The liquefaction of lignocellulosic biomass can be either acidor basecatalyzed, although the former is more commonly used. Among all acids investigated so far, concentrated (98%)sulfuric acid has the highest catalytic ability in biomass liquefaction.The effect of different sulfuric acid loadings on the liquefaction of lignocellulosic biomass has been extensively studied.Generally, significant improvements on biomass liquefaction efficiency were observed by increasing sulfuric acid loadings from 1 to 3% (% wt., based on liquefaction solvent). For example, by increasing sulfuric acid loadings from 1 to 3%, the percent biomass residue decreased from approximately 45% to less than 20% for the liquefaction of cotton stalks, wheat straw, and acid-hydrolyzed residues of corncobs.Further increasing sulfuric acid loadings to over3% provided little improvement on biomass liquefaction efficiency, but increased the risk of accelerating detrimental recondensation reactions.[38, 44, 51] For most lignocellulosic biomassmaterials, sulfuric acid loadings of around 3–4% providea good balance between high liquefaction efficiency and effective retardation of detrimental recondensation reactions