Mild modification method for the generation of mesoporosity in synthetic and natural mordenite

Abstract

Zeolites are widely used as acid catalysts for the synthesis of fine chemicals in industrial processes. However, in most cases, diffusion limitations in the microporous network of zeolites prevents a good catalytic performance. In this sense, in the course of our research we have modified synthetic and natural mordenite zeolites by mild dealumination/desilication process to obtain mesoporosity. Commercial mordenite (CBV21A Si/Al = 10.5), and natural mordenite from Ethiopia (Si/Al = 6.2) have been treated under mild conditions (pH = 6) in order to maintain high crystallinity in the final zeolites. The impact of this mild treatment (based on ammonium acetate) is remarkable in the synthetic mordenite, creating good degree of mesoporosity while maintaining the bulk Si/Al ratio and crystallinity of the sample. In the case of the natural mordenite, the treatment leads to strong increase in the crystallinity of the sample, although only small mesoporosity is created. All samples were characterized by X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), N₂ adsorption-desorption isotherms and transmission electron microscopy (TEM).

KEY WORDS: Zeolites, Mordenite, Natural mordenite, Modification, Mesoporous zeolites

Bull. Chem. Soc. Ethiop. 2015, 29(1), 95-103

DOI: http://dx.doi.org/10.4314/bcse.v29i1.8