In Situ EXAFS of Nickel Species during Pyrolysis of Brown Coals

Abstract

An extended X-ray absorption fine structure (EXAFS) spectroscopy technique has been used to examine the behavior and properties of highly dispersed ion-exchanged nickel species in Loy Yang brown coal samples during pyrolysis. At low loadings (1.4-1.6 wt %) the nickel species aggregate to metal particles at 750 K. At high loadings (6.4-7.5 wt %), however, the nickel species aggregate to metal particles at 650 K. The 100 K higher transition temperature at low nickel loadings is explained by stable nickel containing functional groups and by the low amount of nickel species in the coals.