A preliminary Raman spectroscopic perspective for the roles of catalysts during char gasification

Abstract

How a catalyst would speed up gasification is fundamentally important for the development of efficient gasification technologies. It is particularly crucial for the efficient use of catalytic species inherently present in low-rank coal and biomass. This study aims to gain insights about the catalytic gasification reaction mechanisms through tracing the changes in char structure during gasification with FT-Raman spectroscopy. A Victorian brown coal was acid-washed to remove its inherent alkali and alkaline earth metallic species. The raw coal and the acid-washed coal were independently subjected to gasification at 800°C under different gasifying conditions (with oxidising and/or reducing atmosphere). Our FT-Raman results revealed that, regardless of the coal type, oxygenation that occurred during char gasification could increase the gasification rate. In addition, catalyst was shown to enhance the gasification rate by participating in the reaction between the char matrix and the radicals derived from the gasifying agents. The presence of a catalyst has made the gasification process to be less selective, due to both reduced selective consumption of char and reduced chance/time for ring condensation.