Synthesis of colloidal silicalite-1 at high temperatures

• Synthesis of colloidal silicalite-1 at high temperatures.
• Colloidal stability can be improved by pretreatment.
• Template decomposition products depend on temperature and pretreatment.

Stable colloidal suspensions of silicalite-1 were prepared by hydrothermal treatment of clear precursor suspensions at high temperatures, 150 and 170 °C. The precursor suspensions were pretreated prior to hydrothermal treatment. Different pretreatment procedures were applied, namely ultrasonic treatment or heating at 45–60 °C, for different periods of time. In all cases, the size of the crystals decreased with increasing the time of pretreatment. The pretreatment procedure was found to influence the behavior of the tetrapropylammonium hydroxide solution used as structure-directing template during hydrothermal treatment. Colloidal stability of pretreated samples was improved compared to samples prepared by direct hydrothermal treatment.

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