Different Zeolite Phases Obtained with the Same Organic Structure Directing Agent in the Presence and Absence of Aluminum: The Directing Role of Aluminum in the Synthesis of Zeolites

Zeolites are a largefamily of crystalline microporous materialswith, mainly, silicate and aluminosilicate composition. Each topologycan only be synthesized in a specific range of aluminum content, Al/(Si+ Al), within the interval [0-0.5], and this interval cannot,in general, be predicted for each structure. Aluminum and organicstructure directing agents (OSDAs), among others, act together inobtaining the zeolite phase under each specific synthesis condition.The present study is an attempt to rationalize the role of aluminumas a structure directing agent in the synthesis of zeolites usingcomputational chemistry and based on the criteria of energetic stabilityusing both force field and periodic DFT methods. A proper selectionof cases in which, using the same OSDA, different zeolite phases areobtained in the presence and absence of aluminum helps to rationalizehow aluminum contributes to the relative stability of the differentcompeting zeolite phases considered.