DEVELOPMENT OF NANO-NiO/Al2O3 CATALYST TO BE USED FOR TAR REMOVAL IN BIOMASS GASIFICATION

摘要

The objective of this study is to develop a novel supported nano-NiO catalysts for tar removal in biomass gasification/pyrolysis, to significantly enhance the quality of the produced gases. For this purpose, the supported nano-NiO/γ-Al2O3 catalyst was prepared by deposition-precipitation (DP) method. Different analytical approaches such as XRD, BET, TEM and SEM/EDX were used to characterize the synthesized catalysts. The results showed that the prepared nano-NiO/γ-Al2O3 catalysts had an egg-shell structure with a loading of NiO in catalysts over 12 wt %, and they had also a higher BET surface area over commercial nickel based catalysts. The active components of catalyst were spherical NiO nanoparticles coated on the surface of supports with a size range of 12～18 nm. Furthermore, the activity of the catalysts to remove tar in the process of biomass pyrolysis was also investigated using a bench-scale combined fixed bed reactor. The experiments demonstrated that the tar yield after adding catalysis was reduced significantly. The tar removal efficiency reached to 99% for catalytic pyrolysis at 800℃, while the gas yield after adding catalysis increased markedly. Meanwhile, the compositions of gas products before and after adding catalysis in the process also changed significantly. The percentages of CO2 and CH4 in the product gas after addign catalysis were obviously reduced whilst those of the valuable H2 and CO increased sharply. Therefore, using the prepared NiO/γ-Al2O3 catalyst in biomass gasification/pyrolysis can improve significantly the quality of the produced gas and meanwhile eliminate efficiently the tar generation.