Experimental and kinetic studies of the mutual oxidation of ammonia and n-dodecane at low to high temperatures

In the present study, oxidation of n-dodecane, ammonia and ammonia/ n-dodecane was performed at lean mixtures and atmospheric pressure using a jet-stirred reactor, coupled with synchrotron photoionization mass spectrometry and gas chromatography, at the National Synchrotron Radiation Laboratory in Hefei, China; the mole fractions of reactants and important intermediates were determined. Many intermediates specifically containing C and N (including HCN, CH 2 NH, CH 3 NH 2 , HNCO, CH 3 ON , C 3 H 3 N and CH 3 NO 2 ) were identified during the oxidation of ammonia/ n-dodecane. These key intermediates are crucial to clarification of the crossreaction pathways between ammonia and n-dodecane. At 500-620 K, the low-temperature oxidation of n- dodecane triggered NH 3 oxidation, leading to consumption of NH 3 and formation of various N-containing species such as CH 2 NH, CH 3 ON , CH 3 NO 2 , NO and N 2 O. Ammonia addition affected the low-temperature chemistry of n- dodecane via NH 3 + OH = NH 2 + H 2 O, which competed with the H-abstraction of n-dodecane ( n C 12 H 26 + OH = C 12 H 25 + H 2 O). Moreover, NH 2 radicals produced from NH 3 converted NO 2 to NO via NH 2 + NO 2 = H 2 NO + NO, and NO consumed C 12 H 25 O 2 via NO + C 12 H 25 O 2 = C 12 H 25 O + NO 2 , further inhibiting the low-temperature reactivity of n-dodecane. At 620-770 K, ammonia addition promoted the consumption of n-dodecane through the H-abstraction reactions of n-dodecane by OH radicals, as NO produced by ammonia accelerates the formation of OH radicals via NO + HO 2 = NO 2 + OH. At 770-1100 K, ammonia addition promotes the consumption of n- dodecane via NH 2 + NO = NNH + OH and n C 12 H 26 + NH 2 = C 12 H 25 + NH 3 .