Decomposition of 2-Methylfuran. Experimental and Modeling Study

Abstract

The thermal reactions of 2-methylfuran were studied behind reflected shock waves in a pressurized driver single pulse shock tube over the temperature range 1100−1400 K and with overall densities of ∼3 × 10-5 mol/cm3. A large number of products resulting from unimolecular cleavage of the ring and consecutive free radical reactions were obtained under shock heating. The unimolecular decomposition is initiated by two parallel channels: (1) 1,2-hydrogen atom migration from C(5) to C(4) and (2) a methyl group migration from C(2) to C(3) in the ring. Each channel is followed by two parallel modes of ring cleavage. In the first channel, breaking the OC(2) and the C(4)C(5) bonds in the ring yields CO and different isomers of C4H6, whereas breaking of the OC(2) and the C(3)C(4) bonds yields CH2CO and two isomers C3H4. In the second channel, breaking the OC(5), and C(2)C(3) bonds in the ring yields again CO and isomers of C4H6, whereas in the second mode OC(5), C(2)C(3), and C(3)C(4) are broken to yield CO, C2H2, and C2H4. The four C4H6 isomers in decreasing order of abundance were 1,3-butadiene, 1-butyne, 1,2-butadiene, and 2-butyne. The major decomposition product is carbon monoxide. The rate constant for its overall formation is estimated to be k CO = 1015.88 exp(−78.3 × 103/RT) s-1, where R is expressed in units of cal/(K mol). Other products that were found in the postshock samples in decreasing order of abundance were C4H4, C2H2, CH4, p-C3H4, C2H6, C2H4, a-C3H4, C6H6, C4H4O, C3H6, and C4H2. The total decomposition of 2-methylfuran in terms of a first order rate constant is given by k total = 1014.78 exp(−71.8 × 103/RT) s-1. This rate and the production rate of carbon monoxide are slightly higher than the ones found in the decomposition of furan. An oxygen−carbon mass balance among the decomposition products was obtained. A reaction scheme composed of 36 species and some 100 elementary reactions accounts for the product distribution over the temperature range covered in this study. First order Arrhenius rate parameters for the formation of the various reaction products are given, a reaction scheme is suggested, and results of computer simulation and sensitivity analysis are shown. Differences and similarities in the reactions of furan and 2-methylfuran are discussed.

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

“…Before a potential biofuel should be used in practice, it is advisable to investigate it carefully with respect to its combustion chemistry, including information on the nature and amount of undesired and potentially harmful products. Some of the earlier experimental studies regarding furan fuels have investigated their thermal decomposition [6][7][8][9][10][11][12][13][14][15]. Only a few experiments addressed all three furanic fuels.…”

“…Only a few experiments addressed all three furanic fuels. Especially Grela et al [6] employed a heated flow reactor to determine the decomposition rates of furan, 2-methylfuran (MF), and 2,5-dimethylfuran (DMF), and analyzed the pyrolysis products using an online gas chromatography coupled to a mass spectrometer at very low pressure (1.3×10 −3 mbar) and over the temperature range of 1050-1270 K. Also, Lifshitz et al [7][8][9] used shock tube experiments to investigate the thermal decomposition of these three furanic fuels over the temperature range of about 1050 to 1460 K, at pressures of 2 atm. Measurements of the final products were also obtained using gas chromatography techniques, and a chemical kinetic mechanism was proposed to model their results.…”

“…Measurements of the final products were also obtained using gas chromatography techniques, and a chemical kinetic mechanism was proposed to model their results. Both Grela et al [6] and Lifshitz et al [7][8][9] concluded that the rate coefficients for thermal decomposition of these furanic fuels increase with increasing alkylation of the furan ring.…”

Recent Trends in the Production, Combustion and Modeling of Furan-Based Fuels

“…A large number of experimental studies involved investigations of thermal decomposition in shock tubes and flow reactors [114,[134][135][136][137][138][139][140][141][142][143][144][145][146]. Other studies were aimed at the exploration of rate constants of furan reactions with important radicals during oxidation [20,132,144,[147][148][149][150][151][152].…”

“…The decomposition of 2-MF was explored in a few studies. Lifshitz et al [140] studied 2-MF decomposition in a shock tube over a temperature range of 1100-1400 K. The results revealed two main channels for the decomposition, the migration of 1,2-H atom from C5 to C4 and the transfer of a methyl group from C2 to C3 in the ring. Later, Cheng et al [141] studied the pyrolysis of 2-MF at temperatures of 900-1530 K and pressures of 30 and 760 Torr.…”