Incorporation of boron into nano-size MFI zeolite structure using a novel microwave-assisted two-stage varying temperatures hydrothermal synthesis

The isomorphous substitution of trivalent boron in MFI zeolite structure by applying a novel microwave-assisted “two-stage varying temperature” hydrothermal synthesis method was investigated in this study. The effects of template concentration in the batch composition, aging/stirring time, Si/B ratio and second stage time and temperature on the size, morphology and zeolite formation yield were of interest. At the first stage, nucleation and maturation of zeolite precursors was carried out at 80 °C for 90 min, whereas, the crystallization was done during the second stage at temperature range of 120–175 °C and crystallization time in the range of 30–60 min. The homogeneity and morphology of particles were specified by SEM and the framework vibration spectra and crystallinity of the samples were recorded by FT-IR and XRD test results. Crystallites size and powder recovery varied from 75 to 410 nm and from 26.9% to 100% (w/w), respectively for 120 and 175 °C. Also, crystallinity of MFI phase reached 100% after 60 min crystallization at 140 °C.