On the autothermal synthesis of zeolites

• Zeolite synthesis is demonstrated using the heat of hydrolysis reaction of Al as only energy source.
• Zeolites LTA, LTN, SOD and CAN are obtained already after 4 h under those autothermal conditions.
• Tailoring of crystal size, morphology and structure type of aluminosilicate zeolites is thereby simply possible.
• The autothermal process is a suitable preparation method under less energy and time consuming conditions.

The present investigation is a case study of zeolite formation without external heating. The energy of the exothermic reaction of aluminum in aqueous NaOH solution was utilized as the thermal energy source of the whole crystallization process. Zeolites of structure types LTA, LTN, SOD and CAN were observed under insertion of aluminum, NaOH and sodium silicate as well as NaNO3 in the case of CAN.All products were obtained already after 4 h reaction time in a thermos beaker. The samples were only dried under open air over night to prevent any effect of a drying procedure at elevated temperature in a cabinet dryer.Analyses results according to XRD, SEM and FTIR were presented and discussed.Further modifications like insertion of aluminum waste material and the collection of the byproduct hydrogen are important upgrades in future to develop a cost effective technique on the basis of the proposed autothermal reaction with Al.

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