Three different zeolites (erionite, mordenite and natural clinoptilolite) were used to study influence of zeolite topology on the state of copper during ion-exchange and following reduction in hydrogen flow. This comparative study clearly demonstrates the influence of used zeolite matrices on the process of implantation of copper nanospecies. Starting from the ion-exchange, the alterations in the state of Cu2+ ions start to be evident due to variations of the intensity of charge transfer band. Copper ions start to reduce at specific temperatures depending on the type of zeolite matrix. Copper plasma resonance band change its shape and position for different zeolites. In the case of Cu-CLI samples this band change both the shape and position for different temperature of reduction. These observations permit to suggest that the mechanism of copper ion reduction and agglomeration to form copper nanoparticles noticeably depend on the type of zeolite matrix. This mechanism is more complex for the Cu CLI than for the Cu-MOR and Cu-ERI systems. Copper nanoparticles formed at low temperatures in the case of Cu-CLI samples undergo changes while temperature of reduction grow.
We report measurements in copper mordenites showing that silica-alumina molar ratio (MR) strongly affects conversion efficiency for NO x , and that these catalysts are among the most active available for de-NO x at moderate temperatures. Copper mordenites' rapid deactivation by water has led us to also investigate the effects of adsorbed water on framework and extra-framework ions, mainly using NMR of 27 Al and 1 H. Adsorbed water content has been monitored and controlled in mordenite samples via TGA, as well as by vacuum calcination. Several proton NMR measurements have been performed to aid in the interpretation of spectra, including variable pulse-delay spin echo and 1 H/ 27 Al TRAPDOR. A number of surface characterization techniques have been applied to both H and Cu mordenites.
The objective of this study was to prepare composite materials based on mesoporous silica/carbon, functionalized with acid groups, and also to analyze its application in the adsorption of dyes. These materials were prepared in a simplified unconventional route. The carbon phase was generated by direct carbonization of organic surface-active templates, which are used in the synthesis of meso-ordered silicas. The resulting composite materials were characterized in terms of their structure, texture, chemical composition, and surface chemical reactivity. Data obtained demonstrate uniform and ordered porous structures of approximately 70–200 Å, with a developed surface area of approximately 400–500 m2 g−1 and a large total pore volume of approximately 1.0–1.5 cm3 g−1. The potential of synthesized composite materials functionalized by oxygenated groups as adsorbents of cationic dyes was analyzed, the values of the maximum adsorption capacity between 317 mg g−1 and 245 mg g−1 were obtained. The adsorbing properties of silica/carbon composite materials obtained in an unconventional method using an organic template as the only carbon source were compared with the properties of silica/carbon composite materials manufactured by the conventional method using external precursors of the carbon phase. It has been proved that composite materials synthesized using an unconventional procedure, despite the fact that they have a lower carbon phase content, exhibit adsorption properties that are comparable or superior to materials elaborated in the traditional way, removing up to 85–90% of methylene blue from water contaminated with dye.
This work is devoted to the study of copper ion positions in zeolite matrices. Copper cations were exchanged in mordenite and zeolite X from aqueous solutions of different copper salts varying their concentrations. Electronic state of copper in ion-exchanged samples exchanged and dried at different temperatures was evaluated by XPS spectroscopy. Depending on conditions of exchange treatment copper was found to be distributed between two different accessible sites in zeolites. These copper ions are stabilized as isolated species with well-defined oxygen coordination polyhedra.
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