Microwave-hydrothermal synthesis and characterization of silico-aluminophosphate molecular sieve: SSZ-51

The crystallization of microporous silico-aluminophosphate SSZ-51 has been investigated under microwave-hydrothermal (M-H) conditions. The crystallization was performed by employing fumed silica, pseudoboehmite, ortho-phosphoric acid as silica, alumina and phosphate precursors, respectively, using 4-dimethyl aminopyridine (4-DMAP) as structure directing agent (Template) at 453 K. The effect of parameters such as template concentration, F− ion concentration and crystallization time on the crystallization of SSZ-51 phase was investigated. The crystallized samples were characterized by means of powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), nitrogen adsorption-desorption measurements at 77 K, 29Si CP/MAS NMR and scanning electron microscopy (SEM). The obtained results clearly demonstrated the role of Template/F− ion concentration in the initial gel and crystallization time are critical to obtain pure silico-aluminophosphate SSZ-51 framework under M-H conditions.