Atmospheric and high pressures pyrolysis study of n-decane in a flow reactor with online GC-MS/FID analysis: Experiments and modeling

Abstract

The atmospheric and high-pressure pyrolysis of n-decane was studied in a flow tube reactor combined with online GC–MS/FID at 723−1123 K, 0.1–3.0 MPa (highly diluted in helium). Compared with 0.1 MPa, the conversion of n-decane and mole fraction of alkenes clearly increased at 3.0 MPa at the fixed temperature, and more aromatics were observed including toluene, styrene, ethylbenzene, indene and naphthalene, suggesting that the secondary reactions are more intense under high pressure. To account for these differences, a detailed kinetic model with 191 species and 1117 reactions was constructed by incorporating the aromatics subset to a n-decane model developed in previous low-pressure work, and further validated against literature data covering a wide pressure range (0.004–7.2 MPa) with reasonable reproducibility. The current model was compared against three literature kinetic models (LLNL, JetSurf 2.0 and Rev1stGen) and showed a better accordant with the conversion of n-decane and the selectivity of major products. Based on the rate of production and sensitivity analysis using the current model, the results show that although the total consumption of n-decane is weakly pressure-dependent at fixed temperature and residence time under the investigated conditions, the formation and consumption pathways of primary products change significantly attributed to the enhanced bimolecular abstraction and combination reactions at higher pressures. For the formation of benzene, the combination of 1,3-butadien-2-yl with ethylene is the main pathway at both 0.1 and 3.0 MPa, while the additional combination reactions: propargyl with allyl and cyclopentadienyl (c-C5H5) with CH3 become dominant at 0.1 MPa and 3.0 MPa, respectively. For the formation of larger aromatic naphthalene, the self-recombination of c-C5H5 is the most important channel at all investigated pressures.