Dimethyl Ether Oxidation at Elevated Temperatures (295−600 K)

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 109; no. 48; pp. 10940 - 10953
• Main Authors: Rosado-Reyes, Claudette M, Francisco, Joseph S, Szente, Joseph J, Maricq, M. Matti, Frøsig Østergaard, Lars
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 08-12-2005
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp054223t

Dimethyl ether (DME) has been proposed for use as an alternative fuel or additive in diesel engines and as a potential fuel in solid oxide fuel cells. The oxidation chemistry of DME is a key element in understanding its role in these applications. The reaction between methoxymethyl radicals and O2 has been examined over the temperature range 295−600 K and at pressures of 20−200 Torr. This reaction has two product pathways. The first produces methoxymethyl peroxy radicals, while the second produces OH radicals and formaldehyde molecules. Real-time kinetic measurements are made by transient infrared spectroscopy to monitor the yield of three main productsformaldehyde, methyl formate, and formic acidto determine the branching ratio for the CH3OCH2 + O2 reaction pathways. The temperature and pressure dependence of this reaction is described by a Lindemann and Arrhenius mechanism. The branching ratio is described by f = 1/(1 + A T[M]), where A T = (1. × 10-20) exp((1800 ± 400)/T) cm3 molecule-1. The temperature dependent rate constant of the methoxymethyl peroxy radical self-reaction is calculated from the kinetics of the formaldehyde and methyl formate product yields, k 4 = (3.0 ± 2.1) × 10-13 exp((700 ± 250)/T) cm3 molecule-1 s-1. The experimental and kinetics modeling results support a strong preference for the thermal decomposition of alkoxy radicals versus their reaction with O2 under our laboratory conditions. These characteristics of DME oxidation with respect to temperature and pressure might provide insight into optimizing solid oxide fuel cell operating conditions with DME in the presence of O2 to maximize power outputs.