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Research in Chemically Transforming Lignin into Biofuels

In all plants, ranging from trees to crops, there is a substance that makes up its stems or wood or, cell walls and fiber. This substance is referred to as a complex natural polymer known as lignin and it is considered to be the second largest renewable carbon source on the planet following cellulose.

This is a TEM image of Ce-P-Pd elemental map. CREDIT: Igor Slowing

This natural abundance has gained immense interest from the research community in order to chemically transform lignin into biofuels. If plant life really does hold the building blocks for renewable fuels, then it would seem that human beings are literally surrounded by potential energy sources everywhere green grows.

However, untangling the complicated chains of these polymers into components, which can be useful for liquid fuel and other applications ranging from plastics to pharmaceuticals, has presented a constant challenge to industry and science.

Presently, there are two common ways of processing lignin. One needs an acid plus high heat and the other is pyrolysis, or treating with high heat when oxygen is not present. The results are less than optimal besides being energy-consuming processing methods.

You end up with individual molecules that are unstable and reactive, and they easily re-polymerize. It’s kind of a horrible mess, really. We need to be able to deconstruct lignin in a way that is economically feasible and into stable, readily useful components.

Igor Slowing, Expert in Heterogeneous Catalysis, the U.S. Department of Energy, Ames Laboratory

Slowing and other Scientists at Ames Laboratory are currently working to reach that commercialization target, experimenting with chemical reactions that are capable of decomposing lignin models at low pressures and temperatures. There are already proven ways of salvaging useful byproducts out of lignin via the addition of a stabilization process. However, Slowing and his research team took both the stabilization and decomposition processes further, by integrating the two into one multi-functional catalyst, employing phosphate-modified ceria.

Our process does the breaking of lignin-like material and the stabilization in a single step in very mild conditions. The interesting thing is that though there are two different types of chemical processes happening in a single material, they appear to be working synergistically, and are able to do that at a lower temperature.

Igor Slowing, Expert in Heterogeneous Catalysis, the U.S. Department of Energy, Ames Laboratory

Slowing’s research team, in another experiment, was able to process a related material, phenol, into useful industrial precursors for nylon production. This work made use of a catalyst produced from ceria and palladium doped with sodium, which significantly increased the reactivity of the process. They also eradicated the use of hydrogen, which is generated from steam-treatment of natural gas, and employed an energy-conserving alcohol-based hydrogenation process instead.

“Both of these results were very promising, and our next step is to combine the two experiments into one, and achieve lignin deconstruction using hydrogen from a renewable source,” said Slowing.

Ames Laboratory is ideally situated for this kind of research. We are able to collaborate with experts in several areas including catalytic chemistry, high throughput experimentation, spectroscopy, technoeconomic analysis; and in partnership with our contractor Iowa State University, we can also select and grow the best feedstocks.

Igor Slowing, Expert in Heterogeneous Catalysis, the U.S. Department of Energy, Ames Laboratory

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