Hydrothermal liquefaction of corn straw with mixed catalysts for the production of bio-oil and aromatic compounds.

In this study, hydrothermal liquefaction (HTL) of corn straw at different operation temperatures, reaction time and catalyst dosage were investigated, and the main product was heavy bio-oil. Results showed that CuO + NaOH have a synergistic effect in the HTL of corn straw. The product distribution and composition were also studied during the process, in which aromatic compounds achieved the highest proportion in heavy bio-oil. Moreover, the yield of aromatic compounds in hydrothermal products increased under simultaneous action of homogeneous and heterogeneous catalysts. The maximum ratio of aromatic compounds was 89.84% under condition of temperature 230 °C, reaction time 1 h, CuO content 3 g and NaOH 100 mL (1 mol·L-1). GC-MS analysis indicated that the major organic compounds in heavy bio-oil at temperatures between 210 °C and 270 °C were interestingly similar. SEM, XRD, H2-TPR and XPS analysis showed that CuO was completely reduced to copper in the process.