Precursor-seed-assisted facile synthesis of binder-free MCM-22 zeolite

A series of binder-free MCM-22 zeolite catalysts were synthesized within 60 h using a vapor-phase transport (VPT) method, employing MCM-22 precursors prepared via hydrothermal crystallization as seeds. The synthesized zeolites were systematically investigated by using X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier-transform infrared spectra (FT-IR), 27Al magic angle spinning nuclear magnetic resonance (MAS NMR), N2 adsorption-desorption, temperature-programmed desorption of ammonia (NH3-TPD), and X-ray fluorescence (XRF) techniques. The results demonstrated that the addition of precursor seeds (PS) with crystallization time of 36, 48, 60, and 72 h significantly modified the crystal morphologies and improved pore structures and acidic properties of the final products compared to which was synthesized with conventional calcined seed. Specifically, the binder-free MCM-22, PS of which was crystallized for 48 h, exhibited the largest specific surface area, pore volume, and the highest acid site density, leading to superior activity and selectivity in the alkylation of benzene with benzyl alcohol. Furthermore, XRD, FT-IR, SEM, and thermogravimetric analysis (TGA) of PS provided insights into the possible mechanism for the highly efficient synthesis of binder-free MCM-22 zeolites. This work provided a novel and efficient approach for the synthesis of binder-free MCM-22 zeolites, showing potential applications in catalyst industry.