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BACKGROUND: Inulin is a valuable source of high purity fructose. The conversion of inulin to fructose utilizing an advanced sulfonic ion‐exchange resin was previously investigated in detail in a batch reactor study, where a detailed mechanistic model for the reaction kinetics was demonstrated (J Chem Technol Biotechnol 2018;93:224–232). The same catalyst was employed in tailor‐made continuous fixed‐bed reactors in the current work in order to study the feasibility of continuous operation. RESULTS: Two types of reactors were utilized: a single‐bed reactor and a multibed reactor with sample withdrawal between catalyst beds. The results from the single‐bed reactor allowed optimal reaction conditions to be determined which were extrapolated and used for experiments in the multiple‐bed reactor. High yields of fructose (75%) were obtained with the multiple‐bed reactor without any degradation products. Detailed flow characterization was performed on the reactor system and residence time distribution results were merged with the detailed model for the chemical kinetics obtained from batch reactor studies taking into account mass transfer limitations, in order to obtain a rigorous model for the performance of the continuous reactor. The fit of the mathematical model to the experimental data was very good and this provides a useful tool for further development and scale‐up purposes. CONCLUSIONS: The results of the two related studies highlight the potential of new reactor design strategies towards the realization of more efficient, sustainable and green processes, which can easily be scaled‐up and implemented in bio‐based industry. © 2018 Society of Chemical Industry

Extraction of hemicelluloses with subcritical water is an efficient and environmentally benign way of fractionating biomass, including lignocelluloses. The composition and extraction behavior of hemicelluloses from wood depends significantly on the species, which affects the obtained product and the requirements of the extraction process. The current work focuses on the extraction of hemicelluloses from three chemically and structurally different, interesting and economically important tree species namely stone pine ( Pinus pinea ), holm oak ( Quercus ilex ), and Norway spruce ( Picea abies ), for which the literature on holm oak and stone pine hemicelluloses is almost non-existent. The work was performed with identical experimental methods, to obtain completely comparable results. The effect of temperature, raw material and solid-liquid ratio on the extraction kinetics, pH and molar mass, was studied. The results revealed significant differences in the extraction behavior and composition of the different species.

Hemicellulose O-acetyl-galactoglucomannan (GGM) is the main noncellulosic water-soluble polysaccharide in the coniferous softwood Norway spruce, consisting of anhydro-galactose, -glucose, and -mannose. Acid hydrolysis of GGM has been studied in a continuous tube reactor to obtain these sugars under industrially relevant conditions. The reaction was performed under atmospheric pressure at 90°C and 95°C, and hydrochloric acid (HCl) served as catalyst. The influence of the reaction parameters, such as acid concentration (pH), temperature, concentration of the substrate, as well as catalyst and reactant flow rates, has been studied on the conversion efficiency and product distribution. Continuous production of monomeric sugars was achieved without formation of low-molecular by-products. The GGM conversion was high with HCl as catalyst, at 95°C, and a pH of 0.3. The main hydrolysis products were mannose, glucose, and galactose monomers. Minor amounts of sugar dimers were detected among the products. The experimental results are described with a laminar flow model for the continuous reactor.