Glucose valorization by hydrothermal process assisted by photocatalysis

Abstract

SSCI-VIDE+CARE:CDURABLE+IBD:FDA:MET:NES:CGUNational audienceBiomass has attracted considerable attention as an abundant carbon source and a promising alternative for fossil resources. The valorization of its simplest molecule (glucose, in aqueous media) has been studied by mean of different processes such as hydrothermal process (HP) and photocatalytic process (PP). HP which is high energy consuming (high temperature and pressure) transforms glucose into a variety of products such as lactic acid, hydroxymethylfurfural, levulinic acid, but in general the transformations suffer from carbon losses due to uncontrolled humins formation … While PP which is low energy consuming (low temperature and pressure) is mainly used to mineralize glucose or to produce hydrogen from glucose. Herein, we studied glucose transformation in aqueous solutions by HP assisted by photocatalysis (HPP) in the presence of a commercial TiO2 anatase catalyst (UV100) with the objective of combining the advantages of the two process: decreasing energy expenditure without carbon loss in uncontrolled humins’ formation. Under inert atmosphere, under 15 bar and 150°C, after 5h, almost complete glucose conversion was obtained for HP and for HPP. However, while the several main products (erythrose, gluconic and levulinic acids) were formed in low selectivity (<15%) with HP, levulinic acid was the major product formed with a selectivity of about 70% with HPP at the same glucose conversion (90%). Beside the formation of levulinic acid by HPP and importantly, in absence of noble metal, we also notice the important formation of H2 (80 µmol at 150 °C) and ethene (40 µmol at 150°C) for prolonged reaction time (24h) whereas they are present at negligible amount (< 0.25 µmol) under hydrothermal process at 150°C and photocatalysis at ambient TOur research shows the interest of this innovative process, associating an activation of a metal free catalyst under pressure, temperature and UV for elaboration of energy (H2, C2H4) and platform molecules such as levulinic acid, a versatile synthetic intermediate, used for example in the synthesis of pharmaceutical compounds but also a photosensitizer used in photochemotherapy or us biofuel additive