MnO_x/Ce_(0.5+x)Zr_(0.4–x)La_(0.1)O_(1.95)-Al_2O_3 catalysts used for benzene catalytic combustion

Complete oxidation of benzene over supported manganese oxides catalysts was studied.Composite supports Ce0.5+xZr0.4–xLa0.1O1.95-Al2O3 (x=0,0.1,0.2,0.3,0.4),and CeO2-Al2O3 were prepared by co-precipitation method,and manganese oxides (MnOx) catalysts were prepared by incipient wetness method.Catalytic activity was performed in a conventional fixed bed flow reactor.Among these catalysts,MnOx supported on Ce0.8Zr0.1La0.1O1.95-Al2O3 was found to have the highest catalytic activity for benzene oxidation.The comp...     

Structure and oxygen storage capacity of Pd/Pr/CeOe-ZrO2 catalyst： effects of impregnated praseodymia

Praseodymium （Pr） was impregnated to CeO2-ZrO2 solid solution by an impregnation method. The as-obtained Pr modi- fied CeO2-ZrO2 was impregnated with 1 wt.% Pd to prepare the catalysts. The structure and reducibility of the fresh and hydrother- really aged catalysts were characterized by X-ray diffraction （XRD）, Raman, X-ray photoelectron spectroscopy （XPS）, CO chemi- sorption and H2 temperature-programmed reduction （H2-TPR）. The oxygen storage capacity （OSC） was evaluated with CO serving as probe gas. Effects of impregnated Pr on the structure and oxygen storage capacity of catalysts were investigated. The results showed that the aged Pr-impregnated samples had much higher OSC and better reducibility than the unmodified ones. The scheme of structural evolutions of the catalysts with and without Pr was also established. Partial of the impregnated Pr diffused into the bulk of CeO2-ZrO2 during ageing, which inhibited the sintering, and increased the amount of oxygen vacancies in CeO2-ZrO2 support. Furthermore, those impregnated Pr species which covered on the surface of the support obstructed the strong metal-support interaction between Pd and Ce so as to reduce the encapsulation of Pd as well as the back spill-over of the oxygen during the catalytic process.     

Surface reactive species on MnOx（0.4）-CeO2 catalysts towards soot oxidation assisted with pulse dielectric barrier discharge

MnOx(0.4)-CeO2 was investigated for soot oxidation assisted with a pulse dielectric barrier discharge(DBD).The catalysts were evaluated and characterized with TPO(temperature programmed oxidation),X-ray diffraction(XRD),Raman and X-ray photoelectron spectroscopy(XPS).The ignition temperature Ti for soot oxidation decreased from 240.8 to 216.4 oC with the increase of the pulse DBD frequencies from 50 to 400 Hz,lower than that of the case without pulse DBD present(253.4 oC).The results of XRD,Raman and XPS agreed well with the TPO activities of MnOx(0.4)-CeO2 towards soot oxidation.More solid solution of ceria and manganese,and surface reactive species including O2–,O– and Mn4+ were responsible for the enhancement of soot oxidation due to pulse DBD injection in the present study.For solid solution favors to the activation and transformation of those species,which are believed to be involved in the soot oxidation in a hybrid catalysis-plasma.     

Improved sulfur-resistant ability on CO oxidation of Pd/Ce0.75Zr0.25O2 over Pd/CeO2-TiO2 and Pd/CeO2

The influence of sulfation on Pd/Ce0.75Zr0.25O2, Pd/Ce O2-Ti O2 and Pd/Ce O2 was investigated. Physical structure and chemical properties of different catalysts were characterized by N2 adsorption, X-ray diffraction(XRD), CO chemisorption, X-ray photoelectron spectroscopy(XPS), Fourier transform infrared spectroscopy(FT-IR) and X-ray fluorescence(XRF). After 10 h SO2 sulfation, it was found that the decrement on CO oxidation catalytic activity was limited on Pd/Ce0.75Zr0.25O2 compared to Pd/Ce O2-Ti O2 and Pd/Ce O2. It demonstrated that Pd/Ce0.75Zr0.25O2 was more sulfur resistant compared to the other two catalysts. After sulfur exposure, catalyst texture was not much influenced as shown by N2 adsorption and XRD, and surface Pd atoms were poisoned indicated by CO chemisorption results. Pd/Ce0.75Zr0.25O2 and Pd/Ce O2-Ti O2 exhibited less sulfur accumulation compared to Pd/Ce O2 in the sulfation process. Furthermore, XPS results clarified that surface sulfur amount, especially surface sulfates amount on the sulfated catalysts was more crucial for the deactivation in sulfur containing environment.     

Catalytic Reduction of SO2 on CeO2-La2O3 Rare Earth Mixed Compounds

Adding rare earth oxide CeO2 with variable valences to La2O3 formed a mixture of rare earth oxides. By means of dipping CeO2, La2O3 and their mixture, whose carriers were all γ-Al2O3, were used as the catalyst for the reduction of SO2 by CO. The activation process of this catalyst and the impact of temperature and reactant concentration on the activation process were investigated. Using X-ray diffraction, the structure characteristics of catalyst before and after reaction were analyzed to reveal the change of phase structure. The result shows that the rare earth oxide mixtures composing of CeO2 and La2O3, as the catalyst for the reduction of SO2 by CO, diminish activation temperature 50～100℃ less and have higher activity than a single oxide CeO2 or La2O3. The reason possibl is that La2O3 goes into in the lattice of CeO2 to form solid phase complex CeO2-La2O3 and increases the capability of CeO2-La2O3/γ-Al2O3 catalyst to store oxygen, which supplies the redox of CeO2 reaction with a better condition. At the same time, elemental sulfur formed in the redox reaction impels La203 to be transformed to activation phase La2O2S in a lower temperature, which can be explained with the synergism between redox reaction and COS intermediate mechanism reaction.     

Effects of Support on Catalytic Behavior of Combustion Catalyst La0.8Sr0.2CoO3/γ-Al2O3

Combustion catalyst La0.8Sr0.2CoO3 (LSC) is expected to possess relatively high activity for the oxidation of carbon monoxide and many hydrocarbons. If γ-Al2O3 is used as its support, cobalt ions can easily react with γ-Al2O3 at not very high temperature to form spinel CoAl2O4 or spinel-like, which decreases the activity of the combustion catalyst. In this paper, MgAl2O4 and CaAl2O4 were pre-coated on γ-Al2O3 by impregnation respectively, which formed compound support for LSC. It is shown that, when MgAl2O4 layer is covered on the surface of MgAl2O4 by impregnation, the entering of cobalt ions into γ-Al2O3 lattice is restrained, then LSC formed on the surface of MgAl2O4, which leads to a good catalytic activity of xylene complete oxidation. But the layer of MgAl2O4 should be thick enough to reach 30% (mass fraction) MgO in the support due to large size particle of MgAl2O4 crystalline. If polyvinyl alcohol (PVA) is added into the impregnation solution adequately, MgAl2O4 particles formed on the surface of γ-Al2O3 are getting smaller, and less amount of MgAl2O4 is needed to cover up the surface of γ-Al2O3. If CaAl2O4 layer substituted for MgAl2O4, more closed cover is obtained in virtue of fine particles of CaAl2O4. The activity examination shows that smaller particles of MgAl2O4 or CaAl2O4 can be more effective to hinder cobalt ions entering the lattice of γ-Al2O3, and better activities will be obtained.     

储氧材料CeO_2-ZrO_2-La_2O_3-Pr_6O_(11)的制备与表征

采用共沉淀法制备了稀土复合氧化物CeO2-ZrO2-La2O3-Pr6O11储氧材料,通过调节分散剂和表面活性剂浓度、改变工艺参数,得到了比表面积大和高温抗老化能力强的储氧材料,并对该材料进行表征。结果表明,该材料铈、锆、镧、镨的摩尔比约为40∶50∶5∶5;粒径分布D10=1.508μm,D50=3.348μm、D90=6.824μm,材料的新鲜比表面积和1 000℃老化4h后的比表面积分别达到了101.5m2/g和40.21m2/g,具有优异的抗高温老化能力。     

Steam effects over Pd/Ce0.67Zr0.33O2-Al2O3 three-way catalyst

Ceria-zirconia-alumina (CZA) solid solution was prepared by sol-gel method in the present study. 0.5 wt.% Pd supported on CZA was prepared by incipient wetness impregnation. The steam effects for CO and C3H8 oxidation, three-way catalytic activity and stoichiometric window property were studied. The light-off temperature of the CO oxidation reaction shifted to a lower temperature due to the water-gas shift (WGS) reactions. The oxidation of C3H8 was enhanced due to the steam reforming (SR) reactions. The steam promoted the C3H8 oxidation and NO reduction in three-way catalytic reaction. The amplitude of stoichiometric window was amplified by the addition of water to the feed stream.     

Effects of ZrO2 Content on Structure and Performance of Cu/CeO2-ZrO2 Catalysts for Water-Gas Shift Reaction

Water-gas shift(WGS)is a critical step in fuelprocessors for preli minary COclean-up and additionalhydrogen generation prior to the CO clean-up stage,which opened up new potential applications for WGScatalysts.Recently several formulations of noble-met-al…     

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 ℃.     

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.