(265b) Effect of Alkali Metals on Lignin Pyrolysis and Gasification

Lignin, the second most abundant naturally occurring material is a major constituent of biomass. Lignin is a waste produced during chemical pulping of wood and it is currently burned in recovery boilers to recover cooking chemicals and to produce steam. It is also produced during saccharification and fermentation of lignocellulosic biomass to ethanol. Lignin can be gasified to produce synthesis gas which can be converted to chemicals and fuels. This study focuses on the effect of alkali metals on pyrolysis and gasification of lignin. Three types of lignin were impregnated with varying amounts of alkali solutions at ambient conditions and were pyrolyzed and gasified at temperatures up to 800 °C. Alkali metals decreased the devolatilization rate and mass loss and increased the rate of gasification for all the lignins. Pyrolysis of all the lignins showed similar behavior until 600 °C but secondary reactions occurred at higher temperature for lignin with high ash content. These reactions were found to be due to interactions of char carbon with alkali metals salts. Gasification reactions are catalyzed by Na2CO3 and Na2SO4 with the rate increase being proportional to the amount of sodium added. The mechanism of alkali impact on pyrolysis and gasification is discussed.