Zinc - modified forms of zeolites by wet impregnation method [articol]

Abstract

Zeolites are crystalline aluminosilicates that possess well-defined pore structures and inner cavities. The framework consists of numerous aluminum and silicon atoms positioned within oxygen tetrahedral sites. Zeolites have been found to possess both Lewis and Brönsted acidity. Solid acid-base catalysts play an extremely important economical and ecological role in chemical and petrochemical industry as well as refinery technology. The range of catalytic transformation has grown steadily in the past two decades as experimental modifications of zeolites were explored. In this work, the various zeolites have been prepared by hydrothermal methods, calcined and ion-exchanged with ammonium nitrate to yield H-zeolites. The catalysts investigated are both medium (H-ZSM-5) and large pore (H-Y) zeolites. These zeolites are modified with zinc by wet impregnation method. FTIR spectroscopy and XRD analysis have been applied to characterize zeolite structures. The results obtained indicate that the introduction of zinc into ZSM-5 and Y samples lead to a series of promising catalysts, with high activity and a good selectivity.