Selective conversion of cellulose to small organic molecules, including carboxylic acids, represents a potential route for upgrading biomass resources to value-added chemical precursors. However, since biomass resources such as cellulose are not soluble in water, the use of a catalyzed system requires a novel reactor design that facilitates slurry flow. As demonstrated herein, the monolith froth reactor is uniquely suited for the conversion of solid materials in a four-phase (solid catalyst, solid reactant, gaseous reactant, and aqueous solution) reaction system. Reactions were performed using a palladium catalyst and 1000 ppm (W) Cellulose, and results were compared with previous experiments conducted over platinum. At 150degreesC, nearly 100% conversion of the cellulose was achieved in approximately 5 h, which compares favorably with results obtained using a platinum catalyst. The palladium catalyst gave a different distribution of intermediate products compared to platinum. For example, acetic acid and malic acid achieved yields of 40 and 80 ppm (w), respectively, using the palladium catalyst. The product selectivity was evaluated under pH control, through the addition of acetic or carbonic acid, and shown to have only a minor effect on the performance of the system.