Synthesis and characterization of kaolin/NaY/MCM-41 composites

A series of kaolin/NaY/MCM-41 composites were synthesized through a two-step crystallization process consisting of in situ crystallization of NaY on kaolin with kaolin as a starting material and the overgrowth of MCM-41 on the surface of kaolin/NaY composites. The composites synthesized were characterized by means of XRD, SEM, NMR, TG. differential thermal analyses (DTA), N(2) adsorption and IR spectra and the results were compared with those of the mechanical mixtures composed of kaolin, NaY and MCM-41. XRD analyses showed that the triple composites obtained in the present investigation possess the typical characteristics of well-ordered mesoporous MCM-41 and NaY zeolite. The results of N(2) adsorption indicated that a stepwise-distributed pore structure exists in the composites. Both NMR and IR spectra suggested that the composite is quite different from the mechanical mixture. The results of DTA indicated that cetyltrimethylammonium bromide attached on the NaY phase gives rise to major interaction among the silanol groups in the mesopore. Compared with the mechanical mixture, the composite has much higher hydrothermal stability and more Bronsted and Lewis acid sites. (C) 2003 Elsevier Inc. All rights reserved.