Doshisha University’s innovation turns carbon dioxide and water to acetylene

Researchers at Doshisha University in Japan, in collaboration with Daikin Industries, Ltd., have developed a novel method for producing acetylene (C2H2), a crucial component in various industrial applications, using carbon dioxide (CO2) and water (H2O) as raw materials. This innovative approach, documented in a study published in ACS Sustainable Chemistry & Engineering, promises to revolutionize the production of acetylene, steering away from the reliance on fossil fuels and significantly reducing carbon emissions. 

Acetylene’s role is key in numerous industries, from welding and metal processing to the synthesis of synthetic resins and plastics such as PVC. Traditionally, its production involves processes that not only consume fossil fuels but also contribute to the high carbon footprint of these industries. The collaborative research effort aims to address this environmental challenge by offering a sustainable alternative for acetylene synthesis. 

The research, led by Assistant Professor Yuta Suzuki from the Harris Science Research Institute, along with Professor Takuya Goto from the Department of Science of Environment and Mathematical Modeling at Doshisha University, and Tomohiro Isogai from Daikin Industries Ltd., leverages the electrochemical and chemical properties of high-temperature molten salts, or chloride melts, to convert CO2 into C2H2. This process revolves around the formation of metal carbides, such as CaC2 and Li2C2, on one of the electrodes, which then react with water to produce the desired acetylene gas. 

Through meticulous experimentation, including techniques such as cyclic voltammetry, carbon crystallinity analysis, and X-ray diffraction, the team identified an optimal molten salt composition that facilitates the selective formation of CaC2 around the cathode. This composition, a NaCl−KCl−CaCl2−CaO melt enriched with additional CaCl2 under a CO2 atmosphere, demonstrated superior performance compared to lithium-inclusive alternatives. 

One of the significant advantages of this new method is the reusability of the electrodes, which can undergo simple reconditioning treatments due to the fact that the crucial reactions occur on the deposited metal carbides rather than directly on the electrode surfaces. More importantly, this approach utilizes CO2—a major contributor to global warming—as a raw material, marking a significant step towards sustainable chemical synthesis and resource utilization. 

As Professor Goto articulates, this method not only holds the potential to reduce dependency on fossil fuels but also to serve as a carbon-negative technology. By extracting CO2 directly from the atmosphere, particularly in conjunction with direct air capture technologies, this technique could contribute to a more sustainable and environmentally friendly industrial landscape. 

This research opens up new possibilities for producing essential chemicals and resins from CO2, offering a path towards building societies that coexist harmoniously with the environment. Such advancements could preserve the benefits of our modern lifestyle while significantly mitigating its environmental impact, heralding a new era of sustainable industrial processes.