Low-temperature oxidation of n-butanol in a jet-stirred reactor: Detailed species measurements and modeling studies

n-Butanol is a new generation of liquid biofuel. A detailed understanding of the low-temperature combustion chemistry of n-butanol is instructive for its practical application in advanced low-temperature engines. The hightemperature combustion chemistry of n-butanol has been extensively studied, but its low-temperature combustion chemistry remains underexplored, especially the detailed species distribution. In this work, ozone addition was used to enhance the low-temperature oxidation reaction activity to achieve the oxidation of nbutanol in a jet-stirred reactor (JSR) at atmospheric pressure and in the temperature range of 400-800 K. Synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) was used for detailed measurements of species distribution. The identification of some intermediate species contributed to elucidating and verifying the low-temperature oxidation reaction pathways of n-butanol, such as butanal, C-4 hydroxyalkyl hydroperoxides, C-4 hydroxyl cyclic ether, and C-4 keto-hydroperoxide. Furthermore, the formation of several elusive intermediates was also identified (e.g., C2H4O2, C3H6O2, C(4)H(6)On (n = 1 similar to 3), and C4H8O2), highlighting the necessity of further kinetic studies on the low-temperature oxidation of n-butanol. Based on detailed experimental measurements, the n-butanol model was further developed to improve the model predictions by updating the rate constants for the H-atom abstraction reactions of n-butanol by the OH radical, adding the detailed butanal sub-mechanism, etc. Especially, the premature formation of CO2 in the present experiment was satisfactorily explained and predicted by the addition of a generally accepted reaction class (i.e., R O-2 + R O-2 = RO + RO + O-2 of butanal). Overall, this updated model satisfactorily predicts both the ignition delay time reported in the literature and the species distribution obtained in this work.