Synthesis method for introducing mesoporosity in a faujasitic-like zeolite system from a sodium aluminosilicate gel composition

Abstract

We report a facile synthesis method of hierarchical faujasitic structures from a sodium aluminosilicate composition. The critical experimental variable was the removal of water via heat from the aluminosilicate gel during the synthesis process. These gels were used as starting materials for synthesis. With these partially dehydrated gels, extensive zeolite nucleation did occur, and the extent was varied both with the degree of dehydration and the temperature at which the dehydrated sample was maintained. Nanoparticles of FAU and EMT were formed that pack together resulting in external surface areas of 249–259 m2/g. In addition, under certain conditions of crystal growth, sheet like-structures arising from FAU-EMT intergrowths were observed. The interpenetration packing of the nanosheets lead to zeolitic particles with external surface areas in the range of 127–199 m2/g. The pore size distribution varied with sample preparation and ranged from 2 to 100 nm. These samples were characterized by N2 adsorption, X-ray diffraction and electron microscopy. The thermal and hydrothermal stability was also studied. In order to evaluate the role of the higher external surface area on a chemical reaction, the dealkylation of 1,3,5-triisopropylbenzene was examined and the product distribution did reflect the mesoporous nature of the sample.