Di- and trioxacyclohexane as structure directing molecules in the synthesis of zeolites omega and ECR-1

Six-membered ring cyclohexane derivatives with 2 oxygen (1,4-dioxane or p-dioxane) and 3 oxygen (1,3,5-trioxane) atoms have been used as organic molecules in the synthesis of zeolites omega (MAZ framework type) and ECR-1 (EON framework type). Both molecules yield zeolite omega at moderate temperatures with a composition and aluminum distribution similar to those obtained with more standard organics such as the tetramethylammonium cation. If the preparation of zeolite omega with p-dioxane was previously known, the use of 1,3,5trioxane had never been reported in the literature. The most interesting feature of 1,3,5-trioxane is that these molecules could be released from the structure at very low temperature, typically 300 ?C below the temperature observed with p-dioxane. When the alkalinity of synthesis gels was decreased, zeolite omega was progressively replaced by ECR-1 in the presence of 1,3,5-trioxane but not in the presence of p-dioxane. The relative proportion of omega and ECR-1 in the different solids has been monitored by X-ray diffraction (XRD) and solid-stare nuclear magnetic resonance (NMR). 23Na NMR of calcined rehydrated solids was found to be particularly adapted to discriminate ECR-1 from zeolites omega in MAZ/EON mixtures with poorly resolved XRD patterns.

Automated summary

Six-membered ring cyclohexane derivatives with 2 oxygen atoms and 3 oxygen atoms have been used in the synthesis of zeolites omega and ECR-1, with the latter, 1,3,5-trioxane, showing the ability to be released at lower temperatures. The alkalinity of synthesis gels affects the formation of zeolite omega and ECR-1, with 1,3,5-trioxane leading to the gradual replacement of zeolite omega by ECR-1. Monitoring the relative proportion of omega and ECR-1 in different solids can be done through X-ray diffraction and solid-state nuclear magnetic resonance techniques.