Synthesis, structure and acid characteristics of partially crystalline silicalite-1 based materials

A series of partially crystalline silicalite-1 based materials were synthesized by varying the molar ratio of organosilane source, phenethyltrimethoxysilane (PE) to tetraethylorthosilicate (TEOS) in the range of 0.05–0.50, using one step co-condensation hydrothermal synthesis method. The phenethyl group was subsequently sulfonated to arenesulfonic acid group following strong acid treatment. The resulting materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption and desorption and elemental analysis. The structure of these materials was determined by Fourier transform infrared spectroscopy (FTIR), 29Si and 13C solid state NMR. The % crystallinity of the partially crystalline silicalite-1 as determined from XRD was in the range of 33–73%. The average crystallite size decreased with the increase of PE concentration in the synthesis mixture. The thermogravimetric analysis shows that the structures were thermally stable up to 550 °C after elimination of the structure directing agents (SDAs) by calcination at 420 °C. The acid capacities of these materials ranged from 2.52 to 6.63 mmol H+/g.