Intensive mechanical pre-treatment of hydrogel in zeolite synthesis: X zeolite synthesis system case study

Short period intensive mechanical treatment of initial hydrogel using fast planetary mills may induce significant changes on the particle size distribution, morphology and even phase structure of the resulting zeolite powder after the synthesis reaction. For a standard synthesis system that produces zeolite X, the effect of mechanical treatment is investigated based on XRD analysis, nitrogen adsorption isotherm measurement, light scattering and FESEM analysis of the resulting zeolite powder. ATR–FTIR has been used to characterize the freshly pre-treated hydrogels. It is shown that mechanical treatment of the gel induces the production of X/A zeolite crystal mixtures. Hydrogels leading to X zeolite show a strong peak at 3310 cm−1, while for hydrogels leading to zeolite A this peak, if present, is very weak. Accordingly, a novel and easy method has been proposed that allows the production of X/A zeolite powder mixtures with the desired proportion of X zeolite from 0% to 100% just by imparting a short time period intensive mechanical mixing of known intensity to the initial hydrogel. It is shown that if the mechanically treated hydrogel is subjected to further aging, pure X zeolite is obtained.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Effect of hydrogel intense mechanical treatment studied in X zeolite synthesis systems. ► Mechanical treatment without aging may be applied to produce A/X mixtures. ► Mechanical treatment with consequent aging results only in X zeolite. ► Hydrogels leading to X zeolite show a strong peak at 3310 cm−1 (ATR spectroscopy).