Boron's Role in Altering Mfi-Type Zeolite

Abstract

All-silica, boron and boron-aluminium substituted MFI-type zeolites were prepared. Different amounts of boron were added to the starting reaction mixtures to investigate their influence on the properties of the obtained zeolites. A comprehensive characterization of the materials was conducted using various techniques: X-ray Diffraction (XRD), nitrogen physisorption, Scanning Electron Microscopy (SEM), infrared (IR), Nuclear Magnetic Resonance (NMR) spectroscopy, thermogravimetric analysis (TGA) as well as microcalorimetry accompanied by ammonia adsorption. The MFI topology and crystallinity is conserved regardless the amount of heteroatoms that occupied different local environments, while the morphology of the crystals, their thermal stability, and their acidity differ considerably. For instance, boron assuming both tetrahedral and trigonal coordination, affect the interactions of the framework with both the organic structure directing agents (OSDA) and ammonia species giving rise to detectable differences in acidity.

Keywords: boron incorporation, MFI zeolite, structure, acidity