Infrared spectroscopic investigation of CO adsorption on SBA-15- and KIT-6-supported nickel phosphide hydrotreating catalysts

Tamás I. Korányi, Eva Pfeifer, J. Mihály, Karin Föttinger

Research output: Contribution to journalArticle

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Abstract

The infrared (IR) spectra of CO adsorbed on 10,20, and 30 wt % nickel phosphide-containing reduced SBA-15 and KIT-6 mesoporous silica-supported catalysts have been studied at 300-473 K. On the catalysts containing a stoichiometric amount of phosphorus with 20 wt % loading, the most intense IR absorption band was observed at 2097-2099 cm-1, which was assigned to CO terminally bonded to coordinatively unsaturated Niδ+ (0 <δ <1) sites. The frequency of this band was 15 cm-1, higher than that in the spectrum of a reduced Ni2P/SiO2 catalyst, indicating a modified Ni-P charge distribution. This band shifted to lower wavenumbers, and its intensity decreased, while the relative intensity of another band at 2191-2194 cm-1 assigned to CO terminally bonded to P increased going to catalytically less active, excess-P-containing SBA-15-supported catalysts. CO also adsorbed as a bridged carbonyl (1910 cm -1) and as Ni(CO)4 (2050 cm-1) species, and the formation of surface carbonates was also identified. The nature of the surface acidity was studied by temperature-programmed desorption of ammonia (NH 3-TPD). Weak and strong acid sites were revealed, and the high excess-P-containing catalyst released the highest amount of ammonia, indicating that a high concentration of strong acidity can be disadvantageous for reaching high hydrotreating catalytic activity. The modified Ni-P charge distribution, the mode of CO adsorption on surface nickel phosphide sites, as well as the acidity can be directly connected to the catalytic activity of these mesoporous silica-supported catalysts.

Original languageEnglish
Pages (from-to)5126-5130
Number of pages5
JournalJournal of Physical Chemistry A
Volume112
Issue number23
DOIs
Publication statusPublished - Jun 12 2008

Fingerprint

phosphides
Carbon Monoxide
Nickel
nickel
Infrared radiation
Adsorption
catalysts
Catalysts
adsorption
Catalyst supports
Acidity
acidity
Charge distribution
Temperature programmed desorption
Ammonia
Silicon Dioxide
charge distribution
catalytic activity
ammonia
Catalyst activity

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Infrared spectroscopic investigation of CO adsorption on SBA-15- and KIT-6-supported nickel phosphide hydrotreating catalysts. / Korányi, Tamás I.; Pfeifer, Eva; Mihály, J.; Föttinger, Karin.

In: Journal of Physical Chemistry A, Vol. 112, No. 23, 12.06.2008, p. 5126-5130.

Research output: Contribution to journalArticle

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