Acetaldehyde is an essential chemical building block that plays a major role in modern manufacturing. It is commonly produced using the ethylene-based Wacker oxidation process, a method that is expensive and carries significant environmental drawbacks. Converting bioethanol into acetaldehyde through selective oxidation offers a more sustainable alternative, but most existing catalysts face a familiar problem. When activity increases, selectivity often drops, leaving acetaldehyde yields below 90%.
More than ten years ago, researchers Liu and Hensen demonstrated an important advance using an Au/MgCuCr2O4 catalyst. Their work revealed a specific Au0-Cu+ interaction that delivered acetaldehyde yields exceeding 95% at 250°C, while remaining stable for more than 500 hours (J. Am. Chem. Soc. 2013, 135, 14032; J. Catal. 2015, 331, 138; J. Catal. 2017, 347, 45). Despite this milestone, developing safer, non-toxic catalysts that can achieve similar performance at lower temperatures has remained an unresolved challenge.
New Gold Perovskite Catalysts Push Performance Further
Recent progress from a research team led by Prof. Peng Liu (Huazhong University of Science and Technology) and Prof. Emiel J.M. Hensen (Eindhoven University of Technology) marks a significant step forward. The team designed a series of Au/LaMnCuO3 catalysts with different manganese-to-copper ratios. Among them, Au/LaMn0.75Cu0.25O3 stood out for its strong cooperative interaction between gold nanoparticles and a moderately copper-doped LaMnO3 perovskite structure.
This carefully tuned synergy allowed ethanol oxidation to proceed efficiently at temperatures below 250oC. The new catalyst outperformed the long-standing Au/MgCuCr2O4 benchmark, and the results were reported in the Chinese Journal of Catalysis.
Optimizing Catalyst Design for Higher Yield and Stability
To improve the efficiency of converting bioethanol into acetaldehyde — a valuable chemical used in plastics and pharmaceuticals, the researchers focused on perovskite-based catalyst supports. These materials were produced using a sol-gel combustion process and then coated with gold nanoparticles. By adjusting the manganese and copper content, the team identified an optimal formulation (Au/LaMn0.75Cu0.25O3) that achieved a 95% acetaldehyde yield at 225°C and remained stable for 80 hours.
Catalysts with higher copper levels performed worse, mainly because copper tends to lose its active chemical state during the reaction. The strong performance of the optimized catalyst was traced to a cooperative interaction among gold, manganese, and copper ions.
How Gold, Copper, and Manganese Work Together
To explain why the new catalyst performs so well, the researchers carried out detailed computational studies using density functional theory and microkinetic modeling. These simulations showed that introducing copper into the perovskite structure creates highly active sites near the gold particles. These sites make it easier for oxygen and ethanol molecules to react.
The optimized catalyst also lowers the energy barrier for key reaction steps, allowing the process to proceed more efficiently. Together, experimental data and theoretical modeling emphasize the importance of precisely tuning catalyst composition to achieve higher efficiency and better stability.
