Towards a Comprehensive Characterization of the Low-Temperature Autoxidation of Di-n-Butyl Ether

Abstract

In the present study, we investigated the oxidation of 2500 ppm of di-n-butyl ether under fuel-rich conditions (φ = 2) at low temperatures (460–780 K), a residence time of 1 s, and 10 atm. The experiments were carried out in a fused silica jet-stirred reactor. Oxidation products were identified and quantified in gas samples by gas chromatography and Fourier transform infrared spectrometry. Samples were also trapped through bubbling in cool acetonitrile for high-pressure liquid chromatography (HPLC) analyses. 2,4-dinitro-phenylhydrazine was used to derivatize carbonyl products and distinguish them from other isomers. HPLC coupled to high resolution mass spectrometry (Orbitrap Q-Exactive®) allowed for the detection of oxygenated species never observed before, i.e., low-temperature oxidation products (C8H12O4,6, C8H16O3,5,7, and C8H18O2,5) and species that are more specific products of atmospheric oxidation, i.e., C16H34O4, C11H24O3, C11H22O3, and C10H22O3. Flow injection analyses indicated the presence of high molecular weight oxygenated products (m/z > 550). These results highlight the strong similitude in terms of classes of oxidation products of combustion and atmospheric oxidation, and through autoxidation processes. A kinetic modeling of the present experiments indicated some discrepancies with the present data.

Experimental and kinetic modeling study of n-pentane oxidation at 10 atm, Detection of complex low-temperature products by Q-Exactive Orbitrap

“…C 5 H 8 O 2 also corresponds to other isomers like cyclic ether with a carbonyl group (2methyltetrahydrofuran-3-one (2-Me-THF-3-one) known as coffee furanone, and tetrahydropyran-3one), but we had no standards to identify them and confirm their formation under these experimental conditions (Table 1). More oxygenated molecules with one or more hydroperoxy groups are formed during n-pentane oxidation, as already reported in recent studies the oxidation of other fuels (alkanes, ethers) [17][18][19][20][21][22].…”

“…Low-temperature oxidation intermediates are formed by combustion reactions requiring oxygen addition onto fuel's radicals followed by different chemical reactions such as isomerization, intramolecular rearrangement and molecular decomposition. As observed previously for heavier hydrocarbons and oxygenates (esters, aldehydes, alcohols, ethers), oxidation can proceed much further than previously reported in combustion studies [12][13][14][15][16][17][18][19][20][21][22][23]. In our recent combustion works, we could observe the formation of highly oxygenated molecules (HOMs) resulting from more than two oxygen additions on fuels' radicals [17][18][19][20][21][22][23].…”

“…As observed previously for heavier hydrocarbons and oxygenates (esters, aldehydes, alcohols, ethers), oxidation can proceed much further than previously reported in combustion studies [12][13][14][15][16][17][18][19][20][21][22][23]. In our recent combustion works, we could observe the formation of highly oxygenated molecules (HOMs) resulting from more than two oxygen additions on fuels' radicals [17][18][19][20][21][22][23]. Interestingly, HOMs produced through multiple O 2 addition on fuel's radicals and internal H-shifts, are considered important chemicals in atmospheric chemistry, especially for the evolution and growth of secondary organic aerosols (SOA) [24][25][26].…”

“…As in our previous works [17][18][19][20][21][22]27], several analytical chemical procedures were applied to improve the detection of species or to reveal specific functional groups. For example, 2,4dinitrophenylhydrazine (2, S2.…”

Low-Temperature Oxidation of Di-n-Butyl Ether in a Motored Homogeneous Charge Compression Ignition (HCCI) Engine: Comparison of Characteristic Products with RCM and JSR Speciation by Orbitrap

“…C 8 H 16 O 4 and C 4 H 8 O 3 keto hydroperoxides (KHPs) are formed during the low-temperature oxidation of di- n -butyl ether. , C 8 H 16 O 4 keto hydroperoxides are formed through the following well-accepted combustion chemistry reaction pathways: DBE + X • (X = • OH, H • , O • , HO 2 • , O 2 , ...) → R • + XH, R • + O 2 → ROO • → • QOOH (H-shift), and • QOOH + O 2 → • OOQOOH → HOOQ′O + • OH. With regard to C 4 H 8 O 3 keto hydroperoxides, their production can occur through the following sequence of reactions: fuel + X • → R • + XH, R • + O 2 → ROO • → • QOOH (H-shift) → decomposition of • QOOH → carbonyl compound + R′OO • → • Q′OOH (H-shift), and • Q’OOH + O 2 → • OOQ′OOH → HOOQ′′O + • OH.…”