Anomalous valence changes and specific dinitrogen adsorption features of copper ion exchanged in ZSM-5 zeolite prepared from an aqueous solution of [Cu(NH3)2]+

Kuroda, Yasushige; Itadani, Atsushi; Kumashiro, Ryotaro; Fujimoto, Takao; Nagao, Mahiko

doi:10.1039/b316172m

Cited by 14 publications

(12 citation statements)

References 80 publications

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“…Concerning the TM-exchanged systems, we are not aware of experiments using chabazite-type structures, but we can compare our results to experimental data obtained for other zeolites. For example, a heat of N 2 adsorption of 85 kJ mol -1 has been observed for Cu-ZSM-5, agreeing very well with our DFT results [78]. Also, a moderately high heat of N 2 adsorption of 37 kJ mol -1 has been measured in silver-exchanged zeolite A, rendering this material interesting for N 2 /O 2 separation [79].…”

Section: Comparison With Experimental Studiessupporting

confidence: 70%

A DFT-D study of the interaction of methane, carbon monoxide, and nitrogen with cation-exchanged SAPO-34

Fischer¹,

Bell

2014

Zeitschrift Für Kristallographie - Crystalline Materials

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Density-functional theory calculations including a semi-empirical dispersion correction (DFT-D) are employed to study the interaction of small guest molecules (CH 4 , CO, N 2 ) with the cation sites in the silicoaluminophosphate SAPO-34. Eight different cations from three different groups (alkali cations, alkaline earth cations, transition metals) are included in the study. For each case, the total interaction energy as well as the non-dispersive contribution to the interaction are analysed. Electron density difference plots are used to investigate the nature of this non-dispersive contribution in more detail. Despite a non-negligible contribution of polarisation interactions, the total interaction remains moderate in systems containing main group cations. In SAPOs exchanged with transition metals, orbital interactions between the cations and CO and N 2 lead to a very strong interaction, which makes these systems attractive as adsorbents for the selective adsorption of these species. A critical comparison with experimental heats of adsorption shows reasonable quantitative agreement for CO and N 2 , but a pronounced overestimation of the interaction strength for methane. While this does not affect the conclusions regarding the suitability of TM-exchanged SAPO-34 materials for gas separations, more elaborate computational approaches may be needed to improve the quantitative accuracy for this guest molecule.

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Section: Comparison With Experimental Studiessupporting

confidence: 70%

A DFT-D study of the interaction of methane, carbon monoxide, and nitrogen with cation-exchanged SAPO-34

Fischer¹,

Bell

2014

Zeitschrift Für Kristallographie - Crystalline Materials

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“…Several experimental studies showed that N 2 adsorbs on single Cu + sites within the ZSM-5 structure with an interaction energy of about 19 kcal mol À1 and an associated IR frequency of the N-N stretching of 2295 cm À1 . [12][13][14][15][16][17][18][19][20][21][22]24 The same studies showed that this type of adsorption is generally reversible if the catalyst is evacuated at room temperature and that other Cu + sites in the ZSM-5 structure are instead inactive for N 2 adsorption. 19 At the same time, computational studies showed that small molecules such as N 2 , CO, NO, NO 2 and H 2 O adsorb on two general types of isolated copper sites in Cu-ZSM-5, where the Cu + ions are coordinated (i) by 3 or 4 oxygen atoms or (ii) by 2 oxygen atoms of a single AlO 4 tetrahedron, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…Further, the possibility that active sites may be pairs of Cu ions rather than isolated Cu ions, was suggested for two reasons: (i) the turnover frequency (TOF) of the NO decomposition increases with the copper loading following a peculiar sigmoidal curve with a maximum at about the exchange capacity of the ZSM-5 catalysts; 9,10 (ii) the maximum value of the TOF can be linearly correlated to the number of aluminium atoms per unit cell of the ZSM-5 zeolite. 11 Further, it is known that N 2 adsorbs reversibly on Cu + species at room temperature with on-top symmetry giving a N-N stretching vibration at 2295 cm À1 which disappears on evacuation, [12][13][14][15] while recent experimental studies have shown that Cu-ZSM-5 catalysts also adsorb a small fraction of N 2 in an irreversible way at 273-320 K. [16][17][18][19][20][21][22] The irreversibly adsorbed N 2 was found to be IR silent, suggesting the coordination in a symmetric environment, possibly to dimeric Cu + species. 22 Notably, a linear relationship was found between the fraction of N 2 irreversibly adsorbed at low temperature (273-320 K) and the catalytic data for the NO decomposition by Cu-ZSM-5.…”

Section: Introductionmentioning

confidence: 99%

A computational study on N₂adsorption in Cu-ZSM-5

Morpurgo

Moretti

Bossa

2007

Phys. Chem. Chem. Phys.

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The present computational study investigates the adsorption of N(2) by Cu-ZSM-5, with particular regard to the interaction with pairs of Cu(+) ions, employing simple cluster models in the calculations. It shows that several interaction patterns between N(2) and couples of Cu(+) sites are possible within the Cu-ZSM-5 structure. In particular, when pairs of Cu(+) ions are located at opposite sides of ten-membered rings, in the region where linear and sinusoidal channels intersect each other, a quasi-linear Cu-N-N-Cu adsorption occurs. Although lattice restraints cause small deviations from linearity, such interaction turned out to be more favourable than other adsorption patterns within the Cu-ZSM-5 structure. The linearity of the Cu-N-N-Cu fragment and the relatively low concentration of the related sites cause a low extinction coefficient for the N-N IR stretching mode, which is usually detected with very low intensity or not detected at all. The results of the present calculations may explain the experimental evidence for a nearly IR-silent fraction of nitrogen strongly adsorbed in the Cu-ZSM-5 catalyst which, as shown in a previous work, is linearly related to the number of active sites for NO decomposition.

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“…30,34,37 However, there are still some ambiguity in the interpretation of experimental results. It is evident that the differences in Cu-zeolite preparation (ionexchange procedure and Cu 21 reduction in particular 9,20,38,39 ) can be the cause for these differences.…”

Section: -22 and References Therein)mentioning

confidence: 99%

On the site-specificity of polycarbonyl complexes in Cu/zeolites: combined experimental and DFT study

Bulánek

Drobná

Nachtigall

et al. 2006

Phys. Chem. Chem. Phys.

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The preferred Cu(+) sites and formation of mono-, di-, and tricarbonyl complexes in the Cu-FER were investigated at the periodic density functional theory level and by means of FTIR spectroscopy. The site-specificity of adsorption enthalpies of CO on Cu-FER and of vibrational frequencies of polycarbonyl complexes were investigated for various Cu(+) sites in Cu-FER. Large changes in the Cu(+) interaction with the zeolite framework were observed upon the formation of carbonyl complexes. The dicarbonyl complexes formed on Cu(+) in the main channel or on the intersection of the main and perpendicular channels are stable and both, adsorption enthalpies and CO stretching frequencies are not site-specific. The fraction of Cu(+) ions in the FER cage, that cannot form dicarbonyl can be determined from IR spectra (about 7% for the Cu-FER with Si/Al = 27.5 investigated here). The tricarbonyl complexes can be formed at the Cu(+) ions located at the 8-member ring window at the intersection of main and perpendicular channel. The stability of tricarbonyl complexes is very low (DeltaH degrees (0 K)>or=-4 kJ mol(-1)).

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Anomalous valence changes and specific dinitrogen adsorption features of copper ion exchanged in ZSM-5 zeolite prepared from an aqueous solution of [Cu(NH3)2]+

Cited by 14 publications

References 80 publications

A DFT-D study of the interaction of methane, carbon monoxide, and nitrogen with cation-exchanged SAPO-34

A DFT-D study of the interaction of methane, carbon monoxide, and nitrogen with cation-exchanged SAPO-34

A computational study on N₂adsorption in Cu-ZSM-5

On the site-specificity of polycarbonyl complexes in Cu/zeolites: combined experimental and DFT study

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Anomalous valence changes and specific dinitrogen adsorption features of copper ion exchanged in ZSM-5 zeolite prepared from an aqueous solution of [Cu(NH3)2]+

Cited by 14 publications

References 80 publications

A DFT-D study of the interaction of methane, carbon monoxide, and nitrogen with cation-exchanged SAPO-34

A DFT-D study of the interaction of methane, carbon monoxide, and nitrogen with cation-exchanged SAPO-34

A computational study on N2adsorption in Cu-ZSM-5

On the site-specificity of polycarbonyl complexes in Cu/zeolites: combined experimental and DFT study

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A computational study on N₂adsorption in Cu-ZSM-5