Synthesis of A-type zeolite membrane using a plate heater and its formation mechanism

The synthesis of zeolite membrane using a plate heater is described. Attempts have been made to synthesize zeolite membrane either by the static method, which is a typical zeolite synthesis method, or by the circulated solution system. In both methods, the zeolite membrane was selectively formed on the substrate that was heated with a plate heater. Liquid phase solution, which was separated from the hydrogel, was found to be suitable as the starting material. In the case of the static method, A-type zeolite was mainly formed as the membrane. However, by-products such as gmelinite, chabazite and faujasite were detected with increasing crystallization period, which might be due to the shortage of secondary building units with the progress of zeolite formation. In the case of the circulated solution system, using an excess amount of the liquid phase solution, zeolite membrane crystals were formed consisting of only A-type zeolite, spherical in shape. The formation mechanism of A-type membrane is discussed according to observations by means of scanning electron microscope and X-ray diffraction analyses. (C) 2000 Elsevier Science B.V. All rights reserved.