Chemical Engineering Science, Vol.153, 374-381, 2016
Direct synthesis of hierarchical USY zeolite for retardation of catalyst deactivation
Hierarchically structured zeolite Y was hydrothermally synthesized using a water glass containing organosilane surfactant as a mesoscale template. The resulting hierarchical zeolite Y was characterized by a complementary combination of X-ray powder diffraction, Fourier transform infrared spectroscopy, N-2 adsorption-desorption isotherms, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, Al-27 MAS NMR spectroscopy and density functional theory (DFT) calculation. These results indicated that the hierarchical zeolite Y contained disordered intracrystal mesopores. In addition, quantum chemical calculation results showed that organosilane surfactants could be easily dispersed into the viscous gel used in the synthesis of zeolite Y, inhibiting the phase-separation phenomenon. Hierarchical zeolite Y exhibited remarkably higher resistance to deactivation in the aldol condensation reaction of benzaldehyde with n-butyl alcohol than that of commercial zeolite Y, which is attributed to the highly mesoporous structure that can improve access of reactant molecules to the active sites and minimize the diffusion length of coke precursors out of the zeolite matrix. Such hierarchically porous zeolite Y is very attractive for applications in adsorption and catalysis involving bulky molecules. (C) 2016 Elsevier Ltd. All rights reserved.