Hydrothermal decomposition of xylan as a model substance for plant biomass waste – Hydrothermolysis in subcritical water

Beech wood xylan, as a model substance for hemicellulose contained in plant biomass waste, was subjected to thermohydrolysis in subcritical water. The composition of the product fractions obtained as a result of its hydrothermal decomposition was studied: the water fraction, the oil fraction and the solid fraction of charred post-reaction residue. An increase in temperature favors xylan thermohydrolysis, leading to the production of saccharides – the products of its hydrolytic depolymerization. The yield of the saccharides contained in the water-soluble product fraction reaches it maximum value at 220 °C and 235 °C, with the retention time of 0 min. Both extending reaction time up to 30 min and further increasing the temperature favor the occurring of secondary reactions – saccharide decomposition – leading to the production, among others, of carboxylic acids, furfurals and aldehydes, and their further carbonization and gasification.

► Xylan as model substance for plant waste biomass in hydrothermolysis.
► Xylose was obtained with the yield of 36.3% at 235 °C with holding time of 0 min.
► Raw product containing xylose can be applied in the fermentation leading to bioethanol.
► Higher reaction temperatures and times favored secondary reactions.
► The secondary products can be directly applied as fuel supplements.