Research On Synthesis Of TiO₂-Pillared Microporous Manganese Oxide

This paper mainly consists of two sections, review and experiments. The synthesis methods, properties, applications, and development of porous manganese oxide crystals were reviewed in terms of the structural characteristics of porous manganese oxide crystals in the first section (Chapter 1 ). The novel synthesis method of a new TiO₂-pillared porous manganese oxide with a layered structure was described in the experiments section (Chapter 2, and 3), in which layered manganese oxide was acted as precursor and titanium oxide was acted as pillaring agent. Meanwhile, the synthesis conditions were optimized and effects of reaction conditions on titanium pillared products were also investigated.The novel synthesis method of a new TiO₂-pillared porous manganese oxide with a layered structure was described in Chapter 2. H-type layered manganese oxide was obtained by an acid exchange mechanism from its Na-type precursor, which was synthesized by the oxidation precipitation method in sodium hydroxide solution. H-type layered manganese oxide was reacted with titanyl acylate complex ions, titanium sol particals, and dodecylamine ions, respectively. It was found that neither of ion-exchange reactions between H-type layered manganese oxide and titanyl acetate complex ions or titanium sol particals could occur. Dodecylamine ions were able to be intercalated into the interlayer of H-type layered manganese oxide by an ion-exchange mechanism, forming a swelled layered manganese oxide. When the swelled layered manganese oxide was reacted with titanyl acylate complex ions or titanium sol particles, respectively, two new layered manganese oxides were obtained. H-Birnessite layered manganese oxide reappeared when dodecylamine-swelled layered manganese oxide was reacted with titanyl acylate complex ions, while a new layered manganese oxide phase was found during the reaction between dodecylamine intercalated manganese oxide and titanium sol, which had a weak crystallinity. On the other hand, when swelled layered manganese oxide was stirred with a mixed solution of titanium propoxide and ethanol, followed by a solvethermal treatment at 50 ℃ for 48 h, titanate pillared manganese oxide was synthesized. A TiO₂ pillared microporous manganese oxide was obtained by heating the titanate pillared manganese oxide in the air at 300 ℃ for 2 h, which still maintained a layered structure and had a basal spacing of 0.95 nm as well as a BET areaof 140 m2/g. The effect of different concentrations of titanium propoxide solution on the TiC>2-pillared microporous materials was examined. The obtained materials at different stages were characterized by XRD, DSC-TGA, SEM, TEM, IR, N2 adsorption-desorption and element analysis.The effects of reaction conditions on the finial materials were systematically discussed in Chapter 3. Alkylamine swelled products with different basal spacing were obtained by reacting the H-birnessite with decylamine, octylamine, and dodecylamine, respectively. The results indicated that the basal spacing of the alkylamine intercalated products connected with the chain length of intercalated alkylamine. The different alkylamine intercalated manganese oxides were dispersed into the pure titanium propoxide, and then the suspensions were solvethermally treated at the same temperature. The obtained products had nearly the same basal spacing, which was not connected with the length of alkylamine. In addition, the effect of solvethermal temperature on crystallinity and thermal stability of the obtained materials were also described. The results showed that all obtained products had a layered structure, but the basal spacing increased with the increase of the solvethermal temperature. The layered structure of the obtained titanium pillared layered manganese oxide could be stabilized to 300 °C and was destroyed above this temperature. It was found that the basal spacing, quantum of intercalated titanium, and thermal stabilization of the finial products were related to the content of H2O existing in the interlayer of alkylamine swelled layered manganese oxide. Titanium pillared microporous manganese oxide was synthesized successfully on the basis of influencing factors.