Kinetics of OH radical reactions with methane in the temperature range 295-660 K and with dimethyl ether and methyl-tert-butyl ether in the temperature range 295-618 K

The pulse laser photolysis/laser induced fluorescence (PLP-LIF) technique has been used to measure the rate constants of the reactions of OH radicals with dimethyl ether and methyl-tert-butyl ether. OH radicals were produced by photolysis of H2O2 at lambda = 266 nm. The photolysis cell was heated by a small electric furnaces in order to obtain information on the temperature dependency of the rate constants in the domain of 295-660 K. A preliminary study of the reaction of OH with methane was carried out to control the experimental setup. The Arrhenius expression obtained in the temperature range of 295-668 K, k(OH+CH4) = (5.65 +/- 0.49) x 10(-21)T(3.01) exp[-(959 +/- 36)/T], is in very good agreement with previous determinations (bimolecular rate constant units: cm(3) molecule(-1) s(-1); error limits +/- 2sigma). For the reactions of OH with ethers, the Arrhenius expressions derived from our own results are k(OH+DME)(295-618 K) = (3.02 +/- 0.10) x 10(-20)T(2.85) exp[(618 +/- 13)/T] and k(OH+MTBE)(297-616 K) = (6.59 +/- 0.43) x 10(-19)T(2.40) exp([(499 +/- 22)/T]. Combining these data with those from previous experimental studies allows us to derive Arrhenius expressions in larger temperature domains: k(OH+DME)(230-650 K) = (4.59 +/- 0.21) x 10(-19)T(2.41) exp[(476 +/- 14)/T] and k(OH+MTBE)(230-750 K) = (1.58 +/- 0.09) x 10(-20)T(2.93) exp([(716 +/- 18)/T].