A series of activated carbon aerogel (ACA) bearing sulfonic acid group (SO 3 H) was prepared at different sulfonation temperatures (ACA-SO 3 H (X), X=30, 60, 90, 120, and 150 in Celsius). Palladium catalysts were then supported on ACA-SO 3 H (X) (Pd/ACA-SO 3 H (X)) for use in the decomposition of 4-phenoxyphenol to aromatics. 4-Phenoxyphenol was used as a lignin model compound for representing 4-O-5 bond in lignin. Acidity of Pd/ACA-SO 3 H (X) catalysts played an important role in the reaction. Among the catalysts tested, Pd/ACA-SO 3 H (90) with the largest acidity showed the highest conversion of 4-phenoxyphenol and total yield for main products (cyclohexanol, benzene, and phenol).