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n -Dodecane is a potential diesel and jet fuel surrogate. The combustion chemistry of n -dodecane has long been a research focal point, but its long carbon-chain length makes it challenging to obtain detailed information on cool flame intermediates and products. Determining the detailed formation mechanism of combustion intermediates is important to validate possible reaction pathways, develop detailed reaction mechanisms, and improve kinetic models. Reports on its low-temperature (low-T) oxidation, including detailed speciation in the oxidation process, are scarce. In this work, low-T oxidation of n -dodecane was investigated in a jet-stirred reactor coupled with synchrotron vacuum ultraviolet photoionization mass spectrometry and gas chromatography. Experimental conditions were maintained at atmospheric pressure with an initial fuel concentration of 0.4%, equivalence ratio of 0.5, and residence time of 2 s. A large number of cool flame intermediates and products, including alkenes, dienes, aldehyde/keto compounds, olefinic aldehyde/keto compounds, diones, cyclic ethers, peroxides, acids, and alcohols/ethers, were identified and classified. Particular attention is focused on understanding these intermediates and products. Detailed structures and the most likely formation channels for these species are proposed and discussed herein. These results provide a solid database for the low-T oxidation of n -dodecane, which is important for the development of future kinetic models. [ABSTRACT FROM AUTHOR]

Pyridine is an important model compound of fuel-nitrogen during the coal combustion process. The lean oxidation of pyridine was studied over 800–1100 K at atmospheric pressure with the equivalence ratio of 0.4 in a jet-stirred reactor. Pyridine and its oxidation products were measured by tunable synchrotron vacuum ultraviolet photoionization molecular-beam mass spectrometry and gas chromatography analyzer. Three-stage consumption phenomenon of pyridine and O 2 was observed including a fast consumption stage at 910–920 K, a moderate consumption stage at 920–1000 K, and a slow consumption stage at 1000–1100 K. HCN, N 2, N 2 O, and HNCO are the major nitrogenous oxidation products of pyridine. CO, CO 2 , HCN, and HNCO are the dominant carbonaceous products. HNCO is uniquely detected in the lean oxidation of pyridine compared with rich oxidation. A new pyridine LTO 2.0 model comprising 210 species and 1349 reactions was proposed, providing a good prediction of pyridine and its major oxidation products against experimental data. N 2 O emission is larger than NO at 1100 K. HCN is the dominant nitrogenous intermediate under both fuel-lean and fuel-rich conditions. Results of this work provide a detailed analysis of the nitrogen evolution mechanism of pyridine oxidation under the fuel-lean condition, which is close to the real industrial low-temperature coal combustion processes including the MILD combustion, fluidized bed combustion, etc. [ABSTRACT FROM AUTHOR]

Benefitting from the rapid development of instrumental analysis methods, intermediate products that were difficult to probe in the past can now be measured and quantified in complex reaction systems. To understand low temperature reactions of interest for combustion applications, and reduce the deviations between model predictions and experimental measurements, constant advancement in understanding low temperature oxidation process is necessary. This work examines the oxidation of n -heptane in jet-stirred reactors at atmospheric pressure, with an initial n -heptane mole fraction of 0.005, equivalence ratio of 0.5, a residence time of 1s, and over a temperature range of 500-800 K. Reaction products were analyzed using synchrotron ultra-violet photoionization mass spectrometry, gas chromatography, and Fourier-transform infrared spectroscopy. Ignition delay times of n -heptane/O 2 /CO 2 mixture were measured in a rapid compression machine at 20 and 40 bar over a 600-673 K temperature range. Based on the experimental results, a comprehensive kinetic model of n -heptane low temperature oxidation was developed by considering the sub-mechanisms of keto-hydroperoxide, cyclic ether, heptene isomers, and the third O 2 addition reaction, and by updating the rate constants of keto-hydroperoxide decomposition and second oxygen addition reactions. The combination of reaction mechanism development and evaluation of the rate constants of key reactions enabled the model to effectively predict the species concentrations and ignition delay times of n -heptane low temperature oxidation, providing additional insight into alkane low temperature oxidation chemistry. [ABSTRACT FROM AUTHOR]