Synthesis of Al-rich ZSM-12 using TEAOH as template

Hydrothermal synthesis of ZSM-12 (MTW) with tetraethylammonium hydroxide (T EAOH) as template was systematically studied with the objective of obtainin g an aluminum rich zeolite. In contrast to other zeolites, published inform ation on the synthesis of ZSM-12, especially aluminum rich samples, is limi ted since its preparation is a difficult task due to its inherent high sili ca character. The effect of aluminum content of the gel, the OH-/SiO2 ratio and the TEA/SiO2 ratio were examined and the crystallization domain of pur e ZSM-12 phase was identified as a function of these parameters. TEA/SiO2 a nd OH-/SiO2 ratios much lower than what is typically used in zeolite synthe sis were found to be favorable for crystallization of ZSM-12, especially at Si/Al ratios ranging from 30 to 50. In this study, we were able to success fully synthesize ZSM-12 with Si/Al ratio of 31. This was achieved from gels having TEA/SiO2 ratios of 0.125 as well as 0.16 and OH-/SiO2 ratio of 0.07 . The products obtained were characterized by XRD, SEM, BET and TGA. The re sults clearly showed that pure ZSM-12 with high crystallinity was obtained in all the batches. The amount of organic retained in the zeolites after sy nthesis was constant but the state of TEA was very different depending on t he Si/Al ratio of the zeolite. (C) 2001 Elsevier Science B.V. All rights re served.