Kinetic and mechanistic study of CO oxidation over nanocomposite Cu−Fe−Al oxide catalysts

Abstract

The oxidation of CO has been studied over FeÀ Al and CuÀ FeÀ Al oxide nanocomposite catalysts prepared by melting of copper, iron, and aluminum nitrates. It was shown that the addition of copper significantly increases the catalytic activity of the FeÀ Al nanocomposites. The catalysts were characterized by lowtemperature nitrogen adsorption, X-ray diffraction (XRD), and Xray photoelectron spectroscopy (XPS). It was found that the catalysts contain Fe 2 O 3 with the hematite structure modified by aluminum. Copper in the three-component catalyst is in the Cu 2 + state, forming CuO and CuFeO x clusters on the catalyst surface. An increase in the copper content leads to the formation of a Cu x Al y Fe 3-x-y O 4 spinel phase. In situ XPS study showed that a treatment of the catalysts in a CO flow leads to the reduction of both copper and iron cations into the metallic state. In contrast, a treatment in a CO/O 2 flow leads only to partial reduction of Cu 2 + to Cu 1 + , while Fe 3 + are not reduced. The tests of catalytic activity performed in a flow fixed bed reactor using a CO pulse technique showed that the light-off temperature in the oxidation of CO over the CuÀ FeÀ Al nanocomposite catalysts depends on the copper content. The minimal light-off temperature was achieved over the catalyst containing 5 wt% CuO. In addition, we performed kinetic measurements in a differential reactor and obtained the activation energy and the reaction orders with respect to the reactants. The reaction mechanism of the catalytic oxidation of CO and the origin of active species are discussed.

Versatile Layered Hydroxide Precursors for Generic Synthesis of Cu‐Based Materials

“…[ 33 ] The synergistic effects between Cu and other transition metals, such as Fe, Co, and Ni, during catalytic CO oxidation have been widely studied. [ 34 ] Thus, in this study, we examined the CO oxidation activities of Cu‐based metal oxide catalysts derived from 15 different bimetal HDSs containing relatively large secondary metal cations (Bi, Dy, Er, Eu, Gd, Ho, La, Lu, Nd, Pr, Sm, Tb, Tm, Y, or Yb). Since the NO 3 − and OH − anions in the Cu‐based HDSs were fully decomposed and disappeared at temperatures below 400 °C, regardless of the type of metal cation used (Figure S17, Supporting Information), the possibility of any influence from surface anion impurities derived from the precursor, such as nitrates, on catalytic activities, was ruled out after calcination at temperatures above 400 °C.…”

Synthesis of Self-Supported Cu/Cu3P Nanoarrays as an Efficient Electrocatalyst for the Hydrogen Evolution Reaction

“…The peaks at 933.1 eV and 935.1 eV are assigned to the Cu δ+ in the Cu 3 P and oxidized Cu for the Cu 2p 3/2 energy level, while the peaks at 940.8 and 944.1 eV belong to the satellite peaks of Cu 2p 3/2 . The three peaks appearing at 952.8, 955.2 and 962.9 eV are indexed to the Cu δ+ in the Cu 3 P, oxidized Cu and the satellite for Cu 2p 1/2 , respectively [51,52]. In Figure 3b, the peak at 133.6 eV could be indexed to oxidized phosphate species, resulting from the exposure of the sample to air.…”

Ni–Cu High-Loaded Sol–Gel Catalysts for Dehydrogenation of Liquid Organic Hydrides: Insights into Structural Features and Relationship with Catalytic Activity

“…There are no Cu 2+ species, because these are characterized by a higher Cu 2p 3/2 binding energy. Moreover, the Cu 2p spectrum of a Cu(II)-based compound contains intense shake up satellites [ 58 ]. To distinguish Cu 1+ from Cu 0 , it is necessary to use the Auger parameter, which is equal to the sum of the Cu 2p 3/2 binding energy and the position of the maximum of the Cu LMM Auger peak on the scale of the kinetic energies of electrons.…”

“…To distinguish Cu 1+ from Cu 0 , it is necessary to use the Auger parameter, which is equal to the sum of the Cu 2p 3/2 binding energy and the position of the maximum of the Cu LMM Auger peak on the scale of the kinetic energies of electrons. According to the literature data, the Auger parameters of metallic copper, Cu 2 O, and CuO are 1851.0–1851.4, 1848.7–1849.3, and 1851.4–1851.7 eV, respectively [ 58 , 59 ]. In our case, the Auger parameter is in the range of 1850.9–1851.3 eV for all of the reduced catalysts, which strongly indicates that copper is mainly in the metallic state.…”