Intermedia phases in synthesis of AlPO4-5 molecular sieve: A study of XRD, raman scattering and TGA

Abstract

In the world, aluminophosphate molecular sieves have been synthesized successfully; however, the intermediate phases and their evolution during crystallization process have not been studied systematically yet. In this work, the behaviors of the initial gel and the evolution of the intermediate phases during crystallization process of AlPO₄-5 molecular sieve using triethylamine as a template have been investigated. It has been shown that in the amorphous aluminophosphate gel phases, template triethylamine does exist in protonated form; and there appear a significant change, formation of 12-member rings of AlPO₄-5 structure, during the early stage of crystallization of AlPO₄-5. In addition, a proposition to explain the crystallization of AlPO₄-5 is also suggested.