Synthesis of sillenite-type compounds from zeolite precursors: XRPD and SEM/EDS analyses

Abstract

The paper analyze the possibility of using LTA zeolite as a precursor for obtaining sillenite phase (Bi(12)MO(20), M=Si, Ti, Ge) by hydrothermal synthesis process. The synthesis procedure involves mixing of zeolite (Na-LTA) water solution with native bismuth in autoclave at 170 degrees C for 7 days. As-prepared sample contains sillenite Bi(12)SiO(20) and nepheline (Na(2)AlO(6)) phases. The structures of sillenite and nepheline phases were determined by XRPD methods, and their quantitative amounts were calculated by Rietveld method. These structures were refined with agreement factors: R(p)=7.21, R(wp)=9.25 and R(bragg)=6.14 for a cubic structure sillenite and R(bragg)=18.6 for nepheline phases. The weight fractions were 36.73% for sillenite and 63.72% for nepheline. The shape, morphology and chemical composition of investigated phase are done by means of scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS).