THERMAL BEHAVIOR OF SYNTHETIC FAUJASITE

Data are presented to show that the thermal stability of synthetic faujasite is dependent on the level of sodium present. A simple relationship has been found between the sodium content of ammonium-exchanged faujasite and the temperature at which breakdown of the zeolite structure occurs. This relationship extends to sodium contents below 0.1%, and demonstrates the existence of a continuum of properties for variously exchanged faujasite samples. Regardless of the degree of sodium removal or the method of exchange employed, X-ray diffraction analysis shows that the faujasite structure is retained to just below the breakdown temperature, that material heated just beyond the breakdown temperature is amorphous, and that material heated further, to beyond the mullitization temperature, contains crystalline mullite. The data obtained support the hypothesis that thermally induced migration of cations is an important part of the mechanism for facilitation of exchange, and for structure degradation as well. © 1969.