Synthesis, characterization and influence parameters on the overgrowth of micro/mesoporous Y-zeolite-MCM-41 composite material under acidic conditions

Y-zeolite-MCM-41 composite material with microphase zeolite Y as core and mesophase MCM-41 as shell was simply synthesized by overgrowing MCM-41 on zeolite Y at acidic medium containing cationic surfactant and inorganic Si source. The material was characterized by various techniques. The results indicated this material had hierarchical micropore and bimodal mesopore as well as large BET surface area and thick mesopore wall. Furthermore, the closely connected micropores and mesopores in a single dimension were clearly observed. The effects of various synthesis parameters on the formation of Y-zeolite-MCM-41 composite material were discussed in detail. The steric hindrance effect of counter ion Cl- of the S+X-I+ route at acidic medium, the speed of Si condensation, the induction time (t(p))of silica precipitation, the local effective surfactant packing parameter theory and the charge balance theory were applied to explain the reasons why various parameters could affect or not the product structure. The feasible synthesis conditions were obtained, for adjusting the framework Si/Al of the microphase and improving the mesophase structure such as pore size, orderliness and wall thickness. Finally, mesoporous Al-MCM-41 containing zeolite Y secondary building units in its wall was also synthesized under the strong acid condition (pH = 0) by the designed method in this paper. (C) 2010 Elsevier Inc. All rights reserved.