Key Compounds of the Hydropyrolysis of Glucose in Supercritical Water in the Presence of K₂CO₃

Abstract

Hydropyrolysis of glucose as a model compound for cellulose in hot compressed water in the presence of K 2 CO 3 at temperatures of 400 and 500 °C and pressures of 30 and 50 MPa in the range of 1.8−16.3 min reaction time is conducted to characterize key compounds of the thermochemical conversion {phenols (phenol and cresols), furfurals [methylfurfural and (hydroxymethyl)furfural], organic acids, aldehydes}. To compare the effect of alkali salts on the pyrolysis of glucose and biomass, the experiments are conducted in the presence of K 2 CO 3, while biomass includes usually alkali salts. Hydrothermolysis of glucose in the presence of K 2 CO 3 increases the hydrogen yield and the amount of phenols under these conditions. The formation and the degradation pathways of phenols and the other compounds that are identified are discussed. A simplified reaction scheme for glucose decomposition is given and used to discuss the role of these compounds. The effect of varying properties of supercritical water such as density, dielectric constant, and ion product on the reaction pathways is also reported.