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

Abstract

Direct oxidation of n-butenes is the preferred but yet unrealized route to methyl ethyl ketone (MEK). At the same time, N 2 O 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 N 2 O 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 N 2 O 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 N 2 O 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 N 2 O, a powerful greenhouse gas.

Liquid-Phase Oxidation of Butene–Butane Mixtures with N2O to Ketones and Aldehydes

“…Earlier, we investigated the gas-phase oxidation of a similar BBM with nitrous oxide at 350–500 °C and a pressure of 0.5–2 MPa . In this case, the highest butenes conversion of 40.5% was achieved at 450 °C, a pressure of 2 MPa, and the BBM/N 2 O molar ratio of 7:3.…”

“…Note that in the gas-phase oxidation, non-flammable BBM-N 2 O mixtures containing at least 70 mol % BBM should be used for safe operation. 49 An important feature of the liquidphase process is the ability to perform the oxidation at a much lower BBM/N 2 O molar ratio of 1:1.…”

“…The GC−MS analysis was carried out on a 7000B GC/MS (Agilent) instrument equipped with a HP5ms capillary column (30 m × 0.25 mm, heating (3 °C/min) from 50 to 300 °C, helium carrier gas). The experimental details of 13 C and 1 H NMR analysis are given elsewhere 49 (see also Supporting Information, Figures S1−S4).…”

“…These reactions can occur in the liquid phase below 300 °C ,,− or in the gas phase at higher temperatures. ,− For instance, the selectivity of the liquid-phase oxidation of cycloolefins with N 2 O to corresponding cyclic ketones attains 95–99%. , …”

Photocatalytic Oxygen Transfer as an Innovative Route for N2O Upgrading**

“…110 years [1] . Industries generating this waste, such as in the production of adipic acid, currently burn this gas in flares, [2] but in the drive towards more sustainable chemical processes, this GEG could be upgraded as an oxygen source to produce marketable chemicals, only generating dinitrogen (N 2 ) as a benign co‐product.…”