Synthesis Of Heteropoly Acid-based Composite Catalyst With Controllable Pore Morphologies And Their Catalytic Performance

Heteropoly acid (HPA) have attracted significant attention because of their special properties. However, HPA exhibit low surface area(< 10 m2 g?1), low thermal stability, high solubility in polarity solvent which limit their utility in many catalytic reactions. Thus, the dispersion of HPAs on mesoporous supports with high surface area, large pore diameter, and high specific pore volume is seen as a critical means of improving their properties and obtaining better performance in many potential heterogeneous catalytic applications.1. Periodic mesoporous H3PW12O40/SiO2 composite catalysts with controllable H3PW12O40 loadings (4.0?65.1%) were prepared by a direct sol-gel co-condensation technique in the presence of triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) copolymer followed by hydrothermal treatment. Powder X-ray diffraction patterns and nitrogen sorption analysis indicate the formation of ordered mesoporous materials. With H3PW12O40 loadings lower than 20%, the materials exhibit higher BET surface area (604.5?753.0 m2 g?1), larger pore size (6.1?8.6 nm), larger pore volume (0.75?1.2 cm3 g?1), and highly dispersed Keggin unit throughout the materials. Raman scattering spectroscopy studies confirm that the primary Keggin structure remained intact after formation of the composites. The acid catalytic properties of as-prepared materials was tested by the reaction of solvent-free synthesis of diphenolic acid from levulinic acid. Remarkably high catalytic activity and stability were observed.2. A series of mesostructured H3PW12O40/SiO2 materials were developed by using a single step co-condensation technique in the presence of nonionic oligomeric surfactant, C18H37(OCH2CH2)10OH (C18EO10, Brij76). By tuning the composition ratios of the starting precursors (mainly the molar ratios of water to the other materials) and the preparation conditions, the materials exhibited ordered two-dimensional (2D) hexagonal p6mm, three-dimensional (3D) hexagonal P63/mmc, and 3D disordered sponge-like pore geometries, respectively. The materials possessed unique textural properties including very large BET surface area (590?1050 m2 g?1), very high porosity (0.4?1.3 cm3 g?1), and well-distributed pore diameter (3.0?5.4 nm). As a novel type of reusable solid acid catalyst, as-prepared materials were applied for the synthesis of diphenolic acid (DPA) from biomass-derived platform molecule, levulinic acid (LA), under solvent-free condition, and special attention was paid to investigate the influences of the structural orderings, pore geometries, H3PW12O40 loadings, and template removal methods on the reactivity and selectivity of H3PW12O40/SiO2 materials to the target reaction.3. A series of mesostructured H3PW12O40/TiO2 materials with two-dimensional hexagonal p6mm, three-dimensional cubic Im3m, and three-dimensional interconnected sponge-like pore geometries were developed by using a single step nonionic-surfactant-templating strategy combined with evaporation-induced self-assembly (EISA) or hydrothermal treatment technique. The mesostructure, morphology, porosity, optical absorption property as well as composition and structure of as-prepared materials were well-characterized. Subsequently, the materials were successfully applied to the degradation of an aqueous phthalate ester (a kind of endocrine disrupting chemicals) under the simulated sunlight irradiation (? > 320 nm and ? > 400 nm), and special attention was paid to investigate the influences of the structural orderings, pore geometries, H3PW12O40 loadings as well as calcination temperature on the photocatalytic performance of the H3PW12O40/TiO2 materials to the target reaction.