The atmospheric chemistry of Oxygenated fuel additives: t-Butyl alcohol, dimethyl ether, and methylt-butyl ether

✍ Scribed by S. M. Japar; T. J. Wallington; J. F. O. Richert; J. C. Ball

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 650 KB
• Volume: 22
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550221205

✦ Synopsis

The mechanisms for the C1-initiated and OH-initiated atmospheric oxidation of t-butyl alcohol (TBA), methyl t-butyl ether (MTBE), and dimethyl ether (DME) have been determined. For TBA the only products observed are equimolar amounts of HzCO and acetone, and its atmospheric oxidation can be represented by ( 7), ( 7)

The mechanism for the atmospheric oxidation of DME is also straight forward, with the only observable product being methyl formate,

The mechanism for the atmospheric oxidation of MTBE is more complex, with observable products being t-butyl formate (TBF) and HzCO. Evidence is presented also for the formation of 2-methoxy-2-methyl propanal (MMP), which is highly reactive and presumably oxidized to products. The atmospheric oxidation of MTBE can be represented by ( 9) and (lo), ( 9)

In terms of atmospheric reactivity, DME, TBA, and MTBE all compare favorably with methanol. In terms of rate of reaction in the atmosphere, DME, MTBE, and TBA are 1.4, 0.40, and 0.28 times as reactive as CH30H towards OH on a per carbon basis. With regard to chemistry, atmospheric oxidation of CHBOH yields highly reactive HzCO as the sole carboncontaining product. In contrast, only 25% of the carbon in TBA is converted to HzCO, with the balance yielding unreactive acetone. For DME, all the carbon is converted to methyl formate which is unreactive. Finally, for MTBE, 60% is converted to unreactive TBF while the remaining 40% produces highly reactive MMP.

Final assessment of the impact of these materials on the atmospheric reactivity of vehicle emissions requires the determination of their emissions rates under realistic operating conditions