The CO–H2 and CO–H2O reactions over TiO2 nanotubes filled with Pt metal nanoparticles

We have investigated the catalytic behavior of Pt encapsulated TiO₂ nanotubes for the water gas shift reaction as well as the hydrogenation of CO. Pt–TiO₂ nanotube catalysts were prepared by employing fine fiber shaped crystals of [Pt(NH₃)₄](HCO₃)₂ complex as a structure determining template material. The turnover frequencies (TOF) of these nanotube catalysts were more than one order of magnitude larger than conventional impregnation Pt/TiO₂ catalysts, and the selectivity for methanol in CO–H₂ reaction was extraordinary high compared to the impregnation catalysts. The XPS and XRD analyses of the nanotubes revealed characteristic electronic state of reduced TiO₂ (Ti³⁺ in rutile structure) with zerovalent Pt even after the calcination at 773 K. In WGS reaction, electron rich Ti³⁺ on the nanotube wall may play an important role to activate water molecules for the oxidation of CO. In CO–H₂ reaction, similar promotion effect of Ti³⁺ species may be operating for selective methanol formation by supplying active OH(a).     

Preparation and characterization of LaFe1−xMgxO3/Al2O3/FeCrAl: Catalytic properties in methane combustion

MnO_x–CeO₂ mixed oxides prepared by sol–gel method, coprecipitation method and modified coprecipitation method were investigated for the complete oxidation of formaldehyde. Structure analysis by H₂-TPR and XPS revealed that there were more Mn⁴⁺ species and richer lattice oxygen on the surface of the catalyst prepared by the modified coprecipitation method than those of the catalysts prepared by sol–gel and coprecipitation methods, resulting in much higher catalytic activity toward complete oxidation of formaldehyde. The effect of calcination temperature on the structural features and catalytic behavior of the MnO_x–CeO₂ mixed oxides prepared by the modified coprecipitation was further examined, and the catalyst calcined at 773 K showed 100% formaldehyde conversion at a temperature as low as 373 K. For the samples calcined below 773 K, no any diffraction peak corresponding to manganese oxides could be detected by XRD measurement due to the formation of MnO_x–CeO₂ solid solution. While the diffraction peaks corresponding to MnO₂ phase in the samples calcined above 773 K were clearly observed, indicating the occurrence of phase segregation between MnO₂ and CeO₂. Accordingly, it was supposed that the strong interaction between MnO_x and CeO₂, which depends on the preparation route and the calcination temperature, played a crucial role in determining the catalytic activity toward the complete oxidation of formaldehyde.     

Copper-impregnated Al–Ce-pillared clay for selective catalytic reduction of NO by C3H6

The selective catalytic reduction (SCR) of NO by hydrocarbon is an efficient way to remove NO emission from lean-burn gasoline and diesel exhaust. In this paper, a thermally and hydrothermally stable Al–Ce-pillared clay (Al–Ce-PILC) was synthesized and then modified by SO₄²⁻, whose surface area and average pore diameter calcined at 773 K were 161 m²/g and 12.15 nm, respectively. Copper-impregnated Al–Ce-pillared clay catalyst (Cu/SO₄²⁻/Al–Ce-PILC) was applied for the SCR of NO by C₃H₆ in the presence of oxygen. The catalyst 2 wt% Cu/SO₄²⁻/Al–Ce-PILC showed good performance over a broad range of temperature, its maximum conversion of NO was 56% at 623 K and remained as high as 22% at 973 K. Furthermore, the presence of 10% water slightly decreased its activity, and this effect was reversible following the removal of water from the feed. Py-IR results showed SO₄²⁻ modification greatly enhanced the number and strength of Brönsted acidity on the surface of Cu/SO₄²⁻/Al–Ce-PILC, which played a vital role in the improvement of NO conversion. TPR and XPS results indicated that both Cu⁺ and isolated Cu²⁺ species existed on the optimal catalyst, mainly Cu⁺, as Cu content increased to 5 wt%, another species CuO aggregates which facilitated the combustion of C₃H₆ were formed.     

Preparation, characterization and catalytic properties of Co–Nb2O5–SiO2 catalysts

Co–Nb₂O₅–SiO₂ catalysts were prepared using three different sol–gel procedures: (i) the colloidal sol–gel method using NbCl₅ and SiCl₄ as precursors; (ii) the polymeric sol–gel method using niobium ethoxide and tetraethyl-orthosilicate (TEOS); (iii) an intermediate procedure between the colloidal and polymeric sol–gel method in which the precursors were those utilized in the CSG but dissolved in a mixture of anhydrous ethanol and CCl₄. In all procedures, the elimination of the solvent carried out between 80 and 110°C was followed by a reduction in hydrogen flow (30 ml min⁻¹) at 773 K. Following these procedures, samples containing 10 wt.% Co and 15 wt.% niobium oxide (expressed as Nb₂O₅) were obtained. The characterization of the catalysts was performed using various techniques: N₂ adsorption and desorption curves at 77 K, NH₃- and H₂-chemisorption, TPO, XPS, XRD, and solid state ¹H MAS-NMR. Hydrogenolysis of butane was evaluated. The low reaction rates are assigned to the effect of the metal size, whereas the isobutane selectivity as well as the relatively high stability is due to the acidity of the support.     

Electrode reaction of the Np3+/Np couple at liquid Cd and Bi electrodes in LiCl–KCl eutectic melts

The electrode reactions of the Np³⁺/Np couple at liquid Cd and Bi electrodes were investigated by cyclic voltammetry at 723, 773 and 823 K in the LiCl–KCl eutectic melt. It was found that the diffusion of Np³⁺ in the salt phase was the rate-determining step in the cathodic reaction when the concentration of NpCl₃ was less than about 1 wt % and the liquid Cd or Bi phase was not saturated with Np. The redox potentials of the Np³⁺/Np couple at the liquid Cd electrode at 723, 773 and 823 K were observed to be more positive than those at the Mo electrode by 0.158, 0.140 and 0.126 V, respectively. The potential shift results from a lowering of the activity of Np in the Cd phase according to the formation of the NpCd₁₁ alloy at 723 K and NpCd₆ at 773 and 823 K. The redox potentials of the Np³⁺/Np couple at the liquid Bi electrode at 723, 773 and 823 K were more positive than those at the Mo electrode by 0.427, 0.419 and 0.410 V, respectively, which is attributable to a lowering of the activity of Np in the Bi phase due to the formation of NpBi₂.     

Comparative study of Au/ZrO2 catalysts in CO oxidation and 1,3-butadiene hydrogenation

This work investigates the effects of Au³⁺/Au⁰ ratio or distribution of gold oxidation states in Au/ZrO₂ catalysts of different gold loadings (0.01–0.76% Au) on CO oxidation and 1,3-butadiene hydrogenation by regulating the temperature of catalyst calcination (393–673 K) and pre-reduction with hydrogen (473–523 K). The catalysts were prepared by deposition–precipitation and were characterized with elemental analysis, nitrogen adsorption/desorption, TEM, XPS and TPR. The catalytic data showed that the exposed metallic Au⁰ atoms at the surface of Au particles were not the only catalytic sites for the two reactions, isolated Au³⁺ ions at the surface of ZrO₂, such as those in the catalysts containing no more than 0.08% Au were more active by TOF. For 0.76% Au/ZrO₂ catalysts having coexisting Au³⁺ and Au⁰, the catalytic activity changed differently with varying the Au³⁺/Au⁰ ratio in the two reactions. The highest activity for the CO oxidation reaction was observed over the catalyst of Au³⁺/Au⁰ = 0.33. However, catalyst with a higher Au³⁺/Au⁰ ratio showed always a higher activity for the hydrogenation reaction; co-existance of Au⁰ with Au³⁺ ions lowered the catalyst activity. Moreover, the coexisting Au particles changed the product selectivity of 1,3-butadiene hydrogenation to favor the formation of more trans-2-butene and butane. It is thus suggested that for better control of the catalytic performance of Au catalyst the effect of Au³⁺/Au⁰ ratio on catalytic reactions should be investigated in combination with the particle size effect of Au.     

Support effects in Pt/TiO2–ZrO2 catalysts for NO reduction with CH4

ZrO₂–TiO₂ mixed oxides, prepared using the sol–gel method, were used as supports for platinum catalysts. The effects of catalyst pre-reduction and surface acidity on the performance of Pt/ZT catalysts for the reduction of NO with CH₄ were studied. The diffuse reflectance infrared Fourier transformed (DRIFT) spectra of CO adsorbed on the Pt/ZT catalysts, and also on the Pt/T and Pt/Z references, pre-reduced at 773 K in hydrogen, revealed that an SMSI state is developed in the Ti-rich oxide-supported platinum catalysts. However, no shift in the binding energy of Pt 4f_7/2 level for Pt/T and Pt deposited on Ti-rich support counterparts pre-reduced at 773 K was found by photoelectron spectroscopy. The DRIFT spectra of the catalysts under the NO+O₂ co-adsorption revealed the appearance of nitrite/nitrate species on the surface of the Zr-containing catalysts, which displayed acidic properties, but were almost absent in the Pt/T catalyst. The intensity of these bands reached a maximum for the Pt/ZT(1:1) catalyst, which in turn exhibited a larger specific area. In the absence of oxygen in the feed stream, the NO+CH₄ reaction showed DRIFT spectra assigned to surface isocyano species. Since the intensity of this band is higher for the Pt/ZT (9:1) catalyst, it seems that such species are developed at the Pt–support interface.     

The red–ox treatments influence on the structure and properties of M2O3–CeO2–ZrO2 (M=Y, La) solid solutions

The introduction of trivalent cation — Y³⁺ or La³⁺ — into the lattice of CeO₂–ZrO₂ solid solutions allows to stabilise a cubic structure at low ceria content (30 mol%). The reducibility of the samples has been compared in the experiments of temperature-programmed reduction (TPR). The introduction of lanthanum cations decreases the amount of hydrogen consumed during TPR, while the introduction of yttrium ones increases this value. At the same time, the value of temperature of the maximum speed of reduction (T_max) is independent on the trivalent dopant. The reducibility of these solid solutions did not change during repeated red–ox treatments at temperature below 1220 K. It is connected with the high thermostability of all systems in this temperature interval. TPR up to 1470 K causes a significant shift of T_max value to higher temperature and a slight decrease of hydrogen consumption in two to three cycles. It is suggested that this alterations are connected with the sharp decrease of the specific surface area of all samples and partially phase decomposition of CeO₂–ZrO₂ and Y₂O₃–CeO₂–ZrO₂ solid solutions. Raman characterisation of the oxygen sublattice of the fresh samples and of the samples after TPR has been carried out.     

Alumina supported Mo–V–Te–O catalysts for the ammoxidation of propane to acrylonitrile

The effect of Te addition over Mo–V–O catalysts supported on alumina is discussed for the ammoxidation of propane to acrylonitrile. Catalyst composition and atmosphere of activation are evaluated. Catalysts are characterized before and after catalytic reaction by XPS, XRD and in situ Raman spectroscopies. The absence of Te in catalysts formulation and the presence of a high amount of vanadium induce the presence of V⁵⁺ species and the formation of V₂O₅ oxide; associated with a decrease in acrylonitrile selectivity. The presence of Mo-based polyacids structures decreases the selectivity to acrylonitrile. V⁵⁺ sites are responsible of propane activation and of the subsequent -H abstraction to form the intermediate propylene. Then, a Mo–V rutile-like structure in which vanadium species are reduced as V⁴⁺, is responsible for nitrogen insertion and acrylonitrile formation. The formation of such structure is favoured when Te is added to catalysts and is promoted during propane ammoxidation.     

Rich photoluminescence emission of SnO2–SiO2 composite aerogels prepared with a co-fed precursor sol–gel process

Tin oxide–silica composite aerogels were successfully prepared with a co-fed precursor sol–gel process. The crystallinity of the tin oxide nanoparticles, embedded in the mesoporous SiO₂ network, was improved with increasing the post-reaction thermal treatment temperature. The composite aerogels exhibited a rich photoluminescence (PL) emission contributed by both SnO₂ and SiO₂. The PL peak of 346 nm was from the near band edge emission of the tin oxide nanoparticles, and the ones located at 310 and 476 nm were attributable to the oxygen deficiencies of the silica network. Three more emission peaks, 387, 432, and 522 nm, were observed, with the 387 nm peak contributed by the oxygen vacancies V_O⁺⁺, the 432 nm peak by the Sn interstitials, and the 522 nm peak by the oxygen vacancies V_O⁺, respectively, of the tin oxide nanoparticles. The intensities of these three defect level emissions were found decreased, as compared to that of the near band edge emission, with increasing the post-reaction thermal treatment temperature as the tin oxide crystallinity improved.     

Preparation and characterization of mesoporous γ-Ga2O3

Mesoporous γ-Ga₂O₃ was prepared by calcination (at 773 K) of a gallia gel obtained by adding ammonia to an ethanolic solution of gallium nitrate. The corresponding powder X-ray diffraction pattern was found to be similar to that of γ-alumina; all diffraction lines could be indexed by assuming a cubic spinel-type structure having a lattice parameter a₀=0.830 nm. Nitrogen adsorption–desorption at 77 K showed the material to have a BET surface area of 120 m² g⁻¹ and a most frequent pore radius of 2.1 nm. The surface chemistry was studied by FTIR spectroscopy of adsorbed carbon monoxide at liquid nitrogen temperature. Partially hydroxylated γ-Ga₂O₃ gave main O–H stretching bands at 3692 and 3637 cm⁻¹. These hydroxyl bands were significantly perturbed by adsorbed CO, thus showing a Brønsted acid character. Lewis acidity was monitored by analyzing the C–O stretching mode of carbon monoxide adsorbed on coordinatively unsaturated Ga³⁺ ions; main IR absorption bands of Ga³⁺CO adducts were found at 2220 and 2193 cm⁻¹.     

Catalytic combustion of methane over microemulsion-derived MnOx–Cs2O–Al2O3 nanocomposites

Mesostructured MnO_x–Cs₂O–Al₂O₃ nanocomposites have been synthesized by reverse microemulsion method combined with hydrothermal treatment and then applied to the catalytic combustion of methane. Compared to impregnation-derived conventional MnO_x/Cs₂O/Com-Al₂O₃ catalyst, the microemulsion-derived catalyst showed higher activity and stability for methane combustion. The T_10% of the fresh and of the 72 h aged Mn_xO–Cs₂O–Al₂O₃ were 475 and 490 °C, respectively, recommending it as a potential candidate catalyst for application in hybrid gas turbines. The homogeneous composition of the microemulsion-derived nanocomposite catalyst can hinder the loss of Cs⁺ and accelerate the formation of Cs–β-alumina phase, ensuring thus higher activity and stability for methane combustion.     

Kinetic studies of CH4 oxidation over Pt–NiO/δ-Al2O3 in a fluidised bed reactor

The oxidation of CH₄ over Pt–NiO/δ-Al₂O₃ has been studied in a fluidised bed reactor as part of a major project on an autothermal (combined oxidation–steam reforming) system for CH₄ conversion. The kinetic data were collected between 773 and 893 K and 101 kPa total pressure using CH₄ and O₂ compositions of 10–35% and 8–30%, respectively. Rate–temperature data were also obtained over alumina-supported monometallic catalysts, Pt and NiO. The bimetallic Pt–NiO system has a lower activation energy (80.8 kJ mol⁻¹) than either Pt (86.45 kJ mol⁻¹) and NiO (103.73 kJ mol⁻¹). The superior performance of the bimetallic catalyst was attributed to chemical synergy. The reaction rate over the Pt–NiO catalyst increased monotonically with CH₄ partial pressure but was inhibited by O₂. At low partial pressures (<30 kPa), H₂O has a detrimental effect on CH₄ conversion, whilst above 30 kPa, the rate increased dramatically with water content.     

CH4/CO2 reforming over La2NiO4 and 10%NiO/CeO2–La2O3 catalysts under the condition of supersonic jet expansion via cavity ring-down spectroscopic analysis

CH₄/CO₂ reforming over La₂NiO₄ and 10%NiO/CeO₂–La₂O₃ catalysts under the condition of supersonic jet expansion was studied via direct monitoring of the reactants and products using the sensitive technique of cavity ring-down spectroscopy. Vibration–rotational absorption lines of CH₄, H₂O, CO₂ and CO molecules were recorded in the near infrared spectral region. Our results indicated that La₂NiO₄ is superior to 10%NiO/CeO₂–La₂O₃ in performance. In addition, we observed enhanced reverse-water-gas-shift reaction at augmented reaction temperature. The formation of reaction intermediates was also investigated by means of time-of-flight mass spectrometry and there was the detection of CH_x⁺, OH⁺ and H⁺ species.     

Isomerization of n-hexane over mono- and bimetallic Pd–Pt catalysts supported on ZrO2–Al2O3–WOx prepared by sol–gel

The catalytic performance of mono- and bimetallic Pd (0.6, 1.0 wt.%)–Pt (0.3 wt.%) catalysts supported on ZrO₂ (70, 85 wt.%)–Al₂O₃ (15, 0 wt.%)–WO_x (15 wt.%) prepared by sol–gel was studied in the hydroisomerization of n-hexane. The catalysts were characterized by N₂ physisorption, XRD, TPR, XPS, Raman, NMR, and FT-IR of adsorbed pyridine. The preparation of ZrW and ZrAlW mixed oxides by sol–gel favored the high dispersion of WO_x and the stabilization of zirconia in the tetragonal phase. The Al incorporation avoided the formation of monoclinic-WO₃ bulk phase. The catalysts increased their S_BET for about 15% promoted by Al₂O₃ addition. Various oxidation states of WO_x species coexist on the surface of the catalysts after calcination. The structure of the highly dispersed surface WO_x species is constituted mainly of isolated monotungstate and two-dimensional mono-oxotungstate species in tetrahedral coordination. The activity of Pd/ZrW catalysts in the hydroisomerization of n-hexane is promoted both with the addition of Al to the ZrW mixed oxide and the addition of Pt to Pd/ZrAlW catalysts. The improvement in the activity of Pd/ZrAlW catalysts is ascribed to a moderated acid strength and acidity, which can be correlated to the coexistence of W⁶⁺ and reduced-state WO_x species (either W⁴⁺ or W⁰). The addition of Pt to the Pd/ZrAlW catalyst does not modify significantly its acidic character. Selectivity results showed that the catalyst produced 2MP, 3MP and the high octane 2,3-dimethylbutane (2,3-DMB) and 2,2-dimethylbutane (2,2-DMB) isomers.     

Production of hydrogen via partial oxidation of methanol over Au/TiO2 catalysts

Selective production of hydrogen by partial oxidation of methanol (CH₃OH + (1/2)O₂ → 2H₂ + CO₂) over Au/TiO₂ catalysts, prepared by a deposition–precipitation method, was studied. The catalysts were characterized by XRD, TEM, and XPS analyses. TEM observations show that the Au/TiO₂ catalysts exhibit hemispherical gold particles, which are strongly attached to the metal oxide support at their flat planes. The size of the gold particles decreases from 3.5 to 1.9 nm during preparation of the catalysts with the rise in pH from 6 to 9 and increases from 2.9 to 4.3 nm with the rise in calcination temperature up to 673 K. XPS analyses demonstrate that in uncalcined catalysts gold existed in three different states: i.e., metallic gold (Au⁰), non-metallic gold (Au^δ+) and Au₂O₃, and in catalysts calcined at 573 K only in metallic state. The catalytic activity is strongly dependent on the gold particle size. The catalyst precipitated at pH 8 and uncalcined catalysts show the highest activity for hydrogen generation. The partial pressure of oxygen plays an important role in determining the product distribution. There is no carbon monoxide detected when the O₂/CH₃OH molar ratio in the feed is 0.3. Both hydrogen selectivity and methanol conversion increase with increasing the reaction temperature. The reaction pathway is suggested to consist of consecutive methanol combustion, partial oxidation and steam reforming.     

The role of oxygen vacancies during the decomposition of RhCl3/TiO2 precursor: study by XPS, IR, EPR and NMR.

Thermal reduction under ultrahigh vacuum or with H₂ of RhCl₃/TiO₂ precursors up to 773K has been studied either directly or after precalcination with O₂ at 773K. The evolution of rhodium and chlorine has been followed with the aid of XPS, EPR, IR ¹H-NMR and TPR/DTG for the different treatments. Ar⁺ sputtering has been used in combination with XPS to examine in detail the incorporation of chlorine to the TiO₂ support. A model is proposed which assumes the formation during the reduction process of oxygen vacancies (Vo) associated to Ti³⁺ species (i.e. (TiVo)_n³ⁿ⁺). These centers act promoting the reduction of Rh³⁺ to Rh^o and upon extensive reduction at 773K in H₂, as anchoring sites of Rh^o through interaction with exposed Ti³⁺ ions. Oxygen vacancies sites are also able to incorporate chlorine and hydrogen to form in the later case hydride, (Ti-H)³⁺, species that we have previously found to have a role in the SMSI state.     

Local structure and photocatalytic activity of B2O3–SiO2/TiO2 ternary mixed oxides prepared by sol–gel method

The local structure and the photoactivity of B₂O₃–SiO₂/TiO₂ ternary mixed oxides (SiO₂ content was fixed as 30 at.% with respect to TiO₂) was investigated by using XRD, FT-IR, BET, UV-vis spectra, and electron paramagnetic resonance (EPR) measurement. In FT-IR analysis, boron was incorporated into the framework of titania matrix with replacing Ti---O---Si with Si---O---B or Ti---O---B bonds. Also, paramagnetic species such as O⁻ and Ti³⁺ defects were formed by the boron incorporation. In SiO₂/TiO₂ mixed oxides, a blue shift in the light absorption band was observed due to the quantization of band structure. All B₂O₃–SiO₂/TiO₂ samples had pure anatase phase and no rutile phase was formed even though the calcination temperature was over 900 °C. Incorporating boron oxides of more than 10% enlarges the grain size of anatase phase and causes a red shift of the light absorption spectrum. The surface area was monotonically decreased with increasing the content of boron content. As a result, the photoactivity of B₂O₃–SiO₂/TiO₂ ternary mixed oxides was greatly influenced by the content of boron oxide. The highest photoactivity (g moles/min l) was obtained when the boron content was 5% and seven times higher than that of silica/titania binary mixed oxide. In addition, the specific photoactivity (g moles/m² l) was maximum still at 5%. It was concluded that the large reduction of surface area, the change of band structure, and more formation of bulk Ti³⁺ sites are responsible for the deterioration in the photoactivity of B₂O₃–SiO₂/TiO₂ ternary mixed oxides when the content of boron is over 10%, although their crystallinity was enhanced by increasing the calcination temperature with keeping anatase phase.     

Pitting corrosion of Al and Al–Cu alloys by ClO4 ions in neutral sulphate solutions

The influence of various concentrations of NaClO₄, as a pitting corrosion agent, on the corrosion behaviour of pure Al, and two Al–Cu alloys, namely (Al + 2.5 wt% Cu) and (Al + 7 wt% Cu) alloys in 1.0 M Na₂SO₄ solution was investigated by potentiodynamic polarization and potentiostatic techniques at 25 °C. Measurements were conducted under the influence of various experimental conditions, complemented by ex situ energy dispersive X-ray (EDX) and scanning electron microscopy (SEM) examinations of the electrode surface. In free perchlorate sulphate solutions, for the three Al samples, the anodic polarization exhibits an active/passive transition. The active dissolution region involves an anodic peak (peak A) which is assigned to the formation of Al₂O₃ passive film on the electrode surface. The passive region extends up to 1500 mV with almost constant current density (j_pass) without exhibiting a critical breakdown potential or showing any evidence of pitting attack. For the three Al samples, addition of ClO₄⁻ ions to the sulphate solution stimulates their active anodic dissolution and tends to induce pitting corrosion within the oxide passive region. Pitting corrosion was confirmed by SEM examination of the electrode surface. The pitting potential decreases with increasing ClO₄⁻ ion concentration indicating a decrease in pitting corrosion resistance. The susceptibility of the three Al samples towards pitting corrosion decreases in the order: Al > (Al + 2.5 wt% Cu) alloy > (Al + 7 wt% Cu) alloy. Potentiostatic measurements showed that the rate of pitting initiation increases with increasing ClO₄⁻ ion concentration and applied step anodic potential, while it decreases with increasing %Cu in the Al samples. The inhibitive effect of SO₄²⁻ ions was also discussed.     

NO decomposition and reduction by CH4 over Sr/La2O3

Both NO decomposition and NO reduction by CH₄ over 4%Sr/La₂O₃ in the absence and presence of O₂ were examined between 773 and 973 K, and N₂O decomposition was also studied. The presence of CH₄ greatly increased the conversion of NO to N₂ and this activity was further enhanced by co-fed O₂. For example, at 773 K and 15 Torr NO the specific activities of NO decomposition, reduction by CH₄ in the absence of O₂, and reduction with 1% O₂ in the feed were 8.3·10⁻⁴, 4.6·10⁻³, and 1.3·10⁻² μmol N₂/s m², respectively. This oxygen-enhanced activity for NO reduction is attributed to the formation of methyl (and/or methylene) species on the oxide surface. NO decomposition on this catalyst occurred with an activation energy of 28 kcal/mol and the reaction order at 923 K with respect to NO was 1.1. The rate of N₂ formation by decomposition was inhibited by O₂ in the feed even though the reaction order in NO remained the same. The rate of NO reduction by CH₄ continuously increased with temperature to 973 K with no bend-over in either the absence or the presence of O₂ with equal activation energies of 26 kcal/mol. The addition of O₂ increased the reaction order in CH₄ at 923 K from 0.19 to 0.87, while it decreased the reaction order in NO from 0.73 to 0.55. The reaction order in O₂ was 0.26 up to 0.5% O₂ during which time the CH₄ concentration was not decreased significantly. N₂O decomposition occurs rapidly on this catalyst with a specific activity of 1.6·10⁻⁴ μmol N₂/s m² at 623 K and 1220 ppm N₂O and an activation energy of 24 kcal/mol. The addition of CH₄ inhibits this decomposition reaction. Finally, the use of either CO or H₂ as the reductant (no O₂) produced specific activities at 773 K that were almost 5 times greater than that with CH₄ and gave activation energies of 21–26 kcal/mol, thus demonstrating the potential of using CO/H₂ to reduce NO to N₂ over these REO catalysts.