| dc.description.abstract | In the present work possible routes for the introduction of Mo and Re into silica aerogels and aluminophosphate AlPO-5 have been investigated. Parameter studies on the influence of synthesis conditions including metal precursor, metal molar ratio, sol pH, gelation mechanism, and post treatments have been performed on the synthesis of Me-aerogels. Parameter studies on the synthesis of MeAlPO-5 have been performed with varying metal precursor, sol preparation method, sol pH, choice of structural directing agent, and crystallization conditions. Both Mo and Re have been introduced into silica aerogels following the sol-gel route and ambient pressure drying method, in which the metal (Mo or Re) precursor was added during the sol stage before gelation. The as-prepared Mo-aerogels were all amorphous with metal content up to 0.56 wt.%, whereas all as-prepared Re-aerogels contain both amorphous and crystalline phases with metal content up to 6.61 wt.%. Direct introduction of Mo into AlPO-5 by isomorphous substitution obtained phase pure samples with metal content up to 0.12 wt.%. Direct introduction of Re into AlPO-5 produced samples either contain significant amount of extra phases, or with negligible amount of metal content. An indirect method to introduce Re into AlPO-5 through the intermediate GeAlPO-5 has been attempted in the first stage, where GeAlPO-5 was synthesized with the precursor GeO2, yielding Ge content up to 0.84 wt.%. | |
