Gas-Phase Selective Oxidation of Butenes in the C4 Fraction by Nitrous Oxide

Direct oxidation of n-butenes is the preferred but yet unrealized route to methyl ethyl ketone (MEK). At the same time, N2O is a promising selective oxidant for conversion of olefins mainly to ketones. In this work, we studied the possibility of producing MEK via the gas-phase noncatalytic oxidation with N2O of butene isomers in the C4 refinery stream from catalytic cracking. The oxidation was performed at 573-823 K and a pressure of up to 2 MPa. NMR and gas chromatography methods were used to identify the reaction products. It was shown that N2O selectively oxidizes only butenes in the C4 fraction to form nitrogen and carbonyl products, among which MEK is predominant. The reaction proceeds through the 1,3-dipolar cycloaddition of N2O to the C=C bond of butenes. The proposed method allows obtaining valuable oxygenates without the separation of the C4 fraction and opens a potential way for the rational utilization of waste N2O, a powerful greenhouse gas.