Experimental and modeling study of the pyrolysis and combustion of 2-methyl-tetrahydrofuran

Abstract

Saturated cyclic ethers are being proposed as next-generation bio-derived fuels. However, their pyrolysis and combustion chemistry has not been well established. In this work, the pyrolysis and combustion chemistry of 2-methyl-tetrahydrofuran (MTHF) was investigated through experiments and detailed kinetic modeling. Pyrolysis experiments were performed in a dedicated plug flow reactor at 170 kPa, temperatures between 900 and 1100K and a N 2 (diluent) to MTHF molar ratio of 10. The combustion chemistry of MTHF was investigated by measuring mole fraction profiles of stable species in premixed flat flames at 6.7 kPa and equivalence ratios 0.7, 1.0 and 1.3 and by determining laminar burning velocities of MTHF/air flat flames with unburned gas temperatures of 298, 358 and 398K and equivalence ratios between 0.6 and 1.6. Furthermore, a kinetic model for pyrolysis and combustion of MTHF was developed, which contains a detailed description of the reactions of MTHF and its derived radicals with the aid of new high-level theoretical calculations. Model calculated mole fraction profiles and laminar burning velocities are in relatively good agreement with the obtained experimental data. At the applied pyrolysis conditions, unimolecular decomposition of MTHF by scission of the methyl group and concerted ring opening to 4-penten-1-ol dominates over scission of the ring bonds; the latter reactions were significant in tetrahydrofuran pyrolysis. MTHF is mainly consumed by hydrogen abstraction reactions. Subsequent decomposition of the resulting radicals by β-scission results in the observed product spectrum including small alkenes, formaldehyde, acetaldehyde and ketene. In the studied flames, unimolecular ring opening of MTHF is insignificant and consumption of MTHF through radical chemistry dominates. Recombination of 2-oxo-ethyl and 2-oxo-propyl, primary radicals in MTHF decomposition, with hydrogen atoms and carboncentered radicals results in a wide range of oxygenated molecules.

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

“…However, the quantitative agreement is poor for most species. Then, De Bruycker et al [146] presented another 2-MTHF kinetic model, developed with the help of new advanced theoretical calculations. The authors segment the new model into three main mechanisms: a primary mechanism, covering the oxidation and pyrolysis of 2-MTHF and its radicals; a base mechanism, capturing the oxidations and pyrolysis of small oxygenates and hydrocarbons; and a secondary mechanism, focusing on 2-MTHF decomposition products.…”

“…The pyrolysis of 2-MTHF was recently investigated by De Bruycker [146] in a plug flow reactor at a pressure of 170 kPa, temperatures of 900-1100 K and an N 2 /2-MTHF molar ratio of 10. The results indicated that the main pathway for decomposition is by cleavage of the CH 3 group and ring opening to 4-penten-1-ol.…”

“…The characterization of flame behavior of tetrahydrofurans was also carried out in a few studies [146,223]. Recently, the first effort on 2-MTHF flames was presented by De Bruycker et al [146], who measured mole fraction profiles of some stable species in 2-MTHF/air premixed flat flames at a pressure of 6.7 kPa and equivalence ratios of 0.7-1.3, as well as laminar burning velocities of flat flames of 2-MTHF/air at initial temperatures of 298-398 K and equivalence ratios of 0.6-1.6, as shown in Figure 9.…”

“…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].…”

“…Chemical kinetic models of tetrahydrofurans have been proposed [27,146,157,158]. The first 2-MTHF model by Moshammer et al [27] was developed based on mole fraction profiles of products, reactants and a number of intermediate species including radicals obtained experimentally for premixed low-pressure 2-MTHF flames at an equivalence ratio of 1.7.…”