Effect of Potassium Carbonate Catalyst on Pyrolysis of Milicia excelsa in a Fixed Bed Reactor

Abstract

The effect of potassium carbonate catalyst on the products distribution from pyrolysis of Milicia excelsa (Iroko) at various temperatures (400, 500 and 600 oC) was investigated. Milicia excelsa sawdust was obtained from a sawmill in Ogbomoso, South-Western Nigeria and was sundried for five days in order to reduce its moisture content. Catalytic pyrolysis of the sawdust was performed with different amounts of catalyst (10, 20, 30 and 40 wt.%). Non-catalytic pyrolysis was also performed for the same temperatures and the products distributions from both batches were compared. Char yield generally increased with increase in catalyst amount for all the temperatures considered. Tar yield did not follow any definite pattern with increasing amount of catalyst as different trends were obtained for different temperatures. Gas yield generally decreased with increase in catalyst amount in the feed. Char yields from non-catalytic experiments were higher than those obtained from catalytic runs, with the highest value of 68% at 400 oC. Tar yields from catalytic pyrolysis were higher than those from non-catalytic process at 400 oC (biomass/catalyst ratio of 90/10) and at 500 oC (biomass/catalyst ratios of 70/70 and 60/40), the highest yield being 29.47% at 500 oC and biomass/catalyst ratio of 60/40. Gas yields from catalytic pyrolysis were higher than those from non-catalytic runs except at 500 oC (biomass/catalyst ratio of 60/40), the highest being 51.3% at 600 oC (biomass/catalyst ratio of 90/10). By making use of appropriate biomass/catalyst ratio and temperature, the yield of liquid fuel from catalytic pyrolysis of Milicia excelsa can be increased.Keywords— Catalyst, potassium carbonate, pyrolysis, biomass, product distribution