Browsing by Author "Steiner, Andrew Charles Dudley Pringle"

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    Mechanistic and kinetic aspects of furfural degradation in dilute acidic media
    (Stellenbosch : Stellenbosch University, 2019-04) Steiner, Andrew Charles Dudley Pringle; Gorgens, Johann F.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.
    ENGLISH ABSTRACT: Furfural is a renewable platform chemical produced from lignocellulosic biomass. Many chemicals are derived from furfural including furfuryl alcohol, cosmetic ingredients & fragrances, flavour ingredients, nematocides & other agricultural chemicals, biofuels/fuel additives, solvents, resins, nylon, spandex (PolyTHF), etc. Furfural is mostly produced by an acid catalysed dehydration of the xylan in the biomass. The same acid catalyst also catalyses furfural degradation reactions which are known to convert furfural into formic acid and solid, insoluble, heterogeneous, carbonaceous, furan-rich macromolecules known as humins. In this study, furfural degradation was investigated, considering reaction temperatures of 140 °C - 200 °C, initial furfural concentrations of 1.5 wt% - 6 wt% and the sulfuric acid catalyst concentration of 0.5 wt% - 2 wt%. The reaction kinetics of degradation were established by fitting experimental data to the Arrhenius equation. The results showed formic acid as a significant product of furfural degradation. It was found that for each mol of degraded furfural, 0.86 mol formic acid was formed under the conditions of this study. Humins were primarily composed of bifurylic and trifurylic structures and the humins composition was independent of reaction conditions and was uniform under all reaction conditions in the present study. Combustion of humins provides a route to valorise humins but generates only 1.3% of the energy required for furfural production. In a scenario where furfural is produced from biorefinery pre-treatment stages or from pulp mill pre-hydrolysis liquor (not directly from biomass) combustion of humins is a viable application as it facilitates removal of humins which otherwise block up the system. In this study, it was found that initial furfural concentration was the most influential factor towards furfural degradation. Increasing the initial furfural concentration caused an increase in the rate of degradation, more humins were formed and more formic acid was formed. Increasing reaction temperature caused an increase in the amount of humins formed and an increase in the rate of degradation. Increasing the concentration of sulfuric acid caused an increase in the rate of degradation.