A comprehensively experimental and kinetic modeling investigation of tetrahydropyran pyrolysis and oxidation in a jet-stirred reactor

Abstract

Tetrahydropyran (THP), a kind of promising green cyclic-ether fuel derived from biomass, exhibits excellent resistance to autoignition characteristics and can be used as an alternative fuel or fuel additive to improve combustion efficiency as well as reduce harmful emissions. To further reveal insights into its high-temperature decomposition and low-and intermediate temperature oxidation behaviors closely related the deflagration to detonation in spark ignition engines, the comprehensive investigation of experiments and detailed kinetic modeling of THP were performed in the present work. The experiments at two equivalence ratios, i.e. ϕ = ∞ (pyrolysis) and ϕ = 1.0, were carried out in a jet-stirred quartz reactor at 1.0 atm and 733–1148 K. More than ten substances were identified and quantified by GC and GC/MS, including small hydrocarbons, oxygenated and stable products. A detailed kinetic model of THP pyrolysis and oxidation was developed by incorporating the O₂ additions of fuel radicals and updating the rate constants of key reactions, and validated and showed the slight an improvement for the speciation profiles newly reported in this work and those available in the previous literature over a wide experimental range of 450–1260 K and 1.0–10.0 atm. Rate of production analysis indicated that the H-abstractions by H attacking are the important pathways governing THP reactivity with a minor contribution from C-C and C-O dissociations of ring-opening reactions in high-temperature pyrolysis, whereas the H-abstractions triggered by OH and HO₂ largely control fuel consumption in low- and intermediate temperature oxidation. The formed three tetrahydropyranyls, especially α-tetrahydropyranyl, will proceed to decompose into acyclic C₅H₉O radicals via C-O and C-C β-scissions or C₅H₉OO₂-2 intermediates via O₂ addition in THP pyrolysis and oxidation, as the main source of small species. For the unique aromatics detected during the pyrolysis, the combination reactions of C2 + C4 unsaturated hydrocarbons predominantly determinate their generation. This work provides new experimental data and further analyses for understanding the pyrolysis and oxidation chemistry of THP and sheds light on directions for future practical application.