Quantitative IR studies of the concentration of different nickel sites in NiZSM-5 zeolites

doi:10.1016/j.micromeso.2012.03.027

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punktacja MNiSW [2012 A]: 35

tytuł	Quantitative IR studies of the concentration of different nickel sites in NiZSM-5 zeolites
autor	Góra-Marek Kinga , Glanowska Anna, Datka Jerzy
tytuł czasopisma	Microporous and Mesoporous Materials
tom	158
data wydania	2012
strony	162-169
ISSN	1387-1811
eISSN	1873-3093
DOI	10.1016/j.micromeso.2012.03.027
adres URL	http://www.sciencedirect.com/science/article/pii/S138718111200176X
data dostępu	2015-04-29
język	angielski
język czasopisma	angielski
abstrakt w j. angielskim	Quantitative IR studies were realized in order to determine the concentration of Ni 2+ and Ni + in two zeo- lites NiZSM-5 differing in Si/Al and nickel content. The NiZSM-5 zeolite of Si/Al = 11.5 contained most of Ni 2+ in exchange positions whereas another one, of Si/Al = 40 contained most of Ni 2+ in the form of oxides. Also the Ni + ions in NiZSM-5 reduced by CO were investigated. The experimental procedure of quantita- tive studies was elaborated and the condition of stoichiometric reaction between probe molecule (CO or NO) and sorption site (Ni 2+ or Ni + ) was fulfilled: each CO or NO molecule introduced into the IR cell reacted with one Ni 2+ forming Ni 2+ (CO) or Ni 2+ (NO) adducts. The procedure was also elaborated for quan- titative studies of concentration of Ni + in zeolite reduced. The absorption coefficients of IR bands of Ni 2+ (CO), Ni 2+ (NO) and Ni + (CO) at 2212, 1898, and 2109 cm 1 , respectively were determined, and finally the concentrations of Ni 2+ and Ni + were calculated. In the zeolite of Si/Al = 11.5 the concentration of Ni 2+ in exchange positions determined by our IR studies was nearly the same as that determined by chemical analysis. The values of the absorption coefficients turned out to be independent on the probe molecule (CO or NO). In the zeolite of Si/Al = 40, containing the most of Ni 2+ in the form of oxides, the concentration of Ni 2+ found by IR was 66% of concentration of Ni determined by chemical analysis demonstrating that dispersion of Ni 2+ was low and some of Ni 2+ was hidden inside oxide clusters being inaccessible to probe molecules. In reduced NiZSM-5 of Si/Al = 11.5 and 40 the concentration of Ni + determined by IR studies was nearly the same as concentration of Ni determined by chemical analysis. In NiZSM-5 of Si/Al = 40 the dispersion of Ni increased distinctly upon the reduction, and all Ni + cations became accessible to probe molecules or reactants.
słowa kluczowe w j. angielskim	carbon monoxide, ZSM-5, nitrogen monoxide, quantitative IR studies
punktacja wydziałowa	35
wydział:instytut/zakład/katedra	Wydział Chemii : Zakład Chemii Nieorganicznej
typ	artykuł w czasopiśmie
podtyp	artykuł