Impact of Methanol and Butanol on Soot Formation in Gasoline Surrogate Pyrolysis: A Shock-Tube Study.

The influence of methanol and butanol on soot formation during the pyrolysis of a toluene primary reference fuel mixture with a research octane number (RON) of 91 (TPRF91) was investigated by conducting shock-tube experiments. The TPRF91 mixture contained 17 mol % -heptane, 29 mol % -octane, and 54 mol % toluene. To assess the contribution of individual fuel compounds on soot formation during TPRF91 pyrolysis, the pyrolysis of argon diluted (1) toluene, (2) -octane, and (3) -heptane mixtures were also studied.

Thermochemistry of Oxygen-Containing Organosilane Radicals and Uncertainty Estimations of Organosilane Group-Additivity Values.

Si-C-H-O-containing radicals are important intermediates during the combustion and pyrolysis of precursors applied for the gas-phase synthesis of silica nanoparticles. Despite the industrial importance of silica nanoparticles, a comprehensive thermodynamics database of organosilane species is still missing. This work presents thermochemical data of 91 Si-C-H-O radical species.

Theoretical, Experimental, and Modeling Study of the Reaction of Hydrogen Atoms with 1- and 2-Pentene.

Alkyl radicals are prominent in combustion chemistry as they are formed by hydrocarbon decomposition or from a radical attack on hydrocarbons. Accurate determinations of the thermochemistry and kinetics of their unimolecular isomerization and decomposition reactions and related addition reactions of alkenes are therefore important in simulating the combustion chemistry of virtually all hydrocarbon fuels. In this work, a comprehensive potential energy surface (PES) for Ḣ-atom addition to and abstraction from 1- and 2-pentene, and the subsequent C-C and C-H β-scission reactions, and H-atom transfer reactions has been considered.

High-Temperature Unimolecular Decomposition of Diethyl Ether: Shock-Tube and Theory Studies.

The unimolecular decomposition of diethyl ether (DEE; CHOCH) is considered to be initiated via a molecular elimination and a C-O and a C-C bond fission step: CHOCH → CH + CHOH (1), CHOCH → CH + CHO (2), and CHOCH → CH + CHOCH (3). In this work, two shock-tube facilities were used to investigate these reactions via (a) time-resolved H-atom concentration measurements by H-ARAS (atomic resonance absorption spectrometry), (b) time-resolved DEE-concentration measurements by high repetition-rate time-of-flight mass spectrometry (HRR-TOF-MS), and (c) product-composition measurements via gas chromatography/MS (GC/MS) after quenching the test gas. The experiments were conducted at temperatures ranging from 1054 to 1505 K and at pressures between 1.

Supersonic jet spectroscopy of parent hemiporphycene: Structural assignment and vibrational analysis for S and S electronic states.

Hemiporphycene (HPc), a constitutional isomer of porphyrin, is studied under supersonic expansion conditions by means of laser-induced fluorescence, visible-visible hole-burning experiments, single vibronic level fluorescence techniques, and quantum chemical calculations. Only one form of jet-cooled HPc is observed, in contrast to solution studies that evidence a mixture of two tautomeric forms separated in energy by ∼1 kcal/mol. Reliable structural assignment is provided by simulating absorption and emission patterns at the density functional theory and time-dependent density functional theory levels of theory.

Direct Measurement of High-Temperature Rate Constants of the Thermal Decomposition of Dimethoxymethane, a Shock Tube and Modeling Study.

Shock-tube experiments have been performed to investigate the thermal decomposition of the oxygenated hydrocarbon dimethoxymethane (DMM; CHOCHOCH). The primary initial reaction channels of DMM decomposition are considered to be the two bond fissions: CHOCHOCH → CHO + CHOCH (1) and CHOCHOCH → CH + OCHOCH (2). In the present work, two shock-tube facilities and three different detection techniques have been combined: Behind reflected shock waves, we have carried out time-resolved measurements of (i) the formation of H atoms using the highly sensitive H-ARAS (Atomic Resonance Absorption Spectrometry) technique and (ii) the depletion of the DMM reactant by high-repetition-rate time-of-flight mass spectrometry (HRR-TOF-MS).

High-Temperature Rate Constants for the Reaction of Hydrogen Atoms with Tetramethoxysilane and Reactivity Analogies between Silanes and Oxygenated Hydrocarbons.

The shock-tube technique has been used to investigate the H-abstraction reaction H + Si(OCH) → H + Si(OCH)(OCH) behind reflected shock waves. CHI was used as a thermal in situ source for H atoms. The experiments covered a temperature range of 1111-1238 K, and pressures of 1.

Supersonic Jet Spectroscopy and Density Functional Theory Study of Isomeric Diazines: 1,4- and 1,8-Diazatriphenylene. Why Do They Differ So Deeply?

We report on laser-induced fluorescence excitation and dispersed fluorescence spectra of two isomeric compounds: 1,4- and 1,8-diazatriphenylene (1,4- and 1,8-DAT) isolated in supersonic molecular jets, and their 1:1 complexes with protic solvents. We found that the ground and excited state vibronic patterns of bare 1,4-DAT differ significantly from those of 1,8-DAT, and those of the complexes of both isomers. A marked activity of several out-of-plane vibrations in 1,4-DAT and the symptoms of the distortion of the S excited molecule were diagnosed from the vibronic spectra, whereas planar structures were predicted for 1,8-DAT in S and S states.