Hydrothermal conversion of glucose in multiscale batch processes. Analysis of the gas, liquid and solid residues

• Degradation of glucose is achieved at low temperature (250 °C) using slow heating rates (below 10 °C min−1).
• Production of valuable platform molecules (5-HMF) at subcritical temperatures during heating.
• Gasification of glucose improved at high temperature in supercritical domain.
• Maximal efficiency of 1.5 mol H2 per mol glucose at 600 °C (5 wt% glucose, 0.5 wt% catalyst, 25 MPa, 60 min).
• Amorphous solid residues with spherical carbonaceous particles obtained by SCWG of glucose solution.

Hydrothermal conversion is an interesting process to transform (very) humid biomass into high energy vectors or valuable products in the liquid or solid state. In the supercritical domain, water becomes a solvent for organics as well as a reactant, and thus the cellulosic content is effectively hydrolyzed into glucose, largely considered as its model molecule.The kinetics of glucose decomposition during the heating step in the batch reactor were investigated through the analysis of glucose concentration. Glucose reacts totally before reaching the supercritical point of water. Among the operating parameters that influence supercritical water gasification, this paper presents only the effect of reaction temperature through gas composition, liquid carbon content and structure of the solid. Glucose gasification in a batch process (5 wt% glucose, 0.5 wt% catalyst, 600 °C, 25 MPa, 60 min) produced 1.5 mol of hydrogen per mol of glucose. The gas has energetic properties (H2, CH4, C2H6) while the liquid contains substances that could be used as platform molecules (5-HMF). The solid phase is composed of carbon (almost pure) in two distinct phases: spherical nanoparticles and an amorphous phase.

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