Electrochemically Generated Copper Carbonyl for Selective Dimethyl Carbonate Synthesis

Abstract

Development of electrochemical synthesis routes for high-value chemicals could pave the way for a sustainable chemical industry based on electricity. Herein, the electrochemical synthesis of the industrially relevant and environmentally benign reagent, dimethyl carbonate (DMC), is investigated. By utilizing a combination of electrochemical techniques, in situ infrared spectroscopy, and headspace-gas chromatography−mass spectrometry we show production and spectroelectrochemical evidence for the synthesis of DMC via an electrochemically generated copper carbonyl species. The formation of the copper carbonyl has close to 100% current efficiency, in the applied potential range of 0.1−0.4 V vs SCE. Subsequent formation of DMC occurs with a slow reaction time on the order of 30− 40 days. Relative to potential coproducts, the reaction is highly selective for DMC. Optimization of the reaction may lead to a viable method of DMC production.

Electrochemical Approaches to Carbonylative Coupling Reactions

“…The investigation of the reaction mechanism (through Fourier-transform infrared spectroscopy, constant potential electrolysis, and HS-GS-MS technology) showed that Cu was first oxidized on the electrode surface to generate copper carbonyl and then reacted with methoxy to generate DMC. [32] Compared with Pd and Cu, the biggest preponderance of Au is that it has higher selectivity to the dicarbonyl product of methanol electrochemical carbonyl coupling: dimethyl oxalate (DMO). Yamanaka et al found that besides DMC, DMO could also be detected when using Au or Au/C as the anode.…”

Electrocatalytic synthesis of organic carbonates

“…The analysis time plays a crucial role in the analysis since it has been previously shown that in some systems DMC can be formed in the solution via an indirect electrochemical, homogeneous reaction. 38,45,46,49 Therefore, a shorter analysis time can improve the analysis of the results. The drawback of this analytical technique is that it can only detect products that are volatile below the boiling temperature of the sample matrix.…”

“…DFT studies on metallic surfaces 38,49 showed that Cu, different from Au and Pd, is an interesting candidate for the electrosynthesis of DMC, as it is predicted to require lower overpotentials. A good catalytic material would bind the methoxy group strongly enough in order to lower the overpotential needed for CH 3 OH oxidation and, at the same time, allow for an optimal coverage of CO.…”

“…However, the binding of CO and methoxy intermediates should not be too strong, otherwise the surface will be poisoned by one of these intermediates. With the help of FTIR, ICP-MS and HS-GS-MS, the authors 38,49 found that Cu does not act as a direct electrocatalyst for CH 3 OH carbonylation to DMC (Table 2, entries 1 and 13). According to spectroelectrochemical measurements, adsorbed methoxy, which is an intermediate for the direct electrochemical synthesis of DMC, was not observed.…”

“…Furthermore, there is a lack of fundamental theoretical studies, which can help understand structure-performance relationships and design better catalysts. 38,49,67 For instance, modelling of the electrode-electrolyte interface can provide insight into the reaction kinetics and mass transport phenomena, which are of particular importance for continuous cell applications and porous electrode materials. Porous materials, usually prepared by catalyst deposition on a gas diffusion layer (GDL), have the advantage of supplying enough CO and CO 2 to the reaction zone, while enhancing a rapid electrolyte diffusion rate at the catalyst surface minimising mass transport limitations.…”