(167d) A Four Step Catalytic Process for the Conversion of Aqueous Hemicellulose Stream to Hydrocarbons

Authors: 
Upadhye, A., University of Wisconsin-Madison
Huber, G. W., University of Wisconsin-Madison
Olcay, H., Massachusetts Institute of Technology


A four step catalytic process for the conversion of aqueous hemicellulose stream to hydrocarbons

Aniruddha A. Upadhye,1 Hakan Olcay2, and George W. Huber1, *

  1. Department of Chemical and Biological Engineering, University of Wisconsin, Madison, WI
  2. Laboratory for Aviation and the Environment, Massachusetts Institute of Technology, Cambridge, MA

Depleting fossil fuel resources, increasing concerns over environmental effects arising from combustion of these fossil fuel resources, and growing global energy needs have driven today’s research towards renewable energy technologies. Because of its abundance [1], biomass is considered as the most appropriate long-term alterative to fossil carbon. However, a large-scale transition to lignocellulosic “drop-in” fuels is constrained by the economic and technological challenges associated with biomass conversion processes.

Hemicellulose is one of the major components of biomass consisting of oligomers of C5 sugar. It can be easily separated in the form of aqueous stream from the lignocellulosic biomass using a pretreatment process. This aqueous hemicellulose stream is also a by-product of pulp and paper industry. The focus of this presentation is a four step catalytic process [2] for conversion of aqueous hemicellulose stream obtained from the pre-treatment processing. First, the oligomers of C5 sugars in hemicellulose stream (mainly xylose) are hydrolyzed and dehydrated to furfural in a continuous flow reactor with a homogeneous acid catalyst and a biphasic reaction scheme with tetrahydrofuran (THF) as co-solvent.  Furfural yields up to 90% were obtained in this first step. The furfural in THF is then condensed with acetone to form a C13 precursor in a biphasic base catalyzed aldol condensation reaction. The C13 precursor is then hydrogenated over Ru/C catalyst at low temperatures to saturate the double bonds. This low temperature hydrogenation makes the C13 precursor more stable towards high temperature hydrodeoxygenation step. In this step, certain larger oligomers are also formed from partially hydrogenated product. The product of hydrogenation step is subsequently hydrodeoxygenated over Pt/SiO2-Al2O3 at higher temperatures to obtain jet fuel range straight chain hydrocarbons. Using this process, we can produce hydrocarbons containing up to 31 carbon atoms. We have successfully demonstrated this process with aqueous hemicellulose stream obtained from real biomass. Here, we present the effects of different pretreatment processes on the downstream catalytic processing of the hemicellulose stream to hydrocarbons and provide directions for future research in catalytic conversion of biomass.

References:

[1] G. W. Huber, S Iborra, A. Corma, Chem. Rev., 2006, 106, 4044-4098.

[2] H. Olcay, A.V. Subrahmanyam, R. Xing, J. Lajoie, J.A. Dumesic, G.W. Huber, Energy Environ. Sci., 2013, 6, 205

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