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Catalytic gasification of pine-sawdust: Effect of primary and secondary catalysts

Abstract:

Pine sawdust steam gasification in a fixed double bed reactor and continuous flow was investigated. K<inf>2</inf>CO<inf>3</inf> as primary catalyst and cobalt supported on γ-Al<inf>2</inf>O<inf>3</inf> and SiO<inf>2</inf>-Al<inf>2</inf>O<inf>3</inf> as secondary catalyst was investigated. Thermal and catalytic steam gasification was compared. The effect of the support in tar yield and the H<inf>2</inf>/CO ratio was pursued. It is noteworthy to observe that the primary catalyst increases the biomass gasification. It is also marked the total consumption of CH<inf>4</inf> species by the primary catalyst. The catalysts (K<inf>2</inf>CO<inf>3</inf> and K<inf>2</inf>CO<inf>3</inf>-Co/γ-Al<inf>2</inf>O<inf>3</inf>) reduced tar formation from 11% in the thermal gasification to a value of 2.0% and 0.5% respectively. This tar yield reduction could be explained due to the action of potassium actives species of the primary catalyst combined with the lower acid strength of the support; high metal dispersion of cobalt species and the higher fraction of metallic cobalt species in Co/γ-Al<inf>2</inf>O<inf>3</inf> catalyst. The catalysts decrease the formation of CO<inf>2</inf> from 21% in the thermal gasification to values on the order of 3%. The highest H<inf>2</inf>/CO ratio with a value of 1.6 was obtained by K<inf>2</inf>CO<inf>3</inf>-γ-Al<inf>2</inf>O<inf>3</inf> catalytic system. The presence of cobalt supported catalysts favored hydrogen consumption reactions such as reverse water gas shift reaction.