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1.
Co 3O 4/CeO 2 composite oxides with different cobalt loading (5, 15, 30, 50, 70 wt.% as Co 3O 4) were prepared by co-precipitation method and investigated for the oxidation of methane under stoichiometric conditions. Pure oxides, Co 3O 4 and CeO 2 were used as reference. Characterization studies by X-ray diffraction (XRD), BET, temperature programmed reduction/oxidation (TPR/TPO) and X-ray photoelectron spectroscopy (XPS) were carried out. An improvement of the catalytic activity and thermal stability of the composite oxides was observed with respect to pure Co3O4 in correspondence of Co3O4–CeO2 containing 30% by weight of Co3O4. The combined effect of cobalt oxide and ceria, at this composition, strongly influences the morphological and redox properties of the composite oxides, by dispersing the Co3O4 phase and promoting the efficiency of the Co3+–Co2+ redox couple. The presence in the sample Co3O4(30 wt.%)–CeO2 of a high relative amount of Ce3+/(Ce4+ + Ce3+) as detected by XPS confirms the enhanced oxygen mobility. The catalysts stability under reaction conditions was investigated by XRD and XPS analysis of the used samples, paying particular attention to the Co3O4 phase decomposition. Methane oxidation tests were performed over fresh (as prepared) and thermal aged samples (after ageing at 750 °C for 7 h, in furnace). The resistance to water vapour poisoning was evaluated for pure Co3O4 and Co3O4(30 wt.%)–CeO2, performing the tests in the presence of 5 vol.% H2O. A methane oxidation test upon hydrothermal ageing (flowing at 600 °C for 16 h a mixture 5 vol.% H2O + 5 vol.%O2 in He) of the Co3O4(30 wt.%)–CeO2 sample was also performed. All the results confirm the superiority of this composite oxide. 相似文献
2.
The oxidation of CH 4 over Pt–NiO/δ-Al 2O 3 has been studied in a fluidised bed reactor as part of a major project on an autothermal (combined oxidation–steam reforming) system for CH 4 conversion. The kinetic data were collected between 773 and 893 K and 101 kPa total pressure using CH 4 and O 2 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 CH 4 partial pressure but was inhibited by O 2. At low partial pressures (<30 kPa), H 2O has a detrimental effect on CH 4 conversion, whilst above 30 kPa, the rate increased dramatically with water content. 相似文献
3.
CO and CH 4 combined oxidation tests were performed over a Pd (70 g/ft 3)/Co 3O 4 monolithic catalyst in conditions of GHSV = 100,000 h −1 and feed composition close to that of emission from bi-fuel vehicles. The effect of SO 2 (5 ppm) on CO and CH 4 oxidation activity under lean condition ( λ = 2) was investigated. The presence of sulphur strongly deactivated the catalyst towards methane oxidation, while the poisoning effect was less drastic in the oxidation of CO. Saturation of the Pd/Co 3O 4 catalytic sites via chemisorbed SO 3 and/or sulphates occurred upon exposure to SO 2. A treatment of regeneration to remove sulphate species was attempted by performing a heating/cooling cycle up to 900 °C in oxidizing atmosphere. Decomposition of PdO and Co 3O 4 phases at high temperature, above 750 °C, was observed. Moreover, sintering of Pd 0 and PdO particles along with of CoO crystallites takes place. 相似文献
4.
The paper presents the results of a study on the electrochemical destruction of pollutants present in a spent reducing bath of a textile factory. The investigations comprised the electro-oxidation of thiourea dioxide (TUD) (the main component of the reducing bath), sulphites and urea, which are formed during oxidation of TUD. The study performed in an undivided cell parallel plate electrodes reactor, using eight different anode materials under various hydrodynamic conditions, proved that electro-oxidation can be successfully applied for treatment of spent reducing baths. The best results of TUD and SO 32− electro-oxidation were obtained with a Ti/Pt electrode, which showed electrocatalytic effect for both the compounds, indicating a possibility of their direct electro-oxidation on the anode. Destruction of TUD and SO 32− proceeded also via indirect electro-oxidation, mediated by chlorine evolved on the anode. The process kinetics was mass transport controlled till Re=5000. No electrocatalytic effects were observed for urea with any of the tested anode materials. The elimination of urea resulted to proceed only by indirect electro-oxidation, mediated by chlorine. For elimination of urea a Ti/Pt–Ir electrode proved to be the best anode, probably due to its high efficiency in electro-oxidation of chlorides into chlorine. 相似文献
5.
The influence of catalyst pre-treatment temperature (650 and 750 °C) and oxygen concentration ( λ = 8 and 1) on the light-off temperature of methane combustion has been investigated over two composite oxides, Co 3O 4/CeO 2 and Co 3O 4/CeO 2–ZrO 2 containing 30 wt.% of Co 3O 4. The catalytic materials prepared by the co-precipitation method were calcined at 650 °C for 5 h (fresh samples); a portion of them was further treated at 750 °C for 7 h, in a furnace in static air (aged samples). Tests of methane combustion were carried out on fresh and aged catalysts at two different WHSV values (12 000 and 60 000 mL g−1 h−1). The catalytic performance of Co3O4/CeO2 and Co3O4/CeO2–ZrO2 were compared with those of two pure Co3O4 oxides, a sample obtained by the precipitation method and a commercial reference. Characterization studies by X-ray diffraction (XRD), BET and temperature-programmed reduction (TPR) show that the catalytic activity is related to the dispersion of crystalline phases, Co3O4/CeO2 and Co3O4/CeO2–ZrO2 as well as to their reducibility. Particular attention was paid to the thermal stability of the Co3O4 phase in the temperature range of 750–800 °C, in both static (in a furnace) and dynamic conditions (continuous flow). The results indicate that the thermal stability of the phase Co3O4 heated up to 800 °C depends on the size of the cobalt oxide crystallites (fresh or aged samples) and on the oxygen content (excess λ = 8, stoichiometric λ = 1) in the reaction mixture. A stabilizing effect due to the presence of ceria or ceria–zirconia against Co3O4 decomposition into CoO was observed. Moreover, the role of ceria and ceria–zirconia is to maintain a good combustion activity of the cobalt composite oxides by dispersing the active phase Co3O4 and by promoting the reduction at low temperature. 相似文献
6.
A series of CoO x/Al 2O 3 catalysts was prepared, characterized, and applied for the selective catalytic reduction (SCR) of NO by C 3H 8. The results of XRD, UV–vis, IR, Far-IR and ESR characterizations of the catalysts suggest that the predominant oxidation state of cobalt species is +2 for the catalysts with low cobalt loading (≤2 mol%) and for the catalysts with 4 mol% cobalt loading prepared by sol–gel and co-precipitation. Co 3O 4 crystallites or agglomerates are the predominant species in the catalysts with high cobalt loading prepared by incipient wetness impregnation and solid dispersion. An optimized CoO x/Al 2O 3 catalyst shows high activity in SCR of NO by C 3H 8 (100% conversion of NO at 723 K, GHSV: 10,000 h −1). The activity of the selective catalytic reduction of NO by C 3H 8 increases with the increase of cobalt–alumina interactions in the catalysts. The influences of cobalt loading and catalyst preparation method on the catalytic performance suggest that tiny CoAl 2O 4 crystallites highly dispersed on alumina are responsible for the efficient catalytic reduction of NO, whereas Co 3O 4 crystallites catalyze the combustion of C 3H 8 only. 相似文献
7.
The catalytic effect of a heteropolyacid, H 4SiW 12O 40, on nitrobenzene (20 and 30 μM) oxidation in supercritical water was investigated. A capillary flow-through reactor was operated at varying temperatures ( T=400–500 °C; P=30.7 MPa) and H 4SiW 12O 40 concentrations (3.5–34.8 μM) in an attempt to establish global power-law rate expressions for homogenous H 4SiW 12O 40-catalyzed and uncatalyzed supercritical water oxidation. Oxidation pathways and reaction mechanisms were further examined via primary oxidation product identification and the addition of various hydroxyl radical scavengers (2-propanol, acetone, acetone-d 6, bromide and iodide) to the reaction medium. Under our experimental conditions, nitrobenzene degradation rates were significantly enhanced in the presence of H 4SiW 12O 40. The major differences in temperature dependence observed between catalyzed and uncatalyzed nitrobenzene oxidation kinetics strongly suggest that the reaction path of H 4SiW 12O 40-catalyzed supercritical water oxidation (average activation Ea=218 kJ/mol; k=0.015–0.806 s −1 energy for T=440–500 °C; Ea=134 kJ/mol for the temperature range T=470–490 °C) apparently differs from that of uncatalyzed supercritical water oxidation ( Ea=212 kJ/mol; k=0.37–6.6 μM s −1). Similar primary oxidation products (i.e. phenol and 2-, 3-, and 4-nitrophenol) were identified for both treatment systems. H 4SiW 12O 40-catalyzed homogenous nitrobenzene oxidation kinetics was not sensitive to the presence of OH√ scavengers. 相似文献
8.
Performance of NO x traps after high-temperature treatments in different redox environments was studied. Two types of treatments were considered: aging and pretreatment. Lean and rich agings were examined for a model NO x trap, Pt–Ba/Al 2O 3. These were done at 950 °C for 3 h, in air and in 1% H 2/N 2, respectively. Lean aging had a severe impact on NO x trap performance, including HC and CO oxidation, and NH 3 and N 2O formation. Rich aging had minimal impact on performance, compared to fresh/degreened performance. Deactivation from lean aging was essentially irreversible due to Pt sintering, but Pt remained dispersed with the rich aging. Pretreatments were examined for a commercially feasible fully formulated NO x trap and two model NO x traps, Pt–Ba/Al 2O 3 and Pt–Ba–Ce/Al 2O 3. Pretreatments were done at 600 °C for 10 min, and used feed gas that simulated diesel exhaust under several conditions. Lean pretreatment severely suppressed NO x, HC, CO, NH 3 and N 2O activities for the ceria-containing NO x traps, but had no impact on Pt–Ba/Al 2O 3. Subsequently, a relatively mild rich pretreatment reversed this deactivation, which appears to be due to a form of Pt–ceria interaction, an effect that is well known from early work on three-way catalysts. Practical applications of results of this work are discussed with respect to NO x traps for light-duty diesel vehicles. 相似文献
9.
Catalytic methane combustion and CO oxidation were investigated over AFeO 3 (A=La, Nd, Sm) and LaFe 1−xMg xO 3 ( x=0.1, 0.2, 0.3, 0.4, 0.5) perovskites prepared by citrate method and calcined at 1073 K. The catalysts were characterized by X-ray diffraction (XRD). Redox properties and the content of Fe 4+ were derived from temperature programmed reduction (TPR). Specific surface areas (SA) of perovskites were in 2.3–9.7 m 2 g −1 range. XRD analysis showed that LaFeO 3, NdFeO 3, SmFeO 3 and LaFe 1−xMg xO 3 ( x·0.3) are single phase perovskite-type oxides. Traces of La 2O 3, in addition to the perovskite phase, were detected in the LaFe 1−xMg xO 3 catalysts with x=0.4 and 0.5. TPR gave evidence of the presence in AFeO 3 of a very small fraction of Fe 4+ which reduces to Fe 3+. The fraction of Fe 4+ in the LaFe 1−xMg xO 3 samples increased with increasing magnesium content up to x=0.2, then it remained nearly constant. Catalytic activity tests showed that all samples gave methane and CO complete conversion with 100% selectivity to CO 2 below 973 and 773 K, respectively. For the AFeO 3 materials the order of activity towards methane combustion is La>Nd>Sm, whereas the activity, per unit SA, of the LaFe 1−xMg xO 3 catalysts decreases with the amount of Mg at least for the catalysts showing a single perovskite phase ( x=0.3). Concerning the CO oxidation, the order of activity for the AFeO 3 materials is Nd>La>Sm, while the activity (per unit SA) of the LaFe 1−xMg xO 3 catalysts decreases at high magnesium content. 相似文献
10.
Direct decomposition of nitrous oxide (N 2O) on K-doped Co 3O 4 catalysts was examined. The K-doped Co 3O 4 catalyst showed a high activity even in the presence of water. In the durability test of the K-doped Co 3O 4 catalyst, the activity was maintained at least for 12 h. It was found that the activity of the K-doped Co 3O 4 catalyst strongly depended on the amount of K in the catalyst. In order to reveal the role of the K component on the catalytic activity, the catalyst was characterized by XRD, XPS, TPR and TPD. The results suggested that regeneration of the Co 2+ species from the Co 3+ species formed by oxidation of Co 2+ with the oxygen atoms formed by N 2O decomposition was promoted by the addition of K to the Co 3O 4 catalyst. 相似文献
11.
Catalytic activities of various metal oxides for decomposition of nitrous oxide were compared in the presence and absence of methane and oxygen, and the general rule in the effects of the coexisting gases was discussed. The reaction rates of nitrous oxide were well correlated to the heat of formation of metal oxide, i.e., a V-shaped relationship with a minimum at −Δ Hf0 around 450 kJ (O mol) −1 was observed in N 2O decomposition in an inert gas. In the case of metal oxides having the heat of formation lower than 450 kJ (O mol) −1, CuO, Co 3O 4, NiO, Fe 2O 3, SnO 2, In 2O 3, Cr 2O 3, the activities were strongly affected by the presence of methane and oxygen. On the other hand, the activities of TiO 2, Al 2O 3, La 2O 3, MgO and CaO were almost independent. The reaction rate of nitrous oxide was significantly enhanced by methane. The promotion effect of methane was attributed to the reduction of nitrous oxide with methane: 4N 2O+CH 4→2N 2+CO 2+2H 2O. The activity was suppressed in the presence of oxygen on the metal oxides having lower heat of formation. On the basis of Langmuir–Hinshelwood mechanism, the effect of oxygen on nitrous oxide decomposition was rationalized with the strength of metal–oxygen bond. 相似文献
12.
Decolorization of reactive brilliant red X-3B was studied by using an Fe–Ce oxide hydrate as the heterogeneous catalyst in the presence of H 2O 2 and UV. The decolorization rate was in the order of UV–Fe–Ce–H 2O 2 > UV–Fe 3+–H 2O 2 > UV–H 2O 2 > UV–Fe–Ce ≥ Fe–Ce–H 2O 2 > Fe–Ce. Under the conditions of 34 mg l −1 H 2O 2, 0.500 g l −1 Fe–Ce, 36 W UV and pH 3.0, 100 mg l −1 X-3B could be decolorized at efficiency of more than 99% within 30 min. The maximum dissolved Fe during the reaction was 1 mg l −1. From the fact that the decolorization rate of the UV–Fe–Ce–H 2O 2 system was significantly higher than that of the UV–Fe 3+–H 2O 2 system at Fe 3+ = 1 mg l −1, it is clear that the Fe–Ce functioned mainly as an efficient heterogeneous catalyst. UV–vis, its second derivative spectra, and ion chromatography (IC) were employed to investigate the degradation pathway. Fast degradation after adsorption of X-3B is the dominant mechanism in the heterogeneous catalytic oxidation system. The first degradation step is the breaking down of azo and CN bonds, resulting in the formation of the aniline- and phenol-like compounds. Then, the breaking down of the triazine structure occurred together with the transformation of naphthalene rings to multi-substituted benzene, and the cutting off of sulphonic groups from the naphthalene rings. The last step includes further decomposition of the aniline structure and partial mineralization of X-3B. 相似文献
13.
Different bulk metal oxides (NiO, CuO, Mn 2O 3, Cr 2O 3 and Co 3O 4) were prepared and tested for the combustion of methane–air lean mixtures (5000 ppmV of CH 4) in presence of SO 2 (40 ppmV). Methane combustion experiments were carried out at ambient pressure, 425 and 625 °C and a space time of 93.3 g h mol CH4−1. Catalysts aged (60 h on stream) both in absence and in presence of SO 2, were characterised by nitrogen physisorption (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature-programmed desorption (TPD-MS) and infrared spectroscopy (DRIFTS). It was observed that Cr 2O 3 is not deactivated at the studied conditions, whereas all the other materials present fast deactivation in presence of SO 2. Aged catalysts characterisation reveals that the outstanding behaviour of the Cr 2O 3 catalyst is caused by the absence of formation of surface sulphates. By contrast, Mn 2O 3 and Co 3O 4 are more active than Cr 2O 3 for methane oxidation in absence of sulphur species, but they are strongly deactivated in presence of SO 2. Finally, the performance of the Cr2O3 catalysts was compared to the corresponding to Pd/Al2O3 catalyst and to a highly sulphur-tolerant perovskite (La0.9Ce0.1CoO3) for the oxidation of methane in a real industrial emission from a coke oven, containing different inorganic gases (NH3, N2, H2, H2O, CO, CO2, SO2 and H2S). Cr2O3 catalyst shows to be also the most stable catalyst for the treatment of these emissions. 相似文献
14.
Four series of cobalt-based catalysts, such as bare Co 3O 4 and CoO, CoO x–CeO 2 mixed oxides, CoO x supported over alumina and alumina–baria and CoMgAl and CoNiAl hydrotalcites have been synthesized and investigated for the oxidative degradation of phenol in the presence of ozone. Characterizations were obtained by several techniques in order to investigate the nature of cobalt species and their morphological properties, depending on the system. Analyses by XRD, BET, TPR, UV–visible diffuse reflectance spectroscopy and TG/DT were performed. The CoNiAl hydrotalcite exhibits, after 4 h of reaction, the highest phenol ozonation activity followed by Co(3 wt%)/Al2O3–BaO and CoMgAl. The samples Co(1 wt%)/Al2O3–BaO and Co(1 and 3 wt%)/Al2O3 show a comparable medium activity, while the oxidation properties of bare oxides Co3O4, CoO and CoOx–CeO2 are really low. Leaching of cobalt ions in the water solution was detected during the reaction, the amount varied depending on the nature of catalysts. A massive release was observed for the CoMgAl and CoNiAl hydrotalcites, while cobalt catalysts over alumina and alumina–baria look much more stable. The recycle of CoOx/Al2O3 and CoOx/Al2O3–BaO was studied by performing three consecutive cycles in the phenol oxidation. Because of the potential interest of the cobalt-supported catalysts in the ozonation process, the oxidative degradation of naphtol blue black was also investigated. On the basis of TPR and UV–visible results it appears that highly dispersed Co2+ ions especially present over Co(3 wt%)/Al2O3–BaO are the main active sites for phenol and naphtol blue black oxidative degradation by ozone. 相似文献
15.
Water–gas shift reaction was studied over two nanostructured Cu xCe 1−xO 2−y catalysts: a Cu 0.1Ce 0.9O 2−y catalyst prepared by a sol–gel method and a Cu 0.2Ce 0.8O 2−y catalyst prepared by co-precipitation method. A commercial low temperature water–gas shift CuO–ZnO–Al 2O 3 catalyst was used as reference. The kinetics was studied in a plug flow micro reactor at an atmospheric pressure in the temperature interval between 298 and 673 K at two different space velocities: 5.000 and 30.000 h −1, respectively. Experimentally estimated activation energy, Eaf, of the forward water–gas shift reaction at CO/H 2O = 1/3 was 51 kJ/mol over the Cu 0.1Ce 0.9O 2−y, 34 kJ/mol over the Cu 0.2Ce 0.8O 2−y and 47 kJ/mol over the CuO–ZnO–Al 2O 3 catalyst. A simple rate expression approximating the water–gas shift process as a single reversible surface reaction was used to fit the experimental data in order to evaluate the rate constants of the forward and backward reactions and of the activation energy for the backward reaction. 相似文献
16.
The selective catalytic reduction (SCR) of nitric oxide by propene over Ir/Al 2O 3 under lean-burn conditions (1000 vpm NO, 2000 vpm C 3H 6, 500 vpm CO, 10 vol.% O 2) was studied. The activity was shown to be strongly enhanced after exposure of the catalyst at 600°C under the reaction mixture, irrespective of the oxidising or reducing pre-treatment. Simultaneously, the Ir dispersion decreased from 78 to 10%. The influence of each component of the reaction mixture on the activation process was examined. The presence of both CO and O 2 was found to be necessary to activate Ir/Al 2O 3 while NO would not be. In situ FT-IR results revealed that initially fully oxidised Ir particles partially reduced in the feed to form Ir 0 reduced surface sites ( νCO at 2060 cm −1) which adsorbed CO up to 350–400°C. The activation under reactants was related to the formation of these sites. The presence of reduced (or partially reduced) Ir sites, possibly siting at the surface of IrO 2 particles and stabilised by CO adsorption, was proposed to be responsible for the SCR activity. 相似文献
17.
Oxidation of propene and propane to CO 2 and H 2O has been studied over Au/Al 2O 3 and two different Au/CuO/Al 2O 3 (4 wt.% Au and 7.4 wt.% Au) catalysts and compared with the catalytic behaviour of Au/Co 3O 4/Al 2O 3 (4.1 wt.% Au) and Pt/Al 2O 3 (4.8 wt.% Pt) catalysts. The various characterization techniques employed (XRD, HRTEM, TPR and DR-UV–vis) revealed the presence of metallic gold, along with a highly dispersed CuO (6 wt.% CuO), or more crystalline CuO phase (12 wt.% CuO). A higher CuO loading does not significantly influence the catalytic performance of the catalyst in propene oxidation, the gold loading appears to be more important. Moreover, it was found that 7.4Au/CuO/Al2O3 is almost as active as Pt/Al2O3, whereas Au/Co3O4/Al2O3 performs less than any of the CuO-containing gold-based catalysts. The light-off temperature for C3H8 oxidation is significantly higher than for C3H6. For this reaction the particle size effect appears to prevail over the effect of gold loading. The most active catalysts are 4Au/CuO/Al2O3 (gold particles less than 3 nm) and 4Au/Co3O4/Al2O3 (gold particles less than 5 nm). 相似文献
18.
In this paper, the effect of the presence of humidity and molecular oxygen on the low temperature oxidation of carbon monoxide on a Co 3O 4 powder surface was studied. The interaction between the probe molecules and the Co 3O 4 surface was investigated by means of diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and quadrupolar mass spectrometry (QMS). Carbon monoxide interacts with the Co3O4 surface and is converted to carbon dioxide at rather low temperature (T≥323 K); the formation of carbonate species is also evident. The reactivity of Co3O4 is strongly depressed by humidity: as a matter of fact, in steam conditions carbon monoxide oxidation is significant at temperatures higher than 523 K. Moreover, the formation of carbonate species is more evident than in dry conditions. The Co3O4 powder surface interacts with oxygen molecules at T≥323 K to originate several activated surface oxygen species. The activation with oxygen does not appear to facilitate significantly the formation of carbon dioxide. 相似文献
19.
Catalytic oxidation of Hg 0 to HgO is an efficient way to remove Hg 0 from coal-fired flue gas. The catalyst with ordered pore structure can lower mass transfer resistance resulting in higher Hg 0 oxidation efficiency. Therefore, in the present work, wood vessels were used as sacrificial template to obtain Co 3O 4 with ordered pore structure. SEM and BET results show that, when the mass concentrations of Co(NO 3) 2·6H 2O was 20%, the obtained catalyst (Co 3O 4 [20%Co(NO 3) 2]) possesses better pore structure and higher surface area. It will expose more available surface active sites and lower the mass transfer resistance. Furthermore, XPS results prove that Co 3O 4 [20%Co(NO 3) 2] has the highest ratio of chemisorbed oxygen which plays an important role in Hg 0 oxidation process. These results lead to a better Hg 0 oxidation efficiency of Co 3O 4 [20%Co(NO 3) 2], which is about 90% in the temperature range of 200 to 350 ℃. Furthermore, Co 3O 4 [20%Co(NO 3) 2] has a stable catalytic activity, and its Hg 0 oxidation efficiency maintains above 90% at 250 ℃ even after 90 h test. A probable reaction mechanism is deduced by the XPS results of the fresh, used and regenerated catalyst of Co 3O 4 [20%Co(NO 3) 2]. Chemisorbed oxygen can react with Hg 0 forming HgO with the reduction of Co 3+ to Co 2+. And lattice oxygen and gaseous oxygen can supplement the consumption of chemisorbed oxygen to oxidize Co 2+ to Co 3+. 相似文献
20.
An aqueous (NH 4) 2CO 3 coprecipitation method, based on that of Groppi et al. [Appl. Catal. A 104 (1993) 101–108] was used to synthesize Sr 1−xLa xMnAl 11O 19− hexaaluminates. These materials were first synthesized by alkoxide hydrolysis. This synthesis route requires special handling of the starting materials and is not likely to be commercially practical. The materials prepared by (NH 4) 2CO 3 coprecipitation have similar surface areas as those prepared by the alkoxide hydrolysis method. Their CH 4 oxidation activity, measured as the temperature needed for 10% conversion of methane, is higher than those prepared by alkoxide hydrolysis. The La-substantiated material, LaMnAl 11O 19−, shows high surface area with 19.3 m 2/g after calcination at 1400°C for 2 h. It is active for CH 4 oxidation with T10% at 450°C using 1% CH 4 in air and 70 000 cm 3/h g space velocity. The stability and activity of LaMnAl 11O 19− prepared by (NH 4) 2CO 3 coprecipitation method is a simple and important step forward for the application of CH 4 catalytic combustion for gas turbines. 相似文献
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