Metal-Oxide-Catalyzed Efficient Conversion of Cellulose to Oxalic Acid in Alkaline Solution under Low Oxygen Pressure

Conversion of cellulose into value-added chemicals and/or fuels has attracted worldwide attention due to the dwindling fossil fuel reserves and concerns over global warming. Herein, the conversion of microcrystalline cellulose into oxalic acid in homogeneous NaOH solution catalyzed by metal oxides under low oxygen pressure was reported. The effects of metal oxides, reaction temperature, reaction time, and oxygen pressure on the yields of the major products were studied. The results showed that a high yield of organic acids, mainly including oxalic acid, formic acid, glycolic acid, lactic acid, and acetic acid, could be obtained. Catalytic amounts of CuO could effectively improve the yield of oxalic acid. The yield of the oxalic acid could be as high as 41.5% with catalytic amount of CuO at oxygen pressure of 0.3 MPa and 200 °C for 2 h. A tentative reaction pathway for the selective oxidation of cellulose into small molecular organic acids in aqueous NaOH solution was investigated and proposed.