Abstract:
Bio-oil from pyrolysis typically has large amount of oxygenated compounds, which significantly affects on quality of bio-oil. This research focused on investigating catalytic effect of alkali and alkaline earth metals on deoxygenation of bio-oil during hydrothermal pyrolysis of Giant Leucaena wood. Experiments were conducted in an auto-clave reactor. The influences of temperature in range of 300 to 425℃, holding time, water to biomassmass ratio and type of catalysts (K₂CO₃, Na₂CO₃, Ca(OH)₂, CaO) were investigated in terms of bio-oil yield and oxygen content in the bio-oil. The results showed that bio-oil yield was increased with increasing temperature from 300 to 375℃ and reached the maximum value at 375℃. Bio-oil yield was decreased when temperature was up to 425℃. The oxygen content was gradually decreased with increasing temperature. An increase in holding time was found to slightly decrease the oil yield and the oxygen content. In contrast, both values tended to become higher with increasing the water to biomassmass ratio. The presence of Ca(OH)₂gave the maximum bio-oil yield of 6.49 wt% (oxygen content of 10.57 wt%) while the presence of K₂CO₃ gave the lowest oxygen content at 8.02 wt% (bio-oil yield 5.54 wt%). Therefore, it can be concluded that the presence of alkali and alkaline earth metals in the hydrothermal pyrolysis enhanced deoxygenation whereas it has no effects on the bio-oil yield.