The photooxidation of methyl tertiary butyl ether

Abstract

Methyl tertiary butyl ether (MTBE) has been proposed and is being used as an additive to increase the octane of gasoline without the use of tetraethyl lead and alkylbenzenes. The present experiments have been performed to examine the kinetics and mechanisms of the atmospheric removal of MTBE. The kinetics of the reaction of OH with MTBE was examined by using a relative rate technique in which photolysis of methyl nitrite was used as the source of OH. With n‐butane as the reference compound a value of (2.99 ± 0.12) × 10−12 cm3 molecule−1 s−1 at a temperature of 298 K was obtained for the rate constant. The products (and product yields) for the OH reaction with MTBE in the presence of NOx were also determined and found to be t‐butyl formate (0.68 ± 0.05), methyl acetate (0.14 ± 0.02), acetone (0.026 ± 0.003), t‐butanol (0.062 ± 0.009), and formaldehyde (0.48 ± 0.05) in mols/mol MTBE converted. The OH rate constant for the major product formed, t‐butyl formate was also measured and found to be (7.37 ± 0.05) × 10−13 cm3 molecule−1 s−1. Mechanisms to rationalize the formation of the products are presented.

Atmospheric chemistry of di-tert-butyl ether: Rates and products of the reactions with chlorine atoms, hydroxyl radicals, and nitrate radicals

“…In accord with this expectation in studies of MTBE oxidation Smith et al [7] and Tuazon et al [8] report methyl acetate yields of 0.14 5 0.02 and 0.17 ? 0.02, respectively.…”

“…Thus, the yield of tert-butyl formate following the OH radical initiated oxidation of MTBE in air in the presence of NO has been reported to be 0.59 +-0.05 (61, 0.68 t 0.05 [7], and 0.76 t 0.07 [8]. While there is a disagreement as to the exact magnitude of the tert-butyl formate yield, there is a general consensus that this product is formed in a yield which is greater than 54%.…”

Kinetics and mechanism of the atmospheric oxidation of tertiary amyl methyl ether

“…Experiments to measure rate constants and yields of the reaction products of OH with TAME were conducted with an apparatus similar to that which has been described previously [6]. Irradiations were performed in 200-L reaction chambers constructed of 50-pm Teflon film.…”

Laboratory studies of the ·OH‐initiated photooxidation of ethyl‐n‐butyl ether and di‐n‐butyl ether

“…The hydroxyl radical attacks the ether by abstracting a hydrogen atom from primary or secondary alkyl groups. Past studies indicate that the hydrocarbon radical that is formed from this reaction is then oxidized and reduced, forming an alkoxy radical [1,3,11,15,16]. This alkoxy radical can then decompose, react with atmospheric oxygen, or isomerize to produce another organic compound.…”

“…This alkoxy radical can then decompose, react with atmospheric oxygen, or isomerize to produce another organic compound. However, previous ether product studies were conducted on relatively short-chain molecules (e.g., methyl tertiary-butyl ether (MTBE), tertiary amyl methyl ether (TAME), di-isopropyl ether (DIPE), ethyl tertiary-butyl ether (ETBE), diethyl ether (DEE), methyl-n-butyl ether (MNBE), and di-n-propyl ether (DNPE) [1,3,11,15,16,17,18]). 1,5-Hydrogen atom abstraction is not likely to occur with these ethers (with the exception of DNPE) because their carbon chains are too short or the tertiary carbon group presents too much steric hindrance for hydrogen atom abstraction to take place.…”