Boron Incorporation by Hydrothermal Synthesis Into SAPO-5 and SAPO-11 Molecular Sieves

Abstract

Silicoaluminophosphates SAPO-5 and SAPO-11 were synthesized using the hydrothermal method, 170 ºC with triethylamine and dipropylamine as the structure directing agents, respectively. This work aimed the incorporation of boron into the structures obtained by modifying the composition of the system, using as a reaction equation: Al₂O₃:P₂O₅:x SiO₂: yB₂O₃:1,5TEA (or DPA):50H₂O, with x, y=0-0.2. The phase was identified by XRD and characterized by FTIR, TGA/DTG, TPD-NH₃ and nitrogen adsorption at -196°C. The structure parameters confirmed the obtaining of pure structures, showing a slight contraction in the parameters of the unit cells, indicating the presence of boron in the crystal lattice. The Brønsted sites, were modified up to a maximum of boron (y = 0.1) and for higher content, the acidity was not significant. The modification of weak acidity related to the appearance of isolated BO₃ groups, indicating that the silicon atoms were not sufficiently distributed for the formation of sites.

Keywords:
Boron; SAPO; AFI; AEL