Synthesis And Characterization Of Microsized Zeolite NaY With High Silica-Alumina Ratio

Microsized zeolite NaY has a wonderful prospect in the way of catalysis,gasoline desulfurization, water treatment and bioresearch owing to its uniquefeatures. But the thermal stability and hydrothermal stability of zeolite NaYare worse because the crystal size is smaller. However, stability of zeoliteNaY can be enhanced via raising the framework silica-alumina ratio. The goalcan be achieved by increasing framework silica-alumina ratio when the crystalsize remains unchanged.To discover the synthesis method of microsized zeolite NaY with highsilica-alumina ratio, which can be industrialized easily, the gelling way ofaluminosilicate gel, mole ratio of nucleation gel, sodium-aluminum ratio ofsynthesis system are selected, setting industrial zeolite NaY as reference. Onthat basis, more emphasis are put on the optimization of the nucleation gelaging, aluminosilicate gel aging and crystallizing, then microsized zeolite NaYwith high silica-alumina ratio is synthesized.Zeolite NaY is characterized by XRD, SEM, DLS, BET and so on. Itshows that the highly active nucleation gel is synthesized by adding sodium aluminate to water glass with strirring at temperature, then the microsizedZeolite NaY is synthesized, whose average crystal size is less than200nanometer. The nucleation gel aging time and way affect agglomerationdegree and quantity of crystal nucleus precursor and then impact crystal sizeand crystallization rate of zeolite NaY. The crystallization rate is higher andagglomeration degree of zeolite NaY is lower, when the nucleation gel agesdynamically at temperature for24-36hours.The crystallization rate is accelerated and the particle size is decreased byraising sodium-aluminum ratio of synthesis system; The frameworksilica-alumina ratio can be improved by reducing sodium-aluminum ratio ofsynthesis system; Microsized zeolite NaY can be synthesized, whose averagecrystal size is between142and174nanometer and the frameworksilica-alumina ratio is above5.0, when the sodium-aluminum ratio ofsynthesis system is between3.2and3.3. The crystallization temperatureadvanced can make the crystallization rate quick and the particle size small.Thus, the crystallization temperature is fit for90℃. What′s more, decreasingaluminosilicate gel aging temperature and shortening crystallization timeresult in reduction of crystal size of zeolite NaY.In a word, through optimizing synthesis conditions, microsized zeoliteNaY with high silica-alumina ratio is synthesized, whose frameworksilica-alumina ratio is5.29and average crystal size is77nanometer.