EFFECT OF VARIOUS INORGANIC CATIONS (LI, NA, K AND CS) AND SILICA SOURCES ON THE SYNTHESIS OF THE SILICA ANALOG OF ZEOLITE NCL-1 (SI-NCL-1)

The role of various inorganic cations such as Li, Na, K and Cs has bee n studied in the hydrothermal synthesis of the silica polymorph of zeo lite NCL-1 (Si-NCL-1). The crystallization time decreases in the order (Cs + Na) > K > Na > (Li + Na) under otherwise identical gel composit ion and crystallization conditions. Further, the synthesis has been st andardized using different silica sources including various fumed sili cas with different surface area and particle size, through optimizing the OH-/Si molar ratio by adding the required amount of alkali hydroxi de in the synthesis gel. Among different silica sources (fumed silicas , tetraethyl orthosilicate, silica sol etc.), fumed silicas with small er particles (similar to 0.007 mu m) like Sigma S-5005, S-5130, and Ca b-O-Sil-M5 were found to be quite effective and preferable for the syn thesis of Si-NCL-1 molecular sieves. These materials were characterize d through XRD, IR, SEM, sorption and surface area measurements.