One-pot synthesis of binderless zeolite A spheres via in situ hydrothermal conversion of silica gel precursors

One-pot synthesis route was explored for preparing binderless zeolite A via an in situ hydrothermal transformation process involving the preformation of silica gel precursors. Synthesis process was optimized and resulting samples were characterized using XRD, Raman spectroscopy, EDS, 29 Si and 27 Al NMR spectroscopy, SEM, HRTEM, and pore structure analyses. Furthermore, the kinetics for the in situ synthesis was investigated and the underlying crystallization mechanism was interpreted. The transformation of silica precursors was accomplished via controlling the synthesis parameters which govern the crystallization through determining the dissolution rate of silica nanoparticles, diffusion of Al species into silica precursors and crystal nuclei growth. Subsequently, Al species could contact and react with released Si species from silica nanoparticles to build the structural units that finally construct the LTA framework through self-organized arrangement. On pure zeolite A phase basis, the synthesized binderless sample exhibits higher specific surface area and n-paraffins adsorption capacity than binder-containing zeolite. © 2018 American Institute of Chemical Engineers AIChE J , 64: 4027–4038, 2018