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January 2012

Deciphering the Black Box of Next-Generation Biofuels Chemistry

Researchers combine experiments and fundamental models to unveil the previously unknown mechanisms for how biofuels are generated from biomass

Mike Salciccioli

A novel experimental technique, thin-film pyrolysis, is capable of heating biomass at over a million degrees a minute and is coupled with powerful first-principles simulations to deconstruct the black box masking high-temperature biofuels production processes. Click on image to enlarge

Next-generation biofuels production uses temperatures around 1000°F to convert every part of a plant into molecules that are similar to those in fuels. A series of complex processes fracture large biomolecules containing millions of atoms into much smaller molecules with higher energy density and reactivity. While this chemical deconstruction is critical to biofuels production, for decades the fundamental chemical reactions controlling this transformation have been unknown. Researchers at the Catalysis Center for Energy Innovation are seeking to remove this black box and to identify and control the chemical reactions responsible for producing biofuels from biomass in these next-generation approaches. Their work identifies, for the first time, the fundamental chemistry of high-temperature biomass conversion.

Next-generation biofuels

While conventional biofuels production relies on slow and expensive enzymatic processes to convert only the fruit of plants to fuels, next-generation approaches can convert the entire plant to fuels. This is a huge benefit because fuel can be produced from the non-food parts of the plant, leaving the fruit for food production. In these processes, biomass is converted to fuels using a relatively simple approach: plants are heated to high temperatures where they are deconstructed to form smaller, fuel-range molecules. While this conversion occurs in a single reactor, the process involves millions of solid-, liquid- and gas-phase reactions. Deciphering this complex network of reactions is challenging due to the number of chemical processes and differing timescales of these processes. Despite the difficulty, knowledge of the chemistry would facilitate the design of better processes, lower manufacturing costs and improve the overall efficiency for eventual economically viable commercialization of next-generation biofuels.

Revealing the chemistry

Researchers at the Center are able to unmask the complex chemistry of high-temperature biomass conversion by combining advanced experiments and simulations. A novel experimental technique was developed that utilizes extremely small samples, approximately the thickness of a human hair, for precise control of the deconstruction process. These advanced experiments were then coupled with powerful first-principles simulations to understand the sub-atomic details of how fuel-range compounds are formed.

Using this new approach, the researchers show that biomass deconstruction chemistry involves short-lived radical species. This implies that the pair of electrons that comprise a chemical bond part ways, rather than traveling together, during the biomass conversion process. This finding reveals the sub-atomic information of high-temperature cellulose pyrolysis for the first time and represents a critical step in understanding the underlying mechanisms of conversion of raw biomass to fuels and chemicals.

“This work yields fundamental knowledge into the underlying kinetics of biomass processing through the combination of insightful experiments and ab initio simulation,” says Michail Stamatakis, a postdoctoral fellow at the University of Delaware.

Significance for biofuels

This approach combines novel experiments with rigorous models to show how fuels form from biomass in high-temperature conversion processes and enables advanced optimization techniques to be utilized to design improved biofuels production facilities.

“This work paves the road to designing novel processes for the economical and sustainable production of chemicals and fuels from biomass,” says Stamatakis.

Such improvements are important for a large-scale, noncontroversial implementation of biofuels, one of the fastest growing fields in the renewable energy sector.

More Information

Mettler MS, SH Mushrif, AD Paulsen, AD Javadekar, DG Vlachos and PJ Dauenhauer. 2011. “Revealing Pyrolysis Chemistry for Biofuels Production: Conversion of Cellulose to Furans and Small Oxygenates.” Energy & Environmental ScienceDOI: 10.1039/C1EE02743C.

Acknowledgments

This research is supported as part of the Catalysis Center for Energy Innovation, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Key calculations were performed using the TeraGrid resources provided by University of Illinois’ National Center for Supercomputing Applications. SH Mushrif is the recipient of the Natural Sciences and Engineering Research Council of Canada postdoctoral fellowship.

About the author(s):

  • Mike Salciccioli is a Ph.D. candidate at the University of Delaware and is a student in the Catalysis Center for Energy Innovation. His thesis research involves the rational design of catalysts for conversion of small biomass derivatives to fuels and chemicals and he was the recipient of the Bill N. Baron Fellowship award from the Delaware Institute of Energy Conversion in 2011. He is advised by Dion Vlachos.

Unlocking the Biofuels Black Box

Transparent metal and DNA-based cages could help transform water and sunlight into fuel

What if you could convert trees, grasses or bio-wastes directly to fuels in less than 1 second? While this sounds like the stuff of dreams, next-generation biofuels processes, such as pyrolysis, utilize high temperatures to generate extremely fast reaction rates and rapidly convert all parts of biomass to fuels. Despite the clear benefits of these new high-temperature technologies, there is a black box masking the fundamental chemistry and inhibiting development and deployment of this exciting approach to biofuels production. However, help is on the way. Researchers have developed a new experimental technique capable of explaining the reactions that happen in this black box. The new technique utilizes extremely small biomass samples, about the thickness of a human hair, which can heat biomass at over a million degrees a minute. This fast heating enables precise control of temperature during the conversion process, something not possible with previous approaches. The researchers then couple these experiments with powerful simulations to show how biofuels are formed in high-temperature biomass conversion processes. This work could lead to new innovations in fossil-free fuels. The research was done at the Catalysis Center for Energy Innovation, led by the University of Delaware.

Written by Michael Salciccioli

More Information

Mettler MS, SH Mushrif, AD Paulsen, AD Javadekar, DG Vlachos and PJ Dauenhauer. 2011. “Revealing Pyrolysis Chemistry for Biofuels Production: Conversion of Cellulose to Furans and Small Oxygenates.” Energy & Environmental ScienceDOI: 10.1039/C1EE02743C.

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.