Electro-valorization of acetylene to 1,3-butadiene

Chemists from the National University of Singapore (NUS) have developed a sustainable method to electrosynthesize 1,3-butadiene, a feedstock used for synthetic rubber production, from acetylene.

Lowering the energy requirements and environmental impact of producing multi-carbon molecules is critical for advancing a more sustainable chemical industry. A key approach is electrification, which uses renewable electricity to convert simple feedstocks such as water and carbon dioxide (CO₂) into valuable chemicals and fuels. Achieving this requires identifying clear target molecules and efficient synthesis routes. One such target is 1,3-butadiene. Today, 1,3-butadiene is produced as a minor by-product alongside ethylene from the energy-intensive thermal cracking of naphtha or ethane. Despite this, more than 21 million tonnes of this critical feedstock are produced annually.

A research team led by Associate Professor YEO Boon Siang, Jason from the Department of Chemistry at NUS has found that copper catalysts, after a simple modification with iodide anions, are highly efficacious for electro-converting acetylene to 1,3-butadiene at ambient temperature and pressure. 1,3-butadiene could be produced with a Faradaic efficiency of 93% at −0.85 V versus the Standard Hydrogen Electrode (SHE) and a partial current density of −75 mA cm^-2 at −1.0 V versus SHE. The partial current density of 1,3-butadiene, an indicator of catalytic activity, was at least 20 times higher than that reported in previous studies. This research was conducted in collaboration with Dr Federico CALLE-VALLEJO from the Basque Foundation for Science and the University of the Basque Country, both in Spain. The team also included Dr Wei Jie TEH from the Department of Chemistry, NUS, Ms Eleonora ROMEO and Professor Francesc ILLAS from the University of Barcelona, Spain, Dr Ben ROWLEY from Shell Global Solutions International B.V., and Dr Shibo XI from the Institute of Sustainability for Chemical, Energy and Environment, Agency for Science, Technology and Research.

The findings were published in the journal Nature Catalysis.

Extensive characterisation of the catalyst using in situ spectroscopies and computational simulations using density functional theory revealed that iodide promotes stable ensembles of neutral and partially oxidised Cu sites (Cu^δ+–Cu⁰ sites), which enhance the carbon-carbon (C-C) coupling of *C₂H₃ intermediates to form 1,3-butadiene.

Prof Yeo said, “This work is the fruit of an intense collaboration between experimentalists and theoreticians, together with our industrial partner, to discover how important chemicals, such as 1,3-butadiene, could be more sustainably produced.”

Building on the research findings from their work, the research team plans to develop catalysts capable of coupling acetylene into longer-chain hydrocarbons, which could potentially be used as aviation fuel.

Illustration of the electrocatalytic conversion of acetylene (C₂H₂) to 1,3-butadiene (C₄H₆) on copper catalysts. The process involves the adsorption of acetylene molecules onto the catalyst surface, followed by hydrogenation and coupling of *C₂H₂ and *C₂H₃ intermediates, leading to the formation of 1,3-butadiene, which is subsequently desorbed. [Credit: Nature Catalysis]

Reference

WJ Teh; E Romeo; SB Xi; B Rowley; F Illas; F Calle-Vallejo*; BS Yeo*, “Selective electroreduction of acetylene to 1,3-butadiene on iodide-induced Cu^δ+-Cu⁰ sites” Nature Catalysis DOI : 10.1038/s41929-024-01250-0 Published: 2024.