Combustion chemistry and flame structure of furan group biofuels using molecular-beam mass spectrometry and gas chromatography – Part I: Furan

Abstract

Fuels of the furan family, i.e. furan itself, 2-methylfuran (MF), and 2,5-dimethylfuran (DMF) are being proposed as alternatives to hydrocarbon fuels and are potentially accessible from cellulosic biomass. While some experiments and modeling results are becoming available for each of these fuels, a comprehensive experimental and modeling analysis of the three fuels under the same conditions, simulated using the same chemical reaction model, has -to the best of our knowledge -not been attempted before. The present series of three papers, detailing the results obtained in flat flames for each of the three fuels separately, reports experimental data and explores their combustion chemistry using kinetic modeling. The first part of this series focuses on the chemistry of low-pressure furan flames. Two laminar premixed low-pressure (20 and 40 mbar) flat argondiluted (50%) flames of furan were studied at two equivalence ratios (φ=1.0 and 1.7) using an analytical combination of high-resolution electron-ionization molecular-beam mass spectrometry (EI-MBMS) in Bielefeld and gas chromatography (GC) in Nancy. The time-of-flight MBMS with its high mass resolution enables the detection of both stable and reactive species, while the gas chromatograph permits the separation of isomers. Mole fractions of reactants, products, and stable and radical intermediates were measured as a function of the distance to the burner. A single kinetic model was used to predict the flame structure of the three fuels: furan (in this paper), 2-methylfuran (in Part II), and 2,5-dimethylfuran (in Part III). A refined sub-mechanism for furan combustion, based on the work of Tian et al. [Combustion and Flame 158 (2011) 756-773] was developed which was then compared to the present experimental results. Overall, the agreement is encouraging. The main reaction pathways involved in furan combustion were delineated computing the rates of formation and consumption of all species. It is seen that the predominant furan consumption pathway is initiated by H-addition on the carbon atom neighboring the O-atom with acetylene as one of the dominant products.

Advanced Biofuels and Beyond: Chemistry Solutions for Propulsion and Production

“…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.…”

“…[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.…”

“…[178] The general reaction sequence shows that-not unexpectedly-2-MF is an intermediate in the consumption of 2,5-DMF; detailed pathways for 2-MF and furan are discussed in the companion papers. [173,177] Them ost important initial consumption reaction of 2,5-DMF (42 %) is hydrogen abstraction from the methyl side chain by H, O, OH, and CH 3 .I ti nitiates the dominant reaction sequence that leads to 1,3-cyclopentadiene and phenol, harmful or toxic compounds that were observed in substantially higher concentrations-by factors of up to 30 and 100, respectively-for 2,5-DMF than for the other two furanic fuels. [178] These results are in agreement with observations on 2,5-DMF pyrolysis in Refs.…”

“…Species-selective mass-spectrometric investigations of furan in premixed low-pressure flames [172,173] were presented regarding an early development of ar eaction mechanism. [172,214] For2 -MF,i gnition delay times [174,215,216] and species measurements in flames [177,217] were complemented with modeling, [177] but an umber of species were identified experimentally that were not considered by the model, which led to further work on 2-MF pyrolysis and decomposition reactions.…”

Nanoscale Characteristics and Reactivity of Nascent Soot from n-Heptane/2,5-Dimethylfuran Inverse Diffusion Flames with/without Magnetic Fields

“…There were amount of literatures focusing on the study of chemistry and flame structure of furanic fuel flames. Using molecular beam mass spectrometry and gas chromatography, the combustion chemistry and flame structure of furan group biofuels in flames of furanic compounds and those of other fuels have been investigated by Kohse-Höinghaus's group [39,40]. They found that DMF offered a priori surprising ability to form soot precursors compared to less substituted furans and to other fuels [41,42].…”