Effects of FeCl3 and air pre-oxidation on char structure and pore development during activation

A series of the activated carbon with low burn-off and high specific surface area from Jixi bituminous coal were prepared by air pre-oxidation at 200 ℃ and adding iron-based compounds (3% FeCl3 ). The changes of macro-structure and microstructure of bituminous chars during pyrolysis and activation were obtained by FTIR,SEM ( scan-ning electron microscope), nitrogen adsorption, XRD ( X-ray diffraction) and Raman spectroscopy. The effects of FeCl3 and air pre-oxidation on char structure and pore development during activation were investigated. Results show that the increase of the type and quantity of oxygen functional groups and the removal of aliphatic chains are observed gradually with the increase of oxidation time from 15 to 48 h. The evolution of different oxygen-containing structures and the catalysis of FeCl3 result in the disordered conversion of microstructure and the formation of more porosity dur-ing pyrolysis,however,the thermal desorption behavior of oxygen-containing structures with different thermal stabilities plays a more important role on the changes of char structure. The pore formation of JX-800 and JXFe-800 follow a hi-erarchical development from the surface to the core during activation. Because of the difference in microstructure and the existence of Fe based compounds,JX-800 and JXFe-800 have the hierarchical pores and similar specific surface area (549. 64 and 600. 47 m2 / g) at the lower burn-offs of 53. 7% and 43. 7% ,respectively,and severe carbon loss at the particles’ surfaces is observed for JX-800 -53. 7. The pore formations of JXFeO15 and JXO48 with more pores and disordered microstructure which promote the diffusion of activated gas follow a non-hierarchical development from the external and internal particles simultaneously,thereby hindering the severe carbon losses at the particle surface. Because of Fe based compounds which promote the reaction between activated gas and aromatic structure,JXFeO15 has a high value of SBET ( 906. 05 m2 / g) at a low value of burn-off 30. 9% , compared with the values of SBET (809． 69 m2 / g) of JXO48-800 char at a value of burn-off 32. 5% .