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May 2011

Breaking Limits with Biomass Thermochemical Catalysis

Scientists discover a novel zeolite catalyst that replaces enzymes

Paul J. Dauenhauer

New catalyst promotes turning biomass, like grasses and wood chips, into biofuels, biomaterials, biochemicals and food.

In the world of biomass and carbohydrate processing for biofuels and biochemicals, enzymes have long been the catalyst of choice despite their high cost.  Now, researchers from the Catalysis Center for Energy Innovation have discovered a new zeolite catalyst that is cheaper, more stable and can directly replace enzymes in the production of fructose.  This research was led by Mark Davis at the California Institute of Technology and featured in the Proceedings of the National Academy of Sciences.

Benefit for renewable products: Fructose is generally recognized as the sweetener in soda and food as well as the main component of high-fructose corn syrup.  In production, starch from maize (corn) is hydrolyzed to produce glucose followed by rearrangement or isomerization to form fructose.  The fructose is then refined, resulting in a high-volume food commodity, sugary syrup, that can be used in hundreds of different food products.

The discovery of a new, cheaper catalyst to produce fructose improves the economics of high-fructose corn syrup production and opens the door to new biofuels, biochemicals and materials from biomass.  Fructose is the precursor to a class of molecules called “furans,” which are known to have broad applicability.  Furans can be converted to molecules that exhibit favorable fuel qualities, such as dimethylfuran. Alternatively, furans can be converted to basic chemicals, such as levulinic acid, or polymerized to make renewable materials.

Selective reactions with carbohydrates: The general challenge of biomass processing for new products arises from the high number of oxygen atoms within biomass molecules.  For this reason, highly selective biological enzyme catalysts have been required due to their shape-selective structure.  The newly discovered inorganic catalyst achieves similar performance through the combination of materials that address both molecular shape and chemical transformation.

To make the new catalyst, researchers combined an active metal center composed of tin with a crystalline, microporous material: Beta zeolite. The zeolite structure consists of large pores through which glucose diffuses.  Within this structure, an atom of tin built into the zeolite framework acts as a solid acid on a single glucose molecule to catalyze its transformation to fructose.

Breaking catalysis limits:  The new tin-zeolite catalyst breaks several processing limitations inherent in conventional immobilized enzyme catalysts.  Inorganic zeolites are capable of catalyzing the transformation of sugars and biomass in the presence of ionic impurities, such as calcium, with excessive variability of pH (e.g., < 6.0), and at significantly higher reaction temperatures than is possible with enzymes.  Additionally, the utilization of the new catalyst provides a significantly more stable and cheaper catalyst alternative that does not require regular replacement within catalytic reactors.

With increased processing flexibility and reduced cost, the tin-zeolite catalyst is altering perceptions of catalytic strategies for biomass conversion.  Biomass processing, which has been limited by existing biological catalysts, can now be achieved via heterogeneous, inorganic catalysts.

“This is a major breakthrough in the catalysis of carbohydrate isomerization, which will accelerate the implementation of biomass processing,” says Aditya Bhan, Assistant Professor of Chemical Engineering at the University of Minnesota.

This discovery supports the research objectives of the Catalysis Center for Energy Innovation which aims to discover new catalytic materials to revolutionize biomass processing for fuels and chemicals.

More Information

Moliner M, Y Roman-Leshkov, and ME Davis. 2010. “Tin-containing zeolites are highly active catalysts for the isomerization of glucose in water.” Proceedings of the National Academy of Sciences107:6164. DOI:10.1073/pnas.1002358107.

Acknowledgments

This work was financially supported as part of the Catalysis Center for Energy Innovation, an Energy Frontier Research Center funded by the Department of Energy, Office of Basic Energy Sciences.

About the author(s):

  • Paul J. Dauenhauer, Ph.D., is a member of the Catalysis Center for Energy Innovation and Assistant Professor of Chemical Engineering at the University of Massachusetts, Amherst. He received his Ph.D. from the University of Minnesota in 2008 and has worked for both the Dow Chemical Company and Cargill, Inc.

More Information

Moliner M, Y Roman-Leshkov, and ME Davis. 2010. “Tin-containing zeolites are highly active catalysts for the isomerization of glucose in water.” Proceedings of the National Academy of Sciences107:6164. DOI:10.1073/pnas.1002358107.

Disclaimer: The opinions in this newsletter are those of the individual authors and do not represent the views or position of the Department of Energy.