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Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Chemical Engineering

Year Degree Awarded

Summer 2014

First Advisor

Paul J. Dauenhauer

Subject Categories

Catalysis and Reaction Engineering

Abstract

Growing concern over the petroleum supply, energy independence, and environmental impacts associated with fossil fuels, has motivated research into the production of renewable fuels and aromatic chemicals from biomass resources. Specifically, furan-based feedstocks such as furfural, 2-methylfuran (MF) and, 2,5-dimethylfuran (DMF) can be derived from biomass and used to produce a wide variety of desired compounds. These furan-based feedstocks are produced by: (a) the hydrolysis of cellulose and hemicellulose form to glucose and xylose, (b) the dehydration of these carbohydrates to form 5-hydroxymethylfurfural (HMF) and furfural, and (c) the reduction of HMF and furfural to DMF, MF, and furan.

The use of a continuous electrocatalytic membrane reactor presents a novel method of selectively hydrogenating furfural at low temperatures without the use of gaseous hydrogen. Conversion of acetone to isopropanol confirmed that the rate of hydrogenation using gaseous hydrogen is comparable to the rate of hydrogenation using water electrolysis. Evaluation of the electrocatalytic hydrogenation of furfural demonstrated an ability to control product selectivity beyond the capability of conventional catalysis. Results indicate that production of renewable “electrofuels” in a PEM reactor, utilizing water electrolysis in the place of hydrogen gas, is a viable alternative to conventional methods.

Diels-Alder cycloaddition of furan-based compounds and ethylene is a promising method of sustainably producing valuable base chemicals. Specific molecules of interest include p-xylene, the feedstock for polyethylene terephthalate (PET); toluene, an important monomer for polyurethane; and benzene, a precursor for polystyrene. The reaction proceeds via a [4+2] Diels-Alder cycloaddition of the furan feedstock and ethylene to produce an oxa-norbornene intermediate, and the subsequent dehydration of the intermediate to form the desired aromatic. 90% selectivity to p-xylene from DMF and 46% selectivity to toluene from MF were achieved over an H-BEA catalyst. Analysis of the reaction rate as a function of catalyst loading revealed two distinct kinetic regimes, whose activation energies correspond with DFT calculated energy barriers for dehydration and cycloaddition rate-limiting steps. Additionally, the reaction network for the MF/ethylene system was expanded to include MF polymers and two isomers of incomplete cycloadduct dehydration. Results demonstrate the complex nature of these reactions and the effect of reaction temperature, catalyst type and loading, and furan feedstock on the product distribution.

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