负载型CuO/TiO2催化剂催化CO2加氢制甲醇

采用浸渍法制备了CuO/TiO_2负载型催化剂,并将其用于CO2加氢制甲醇反应。重点考察了铜的负载量对催化剂性能的影响,并对其物化性能和催化性能之间的关系进行了讨论。结果发现,随着铜负载量的增加,催化剂中金属铜的比表面先增加后减小,当铜的负载量为10%(质量百分数)时达到最大值。催化剂的表面碱性位数量随铜含量的增加持续减小,中等碱位和强碱位的强度下降。当铜的负载量不高于10%时,CO2的转化率与铜的比表面积呈线性关系。甲醇选择性与催化剂的表面碱位性质有关,过强的碱性位会降低甲醇选择性。     

Kinetics of methane combustion on Fe2O3/TiO2 catalysts

The objective of this work was to study the kinetics of methane combustion for a series of Fe₂O₃/TiO₂ catalysts. An increase in activity is observed as iron loading increases, and can be attributed to an increase of surface coverage by Fe₂O₃ species. Kinetic studies revealed that the reaction orders with respect to methane, oxygen, carbon dioxide and water are 1, 0, 0 and -1 respectively. This revised version was published online in June 2006 with corrections to the Cover Date.     

负载型CuO/TiO2催化剂催化CO2加氢制甲醇

采用浸渍法制备了CuO/TiO₂负载型催化剂,并将其用于CO₂加氢制甲醇反应。重点考察了铜的负载量对催化剂性能的影响,并对其物化性能和催化性能之间的关系进行了讨论。结果发现,随着铜负载量的增加,催化剂中金属铜的比表面先增加后减小,当铜的负载量为10%（质量百分数）时达到最大值。催化剂的表面碱性位数量随铜含量的增加持续减小,中等碱位和强碱位的强度下降。当铜的负载量不高于10%时,CO₂的转化率与铜的比表面积呈线性关系。甲醇选择性与催化剂的表面碱位性质有关,过强的碱性位会降低甲醇选择性。     

Novel Bi2MoO6 Nanosheets/Vertical TiO2 Nanorods Arrays Heterojunction with Enhanced Photoelectrochemical Performance under Visible Light Irradiation

Novel Bi₂MoO₆/TiO₂ heterojunction was fabricated by growing Bi₂MoO₆ nanosheets arrays on the vertically aligned TiO₂ nanorods arrays via a two-step solvothermal method. The obtained Bi₂MoO₆/TiO₂ hierarchical heterojunction showed excellent visible light photoelectrochemical performance. Compared with the pure TiO₂ and Bi₂MoO₆, the photocurrent density of the heterojunction was increased 57 and 29 times, respectively. Furthermore, the hydrogen generation rate of the Bi₂MoO₆/TiO₂ for photoelectrocatalytic water-splitting was about 6 times higher than that of the pure Bi₂MoO₆. The improved performance can be attributed to the synergistic effects of enhanced absorption of visible light, increase of migration rate and separation efficiency of photo-induced carriers.     

TiO2晶相对MnOx/TiO2催化剂催化NO氧化性能的影响

以浸渍在不同晶相TiO₂ （金红石型（R）、锐钛矿型（A）和P25型（P））上的锰基催化剂为对象,研究了TiO₂晶相对MnO_x/TiO₂催化剂催化NO氧化活性的影响。 结果表明,MnO_x/TiO₂（P）催化剂活性最高,NO转化率在300℃及GHSV = 20000 h^-1条件下可达83%。 各催化剂活性顺序为MnO_x/TiO₂（P）>MnO_x/TiO₂（A）>MnO_x/TiO₂（R）。采用X射线粉末衍射、场发射扫描电子显微镜、X射线光电子能谱、H₂程序升温还原和O₂程序升温脱附等手段研究了TiO₂晶相影响MnO_x/TiO₂催化剂催化活性的作用机理。结果表明,相比于A和R型TiO₂,P型TiO₂能够增加MnO_x在其表面的分散度并抑制催化剂颗粒的团聚和粘连,且更有利于Mn₂O₃的生成,而后者催化NO氧化活性比其它MnO_x更高;此外,P型TiO₂可以增加MnO_x尤其是Mn₂O₃的还原性,并可促进O₂^-从M³⁺-O键的脱附。     

Oxidative dehydrogenation of propane over chromium and nickel oxide modified V2O5/ZrO2 catalysts

The effect of addition of chromium and nickel oxides on the physicochemical properties and performance of V₂O₅/ZrO₂ catalysts was studied for the oxidative dehydrogenation of propane. Addition of chromium oxide increased, whereas addition of nickel oxide lowered the activity. Selectivity for propene was lower for the doped catalysts. The selectivity was lowered by higher total acidity as well as the higher concentration of stronger acid sites in doped catalysts.     

Catalytic combustion of chlorobenzene over V2O5/TiO2 catalysts prepared by the precipitation-deposition method

Catalytic combustion of chlorobenzene over supported vanadium oxides has been investigated. TiO₂ was prepared by the sol-gel method from titanium isopropoxide. The supported vanadium oxide catalysts have been prepared by precipitation-deposition and impregnation method and characterized by XRD, FT-Raman and TPR. In the VO_x/TiO₂catalysts prepared using the impregnation method, when vanadium loading reaches 3 wt.%, the activity shows a maximum. However, in the VO_x/TiO₂catalysts prepared by precipitation-deposition, when vanadium loading reaches 7 wt.%, the activity shows a maximum. This result suggests that the precipitation-deposition can yield a higher metal loading on the support and a high dispersion compared to the impregnation method. This revised version was published online in August 2006 with corrections to the Cover Date.     

CrOx/SiO2催化剂上丙烷在CO2气氛中脱氢反应的研究

采用XRD、UV-vis DRS、ESR和微分吸附量热等技术,考察了铬担载量分别为2.5、5和10wt%的CrO_x/SiO₂催化剂的结构、表面性质和氧化还原性能。结果表明,催化剂表面上存在多种Cr的氧化态和聚集形式。随着Cr担载量从2.5wt%到10wt%的逐渐增大,催化剂表面占主导地位的Cr物种由CrO₃单体转为多聚CrO₃和Cr₂O₃晶相。在CO₂气氛中催化剂对丙烷转化率和丙烯选择性的大小顺序为2.5wt%CrO_x/SiO₂>5wt%CrO_x/SiO₂>10wt%CrO_x/SiO₂,反应过程中的原位ESR和UV-visDRS测定结果表明,催化剂表面的反应活性中心为Cr⁵⁺,Cr⁵⁺可由催化剂预处理过程中Cr³⁺的氧化及丙烷反应过程中CrO₃单体的还原产生,在反应中CO₂可使Cr³⁺重新氧化为Cr⁵⁺.     

Sunlight-activated AlFeO3/TiO2 photocatalyst

A nanocomposite photocatalyst composed of AlFeO₃ and TiO₂ is prepared, and characterized through X-ray diffraction. Application of the nanocomposite for the photodegradations of eosin dye and methyl orange gives an improved photoactivity compared with TiO₂-only nanomaterials. The optimal concentration of AlFeO₃ in the composite is about 1.0 wt% under UV excitation, and 9.0 wt% under sunlight excitation for the improved photoactivity. Furthermore, this nanocomposite is more active for eosin photodegradation if natural sunlight rather than UV is used. This may be due to the reason that adding AlFeO₃ nanoparticles into TiO₂ matrix can promote the separation of photogener-ated charge carriers, and extend the photoresponse of TiO₂ toward visible region, which results in an increase in the solar energy utilization efficiency.     

Radiation-induced synthesis of Fe-doped TiO2: Characterization and catalytic properties

Fe-doped TiO₂ catalyst was prepared by wet impregnation, using TiO₂ P25 Degussa as a precursor and Fe(NO₃)₃ as a dopant, followed by irradiation with an electron beam or γ-rays. Surface properties of Fe/TiO₂ samples were examined by BET, XRD, ToF-SIMS, and TPR methods. The photocatalytic activity towards destruction of the anionic surfactant, sodium dodecylbenzenesulfonate (SDBS), in aqueous solutions was higher for the irradiated Fe/TiO₂ catalysts than for bare TiO₂ P25 or that calcined at 500 °C. The results show that irradiated catalysts exhibit a more uniform texture with high dispersion of iron species. An enhancement of the activity of irradiated Fe/TiO₂ systems can be attributed to the synergetic effects of small crystallite size and homogenous distribution of iron species including FeTiO₃ phase.     

Oxidative dehydrogenation of propane on TiO2-supported chromium and zinc oxides

Oxidative dehydrogenation of propane has been studied on chromium, zinc and zinc-chromium mixed oxides supported on anatase titania. The order of activity and selectivity to propene was CrTi>ZnCrTi>ZnTi. The activity and selectivity to propene did not change markedly with increase in the reaction temperature.     

WO3/TiO2 catalysts: Morphological and structural properties

Titania-supported tungsten oxide catalysts with different W loadings up to 9 wt. % and calcined at different temperatures have been prepared and characterized. It is found that W hinders the initial sintering of anatase, providing thermal stability. The interaction of W with TiO₂ and the amount of hydroxy groups present on the surface can limit diffusion, thus reducing the sintering rate.     

Ce掺杂Bi2MoO6/TiO2纳米纤维异质结的制备及可见光催化性能

以静电纺丝技术制备的TiO₂纳米纤维为基质,通过溶剂热法制备了异质结型稀土Ce掺杂Bi₂MoO₆/TiO₂复合纳米纤维。利用X射线衍射（XRD）、扫描电子显微镜（SEM）、X射线光电子能谱（XPS）、透射电镜（TEM）、紫外-可见漫反射光谱（UV-Vis DRS）以及荧光光谱（PL）等分析测试手段对样品的物相、形貌和光学性能等进行表征。以罗丹明B为模拟有机污染物,研究了样品的可见光催化性能。结果表明：在稀土掺杂样品中,Ce离子进入Bi₂MoO₆晶格,部分取代Bi³⁺,导致晶胞膨胀,晶格畸变,形成缺陷;与TiO₂复合形成异质结,有利于光生电荷的产生、转移和有效分离,从而提高TiO₂纳米纤维的光催化活性。可见光照射180 min,罗丹明B的降解率达到95.1%。经5次循环光催化降解活性基本不变,样品具有良好的光催化稳定性。     

Ce掺杂Bi2MoO6/TiO2纳米纤维异质结的制备及可见光催化性能

以静电纺丝技术制备的TiO_2纳米纤维为基质,通过溶剂热法制备了异质结型稀土Ce掺杂Bi_2MoO_6/TiO_2复合纳米纤维。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、透射电镜(TEM)、紫外-可见漫反射光谱(UV-Vis DRS)以及荧光光谱(PL)等分析测试手段对样品的物相、形貌和光学性能等进行表征。以罗丹明B为模拟有机污染物,研究了样品的可见光催化性能。结果表明:在稀土掺杂样品中,Ce离子进入Bi_2MoO_6晶格,部分取代Bi3+,导致晶胞膨胀,晶格畸变,形成缺陷;与TiO_2复合形成异质结,有利于光生电荷的产生、转移和有效分离,从而提高TiO_2纳米纤维的光催化活性。可见光照射180 min,罗丹明B的降解率达到95.1%。经5次循环光催化降解活性基本不变,样品具有良好的光催化稳定性。     

贵金属负载TiO2对光催化还原CO2选择性的影响

利用光沉积方法在TiO₂表面分别负载1%(质量分数) Pt、Pd、Au和Ag助催化剂.用TEM、XRD、UV-vis等技术对催化剂进行了表征,并利用连续瞬态电流时间响应和线性扫描伏安法等电化学方法,对贵金属负载的TiO₂光催化剂在光照条件下的电流响应强度及电催化析氢电位等特性加以测试.分析了贵金属助催化剂对光催化还原CO₂性能的差异.结果表明,负载贵金属助催化剂能显著加速光生电子空穴的分离,降低复合率;另外,助催化剂对还原CO₂选择性的顺序为Ag>Au>Pd>Pt.贵金属助催化剂还原CO₂的加氢选择性和析氢过电位存在相关性,即越不利于析氢过程的助催化剂,其催化CO₂加氢还原产物的选择性越高.     

Catalytic oxidation of no to NO2 over Cr/TiO2 and Cu/TiO2 under oxidizing atmosphere

The catalytic activity of Cr/TiO₂ and Cu/TiO₂ for the oxidation of NO under an oxidizing atmosphere has been examined. Both catalysts had excellent ability for the oxidation of NO to NO₂ in the temperature range of 350–400°C.     

The influence of La2O3 and TiO2 on NiO/MgO/α-Al2O3

Summary The effect of La₂O₃ and TiO₂ on product selectivity, methane conversion and coke formation over NiO/MgO/ α -Al₂O₃ catalyst were studied in a simultaneous steam and CO₂ reforming of methane to syngas. La₂O₃ and TiO₂ were added to the catalyst via incipient wetness impregnation and bulk precipitation techniques and catalyst activity was tested in a fixed bed quartz reactor. Results reveal that although the addition of these oxides has no effect on the product selectivity and methane conversion, but can reduce coke formation on the surface of the catalysts as it can enhance the mobility of lattice oxygen anions. The results further show that the catalysts prepared by bulk precipitation technique decrease the coke formation more effectively.     

Catalytic reduction of nitrogen monoxide with propene over Nb/TiO2 mixed mechanically with Mn2O3

Selective catalytic reduction of nitrogen monoxide (NO) over a catalyst of mechanically mixed Nb/TiO₂ and Mn₂O₃ (Mn₂O₃+Nb/TiO₂) in an oxidizing atmosphere with propene (C₃H₆) was studied. The Mn₂O₃+Nb/TiO₂ catalyst showed high activity for the reduction of NO to N₂. The maximum conversion of NO to N₂ was observed at 200∼300°C, with about 80% reduction of NO to N₂. Mn₂O₃ enhanced the formation of NO₂ from NO and the activation of propene to react with NO₂ for reduction to N₂.     

纳米TiO2-SiO2复合光催化剂的超临界流体干燥法制备及其光催化性能研究

本文以廉价无机盐Na₂SiO₃·9H₂O和TiCl₄溶液为原料,采用化学包覆结合超临界流体干燥(SCFD)法制备纳米级TiO₂-SiO₂复合光催化剂。利用XRD、TEM、NMR等手段对复合粉体进行了表征。结果表明,采用超临界流体干燥法可直接制得锐钛矿型TiO₂-SiO₂纳米复合光催化剂,其中SiO₂以单分散、无定形形式存在。以苯酚和邻苯二酚紫光催化降解为反应模型,考察了TiO₂-SiO₂复合光催化剂的催化性能。证明掺入适量SiO₂的TiO₂-SiO₂纳米复合光催化剂既减少了TiO₂的用量、降低了成本,又在某种程度上提高了TiO₂的光催化活性。SiO₂的引入可以有效抑制纳米粒子粒径的长大和晶相的转变,增强了二氧化钛纳米粒子的热稳定性。二氧化硅的最优掺杂量为15%(质量分数)。     

高热稳定性纳米Au/TiO2催化剂的制备与表征

 采用三嵌段共聚物聚乙醚-聚丙醚-聚乙醚EO20PO70EO20 (P123)为有机模板剂合成了介孔TiO2载体,用沉积-沉淀法制得Au/TiO2催化剂. 运用N2 吸附-脱附、 X射线衍射、 X射线光电子能谱和高分辨电镜技术对催化剂的结构与形貌进行了表征. 采用P123模板剂合成的TiO2具有较均匀的介孔结构,孔径集中在6.1 nm附近,负载金后,其介孔结构保持良好,但孔径下降至5.4 nm. 400 ℃焙烧后,介孔TiO2负载的Au催化剂中Au主要以金属态存在. 负载在三种TiO2载体(介孔TiO2、溶胶-凝胶法合成的TiO2和工业TiO2)上的Au晶粒大小和分散度差异较大,其中介孔TiO2载体更有利于金的分散,以该载体制备的催化剂400 ℃焙烧后金的晶粒尺寸在1～5 nm范围内,催化剂显示了很好的CO氧化活性和抗热稳定性,即使在420 ℃焙烧,其室温下CO的转化率也在90%以上. 而溶胶-凝胶法制备的TiO2和工业TiO2负载的纳米金催化剂中,金晶粒尺寸约为10 nm,催化剂的CO氧化活性和抗热稳定性较差.