Coupling nitrate electrochemical reduction and nitrite oxidation of ethanol for acetamide synthesis

TL;DR

A new electrochemical method combines nitrate reduction and ethanol oxidation to efficiently produce acetamide under mild conditions.

Contribution

A tandem electrolyzer system that couples cathodic and anodic reactions to enhance acetamide synthesis efficiency and yield.

Findings

The tandem system achieved a yield of 7.2 ± 0.3 mmol h⁻¹ at 2.4 V cell voltage.

The method is versatile, producing other amides like formamide and butyramide.

Techno-economic analysis shows production costs are competitive with traditional methods.

Abstract

Electrochemical acetamide synthesis under ambient conditions offers a sustainable route for converting waste nitrate into valuable chemicals. Conventional methods, limited to standalone reduction or oxidation processes, typically achieve low Faradaic efficiencies (<40%) and yields (<0.2 mmol h⁻¹ cm⁻²). Here, we present a tandem reaction system coupling cathodic reduction and anodic oxidation in a full-cell electrolyzer to enhance acetamide production. At the cathode, nitrate is first reduced to nitrite, which subsequently oxidizes ethanol to acetaldehyde. This acetaldehyde reacts in situ with electrogenerated ammonia to form α-aminoethanol. The intermediate is then transported to the anode, where it undergoes oxidation to yield acetamide. The reaction pathway is confirmed through proton nuclear magnetic resonance spectroscopy, revealing efficient acetamide synthesis with a yield of 7.2 ± 0.3 mmol h⁻¹ (0.45 ± 0.02 mmol h⁻¹ cm⁻²) at a cell voltage of 2.4 V. Furthermore, the strategy extends to other amides, such as formamide and butyramide, underscoring its versatility. Techno-economic analysis highlights the viability of this route, with estimated production costs competitive against conventional thermal processes.

Conventional amides electrosynthesis methods confine reactions to solely electrochemical reduction or oxidation processes, resulting in low amides yield rates. Here, the authors report a tandem electrolyzer that couples cathodic nitrate reduction with anodic ethanol oxidation to produce acetamide.

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