Scientists develop a catalyst to convert ethanol into high-value chemicals and fuels

While we usually think of ethanol as a gas tank fuel, it can also be made into valuable chemicals that could help replace a variety of petroleum-based products beyond just gasoline. However, the evolution of ethanol for a wider range of industries requires more efficient chemical processes than are available today.

Scientists at the Pacific Northwest National Laboratory (PNNL) have developed a new catalyst that converts ethanol into C5 + ketones that can serve as the building blocks for everything from solvents to jet fuel. In a new article, they describe this revolutionary chemistry and the mechanism behind it.

One-pot upgrade ethanol to C5 + ketones

Catalysts are needed to accelerate the chemical transformations that convert ethanol into other compounds. To be commercially viable, a catalyst must be highly active while selectively generating the desired chemicals, in other words it must reliably churn out the exact material sought. Scientists are looking for ethanol catalysts that can extract the right compounds efficiently and do so repeatedly. In chemicals that require numerous reaction steps in a long cascade of chemical reactions to the final end product, this can be a daunting task.

The catalyst developed with PNNL condenses several reactions in a single step. Ethanol encounters the catalyst at high temperature (370 ° C or 698 ° F) and pressure (300 pounds per square inch). Then it quickly converts to products containing more than 70% C5 + ketones. The catalyst also appears robust, remaining stable over 2,000 hours of use. The ultimate goal is to have a catalyst that can last from 2 to 5 years.

For their research, the scientists combined zinc oxide and zirconium dioxide for the catalyst. Such mixed oxide catalysts usually do not achieve such selectivity, instead producing too many unwanted by-products.

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.

“The novelty is to produce these ketones by forming the alloy between palladium and zinc during the reaction,” said Karthi Ramasamy, study co-author and senior research engineer at PNNL. “So many intermediate steps all take place on this catalyst – each step requires a different component of the catalyst to activate it.”

One catalyst, flexible operation

The catalyst can be used to produce 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 for the production of mixtures of fuel, lubricants, jet fuel and diesel fuel. Generating such products from renewable ethanol rather than fossil resources could help reduce greenhouse gas emissions and increase energy security.

“This catalyst is very flexible,” Ramasamy said. “We can make changes to operating conditions, such as temperature and pressure, to achieve the desired product composition.”

The process is further detailed in the paper “Direct catalytic conversion of ethanol into C5 + ketones: role of the Pd-Zn alloy on catalytic activity and stability”, published in the journal Angewandte Chemie International Edition.