Determination of the ordered distribution of aluminum atoms in a zeolitic framework. Part II

Abstract

The connectivity-configuration matrices method, developed in Part I, is applied to mordenite (Na 8Al 8Si 40O 96) to determine the ordered distribution of Al atoms in its framework. There are, in such a high-siliceous zeolite, hundreds of candidates which well describe an observed 29Si MAS n.m.r. spectrum. By utilizing dependencies of various properties of mordenite on the Al content, only one configuration pattern of Al atoms can be selected from these candidates. The reason is sought for why only one pattern is realized out of hundreds of candidates. For this purpose a new rule is introduced complementing Loewenstein's AlOAl avoidance rule, i.e., that a five-membered ring cannot contain two Al atoms. The new rule directly gives a correct configuration of Al atoms as the unique solution using 29Si MAS n.m.r. spectrum alone. The rule is further applied to ferrierite and others, giving correct values for the maximum amounts of Al atoms contained in them. The limitation of applicability of the new rule is discussed.