A detailed chemical kinetic model has been used to study dimethyl ether (DME) oxidation over a wide range of conditions. Experimental results obtained in a jet-stirred reactor (JSR) at I and 10 atm, 0.2 < 0 < 2.5, and 800 < T < 1300 K were modeled, in addition to those generated in a shock tube at 13 and 40 bar, 0 = 1.0 and 650 :5 T :5 1300 K. The JSR results are particularly valuable as they include concentration profiles of reactants, intermediates and products pertinent to the oxidation of DME. These data test the Idnetic model severely, as it must be able to predict the correct distribution and concentrations of intermediate and final products formed in the oxidation process. Additionally, the shock tube results are very useful, as they were taken at low temperatures and at high pressures, and thus undergo negative temperature dependence (NTC) behavior. This behavior is characteristic of the oxidation of saturated hydrocarbon fuels, (e.g. the primary reference fuels, n-heptane and iso- octane) under similar conditions. The numerical model consists of 78 chemical species and 336 chemical reactions. The thermodynamic properties of unknown species pertaining to DME oxidation were calculated using THERM.

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Wide range modeling study of dimethyl ether oxidation

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

Deactivation and regeneration of hybrid catalysts in the single-step synthesis of dimethyl ether from syngas and CO2

Burning velocities of dimethyl ether and air

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

High-temperature pyrolysis of dimethyl ether in shock waves

Pyrolysis and oxidation in fuel-rich and fuel-lean mixtures of dimethyl ether (DME) highly diluted with argon were studied behind reflected shock waves in the temperature range 950 - 1900 K at total pressures between 0.8 and 2.9 atm. The study was carried out using the following methods: l) time-resolved IR-laser absorption at 3.39 Jlm for DME decay and CH-compound formation rates, 2) time-resolved UV absorption at 216 nm for the CH3 radical formation rate, 3) time­ resolved UV absorption at 306.7 nm for the OH radical formation rate, 4) time-resolved IR emission at 4.24J1m for the C02 formation rate, and 5) a single-pulse technique for product yields. The pyrolysis and oxidation of DME, which were for very wide mixture compositions ranging from highly DME-rich to highly DME-lean, were modeled using a reaction mechanism with 178 reaction steps and 53 species including the most recent sub-mechanisms for formaldehyde, ketene, methane, acetylene, and ethylene oxidation. This and previously reported data were reproduced using this mechanism. The rate constant k5 = 4.5 x 10 14 exp (- 6.1 kcal/RT) cm 3 mor 1 s- 1 of reaction DME + OH -> CH30CH2 + H20 was evaluated.

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Masatsugu Yamane

Papers

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

High-temperature pyrolysis of dimethyl ether in shock waves

Shock-Tube and Modeling Study of Dimethyl Ether Pyrolysis and Oxidation