Acetaldehyde is a basic raw material for many products. To date, the chemical has been produced using the resource-intensive Wacker process. But now researchers have developed a new type of copper catalyst that can produce CO2 can be converted into acetaldehyde much more efficiently and in a more environmentally friendly manner. This is made possible by a special atomic structure in the copper particles. This could make acetaldehyde production and many other industrial processes more sustainable.
Acetaldehyde is a chemical that is necessary as a raw material for the production of numerous everyday products, from perfumes to dyes and medicines to plastics. Acetaldehyde itself has so far mainly been obtained using the so-called “Wacker process”, which has practically not changed in the last 60 years. Ethylene from crude oil and natural gas is mixed with strong acids and converted using a palladium catalyst. However, this process has a high CO2footprint, is resource intensive and unsustainable.
Scientists have therefore long been looking for more environmentally friendly ways to produce acetaldehyde. A promising approach is the electrochemical reduction of the greenhouse gas carbon dioxide (CO2) using copper-based catalysts. However, these processes have so far not only produced the desired acetaldehyde, but rather a mixture of several products.
Innovative catalyst for more efficiency
Now chemists led by Cedric Koolen from the Ecole Polytechnique Fédérale de Lausanne (EPFL) have developed a new copper-based catalyst that is significantly more efficient. To do this, the researchers first created tiny clusters of copper particles from copper electrodes, each only around 1.6 nanometers in size. They then attached these copper clusters to a carbon support to stabilize them. To test the performance of the new catalyst, the chemists conducted a series of electrochemical reactions with CO in a controlled environment2 through and compared the yield.
The evaluation showed that the new copper catalyst produces CO in this process2 can convert it into acetaldehyde with a selectivity of 92 percent. The catalyst also maintained this performance in a 30-hour stress test over several cycles. The copper clusters were also stable and required only a relatively low voltage and therefore little energy for the chemical reaction. This makes them cost-effective both to produce and to use.
Using various spectroscopes, Koolen and his colleagues also surprisingly found that the copper particles retained their metallic nature throughout the reaction. “The copper remained metallic even after the electrical potential was removed and the catalyst was exposed to air,” says co-author Wen Luo from Shanghai University. “Copper usually oxidizes like crazy, especially such small copper particles. “In our case, however, an oxide shell formed around the cluster, protecting the core from further oxidation,” explains Luo. This property allows the catalyst to be recycled and reused.
Stable and reusable catalyst thanks to atomic structure
The new copper catalyst is therefore significantly more stable and efficient than previous alternatives. The discovery represents a “green” breakthrough for the production of acetaldehyde. The method is more environmentally friendly and could replace the Wacker process in the future. Since acetaldehyde is a building block for many other chemicals, this research also has the potential to subsequently transform several industries, from pharmaceuticals to agriculture, the team explains.
But why does the copper catalyst work so well? Using computer simulations, Koolen and his colleagues found that the copper clusters have a specific configuration of atoms. This atomic arrangement of copper promotes the binding and conversion of CO2molecules to acetaldehyde. However, other possible products such as ethanol or methane are energetically disadvantaged with this catalyst structure.
This principle can now be transferred to other chemical reactions and catalysts, as the team reports. “Our computer simulations allow us to quickly examine clusters for promising properties. We can also easily produce the new material and test it directly in the laboratory,” says co-author Jack Pedersen from the University of Copenhagen. This means that new types of catalysts could be developed much more quickly in the future.
Source: Cedric Koolen (Ecole Polytechnique Fédérale de Lausanne) et al.; Nature Synthesis, doi: 10.1038/s44160-024-00705-3