Browsing by Author "Lamptey, Irene Naa Odarley"

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    Comparative kinetics analysis of furfural production from xylan and xylose
    (Stellenbosch : Stellenbosch University, 2019-04) Lamptey, Irene Naa Odarley; Gorgens, Johann F.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.
    ENGLISH ABSTRACT: Furfural is a valuable platform chemical with a wide range of industrial applications. The replacement of petrochemicals with alternative bio furfural will reduce the overall carbon footprint of crude oil based products. The current industrial furfural production method is a direct catalyzed conversion of lignocellulosic biomass in a continuous or batch reactor system. The mechanism of the reaction is primarily a two-step reaction process comprising xylan hydrolysis and xylose dehydration along with the simultaneous conversion of other components of the lignocellulose biomass material. Examining the kinetics of furfural production using xylan and xylose as starting material will provide insights and fundamental knowledge on the furfural production reaction with little effect of the inhibitory components present in whole lignocellulose biomass. This study focuses on the kinetics of furfural formation from xylan and xylose at temperature ranges of 140 oC-170 oC, H2SO4 concentration of 0.5wt%-2wt % and solids loading of 4-14wt %. The solids loading for xylan experiments were determined by standardizing the xylan reaction against the xylose reaction considering only the xylose composition of xylan (xylose-equivalent). The range of conditions were selected with reference to literature to obtain data that were relevant to industrial processes. Statistical analysis of the results showed that temperature and acid concentrations demonstrated significant effect on the reaction. However, it was found that the effect of solids loading on the reaction was insignificant. Based on the results, it was determined that the xylan conversion process is described by a kinetic model consisting of a two-step first order reaction, whereas the conversion process for xylose consisted of a single step first order reaction model. The main difference in the models was found to be the xylan hydrolysis step that precedes xylose dehydration in the xylan conversion reaction. This hydrolysis step was found to be fast compared to the xylose dehydration resulting in xylose accumulation within 5minutes of the reaction. The dehydration reaction (in xylan conversion process) was found to be the rate determining step of the reaction relative to the fast hydrolysis step with 98kJ/mol and 55 kJ/mol activation energies, respectively. The xylose dehydration in both xylose and xylan conversion process can be described by a first order single step reaction without any side product formation and degradation reaction. Consequently, it was determined from the models that xylose condensation degradation reactions were negligible in the range of condition investigated in this study. The activation energies of xylose dehydration step for xylan and xylose feed were 98kJ/mol and 95kJ/mol, respectively. Comparing the xylan and xylose conversion to furfural processes, it was determined that the xylan conversion process was generally faster despite the two steps process. Finally, higher furfural yields were observed for xylan compared to xylose at all conditions investigated in this study.