Organic Additives Templates in Synthesis of Zeolites and Molecular Sieves

Organic Additives (Templates) in Synthesis of Zeolites and Molecular Sieves 

Tetramethylaimnonium (TMA) cation was investigated as an additive in the synthesis of type A zeolite (LTA or Linde Type A) in 1961 (Barrer and Denny, 1961 Kerr and Kokotailo, 1961). Many new crystalline phases were found by the addition of TMA. It was soon found that the Si/Al ratio in LTA could be increased up to 2.5 by the use of TMA. An analog of these crystals is named ZK-4 (Kerr, 1966). The size of the TMA cation is approximately 6 A, which is about the same size as that of hydrated Na . These cations fit well in the beta or sodalite cage. A typical composition of ZK-4 is Na8(TMA)i.2[(A102)9.2(Si02)i4.8] 28H2O. 

Chamell used triethanolamine (2,2, 2 -nitrilotriethanol) as an additive in the synthesis of zeolites A and X and reported that crystals as large as 100 and 140 xm, for zeolites A and X, respectively, were formed (Chamell, 1971). Subsequent work showed that triethanolamine formed a complex with Al +, the presence of which would reduce the tendency for nucleation and crystal growth (Coker and Jansen, 1998). 

Adsorption, diffusion, and reaction in ZSM-5 and siUcaUte have been studied extensively. For adsorption, it has been used as a selective sorbent for VOC 

The syntheses of aluminophosphate (AIPO4) molecular sieves were first reported in 1982 (Wilson et al, 1982a 1982b and 1984). These molecular sieves have a very narrow range of chemical composition (i.e., rather invariant ratio of P/Al compared with the wide range of Si/Al ratio in zeolites), but exhibit a rich diversity of framework structures. The chemical composition of AIPO4 is 

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