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CHAPTER 19

Hydrothermal Events Occurring During Gasification in Supercritical Water

Supercritical water is an excellent green solvent for many chemical reactions such as oxidation, gasification, pyrolysis and liquefaction. It is a promising reaction medium for the generation of hydrogen from biomass through a series of degradation reactions, such as hydrolysis, steam reforming, water–gas shift reaction, hydrogenation and methanation. Supercritical conditions at temperatures greater than 374 °C and pressures above 22.1 MPa are found helpful to degrade a variety of biomasses and organic wastes. The chapter gives an overview of the thermo-physical properties of supercritical water including temperature, pressure, density, dielectric constant, viscosity, diffusivity, ionic products and free radicals. The chapter reviews the hydrothermal degradation routes of different biomass model compounds, such as cellulose, hemicellulose, lignin, proteins, lipids, fatty acids, alcohols and sewage sludge. The candidacy of each of these substrates for conversion to hydrogen through supercritical water gasification is discussed in terms of promises and challenges.

Print publication date: 28 Aug 2018
Copyright year: 2018
Print ISBN: 978-1-78262-880-4
PDF eISBN: 978-1-78801-354-3
ePub eISBN: 978-1-78801-518-9
Citation:
From the book series:
Green Chemistry Series