We present an investigation of the structure and properties of MCM-56 and M
CM-22. These materials have been characterized by X-ray diffraction, scanni
ng electron microscopy, transmission electron microscopy and N-2 adsorption
isotherms. DIFFaX was used to simulate pronounced peak broadening in the X
-ray diffraction patterns of MCM-56. Toluene disproportionation is used as
a test reaction to compare the catalytic activity of MCM-22 and MCM-56. We
have found that MCM-56 is made of very thin MWW-type layers. The layers are
typically one unit cell along the c direction (with a few of them having t
wo or three unitcells). These very thin layers of MCM-56 become tightly cur
led upon calcination. The structures thus formed pack very efficiently, and
this phenomenon prevents access of organic molecules like toluene to most
of the 12 MR cups on the crystal exterior. Although MCM-56 is active for th
e disproportionation of toluene, its activity is lower than that of MCM-22.
A calcination procedure that prevents the curling up of the MCM-56 layers
is needed to make MCM-56 a useful catalyst for large organic molecules. (C)
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