Hydrothermal synthesis of potassium-type zeolite from coal fly ash and evaluation of its physical properties

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Hydrothermal syntheses of potassium-type zeolite from coal fly ash were carried out under various KOH concentrations and reaction temperatures, and crystal structure and cation exchange capacity (CEC) of the reaction products were investigated. Both acid resistance and heat resistance of the reaction products were considered, as these are important for use as a cation exchanger, a catalyst or an absorbent. When hydrothermal synthesis from coal fly ash is conducted at a reaction temperature of 393K, potassium chabazite (K-CHA) begins to form for 5h of reaction time. K-CHA and K-H zeolite are formed as zeolite species at 393K and 453K, respectively. Both K-CHA and K-H zeolite are synthesized simultaneously at 433K. CEC values of the obtained K-CHA and K-H zeolite are 208meq/100g and 104meq/100g, respectively. The CEC of reaction products decreases with increasing reaction temperature, and this phenomenon dictates the kind of formed zeolite. X-ray diffraction intensities of K-CHA gradually decrease with decreasing pH in the range above pH4. Whereas, in the range below pH 4, this intensity decreases rapidly and the elution amount of Al^<3+> from K-CHA with proton increases remarkably. In the case of heat treatment below 873K, the X-ray diffraction intensity of K-CHA decreases with increasing calcined temperature, but thermal decomposition of K-CHA and production of new crystalline materials do not take place in these treatments. With a heat treatment of 1273K, the K-CHA peaks disappear in the XRD pattern, and those of leucite generate anew.
関西大学の論文
2005-03-21

Hydrothermal synthesis of potassium-type zeolite from coal fly ash and evaluation of its physical properties

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