Исследование методами ИК-спектроскопии и спектроскопии диффузного отражения клиноптилолита, модифицированного ионами водорода, палладия(іі) и меди(іі)
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2016
Науковий керівник
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Одеський національний університет імені І. І. Мечникова
Анотація
Методами ИК-спектроскопии и спектроскопии диффузного отражения показано,
что влияние концентрации азотной кислоты (0,25-3М), используемой для кислотно-
термального модифицированния отечественного клиноптилолита, на спектральные характеристики носителя и закрепленных биметалльных палладий-медных комплексов проявляется существенно при СHNO3≥1,0 моль/л.
Методами ІЧ-спектроскопії та спектроскопії дифузного відбиття показано, що вплив концентрації азотної кислоти (0,25-3М), що вкористовується для кислотно-термального модифікування вітчизняного клиноптилоліта, на спектральні характеристики носія та закріплених біметальных купрум-паладієвих комплексів суттєво проявляється при СHNO3≥1,0 моль/л.
Changes appeared in IR and diffuse reflectance UV-vis spectra of clinoptilolite as a result of its modification by boiling in nitric acid solutions (0.25-3 M) and anchoring active components on it were analyzed. As was shown by IR spectroscopy, the increase in acid concentration caused a high-frequency shift of the band attributed to asymmetric stretching vibrations of the Si-O-Al fragment due to the clinoptilolite dealumination. The values of this shift were not changed after active components anchoring on the acid modified clinoptilolite samples. The band of deformation vibrations of OH groups in water molecules (at 1633 cm-1 for natural clinoptilolite) was weakly affected (a slight high-frequency shift) by the acid concentration increase and remained practically unaffected by anchoring palladium and copper ions. However, the effect of Pd(II) and Cu(II) anchoring on IR spectra could be observed through a low-frequency shift of the band characterizing stretching vibration νОН of OH groups in water molecules indicating some disturbance of hydrogen bonds in H2O molecules and a change in their energy. The UV region of diffuse reflectance UV-vis spectra of all anchored catalyst samples showed the appearance of new intense bands at 224-226, 279-284, and 327-334 nm which were absent in the corresponding spectra of the acid modified supports. They were assigned to bimetallic Pd-Cu complexes which attendance is necessary for catalytic low-temperature oxidation of carbon monoxide with air oxygen. It should be noted that a new band appeared at 351-363 nm would be assigned to individual Pd(II) indicating that some portion of palladium(II) ions did not participate in the formation of the catalytically active bimetallic Pd-Cu complexes. The presence of individual palladium(II) was confirmed by the fact that only the bends characteristic of square planar palladium(II) complexes were observed in the palladium(II) absorbing region in the visible part of diffuse reflectance UV-vis spectra. Additionaly, theses spectra also contained the bends corresponding to d-d transition in the bimetallic palladium-copper complexes. As well, a low-intensity band centered at 740-750 nm could be assigned to copper situated in the bimetallic Pd-Cu complexes because the band was shifted towards the low-frequency region as compared with the mononuclear octahedral aqua complex of copper(II).Judging from these diffuse reflectance UV-vis spectral data and the results obtained in our previous works, the optimal conditions for formation of the clinoptilolite anchored Pd-Cu complexes were achieved when clinoptilolite was boiled in 3 M HNO3 for 30 min.
Методами ІЧ-спектроскопії та спектроскопії дифузного відбиття показано, що вплив концентрації азотної кислоти (0,25-3М), що вкористовується для кислотно-термального модифікування вітчизняного клиноптилоліта, на спектральні характеристики носія та закріплених біметальных купрум-паладієвих комплексів суттєво проявляється при СHNO3≥1,0 моль/л.
Changes appeared in IR and diffuse reflectance UV-vis spectra of clinoptilolite as a result of its modification by boiling in nitric acid solutions (0.25-3 M) and anchoring active components on it were analyzed. As was shown by IR spectroscopy, the increase in acid concentration caused a high-frequency shift of the band attributed to asymmetric stretching vibrations of the Si-O-Al fragment due to the clinoptilolite dealumination. The values of this shift were not changed after active components anchoring on the acid modified clinoptilolite samples. The band of deformation vibrations of OH groups in water molecules (at 1633 cm-1 for natural clinoptilolite) was weakly affected (a slight high-frequency shift) by the acid concentration increase and remained practically unaffected by anchoring palladium and copper ions. However, the effect of Pd(II) and Cu(II) anchoring on IR spectra could be observed through a low-frequency shift of the band characterizing stretching vibration νОН of OH groups in water molecules indicating some disturbance of hydrogen bonds in H2O molecules and a change in their energy. The UV region of diffuse reflectance UV-vis spectra of all anchored catalyst samples showed the appearance of new intense bands at 224-226, 279-284, and 327-334 nm which were absent in the corresponding spectra of the acid modified supports. They were assigned to bimetallic Pd-Cu complexes which attendance is necessary for catalytic low-temperature oxidation of carbon monoxide with air oxygen. It should be noted that a new band appeared at 351-363 nm would be assigned to individual Pd(II) indicating that some portion of palladium(II) ions did not participate in the formation of the catalytically active bimetallic Pd-Cu complexes. The presence of individual palladium(II) was confirmed by the fact that only the bends characteristic of square planar palladium(II) complexes were observed in the palladium(II) absorbing region in the visible part of diffuse reflectance UV-vis spectra. Additionaly, theses spectra also contained the bends corresponding to d-d transition in the bimetallic palladium-copper complexes. As well, a low-intensity band centered at 740-750 nm could be assigned to copper situated in the bimetallic Pd-Cu complexes because the band was shifted towards the low-frequency region as compared with the mononuclear octahedral aqua complex of copper(II).Judging from these diffuse reflectance UV-vis spectral data and the results obtained in our previous works, the optimal conditions for formation of the clinoptilolite anchored Pd-Cu complexes were achieved when clinoptilolite was boiled in 3 M HNO3 for 30 min.
Опис
Ключові слова
клиноптилолит, кислотное модифицирование, ИК-спектроскопия, спектроскопия диффузного отражения, клиноптилоліт, кислотне модифікування, ІЧ-спектроскопія, спектроскопія дифузного відбиття, clinoptilolite, IR spectroscopy, diffuse reflection, acid modify
Бібліографічний опис
Вісник Одеського національного університету = Odesa National University Herald