Direct and relative rate coefficients for the gas-phase reaction of OH radicals with 2-methyltetrahydrofuran at room temperature

Abstract

2-methyltetrahydrofuran (2-MTHF) is a renewable green solvent, a platform molecule for organic syntheses and a potential automotive fuel or fuel additive that can be produced efficiently from lignocellulosic biomass. Its reaction with OH radicals is important concerning both of its atmospheric fate and combustion. Kinetics of the overall reaction OH + 2-MTHF → products (1) were studied at room temperature (T = 298 ± 1 K) using both direct and relative kinetic methods. The low pressure fast discharge flow (DF) experiments coupled with resonance fluorescence (RF) detection of OH have provided the direct rate coefficient of k 1 (298 K, 2.64 mbar He) = (1.21 ± 0.14 (±2σ)) × 10 -11 cm 3 molecule -1 s -1 . The relative-rate experiments (RR) with gas-chromatographic (GC) analysis were performed at higher pressure in synthetic air using the reaction OH + cyclohexane (c-C 6 H 12 ) → products (2) as reference. The determined rate coefficient ratio k 1 /k 2 = 3.80 ± 0.17 (±2σ) has been converted to k 1 (298 K, 1030 mbar air) = (2.65 ± 0.55 (±2σ)) × 10 -11 cm 3 molecule -1 s -1 . This k 1 value agrees reasonably well with the only other rate coefficient reported which was determined also at higher pressures. Comparison with the DF result indicates a possible pressure dependence of the reaction. Impact of 2-MTHF on the chemistry of the atmosphere has been briefly discussed.

An Ab Initio RRKM-Based Master Equation Study for Kinetics of OH-Initiated Oxidation of 2-Methyltetrahydrofuran and Its Implications in Kinetic Modeling

“…The reactions of 2MTHF with O 3 and NO 3 radicals should result in a negligibly slow depletion of 2MTHF. Recently, the experimental work of Illés et al [17] reinforced the earlier reports of Wallington et al [16] for the rate coefficient of the 2MTHF + OH reaction. Illés et al [17] used the low-pressure fast discharge flow (DF) experiments coupled with resonance fluorescence detection of OH to directly measure a rate coefficient of k(298 K, 2.64 bar He) = (1.21 ± 0.14) × 10 −11 cm 3 /molecule/s.…”

“…Recently, the experimental work of Illés et al [17] reinforced the earlier reports of Wallington et al [16] for the rate coefficient of the 2MTHF + OH reaction. Illés et al [17] used the low-pressure fast discharge flow (DF) experiments coupled with resonance fluorescence detection of OH to directly measure a rate coefficient of k(298 K, 2.64 bar He) = (1.21 ± 0.14) × 10 −11 cm 3 /molecule/s. Their additional experiments using the relative-rate/gas-chromatographic method yielded the rate coefficient k(298 K, 1030 mbar air) = (2.65 ± 0.55) × 10 −11 cm 3 /molecule/s.…”

Atmospheric breakdown chemistry of the new green solvent 2,2,5,5-tetramethyloxolane via gas-phase reactions with OH and Cl radicals

“…We therefore conclude that, at ambient temperature, OH reacts with TMO considerably more slowly than with other oxolanes, e.g. : oxolane (tetrahydrofuran) k = 1.7×10 -11 cm 3 molecule -1 s -1 (Moriarty et al, 2003); 2-methyloxolane, k = 2.65×10 -11 cm 3 molecule -1 s -1 (Illes et al, 2016); and 2,5-dimethyloxolane for which only data for the reaction with isotopicallylabelled OD is available and where k = 4.6 × 10 -11 cm 3 molecule -1 s -1 (Andersen et al, 2016). That the measured ambient temperature k1 values determined in this work were indeed anomalously small is further confirmed by calculations using the most up-to-date structure activity relationship from Jenkin et al (2018) which may be used to predict k1(298 K) = 9.1 × 10 -12 cm 3 molecule -1 s -1 .…”

Atmospheric breakdown chemistry of the new “green” solvent 2,2,5,5-tetramethyloxolane via gas-phase reactions with OH and Cl radicals

“…We therefore conclude that, at ambient temperature, OH reacts with TMO considerably more slowly than with other oxolanes, e.g. oxolane (tetrahydrofuran) k = 1.7 × 10 −11 cm 3 molecule −1 s −1 (Moriarty et al, 2003); 2-methyloxolane, k = 2.65 × 10 −11 cm 3 molecule −1 s −1 (Illes et al, 2016); and 2,5-dimethyloxolane for which only data for the reaction with isotopically labelled OD are available and where k = 4.6 × 10 −11 cm 3 molecule −1 s −1 (Andersen et al, 2016). That the measured ambienttemperature k 1 values determined in this work were indeed anomalously small is further confirmed by calculations using the most up-to-date structure-activity relationship (SAR) from Jenkin et al (2018), which may be used to predict k 1 (298 K) = 9.1 × 10 −12 cm 3 molecule −1 s −1 and identifies in Reaction (R1a) the preferred H-abstraction route with a branching ratio of 80 %.…”