Steam- and CO2-activated carbons from a Spanish HV bituminous coal char wer
e obtained at 800-900 degrees C in a batch laboratory scale fluidized bed r
eactor. The N-2 and CO2 adsorption isotherms and scanning electron microsco
py allow for sample characterization. The development of porosity upon acti
vation, using a fluidized bed reactor, is different depending on the activa
ting agent. A much better activation development is attained with steam. Th
us, total micropore volume linearly increases with the activation degree, a
ttaining an apparent specific surface area of 1150 m(2)/g at 50% burnoff fo
r steam-activated carbons. Although CO2 activation also produces a linear i
ncrease vs burnoff, much lower pore volume values are obtained, reaching an
equivalent specific surface area of only 800 m(2)/g at 50% burnoff. SEM an
alysis indicates that CO2 produces external burning of the carbon particles
. This different behavior of CO2 and steam activation was also observed for
several runs carried out with almond shell char. The explanation of this b
ehavior may be to a partial diffusion control in the CO2 gasification react
ion, under fluidized bed conditions.