Synthesis strategies to improve the catalytic activity of the new Ti(III)APO-5 materials in oxidation reactions
| Autor: | Alfayate Lanza, Almudena, Sepúlveda-San José, R., Sánchez Sánchez, Manuel, Pérez Pariente, Joaquín |
|---|---|
| Rok vydání: | 2014 |
| Zdroj: | Digital.CSIC. Repositorio Institucional del CSIC instname |
| Popis: | Trabajo presentado en la 6th FEZA Conference, celebrada en Leipzig (Alemania) del 08 al 11 de septiembre de 2014. Ti-containing zeolites have received much attention due to their high catalytic activity in oxidation processes of industrial interest [1]. However, attempts carried out with the related Ti-doped AlPO4-based materials have not resulted in such successful catalysts. For that reason, we have developed a synthesis method to obtain TAPO materials containing more active Ti centres [2]. By introduction of Ti(III) ions in the synthesis gels, instead of the traditionally used Ti(IV), a different incorporation mechanism is likely to happen with a consequent change in their coordination environment. The introduction of Ti as Ti(III) in the AlPO-5 structure has resulted in more active catalysts in the cyclohexene oxidation with H2O2 than the conventional TAPO-5 material, prepared with Ti(IV) [3, 4]. Additional strategies can be applied to the synthesis of these Ti(III)APO-5 materials to further improve their catalytic activities. The acidification of the gel pH by addition of HCl in the synthesis gel would stabilize the Ti(III) ions and favour their incorporation in that oxidation state, and the addition of Si would lead to a more zeolitic environment of the Ti(III) ions. From Fig. 1, it can be inferred that gels with more acidic pH do not result in a more active material than the Ti(III)APO-5 synthesized under unmodified conditions. However, the activities per Ti centre (TON) become higher for the catalysts obtained by the addition of Si to both an aqueous gel and a biphasic (water-hexanol) gel, likely because of the generation of a more siliceous environment of Ti, similarly to zeolites. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|