REACTION OF THE NITRATE RADICAL WITH SOME POTENTIAL AUTOMOTIVE FUEL ADDITIVES - A KINETIC AND MECHANISTIC STUDY

Rate coefficients for the reaction of NO3 with ethyl tert-butyl ether (ETBE), diisopropyl ether (DIPE), and tert-amyl methyl ether (TAME) ha ve been determined. Absolute rates were measured at temperatures betwe en 257 and 367 K using the fast flow-discharge (FFD) technique. Relati ve rate experiments were also performed at 295 K in a reactor equipped with White optics and using FTIR spectroscopy to follow the reactions . Rate data from FFD experiments can be presented as follows: k(ETBE) = (2.48 +/- 0.78) X 10(-12) exp [-(1613 +/- 542)/T], k(DIPE) = (2.02 /- 0.35) X 10(-12) exp [-(1759 +/- 301)/T], and k(TAME) = (1.21 +/- 0. 22) X 10(-12) exp [-(1874 +/- 304)/T] (in units of cm(3) molecule(-1) s(-1)). The rate coefficients at room temperature from the FFD experim ents are in goad agreement with the corresponding rate coefficients fr om the relative rate experiments. Products from simulated atmospheric oxidation of the investigated ethers, initiated by the reaction with t he nitrate radical, were identified using FTIR spectroscopy. The degra dation of ETBE results in tert-butyl formate, tert-butyl acetate, form aldehyde, and methyl nitrate, that of DIPE in acetone, isopropyl nitra te, isopropyl acetate, and formaldehyde, and that of TAME in tert-amyl formate, formaldehyde, and tert-amyl nitrate.