Hydrothermal and solvothermal synthesis of cerium-zirconium oxides for catalyst applications

Cerium oxide (CeO₂) is a rare earth metal oxide that has high oxygen storage capacity at low temperature. In order to enhance this capacity, as well as its thermal stability, it is necessary to combine CeO₂ with zirconium oxide (ZrO₂). This work focuses on the synthesis of cerium-zirconium oxides by hydrothermal and solvothermal treatment at low temperature to obtain ones suitable for catalyst applications. The possibility of the application of ceria-zirconia oxide to the delignification reaction was investigated. The experiments were conducted at a constant pressure of 5 MPa, constant temperature of 150°C, and constant synthesis time of 2 h, in an autoclave reactor made of SUS 316 with an internal volume of 100 mL. Precursor was prepared from Ce(NO₃)₃ and ZrO(NO₃)₂ at 0.06 M concentration, dissolved in various solvents. The solvents used were water, water/ethanol (70:30 vol/vol), and water/ethylene glycol (70:30 vol/vol). After hydrothermal and solvothermal synthesis, the colloid products were dried at 60°C for 6 h and then calcined at 500°C for 6 h. The characterizations of the particle products were analyzed using SEM and XRD. Furthermore, these products were used for the hydrothermal delignification process of wood biomass. The addition of ceria-zirconia particles dramatically increased the percentage of lignin removal from rapeseed wood up to 97.58%. Based on the results, ceria-zirconia oxide particles are effective for the pre-treatment of wood biomass in bio-refinery applications. Moreover, ceria-zirconia oxides may reduce the use of chemical compounds in the delignification process.