Role of crystal growth modifiers in the synthesis of ZSM-12 zeolite

• The effect of the growth modifiers/Si ratio on the phase purity was studied.
• Polyethylene glycol and polyoxyethylene Brij-35 were used as a growth modifier.
• Growth modifiers suppressed co-crystallization phase.
• Rapid synthesis time of 60 h was achieved in the presence of modifiers.

The effects of crystallization time, temperature and aging time on the synthesis of pure ZSM-12 in the presence of polyethylene glycol (PEG) and polyoxyethylene Brij-35 surfactant with fixed ratios of Si/Al (160) and Na/SiO2 (0.144) were systematically investigated. Larger synthesis window and high purity of ZSM-12 were expected. Pure phase of ZSM-12 was obtained when PEG was added to the synthesis mixture with PEG/Al2O3 ratio in the range of 0.4–2. Furthermore, the addition of both Brij-35 and PEG in the synthesis was found to play a significant role in controlling the crystallization rate. The Brij-35/Al2O3 ratio was varied from 0 to 4.9. Conventional ZSM-12 was typically synthesized at 145 °C for 120 h. Shorter crystallization time of 60 h was achieved when PEG/Al2O3 ratio of 1.22 and a Brij-35/Al2O3 ratio of 1.61 was used in the synthesis.

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