Dimethyl ether oxidation at elevated temperatures (295-600 K).
Dimethyl ether oxidation at elevated temperatures (295-600 K).
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DOI：
10.1021/jp054223t
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发表时间：
2005-11
期刊：
影响因子：
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通讯作者：
C. Rosado-Reyes;J. S. Francisco;J. Szente;M. Maricq;Lars Frøsig Østergaard
中科院分区：
文献类型：
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作者：
C. Rosado-Reyes;J. S. Francisco;J. Szente;M. Maricq;Lars Frøsig Østergaard
二甲醚（DME）已被提议用作柴油发动机中的替代燃料或添加剂以及用作固体氧化物燃料电池中的潜在燃料。DME的氧化化学是理解其在这些应用中的作用的关键要素。在295-600 K的温度范围和20-200 Torr的压力下，研究了甲氧基甲基自由基与O（2）之间的反应。该反应有两种产物途径。第一个产生甲氧基甲基过氧自由基，而第二个产生OH自由基和甲醛分子。通过瞬态红外光谱进行实时动力学测量，以监测三种主要产物-甲醛，甲酸甲酯和甲酸的产率，以确定CH（3）OCH（2）+ O（2）反应途径的分支比。该反应的温度和压力依赖性由Lindemann-Arrhenius机理描述。分支比由f = 1/（1 + A（T）[M]）描述，其中A（T）=（1.6（+2.4）（-1.0）× 10（-20））exp（（1800 +/-400）/T）cm（3）molecule（-1）。根据甲醛和甲酸甲酯产物产率的动力学计算了甲氧基甲基过氧自由基自反应的温度依赖性速率常数，k（4）=（3.0 +/- 2.1）× 10（-13）exp（（700 +/- 250）/T）cm（3）molecule（-1）s（-1）。实验和动力学模拟结果支持了强烈的偏好，热分解的烷氧基自由基与O（2）在我们的实验室条件下的反应。DME氧化相对于温度和压力的这些特性可以提供对在O（2）存在下使用DME优化固体氧化物燃料电池操作条件以最大化功率输出的见解。
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 O(2) 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 CH(3)OCH(2) + O(2) 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) = (1.6(+2.4)(-1.0) x 10(-20)) exp((1800 +/- 400)/T) cm(3) 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) x 10(-13) exp((700 +/- 250)/T) cm(3) 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 O(2) 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 O(2) to maximize power outputs.