Crystallization of phase-pure zeolite NaP from MCM-22-type gel compositions under microwave radiation

Applying microwave heating, crystallization of NaP without by-products could be achieved from synthesis gel compositions typically resulting in MCM-22 formation under thermal heating. Adjusting the alkalinity of Na/SiO2 to 1.17, and the synthesis time to 5 h, zeolite NaP (Na4.5Al4.5Si11.5O32 · 9.9H2O) was the main product (91%) with analcime (9%) as by-phase. Phase-pure zeolite NaP was obtained from a gel composed of 60 Na2O: Al2O3:103SiO2:4500H2O with and without hexamethylenediimine (HMI) template under microwave heating at 140 °C for 3 h. Formation of crystalline MCM-22 was not observed. Characterization methods comprised chemical analysis (ICP-OES), XRD, thermal analysis (TG/DTA), 27Al as well as 29Si MAS NMR spectroscopy, and electron microscopy (SEM).