Influence of Salts During Hydrothermal Biomass Gasification: The Role of the Catalysed Water-Gas Shift Reaction

Abstract

Biomass Gasification / Salt Effects / Supercritical Water / Water-Gas Shift ReactionNear-critical and supercritical water is an unusual reaction medium with extraordinary properties, varying with temperature and density. This opens the opportunity for new reactions and new technical processes. In the studies of synthesis reactions, total oxidation and biomass gasification interesting effects of salts are observed. These effects are assumed to be caused by complex formation, acidity/basicity or the presence of active hydrogen due to the water-gas shift reaction. The water-gas shift reaction is catalysed by salts and lead to the formation of hydrogen, which might react with other compounds.This article focuses on the salt effects during hydrogen production by biomass gasification in supercritical water. This is a very interesting process to make use of "wet biomass", which is up to now not applied in a technical process. Here salts influenced the main reactions pathways. Possible reasons are discussed.

Hydrothermal Biomass Gasification – Effects of Salts, Backmixing and Their Interaction

“…1)! This assumption is supported by the fact that gasification is enhanced in batch-type experiments when CO is added at the beginning of the reaction for the water-gas shift reaction to take place [21]. Obviously, this results in an inhibition of polymerization and a promotion of cleavage, as is known from liquefaction processes with "active hydrogen".…”

“…The reasons are not yet completely understood. However, there is experimental evidence that all these effects are closely linked to the catalysis of the water-gas shift reaction by alkali salts [20,21]. Apparently, different reaction paths may be affected by the occurrence of reactive intermediate stages of the water-gas shift reaction or by hydrogen in statu nascendi as "active hydrogen".…”

Back in the black: hydrothermal carbonization of plant material as an efficient chemical process to treat the CO2 problem?

“…These approaches aim for the recovery of liquid, 20,21 or gaseous 22,23 fuel intermediates (like glucose, 5-hydroxymethylfurfural, methane, hydrogen etc.) from biomass, while the solid residues were, up until now, mostly treated as undesirable side products.…”

Hydrothermal Disintegration and Extraction of Different Microalgae Species

“…Main fractions of these are alkali metals like Potassium and Sodium. These are known for their catalytic impact [18][19][20][21] and might Energies 2018, 11, 450 3 of 13 change the proportion of liquefied and solid products and thereby the yield of extractable lipids from the HTC char. The influence of this for the given experiments remains a subject to further research.…”