Work

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

Year: 2022

Type: article

Abstract: Previously, the oxidation of di- n -butyl ether (DBE) carried out in a jet-stirred reactor (JSR) and in a rapid compression machine (RCM) revealed that it proceeds similarly under both conditions (Belhadj et al, Combust. Flame 2020, 222, 133–144). Here, we extend that study to DBE oxidation in a motored homogeneous charge compression ignition engine, conditions under which this fuel has never been studied. Samples of exhaust gas were obtained by bubbling in acetonitrile maintained at 0 °C. The samples were analyzed using atmospheric pressure chemical ionization in positive and negative modes, high-resolution mass spectrometry (Orbitrap), and ultrahigh-pressure liquid chromatography. Flow injection analyses of samples before and after H/D exchange using D 2 O were also performed to verify the presence of isomeric products containing OH or OOH groups. Carbonyls were identified through derivatization with 2,4-dinitrophenylhydrazine. A large set of chemical products of the DBE cool flame were detected in the engine exhausts. They include hydroperoxides and diols (C 8 H 18 O 3 ), unsaturated diols or unsaturated hydroperoxides (C 8 H 16 O 3 ), keto hydroperoxides (C 4 H 8 O 3 and C 8 H 16 O 4 ), diketo ethers (C 8 H 14 O 3 ), olefinic diketo ethers (C 8 H 12 O 3 ), cyclic and keto ethers (C 8 H 16 O 2 ), and olefinic cyclic and keto ethers (C 8 H 14 O 2 ). Also, highly oxygenated chemicals, i.e., keto dihydroperoxides (C 8 H 16 O 6 ) resulting from three O 2 additions on radicals from the fuel, diketo hydroperoxides (C 8 H 14 O 5 ) resulting from decomposition of keto dihydroperoxides (C 8 H 16 O 6 ), in addition to other oxygenated intermediates i.e., hydroxy-DBE (C 8 H 18 O 2 ) and organic peroxides ROOR′ (C 16 H 34 O 4, C 11 H 24 O 3, C 11 H 22 O 3, and C 10 H 22 O 3 ), were observed in the engine exhausts. The present speciation results of the engine exhausts were compared to those obtained for samples of the oxidation of DBE in an RCM and a JSR. Despite the significant differences in physical experimental conditions, the present study indicates thata common oxidation mechanism proceeds in JSR, RCM, and a motored engine, leading to the formation of products having the same chemical formulas and retention times.

Source: Energy & Fuels

DOI: 10.1021/acs.energyfuels.2c00749