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Open Access Dissertation
Doctor of Philosophy (PhD)
Year Degree Awarded
Paul J. Dauenhauer
Catalysis and Reaction Engineering
Fast pyrolysis of biomass is a next-generation biofuels production process that is capable of converting solid lignocellulosic materials (in their raw form) to a transportable liquid (bio-oil) which can be catalytically hydrogenated to fuels and chemicals. Pyrolysis reactors depolymerize solid biomass by heating the feedstock (in the absence of oxygen) up to high temperatures (400 – 600 °C) to produce a short-lived intermediate liquid phase (only a few seconds), which ultimately breaks down to form small (1-6 carbon) oxygenates. These vapor-products can then be condensed at room temperature to produce liquid bio-oil. While biomass fast pyrolysis has enormous potential to produce renewable fuels, an understanding of the fundamental chemistry and transport processes of biomass pyrolysis to produce bio-oil is not available in the literature.
This work utilizes co-pyrolysis and isotopic labeling to study the liquid-phase secondary reactions of levoglucosan to form anhydrosugars, pyrans, and light oxygenates. Isotopic labeling studies also reveal that hydrogen exchange is a critical component of levoglucosan deoxygenation. Next, the effects of pyrolysis reaction temperature and sample length scale are discussed. These studies revealed that the yield of total furan rings (i.e., all products containing a five-membered furan ring) does not change significantly with increased reaction temperature compared to other pyrolysis products, such as light oxygenates and anhydrosugars. However, the functional groups bound to the furan ring (e.g., alcohols and aldehydes) are easily cleaved to produce smaller furans. This chemistry was targeted by impregnating cellulose with palladium on carbon to selectively decarbonylate oxygenated furans within liquid intermediate cellulose to form deoxygenated furans resulting in a more stable bio-oil.
The last part of this thesis, a new experimental technique, Spatiotemporally-Resolved Diffuse Reflectance in situ Spectroscopy of Particles (STR-DRiSP), which is capable of measuring biomass composition during fast pyrolysis with high spatial (ten micron) and temporal (one millisecond) resolution is developed. Compositional data were compared with a comprehensive two-dimensional single particle model. The STR-DRiSP technique can be used to determine the transport-limited kinetic parameters of biomass decomposition for a wide variety of biomass feedstocks.
Paulsen, Alex D., "PRIMARY AND SECONDARY REACTIONS OF CELLULOSE MELT PYROLYSIS" (2014). Doctoral Dissertations. 229.