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Paul Dauenhauer

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Our ability to provide fuels and chemicals in a sustainable manner for future generations presents the largest global challenge for reaction engineering in the twenty-first century.  The core of the technical problem are the significant physical differences between the carbon sources of the future such as biomass, natural gas, and heavy oils and our current reduced-carbon feedstocks.  Our goal is to develop integrated catalytic reactor technologies that permit the utilization of new and exotic feedstocks, while simultaneously allowing atomic level control and access to energy. 

Renewable Processes for Production of p-Xylene from Glucose

The production of renewable chemicals from biomass relies on controlled catalytic deoxygenation and rearrangement to monomers with targeted functionality.  We have developed a new catalytic reaction system (heterogeneous zeolite catalyst, four phase reactor) which can convert biomass-derived furans such as dimethylfuran to valuable aromatic monomers such as p-xylene (a key feedstock in the production of plastic bottles) with 75% selectivity at high conversion (>90%). 

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Award/Support: Department of Energy - Energy Frontiers Research Center, Catalysis Center for Energy Innovation (CCEI). 

Pyrolysis Chemistry of Biomass and Cellulose

For the last five decades, the chemistry of cellulose pyrolysis has been described by a lumped kinetic model consisting of three steps which predicts the rate of formation of ‘gases, char, and vapors.’  Using our unique technique of thin-film pyrolysis, we have elucidated seven condensed phase reaction pathways (depicted below, black).  We have discovered that α-cyclodextrin is a surrogate for cellulose pyrolysis, which has led to a mechanism for furan formation directly from molten cellulose (using molecular dynamics simulation).  A new co-pyrolysis technique using isotopically labeled carbohydrates led to the discovery of secondary levoglucosan pathways (depicted below, red).  Finally, we have discovered the chain length effect of cellulose, whereby the ratio of end-groups to inner monomers is a key descriptor of cellulose pyrolysis chemistry.

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Award/Support:  Department of Energy, Early Career Award
Highlighted in Nature Chemistry 2012, 4, 68-69.

New Experimental Techniques for High Temperature Pyrolysis Chemistry

A molecular-level understanding of thermochemical conversion of lignocellulosic materials does not exist resulting from the multi-scale and multi-phase nature of biomass, thereby requiring the development of new experimental techniques.  To study lignocellulose chemistry, we developed 'Thin-Film Pyrolysis' (TFP) which utilizes micrometer-thick cellulose samples to achieve isothermal reaction conditions at 500-600 °C (∆T>10^6 K/min) which we have also shown to be absent mass transfer limitations. As shown in the following reaction-transport map, pyrolysis chemistry by TFP occuring within the kinetically-limited regime are the first experiments to provide data on the intrinsic chemistry of cellulose, carbohydrates, and biomass.

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Award:  NSF EAGER Award, NSF CAREER Award

Catalytic Processing of Biomass-Derived Oxygenates

The catalytic deoxygenation of biomass-derived aromatics such as furfural, hydroxymethylfurfural, or m-cresol requires the selective removal of oxygen with the use of hydrogen.  However, these processes occur in liquid water, which can interact with oxygenates when adsorbed on heterogeneous catalytic surfaces.  Using an oxygenated aromatic surrogate, we reveal the role of hydrogen bonding on the adsorbtion and reaction of oxygenated aromatic compounds on Pd and Pt (111) surfaces.  Using a combination of experiments, molecular dynamics simulations and density functional theory, we show that hydrogen bonding can alter surface energies by as much as 25% during reaction.

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Funding Award:  3M Corporation, Young Faculty Award
Publications:  (1) J. Yang, P.J. Dauenhauer, A. Ramasubramaniam, “The Role of Water in the Adsorption of Oxygenated Aromatics on Pt and Pd,” Submitted. (2) L.D. Schmidt, P.J. Dauenhauer, "Hybrid Routes to Biofuels," Nature 2007, 447, 914-915.

Aerosol Generation from High Temperature Molten Biomass

The generation of primary aerosols from biomass during pyrolysis hinders the production of thermochemical biofuels by transporting non-volatile inorganics and organic biopolymers to the gas phase.  Using a combination of aerosol chemical characterization, ejection measurements (photography, shown below), and fluid modeling, we reveal the fundamental mechanism of aerosol generation directly from molten cellulose.  Aerosols are generated by the collapse of vapor bubbles, and future research will attempt to suppress their formation using inexpensive surfactants directly applied to cellulose and wood fibers.

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Highlighted in Science, 2011, 333, 1680.
Publications:  (1) M.S. Mettler, et al. Energy & Environmental Science 2012, 5, 5414-5424. (2) P.J. Dauenhauer, et al. Green Chemistry 11 (2009) 1155.

Integrated Pyrolysis and Catalysis - Reactive flash Volatilization

Conversion of biomass to pyrolysis oil or a clean stream synthesis gasn remains the most economically-challenged step in production of synthetic fuels and chemicals. We developed a single catalytic reactor that mixes air and biomass particles (depicted below) to produce either bio-oil or a H2/CO-rich gas autothermally in milliseconds.  This technology was shown to have broad applicability for processing a wide range of feedstocks including plastics, paper, and wood.  Also, the addition of CH4 co-reactant was shown to improve the overall yield of carbon monoxide from biomass to over 95%.

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Publications:  (1) J.L. Colby, et al.  Green Chemistry 2010, 12, 378. (2) D. Rennard, et al. Energy & Fuels 2008,22, 1318-1327. (3) J.L. Colby, et al. Green Chemistry 2008, 10, 773-783. (4) P.J. Dauenhauer, Angewandte Chemie 2007, 119, 5968-5971. (5) J.R. Salge, et al. Science 2006, 314, 801-804.

Patents:  (1) “Reactive Flash Volatilization of Fluid Fuels” L.D. Schmidt, P.J. Dauenhauer, B.J. Dreyer,  U.S. Patent Pending. Application # 60/893,080.  (2) “System and Method for Volatilizing Solid Fuels to Produce Synthesis Gas” L.D. Schmidt, P.J. Dauenhauer, B.J. Dreyer, N.J. Degenstein, U.S. Patent Pending.  Application #60/893,072 (3) A. Bhan; L. D. Schmidt; J. C. Colby, PJ. Dauenhauer, “Methods of Producing Synthesis Gas using a Carbon Dioxide Feed Component” U.S. Provisional Patent Application Serial No. 61/172,325

 

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