Evolution of pore structure and surface characteristics of activated coke during circulations of desulfurization and regeneration

The experiments of desulfurization-regeneration (D-R) with commercial activated coke on a fixed-bed reac- tor in the simulated flue gas were conducted for ten cycles. The desulfurization capability of the activated coke was de- termined and calculated. Surface chemistry and morphology of the activated coke before and after regeneration were characterized by XPS (X-ray Photoelectron Spectroscopy) and SEM (Scanning Electronic Microscopy),respectively. Adsorption / desorption isotherm of nitrogen at 77 K of the activated coke was plotted,and thus the BET specific area and pore volume of the activated coke were obtained. Results show that with the proceeding of D-R cycle the BET spe- cific area and pore volume of the activated coke are on a rising trend,increasing from 312. 3 to 441. 4 m2 / g and from 0. 147 9 to 0. 203 0 cm3 / g,respectively,meanwhile a gradual increase of oxygen content from 15. 63% to 19. 09% on surface of the activated coke can be observed;an unfavorable decrease of the desulfurization capability from 101. 29 to 22. 56 mg / g accompanied the increase of pore volume,BET specific area and surface oxygen content. During the first six D-R cycles there is an inverse relationship between the desulfurization capabilities and surface oxygen content on the surface of the activated coke. It is the enhancement of acidity of surface that inhabits SO2 chemisorptions on the ac- tive sites,which results in the progressive loss of desulfurization ability.