Kinetics and mechanism of catalytic carbon gasification

Abstract

The evidence of the carbon bulk diffusion mechanism, operating in catalytic carbon gasification, is summarized. Linking visual and structural observations (transmission electron microscopy and X-ray diffraction) with comprehensive kinetic studies offers a good basis to understand the details of the phenomenological behavior. The role of the catalyst nanoparticles in catalytic coal/coke gasification and in graphene reactions is briefly reviewed. Knowledge of the solid-state phases operating under steady-state reaction and of the ''sintering like" catalyst-carbon contact is essential to understand the most likely reaction sequence: 1st step - carbon dissolution; 2nd step - C bulk diffusion; 3rd step - surface reaction of emerging C atoms with the reactant gas. Kinetics and preliminary solid-state changes observed in graphite gasification and in coke/coal gasification leads to the conclusion that they follow the same mechanism. Using an analogy with proton exchange membranes in fuel cells: catalytic carbon gasification is promoted by carbon exchange moving nanoparticles. A better understanding of the mechanism may lead to improvements in industrial processes.