Scientists at Pacific Northwest National Laboratory (PNNL) have developed a novel Pd‐promoted ZnO‐ZrO₂ catalyst that converts ethanol into C₅₊ ketones that can serve as building blocks for everything from solvents to jet fuel. A paper on the work is published in Angewandte Chemie International Edition.

The catalyst developed at PNNL condenses multiple reactions into a single step. Ethanol meets the catalyst under high temperature (370 °C, or 698 °F) and pressure (300 pounds per square inch). It then rapidly converts to products containing more than 70% C₅₊ ketones. The catalyst also appears robust, remaining stable over 2,000 hours of use. The end goal is to have a catalyst that can last for 2 to 5 years.

For their research, the scientists combined zinc oxide and zirconium dioxide for the catalyst. Such mixed-oxide catalysts don’t usually achieve such selectivity, spinning off too many unwanted byproducts instead.

But the researchers added another key ingredient to the mix: palladium. During the process, palladium and zinc formed an alloy that behaved very differently from its constituent parts, catalyzing only the necessary reaction steps that lead to the formation of C₅₊ ketones.

What’s novel is producing these ketones by forming the alloy between palladium and zinc during the reaction. So many intermediate steps all happen on this one catalyst—each step requires a different component of the catalyst to activate it.

—Karthi Ramasamy, study co-author and senior research engineer at PNNL

The catalyst can be used to make 2-pentanone and/or 2-heptanone, which are used in solvents for the electronics industry and are usually derived from petroleum. C₅₊ ketones can also serve as intermediates to produce fuel blendstock, lubricants, jet fuel, and diesel fuel. Generating such products from renewable ethanol rather than fossil resources could help cut greenhouse gas emissions and boost energy security.

This catalyst is very flexible. We can make adjustments to the operating conditions, such as temperature and pressure, to attain the desired product composition.

—Karthi Ramasamy

The technology for converting ethanol to ketones is available for licensing from PNNL’s commercialization office.

Resources

• S. Subramaniam, M. F. Guo, T. Bathena, M. Gray, X. Zhang, A. Martinez, L. Kovarik, K. A. Goulas, K. K. Ramasamy (2020) “Direct Catalytic Conversion of Ethanol to C₅₊ Ketones: Role of Pd–Zn Alloy on Catalytic Activity and Stability” Angew. Chem. Int. Ed. doi: 10.1002/anie.202005256