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RESEARCH PRODUCT

Factorial Design in the Ammonia Based Synthesis of Large Uniform MFI, MEL, DOH, and DOH/DDR Type Zeolite Crystals

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This study reports the synthesis of large and uniform crystals of high-silica zeolite materials. Statistic factorial design was applied in order to determine significant parameters for the rapid growth of alkali-free crystals out of ammonia-based synthesis systems. For silicalite-I, high ammonia contents at low water concentrations yielded crystals up to 300 μm in size. The number of crystal nuclei in type MFI synthesis systems was found to be significantly reduced by increasing ammonia and aluminium contents. MEL-type zeolites could be prepared only with the smaller size of 15 μm. Low water concentrations improved the product yield. Aminoadamantane as a guest molecule nucleated highly uniform clathrasil crystals of DOH type with a 200 μm size. Upon addition of aluminium, a significant degree of a polytype DOH/DDR material was obtained with slightly smaller crystals. Aluminium was found to be preferentially incorporated at the outer rim of the crystals, thus causing a compositional elemental zoning.