Effects of Fluid Velocity on Solubilization of Total Mass, Xylan and Lignin for Hot Water Only and 0.05wt% Sulfuric acid Pretreatment of Corn Stover Thayer School of Engineering Dartmouth College Hanover, New Hampshire 03755

Objective Our previous study showed removal of hemicellulose, lignin, and total mass all increase with flow rate for both hot water only and very dilute acid pretreatment of corn stover, implying fluid velocity may play an important role in promoting hemicellulose hydrolysis. This study is to evaluate the impact of fluid velocity on solubilization of total mass, xylan and lignin for both hot water only and 0.05wt% sulfuric acid pretreatment of corn stover.

Materials and Methods Substrate: Corn stover from Harlan, Iowa provided by NREL. A set of 10.9mm ID  180mm L, 15.7 ID  87mm L, and 21.2 ID  47mm L tubular reactors was used to investigate impact of fluid velocity on both hot water only and very dilute sulfuric acid (0.05wt%) pretreatment. Each reactor has the same internal volume of 16.8mL, and can load about 1.5g dry biomass. When passing hot water or very dilute acid at the same flow rate of 10mL/min, average liquid-solid contact time in each reactor is supposed to be the same (1.68min), but fluid velocity in each reactor is 10.7,5.2 and 2.8cm/min, respectively. Pretreatment conditions: Hot water only, 200 o C, 16minutes, 10mL/min; 0.05wt% acid, 180 o C, 8 and16minutes, 10mL/min.

Effect of Fluid Velocity on Total Mass Remaining in Solid Residue for 0.05wt% Sulfuric Acid and Hot Water Only Pretreatment of Corn Stover with a Flow Rate of 10mL/min

Effect of Fluid Velocity on Lignin Removal for 0.05wt% Sulfuric Acid and Hot Water Only Pretreatment with a Flow Rate of 10mL/min

Effect of Fluid Velocity on Xylan Remaining in Solid Residue for 0.05wt% Sulfuric Acid and Hot Water Only Pretreatment with a Flow Rate of 10mL/min

Effect of Fluid Velocity on Total Xylose Yield for 0.05wt% Sulfuric Acid and Hot Water Only Pretreatment with a Flow Rate of 10mL/min

Summary Increasing fluid velocity increased removal of total mass, xylan, and lignin, especially for 0.05wt% sulfuric acid pretreatment in the first 8 minutes implying that mass transfer or other physical factors may be important in hemicellulose hydrolysis. –For example, when fluid velocity was increased from 2.8 to 10.7cm/min, total mass dissolution increased from 42 to 52%, xylan dissolution increased from 73 to 94%, and lignin removal increased from 35 to 53% for 0.05wt% sulfuric acid pretreatment of corn stover at 180 o C after 8minutes. At the same time, total xylose recovery increased from 60 to 91%. Fluid velocity has a small effect on hot water only pretreatment although the reason is not yet clear.