The liquefactions of cellulose, rice straw, and red pine were conducted in a batch reaction system in the presence of solid catalysts and several protonic solvents, such as methanol and ethylene glycol. In the solvolysis of cellulose in methanol, methyl-glucopyranosides were the main products formed via the addition of H⁺ and OCH₃^– in the presence of a solid catalyst. The decomposition rates of cellulose in various solvents decreased in the order of water › methanol › ethylene glycol › 1-butanol. This may suggest that the solvents with large self-dissociation constant (K_SH) enhance the solvolysis of cellulose. In addition, the pore structure and acidity of a solid acid catalyst and type of lignocellulosic biomass also affected the solvolysis. The maximum liquefaction rates of rice straw and red pine in ethylene glycol using a sulfated zirconia catalyst at 453 K for 6 h were ca. 78.7% and 97.5%, respectively.