Determination of Polycarbonyl Species on Nickel-Containing Catalysts by Adsorption of CO Isotopic Mixtures

Abstract

The possibilities to identify polycarbonyl species using different CO isotopic mixtures ( 12 C 16 O ? 13 C 16 O and 12 C 16 O ? 13 C 18 O) are regarded. The examples concern two nickel-containing catalysts, Ni-ZSM-5 and Ni/SiO 2 . Ni ? ions, present in Ni-ZSM-5 reduced by CO, can coordinate up to three CO molecules each. Ni ? (CO) 2 dicarbonyl structures are well established by both, 12 C 16 O ? 13 C 16 O and 12 C 16 O ? 13 C 18 O isotopic mixtures. However, the 12 C 16 O ? 13 C 18 O mixture is advantageous in the determination of tricarbonyl structures. This is due to the much higher 12 C 16 O ? 13 C 18 O isotopic shift (about 100 cm -1 ) as compared to the 12 C 16 O ? 13 C 16 O shift (ca. 50 cm -1 ) which allows a better resolution of the different carbonyl bands. The use of 12 C 16 O ? 13 C 18 O mixtures also permits assignment of the bands due to polycarbonyl structures when CO is adsorbed on a reduced Ni/SiO 2 catalyst.

Influence of copper on nickel-based catalysts in the conversion of glycerol

“…The bands 1952-1892 cm − 1 can be assigned to CO molecules bridge-bonded to Ni atoms. The bands below 1890 cm − 1 are attributed to Ni 3 CO and Ni 4 CO species [53]. The addition of Cu to the Ni catalysts ( Fig.…”

Silver-catalyzed low-temperature CO isotopic scrambling reaction:12C16O +13C18O →12C18O +13C16O

“…The reaction proceeded on a silver-loaded zeolite and did not occur (at ambient temperature) on several other catalysts, e.g. Cu-ZSM-5, 4 Cu/MCM-41, 5 Fe-ZSM-5 and Fe-BEA, 6 Ni-ZSM-5 and Ni/SiO 2 , 7 Ru/ZrO 2 , 8 Pt/SiO 2 9 and Pt-Cu/SiO 2 . 10 Moreover, we found that an optimal reduction degree of the sample was needed for the reaction.…”

Precise Identification of the Infrared Bands of the Polycarbonyl Complexes on Ni–MOR Zeolite by12C16O–13C18O Coadsorption and Computational Modeling

“…In order to obtain spectral evidence of the di-and tricarbonyls structures, we have studied adsorption of CO isotopic mixtures. In this case, we utilized mixtures of 12 C 16 O and 13 C 18 O because, as already reported, 9,11,44 these mixtures provide a better spectral resolution as compared to the widely used 12 C 16 O/ 13 C 16 O mixtures. Also, to obtain more information on the spectral performance of the mixed-ligand complexes, we have utilized two isotopic mixtures with 12 C 16 O/ 13 C 18 O molar ratios of 1:1 and 3:1, respectively.…”

“…The goal of the present work is to clarify the complex spectra of the various di- and tricarbonyl species formed on nickel cations in Ni–MOR zeolites and to check the formation of tricarbonyl complexes of Ni + , suggested earlier . For identification of all individual IR bands of the polycarbonyl complexes containing either the same or mixed isotopic probe molecules, we modeled the corresponding species with the density functional method.…”

“…The goal of the present work is to clarify the complex spectra of the various di-and tricarbonyl species formed on nickel cations in Ni−MOR zeolites and to check the formation of tricarbonyl complexes of Ni + , suggested earlier. 9 For identification of all individual IR bands of the polycarbonyl complexes containing either the same or mixed isotopic probe molecules, we modeled the corresponding species with the density functional method. Note that, although calculations according to the approximate force field model give good results for dicarbonyl species, they fail to predict unambiguously the spectral parameters of tri-and tetracarbonyls.…”