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Synthesis of Large ZSM-5 Crystals under High Pressure

Published online by Cambridge University Press:  18 March 2011

Allan J. Jacobson
Affiliation:
Department of Chemistry and Materials Research Science and Engineering Center, University of Houston, Houston, Texas 77204-5641
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Abstract

The synthesis temperature for silicalite-I (MFI) can be raised to 300°C by applying high pressure to stabilize the structure-directing organic template. The elevated temperature and pressure favor theformation of crystals with improved quality. Prismatic silicalite-I crystals with a uniform size of about 0.7× 0.2 × 0.2 mm have been obtained by heating a gel prepared from TMA-silicate solution, TPABr andsodium hexafluorosilicate at 250°C under a pressure of 80 MPa. The influence of synthesis conditions on the crystal sizes has been studied by systematically changing temperature, pressure and gel compositions. Underthe specific conditions of 250°C and 80 MPa, a strong correlation was found between the crystal size andthe F/Si mole ratio of the starting gel, which enables the preparation of uniform crystals of silicalite-I with preset dimensions.

Type
Research Article
Copyright
Copyright © Materials Research Society 2000

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References

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