized and authentic samples were used for calibration. A photochemical mechanism was developed to describe the OH-initiated degradation of di- n -butoxymethane (DNBM) in the presence of NO x . The reaction scheme was tested by comparison of computer box model calculations and experimental data. Experimentally obtained and modeled concentration−time profiles for selected reactants are in excellent agreement.