Effects of Lignin Content and Temperature on the Properties of Hybrid Poplar Bio-Oil, Char, and Gas Obtained by Fast Pyrolysis

Eight genetically different hybrid poplar samples with varying lignin content were pyrolyzed at 500 °C using a micropyrolysis unit, which was directly connected to a GC/MS. Four of these hybrid poplar samples with a range of lignin content were then pyrolyzed at temperatures of 550 and 600 °C to determine the effects of pyrolysis temperature on product distribution among bio-oil, char, and gas. At a pyrolysis temperature of 500 °C, an increase in poplar lignin content from 17% to 22% decreased the relative bio-oil yield from 73% to 65%, increased the char yield from 17.5% to 27.2%, and decreased the yield of lignin-derived phenolic species in the bio-oil by 3%. At the higher pyrolysis temperature of 600 °C, there was neither a decrease in the yield of bio-oil nor an increase in the char yield, and there was an increase in the relative abundamnce of bio-oil phenolics compared to the results obtained at 500 °C. According to these results, higher temperatures are needed to increase the yield of bio-oil and the content of phenolic species in bio-oil.