Hydrothermally stable aluminosilicate mesostructures prepared from zeolite ZSM-5

Excerpt

Significant advances have been made recently in improving both the hydrothermal stability and acidity of MCM-41 and SBA-15 mesostructures through the use of protozeolitic aluminosilicate nanoclusters or “zeolite seeds” as framework precursors [1‐8]. These nanoclusters contain the secondary building blocks of the zeolite structures that they nucleate. Since the first demonstration of this approach to stable aluminosilicate mesostructures successfully utilized faujasitic zeolite seeds (FAU) to construct the walls of a hexagonal MCM-41 structure [1], many efforts have been made to assemble hydrothermally stable mesopores that are structurally analogous to MCM-41 and SBA-15 from different zeolite seeds solutions such as zeolite L, Beta and ZSM-5 seeds [2‐8]. All of these mesoporous materials show highly hydrothermal stability and good activity in catalytic conversion of organic compounds, as compared with conventional mesopores such as MCM-41 and SBA-15. However, to the best of our knowledge, researchers are still not able to prepare every type of zeolite seeds at the present time, which means that many types of zeolites haven’t their own seeds. Therefore, it is impossible to synthesize hydrothermally stable mesoporous aluminosilicates containing the five-ring subunits characteristic of zeolites other than those reported previously. We report here a general approach to more acidic and hydrothermally stable mesostructures based on the direct assembly of zeolite precursors which were obtained by the dissolution of preformed zeolite into strongly basic solutions. …