Graduate Thesis Or Dissertation

 

Modeling the conversion of arabinose to furfural Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/d217qs69x

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  • Hemicellulose hydrolyzate contains many carbohydrate fractions, the most abundant being xylose, arabinose, and glucuronic acid. Under mild acid conditions (0.025 - 0.10 M sulfuric acid) and high temperatures (140°C to 200°C) the first two components form furfural through a series of dehydration reactions. Unlike xylose and arabinose, glucuronic acid must first undergo a decarboxylation reaction before the dehydration steps to form furfural. The kinetics for the reaction of xylose to furfural have been studied extensively (Root et al., 1959 and Sproull, 1986). Some researchers have considered the kinetics of arabinose degradation (Bott et al., 1932; Hurd et al., 1932; Hughes et al., 1939; Saeman, 1945), however, the rate constants for the dehydration of arabinose to furfural have not been accurately modeled to fit an Arrhenius expression. The scope of this work was to model the kinetics for the formation of furfural from arabinose in the aqueous phase using the three-constant Dunlop model. The conversion of arabinose was found to follow a first-order reaction. Some experimental runs were made in the presence of an extraction solvent, ortho-nitrotoluene. In this case furfural concentrations were determined in both phases. The use of the extraction solvent is to protect the forming furfural from further acid degradation. The solvent to water ratio in these experiments was two. Predicted furfural concentration profiles (aqueous and solvent phases) were compared to the experimentally determined values assuming that the process was diffusion limiting. The two profiles were in good agreement with each other up to and including the maximum furfural concentration. At times after the maximum furfural concentration, the predicted profiles slightly overestimated the experimental furfural concentrations. A short study was also made to consider the possibility that furfural degradation may occur in the solvent phase (o-nitrotoluene) which would decrease the furfural yield. In this case, the decomposition of furfural in the solvent phase was negligible.
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