The Controllable Synthesis Of Mesoporous Ceria And Cerous Phosphate

The Lanthanon and its compounds, because of its 4f electronic characters, have special performance. CeO₂ is widely used as a promotor in three-way catalysts (TWC) for the elimination of toxic auto-exhaust gases, low-temperature water-gas shift reaction, high-energy efficiency fuel-cells and oxygen sensors. CePO₄ has potential application in the area of ion-exchanger, fluorescence, conductor, catalysis and so on.In this study, cerium salt is used as inorganic material, surfactant and organic small molecule as template. Under hydrothermal condition, controlling the type of templates, the pH value, reactive temperature and time, the the ratio of reactants, mesostructrued CeO₂ and CePO₄ were successfully synthesized. The mesostructures, crystal phases, textile characteristics, microscopic patterns, chemical structures and surface chemical properties were characterized by low-angle XRD, XRD, N₂ adsorption-desorption isotherm, TEM, FTIR, and XPS techniques.The results showed that under hydrothermal condition, nitrate cerium(IV) was used as a cerium source, lauryl sodium sulfate (SDS) as the molecular template and urea as a precipitating agent, and the lamellar well-aligned mesostructrue of the cubic fluorite ceria were successfully synthesized. The crystalline phase of the products were cubic fluorite CeO2 with the uniform pore size of 6～7nm. In addition, the products have different crystalline phase and composition as increasing the final pH value of reaction system; And when the final pH values of reaction system were at 5～6, 6～8 and >8 respectively, the crystalline phase of the products were respectively cubic fluorite CeO₂, mixtures of cubic fluorite CeO₂ and hexagonal Ce(OH)CO₃, hexagonal Ce(OH)CO₃.The ceria mesostructured materials were prepared by using non-surfactantsβ-cyclodextrin and triethylamine as the structure directing agents.β-cyclodextrin play a important role of structure directing agents and supporting objects in the formation of mesostructured ceria. The addition of triethylamine was propitious to enhance the order degree of mesoporous structure.Under hydrothermal condition, cerium sulfate (IV) was used as a cerium source, octadecylamine (C₁₈H₃₇NH₂) as the molecular template, and the lamellar well-aligned mesostructrue of the monazite cerium phosphate was successfully synthesized. The CePO₄ was layered mesostructure. The main crystalline phase of the product was monazite CePO₄. By controlling the rate of cerium sulfate and octadecylamine of the reactive system, pore size of the mesostructure CePO₄ varied from 5.46nm to 9.16nm. Themaximal surface area of mesoporous CePO₄ was 113.2 m²Â·g^-1, corresponding to pore volume of 0.25 ml·g^-1.