Preparation of high silica chabazite with controllable particle size

• High silica (SiO2/Al2O3 = 100) chabazite crystals with a size of 0.3–4.5 μm were prepared.
• Zeolite gel composition and hydrothermal treatment parameters have been correlated with size and shape of zeolite crystals.
• The controlling crystal size step has been identified as the primary fractal aggregation of the Si/Al/SDA species.

In this work synthesis procedures for controlling particle size distributions of high silica chabazite (Si/Al = 100) zeolites between 0.3 and 4.5 μm is described. The chabzite zeolite crystallization and crystal growth have been monitored using XRD, SEM and DLS. Hydrothermal treatment parameters such as time, temperature and agitation and gel composition parameters such as amounts of water and structure directing agent (SDA) have been correlated with chabazite zeolite crystal size, crystal shape, synthesis yield and crystallinity. From this data a chabazite zeolite formation and crystal growth mechanism based on experimental studies and previous studies has been proposed. It was also found that large aggregates formed in the chabazite zeolite gel before any hydrothermal treatment (1 μm large when using zeolite gel with composition 1Al2O3:100SiO2:60TMAdaOH:3100H2O). The size controlling parameter and size controlling synthesis step of the chabazite zeolite (below 1 μm) has been identified as the primary fractal aggregation of the silicium/aluminium/SDA species.

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