THE ROLE OF DIQUATERNARY CATIONS AS DIRECTING AGENTS IN ZEOLITE SYNTHESIS

A systematic study was carried out in which the formation of various z eolitic phases from diquaternary cations was monitored. The chain leng th of the diquats was found to play a key role in the nature of the fi nal products. In a specific composition regime, an ''oscillatory'' pat tern was observed, where, by varying the diquat chain length, the unid imensional 10-ring zeolite ZSM-23 or a 12-ring containing system, i.e. , ZSM-50, NU-87, or ZSM-12, was obtained. Molecular modeling studies l ed to a proposed orientation of the respective diquats in the 12-ring pores/channels of ZSM-50 and NU-87. It is concluded that specific chai n lengths provide an ideal fit for the formation of these ''2-dimensio nal'' pore systems. When the fit is less than ideal, ZSM-23 appears as the default phase under the conditions studied.