The oxidation of propylene and isobutylene in barrier-discharge plasma in the presence of octane was studied. The possible reaction mechanism was considered.Recently, the interest in organic synthesis in electric discharges has been increasing. However, development of new technologies based on electric discharges is hindered by the lack of a sufficiently large body of data on the mechanisms and kinetics of conversion of organic compounds in plasma, which is, as a rule, caused by the low selectivity of the occurring reactions, tarring, and deep degradation of organic molecules.We have shown previously that oxidation of hydrocarbons belonging to various classes without formation of tars and products of complete oxidation is possible in a barrier discharge [1]. This is achieved by effective removal of reaction products from the zone of the barrier discharge with a hydrocarbon film formed by condensation of supersaturated vapor of a hydrocarbon on the cooled reactor walls. For example, oxidation of hexane, cyclohexane, and cumene mainly yields hydroxy and carbonyl compounds: alcohols, aldehydes, and ketones with the same number of carbon atoms as that in the starting compound. The product formed in oxidation of cyclohexene is epoxycyclohexane (62 wt %).It was shown in [2] that the selectivity of cyclohexene oxidation can be, in principle, controlled. The maximum yield of cyclohexene oxide was~72%. However, products of oxidation of light olefins are of greater importance for petrochemical synthesis.In this work we studied oxidation of propylene (PR) and isobutylene (IB) in a reactor with a barrier discharge.EXPERIMENTAL PR and IB were oxidized in the presence of octane to create a hydrocarbon film in which reaction products are dissolved and are thereby removed from the zone of the barrier discharge. A flow-through gasdischarge reactor of coaxial design was used. The experimental setup has been described in detail previously [1].The starting parameters of the process were as follows: flow rate of oxygen, olefin, and octane through the reactor 3.0, 0.6, and 6 0 10 33 l h 31 , respectively; temperature of the reactor walls 10oC; atmospheric pressure; amplitude of voltage pulses 12 kV; pulse repetition frequency 500 Hz; specific energy of the discharge 1.3 Wh l 31 .The liquid reaction products were analyzed by gas chromatography: heat-conductivity detector in the isothermal mode at 120oC; 1.2-m-long packed column with an inner diameter of 3 mm; sorbent Porapak-Q; carrier gas helium.The conversions and the composition of products formed in oxidation of PR and IB are listed in the table. It can be seen that the main reaction products are the corresponding epoxides. In contrast to the oxidation of cyclohexene, the oxidation of PR and IB is accompanied by degradation of the olefin molecule to give methanol and formaldehyde. At the same time, no CO, CO 2 , acids, or tarring products were found in the reaction products, which constitutes a fundamental difference between the results of this study and those of previous studies o...
