(600cl) Microwave-Assisted Synthesis of Silico-Alumino-Phosphate SAPO-56

Silicoaluminophosphates (SAPOs), a particular type of small pore zeolites, have received considerable interest because of its applications in separations, catalysis and adsorption. Its unique functional properties are attributed to their chemical and thermal stability, unique shape selectivity, molecular sieving properties, ordered microporous structure, and surface properties. In particular, SAPO-56. a microporous silicoaluminophosphate in which silicon substitutes for some of the aluminum and phosphorus atoms in the structural framework displaying pore diameter of ~0.36 nm, could find potential applications in molecular gas separations. SAPO-56 has been successfully synthesized by few research groups via hydrothermal treatment. Microwave (MW) heating has several advantages over conventional hydrothermal approach, such as fast crystallization, phase selectivity, narrow particle size distribution, abundant nucleation, morphology and size control and rapid and uniform heating.

The main objective of the present work was to synthesize SAPO-56 displaying small crystal size and narrow particle size distribution using MW heating to considerably decrease the synthesis time. Interestingly, a phase co-existance (SAPO-56 and SAPO-34) was observed, at short MW synthesis times.  To the best of our knowledge, this is the first evidence of the preparation of SAPO-56 using MW assisted synthesis.