Influence of the composition of composites based on Y-and Sc-stabilized zirconium dioxide on catalytic properties in the oxidative conversion of methane

The effect of the composition of composites based on Y-and Sc-stabilized zirconium dioxide doped with CeO₂ and transition metal (Cu, Co, Ni) oxides on catalytic properties in the oxidative conversion of methane was studied. The activity of the composites correlated with the quantity and mobility of oxygen in them. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 3, pp. 184–188, May–June, 2006.     

The effect of the conditions for the preparation of iron oxide nanoparticles on their catalytic characteristics in the oxidation of CO

The catalytic characteristics of systems prepared by mechanically mixing iron oxide nanoparticles, produced in the thermolysis of carboxylate complexes at 300–750°C, with aluminum oxide in the oxidation of CO were studied. It was shown that increase in the size of the iron oxide nanoparticles leads to decrease in the catalytic activity of the samples as a result of their different structural and textural characteristics, which change in relation to the synthesis conditions. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 5, pp. 300–305, September–October, 2006.     

Effect of temperature on the structural characteristics of zirconium dioxide nanoparticles produced under conditions of microwave treatment

The effect of the sintering temperature on the structural characteristics of nanosized zirconium dioxide particles treated by microwave radiation during the drying process was investigated by small-angle X-ray scattering and the BET method. It was shown that the specific surface area, particle size, polydispersivity index, and surface and mass fractal dimensionality of zirconium dioxide depend on its heat treatment conditions. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 3, pp. 138–143, May–June, 2008.     

Effect of ZrO<Subscript>2</Subscript> morphology in copper–cerium–zirconium oxide systems on their catalytic properties in the reaction of co oxidation in hydrogen-rich mixtures

We studied the catalytic properties of copper–cerium oxide systems, deposited on supports obtained by calcination of yttrium-stabilized zirconium dioxide at 300-1000 °C, in the reaction of selective oxidation of CO in a stream of hydrogen. We have shown that the catalytic activity of the samples obtained correlates with the activity of the original supports in the reaction of CO oxidation: the highest CO conversion is observed on catalysts with the highest and the lowest specific surface area. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 2, pp. 115-120, March-April, 2009.     

Effect of fractal dimension of zirconium dioxide on its catalytic properties in the oxidation of CO

The effect of fractal dimension of zirconium dioxide on its catalytic properties in the oxidation of CO has been studied. The interconnection between the pre-exponential factor of the reaction rate constant and the fractal dimension of the catalyst has been established. It has been shown that the pre-exponential factor decreases with an increase in the mass fractal dimension.     

Effect of synthesis conditions for phosphated mesoporous zirconium dioxide on formation of its structure and adsorption properties

We have used X-ray phase analysis, temperature programmed desorption of argon, and IR spectroscopy to study the conditions and characteristics of formation and the adsorption and acidic properties of mesoporous phosphated zirconium dioxide. We have established that treatment of a mesostructural and mesoporous hydrogel of zirconium hydroxide with a solution of orthophosphoric acid not only promotes stabilization of the mesostructure and the texture when detemplated, but also functionalization of the zirconium dioxide surface. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 1, pp. 49–54, January–February, 2006.     

金属核及氧化铈的物理化学性质对一氧化碳氧化的影响

氧化铈独特的氧化还原性能使其适合用作氧化反应中的催化剂或载体.氧化铈负载的过渡金属纳米粒子或孤立的单原子提供了金属-载体界面,从而降低了去除界面氧原子的能耗,提供了可以参与ManVanKulvian氧化过程的活性氧物种.CO氧化是测试氧化铈负载催化剂还原性的主要探针反应,并且它常见于在相对低温下消除CO的各种应用中.在过量H2中优先氧化CO(PROX)反应可控制CO浓度达到超低水平,以防止氢氧化电催化剂中毒.催化剂在CO氧化反应中的活性和在PROX反应中对CO和H2的选择性取决于金属物种的种类和分散性、CeO2的结构和化学性质以及催化剂的合成方法.在这篇综述中,我们总结了最近发表的关于CeO2负载的金属纳米粒子和单原子催化CO氧化和PROX反应的相关工作;以及不同的负载金属和同种金属在普通CeO2表面上的反应性.我们还总结了密度泛函理论计算中提出的最可能的反应机理;并且讨论了各种负载型金属在PROX反应中影响CO氧化选择性的因素.     

Effect of the means of preparation of nanodispersed CuO/MgO catalysts on their activity in the oxidation of CO

A method is proposed for obtaining copper-containing catalysts by means of mechanical mixing of previously formed monodispersed CuO nanoparticles (mean particle diameter 12 nm) with MgO. Higher activity was found for these catalysts in the oxidation of carbon monoxide than for the analogous copper-containing systems prepared by impregnation and deposition of cupric oxide nanoparticles from colloidal solution. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 3, pp. 165–169, May–June, 2008.     

Influence of pH values in the preparation of CuO-CeO2 on its catalytic performance for the preferential oxidation of CO in excess hydrogen

CuO-CeO2 catalyst prepared with co-precipitation showed high catalytic performance for the preferential oxidation of CO in excess hydrogen (PROX). Influence of pH values in the preparation of CuO-CeO2 on its catalytic performance was investigated in this work. The CuO-CeO2 catalyst prepared at pH = 13.03 had the smallest particle size (5.4 nm), the largest surface areas (138 m2/g) and the highest activity with CO conversion of 99.6% at 130 ℃. The CuO-CeO2 catalyst was characterized using BET, XRD and TPR techniques. The results showed that when the pH value of the mixed solution containing Cu and Ce species was properly adjusted, both the adsorption layers and diffusion layers of the formed colloidal particles in hydroxide precursor of CuO-CeO2 were modified, resulting in the better catalytic performance for PROX on the final CuO-CeO2 catalyst.     

Promoting effect of tin oxide on the activity of silica- supported gold catalysts used in CO oxidation

In this study various Au/SnO_x-SiO₂ catalysts were prepared and tested in CO oxidation. It was found that the addition of tin oxide onto silica increased significantly the activity of Au/SiO₂ catalysts due to the alteration of the nanoenvironment of gold, which was evidenced by XPS and FTIR measurements.     

Effect of the nature of the support for copper-cerium oxide catalysts on selective oxidation of CO in hydrogen-rich mixtures

We have studied the catalytic properties of copper-cerium oxide catalysts, supported on zirconium, aluminum, titanium, and manganese oxides, in the reaction of selective oxidation of CO in hydrogen-rich mixtures. We have shown that the high activity and selectivity of catalysts supported on zirconium and aluminum oxides is connected with the presence of (in addition to divalent copper) higher amounts of copper in the (+1) oxidation state in the catalysts. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 2, pp. 119–124, March–April, 2006.     

制备条件对异丁烯选择性氧化催化剂性能的影响

通过正交实验设计，改变钼酸铵溶液的质量分数、pH值和催化剂焙烧温度，利用共沉淀法制备了一系列Mo-Bi-Co-Fe-Ce-Cs-K复合氧化物催化剂。借助于BET、TG-DSC、XRD等分析方法对催化剂的物理化学性质进行了表征。在常压连续流动固定床反应器中，系统地考察了上述三种制备条件对复合氧化物催化剂催化异丁烯选择性氧化生成甲基丙烯醛反应性能的影响。结果表明，大比表面积的催化剂具有较高的活性，而平均孔径小的催化剂选择性较差。 催化剂的最佳制备条件为： 钼酸铵溶液的质量分数10%、 pH值2～3、 焙烧温度500 ℃。在异丁烯∶空气=6∶94（体积比）、GHSV=3 600 h－1和360 ℃条件下，异丁烯转化率87.2％，甲基丙烯醛选择性72.0％，甲基丙烯醛收率62.7％。     

Effect of ZSM-11 crystallinity on its catalytic performance in benzene to phenol oxidation with nitrous oxide

Evolution of ZSM-11 zeolite crystal and pore structure has been studied at 150°C depending on the synthesis time. The amorphous gel was shown to be catalytically inert over the whole induction period, which precedes the crystallization process. The concentration of active sites and the catalytic activity in the oxidation of benzene to phenol is related to the zeolite structure formation and the increasing degree of crystallinity.     

Influence of palladium on the structure of LaSrCo0.9Pd0.1O4 catalysts and their properties for the selective oxidation of CO

The mixed oxides were prepared and used successfully for selective CO oxidation. Pd has a significant influence on the values of S_BET, V_p and XPS, and catalytic properties.     

Effect of structural,redox and acid characteristics of M<Subscript>x</Subscript>O<Subscript>y</Subscript>/ZrO<Subscript>2</Subscript>(Al<Subscript>2</Subscript>O<Subscript>3</Subscript>) (M-Mn,Co, Cr) oxide nanocomposites on their catalytic properties in the deep oxidation of methane

Alumina-and zirconia-manganese catalysts for the deep oxidation of methane were studied by X-ray phase analysis, temperature-programmed hydrogen reduction, and IR spectroscopy. The most active catalyst has the optimal combination of dimensional, redox, and acid characteristics. The zirconia-manganese catalysts formed on the surface of a kaolin-aerosil honeycomb matrix provides for 80–100% conversion of methane to CO₂ at 690–750 °C. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 6, pp. 367–372, November–December, 2007.     

Properties of the surface layer and catalytic activity of Ta<Subscript>2</Subscript>O<Subscript>5</Subscript> with Pt or Pd additives in the oxidation of hydrogen

The catalytic activity in the oxidation of hydrogen (in the gaseous state in the presence of excess oxygen) has been studied for samples of Pt(Pd)/Ta₂O_5−x, formed by reduction with hydrogen. The samples obtained had greater activity than the traditional catalysts Pt(Pd)/Al₂O₃. According to X-ray diffraction analysis and electron microscopic studies, Ta₂O_5−x becomes amorphous with the formation of more reduced non-stoichiometric oxygen-deficient tantalum oxides with a surface layer of catalyst. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 3, pp. 180–185, May–June, 2008.     

Influence of reduction energy match among CuO species in CuO-CeO2 catalysts on the catalytic performance for CO preferential oxidation in excess hydrogen

In the present study, we have investigated the reducibility of CuO species on CuO-CeO2 catalysts and the influence of CuO species on the catalytic performance for CO preferential oxidation (CO PROX) in excess hydrogen. It is revealed that the smaller the difference of reduction temperature (denoted as ?T) for two adjacent CuO species is, the higher the catalytic activity of CuO-CeO2 for the PROX in excess hydrogen may be obtained. It means that if the reduction energy of Cu0-Cu2+ pairs matched better, the reduction-oxidation recycle of Cu0-Cu2+ pairs would go on more easily, then the transferring energy of Cu0-Cu2+ pairs would be lesser. Therefore, the CuO-CeO2 catalysts will be largely improved in their catalytic performance if the different CuO species on the catalysts have matched the reduction energy, which would allows them to cooperate effectively.     

Influence of redox properties on the activity of iron oxide catalysts in dehydrogenation of propane with CO2

Different Fe-containing catalysts (pure Fe₂O₃, Fe₂O₃ supported on active carbon or g-Al₂O₃, and hydrotalcite derived Mg-Fe oxides) were examined in the dehydrogenation of propane performed in an Ar or CO₂ atmosphere at 873 K. A promoting effect of carbon dioxide was found for the Fe₂O₃ and Fe₂O₃/AC samples. The catalytic results are discussed in terms of redox properties of the catalysts determined by temperature-programmed reduction (TPR). This revised version was published online in August 2006 with corrections to the Cover Date.     

Nickel-containing nanophases as the carriers of catalytic active sites in the ethylene oligomerization in the presence of systems based on Ni(acac)2 and organoaluminum compounds

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Influence of NO on the Reduction of NO2 with CO over Pt/SiO2 in the Presence of O2

Reduction of NO2 with CO in the presence of NO and excess oxygen, a model mixture for flue gas, over a 0.1% Pt/SiO2 catalyst was studied. The related reaction mechanisms, such as oxidation of CO and NO, were discussed. It was found that there was a narrow temperature window （180-190 ℃） for the reduction of NO2 by CO. When the temperature was lower than the lower limit of the window, the reduction hardly occurred, while when the temperature was higher than the upper limit of the window, the direct oxidation of CO by O2 occurred and thereby NO2 could not be effectively reduced by CO. The presence of NO shifted the window to higher temperatures owing to the inhibition effect of NO on the activation of O2 on Pt, which made it possible to reduce NO2 by CO in flue gas.