Kinetic, mechanistic, and modeling study of the OH-radical-initiated oxidation of di-n-butoxymethane (DNBM)

FTIR product studies of the OH-radical-initiate oxidation of di-n-butoxymet hane (DNBM) in the presence of NOx were performed in an indoor photoreactor and in the outdoor simulation chamber EUPHORE in Valencia, Spain. The reac tion products observed in both reaction chambers were n-butoxymethyl format e (NBMF), propionaldeyhde, and di-ii-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/NOx/air/hv and 88 +/- 18 and 69 +/ - 14 mol % in the system DNBM/H2O2/NOx/air/hv, respectively. In the outdoor chamber, yields of 80 +/- 8 and 44 +/- 11 mol % were obtained after sunlig ht irradiation of a DNBM/NOx/HONO/air mixture. For di-n-butyl carbonate (DN BC), an upper limit of less than or equal to 10 mol % was estimated for bot h reaction chambers. In the indoor photoreactor small amounts of n-butyl fo rmate (NBF) and n-butoxymethyl butyrate (NBMB) were also detected with uppe r limits of 3 mol % for each compound. Bimolecular rate coefficients for th e 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) x 10(-12) cm(3) s(-1) and k(OH+DNBC) = (7.07 +/- 1.64) x 10(-1 2) cm(3) s(-1) were obtained. NBMF was synthesized and authentic samples we re used for calibration. A photochemical mechanism was developed to describ e the OH-initiated degradation of di-n-butoxymethane (DNBM) in the presence of NOx. The reaction scheme was tested by comparison of computer box model calculations and experimental data. Experimentally obtained and modeled co ncentration-time profiles for selected reactants are in excellent agreement .