Hollow Silica-Alumina Composite

Control of Shell Thickness of Hollow Silica-Alumina Composite Spheres and their Activity for Hydrolytic Dehydrogenation of Ammonia Borane... 

Control of shell thickness of hollow silica-alumina composite spheres and their activity for hydrolytic dehydrogenation of ammonia borane... 

Keywords Hollow silica-alumina composite spheres Shell thickness Hydrolytic dehydrogenation Ammonia borane... 

Morphologies of hollow silica-alumina composite spheres before calcination were examined using SEM. From the SEM images, silica and/or alumina agglomerations were observed around the samples prepared using 5 and 10 g of PS suspension. On the other hand, homogeneous samples were... 

Figure 1. TEM images of hollow silica-alumina composite spheres prepared using (a) 5, (b) 10, and (c) 15 g of PS suspension and coating time for (a) 24.0, (b) 7.0, and (c) 1.5 h.

Table 1 Properties of hollow silica-alumina composite spheres...

We have already fabricated hollow silica-alumina composite spheres prepared by sol-gel based method using aqueous ammonia solution as a promoter of sol-gel reaction [4], and have revealed the influence of their nanostructure of the hollow spheres on their catalytic activity for hydrolysis of NH3BH3 [4], In the present study, we fabricated hollow silica-alumina composite spheres using PS template method and investigated their activity for hydrolytic dehydrogenation of ammonia borane. In addition, we firstly fabricated the hollow spheres using L(+)-arginine as the promoter for hydrolysis of tetraethoxysilane (TEOS) [16],... 

Hollow silica-alumina composite spheres were prepared by polystyrene (PS) template method as follows. The monodisperse PS particles were prepared by emulsifier-free emulsion polymerization [11], The content of PS particles with the diameter of ca. 200 - 300 nm could be tailored through the addition of ethyl alcohol. Then, 15.0 g of the PS template suspension and 6.75 mL of aqueous L(+)-arginine (0.2325 g, Kanto Chem. Co.) solution were added into 40 mL of ethyl alcohol, and then, 20 mL of aluminium(IV) iso-propoxide (AIP, 0.0057 g, Aldrich) / ethyl alcohol solution was added into the mixed solution, following the addition of 0.1551 mL of tetraethoxysilane (TEOS, Kanto Chem. Co., > 99.9 %). The sol-gel reaction was carried out at 323 K for 17 h, and as-prepared hollow silica-alumina composite spheres could be directly obtained. After drying in a desiccator overnight, the obtained fine powders were calcined at 873 K at heating rate = 0.5 K min ... 

Figure 2 Hydrogen evolution from aqueous NH3BH3 solution in the presence of hollow silica-alumina composite spheres prepared with (a) L(-l-)-arginine and (b) ammonia, (c) H-BEA zeolite, and (d) spherical silica-alumina composite particles.

Table 1 Characteristics of Hollow silica-alumina Composite Spheres.

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