Performance and characterization of Ru/Al2O3 and Ru/SiO2 catalysts modified with Mn for Fischer–Tropsch synthesis

Mn effect and characterization on γ-Al₂O₃-, -Al₂O₃- and SiO₂-supported Ru catalysts were investigated for Fischer–Tropsch synthesis under pressurized conditions. In the slurry phase Fischer–Tropsch reaction, γ-Al₂O₃ catalysts showed higher performance on CO conversion and C₅⁺ selectivity than -Al₂O₃ and SiO₂ catalysts. Moreover, Ru/Mn/γ-Al₂O₃ exhibited high resistance to catalyst deactivation and other catalysts were deactivated during the reaction. From characterization results on XRD, TPR, TEM, XPS and pore distribution, Ru particles were clearly observed over the catalysts, and γ-Al₂O₃ catalysts showed a moderate pore and particle size such as 8 nm, where -Al₂O₃ and SiO₂ showed highly dispersed ruthenium particles. The addition of Mn to γ-Al₂O₃ enhanced the removal of chloride from RuCl₃, which can lead to the formation of metallic Ru with moderate particle size, which would be an active site for Fischer–Tropsch reaction. Concomitantly, manganese chloride is formed. These schemes can be assigned to the stable nature of Ru/Mn/γ-Al₂O₃ catalyst.     

Mesoporous molecular sieve MCM-41 supported Co–Mo catalyst for hydrodesulfurization of petroleum resids

In this work, we explored the potential of mesoporous zeolite-supported Co–Mo catalyst for hydrodesulfurization of petroleum resids, atmospheric and vacuum resids at 350–450°C under 6.9 MPa of H₂ pressure. A mesoporous molecular sieve of MCM-41 type was synthesized; which has SiO₂/Al₂O₃ ratio of about 41. MCM-41 supported Co–Mo catalyst was prepared by co-impregnation of Co(NO₃)₂·6H₂O and (NH₄)₆Mo₇O₂₄ followed by calcination and sulfidation. Commercial Al₂O₃ supported Co–Mo (criterion 344TL) and dispersed ammonium tetrathiomolybdate (ATTM) were also tested for comparison purposes. The results indicated that Co–Mo/MCM-41(H) is active for HDS, but is not as good as commercial Co–Mo/Al₂O₃ for desulfurization of petroleum resids. It appears that the pore size of the synthesized MCM-41 (28 Å) is not large enough to convert large-sized molecules such as asphaltene present in the petroleum resids. Removing asphaltene from the resid prior to HDS has been found to improve the catalytic activity of Co–Mo/MCM-41(H). The use of ATTM is not as effective as that of Co–Mo catalysts, but is better for conversions of >540°C fraction as compared to noncatalytic runs at 400–450°C.     

NO reduction by CH4 in the presence of O2 over La2O3 supported on Al2O3

Dispersing La₂O₃ on δ- or γ-Al₂O₃ significantly enhances the rate of NO reduction by CH₄ in 1% O₂, compared to unsupported La₂O₃. Typically, no bend-over in activity occurs between 500° and 700°C, and the rate at 700°C is 60% higher than that with a Co/ZSM-5 catalyst. The final activity was dependent upon the La₂O₃ precursor used, the pretreatment, and the La₂O₃ loading. The most active family of catalysts consisted of La₂O₃ on γ-Al₂O₃ prepared with lanthanum acetate and calcined at 750°C for 10 h. A maximum in rate (mol/s/g) and specific activity (mol/s/m²) occurred between the addition of one and two theoretical monolayers of La₂O₃ on the γ-Al₂O₃ surface. The best catalyst, 40% La₂O₃/γ-Al₂O₃, had a turnover frequency at 700°C of 0.05 s⁻¹, based on NO chemisorption at 25°C, which was 15 times higher than that for Co/ZSM-5. These La₂O₃/Al₂O₃ catalysts exhibited stable activity under high conversion conditions as well as high CH₄ selectivity (CH₄ + NO vs. CH₄ + O₂). The addition of Sr to a 20% La₂O₃/γ-Al₂O₃ sample increased activity, and a maximum rate enhancement of 45% was obtained at a SrO loading of 5%. In contrast, addition of SO⁼₄ to the latter Sr-promoted La₂O₃/Al₂O₃ catalyst decreased activity although sulfate increased the activity of Sr-promoted La₂O₃. Dispersing La₂O₃ on SiO₂ produced catalysts with extremely low specific activities, and rates were even lower than with pure La₂O₃. This is presumably due to water sensitivity and silicate formation. The La₂O₃/Al₂O₃ catalysts are anticipated to show sufficient hydrothermal stability to allow their use in certain high-temperature applications.     

Mechanistic study of partial oxidation of methane to synthesis gas over supported rhodium and ruthenium catalysts using in situ time-resolved FTIR spectroscopy

In situ time-resolved FTIR spectroscopy was used to study the reaction mechanism of partial oxidation of methane to synthesis gas and the interaction of CH₄/O₂/He (2/1/45) gas mixture with adsorbed CO species over SiO₂ and γ-Al₂O₃ supported Rh and Ru catalysts at 500–600°C. It was found that CO is the primary product for the reaction of CH₄/O₂/He (2/1/45) gas mixture over H₂ reduced and working state Rh/SiO₂ catalyst. Direct oxidation of methane is the main pathway of synthesis gas formation over Rh/SiO₂ catalyst. CO₂ is the primary product for the reaction of CH₄/O₂/He (2/1/45) gas mixture over Ru/γ-Al₂O₃ and Ru/SiO₂ catalysts. The dominant reaction pathway of CO formation over Ru/γ-Al₂O₃ and Ru/SiO₂ catalysts is via the reforming reactions of CH₄ with CO₂ and H₂O. The effect of space velocity on the partial oxidation of methane over SiO₂ and γ-Al₂O₃ supported Rh and Ru catalysts is consistent with the above mechanisms. It is also found that consecutive oxidation of surface CO species is an important pathway of CO₂ formation during the partial oxidation of methane to synthesis gas over Rh/SiO₂ and Ru/γ-Al₂O₃ catalysts.     

Preparation of new solid superacid catalyst, zirconium sulfate supported on γ-alumina and activity for acid catalysis

Zirconium sulfate supported on γ-Al₂O₃ catalysts were prepared by impregnation of powdered γ-Al₂O₃ with zirconium sulfate aqueous solution followed by calcining in air at high temperature. For Zr(SO₄)₂/γ-Al₂O₃ samples, no diffraction line of zirconium sulfate was observed up to 50 wt.%, indicating good dispersion of Zr(SO₄)₂ on the surface of γ-Al₂O₃. The acidity of catalysts increased in proportion to the zirconium sulfate content up to 40 wt.% of Zr(SO₄)₂. 40-Zr(SO₄)₂/γ-Al₂O₃ calcined at 400 °C exhibited maximum catalytic activities for 2-propanol dehydration and cumene dealkylation. The catalytic activities for both reactions, 2-propanol dehydration and cumene dealkylation were correlated with the acidity of catalysts measured by ammonia chemisorption method.     

Fischer–Tropsch synthesis on monolithic catalysts of different materials

Monolithic structures made of cordierite, γ-Al₂O₃ and steel have been prepared as catalysts and tested for Fischer–Tropsch activity. The monoliths made of cordierite and steel were washcoated with a 20 wt.% Co–1 wt.% Re/γ-Al₂O₃ Fischer–Tropsch catalyst whereas the γ-Al₂O₃ monoliths were made by direct impregnation with an aqueous solution of the Co and Re salts resulting in a loading of 12 wt.% Co and 0.5 wt.% Re. The activity and selectivity of the different monoliths were compared with the corresponding powder catalysts.

Higher washcoat loadings resulted in decreased C₅₊ selectivity and olefin/paraffin ratios due to increased transport limitations. The impregnated γ-Al₂O₃ monoliths also showed similar C₅₊ selectivities as powder catalysts of small particle size (38–53 μm). Lower activities were observed with the steel monoliths probably due to experimental problems.     

Monodispersed gold nanoparticles supported on γ-Al2O3 for enhancement of low-temperature catalytic oxidation of CO

Monodispersed nano-Au/γ-Al₂O₃ catalysts for low-temperature oxidation of CO have been prepared via a modified colloidal deposition route, which involves the deposition of dodecanethiolate self-assembled monolayer (SAM)-protected gold nanoparticles (C₁₂ nano-Au) in hexane on γ-Al₂O₃ at room temperature. The diameter of the gold nanoparticles deposited on the support is 2.5 ± 0.8 nm after thermal treatment, and their valence states comprise both the metallic and oxidized states. It is found that the thermal treatment temperature affects significantly the catalytic activity of the catalysts in the processing steps. The catalyst treated at 190 °C exhibits considerably higher activity as compared to catalysts treated at 165 and 250 °C. A 2.0-wt.% nano-Au/γ-Al₂O₃ catalyst treated at 190 °C for 15 h maintains the catalytic activity at nearly 100% CO oxidation for at least 800 h at 15 °C, at least 600 h at 0 °C, and even longer than 450 h at −5 °C. Evidently, the catalysts obtained using this preparation route show high catalytic activity, particularly at low temperatures, and a good long-term stability.     

Oxidative dehydrogenation of propane over differently structured vanadia-based catalysts in the presence of O2 and N2O

The effect of the nature and distribution of VO_x species over amorphous and well-ordered (MCM-41) SiO₂ as well as over γ-Al₂O₃ on their performance in the oxidative dehydrogenation of propane with O₂ and N₂O was studied using in situ UV–vis, ex situ XRD and H₂-TPR analysis in combination with steady-state catalytic tests. As compared to the alumina support, differently structured SiO₂ supports stabilise highly dispersed surface VO_x species at higher vanadium loading. These species are more selective over the latter materials than over V/γ-Al₂O₃ catalysts. This finding was explained by the difference in acidic properties of silica- and alumina-based supports. C₃H₆ selectivity over V/γ-Al₂O₃ materials is improved by covering the support fully with well-dispersed VO_x species. Additionally, C₃H₆ selectivity over all materials studied can be tuned by using an alternative oxidising agent (N₂O). The improving effect of N₂O on C₃H₆ selectivity is related to the lower ability of N₂O for catalyst reoxidation resulting in an increase in the degree of catalyst reduction, i.e. spatial separation of active lattice oxygen in surface VO_x species. Such separation favours selective oxidation over CO_x formation.     

Origin of transient species present on the surface of a PdO/γ-Al2O3 catalyst during the methane combustion reaction

Operando DRIFTS was applied to the study of the evolution of surface species formed on a Pd (2 wt.%)/γ-Al₂O₃ catalyst in various conditions. No differences were observed as a function of the initial oxidation state of palladium. Formates/carbonates species were identified at low temperature (<400 °C) and disappeared when CO₂ production started. These species come from the Pd-catalyzed interaction of CO with the alumina support, while CO₂ induces hydrogenocarbonates formation at low temperature (<300 °C). Their presence does not explain the inhibiting effect of CO₂ observed in CCM on Pd/γ-Al₂O₃ catalysts.     

Catalytic combustion of methane in non-permselective membrane reactors with separate reactant feeds

Catalytic combustion of methane over Pd and Pt/SiO₂/-Al₂O₃ membranes was studied in the temperature range 300–650 °C. Fuel and oxygen were fed at opposite membrane sides. In order to improve reactor controllability the -Al₂O₃ membranes were impregnated with SiO₂ sol resulting to smaller pore size. Methane conversions up to 100% for the palladium membrane and up to 42% for the platinum membrane were achieved. The results indicated a transition from kinetic to mass transfer control within the temperature range investigated. This was accompanied by reduction of methane slip from tube to shell side with increasing temperature. CO and H₂ were detected in the product gases of the palladium membrane. Their concentration could be reduced by applying a trans-membrane pressure difference. Low concentrations of CO were observed for the Pt/SiO₂/-Al₂O₃ membrane, while no CO or H₂ were detected for a Pd/-Al₂O₃ membrane operating in dead-end configuration.     

Effect of phosphorus addition on the hydrotreating activity of NiMo/Al2O3 carbide catalyst

A series of phosphorus promoted γ-Al₂O₃ supported NiMo carbide catalysts with 0–4.5 wt.% P, 13 wt.% Mo and 2.5 wt.% Ni were synthesized and characterized by elemental analysis, pulsed CO chemisorption, BET surface area measurement, X-ray diffraction, near-edge X-ray absorption fine structure, DRIFT spectroscopy of CO adsorption and H₂ temperature programmed reduction. X-ray diffraction patterns and CO uptake showed the P addition to NiMo/γ-Al₂O₃ carbide, increased the dispersion of β-Mo₂C particles. DRIFT spectra of adsorbed CO revealed that P addition to NiMo/γ-Al₂O₃ carbide catalyst not only increases the dispersion of Ni-Mo carbide phase, but also changes the nature of surface active sites. The hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) activities of these P promoted NiMo/γ-Al₂O₃ carbide catalysts were performed in trickle bed reactor using light gas oil (LGO) derived from Athabasca bitumen and model feed containing quinoline and dibenzothiophene at industrial conditions. The P added NiMo/γ-Al₂O₃ carbide catalysts showed enhanced HDN activity compared to the NiMo/γ-Al₂O₃ catalysts with both the feed stocks. The P had almost no influence on the HDS activity of NiMo/γ-Al₂O₃ carbide with LGO and dibenzothiophene. P addition to NiMo/γ-Al₂O₃ carbide accelerated CN bond breaking and thus increased the HDN activity.     

Lean reduction of NO by C3H6 over Ag/alumina derived from Al2O3, AlOOH and Al(OH)3

The effectiveness of Ag/Al₂O₃ catalyst depends greatly on the alumina source used for preparation. A series of alumina-supported catalysts derived from AlOOH, Al₂O₃, and Al(OH)₃ was studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible (UV–vis) spectroscopy, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, O₂, NO + O₂-temperature programmed desorption (TPD), H₂-temperature programmed reduction (TPR), thermal gravimetric analysis (TGA) and activity test, with a focus on the correlation between their redox properties and catalytic behavior towards C₃H₆-selective catalytic reduction (SCR) of NO reaction. The best SCR activity along with a moderated C₃H₆ conversion was achieved over Ag/Al₂O₃ (I) employing AlOOH source. The high density of Ag–O–Al species in Ag/Al₂O₃ (I) is deemed to be crucial for NO selective reduction into N₂. By contrast, a high C₃H₆ conversion simultaneously with a moderate N₂ yield was observed over Ag/Al₂O₃ (II) prepared from a γ-Al₂O₃ source. The larger particles of Ag_mO (m > 2) crystallites were believed to facilitate the propene oxidation therefore leading to a scarcity of reductant for SCR of NO. An amorphous Ag/Al₂O₃ (III) was obtained via employing a Al(OH)₃ source and 500 °C calcination exhibiting a poor SCR performance similar to that for Ag-free Al₂O₃ (I). A subsequent calcination of Ag/Al₂O₃ (III) at 800 °C led to the generation of Ag/Al₂O₃ (IV) catalyst yielding a significant enhancement in both N₂ yield and C₃H₆ conversion, which was attributed to the appearance of γ-phase structure and an increase in surface area. Further thermo treatment at 950 °C for the preparation of Ag/Al₂O₃ (V) accelerated the sintering of Ag clusters resulting in a severe unselective combustion, which competes with SCR of NO reaction. In view of the transient studies, the redox properties of the prepared catalysts were investigated showing an oxidation capability of Ag/Al₂O₃ (II and V) > Ag/Al₂O₃ (IV) > Ag/Al₂O₃ (I) > Ag/Al₂O₃ (III) and Al₂O₃ (I). The formation of nitrate species is an important step for the deNO_x process, which can be promoted by increasing O₂ feed concentration as evidenced by NO + O₂-TPD study for Ag/Al₂O₃ (I), achieving a better catalytic performance.     

Tuning the selectivity of MoOx supported catalysts for cyclohexane photo oxidehydrogenation

The photocatalytic properties of sulphated MoO_x/γ-Al₂O₃ catalysts in cyclohexane oxidative dehydrogenation have been determined in a two-dimensional fluidized bed photoreactor and compared to those of sulphated MoO_x/TiO₂ catalysts. Photocatalytic tests on MoO_x/γ-Al₂O₃ at 8 wt% MoO₃ and various sulphate contents showed the selective (100%) formation of cyclohexene, without production of benzene, as instead found with MoO_x/TiO₂. These results show that the selectivity of photocatalytic cyclohexane oxydehydrogenation is dramatically influenced by the catalyst support.

Maximum cyclohexane conversion and cyclohexene yield of 11% were obtained for SO₄ content of 2.6 wt% at 120 °C. Physico-chemical characterisation of catalysts indicates the presence of both octahedral polymolybdate and sulphate species on alumina surface, as previously found for titania. Increasing sulphate load, thermogravimetry evidenced the presence of up to three sulphate species at different thermal stability. The lower activity observed at high sulphate content is likely due to polymolybdate decoration by sulphates.     

Catalytic selective reduction of NO with ethylene over a series of copper catalysts on amorphous silicas

Catalytic selective reduction of NO to N₂ was studied comparing a series of Cu-based catalysts (ca. 8 wt.%) supported over amorphous pure and modified silicas: SiO₂, SiO₂-Al₂O₃, SiO₂-TiO₂, SiO₂-ZrO₂. The catalysts were prepared by the chemisorption-hydrolysis method which ensured the formation of a unique copper phase well dispersed over all supports, as confirmed by scanning electron micrographs (SEMs). Temperature-programmed reduction (TPR) analyses confirmed the presence of dispersed copper species which underwent complete reduction at a temperature of about 220°C, independently of the support. It was found that the support affects the extent of NO reduction as well as the selectivity to N₂ formation. Maximum N₂ yield was found in the range 275–300°C. The catalyst prepared over SiO₂-Al₂O₃ was the most active and selective with respect to the other silicas. Competitiveness factors (c.f.’s) as high as 13–20% in the temperature range 200–250°C could be calculated. For all catalysts, the temperature of the N₂ peak maximum did not correspond to that of the maximum C₂H₄ oxidation to CO₂, suggesting the presence of two different sites for the oxidation and the reduction activity. On the catalyst prepared on SiO₂-Al₂O₃, a kinetic interpretation of catalytic data collected at different contact times and temperatures permitted evaluating the ratio between kinetic coefficients as well as the difference between activation energies of NO reduction by C₂H₄ and C₂H₄ oxidation by O₂.     

The role of the support and dispersion in the catalytic combustion of chlorobenzene on noble metal based catalysts

Polychlorinated benzenes (PhCl_x) are formed as byproducts in the combustion of chlorobenzene on Pt supported on γ-Al₂O₃, SiO₂, SiO₂–Al₂O₃, or ZrO₂. The congener and isomer distribution of the PhCl_x differs for the various supports. The amounts of PhCl_x correlate with the dispersion of platinum. Thus, a Pt/γ-Al₂O₃ catalyst calcined at 500°C to yield very small Pt crystallites was more active in PhCl_x formation than Pt/γ-Al₂O₃ calcined at 800°C. In all cases T_50% for chlorobenzene conversion is close to 300°C and appears to be independent of the crystallite size of the platinum. Replacing platinum by palladium led to lower rates of combustion and to more byproducts. These results lead us to propose that, in the presence of Cl and higher oxygen concentrations, small Pt crystallites are converted more easily into Pt(IV) species. These are less efficient in combustion, but can be more active in chlorination.     

Deactivation studies over NiO/γ-Al2O3 catalysts for partial oxidation of methane to syngas

Two types of NiO/γ-Al₂O₃ catalysts prepared by the impregnation and the sol–gel method were used for the partial oxidation of methane to syngas at 850°C (GHSV1.8×10⁵ lkg⁻¹ h⁻¹). The effects of the carbon deposition, the loss and sintering of nickel and the phase transformation of γ-Al₂O₃ support on the catalytic performance during 80 h POM reaction were investigated with a series of characterization such as XRD, BET, AAS, TG, and XPS. The results indicated that the carbon deposition and the loss and sintering of nickel could not cause the serious decrease of catalytic performance over NiO/γ-Al₂O₃ catalyst during the short-time reaction. However, the slow process of the support γ-Al₂O₃ phase transforming into -Al₂O₃ could slowly decrease the performance of NiO/γ-Al₂O₃ catalysts. Aimed at the reasons of the deactivation, an improved catalyst was obtained by the complexing agent-assisted sol–gel method.     

Size-controlled Pd nanoparticles supported on α-Al2O3 as heterogeneous catalyst for selective hydrogenation of acetylene

Size-controlled Pd nanoparticles （PdNPs） were synthesized in aqueous solution, using sodium car-boxymethyl cellulose as the stabilizer. Size-controlled PdNPs were supported onα-Al2O3 by the incipient wetness impregnation method. The PdNPs onα-Al2O3 support were in a narrow particle size distribution in the range of 1-6 nm. A series of PdNPs/α-Al2O3 catalysts were used for the selective hydrogenation of acetylene in ethylene-rich stream. The results show that PdNPs/α-Al2O3 catalyst with 0.03%（by mass） Pd loading is a very effective and sta-ble catalyst. With promoter Ag added, ethylene selectivity is increased from 41.0%to 63.8%at 100 ＆#176;C. Comparing with conventional Pd-Ag/α-Al2O3 catalyst, PdNPs-Ag/α-Al2O3 catalyst has better catalytic performance in acety-lene hydrogenation and shows good prospects for industrial application.     

Propylene epoxidation over Ti/MCM-41 catalysts prepared by chemical vapor deposition

Ti-containing mesoporous catalysts were prepared by chemical vapor deposition (CVD) of TiCl₄ on silica MCM-41 in the 700–900 °C temperature range. These samples were characterized (with XRD, ICP, nitrogen adsorption, FT-IR, ESCA, and TEM) and evaluated for the epoxidation of propylene with two alkyl hydroperoxides. The increase of CVD temperature resulted in the decrease of titanium content, catalyst hydroxyl population, crystallinity, and surface area. Catalyst selectivity to the desired product – propylene oxide – was highly sensitive to the deposition temperature. The best Ti/MCM-41 catalyst was prepared at the temperature of 800 °C, which had the maximum propylene oxide yield of 94.3%.     

Effect of γ-alumina crystallinity on the state of rhodium during high-temperature treatments in oxygen and hydrogen

Rhodium catalysts, supported on six γ-Al₂O₃ supports with different crystallinities, were exposed to sequential treatments in hydrogen at 500°C, in oxygen at 760°C, in hydrogen at 500°C and at 760°C, respectively. Samples were characterized by X-ray diffraction and hydrogen chemisorption at various stages in the sequential treatment. Based on the characterization results, it is concluded that the formation of crystalline Rh₂O₃ is a function of γ-Al₂O₃ crystallinity; formation of crystalline Rh₂O₃ increased with increasing crystallinity of γ-Al₂O₃ during treatment in oxygen at 760°C. The crystalline Rh₂O₃ formed during treatment in oxygen at 760°C was reduced to Rh metal by hydrogen at 500°C, but most of the Rh did not adsorb hydrogen at room temperature. Subsequent treatment in hydrogen at 760°C increased the hydrogen adsorption capacity by as much as a factor of three. X-ray line broadening measurements showed that oxygen treatment of reduced Rh/γ-Al₂O₃ at 760°C followed by hydrogen reduction at 500°C resulted in significant increases in Rh crystal size; further treatment in hydrogen at 760°C resulted in additional sintering of Rh.     

Study of Ag/La0.6Sr0.4MnO3 catalysts for complete oxidation of methanol and ethanol at low concentrations

Ag-modified La_0.6Sr_0.4MnO₃-based catalysts with the perovskite-type structure were prepared by using a citric acid sol–gel method, and their catalytic performance for complete oxidation of methanol and ethanol was evaluated and compared with that of the γ-Al₂O₃-supported catalysts, Ag/γ-Al₂O₃, Pt/γ-Al₂O₃, and Pd/γ-Al₂O₃. The results showed that the Ag-modified La_0.6Sr_0.4MnO₃-based catalysts with the perovskite-type structure displayed the activity significantly higher than that of the supported precious metal catalysts, 0.1%Pd/γ-Al₂O₃ and 0.1%Pt/γ-Al₂O₃ in the temperature range of 370–573 K. Over a 6%Ag/20%La_0.6Sr_0.4MnO₃/γ-Al₂O₃ catalyst, the T₉₅ temperature for methanol oxidation can be as low as 413 K. Even at such low reaction temperature, there were little HCHO and CO detected in the reaction exit-gas. However, for the 0.1%Pd/γ-Al₂O₃ and 0.1%Pt/γ-Al₂O₃ catalysts, the HCHO content in the reaction exit-gas reached 200 and 630 ppm at their T₉₅ temperatures. Over a 6%Ag/La_0.6Sr_0.4MnO₃ catalyst, the T₉₅ temperature for ethanol oxidation can be as low as 453 K, with a corresponding content of CH₃CHO in the exit-gas at 782 ppm; when ethanol oxidation is performed at 493 K, the content of acetaldehyde in the exit-gas can be below 1 ppm. Characterization of the catalysts by X-ray diffraction (XRD), TEM, XPS, laser Raman spectra (LRS), hydrogen temperature-programmed reduction (H₂-TPR) and oxygen temperature-programmed desorption (O₂-TPD) methods revealed that both the surface and the bulk phase of the perovskite La_0.6Sr_0.4MnO₃ played important roles in the catalytic oxidation of the alcohols, and that γ-Al₂O₃ as the bottom carrier could be beneficial in creating a large surface area of catalyst. Moreover, a small amount of Ag⁺ doped onto the surface of La_0.6Sr_0.4MnO₃ was able to partially occupy the positions of La³⁺ and Sr²⁺ due to their similar ionic radii, and thus, became stabilized by the perovskite lattice, which would be in favor of preventing the aggregation of the Ag species on the surface and enhancing the stability of the catalyst. On the other hand, modification of the Ag⁺ to the surface of La_0.6Sr_0.4MnO₃ resulted in an increase in relative content of the surface O₂²⁻/O⁻ species highly reactive toward the alcohols and aldehydes as well as CO. Besides, solution of low-valence metal oxides SrO and Ag₂O with proper amounts in the lattice of the trivalent metal perovskite-type oxide LaMnO₃ would also lead to an increase in the content of the reducible Mnⁿ⁺ and the formation of anionic vacancies, which would be favorable for the adsorption-activation of oxygen on the functioning catalyst and the transport of the lattice and surface oxygen species. All these factors would contribute to the pronounced improvement of the catalyst performance.