THE FRAMEWORK TOPOLOGY OF MAGNESIUM ALUMINOPHOSPHATE STRUCTURE TYPE-36

The crystal structure of MAPO-36 was solved and refined by combining information obtained by synchrotron powder, Weissenberg single crystal (of an imperfect crystal), and electron and Guinier-Lenne powder diffraction. The powder pattern was indexed using a monoclinic cell (C2/c) with a = 13.148, b = 21.577, and c = 5.164 angstrom and beta = 91.84-degrees. Powder patterns were calculated for hypothetical models having similar cell parameters and a match was finally achieved for a model related to but topologically different from cancrinite. The aluminophosphate-based molecular sieve structure type 36 is based on the 4.6.12 two-dimensional net (gml) and the double zigzag chain (zz), but unlike cancrinite, it has both radial and tangential chains around the 12-ring. This gives an elliptical channel with staggered annular side pockets. Even though it has smaller channels, these side pockets give it a greater adsorption capacity than that of AIPO-5.