Synthesis of Materials Containing Ferrierite Layers Using Quinuclidine and 1-Benzyl-1-methylpyrrolidine as Structure-Directing Agents. An Experimental and Computational Study

A successful synthesis strategy consisting in the combination of two structure-directing agents of different size, quinuclidine and 1-benzyl-1-methylpyrrolidinium (bmp), has been applied to produce zeolitic materials from alkali-free gels in fluoride medium. Two temperatures (150 and 135 °C) were initially tried, as this small difference of 15 °C is crucial for obtaining different types of zeolitic phases for the same gel composition. Synthesis at 135 °C rendered a crystalline material formed by the stacking of ferrierite layers along the direction perpendicular to the sheet. This layered product is different from others ferrierite-related layered precursors, like PREFER, MCM-47, and MCM-65. Computational studies show that the quinuclidine molecule is preferentially accommodated inside the [5⁸6⁶8²] ferrierite cages, which are formed as a consequence of the condensation of the sheets, while the bulkier bmp is located in the 10-membered-ring zeolite channels. Computational results suggest that quinuclidine is too bulky to be accommodated inside the cages of hypothetical full-sheet connected three-dimensional ferrierite crystals and therefore yields a material with a higher interlayer separation.