Thermal analysis and EPR study of copper species in mordenites prepared by conventional and microwave-assisted methods

Shelyapina, Marina G.; Zvereva, Irina A.; Yafarova, L. V.; Bogdanov, Dmitrii; Sukharzhevskii, S. M.; Zhukov, Yu. M.; Petranovskii, Vitalii

doi:10.1007/s10973-018-7016-2

Cited by 9 publications

(4 citation statements)

References 33 publications

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“…For CuNa-MOR-6.5-M Y , where the MW treatment possibly led to the creation of [Cu-O-Cu] 2+ species [28], changes in the intensities of diffraction peaks at high copper loading (>60%) reflect that these complex cations occupy new sites and/or, perhaps, their appearance led to a redistribution of Cu 2+ .…”

Section: Discussionmentioning

confidence: 99%

“…Earlier, we analyzed the influence of various factors in the preparation of copper exchange mordenites on the properties of the materials obtained [24,25,26,27,28]. In [27], we reported the results of our comprehensive study of two sets of copper-exchanged samples of mordenites prepared from the sodium form of this zeolite and obtained by two different methods: conventional and MW assisted.…”

Section: Introductionmentioning

confidence: 99%

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Comprehensive Analysis of the Copper Exchange Implemented in Ammonia and Protonated Forms of Mordenite Using Microwave and Conventional Methods

et al. 2019

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This article presents the results of a comprehensive study of copper-exchanged mordenite samples prepared from its ammonia and protonated forms (Si/Al = 10) using two different ion exchange methods: conventional and microwave (MW)-assisted. The protonated H-MOR-10 sample was obtained by calcination of commercial NH4-MOR-10; in this case, a slight degradation of the mordenite framework was observed, but the resulting defects were partially restored after the first ion-exchange procedure of protons for copper ions. The level of copper exchange in the studied materials was found to be limited to 70%. Regardless of the exchange procedure, the replacement of ammonium or proton ions with copper led to a linear increase in the a/b ratio of cell parameters in accordance with an increase in the level of copper exchange, which means that all Cu2+ cations are ion-exchangeable and enter the main mordenite channel. Thermal analysis indicated a correlation between the replacement of various ammonium and hydroxyl groups by copper ions during the exchange treatment and their dehydroxylation energy during thermal decomposition. As a conclusion: MW-assisted treatment proved itself as an efficacious method for the synthesis of copper-exchanged mordenites, which not only significantly reduces preparation time but leads to a systematically higher copper exchange level.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comprehensive Analysis of the Copper Exchange Implemented in Ammonia and Protonated Forms of Mordenite Using Microwave and Conventional Methods

et al. 2019

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“…Differences regarding the formation of CuO-based compounds prepared in the presence of microwaves were also previously mentioned [33].…”

Section: Resultsmentioning

confidence: 67%

Comparative study of the thermal behavior of Sr–Cu–O gels obtained by sol–gel and microwave-assisted sol–gel method

Predoană

Atkinson

Karaj

et al. 2020

J Therm Anal Calorim

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In the literature data, several papers reported the synthesis by various chemical or physical methods of the SrCu 2 O 2 (SCO) having possible applications in thermoelectric or completely electronic devices such as solar cells, liquid crystal displays and touch screen. A great challenge is represented by the formation of the pure SrCu 2 O 2 (SCO), due to the high labiality of the Cu valence, depending on temperature. In the present paper, the thermal behavior of Sr-Cu-O gels obtained by sol-gel (SG) or microwave (MW)-assisted SG methods was studied in order to establish the appropriate thermal conditions for pure nanostructured SrCu 2 O 2 preparation. As reagents, copper and strontium acetylacetonate in alcoholic media were used. The starting solutions were homogenized either by stirring for 2 h at room temperature or were exposed to MW for 5 min at 300 W and a frequency of 2.45 GHz. Both solutions were left to gel at room temperature. The obtained gels were investigated by scanning electron microscopy, Fourier-transform infrared spectroscopy, as well as by thermal analysis combined with evolved gas analysis (TG/DTA-MS) measurements in air, inert and reducing atmospheres. For both type of samples, a stepwise thermal decomposition of the gels was noticed in a large temperature range. In the case of samples obtained by microwave-assisted SG method, a higher number of thermal effects were registered assigned to a higher number of molecular species formed in the sample. The residues obtained by non-isothermal treatment up to 900 °C, of both type of samples, were investigated by X-ray diffraction. The results demonstrate the influence of the MW on the SG synthesis and on the thermal properties of the resulted gels. Based on the obtained results, the required thermal treatment of the gels in order to obtain convenient precursors powders for obtaining pure SrCu 2 O 2 could be proposed.

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“…The second band, centered at 207 nm belongs to a charge-transfer complex due to the interaction of Cu 2+ with oxygen of the zeolite framework and/or ligand water molecules. Such charge transfer band is also typical for other Cu 2+ -exchange zeolites; it is observed in mordenites by XPS and EPR methods [45,46].…”

Section: Uv-vis Diffuse Reflectance Spectroscopymentioning

confidence: 53%

Bimetallic Copper-Silver Systems Supported on Natural Clinoptilolite: Long-Term Changes in Nanospecies Composition and Stability

Rodrı́guez-Iznaga¹,

Petranovskii²,

Chavez-Rivas³

et al. 2022

Preprint

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Long-term changes in nanoparticles of copper-silver bimetallic systems on natural clinoptilolite obtained by ion exchange of Cu2+ and Ag+, and then reduced at different temperatures, have been studied. Even after storage under ambient conditions, XRD and UV-Vis diffuse reflectance spectra indicate the presence of nanospecies of reduced copper and silver. Scanning Electron Microscopy of aged bimetallic samples, reduced at the highest temperature (450oC) and the primary samples for their preparation, also aged, showed the presence of silver nanoparticles with a size of about 100 nm. They are formed in the initial ion-exchanged sample (without reduction) due to the degradation of Ag+ ions. The nanoparticles in the reduced sample are larger; in both samples they are evenly distributed over the surface. The presence of silver affects the stability and the mechanism of decomposition/oxidation of reduced copper nanospecies, and this stability is higher in bimetallic systems. The decomposition pattern of recently reduced species includes the formation of smaller nanoparticles and few-atomic clusters. This can occur, preceding the complete oxidation of Cu to ions. Quasi-colloidal silver, which is present in fresh bimetallic samples reduced at lower temperatures, transforms after aging into Ag8 clusters, which indicates the stability of these nanospecies on natural clinoptilolite.

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Thermal analysis and EPR study of copper species in mordenites prepared by conventional and microwave-assisted methods

Cited by 9 publications

References 33 publications

Comprehensive Analysis of the Copper Exchange Implemented in Ammonia and Protonated Forms of Mordenite Using Microwave and Conventional Methods

Comprehensive Analysis of the Copper Exchange Implemented in Ammonia and Protonated Forms of Mordenite Using Microwave and Conventional Methods

Comparative study of the thermal behavior of Sr–Cu–O gels obtained by sol–gel and microwave-assisted sol–gel method

Bimetallic Copper-Silver Systems Supported on Natural Clinoptilolite: Long-Term Changes in Nanospecies Composition and Stability

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