Combustion chemistry and flame structure of furan group biofuels using molecular-beam mass spectrometry and gas chromatography – Part III: 2,5-Dimethylfuran

Abstract

This work is the third part of a study focusing on the combustion chemistry and flame structure of furan and selected alkylated derivatives, i.e. furan in Part I, 2-methylfuran (MF) in Part II, and 2,5-dimethylfuran (DMF) in the present work. Two premixed low-pressure (20 and 40 mbar) flat argon-diluted (50%) flames of DMF were studied with electron-ionization molecular-beam mass spectrometry (EI-MBMS) and gas chromatography (GC) under two equivalence ratios (φ=1.0 and 1.7). Mole fractions of reactants, products, and stable and radical intermediates were measured as a function of the distance to the burner. Kinetic modeling was performed using a reaction mechanism that was further developed in the present series, including Part I and Part II. A reasonable agreement between the present experimental results and the simulation is observed. The main reaction pathways of DMF consumption were derived from a reaction flow analysis. Also, a comparison of the key features for the three flames is presented, as well as a comparison between these flames of furanic compounds and those of other fuels. An a priori surprising ability of DMF to form soot precursors (e.g. 1,3-cyclopentadiene or benzene) compared to less substituted furans and to other fuels has been experimentally observed and is well explained in the model.

Advanced Biofuels and Beyond: Chemistry Solutions for Propulsion and Production

“…[178] Although CO is amajor product under fuel-rich conditions,i ti sa lso an early elimination product for furan and 2-MF,b ut cannot be formed by elimination from 2,5-DMF.A cetylene (C 2 H 2 ) at ypical soot precursor,r eaches similar peak concentrations in all three flames.The formation of ethane (C 2 H 6 )isdirectly related to that of the methyl radical and, therefore,d epends on the number of methyl groups in the fuel structure. 1,3-Butadiene (C 4 H 6 ), an undesirable HC component, is formed through fuel-specific decomposition and hydrogenaddition reactions and is less favored for furan, where the CO elimination pathway dominates.R egarding potential OHC components,k etene (C 2 H 2 O) is most abundant in the Figure 9.…”

“…[220,221] Some explanations for these observations have recently been provided by Cheng et al [221] Laminar flame experiments with 2,5-DMF accompanied by modeling were performed by TogbØ et al [178] and Weietal. [222] To obtain ab etter understanding of mechanistic details, individual reaction pathways for 2,5-DMF are being studied experimentally and with quantum chemical methods,w ith ap articular focus on important initiation reactions for fuel consumption.…”

“…Comparisonofexperimental ignition delay times for mixtures of 0.75 %2 ,5-DMF and 2.81 %, 5.625 %, and 11.25 %O 2 in Ar at 1bar (from Ref. [176]) versus predictionsw ith the mechanisms of Somers et al [176] (solid line), Sirjean et al [214] (dashed line), and TogbØ et al [178] (dotted line). Reproduced from Ref.…”

“…[163] This knowledge has led to the formulation of reaction classes and associated rate rules for alcohols,a ldehydes,a nd carbonylic species, which permit the further development of mechanisms for such compounds. [167,168] Quite recently,c hemical mechanisms have also been developed for fuels from second-generation processes and beyond, including larger alcohols, [164,165] ethers, [169] and ketones, [170,171] and as ubstantial amount of work has been devoted to the furans [172][173][174][175][176][177][178] and tetrahydrofurans,w hich are in the focus of the present Review. [69,179,180] It is interesting to understand how macroscopic properties such as derived cetane numbers (compare Section 2a nd Figure 1) for advanced biofuels relate to the chemical kinetics mechanisms,s ince such understanding can substantially support strategies for fuel design.…”

“…Selected results from the only comparative suite of flame studies of the three furans reported in Refs. [173,177,178] are presented in Figure 10. Here,m ole fractions for these onedimensional low-pressure flames are reported as afunction of the reaction progress,g iven in terms of height above the burner.…”