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Producción Científica, Background: The hydrothermal reduction of CO2 using organic molecules such as alcohols can produce renewable fuels and platform chemicals, such as formic acid (FA). If the process is performed using glucose as reductant, the yield is especially high, because FA is selectively produced both by reduction of CO2 and by degradation of glucose degradation in alkaline hydrothermal media. Methods: This article analyzes the origin of formic acid using NaH13CO3 as CO2 source, assisted by HPLC and 13C-NMR to study the origin of FA. Significant findings: Results show that two reactions pathways take place: the first one, at short reaction times, consists on the decomposition of glucose into formic acid and other by-products, achieving low yield to FA-13C, whereas longer reaction times lead to a higher yield to FA-13C. Similarly, temperature plays an important role, being 300°C the optimal. Further reactions were performed using the main by-products of previous reactions (acetic acid, lactic acid, glycolaldehyde and glyceraldehyde) as reductants to understand the reaction mechanisms. Results indicate that the reduction pathway of NaHCO3 take place by oxidation of the by-products rather than by the oxidation of glucose itself, needing long reaction times to achieve significant high ratios of FA-13C/ total FA., Junta de Andalucía - Fondo Europeo de Desarrollo Regional (project CLU-2019-04), Ministerio de Ciencia, Innovación y Universidades (projects RTI2018-097456-B-I00 and PGC2018-099470-B-I00)

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.