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[摘要]：The facile synthesis of mesoporous gamma-alumina is developed through the partial hydrolysis of Al(NO3)(3) aqueous solution with (NH4)(2)CO3 without organic surfactants. In this synthesis, the stable NH4NO3/Al species (AN/Al) hybrid containing Keggin-Al-13 polycations is first prepared, which is the key for the successful formation of mesoporous gamma-alumina. XRD, Al-27 MAS NMR, TEM, and N-2 adsorption and desorption results demonstrate that the as-prepared AN/Al hybrid can be transformed to gamma-alumina by treatment at 200 degrees C and exhibit a wormhole-like mesoporous structure with large surface area up to similar to 450 m(2) g(-1), pore volume of similar to 0.3 cm(3) g(-1) and narrow pore size distribution peaked at similar to 3.9 nm after completely removing NH4NO3 at 300 degrees C. The obtained mesoporous gamma-aluminas have high thermal stabilities up to 900 degrees C and excellent hydrothermal stability. The investigation shows that the synergetic effect of NH4NO3 and Al-13 species promotes crystallization of Al species to gamma-alumina, which may have a unique mechanism distinct from the mesoporous aluminas reported previously. CO2 adsorption measurements indicate that these mesoporous gamma-aluminas have a much higher CO2 adsorption capacity than ordered mesoporous alumina synthesized by the surfactant-templating method and conventional gamma-alumina derived from aluminum oxyhydroxides. We believe that this research should be useful for providing new insights into the transformation of transition alumina phases and for synthesizing mesoporous gamma-alumina with promising properties for various chemical applications. |
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