High-silica molecular sieve syntheses using the sparteine related compounds as structure-directing agents

Three quaternary ammonium compounds are synthesized from sparteine and thei r performances in high-silica molecular sieve syntheses investigated. N(1)- Methyl-alpha-isosparteinium (compound A) is found to form the pure-silica m olecular sieve with the CFI topology that was first synthesized with its di astereomer N(16)-methylsparteinium (B). The crystallization time for the sy nthesis of pure-silica CFI using A as an organic agent is shorter than that with B. The crystal size of the product obtained with A is much smaller th an that recovered when using B. These results indicate that A is a better s tructure-directing agent for the formation of the CFI than B. Molecular mod eling studies suggest that the reason A is a better structure-directing age nt for CFI than B is that A can form a greater number of Van der Waals inte ractions with the silica framework of CFI. The very rigid and bulky compoun d, N(1),N'(16)-endomethylenesparteinium (compound C) does not yield any cry stalline molecular sieves over a range of the reaction conditions. The lack of success with C could be due to its decreased hydrophobicity and hydroth ermal stability compared to A and B. (C) 1999 Elsevier Science B.V. All rig hts reserved.