Catalytic effects of potassium on lignin steam gasification with γ-Al2O3 as a bed material

Abstract

The effects of potassium on the reactivity of biomass-char steam gasification with the presence of a porous material were investigated by using a thermogravimetric reactor with high-heating rates. Lignin was employed as a char-rich biomass model compound. The potassium carbonate (K2CO3) was added to lignin and a mixture of lignin and γ-Al2O3 porous particles by means of aqueous impregnation. The effects of K2CO3 and γ-Al2O3 addition on pyrol- ysis of lignin and steam gasification of lignin-derived char were evaluated in terms of lignin conversion and the gaseous products. Results showed that K2CO3 slightly increased the steam gasification rate of lignin-derived char, but it did not influence the conversion in both the pyrolysis and steam gasification steps. In addition, tar was reduced by adding K2CO3 because of the increment of carbon conversion to gas product. The presence of γ-Al2O3 was found to induce the lower reactivity of resulting char after pyrolysis, reducing the gasification rate and conversion. A significant im- provement in gasification conversion was observed with the presence of both K2CO3 and γ-Al2O3. Especially, almost complete gasification was achieved at a reaction temperature of 1,073 K.