Effect of La_2O_3 promotion on a Ni/Al_2O_3 catalyst for H_2 production in the inline biomass pyrolysis-reforming

摘要

The effect of La2O3 addition on a Ni/Al2O3 catalyst has been studied in the biomass pyrolysis and in-line catalytic steam reforming process. The results obtained using homemade catalysts (Ni/Al2O3 and Ni/La2O3-Al2O3) have been compared with those obtained using a commercial Ni reforming catalyst (G90LDP). The pyrolysis step has been performed in a conical spouted bed reactor at 500 degrees C and the reforming one in a fluidized bed reactor placed in-line at 600 degrees C, using a space time of 20 g(catalyst) min g(volatiles)(-1) and a steam/biomass ratio of 4. The Ni/La2O3-Al2O3 catalyst had a better performance and higher stability than G90LDP and Ni/Al2O3 catalysts, with conversion and H-2 yield being higher than 97 and 90%, respectively, for more than 90 min on stream. Nevertheless, conversion and H-2 yield decreased significantly with time on stream due to catalyst deactivation. Thus, the deactivated catalysts have been characterized by N-2 adsorption-desorption, X-ray diffraction (XRD), temperature programmed oxidation (TPO), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Coke deposition has been determined to be the main cause of catalyst deactivation, with the structure of the coke being fully amorphous in the three catalysts studied.