Catalytic properties of ferrites in oxidation reactions

Catalytic activities of ferrites MFe₂O₄ (M = Cu, Co, Ni, Mg, and Zn) and M¹ _0.5M² _{0 .5}Fe₂O₄ (M¹ = CU; M² = Co, Zn, and Mg) in oxidation of CO and ethylbenzene were investigated, and their dependences on the cation nature were established. Higher activities were observed for catalysts containing ions with variable valence (Cu, Co, and Ni). A correlation between catalytic and adsorption properties of ferrites was found.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 49–52, January, 1996.     

Catalytic properties of manganites in the oxidation of CO and hydrocarbon

Manganites with a spinel structure MMn₂O₄ (M = Co, Cu, Zn, Mo) and M¹ _0.5M² _0.5 Mn₂O₄ (M = Co, Cu, Zn, Mg) have been synthesized and tested in the catalytic oxidation of CO, C₃H₆, and ethylbenzene. The dependence of the catalytic activity of the manganites on the nature of the cation has been established. The spinels containing transition metal ions (Cu, Co) are more active. A relation between catalytic and adsorption properties of manganites has been established. The participation of the lattice oxygen in the oxidation of CO to CO₂ has been found. The mechanism of the oxidation is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No, 11, pp, 2686–2669. November, 1996.     

Catalytic oxidation of CO,hydrocarbons, and ethyl acetate over perovskite-type complex oxides

The catalytic activity of M^IM^IIO₃] perovskite-type complex oxides (M^I = La, Y, Nd, Yb; M^II = Co, Mn, Ni) in the oxidation of CO, propylene, benzene, ethylbenzene,o-xylene, and ethyl acetate was investigated. The Co-containing catalysts were shown to be more active in the oxidation than the Mn-containing catalysts. A relationship between the catalytic and adsorption properties was established.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 602–605, April, 1994.     

Oxidation of CO and hydrocarbons over perovskite-type complex oxides

The catalytic activity of perovskites M^IM^IIO₃ (M^I=La; M^II=Co, Mn, Cr, Al, Ni, and V) and M^ICoO₃ (M=Y, Nd, Sm, and Er) in the oxidation of CO, propylene, and ethylbenzene was investigated. The highest activity was observed for the M^ICoO₃ catalysts with perfect perovskite structure. The nature of the rare-earth element has no influence on the catalytic activity. Deformation of the octahedral coordination of the metal was found for the less active catalysts. The interaction of gases (CO, CO+air) with the catalyst surface was investigated. The more active catalysts adsorb a greater amount of O₂, and the adsorption occurs in the temperature region of the oxidation reaction. The activities of the perovskite- and spinel-type catalysts were compared under similar conditions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 698–701, April, 1999.     

Regularities of formation and catalytic properties of supported cobaltites in the oxidation of CO and hydrocarbons and in the reduction of nitrogen oxides

The catalytic properties of supported cobaltites MCo₂O₄ (M=Cu, Mn, Zn, Mg) in the oxidation of CO, C₃H₆, and ethylbenzene and reduction of nitrogen oxides were investigated. The catalytic activity depends on the calcination temperature and the nature of the cation. The regularities of formation and the state of the surface of the catalysts were studied by IR spectra and diffuse reflectance spectra in the UV and visible regions. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1547–1550, September, 2000.     

Catalytic properties of the thermoactivated schungite rock

A high catalytic activity of the thermoactivated schungite rock was demonstrated for reactions of CO oxidation, neutralization of CO + NO _x mixtures (model exhaust gas), oxidation of o-xylene, and oxidative dehydrogenation of ethylbenzene to styrene.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1555–1560, August, 2004.     

Weakly bound oxygen in the catalytic CO oxidation and exoemission from complex oxides having a spinel structure

The catalytic activity of complex oxides M^IM^II ₂O₄ (M^I=Cu, Ni, Co, Zn, or Mg; M^II=Mn or Cr) with a spinel structure in the oxidation of CO and the low-temperature (20–400°C) exoemission of negative charges from their surface were investigated. A relationship between the catalytic activity and the emissivity of the systems under study was found. The role of the charged species of weakly bound oxygen in exoemission and oxidative catalysis by the complex oxides is discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1618–1621, September, 1997.     

Catalytic properties of chromites with a spinel structure in the oxidation of CO and hydrocarbons and reduction of nitrogen oxides

The catalytic activity of supported chromites MCr₂O₄/-Al₂O₃ (M = Cu, Co, Mn, Zn, Mg) in the oxidation of CO, C₃H₆, and o-xylene and NO_x reduction was studied. The catalytic activity depends on the calcination temperature and cation nature. The features of the formation of the catalysts were studied by the UV-Vis diffuse reflectance and IR spectroscopies.     

Exoemission and catalytic activity of oxides with perovskite and spinel structures in the oxidation of CO and hydrocarbons

Low-temperature (20—400 °C) exoemission of negative charges from mixed oxides having the perovskite structure M¹M²O₃ (M¹ = La; M² = Co, Mn, Ni) or the spinel structure M¹M² ₂O₄ (M¹ = Cu; M² = Fe, Co, Cr) was studied. The relationship between the catalytic activity in CO, ethylbenzene, and propylene oxidation and the emissivity of the oxides was elucidated. The role of weakly bound oxygen and variable-valence ions in the exoemission and redox catalysis by mixed oxides is discussed.     

Catalytic oxidation of methane at low temperature over Pd-containing perovskite type oxides

Two types of catalysts with the same palladium loading, palladium-substituted perovskite La_0.95Ce_0.05Co_0.95Pd_0.05O₃ and perovskite-supported palladium catalyst Pd/La_0.95Ce_0.05CoO₃ were prepared by the combustion and impregnation method, respectively. The catalyst structure was characterized by X-ray diffraction (XRD), BET measurements, temperature-programmed reduction (TPR) and the methane oxidation activity of the catalysts were investigated in detail. It was found that the activity performance of Pd/La_0.95Ce_0.05CoO₃ was higher than that of La_0.95Ce_0.05Co_0.95Pd_0.05O₃, and this was owing to the ease of reduction of palladium in the former.     

Au/TS-1选择性催化氧化NO性能研究

制备了负载型Au/TS-1催化剂,采用XRD、SEM、TEM等方法进行了表征,并将其应用于选择性催化氧化NO反应,考察了各工艺条件对NO催化氧化效率的影响。结果表明,Au/TS-1催化剂具有良好的结晶度,Au粒子成功地负载在TS-1上。该催化剂在选择性催化氧化NO反应中具有优异的低温催化氧化活性,在NO体积分数为1×10-3,O2含量为10%,空速为5 000 h-1,Au的负载量为1.0%,180℃时,NO的氧化率高于55%(此时最适宜吸收处理);260℃时,氧化率可达到78%。     

Impact of metalloporphyrin-based porous coordination polymers on catalytic activities for the oxidation of alkylbenzene

Seven metalloporphyrin-based porous coordination polymers: Fe^ш (TZP)Poly ( CP1 ), Co^II (TZP)Poly ( CP2 ), Ni^II (TZP)Poly ( CP3 ), Cu^II (TZP)Poly ( CP4 ), Zn^II (TZP)Poly ( CP5 ), Mn^II (TZP)Poly ( CP6 ), Pb^II (TZP)Poly ( CP7 ) (TZP = 5,10,15,20- tetrakis[4-(2,3,4,5-tetrazolylphenyl)] porphyrin) were prepared and characterized. CP1−CP7 are amorphous aggregation supported with lower crystallinity by scanning electron microscopy, Brunauer−Emmett−Teller and powder X-ray diffraction. These coordination polymers exhibit effective dye scavenging and catalytic activities toward the oxidation of alkylbenzene to ketones and can be reused by filtration with a slight decreasing of catalytic activities. Metal atoms metalloporphyrin polymers have a great influence on the catalytic activities of metalloporphyrin polymers.     

Selective catalytic oxidation of NO over iron and manganese oxides supported on mesoporous silica

The selective catalytic oxidation （SCO） of NO was studied on a catalyst consisting of iron-manganese oxide supported on mesoporous silica （MPS） with different Mn/Fe ratios. Effects of the amount of manganese and iron, oxygen, and calcination temperature on NO conversion were also investigated. It was found that the Mn-Fe/MPS catalyst with a Mn/Fe molar ratio of 1 showed the highest activity at the calcination temperature of 400 °C. The results showed that over this catalyst, NO conversion reached 70% under the condition of 280 °C and a space velocity of 5000 h-1. SO2 and H2O had no adverse impact on the reaction activity when the SCO reaction temperature was above 240 °C. In addition, the SCO activity was suppressed gradually in the presence of SO2 and H2O below 240 °C, and such an effect was reversible after heating treatment.     

碳纳米纤维增强钴酞菁催化氧化染料的性能研究

将氨基钴酞菁（CoTAPc）以共价键的形式负载到碳纳米纤维（CNF）上制备碳纳米纤维负载钴酞菁催化剂（CoTAPc-CNF）,利用原子吸收光谱、紫外-可见光吸收光谱、衰减全反射-红外光谱等方法对CoTAPc-CNF进行表征.选用具有氧杂蒽结构的罗丹明6G（Rh6G）为主要研究对象,研究CoTAPc-CNF对Rh6G的催化氧化性能,考察了温度、pH、NaCl、异丙醇等对CoTAPc-CNF催化性能的影响.结果表明,CoTAPc-CNF在常温中性条件下能有效催化氧化Rh6G;随着温度和pH的增加,CoTAPc-CNF催化氧化Rh6G速率逐渐提高;NaCl和异丙醇的加入,没有抑制催化氧化反应的进行,相反大大提高了Rh6G的降解速率,这与一般羟基自由基占主导的高级氧化体系完全不同;进一步采用电子顺磁共振波谱法证实CoTAPc-CNF/H2O2体系确实为非羟基自由基催化机理.另外,研究发现CoTAPc-CNF还能有效催化氧化其他共轭结构的染料,如偶氮染料酸性橙7（AO7）、三芳甲烷染料碱性绿1（BG1）.因此,本文探索的CoTAPc-CNF/H2O2非羟基自由基催化反应体系在处理成分复杂的实际印染废水中具有较好的应用前景.     

载体对Pd-Cu/活性炭催化剂在消除卷烟主流烟气中CO活性的影响

采用等体积浸渍法制备了Pd-Cu/活性炭催化剂, 用脉冲反应考察了催化剂对模拟卷烟主流烟气(4.4 CO-4.2 H₂O-19.2 O₂-72.2 He)(体积分数, %)中CO的常温催化氧化性能, 系统研究了不同的活性炭载体对催化剂的CO常温氧化活性的影响. 研究表明, 在室温条件下, 催化剂对CO氧化反应的活性顺序为: 椰壳活性炭为载体的催化剂(CAC)<木质活性炭为载体的催化剂(WAC)<超级活性炭为载体的催化剂(SAC), 并且活性炭载体对催化剂的反应诱导期也存在显著的影响. 对催化剂的表征结果表明, 不同活性炭载体表面上含氧官能团含量不同, 影响催化剂表面Pd和Cu的存在状态, 使得SAC催化剂上的Pd只以Pd²⁺形式存在, 而CAC和WAC催化剂上的Pd以Pd²⁺和Pd⁰形式存在, 导致SAC催化剂比CAC和WAC两种催化剂具有更好的CO催化氧化活性. 使用催化剂接装的三段式复合滤嘴试验卷烟, 与对照卷烟相比, 卷烟主流烟气中CO的释放量都有所降低, 其中添加SAC催化剂的效果最为明显. 如果将Pd的负载量增加为3.4% (w), SAC催化剂对卷烟主流烟气中CO的去除率高达25.4%.     

Exoemission accompanying electron interactions in complex copper-cerium oxide catalysts and synergism phenomena

The formation of the electronic structure of the surface of complex copper-cerium oxide catalysts with different copper concentrations was studied using the exoemission methods at different stages of preparation. The introduction of copper enhances the emissivity of CeO₂, and the number of charges emitted from the catalyst surface exceeds the emission activity of the starting CeO₂ and NuO components. The synergism phenomenon in exoemission is compared with synergism in the catalysis of CO oxidation by these systems. The problem of electron interactions between the components of the complex oxides is discussed. The electron interactions are caused by the electron transitions at the interface and result in an increase in both the emission of weakly bound electrons and catalytic activity in the oxidation of CO.     

预处理条件对Au/Al2O3催化CO氧化性能的影响

 采用沉积-沉淀法制备了Au/Al2O3,探讨了预处理条件对催化剂中金颗粒的大小及其催化CO氧化性能的影响,并以XRD和TEM等手段对催化剂进行了结构表征. 结果表明,还原和焙烧预处理得到的1.2% Au/Al2O3催化剂在GHSV=1.5×104 h-1时,可分别于-22和-10 ℃将空气中的1%CO完全氧化, 还原预处理所得催化剂的活性更高, 原因是催化剂中金颗粒的尺寸更小,分散度更高.     

Catalytic performance and structural characterization of ferric oxide and its composite oxides supported gold catalysts for low-temperature CO oxidation

The preparation and catalytic activity of ferric oxide and its composite oxides supported gold catalysts for low-temperature CO oxidation were investigated detailedly, and characterized extensively by XRD, XPS, TPR, EC and XAFS techniques. It was found that containing highly dispersed Au of partially oxidized state, these nano-structured oxides supported Au/Fe2O3 and Au/NiFe2O4 catalysts had higher low-temperature activities. The possible catalytic active center is the gold of partially oxidized state (Auζ+).     

Au/Fe-O催化剂活性组分在CO催化氧化反应中的存在状态

 采用传统的共沉淀法制备了Au/Fe-O催化剂,运用X射线衍射、X射线光电子能谱和透射电镜技术对其进行了表征,考察了它们对CO氧化反应的催化活性. 结果表明,虽然负载在Fe-O载体上的金晶粒较大(10～15 nm), 但由于采用了共沉淀法制备催化剂,金和载体可紧密接触并产生较强的相互作用. 催化剂中Au 5d轨道上的电子流入Fe 3d轨道,使Au 5d轨道处于非全充盈状态,金呈Auδ+状态(0＜δ＜1), 这是该催化剂具有较高催化活性的根本原因. CO催化氧化反应测试结果表明,当金含量较高时, CO的转化率在室温下就能达到100%.