Deactivation of a HZSM-5 zeolite catalyst in the transformation of the aqueous fraction of biomass pyrolysis oil into hydrocarbons

The effect of the operating conditions (temperature, space time, and time-on-stream) has been studied in the catalytic transformation of the aqueous fraction of the biomass pyrolysis oil obtained in a conical spouted bed reactor under atmospheric pressure. The results show that (i) the deactivation by coke (reversible) of the HZSM-5 zeolite catalyst is similar to the deactivation of the same catalyst in the transformation of light oxygenates (such as methanol and ethanol) and (ii) the deactivation attenuates as space time is increased. The results of product distribution are in agreement with those obtained in the transformation of the pure oxygenates contained in the pyrolysis oil. In experiments conducted following reaction-regeneration (by coke combustion) cycles, it has been proven that (i) at the reaction temperature of 450 degreesC, deactivation by dealumination of the zeolite in the reaction stage is important and (ii) this deactivation is due to the high water content in the reaction medium. This dealumination causes an irreversible deterioration of the total acidity, although the acid strength of the remaining sites is hardly modified.