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Accelerated crystallization of zeolites via hydroxyl free radicals

Science  11 Mar 2016:
Vol. 351, Issue 6278, pp. 1188-1191
DOI: 10.1126/science.aaf1559

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Radically faster synthesis

Zeolite synthesis normally proceeds under basic conditions that allow the oxide bridges between aluminum and silicon atoms to break and reform. Feng et al. show that the formation of hydroxyl radicals, either by irradiation with ultraviolet light or with the Fenton reagent, can speed up the formation of the crystallized zeolite by about a factor of 2.

Science, this issue p. 1188

Abstract

In the hydrothermal crystallization of zeolites from basic media, hydroxide ions (OH) catalyze the depolymerization of the aluminosilicate gel by breaking the Si,Al–O–Si,Al bonds and catalyze the polymerization of the aluminosilicate anions around the hydrated cation species by remaking the Si,Al–O–Si,Al bonds. We report that hydroxyl free radicals (•OH) are involved in the zeolite crystallization under hydrothermal conditions. The crystallization processes of zeolites—such as Na–A, Na–X, NaZ–21, and silicalite-1—can be accelerated with hydroxyl free radicals generated by ultraviolet irradiation or Fenton’s reagent.

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