Tuning Zeolite Phase Selection Through Framework Aluminum Content: Insights from Computational and Experimental Studies

Abstract

Recent progress in computational methods applied to the justification or prediction of zeolite phases under silica and aluminosilicate composition using organic structure directing agents (OSDAs) is reviewed. Using synthesis energy as descriptor of stability, it was found that zeolites become more stable as the aluminum content increases, and that the preferential order of incorporation of anions is [AlO4]− > F− > SiO−/SiOH. The calculated preference of AEI and CHA as aluminosilicate stable phases over a wide range of OSDAs tested is now explained using the new d escriptor called packing energy, which allows to quantify the role of Si/Al ratio and demonstrate its dominant role over van der Waals zeolite-OSDA interactions in order to predict the most stable zeolite phase. Packing energies however, are less accurate than synthesis energies, and in the current implementation can not take into account the roles of defects and fluoride anions and can only be applied for [AlO4]− as compensation of the OSDA charge.