Structure refinement, electron microscopy, and solid-state magic angle spinning nuclear magnetic resonance characterization of AlPO4-52: An aluminophosphate with a large cage

McGuire, N.K.; Bateman, Charles A.; Blackwell, C. S.; Wilson, S.T.; Kirchner, Richard M.

doi:10.1016/0144-2449(94)00040-y

Cited by 36 publications

(11 citation statements)

References 7 publications

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“…Selective Catalytic Reduction (SCR) is an effective technology that is nowadays widely employed 3 for the abatement of NO x emissions from mobile sources, such as Diesel vehicles. The technology 4 is based on the use of NH 3 for NO x reduction, which can occur via various reactions. The Standard 5 SCR reaction (1), 6…”

Section: Introduction 1mentioning

confidence: 99%

“…globally account for the NH 3 -NO x reactivity in modern SCR converters, which are based on metal 11 (Cu, Fe) exchanged zeolite catalysts. The Fast SCR reaction (2) is of particular interest, since it 12 enables high NO x conversions at low temperatures.…”

Section: Introduction 1mentioning

confidence: 99%

“…The Fast SCR reaction (2) is of particular interest, since it 12 enables high NO x conversions at low temperatures. Several literature studies on both V-based [1-4] 13 and metal promoted zeolite catalysts [5][6][7][8] have unveiled the redox nature of the Fast SCR 14 mechanism, whose rate is enhanced by the presence of strongly oxidizing species like NO 2 and 15 surface nitrates: nitrates reduction by NO has been identified as the key step of the process [1][2][3][4][5][6][7][8]. 16…”

Section: Introduction 1mentioning

confidence: 99%

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In-situ DRIFTS measurements for the mechanistic study of NO oxidation over a commercial Cu-CHA catalyst

Ruggeri

Nova

Tronconi

et al. 2015

Applied Catalysis B: Environmental

130

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3We report a mechanistic DRIFTS in-situ study of NO 2 , NO + O 2 and NO adsorption on a 4 commercial Cu-CHA catalyst for NH 3 -SCR of NOx. Both pre-reduced and pre-oxidized catalyst 5 samples were investigated with the aim to clarify mechanistic aspects of the NO oxidation to NO 2 6 as a preliminary step towards the study of the Standard SCR reaction mechanism at low 7 temperatures. Nitrosonium cations (NO + , N oxidation state = +3) were identified as key surface 8 intermediates in the process of NO (+2) oxidation to NO 2 (+4) and nitrates (+5). While NO + and 9 nitrates were formed simultaneously upon catalyst exposure to NO 2 , nitrates evolved consecutively 10 to NO + when the catalyst was exposed to NO + O 2 , suggesting that nitrite-like species, and not NO 2 , 11 are formed as the primary products of the NO oxidative activation over Cu-CHA. Upon catalyst 12 exposure to NO only, i.e. in the absence of gaseous O 2 , NO + and then nitrates were formed on a 13 preoxidized sample but not on a prereduced one, which demonstrates the red-ox nature of the NO 14 oxidation mechanism. The negative effect of H 2 O on NO + and nitrates formation was also clearly 15 established. Assuming small Cu clusters, in the form of Cu dimers, as the active sites for NO 16 oxidation to NO 2 , we propose a mechanism which reconciles all the experimental observations. In 17 particular, we show that such a mechanism also explains the observed kinetic effects of H 2 O, O 2 18 and NO 2 on the NO oxidation activity of the investigated Cu zeolite catalyst. 19 20 21

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Section: Introduction 1mentioning

confidence: 99%

Section: Introduction 1mentioning

confidence: 99%

Section: Introduction 1mentioning

confidence: 99%

See 1 more Smart Citation

In-situ DRIFTS measurements for the mechanistic study of NO oxidation over a commercial Cu-CHA catalyst

Ruggeri

Nova

Tronconi

et al. 2015

Applied Catalysis B: Environmental

130

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“…The crystal structures of AlPO 4 -18, AlPO 4 -40, AlPO 4 -52, and VPI-5 were fully optimized starting from reported X-ray structures [27][28][29][30] . The P1 space group was assumed.…”

mentioning

confidence: 99%

Comparing the Acidities of Microporous Aluminosilicate and Silico-Aluminophosphate Catalysts: A Combined Quantum Mechanics-Interatomic Potential Function Study

Sauer

Schröder

Termath

1998

Collect. Czech. Chem. Commun.

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DFT-B3LYP calculations are performed on 4-ring models of aluminophosphates (AlPOs) and silico-aluminophosphates (SAPOs). The results are used to fit the parameters of ion pair shell model potential functions. The potentials obtained are tested in lattice energy minimizations for berlinite and the microporous materials AlPO-18, AlPO-40, AlPO-52, and VPI-5. Not only does the potential reproduce the observed structures (average error of the cell constants 1.3%), it also predicts vibrational frequencies over the whole frequency range equally well (maximum deviation 50 cm-1). The potential is used to predict the structures and properties of Bronsted acid sites in an aluminosilicate and a SAPO with the chabazite framework structure (HSSZ-13 and HSAPO-34). A new combined quantum mechanics-intermolecular potential function approach (QM-Pot) is used at the DFT level. Comparison is made with full periodic DFT calculations using plane wave basis sets. The deprotonation energies corrected for systematic errors of the methods used are 1 231-1 235 and 1 261-1 280 kJ/mol for HSSZ-13 and HSAPO-34, respectively. The same acid site has a lower acidity in a SAPO than in an aluminosilicate zeolite of the same structure.

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“….). The cage length of 5 Å is as in gmelinite (GME), 10 Å as in chabazite (CHA), 15 Å as in AlPO 4 -52 (AFT) [85]. Zeolite Linde D [86], Phi [87], LZ-276 [88] and LZ-277 [87] are disordered forms of chabazite with different levels of faulting probabilities.…”

Section: Abc-6 Familymentioning

confidence: 99%

Stacking disorders in zeolites and open-frameworks – structure elucidation and analysis by electron crystallography and X-ray diffraction

Willhammar¹,

Zou²

2013

Zeitschrift für Kristallographie - Crystalline Materials

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Abstract. Intergrowth and stacking disorders are often found in minerals and synthetic zeolites and inorganic openframeworks. Structure elucidation of stacking disorders in these materials have been difficult and structure solution of stacking disorders in unknown zeolites and open-frameworks has been challenging. There exist no standard methods for structure analysis of such disordered materials. In this review we present various stacking disorders and intergrowth in a number of representative zeolite families containing stacking disorders. These include zeolite beta, SSZ-26/SSZ-33, ITQ-39, ABC-6, ZSM-48, SSZ-31, UTD-1, faujasite FAU/EMT, pentasil ZSM-5/ZSM-11, ITQ-13/ITQ-34, ITQ-22/ITQ-38 etc. Stacking disorders in open-frameworks containing mixed coordinations, including titanosilicates ETS-10 and ETS-4, and the silicogermanate SU-JU-14 are also described. Various crystallographic methods used for solving disordered structures are summarized. The methods include powder X-ray diffraction (PXRD), electron diffraction, high resolution transmission electron microscopy (HRTEM), and single-crystal X-ray diffraction. Examples of model building combined with simulations of PXRD and single crystal X-ray diffraction to verify the structure models are given.

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Structure refinement, electron microscopy, and solid-state magic angle spinning nuclear magnetic resonance characterization of AlPO4-52: An aluminophosphate with a large cage

Cited by 36 publications

References 7 publications

In-situ DRIFTS measurements for the mechanistic study of NO oxidation over a commercial Cu-CHA catalyst

In-situ DRIFTS measurements for the mechanistic study of NO oxidation over a commercial Cu-CHA catalyst

Comparing the Acidities of Microporous Aluminosilicate and Silico-Aluminophosphate Catalysts: A Combined Quantum Mechanics-Interatomic Potential Function Study

Stacking disorders in zeolites and open-frameworks – structure elucidation and analysis by electron crystallography and X-ray diffraction

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