Factors affecting the reactivity of coal chars during gasification, and indices representing reactivity

Recently, interest in catalytic gasification of carbon has expanded rapidly. In consequence of the volume and diversity of this interest, there is a need to collate, summarize, and interpret the available information on the mechanism of gasification catalyst action.

The Mechanism of the Catalytic Gasification of Coal Char: A Critical Review

Structural and compositional transformations of biomass chars during combustion

From molecular orbital calculations, a unified mechanism is proposed for the gasification reactions of graphite by CO2 and H2O, both uncatalyzed and catalyzed by alkali and alkaline earth catalysts. In this mechanism, there are two types of oxygen intermediates that are bonded to the active edge carbon atoms:  an in-plane semiquinone type, Cf(O), and an off-plane oxygen bonded to two saturated carbon atoms that are adjacent to the semiquinone species, C(O)Cf(O). The rate-limiting step is the decomposition of these intermediates by breaking the C−C bonds that are connected to Cf(O). A new rate equation is derived for the uncatalyzed reactions, and that for the catalyzed reactions is readily available from the proposed mechanism. The proposed mechanism can account for several unresolved experimental observations:  TPD and TK (transient kinetics) desorption results of the catalyzed systems, the similar activation energies for the uncatalyzed and catalyzed reactions, and the relative activities of the alkali ...

Shang Jung Yuh

Papers

FTIR studies of potassium catalyst-treated gasified coal chars and carbons

Kinetic and FT-i.r. studies of the sodium-catalysed steam gasification of coal chars

K2CO3-catalysed steam gasification of supercritical extracted chars