Preparation And Synthesis Mechanism Of Mesoporous La-Co-Ce-O Oxide With Adjustable Pore Size

Currently, mesoporous metal oxide is a kind of most attractive new mesoporous materials. Since their variable valence, nano-characteristics of materials and large pore structure, mesoporous metal oxides are probable to open up new application areas, and display good prospect of application that silicon-based mesoporous material does not have, and has potential applications in catalysis, photics, electricity and magnetism, etc. However, it synthesis is more complexer than silicon-based materials and the synthesis mechanism is not sophisticated. Therefore, it is significant to research on preparation technology of mesoporous metal oxide. In this paper, mesoporous La-Co-Ce-O oxide was prepared successfully by decomposition of organic templates. Mesoporous La-Co-Ce-O oxide with adjustable pore size was prepared by changing the length of surfactants' carbon chain and adding organic auxiliaries, and the synthesis mechanism was investigated. Main research conclusions are as follows:(1) Mesoporous La-Co-Ce-O oxide was prepared using surfactant cetyl trimethyl ammonium bromide(CTAB) as template agent, and the process parameters effects such as pH value, amount of CTAB and H₂O, calcination temperature, hydrothermal conditions were investigated. The results show that preparation parameters have great influence on the specific surface area and pore structure of mesoporous oxide, however the influence on crystal structure is not obvious.(2) Mesoporous oxide with adjustable pore size is prepared with surfactant cetyl trimethyl ammonium bromide (CTAB) as template agent with OP addition. Results show that with increase in OP amounts, pore size increases and specific surface area decreases.(3) Mesoporous oxide with adjusting pore size can be achieved through changing the length of surfactants' carbon chain. Results show that pore size decreases with shorter surfactants' carbon chain and increases with more C12TAB addition.(4) Particle size distribution tests show that the particle size of micelle increases with OP addition and increase of surfactants' carbon chain. Particle size distribution testing validates the mechanism of adjusting pore size. As the addition of organic addition or increasing of surfactants' carbon chain, the volume of micelle increases, so does the diameter, which leads to increase of pore size. (5) In micelle solution, number of surfactants monomer forms micelle structure, micelle out layers and the anti-ion make up of diffusing electric double layer. When anti-ions in diffusing electric double layer were all pressed in stern, Zeta potential is zero, and the micelle is isoelectric. This pH value agrees with that suitable for preparation of mesoporous oxide.