Abstract
The hydrolytic hydrogenation of xylan to xylitol by a one-pot process was studied in detail in a batch reactor. The reaction was catalyzed by a combination of diluted sulfuric acid and precious metal Ru on carbon powder. Process parameters were varied between 120–150°C, while maintaining constant hydrogen pressure at 20 bar and an acid concentration equivalent to pH 2. The xylan solution consisted of 1 wt% beechwood powder (Carl Roth, >90%) in deionized water. Sulfuric acid was added to the solution until pH two was reached, then the 0.3 wt% catalyst powder (5% Ru on Act. C) was added and the solution was put into the batch reactor. The first approach of kinetic modeling began with conventional first-order kinetics and compared this to a more complex model based on Langmuir–Hinshelwood kinetics. The xylan and xylitol data reached a good fit. However, the modeling results also showed that the rate-limiting step of xylose-formation was still not represented in a satisfactory manner. Therefore, the model was adapted and developed further. The advanced model finally showed a good fit with the intermediate product xylose and the target product xylitol. The overall modeling methods and results are presented and discussed.
Highlights
Since the start of the ongoing debate on global warming, the research in many scientific fields has focused more and more on environmentally friendly and sustainable approaches
The modeling approach for the reaction kinetics seems to call for the application of Arrhenius kinetics, considering the catalytic hydrogenation via Ruthenium on Carbon powder
The experimental data points towards an optimal process window for the hydrolytic hydrogenation of xylan to xylitol
Summary
Since the start of the ongoing debate on global warming, the research in many scientific fields has focused more and more on environmentally friendly and sustainable approaches. This trend led to the development of biorefinery concepts with the aim of producing fuels and fine chemicals from renewable resources. This “green chemistry” could use waste plant material from the agricultural and wood industry as feedstock. The conversion of hemicelluloses is usually conducted with the aim to convert them to monosaccharides. These monosaccharides are valuable chemicals for food, cosmetic and pharmaceutical industries. They might be further converted into polyols, known as sugar alcohols. Xylitol can be derived from the monosaccharide xylose, the main structural component of xylan
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