Zeolite synthesis in the presence of flexible diquaternary alkylammonium ions (C2H5)(3)N+(CH2)(n)N+(C2H5)(3) with n=3-10 as structure-directing agents

Abstract

The use of flexible diquaternary alkylammonium ions (C(2)H(5))(3)N(+)(CH(2))(n)N(+)(C(2)H(5))(3) (Et(6)-diquat-n with n = 3-10) as structure-directing agents for zeolite synthesis in the presence of alkali metal cation is described. Among the organic structure-directing agents studied here, a considerable diversity in the phase selectivity was observed only for the Et(6)-diquat-5 ion: this cation can produce five different zeolite structures (i.e., P1, SSZ-16, SUZ-4, ZSM-57, and mordenite), depending on the oxide composition of synthesis mixtures. Analysis of the variable-temperature (1)H CRAMPS NMR spectra obtained from the Et(6)-diquat-5 molecules in these five zeolites reveals that the host-guest interactions occurring within the respective materials maintain in a manner different from one another even at 160 degreesC at which the zeolite hosts crystallize. (C) 2003 Elsevier Science Inc. All rights reserved.