Synthesis of phosphorus-modified AFX zeolite by the hydrothermal conversion of tetraalkylphosphonium hydroxide-impregnated fau zeolite

Phosphorus-modified AFX zeolite was synthesized by the hydrothermal conversion of FAU zeolite, which was impregnated with tetraethylphosphonium hydroxide (TEPOH). For the optimization of the introduced phosphorus, we investigated the influence of the loaded amount of TEPOH on FAU zeolite and tested the combination of the starting materials, composed of phosphorus-free and TEPOH-impregnated FAU zeolites. The synthesis system, employing the combined starting materials, effectively incorporated phosphorus into AFX zeolite while the TEPOH-impregnated FAU zeolite was not effective as a solo starting material. X-ray diffractometry, N2 adsorption, and elemental analysis were employed to confirm the high purity of the AFX zeolite, obtained from the utilization of combined starting materials. Moreover, 13C and 31P magic angle spinning (MAS) NMR spectroscopy further revealed the modification of phosphorus in which the phosphorus species interacting with the zeolite framework was formed via the decomposition of tetraethylphosphonium (TEP) by calcination. © 2021 The Chemical Society of Japan