Synthesis of Basic Cancrinite in a Butanediol−Water System

Abstract

Cancrinite has been synthesized in a 1,3- or 1,4-butanediol/water mixture at temperatures of 353-493 K and reaction times of 24-168 h. Two main series have been performed. In the first series the silica sources (tetraethoxysilane, Aerosil, and precipitated silica) were combined directly with the alumina sources (aluminum sec-butoxide and aluminum isopropoxide) in the synthesis. In the second series organic gels formed from tetraethoxysilane and aluminum sec-butoxide/aluminum isopropoxide as well as inorganic gels formed from hydrolyzation of tetraethoxysilane with aqueous sodium and aluminum nitrate solution or from combination of sodium metasilicate with sodium aluminate were dried and used for synthesis. The products were characterized by X-ray powder diffraction as well as 29 Si and 27 Al MAS NMR spectroscopy. The results show that the sensitivity to the synthesis temperature, duration, and alkalinity depends mainly on the reactivity potential and solubility of the silica/alumina source used in the synthesis. While the directly applied reactants show the highest sensitivity to synthesis temperature and so forth, the gels show even the best synthesis results and cancrinite is formed in a wide range of synthesis parameters (temperature, duration, and sodium hydroxide concentration). A strong relationship between seeding kinetics, crystallization kinetics, and thermodynamic properties of cancrinite seems to be responsible for that behavior under the mild reaction conditions used here. Cancrinite formation as a kinetically controlled process is preferred if both the alumina and silica source dissolve slowly and steadily in the same proportions.