A detailed chemical kinetic mechanism has been developed to describe the oxidation of small hydrocarbon and oxygenated hydrocarbon species. The reactivity of these small fuels and intermediates is of critical importance in understanding and accurately describing the combustion characteristics, such as ignition delay time, flame speed, and emissions of practical fuels. The chosen rate expressions have been assembled through critical evaluation of the literature, with minimum optimization performed. The mechanism has been validated over a wide range of initial conditions and experimental devices, including flow reactor, shock tube, jet-stirred reactor, and flame studies. The current mechanism contains accurate kinetic descriptions for saturated and unsaturated hydrocarbons, namely methane, ethane, ethylene, and acetylene, and oxygenated species; formaldehyde, methanol, acetaldehyde, and ethanol.

A Hierarchical and Comparative Kinetic Modeling Study of C1 − C2 Hydrocarbon and Oxygenated Fuels

The C2H5• + O2 reaction, central to ethane oxidation and thus of fundamental importance to hydrocarbon combustion chemistry, has been examined in detail via highly sophisticated electronic structure methods. The geometries, energies, and harmonic vibrational frequencies of the reactants, transition states, intermediates, and products for the reaction of the ethyl radical (X 2A‘) with O2 (X 3 , a 1Δg) have been investigated using the CCSD and CCSD(T) ab initio methods with basis sets ranging in quality from double-zeta plus polarization (DZP) to triple-zeta plus double polarization with f functions (TZ2Pf). Five mechanisms (M1−M5) involving the ground-state reactants are introduced within the context of previous experimental and theoretical studies. In this work, each mechanism is systematically explored, giving the following overall 0 K activation energies with respect to ground-state reactants, Ea(0 K), at our best level of theory:  (M1) direct hydrogen abstraction from the ethyl radical by O2 to give e...

The C2H5 + O2 Reaction Mechanism: High-Level ab Initio Characterizations

Detailed chemical kinetic models for the combustion of hydrocarbon fuels

Progress in detailed kinetic modeling of the combustion of oxygenated components of biofuels.

Ethanol dehydration was investigated over commercial H-FER, H-MFI, H-MOR, H-BEA, H-Y and H-USY zeolite samples, and alumina and silica alumina for comparison. The catalysts were characterized using FT-IR spectroscopy of the surface OH groups and of adsorbed CO and pyridine. UV–vis, Raman and TG-DTA were applied to characterize coke, formed more on H-MOR and H-BEA. H-zeolites are definitely more active than silica alumina and alumina on catalyst weight base. The H-MOR sample is the most active but the H-MFI samples with Si/Al 2 ratios 280 and 50 show higher reaction rates per Al ion, H-FER and faujasites show highest ethylene yield (99.9% at 573 K). At lower temperature and higher space velocities, diethyl ether is formed with high yield (>70% at 453–473 K on H-BEA and H-MFI (50)). Overconversion of ethylene mainly to aromatics is observed on H-MFI (50). The different behaviour of protonic zeolites can predominantly be explained by confinement effects on the different zeolite cavities.

Dehydration of ethanol over zeolites, silica alumina and alumina: Lewis acidity, Brønsted acidity and confinement effects

The pyrolysis and oxidation of diethyl ether (DEE) has been studied at pressures from 1 to 4 atm and temperatures of 900−1900 K behind reflected shock waves. A variety of spectroscopic diagnostics have been used, including time-resolved infrared absorption at 3.39 μm and time-resolved ultraviolet emission at 431 nm and absorption at 306.7 nm. In addition, a single-pulse shock tube was used to measure reactant, intermediate, and product species profiles by GC samplings at different reaction times varying from 1.2 to 1.8 ms. A detailed chemical kinetic model comprising 751 reactions involving 148 species was assembled and tested against the experiments with generally good agreement. In the early stages of reaction the unimolecular decomposition and hydrogen atom abstraction of DEE and the decomposition of the ethoxy radical have the largest influence. In separate experiments at 1.9 atm and 1340 K, it is shown that DEE inhibits the reactivity of an equimolar mixture of hydrogen and oxygen (1% of each).

A Multiple Shock Tube and Chemical Kinetic Modeling Study of Diethyl Ether Pyrolysis and Oxidation

Pyrolysis and oxidation of acetaldehyde were studied behind reflected shock waves in the temperature range 1000–1700 K at total pressures between 1.2 and 2.8 atm. The study was carried out using the following methods, (1) time-resolved IR-laser absorption at 3.39 μm for acetaldehyde decay and CH-compound formation rates, (2) time-resolved UV absorption at 200 nm for CH2CO and C2H4 product formation rates, (3) time-resolved UV absorption at 216 nm for CH3 formation rates, (4) time-resolved UV absorption at 306.7 nm for OH radical formation rate, (5) time-resolved IR emission at 4.24 μm for the CO2 formation rate, (6) time-resolved IR emission at 4.68 μm for the CO and CH2CO formation rate, and (7) a single-pulse technique for product yields. From a computer-simulation study, a 178-reaction mechanism that could satisfactorily model all of our data was constructed using new reactions, CH3CHO (+M) → CH4 + CO (+M), CH3CHO (+M) → CH2CO + H2(+M), H + CH3CHO → CH2CHO + H2, CH3 + CH3CHO → CH2CHO + CH4, O2 + CH3CHO → CH2CHO + HO2, O + CH3CHO → CH2CHO + OH, OH + CH3CHO → CH2CHO + H2O, HO2 + CH3CHO → CH2CHO + H2O2, having assumed or evaluated rate constants. The submechanisms of methane, ethylene, ethane, formaldehyde, and ketene were found to play an important role in acetaldehyde oxidation. © 2007 Wiley Periodicals, Inc. 40: 73–102, 2008

Shock-tube and modeling study of acetaldehyde pyrolysis and oxidation

Shock-tube and modeling study of ethane pyrolysis and oxidation

Pyrolysis and oxidation of ethyl methyl ether (EME) were studied behind reflected shock waves in the temperature range 900–1750 K at total pressures between 0.9 and 3.1 atm. The study was carried out using following methods, (1) time-resolved IR-laser absorption at 3.39 μm for EME decay and CH-compound formation rates, (2) time-resolved UV absorption at 216 nm for mainly CH 3 radical formation rate, (3) time-resolved UV absorption at 306.7 nm for OH radical formation rate, (4) time-resolved IR emission at 4.24 μm for CO 2 formation rate and (5) a single-pulse technique for product yields. The pyrolysis and oxidation of EME were modeled using a reaction mechanism including the sub-mechanisms for methane, acetylene, ethylene, ethane, formaldehyde, acetaldehyde and ketene oxidation. The reaction mechanism used in this study could reproduce almost all of experimental results. The sub-mechanisms of methane, ethylene, ethane, formaldehyde, and acetaldehyde were found to play an important role in EME oxidation.

Hiroki Hoshikawa

Papers

A Multiple Shock Tube and Chemical Kinetic Modeling Study of Diethyl Ether Pyrolysis and Oxidation

Shock-tube and modeling study of acetaldehyde pyrolysis and oxidation

Shock-tube and modeling study of ethane pyrolysis and oxidation

Shock-tube and modeling study of ethyl methyl ether pyrolysis and oxidation