Infrared spectroscopic studies of carbon monoxide adsorbed on a series of silica-supported copper catalysts in different oxidation states

Journal Article · Mon May 01 04:00:00 EDT 1989 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(89)90230-3· OSTI ID:6473414

Kohler, M A; Wainwright, M S; Trimm, D L; Cant, N W ^[1]

---

1. Macquarie Univ., New South Wales (Australia) Univ. of South Wales (Australia)

Infrared spectroscopy has been used to study the adsorption of carbon monoxide (358-493 K, 0.1-20 kPa) on four copper-on-silica (2-10 wt% Cu) catalysts prepared by the ion-exchange technique. The measurements are made for each sample in three different states: unreduced (predominantly Cu{sup 2+}), and reduced (Cu{sup 0}), and partially reoxidized in nitrous oxide (Cu{sup +}). On unreduced samples, a major absorption band between 2127 and 2132 cm{sup {minus}1} due to CO adsorbed on small CuO particles and a weak band at 2199 cm{sup {minus}1} due to CO on isolated Cu{sup 2+} ions incorporated in the silica surface have been identified. The former adsorption obeys a Langmuir isotherm with a heat of adsorption of 29 kJ/mol independent of CuO particle size and surface coverage. After catalyst reduction, the major absorption band lies between 2090 and 2113 cm{sup {minus}1} and arises from CO linearly bound to very small (1- to 5-nm) copper metal clusters. The observed frequency shifts indicate the presence of steps and terraces similar to low index Cu planes in very small particles (1- to 2-nm), and the presence of similar higher index Cu planes on larger clusters (2- to 5-nm). The absorption is described by a Freundlich isotherm with the heat of CO adsorption decreasing with coverage from 50 to 22 kJ/mol on bigger particles but more constant (27 to 22 kJ/mol) on small particles. A surface copper/CO atomic ratio increasing from 5 to 12 is established at equilibrium saturation between 358 and 493 K using extinction coefficients determined in this study. In the reduced catalysts, a weakly adsorbed ({Delta}H{sub a} = {minus}20 kJ/mol) species assigned to CO bound to isolated Cu{sup +} ions is also found and absorbs at 2175 cm{sup {minus}1}. The frequency of this band does not vary with catalyst loading and is not affected by reoxidation of the catalyst in nitrous oxide.

• OSTI ID: 6473414
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 117:1; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010408* -- Coal
Lignite
& Peat-- C1 Processes-- (1987-)
ADSORPTION
ADSORPTION HEAT
ADSORPTION ISOTHERMS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYST SUPPORTS
CATALYSTS
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTIONS
COPPER
COPPER COMPOUNDS
COPPER OXIDES
ELEMENTS
ENTHALPY
INFRARED SPECTRA
ISOTHERMS
METALS
MINERALS
NITROGEN COMPOUNDS
NITROGEN OXIDES
NITROUS OXIDE
OXIDATION
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PARTICLE SIZE
PHYSICAL PROPERTIES
REDUCTION
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SIZE
SORPTION
SORPTIVE PROPERTIES
SPECTRA
SPECTROSCOPY
SURFACE PROPERTIES
SYNTHESIS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS