Static in-situ hydrothermal synthesis of small pore zeolite SSZ-16 (AFX) using heated and pre-aged synthesis mixtures

The conditions of static in-situ hydrothermal synthesis were optimized to prepare crystalline, pure phase and template-free small pore zeolite SSZ-16 (AFX) particles. The type of silica source and prolonged ageing process at an elevated temperature were decisive in obtaining pure phase zeolite SSZ-16 particles under static conditions and conventional heating. Colloidal and fumed silica-based synthesis mixtures were successful in forming the zeolite SSZ-16. The zeolite particle size was reduced from 46 to 5 mu m when the fumed silica was replaced by colloidal silica. Uniform, fine-grained and fully crystalline zeolite SSZ-16 particles were synthesized only from the colloidal silica-based mixtures that were aged at 80 degrees C for 7 days. The elevated temperature of the ageing stage is supposed to promote nucleation of viable nuclei leading to the reduction of the induction period. The two cycle calcination procedure with maximal temperature of 550 degrees C, ensured the removal of template molecules from the bulk phase of zeolite SSZ-16 particles. Carbonaceous residua were observed in zeolite subsurface region and mainly in the core shell morphology of zeolite SSZ-16 particles. The phase purity of zeolite SSZ-16 particles was checked by XRD and sorption properties were determined by N-2 adsorption at -196 degrees C. Zeolite SSZ-16 particles showed the micropore volume of 0.24 cm(3)/g and BET surface area of 496 m(2)/g. (C) 2016 Elsevier Inc. All rights reserved.