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

✍ Scribed by K Tsuji; P Wagner; M.E Davis

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 786 KB
• Volume: 28
• Category: Article
• ISSN: 1387-1811
• DOI: 10.1016/s1387-1811(98)00335-7

✦ Synopsis

Three quaternary ammonium compounds are synthesized from sparteine and their performances in high-silica molecular sieve syntheses investigated. N(1)-Methyl-a-isosparteinium (compound A) is found to form the pure-silica molecular sieve with the CFI topology that was first synthesized with its diastereomer N( 16)-methylsparteinium (B). The crystallization time for the synthesis 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 than that recovered when using B. These results indicate that A is a better structure-directing agent for the formation of the CFI than B. Molecular modeling studies suggest that the reason A is a better structure-directing agent for CFI than B is that A can form a greater number of Van der Waals interactions with the silica framework of CFI. The very rigid and bulky compound, N(1),N∞( 16)-endomethylenesparteinium (compound C ) does not yield any crystalline molecular sieves over a range of the reaction conditions. The lack of success with C could be due to its decreased hydrophobicity and hydrothermal stability compared to A and B.