title: Investigation of the photochemical reactivity of soot particles derived from biofuels toward NO2. A kinetic and product study.
abstract: In the current study, the heterogeneous reaction of NO2 with soot and biosoot surfaces was investigated in the dark and under illumination relevant to atmospheric conditions (J(NO2) = 0.012 s(-1)). A flat-flame burner was used for preparation and collection of soot samples from premixed flames of liquid fuels. The biofuels were prepared by mixing 20% v/v of (i) 1-butanol (CH3(CH2)3OH), (ii) methyl octanoate (CH3(CH2)6COOCH3), (iii) anhydrous diethyl carbonate (C2H5O)2CO and (iv) 2,5 dimethyl furan (CH3)2C4H2O additive compounds in conventional kerosene fuel (JetA-1). Experiments were performed at 293 K using a low-pressure flow tube reactor (P = 9 Torr) coupled to a quadrupole mass spectrometer. The initial and steady-state uptake coefficients, γ0 and γ(ss), respectively, as well as the surface coverage, N(s), were measured under dry and humid conditions. Furthermore, the branching ratios of the gas-phase products NO (∼80-100%) and HONO (<20%) were determined. Soot from JetA-1/2,5-dimethyl furan was the most reactive [γ0 = (29.1 ± 5.8) × 10(-6), γ(ss)(dry) = (9.09 ± 1.82) × 10(-7) and γ(ss)(5.5%RH) = (14.0 ± 2.8)(-7)] while soot from JetA-1/1-butanol [γ0 = (2.72 ± 0.544) × 10(-6), γ(ss)(dry) = (4.57 ± 0.914) × 10(-7), and γ(ss)(5.5%RH) = (3.64 ± 0.728) × 10(-7)] and JetA-1/diethyl carbonate [γ0 = (2.99 ± 0.598) × 10(-6), γ(ss)(dry) = (3.99 ± 0.798) × 10(-7), and γ(ss)(5.5%RH) = (4.80 ± 0.960) × 10(-7)] were less reactive. To correlate the chemical reactivity with the physicochemical properties of the soot samples, their chemical composition was analyzed employing Raman spectroscopy, NMR, and high-performance liquid chromatography. In addition, the Brunauer-Emmett-Teller adsorption isotherms and the particle size distributions were determined employing a Quantachrome Nova 2200e gas sorption analyzer. The analysis of the results showed that factors such as (i) soot mass collection rate, (ii) porosity of the particles formed, (iii) aromatic fraction, and (iv) pre-existence of nitro-containing species in soot samples (formed during the combustion process) can be used as indicators of soot reactivity with NO2.
authors: Institute de Combustion, Aérothermique, Réactivité et Environnement (ICARE)-CNRS, 1C Avenue de la Recherche Scientifique, 45071, Orléans, France.
authors: Manolis N
authors: MN
authors: Romanías
authors: Philippe
authors: P
authors: Dagaut
authors: Yuri
authors: Y
authors: Bedjanian
authors: Auréa
authors: A
authors: Andrade-Eiroa
authors: Roya
authors: R
authors: Shahla
authors: Karafas S
authors: KS
authors: Emmanouil
authors: Vassileios C
authors: VC
authors: Papadimitriou
authors: Apostolos
authors: A
authors: Spyros
mesh_terms: D056804:Biofuels; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D009585:Nitrogen Dioxide / Q000737:chemistry*; D055668:Photochemical Processes; D016062:Porosity; D053260:Soot / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D056804:Biofuels; D053260:Soot; D009585:Nitrogen Dioxide