Development of a method for separation of aldoses and ketoses via selective adsorption

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Chemical industry depends nowadays on naphtha-resources, though launching sustainable processes based on renewable feedstocks has been in progress. Dramatic differences in the chemical composition of oil- and biomass-derived compounds reflect in considerably different physical properties, such as polarity, volatility, and hydrophilicity/hydrophobicity. As a result, conventional methods for product recovery, such as distillation, are not suitable for isolation of highly-polar biomass-based compounds. Consequently, a number of newly-developed processes on biomass utilization cannot be scaled up, since efficient product recoveries are still missing.This project focuses on separation of aldoses and ketoses. Aldoses, saccharides with an aldehyde group, are highly available from biomass. Aldoses can be converted into ketoses using biotechnological or chemo-catalytic processes. The ketoses are in demand as sweeteners, precursors for cosmetic and pharmaceutical formulations, as well as substrates for platform chemicals. Isomerization of glucose (aldose) into fructose (ketose) is the most prominent example of such aldose-ketose transformations. The yield of a ketose is thermodynamically limited, which presents a key point of isomerization processes. Therefore recovery of a ketose from aqueous solution containing an equilibrium aldose-ketose mixture poses a major challenge, because ketoses are non-volatile and temperature-sensitive.This project aims at developing an efficient method for recovery of ketoses from aqueous solution of aldoses-ketoses using a selective adsorption of ketoses on polymers, containing phenylboronic acid moieties. The separation takes place owing to selective and reversible binding of ketoses to the polymers, whereas aldoses remain in the solution. Ketoses can be desorbed from the polymers under acidic conditions. In order to optimize the polymer structure, materials with different properties, such as nature of phenylboronic moiety, boron content, and crosslinking degree, will be synthesized. The influence of these properties on sorption capacity and selectivity of the separation will be investigated using a number of model aldose-ketose mixtures: glucose-fructose, lactose-lactulose, galactose-tagatose, etc. The experiments will be conducted under batch as well as continuous conditions. The long-term stability of the boron-containing polymers under sorption/desorption conditions will be studied. Ultimately the investigation enables optimizing the chemical composition of boron-containing polymers and sorption/desorption conditions in order to achieve a highly-selective separation of ketoses. The results of the study should present a basis for a potentially energy-efficient and simple separation technique for biorefineries.