Experimental evidence of the ‘‘memory’’ effect of amorphous aluminosilicate gel precursors Tatjana Antoni  c-Jeli  c a , Sanja Bosnar a , Josip Broni  c a , Boris Suboti  c a, * , Mirjana  Skreblin b a Rud - er Bo skovi c Institute, Laboratory for the Synthesis of New Materials, P.O. Box 180, Bijeni cka cesta 54, 10000 Zagreb, Croatia b Pliva, d.d., Quality Assurance, Prilaz Baruna Filipovi ca 25, 10000 Zagreb, Croatia Received 11 March 2003; received in revised form 9 July 2003; accepted 9 July 2003 Abstract The principle of the ‘‘memory’’ effect of amorphous aluminosilicate gel precursors, namely that crystal size distri- bution in the crystalline end product depends exclusively on the number and distribution of nuclei in the gel matrix, previously evidenced theoretically by simulation of zeolite crystallization under various conditions, was evaluated experimentally by analysis of the data obtained from specially designed kinetic experiments of zeolite crystallization. It was found that particulate properties (specific number of crystals, crystal size distribution, size of the largest zeolite crystals) considerably depend on the conditions of gel preparation, and thus on the specific number of nuclei and their distribution in the gel matrix. On the other hand, despite considerable differences in the rates of nucleation and crystal growth during crystallization from appropriate precursor, the particulate properties of the crystalline end products as well as number and distribution of nuclei in the gel matrix are not affected, or are affected very slightly by the crys- tallization condition, and thus by the rates of the relevant critical process (gel dissolution, nucleation, crystal growth). Hence, it was shown that invariability of the size distribution of zeolite crystals in the crystalline end products (zeolite) crystallized from the amorphous aluminosilicate precursors prepared in the same way, but differently treated prior and during crystallization is a consequence of the constancy in the number and distribution of nuclei in the matrix of appropriate gel precursor. This result is in accordance with the result obtained previously by simulation, and thus the principle of the ‘‘memory’’ effect of amorphous aluminosilicate gel precursors was evidenced not only theoretically but also experimentally. Ó 2003 Elsevier Inc. All rights reserved. Keywords: Amorphous gel precursor; Distribution of nuclei; ‘‘Memory’’ effect; Zeolite; Crystallization; Nucleation; Crystal growth; Crystal size distribution 1. Introduction In spite of over four decades of research and progress in zeolite synthesis, techniques and ex- perience, there is still much uncertainty regarding the relevant mechanisms of zeolite nucleation. On * Correspondingauthor.Tel.:+385-1-46-80-123;fax:+385-1- 46-80-098/84. E-mail address: subotic@rudjer.irb.hr (B. Suboti  c). 1387-1811/$ - see front matter Ó 2003 Elsevier Inc. All rights reserved. doi:10.1016/S1387-1811(03)00498-0 www.elsevier.com/locate/micromeso Microporous and Mesoporous Materials 64 (2003) 21–32