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Silica-Germania adsorbents

1974; Elsevier BV; Volume: 49; Issue: 3 Linguagem: Inglês

10.1016/0021-9797(74)90378-6

1095-7103

Malcolm J. Low, Michie Shimizu,

Aerogels and thermal insulation

Silica-supported germania adsorbents were prepared by treating silica with GeCl4 vapor, and then causing the GeCln surface layer to react with H2O. Infrared spectroscopic techniques were used to monitor the reactions at various stages. The data suggest the following mechanism: GeCl4 reacts on the silanols and also with siloxane bridges; the initial exposure to H2O at 25°C then causes the hydrolysis of SiCl groups to form SiOH groups as well as partial hydrolysis of the GeCln layer. Degassing at high temperature then causes the partially hydrolyzed GeCln layer to become mobile and rearrange and further react with the surface, eliminating the newly-formed silanols, and causing the formation of partially-chlorided germania patches. Dechlorination and aggregation of these proceeds as hydration-degassing cycles are continued. The adsorbents prepared in this fashion have properties like those of adsorbents prepared by reacting silica with Ge(OCH3)4 and converting the methoxide layer to oxide.