engleski

Characterization of metal species in metal modified mordenite

The unique physicochemical properties of the zeolites, such as their controlled acidity, adsorption capacity, ion exchange properties, and thermal stability, as well as uniform channels and cavities crystallographically ordered in size and position, determine their effectiveness in catalytic processes. Mordenite is widely used in catalysis, separation and purification because of its uniform, small pore size and high internal surface area. Despite the microporous structure, there are limitations that decrease the efficiency of the zeolite as catalysts. Such limitations can be avoided by creating mesoporous voids. Another important issue in catalysis efficiency is the number of active sites (i.e. Lewis and Brønsted acid sites). Its number can be increased with a number of hetero T-atoms within the framework by post-synthesis treatment such as ion exchange. Parent material was prepared by the hydrothermal synthesis in Teflon-lined autoclaves as one-pot synthesis and resulted in sodium mordenite zeolite. Mono- and bimetallic systems of Ag, Fe, and Ag–Fe were prepared by the ion exchange method in H-form mordenite. PXRD pattern shows that the structure corresponds to the structure of mordenite. All post-synthesis treatments did not have a significant influence on the crystallinity of the samples. Preliminary results (FE-SEM with EDS) have shown a certain amount of metals incorporated in mordenite and preserved structure after wet impregnation. AAS gives the exact concentration of metals in mordenite structure and was used to confirm impregnation of metals, but can't say anything about metal species. UV–Vis spectroscopy was applied to identify the silver and iron species. Due to the usually specific behavior of the Ag and Fe cations under the light, photostability was confirmed by exposing the samples to the radiation in the wavelength range of 200 to 1000 nm.

zeolite ; mordenite ; Ag, Fe incoropration ; UV-VIS spectroscopy

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