Incorporation of niobium in SAPO-11 materials: Synthesis and characterization

The present work concerns a new synthesis approach to prepare niobium based SAPO materials with AEL structure and the characterization of Nb species incorporated within the inorganic matrixes. The SAPO-11 materials were synthesized with or without the help of a small amine, methylamine (MA) as co-template, while Nb was added directly during the preparation of the initial gel. Structural, textural and acidic properties of the different supports were evaluated by XRD, TPR, UV–Vis spectroscopy, pyridine adsorption followed by IR spectroscopy and thermal analyses. Pure and well crystalline Nb based SAPO-11 materials were obtained, either with or without MA, using in the initial gel a low Si content of about 0.6. Increasing the Si content of the gel up to 0.9 led to an important decrease of the samples crystallinity. Niobium was found to incorporate the AEL pores support as small Nb2O5 oxide particles and also as extra framework cationic species (Nb5+), compensating the negative charges from the matrix and generating new Lewis acid sites.

Effect of the niobium addition on the morphology of the SAPO-11 materials synthesized.Figure optionsDownload as PowerPoint slideHighlights
► Highly crystalline niobium based SAPO-11 materials.
► Isolated niobium species in exchange positions.
► Nb2O5 oxide present as small particles.
► Presence of Lewis acid sites derived from niobium species.