Synthesis of SAPO-16 molecular sieve in non-aqueous medium by microwave method using Hexamethyleneimine as a template

Abstract

An Aluminophosphate with sequence number Six Teen (AST) type framework silico alumino phosphate (SAPO-16) molecular sieve is successfully synthesized through an eco-friendly, economic and a faster crystallization method by microwave treatment. In the present investigation, SAPO-16 is synthesized in a non-aqueous medium using hexamethyleneimine as a template. The structural and morphological properties are characterized by PXRD, SEM-EDX, TEM, BET, FT-IR, NH3-TPD, and MAS-NMR techniques. Powder X-ray diffraction studies show that the synthesized samples are highly crystalline. EDX results showed that the calcined sample contains 0.7 Al2O3: 0.8 P2O5: 0.4 SiO2 on the surface. TEM analysis inferred that the sample contains 50-100 nm sized particles with uniformed triangle morphology. The TGA analysis reveals that the sample loses about 20% of it's weight from room temperature to 550 °C. BET-adsorption isotherm shows that the surface area is 270 m2/g. Structural integrity is shown by FT-IR analysis and Magic angle spinning Nuclear magnetic resonance spectroscopic analysis. 29Si MAS NMR analysis infers that most of the Si is present in tetrahedral Si:2Al:2Si environment. TPD-NH3 reveals that the presence of maximum amount of strong Brønsted acidity with minor amount of moderate bronsted acidity. The catalytic activity on Benzaldehyde acetalization reaction shows that the reactants have a maximum of 80% conversion in 8 h with maximum turn over a number of 14.5 × 10−2 and turn over the frequency of 4.0 × 10−5.