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.     

Influence of Supports on Catalytic Performance and Carbon Deposition of Palladium Catalyst for Methane Partial Oxidation

The catalytic performance of methane partial oxidation was investigated on Pd/CeO2-ZrO2 and Pd/α-Al2O3 catalysts.The catalysts were characterized by XRD,Raman spectra,and TG-DTA techniques.The results show that CeO2-ZrO2 support is more advantageous for the catalytic activity and stability of catalysts compared to α-Al2O3.TG-DTA and Raman spectra results indicated that carbon deposited on the catalysts was in the form of graphite,which is the main reason for the deactivation of catalysts after a 24-hour reaction.Moreover,CeO2-ZrO2 had positive effect on inhibiting carbon deposition.     

Kinetics of the Oxidation of Bismuthinite in Oxygen�CNitrogen Atmospheres

Bismuth is present in copper concentrates mainly as the mineral bismuthinite (Bi₂S₃). In some cases of smelting of concentrates, a substantial amount of bismuth can lead to contaminated copper cathodes. Thus, understanding the behavior of Bi₂S₃ at high temperatures is crucial to assessing the potential of bismuth removal in the pyrometallurgical process. Therefore, the oxidation of bismuthinite in mixtures of oxygen?Cnitrogen atmospheres was investigated using a thermogravimetric analysis technique. The results indicate that the oxidation process occurs through the following consecutive reactions: $$ \begin{gathered} {\text{First stage: }}{\text{Bi}}_{ 2} {\text{S}}_{ 3} \left( {\text{s,l}} \right) + 3{\text{O}}_{2} \left( {\text{g}} \right) = 2{\text{Bi}}\left( {\text{l}} \right) + 3{\text{SO}}_{ 2} \left( {\text{g}} \right) \hfill \\ {\text{Second stage: }}2{\text{Bi}}\left( {\text{l}} \right) + 3/2{\text{O}}_{2} \left( {\text{g}} \right) = {\text{Bi}}_{2} {\text{O}}_{3} \left( {\text{s,l}} \right) \hfill \\ \end{gathered} $$ The kinetics of the oxidation of bismuthinite (first stage) was studied, and the model ln(1 ?C X) = ?Ck_app t describes the kinetics of this reaction well. The bismuthinite oxidation dependence on oxygen partial pressure was of 0.9 order, and the intrinsic kinetic constants were obtained in the temperature range of 873 K to 1273 K (600 °C to 1000 °C), which were used to determine the activation energy of 91 kJ/mol. The results indicate that the oxidation of bismuthinite is a process controlled by chemical reactions. From this study, it can be concluded that the removal of bismuth from the Bi₂S₃-containing concentrates through a mechanism involving gaseous bismuth compounds is not feasible during an oxidizing roasting and/or smelting of concentrates containing Bi₂S₃.     

Effects of Concentration of La~(3 ) Vacancies in LaMnO_(3 λ) on the Catalytic Activity of Oxidation of CO

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Effect of Lanthanum on Methanol Fuel Exhaust Deep Oxidation over Palladium Catalyst

The performance of deep oxidation of methanol on supported Pd catalyst was examined by a chromatograph-micro-reactor. The results show that the addition of La into γ-Al2O3 support can affect greatly the performance of the Pd catalyst. In the absence of CO, La can decrease the content of oxygen-containing intermediate, although La can not lower the light-off temperature of methanol oxidation. In the presence of CO, La can lower the light-off temperature, decrease theamount of CO adsorption, and weaken evidently “CO inhibition“ to the oxidation of methanol. By XPS technique, it is shown that La modifies the electronic structure of Pd, which attributes to the modifications of the catalytic performance.     

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 ℃.     

Kinetics of the Reaction between CO2—CO and Liquid Copper

Direct determination of the rate of the reaction between CO₂—CO and pure liquid copper in the interfacial reaction regime and an examination of the effect of oxygen has been made by using the ¹⁴C isotope exchange technique. The first order rate constant for the dissociation of CO₂ on clean, oxygen-‘free’ surfaces is found to be described by the equation:

log K⁰(mol/cm².s.atm) = ? 3510/T ? 2.36

between 1150 and 1400°C, to within an uncertainty of +60%. The first order rate constant for the dissociation (k₂) and that for the formation (k₁) of CO₂ on oxygen-doped surfaces are related through the equation:

k1 = k²a⁰

where a_o the oxygen activity in liquid copper with the standard state defined by pCO₂Sol;pCO = 1. Full consistency is found between experiments with ¹⁴C-labelled C0₂ and CO. The effect of a₀ on the rate of dissociation of CO₂ is in agreement with the site-blocking model and the rate constant (k₂) is found to be consistent with the equation:

with a₀ between 0.015 and 50 at 1200°C. In comparison, the magnitude of the reaction rate is significantly greater than those suggested by earlier studies. Possible causes for the discrepancy are discussed.     

In—Situ FTIR Study on Effect of Lathanum on Oxidation Mechanism of Methanol Automobile Exhaust on Supported Palladium Catalyst

The performance of severe oxidation of methanol on 0.1%Pd supported on alumina was studied by a combined device of chromatograph-micro reactor,The results show that the addition of La intoγAl2O3as support can affect the performance of Pd catalyst greatly.By using Pd catalyst comtaining La in methanol oxidation,thouhg,the ignition temperature is not lower than than by using Pd catalyst,the presence of La does suppress the formation of oxygenic intermediates,The results by in-situ FTIR show that the presence of La in the support affects the adsorbed specties and hence the mechanism of severe oxidation of methanol on Pd catalyst.     

Influence of Y_2O_3 on the Oxidation Behaviour of a β-NiAl Coating

A new-type of β-NiAl coating containing Y_2O_3 particles was obtained by electrolytic co-deposition andpack aluminizing techniques,and the influences of the nature of Y_2O_3 and its content on the oxidation behaviourof the coating at 1100℃ were studied.The test results indicate that the oxidation rates of the composite coatingsare reduced and the scale adhesion is also improved remarkably.The content of Y_2O_3 has little influence on theoxidation rates of the composite coatings,but does obviously on the scale adhesion by modifying the configura-tion of the oxides at the scale-coating interface.The needle-like oxides penetrating into the coating show anobvious keying effect.A part of the dispersed Y_2O_3 in the as-deposited coating accumulates and forms aY_2O_3-rich layer at the coating-substrate interface immediately after aluminizing.The layer is beneficial toreduce the degradation of the composite coating.     

A Study on the Kinetics of the Europium Electrochemistry Reduction 1.The Polarization Properties of Europium Reduced at the Cathode

This article studies the polarization properties of the cathode reduction of Eu in the Sm-Eu-Gdchloride system by using a constant potential method.As the feed concentration,temperature,and stirringrate of the system change,the system can gradually turn from chemical polarization to concentrationpolarization,and there would be a higher limiting current.As to the effects of acidity,only at a rather higherpH there will be a typical polarization property.The study can give some bases for the Eu electroreductiontechnlolgy parameter selection.     

Ru-La_2O_3/Al_2O_3催化剂上CO选择氧化本征反应动力学

采用浸渍法制备了用于CO选择氧化的Ru-La2O3/Al2O3催化剂,研究了CO在Ru-La2O3/Al2O3催化剂床层上的CO选择氧化本征动力学.结果表明,在消除内外扩散的条件下,CO在Ru-La2O3/Al2O3催化剂床层的本征反应是一个表面反应控制的一级反应,反应的活化能为76.24kJ/mol.     

包头稀土精矿添加25%碳酸钠焙烧反应动力学研究

采用XRD、DTA-TG及化学分析等方法,对包头稀土精矿添加25%碳酸钠焙烧反应进行了研究。分解反应分两个阶段进行,第一阶段348℃～455℃,稀土氟碳酸盐分解为稀土氟氧化物,铈被氧化得到CeO     

碳酸盐前驱体Ni1/3Co1/3Mn1/3CO3合成条件的研究

以碳酸盐为沉淀剂,采用共沉淀法合成Ni1/3Co1/3Mn1/3CO3前驱体,再按照一定的锂配比将其烧结合成层状Li（Ni1/3Co1/3Mn1/3）O2。通过SEM及电性能测试仪等方法,研究了碳酸盐前驱体的合成条件,考察了碳酸盐前驱体的振实密度与合成时pH值、溶液浓度以及反应时间的关系。经过实验分析,在pH=8、溶液浓度C=2mol.L^-1、反应时间t=12-13h时,合成的碳酸盐前驱体Ni1/3Co1/3Mn1/3CO3振实密度达到最高值0.98g.cm^-3。     

Influence of Direct Reduction Condition of Hematite Pellets with H2/CO on the Oxidation Behaviour of DRI in Air

Direct reduced iron (DRI) is the product of some commercial direct reduction (DR) of iron ore on base of natural gas. DRI tends to oxidize in air generally above 300 °C and then follows spontaneous combustion. To control the oxidation mechanism, several investigators have used different iron samples and methods. This paper gives the results of experimental work carried out for determination of DRI oxidation. The behaviour of DRI oxidation in air after isothermal reduction of hematite pellets with different size, temperature and H₂ / CO mixture is investigated.     

Kinetics of Oxidation Reaction for Magnetite Pellets

An experiment for the oxidation process of single magnetite pellet and theoretical analysis based on modified unreacted core shrinking (MUCS) model were carried out, and the controlling mechanisms of the initial and developing reactions were examined, respectively. From the study of the initial reaction, it was found that the chemical reaction of surface is the controlling step of the overall reaction when the temperature is up to about 750 K, while the mass transfer through the gaseous boundary layer dominates the reaction rate when the temperature is above 750 K. As the reaction developing within the pellet, the mass transfer through the produced layer becomes the controlling step. In addition, the effects of reaction conditions (such as oxygen concentration, temperature) on the fractional oxidation of magnetite pellet were determined.     

Study on Roast Reaction Kinetics of Baotou Concentrate of Rare Earth with 15% Na_2CO_3 Additions

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