MCM-22 - A MOLECULAR-SIEVE WITH 2 INDEPENDENT MULTIDIMENSIONAL CHANNEL SYSTEMS

The molecular sieve MCM-22 contains structural features previously uno bserved in this class of materials. Its framework topology, derived fr om high-resolution electron micrographs and refined with synchrotron x -ray diffraction powder data, contains two independent pore systems, b oth of which are accessed through rings composed of ten tetrahedral (T ) atoms (such as Si, Al, and B). One of these pore systems is defined by two-dimensional, sinusoidal channels. The other consists of large s upercages whose inner free diameter, 7.1 angstroms, is defined by 12 T -O species (12-rings) and whose inner height is 18.2 angstroms. These coexisting pore systems may provide opportunities for a wide variety o f catalytic applications in the petrochemical and refining industries. Another structural feature is an unusual-T-O-T-chain that passes thro ugh the center of a modified dodecasil-1H [4(3)5(6)6(3)] cage.