CONVENIENT PREPARATION OF CLOSE-PACKED MONOGRAIN LAYERS OF PURE ZEOLITE-A MICROCRYSTALS

A convenient synthesis of pure zeolite A from aluminium and silicon mo lecular precursors by a sol-gel procedure is described. The microcryst als quantitatively obtained are of high chemical quality, very good cr ystallinity and size homogeneity. Modification of the composition of t he starting gel, especially the Si/Al or Si/H2O ratios, results in dif ferent morphologies of the crystals or alteration in the size distribu tion. In addition to the normal synthetic procedure used, an extra pur ification step can be performed between particles of slightly differen t sizes by applying a selective procedure based on the differential sp eed of sedimentation. The so-obtained homodispersed samples were subse quently used for the preparation of high quality close-packed monograi n layers deposited on various substrates.