Core-shell structured zeolite-zeolite composites comprising Y zeolite cores and nano-β zeolite shells: Synthesis and application in hydrocracking of VGO oil

Zeolite-zeolite composites composed of Y zeolite cores and polycrystalline beta zeolite shells were prepared, in which Y zeolite was overgrown with a thin layer of nano-beta zeolite. The incompatibility of the cores and the shells with different zeolite structure types, chemical compositions and crystallization conditions was circumvented by using Y zeolite as the nutrients for the growth of beta zeolite crystals since the dissolution of the core zeolites was inevitable during the formation of the shell layers. The structural, crystalline, and textural properties of the as-synthesized samples were characterized by XRD, SEM, TEM, EDS, SAED, N-2 adsorption-desorption, FT-IR, in situ IR spectra of pyridine and di-tert-butyl pyridine. The performances of the as-synthesized zeolite-zeolite composite supported by Ni-Mo active components were investigated during the hydrocracking of Iran VGO oil. The results displayed that the core-shell structured composites with a high-silicon beta zeolite shell displayed a better performance in terms of conversion of VGO oil and yield of jet fuel, middle distillate yields and middle distillate selectivity than the reference catalyst and the composite catalyst with a low-silicon beta zeolite shell. (C) 2014 Elsevier B.V. All rights reserved.