Inhibition Effect of Sulfation on the Activity of Pt/Tio2 Catalysts for Methane Combustion
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The Pt/TiO2-S catalysts with SO42- modification were synthesized and employed for methane combustion. Experimental and theoretical studies reveal that the sulfation of TiO2 supports drastically aggravates the reduction of Pt2+→Pt0 in Pt/TiO2-S catalysts under the oxidizing atmosphere, weakens the adsorption of CH4, and raises the activation energy barrier of the initial C-H in CH4, leading to the severe deactivation of activity towards methane combustion.Keywords:
Catalytic combustion
Catalytic combustion of hydrogen/air mixture inside micro-tube was numerically investigated with detailed gas phase and surface catalytic chemical reaction mechanisms. Combustion characteristics for different reaction models, inlet velocity, tube diameter on surface catalytic combustion reaction, and comparison of numerical and experimental studies were discussed. The Computational results indicate that the surface catalytic combustion restrains the gas phase combustion. The effect of the surface catalytic reaction on the gas phase reaction can be divided to three types. The existence of catalytic wall will help to reach complete reaction in the micro-tube. Some theoretical evidences are provided for the application of catalytic combustion to Micro-electromechanical System (MEMS) and the extension of the combustion limits.
Catalytic combustion
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Catalytic combustion of hydrogen/air mixture inside a micro-tube was numerically investigated by using the FLUENT coupled with the CHEMKIN and detailed chemical reaction mechanisms. The combustion characteristics of different reaction models and the influence of inlet velocity and tube diameters on surface catalytic combustion reaction were discussed. The computational results indicate that surface catalytic combustion restrains gas phase combustion. Inlet velocity and tube diameters have important influence on catalytic combustion of hydrogen. For smaller inlet velocities,reaction is dominated by gas phase combustion. As the inlet velocity increases,there exist both surface catalytic combustion and gas phase combustion. For bigger inlet velocities,reaction is dominated by surface catalytic combustion. The temperature of flame core decreases with the decrease of tube diameter. Some theoretical evidence is provided for the application of catalytic combustion to micro-electromechanical system(MEMS)and extension of combustion limits.
Catalytic combustion
CHEMKIN
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The La-hexaaluminate catalyst with high temperature stability and catalytic activity was successfully synthesized by the reverse microemulsion method using the buffer solution of NH4HCO3 and NH4OH as a precipitation agent.With methane catalytic combustion as a probe reaction,the catalytic activity was examined on a fixed bed flow reaction system in order to compare their catalytic activity.The tested results showed that the hexaaluminate precursor formed in reverse microemulsion with chemical homogeneouness,and the La-hexaaluminate catalytic crystalline formed at a lower temperature of 1050 ℃.The catalytic activity was greatly enhanced with the substitution of Fe or Mn ions for Al ions in hexaaluminates,and the Fe-substituted La-hexaaluminate catalysts exhibited the high temperature activity and stability.The Mn-substituted La-hexaaluminate catalysts exhibited low temperature catalytic activity.The research results also indicated that the Fe-and Mn-substituted La-hexaaluminate catalysts exhibited the highest catalytic activity on the catalytic combustion of methane,and their effects on the structure and catalytic activity were also studied,due to the well synergic effect between Fe,Mn and La ions of La-hexaaluminates.
Catalytic combustion
Microemulsion
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Catalytic combustion
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As a new way of combustion,catalytic combustion breaks the flammable limits of conventional flame combustion,and the combustion of ultra-natural gas/air mixture under the flammable limits is realized.Its combustion efficiency is higher,which can improve the ratio of energy utilization.Base on investigating the catalytic combustion tchnology and the characteristics of energy utilization in China, a heating system of catalytic combustion burner was presented.The characteristic of this system was analyzed.The combustion efficiency and socioeconomic benefit of catalytic combustion burner were analyzed.The conclusion that catalytic combustion burner has the energy saving and environmental protection is proposed.
Flammable liquid
Catalytic combustion
Gas burner
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Catalytic combustion,which achieved the combustion of lean-natural gas/air mixture below the flammability limit of conventional combustion and improved the ratio of energy utilization with 100% fuel efficiency.To improve the catalytic combustion thermal efficiency,on the basis of catalytic combustion burner Ⅱ,the catalytic combustion burner Ⅳ was designed.Moreover,the combustion conditions of catalytic combustion and gas phase combustion in burner IV were analyzed respectively,and the thermal efficiency of catalytic combustion was compared with gas phase combustion.Experimental result shows that under other similar conditions,catalytic combustion has higher thermal efficiency than that of gas phase combustion when excess air ratios of catalytic combustion was higher.
Catalytic combustion
Flammability limit
Thermal efficiency
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A series of Ce1−XSnXO2 (X = 0, 0.2, 0.3, 0.4, 0.5, 0.9, 1) catalysts were synthesized via the combustion method. The physical and chemical structures of the prepared catalysts were systematically characterized by XRD, BET, SEM, TEM, XPS, and TPR. The Ce1−XSnXO2 catalysts have higher catalytic activities than the mono-oxide catalysts, as there are synergistic effects between CeO2 and SnO2. The catalytic activities of the Ce1−XSnXO2 catalysts are dependent on the X for the catalytic combustion of ethyl acetate (EA). The Ce1−XSnXO2 (X < 0.5) catalysts show high catalytic performances. Meanwhile, the Ce0.8Sn0.2O2 and Ce0.7Sn0.3O2 catalysts display the highest catalytic performance, with T50 = 190 °C and T90 = 210 °C. More importantly, the Ce0.8Sn0.2O2 catalyst exhibits superior thermal and catalytic activity stability. It is found that the Ce1−XSnXO2 catalysts form solid solutions, as the X is <0.5. The reduction of Sn4+ species to Sn2+ is significantly promoted by the CeO2, which is an important factor attributed to the high catalytic activities of the solid solution Ce1−XSnXO2 catalysts. The catalytic activities of the Ce1−XSnXO2 catalysts exhibit a strong correlation to the surface atomic areas of Ce3+ and Oα (VO). In other words, the higher surface atomic areas of Ce3+ and Oα (VO) are, the higher the catalytic activities will have.
Catalytic combustion
Selective catalytic reduction
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Catalytic combustion
Organometallic Chemistry
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In this thesis,a series of perovskite catalysts are prepared with the method of explosion.The catalytic combustion of methylbenzene is compared with non catalytic combustion,it is found that the catalytic combustion has the advantage of lower reaction temperature and less consumption of heat.By means of tests of XRD,TPR,and activity evaluation,it is concluded that the adsorbed oxygen with low combinative energy on these catalysts exertes pivotal action for the reaction of methylbenzene catalytic combustion.
Catalytic combustion
Environmental Pollution
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The gas boilers of conventional flame always produce varying degrees of combustion products NOx and CO,which make the environmental pollution and energy waste.As a new way of combustion,catalytic combustion breaks the flammable limits of conventional flame combustion,and realizes the combustion of ultra-natural gas/air mixture under the flammable limits.Its combustion efficiency is higher,which can improve the ratio of energy utilization.The way of applying the catalytic combustion to gas boilers could solve the gas boilers' lower combustion efficiency,and achieve the purpose of energy-saving.On the basis of catalytic combustion burner Ⅰ,the catalytic combustion burner Ⅱ was designed according to the catalytic combustion and water heaters.The heat loss and thermal efficiency of catalytic combustion burner Ⅱwere analyzed and compared with that of flame combustion boilers.The results show that catalytic combustion burner Ⅱ's heat loss is not so high as considered,and its pollutant emissions are lower.
Catalytic combustion
Flammable liquid
Gas burner
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