Co adsorption-desorption properties of cation-exchanged NaX zeolite and supported ruthenium

Gupta, Nandini; Kamble, V.S.; Rao, K. Annaji; Iyer, R.M.

doi:10.1016/0021-9517(89)90283-2

Cited by 22 publications

(14 citation statements)

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“…As will be discussed later, 18 O isotope studies show that the formation of CO 2 (Figures 1-3) results entirely from CO that gets attached to an oxygen, thus resulting in the abstraction of the bound oxygen and leading thereby to monoisotopically labeled CO 2 . This indicates that the binding of CO to oxygen is very strong, and consequently the isotope shifts produced will vary from site to site, due to mixing of the C 18 O vibrations with C 16 O or other vibrations. All the C-O bands, on the other hand, showed a uniform diatomic type isotopic shift as mentioned already.…”

Section: Discussionmentioning

confidence: 99%

“…We have also reported the thermal desorption spectroscopy results to reveal the existence of multiple CO binding states in zeolite X which were found to be modified by the charge-balancing cations. 15,16 In continuation, we now report the results of our FTIR spectroscopic study on adsorption of CO over zeolite Y at temperatures in the range 300-470 K and at pressures of 10-500 Torr (1 Torr ) 133.3 Pa). The effect of cation exchange on CO binding states has been evaluated.…”

Section: Introductionmentioning

confidence: 93%

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Fourier Transform Infrared Study on the Encapsulation of CO in Zeolite Y under the Moderate Temperature and Pressure Conditions

et al. 1998

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were observed during the room-temperature adsorption of CO over NaY zeolite. This was accompanied by the appearance of a prominent band at 2356 cm -1 along with the sidebands at 2336, 2342-2348, and 2364-2370 cm -1 in the ν 3 region of CO 2 vibrations. The intensity and the frequency of these bands showed monotonic changes on evacuation, temperature rise, and exchange of Na + ions with a proton or a group IIA cation and also on using the isotopically labeled CO. For instance, the adsorption of isotopic 13 C 16 O and 12 C 18 O gases gave rise to a uniform red shift in all the major ν(CO) bands, corresponding to a frequency ratio of ν( 13 CO)/ν( 12 CO) ≈ 0.978 and ν(C 18 O)/ν(C 16 O) ≈ 0.976. Similarly, all the asymmetric stretching bands of CO 2 showed a uniform isotopic shift corresponding to ν( 13 C)/ν( 12 C) ≈ 0.971. Furthermore, the intensity of most of the above-mentioned bands in ν(CO) and ν 3 (CO 2 ) regions exhibited an exponential type growth behavior with increasing adsorbate pressure, though the extent of this growth was different for individual vibrations. No significant change was, however, observed in the frequency and the intensity of the hydroxyl region bands on adsorption of CO under experimental conditions of this study. Arguments are presented to show that the observations of this study are not in harmony with the reported modes of direct CO adsorption at the specific zeolitic sites such as the charge-balancing cations, Al 3+ sites, or the Bronsted acid sites. Instead, the formation of the weakly held (CO) n and (CO 2 ) n molecular clusters occluded in the zeolitic cavities and stabilized under the cation field is in conformity with the data of this study.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 93%

Fourier Transform Infrared Study on the Encapsulation of CO in Zeolite Y under the Moderate Temperature and Pressure Conditions

et al. 1998

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“…Κατ' άλλους ερευνητές [114,115] ο ζεολιθικός φορέας είναι πιθανό να επηρεάζει τις καταλυτικές ιδιότητες με πιο άμεσο τρόπο. Σε πειράματα προσρόφησης και εν συνεχεία θερμοκρασιακά προγραμματισμένης εκρόφησης CO από ζεολίθους MX και καταλύτες RuMX (Μ : Li, Η, Ca, Mg και La), φάνηνε η πιθανότητα να προσροφάται το CO όχι μόνο από το ρουθήνιο, αλλά και από τα όξινα κέντρα Lewis του υλικού.…”

Section: καταλυτες ρουθηνιουunclassified

“…Η προσρόφηση αυτή θεωρήθηκε παρόμοιας φύσης με την χημειορρόφηση του αερίου από τα μέταλλα. Η παρουσία των εξουδετερωτικών ιόντων Μ η+ , ενίσχυε το φαινόμενο με την δημιουργία πρόσθετων κέντρων ρόφησης και την μεταβολή της οξύτητας του ζεολίθου [115].…”

Section: καταλυτες ρουθηνιουunclassified

“…Η κλασσική εξίσωση BET κρίνεται γενικά ανεπαρκής για τον υπολογισμό του όγκου πόρων στους ζεολίθους. Λόγω όμως της απλότητας της μεθόδου, ειδικές επιφάνειες BET αναφέρονται συχνά στην διεθνή βιβλιογραφία [73,115,[188][189][190] και έχουν αποδειχθεί χρήσιμες για την εκτίμηση της κρυσταλλικότητας των ζεολίθων.…”

Section: παρασκευη καταλυτωνunclassified

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Υδρογονωση Μονοξειδιου Του Ανθρακα Σε Ζεολιθικους Καταλυτες Νικελιου, Κοβαλτιου Και Ρουθηνιου

Κορίλη¹,

Korili²

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Carbon monoxide hydrogénation has been investigated on Ni, Co, Ru and NiCo, RuCo bimetallics on zeolite Y, at atmospheric pressure and temperatures of 200-400°C. Catalysts were prepared by ion exchange to a total metal loading of 2% by weight; in the case of monometallic nickel catalysts, metal loadings of 2 to 5% were also examined.Controlled ion exchange ensured uniform metal distribution on the zeolite support. Atomic absorption spectroscopy and thermogravimetric analysis were used for the determination of catalyst composition and extent of exchange. Total surface area measurements and X-ray diffraction analysis were applied to samples in several stages of preparation, activation and activity testing. The prepared catalysts exhibited high surface area and crystallinity throughout their use.Catalysts were reduced in pure hydrogen by slow heating to 450°C. Metal surface area development depended on the nature of the active component, as evidenced by X-ray diffraction and hydrogen chemisorption at 35°C. Nickel agglomerated to form large crystallites on the external surface of the support, ruthenium remained finely dispersed within the zeolite cavities, while cobalt was stabilized by the zeolite and poorly reduced. Reduction of cobalt in bimetallic catalysts was enhanced by the presence of nickel or ruthenium, probably due to spillover of atomic hydrogen. X-ray analysis of bimetallics did not reveal the presence of any new metal phases.A number of techniques were employed to obtain catalyst dispersion; among these, volumetric chemisorption proved the most suitable one. Gas chemisorption on the active metals was relatively low, weak and to a large extent reversible, probably due to metal -support interactions. Ru and RuCo catalysts had the highest dispersion, followed by NiCo and Ni.A differential reactor was used for catalyst testing at a space velocity of 12500 h-i and H2/CO ratio of 3. At these conditions, reaction products on Ni, NiCo were Ci -C3 light hydrocarbons, while Ru and RuCo produced hydrocarbons in the Ci -CO range. Normal paraffins and α-olefins were the products of the hydrogénation reaction, while branched paraffins and ß-olefins were formed by secondary reactions of the primary synthesis products on zeolite acid sites. At 300°C carbon dioxide was formed, due to CO disproportionation and water-gas shift reaction. Carbon monoxide viii 2.5. ΔΙΜΕΤΑΛΛΙΚΟΙ ΚΑΤΑΛΥΤΕΣ 75 3. ΖΕΟΛΙΘΟΙ 85 3.1.

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Density functional study of hydrogen-bonded systems: from gas-phase adducts to catalytically relevant systems

1997

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Co adsorption-desorption properties of cation-exchanged NaX zeolite and supported ruthenium

Cited by 22 publications

References 21 publications

Fourier Transform Infrared Study on the Encapsulation of CO in Zeolite Y under the Moderate Temperature and Pressure Conditions

Fourier Transform Infrared Study on the Encapsulation of CO in Zeolite Y under the Moderate Temperature and Pressure Conditions

Υδρογονωση Μονοξειδιου Του Ανθρακα Σε Ζεολιθικους Καταλυτες Νικελιου, Κοβαλτιου Και Ρουθηνιου

Density functional study of hydrogen-bonded systems: from gas-phase adducts to catalytically relevant systems

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