Zeolite structure directing agents based upon bulky pyridinium molecules

Abstract

We report new zeolite frameworks synthesized with bulky pyridinium molecules as structure directing agents (SDAs). Aluminosilicate zeolite EMM-63 is prepared in potassium-containing hydroxide media with N,2,3,5-tetramethypyridinium or its skeletal isomer N,2,4,6-tetramethylpyridinium. Two new zeolites (EMM-64 and EMM-65) are prepared with 1-methyl-6,7-dihydro-5H-cyclopenta[b]pyridin-1-ium. EMM-64 is crystallized in fluoride media with or without aluminum, and EMM-65 is prepared as a borosilicate in hydroxide media. The same SDA molecule can be used to prepare an aluminosilicate with the RTH topology, a framework with large cavities and an 8 × 8 channel system. Within each RTH cavity, two SDA molecules form a dimer that is not pi-stacked but instead packs with each pyridinium ring interacting with the unsaturated C5 ring of the neighboring molecule. These interactions optimize the van der Waals interactions both within the dimer and between the dimer and the zeolite framework. The diffraction data of EMM-64 are indexed in tetragonal space group I4₁22 or I4₃22 with unit cell dimensions a = 13.8 Å and c = 18.0 Å, and the unit cell composition is |C₉NH₁₂F_0.9|₄Si₆₄O₁₂₈. The dense framework structure of EMM-64 possesses a tortuous 3D 8R channel system and is unusual in that the framework is chiral. EMM-64 possesses a 5¹²8⁴ cavity with a flat shape like that of the occluded SDA molecule. The fluoride is sited within the 4²5⁴6² cages of EMM-64.