Preparation of a New Micro-mesoporous Omega Zeolite by Hydrothermal Route: Effect of Crystallization Time

Nabila Bouchiba,Nadia Toumi,Abdelkader Bengueddach

doi:10.1007/s12633-021-01254-6

Abstract

This work concerns the preparation of a new micro-mesoporous omega zeolite by hydrothermal route. This method consists of the self-assembly of the omega zeolite precursors with a cethyltrimethyl-ammonium bromide surfactant. Different stages of crystallization were studied in order to determine their impact on the textural and structural properties of the resulting materials. For this, several characterization methods were used such as X-ray diffraction, N2 adsorption/desorption, scanning electron microscopy, and Energy-Dispersive X-ray. The results showed that the processing time significantly influences on the crystallinity, porosity and Si/Al ratio of the resulting materials. A specific surface area almost three times greater than the parent zeolite was obtained when using non-hydrothermally treated zeolite precursors. While the precursors prepared hydrothermally for 48 or 72 h essentially lead to the formation of the microporous phase corresponding to the Omega zeolite. These new properties can open new applications of these solids notably in the catalysis for the conversion of bulky molecules and also in the adsorption of organic and inorganic pollutants.

Highlights

Zeolites have been widely used as adsorbents and catalysts in many chemical and petro-chemical processes due to their excellent properties such as higher acidity, hydrothermal stability, and form selectivity [1, 2]
The micro/mesoporous samples were obtained at different processing times of omega zeolite precursors (0h, 48h and 72h) using the assembly of preformed zeolite omega precursors with CTABr surfactant
When the precursor zeolite species was used without a previous crystallization, the XRD pattern for the resulting material (sample C (0h)) indicates that a structurally well ordered hexagonal aluminosilicate was successfully assembled from omega zeolite seeds

Summary

Introduction

Zeolites have been widely used as adsorbents and catalysts in many chemical and petro-chemical processes due to their excellent properties such as higher acidity, hydrothermal stability, and form selectivity [1, 2]. The application of these materials is fairly limited because of the difficult separation of nanosized zeolite crystals from the synthesis medium, the low acidity and hydrothermal stability of mesoporous molecular sieve materials and the need of employing Geranium, as well as the addition of special template in the synthesis of ultra-large-pore zeolite [9, 10]. One of the most successful strategies to overcome the above disadvantages is to prepare micro/mesoporous material. By this way, both advantages of large pore size of mesoporous materials and strong acidity and high hydrothermal stability of zeolites would be combined. Several successful routes for synthesizing composites with excellent catalytic performances have been reported in literatures [11, 12]

Methods

Results

Conclusion