Catalytic Partial Oxidation of Methane over Ni/CeO2-ZrO2-Al2O3

Nickel catalysts supported on CeO2-ZrO2-CeO2,ZrO2-Al2O3 and Al2O3 were prepared and characterized by means of X-ray diffraction（XRD）,BET areas,H2 temperature-programmed reduction（H2-TPR）,and X-ray photoelectron spectroscopy（XPS）.Through the test of catalytic partial oxidation of methane（CPOM）,Ni/CeO2-ZrO2-Al2O3 displayed the highest activity,which resulted from its largest BET area and best NiO dispersion.Furthermore,Ni/CeO2-ZrO2-Al2O3 maintained a long-time stability in CPOM,which was attributed to its best coking resistance among all the prepared catalysts.     

Effect of different mixing ways in palladium/ceria-zirconia/alumina preparation on partial oxidation of methane

The effect of the mixing ways of Ce0.7Zr0.3O2-Al2O3 mixed oxides on the partial oxidations of methane （POM） was investigated over Pd/Ce0.7Zr0.3O2-Al2O3 catalysts, the mixing ways including salt precursor mixing （ATOM）, precipitator mixing （MOL）, and powder mechanically mixing （MECH）, respectively. The test results indicated that among the three samples, Pd/ATOM had the best catalytic activity while Pd/MOL had the best stability in the stability test. Both the activity sequences of the fresh and used samples were consistent with the order of Pd dispersion. According to the X-ray diffraction （XRD） and BET characterization, the interaction of Ce^4＋, Zr^4＋, and Al^3＋ in the ATOM mixed oxide was in favor of performing higher catalytic activity and thermal stability. The stability test indicated that Pd/MOL had the highest Pd dispersion and least coke formation on the active sites calculated by the Hz-chemisorption and TG results, which was considered to relate to its superior activity of POM to other catalysts.     

Catalytic combustion study of soot on Ce0.7Zr0.3O2 solid solution

The Ce0.7Zr0.3O2 solid solution and CeO2 were prepared using the sol-gel method. The phase structure, crystallite sizes and the reducibility of the catalysts were characterized by XRD and H2-TPR techniques. XRD results indicated that Zr^4＋ had replaced part of Ce^4＋ to form a fluorite-like solid solution, which was favorable to obtain ultrafine nanoparticles. The ratio of main HE consumption for Ce0.7Zr0.3O2：CeO2 was 4.4：1.0, implying that the solid solution could improve the reducibility compared to the single CeO2. The Ce0.7Zr0.3O2 solid solution catalyst showed a sharp combustion peak at 397 ℃, which was 200 ℃ lower than that of the single soot. The good catalytic activity of the Ce0.7Zr0.3O2 was attributed to the formation of nano-CeO2-based solid solution, which enhanced the reducibility and then improved the combustion activity. As Ce0.7Zr0.3O2 could be easily reduced to Ce0.7Zr0.3O2-x meanwhile, after oxygenation, the Ce0.7Zr0.3O2.x was recovered to Ce0.7Zr0.3O2 completely. A catalytic combustion reaction mechanism was proposed： the Ce0.7Zr0.3O2 was reduced to Ce0.7Zr0.3O2-x by the reaction with carbon and then it was recovered to Ce0.7Zr0.3O2-x by the interaction with O2.     

Methane Combustion and TPR/TPO Properties of Pd/CexZr1-xO2/Al2O3 Catalysts

Methane Combustion and TPR/TPO Properties of Pd/Ce_xZr_ 1-xO_2/Al_2O_3 Catalysts     

Partial oxidation of methane on Ni/CeO2-ZrO2/γ-Al2O3 prepared using different processes

The influences of CeO2-ZrO2 and γ-Al2O3 mixing methods on the catalytic activity and stability of partial oxidation of methane (POM) were investigated over Ni/Ce0.7Zr0.3O2-Al2O3 catalysts. The catalysts were characterized by XRD, TPR, H2-chemsorption, and TG-DTA. For fresh catalysts, the results showed that the salt precursor mixing catalyst (ATOM) presented better performance than the catalysts prepared by the precipitator mixing method (MOL) and the powder mechanically mixing method (MECH). The result of XRD suggested that the interaction between CeO2-ZrO2 and Al2O3 in ATOM sample was stronger than the others, which led to more lattice defects and thereby better initial activity. Moreover, the MECH sample had the best stability and the least coke deposition in 24 h stability tests. The results of TPR and H2-chemsorption indicated that the intimate contact of Ni-Al in MECH sample enhanced the ability of resisting coke deposition and metal sintering.     

Preparation and characterization of Ce1-xFexO2 complex oxides and its catalytic activity for methane selective oxidation

A series of Ce1-xFexO2 （x=0, 0.2, 0.4, 0.6, 0.8, 1） complex oxide catalysts were prepared using the coprecipitation method. The catalysts were characterized by means of XRD and H2-TPR. The reactions between methane and lattice oxygen from the complex oxides were investigated. The characteristic results revealed that the combination of Ce and Fe oxide in the catalysts could lower the temperature necessary to reduce the cerium oxide. The catalytic activity for selective CH4 oxidation was strongly influenced by dropped Fe species. Adding the appropriate amount of Fe2O3 to CeO2 could promote the action between CH4 and CeO2. Dispersed Fe2O3 first returned to the original state and would then virtually form the Fe species on the catalyst, which could be considered as the active site for selective CH4 oxidation. The appearance of carbon formation was significant and the oxidation of carbon appeared to be the rate-determining step; the amounts of surface reducible oxygen species in CeO2 were also relevant to the activity. Among all the catalysts, Ce0.6Fe0.402 exhibited the best activity, which converted 94.52% of CH4 at 900 ℃.     

Synthesis of neodymium modified CeO2-ZrO2-Al2O3 support materials and their application in Pd-only three-way catalysts

Ce-Zr-Al-Nd2O3 (CZAN) support materials were prepared by co-precipitation and impregnation methods, respectively. They were characterized by X-ray diffraction (XRD), low temperature nitrogen adsorption-desorption, oxygen pulsing technique, H2-temperature pro-grammed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The Pd-only three-way catalysts (Pd-TWC) supported on these materials were prepared by incipient wetness method and studied by activity tests. The results demonstrated that the CZAN supports obtained by the two methods showed better structural, textural and redox properties than the CZA without Nd2O3, and the addition of Nd2O3 improved the catalytic activity of TWC. Especially, the CZAN-i support prepared by impregnation method had better thermal stability and redox prop-erty. Meanwhile, the Pd/CZAN-i catalyst exhibited the best catalytic performance. XPS measurements indicated that the Nd-modified sam-ples possessed more Ce3+ and oxygen vacancies on the surface of samples, which led to a better redox property. The excellent redox property of support materials helped to improve the catalytic activity of TWC.     

Photocatalytic activity of cerium-doped mesoporous TiO2 coated Fe3O4 magnetic composite under UV and visible light

A novel kind of magnetically separable photocatalyst of cerrium-doped mesoporous titanium dioxide coated magnetite (Ce/MTiO2/ Fe3O4) was prepared and its activities under UV and visible light were reported. The catalysts with Ce/MTiO2 shell and Fe3O4 core were pre-pared by coating photoactive Ce/MTiO2 onto a magnetic Fe3O4 core through the hydrolysis of tetrabutyltitanate (Ti(OBu)4, TBT) with pre-cursors of ammonium ceric nitrate and TBT in the presence of Fe3O4 particles. The MTiO2 shell was for photocatalysis, the Fe3O4 core was for separation by the magnetic field and the doped Ce was used to enhance the photocatalytic activity of MTiO2. The morphological, struc-tural and optical properties of the prepared samples were characterized by Brunauer-Emmett-Teller (BET) surface area, transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-vis absorption spectroscopy. The effect of cerrium-doped content on the photocatalytic activity was studied and the result revealed that 0.5 mol.% Ce/MTiO2/Fe3O4 exhibited highest photoactivity. The photocatalytic activities of obtained photocatalysts under UV and visible light were estimated by measuring the degradation rate of methylene blue (MB, 50 mg/L) in an aqueous solution. The results showed that the prepared photocatalyst was activated by visible light and used as effective catalyst in photooxi-dation reactions. In addition, the possibility of cyclic usage of the prepared photocatalyst was also confirmed. Moreover, Ce/MTiO2 was tightly bound to Fe3O4 and could be easily recovered from the medium by an external magnetic filed. So, the photocatalyst can be reused without any mass loss. It can therefore be potentially applied for the treatment of water contaminated by organic pollutants.     

CeO2-Co3O4 Catalysts for CO Oxidation

CeO2-Co3O4 catalysts for low-temperature CO oxidation were prepared by a co-precipitation method. In combination with the characterization methods of N2 adsorption/desorption, XRD, temperature-programmed reduction （TPR）, and FT-IR, the influence of the cerium content on the catalytic performance of CeO2-Co3O4 was investigated. The results indicate that the prepared CeO2-Co3O4 catalysts exhibit a better activity than that of pure CeO2 or pure Co3O4. The catalyst with the Ce/Co atomic ratio 1 ： 16 exhibits the best activity, which converts 77% of CO at room temperature and completely oxidizes CO at 45 ℃.     

Partial oxidation of methane on Ni/CeO2-ZrO2/γ-Al2O3 prepared using different processes

The influences of CeO2-ZrO2 and γ-Al2O3 mixing methods on the catalytic activity and stability of partial oxidation of methane （POM） were investigated over Ni/Ce0.7Zr0.3O2-Al2O3 catalysts. The catalysts were characterized by XRD, TPR, H2-chemsorption, and TG-DTA. For fresh catalysts, the results showed that the salt precursor mixing catalyst （ATOM） presented better performance than the catalysts prepared by the precipitator mixing method （MOL） and the powder mechanically mixing method （MECH）. The result of XRD suggested that the interaction between CeO2-ZrO2 and Al2O3 in ATOM sample was stronger than the others, which led to more lattice defects and thereby better initial activity. Moreover, the MECH sample had the best stability and the least coke deposition in 24 h stability tests. The results of TPR and H2-chemsorption indicated that the intimate contact of Ni-Al in MECH sample enhanced the ability of resisting coke deposition and metal sintering.     

Ni/Y_2O3-Al2O3 catalysts for hydrogen production from steam reforming of ethanol at low temperature

Y2O3-Al2O3 with different mole ratios of Y:Al were prepared by co-precipitation method. Catalysts Ni/Y2O3, Ni/Al2O3 and Ni/ Y2O3-Al2O3 were prepared by impregnation method. The result of BET showed that Al2O3 with relative high surface area was in favor of Ni distribution, whilst the TPR test demonstrated that composite support had appropriate synergistic effect between active constituent and sup-port, and NiO could be reduced more easily than loaded on the single support. H2-TPD test indicated that the catalyst NYA11 had lots of ac-tivity sites where H could be desorbed easily, which led to hydrogen-rich production over the catalyst. Composite support catalysts exhibited high activity for ethanol steam reforming (SRE), and the supported catalyst with composite of 1:1 mole ratio of Y:Al exhibited the optimum catalytic properties for SRE. Ethanol could be completely converted over catalyst NYA11 even at 450 °C, and there had no inactivation after 60 h continuous reaction, hydrogen yield appeared maximum 35.9% at 400 °C, and tended to increase with increasing H2O/EtOH molar ratio and feed flow rate.     

Synthesis kinetics and thermophysical properties of La_2（Zr_（0.7）Ce_（0.3））_2O_7 ceramic for thermal barrier coatings

La2(Zr0.7Ce0.3)2O7 (LZ7C3) ceramic was synthesized by solid state reaction with La2O3, ZrO2 and CeO2 as starting materials. The synthesis kinetics, phase structure, mass loss and microstructure were studied by thermo gravimetric-different thermal analyzer (TG-DTA), X-ray difference (XRD) and scanning electron microscopy (SEM). The thermal conductivity and thermal expansion coefficient were measured by laser-flash method and pushing-rod method, respectively. XRD results showed that LZ7C3 was a mixture of La2Zr2O7 (LZ, pyro- chlore) and La2Ce2O7 (LC, fluorite). The lowest synthesis temperature and time of LZ7C3 were 1400 oC and 5 h. There were no peaks of La2O3 when the powder granularity was about 0.82 μm in the synthesis process. The atom ratio La:Zr:Ce of prepared LZ7C3 powder was very close to 10:7:3 which was the theory value of LZ7C3. The thermal conductivity of LZ7C3 decreased gradually with the temperature increased up to 1200 oC, and was located within 0.79 to 1.02 W/(m·K), which was almost 50% lower than that of LZ, whereas its thermal expansion coefficient was larger and the value was 11.6×10-6 K-1.     

Study of methane autothermal reforming catalyst

The effects of Ce-ZrOx, Ce-LaOx, Ce-SmOx and Ce-GdOx additions to Rh/Al2O3 catalysts on methane autothermal re-forming were investigated. Activity tests showed that the addition of Ce-ZrOx could significantly reduce the concentration of CO in reformats. When Ce/Zr atomic ratio was 1：1, C%.5Zr0.5O2 solid solution with high thermal stability was obtained, which could effec- tively improve the catalytic performance effectively. The additives of alkaline-earth metals （Mg, K and Ca） on the catalytic properties were also studied. The results of experiments showed that the addition of MgO to Rh/Ce0.5Zr0.5O2/Al2O3 improved the stable per- formance and the carbon resistance of the catalyst. The optimized catalyst was 0.1%Rh/2.0%MgO/40%Ce0.5Zr0.5O2/Al2O3, which showed a highly stable performance for methane autothermal reforming.     

钇掺杂对Ce0.33Zr0.67O2储氧性能的影响

采用柠檬酸溶胶凝胶法制备了一系列钇掺杂的富锆铈锆复合氧化物Ce0.33YxZr0.67-xO2,并通过XRD,BET,OSC,XPS,in-situ CO-FTIR等测试,系统研究了钇掺杂后铈锆复合氧化物储放氧性能的变化规律及其影响因素。结果表明,钇离子能够进入铈锆晶格形成固溶体,并提高铈锆体系的结构热稳定性。对于新鲜样,钇掺杂可大幅提升Ce0.33Zr0.67O2材料的比表面积,提高单位质量铈锆材料的储氧能力;但老化后,钇掺杂样品的储氧性能随着掺杂量的增加而减小。通过XPS及原位红外吸附性能测试证实,钇在Ce0.33Zr0.67O2材料表面主要取代锆离子,其掺杂会降低样品的表面吸附能力,抑制铈的氧化还原反应,从而导致该体系储氧性能的下降。     

Lanthanum Modified Ni/γ-Al2O3 Catalysts for Partial Oxidation of Methane

La modified Ni/γ-Al2O3 catalysts prepared by co-precipitation method using NaOH-Na2CO3 as a precipitator show high activity and selectivity for the partial oxidation of methane (POM). Meanwhile, the addition of La is beneficial for the formation of an active component and stability of support. We investigated some factors including calcining temperature, nickel content, and space velocity, which turned out to have a strong influence on catalytic activity and selectivity. By XRD and TPR, it is concluded that Ni0 reduced from amorphous NiAl2O4 is the major active component for POM.     

Promotional effect of CeO2 and Y2O3 on CuO/ZrO2 catalysts for methane combustion

Catalytic combustion of methane was conducted by using a Cu-based catalyst prepared by the plasma-assisted impregnation method. The properties of the catalysts were surveyed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (H2-TPR). The results showed that the activity of CuO/ZrO2 with the CeO2 and Y2O3 was obviously increased compared with the CuO/ZrO2 catalyst, which was examined in relation to the structure and surface characteristics and might be correlated with their surface oxygen species and redox properties. Among the investigated catalysts, the Ce-CuO/ZrO2 sample exhibited the highest activity for methane combustion.     

Magnetic Properties and Activity of Pt-Er/γ-Al2O3 Catalysts

A series of Pt-Er/γ-Al2O3 catalysts containing 0.5%(mass fraction) platinum and 0.05%-1.5% Er were prepared by impregnation of γ-Al2O3 supported with different concentrations of erbium chloride solution. The surface properties of the catalysts were studied by methods of temperature programmed reduction and temperature programmed desorption. The magnetic behavior of Pt-Er-γ-Al2O3 catalysts were studied with a Faraday magnetic balance and the results show that the addition of Er can affect the surface properties, the catalytic activities, and magnetic behavior of the reforming catalysts. It is found that there is a corresponding relationship between the susceptibility and selectivity of Pt-Er-γ-Al2O3 catalysts. The experimental results show that Er plays the role of electron promoter.     

Effect of metal doping into Ce0.5Zr0.5O2 on catalytic activity of MnOx/Ce0.5-xZr0.5-xM0.2xOy/Al2O3 for benzene combustion

The research investigated the effect of doping two metals separately or together into Ce0.5Zr0.5O2 on the catalytic activity of MnOx/Ce0.5–xZr0.5–xM0.2xOy/Al2O3 (M=Y, Mn, Y and Mn) for catalytic combustion of benzene. The prepared catalysts were characterized by X-ray diffraction (XRD), surface area analysis, oxygen storage capacity (OSC), and H2-temperature programmed reduction (H2-TPR). Cata-lytic test was performed on a conventional fixed bed flow reactor. The characterization results revealed that Y and Mn ions entered into the ceria-zirconia mixed oxides framework, which improved the textural properties and greatly promoted the MnOx dispersion on the support surface. The complete conversion temperature of benzene on MnOx/Ce0.4Zr0.4Y0.1Mn0.1Oy /Al2O3 was 563 K, and the selectivity of carbon dioxides was 99%. This catalyst could be applied in a wide range of GHSV and wide concentration condition, showing great potential for application.     

Effects of La_2O_3 contents on the Pd/Ce_（0.8）Zr_（0.2）O_2-La_2O_3 catalysts for methanol decomposition

The catalytic behaviors of Pd (1.4 wt.%) catalysts supported on CeO2-ZrO2 promoted with La2O3 were investigated for methanol decomposition. The measurements of inductively coupled plasma emission spectroscopy (ICP), N2 adsorption-desorption (BET), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR) and oxygen storage capacity (OSC) were used to characterize the properties of catalysts. The catalysts' activities were tested in a fixed bed continuous ...     

Characterization and CO Catalytic Oxidation of CuO／Ce-Zr-La-O Catalyst

The Ce-Zr-La-O solid solution was prepared by the sol - gel method. The structure and the redox behavior of Ce-Zr-La-O solid solution and CuO/Ce-Zr-La-O catalysts were investigated by using XRD, Raman and TPR techniques. The result shows that the reduction capability of Ce0.7Zr0.3-y LayO solid solution is related to content of La. Appropriate content of La can enhance the redox capability of the solid solution. The oxidation activity of the CuO (6%)/Ce0.7Zr0.15La0. 15O catalyst is the highest. CuO, which finely dispersed and interacted with the support, is the site of oxidation activity.