Co–ZSM-5 catalysts with different Co-loadings (2–30 wt.%) were prepared by incipient wetness impregnation method. The prepared solid
catalysts were characterized by X-ray diffraction, FTIR, in situ FTIR of pyridine adsorption and surface area measurements. The XRD data
presented disintegration in the zeolitic crystalline structure accompanied by an increase in particle size of the prepared solids. New phases, Co3O4
and Co2SiO4, were detected with increasing the Co-loading, which indicate the strong interaction of cobalt ions with the ZSM-5 zeolite. FTIR
study proved the presence of Co ions in stabilized sites inside the ZSM-5 framework. The in situ FTIR of adsorbed pyridine determined the type
and relative strength of acidity on the surface of the prepared solids. The acidity switched from B-acid sites to L-acid sites with impregnation of
cobalt ions in ZSM-5 zeolite. The acidity decreased with increasing Co-loading, which might be due to the destruction of zeolite framework and
presence of new phases such as cobalt silicate and cobalt oxide on the surface. The surface texture characteristics changed with the promotion of
ZSM-5 by cobalt ions, since a decrease of surface area, mean pore radius and pore volume was observed.
The assessment of the catalytic activity was performed by the use of the photo-degradation of acid green (AG) dye as a probe reaction in presence
of H2O2 as an oxidant. The pH value controlled the degradation rate since a gradual increase of AG degradation rate was observed with increasing
pH value and the optimum H2O2 concentration was 61.6 mmol/l. It was found that, the AG degradation rate increased until an optimum value of
Co-loading (ca. 10 wt.%), beyond which a monotonic decrease of reaction rate was recognized. The experimental data pointed to the importance
of both the cobalt moieties and the zeolite framework structure in the AG degradation reaction.
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