Mn2O3微纳米粉体的配合物热解制备与电化学性质（英文）

利用液相扩散法制备了异烟酸锰超分子配合物,通过将其在空气中高温煅烧制备了Mn2O3微纳米粉体。利用FTIR、TG-DTA、XRD、TEM和FESEM对产物进行了表征。电化学测试表明,Mn2O3微纳米粉体在0.5 mol.L-1Na2SO4电解液中表现出良好的电化学电容特性,在电流密度为0.5 A.g-1时其单电极比容量可达到88 F.g-1,循环3 000次后容量保持率可达到80%。     

CuO/Mn2O3 /γ-Al2O3催化剂的制备、表征及其在CO氧化反应中的性能研究

采用浸渍法在γ-Al2O3载体上分步负载改性剂Mn2O3和活性组分CuO,制备了一系列不同配比的CuO/Mn2O3/γ-Al2O3催化剂,并运用CO+O2模型反应、XRF、XRD、H2-TPR、in-situ FTIR等手段表征了催化剂的活性和物理化学性质。活性测试结果表明,锰氧化物对γ-Al2O3载体的改性能有效地提高CuO/γ-Al2O3催化剂在CO+O2模型反应中的催化活性。XRD结果表明,锰氧化物对γ-Al2O3载体的改性可以促进氧化铜在载体表面的分散,从而提高了分散态氧化铜的含量,不过这与活性变化的趋势并不完全一致。进一步结合H2-TPR、in-situ FTIR表征结果 ,我们发现,分散态铜、锰氧化物的还原性质也是影响其催化活性的重要因素,催化剂中分散态铜、锰物种越容易被还原,其对CO+O2模型反应的催化活性就越高。     

CuO纳米片催化H2O2氧化降解亚甲基蓝

以十六烷基三甲基溴化铵(CTAB)为保护剂, 采用水热法成功制备了CuO纳米片. 将制备的CuO纳米片在H₂O₂存在下用于催化氧化降解亚甲基蓝, 探讨了其在不同反应条件(如温度、氧化剂浓度及催化剂用量)下对亚甲基蓝降解反应的影响. 该催化反应符合一级动力学模型, 活化能为54.0kJ/mol. CuO纳米片表现出非常高的催化活性, 但其稳定性与重复利用性有待于进一步提高.     

B2O3-Bi2O3-ZnO-Al2O3玻璃助烧剂对BaTiO3陶瓷烧结条件、晶体结构和介电性能的影响

通过调节B₂O₃-Bi₂O₃-ZnO-Al₂O₃(BBZA)玻璃的添加量研究其对钛酸钡(BaTiO₃)陶瓷烧结条件、晶体结构和介电性能的影响。结果表明：添加适量的BBZA玻璃能够有效地将BaTiO₃陶瓷烧结温度由1 350℃降至950℃,并使其致密化。同时,添加BBZA玻璃后,BaTiO₃的晶体结构随着烧结温度的升高而发生转变(立方相→四方相)。另外,BBZA玻璃的引入使BaTiO₃陶瓷的居里峰得到了有效的抑制和拓宽。陶瓷微观形貌显示,玻璃相均匀分布在BaTiO₃晶粒表面。优化的BaTiO₃陶瓷制备条件如下：BBZA添加量(质量分数)为2.0%,烧结温度为950℃。在该条件下制备的BaTiO₃陶瓷介电常数达到1 364,介电损耗低至1.2%。     

活性炭/CoFe2O4复合物的制备及其对亚甲基蓝的吸附性能

通过低温回流法制备了具有磁分离响应的活性碳(AC)与CoFe₂O₄的复合物AC/CoFe₂O₄（MAC）。采用批式吸附实验法对MAC吸附溶液中偶氮染料亚甲基蓝（MB）的吸附动力学过程及吸附平衡进行了研究,考察了溶液初始pH值对MAC吸附MB的影响。结果表明,MAC吸附MB的过程很快,20 min几乎达到平衡。MAC吸附MB过程可以用准二级动力学方程描述。等温吸附过程服从Langmuir方程,MAC对MB的饱和吸附容量为120.48 mg/g。在较低pH值时,MB吸附量较小。随着pH值的升高,MAC对MB的吸附量增大。     

Ni/Al2O3催化2-甲基呋喃加氢制2-甲基四氢呋喃性能的研究

采用浸渍法制备了不同NiO含量的Ni/Al₂O₃催化剂,并进行了2-甲基呋喃加氢制2-甲基四氢呋喃性能的考察。结果表明,在制备的NiO负载量为10%、20%、25%、30%和40%的Ni/Al₂O₃催化剂中,随着NiO负载量增加,加氢反应的选择性与2-甲基呋喃的转化率均呈现出先增加后减小的趋势。其原因是由于适当增加NiO负载量有利于催化剂表面活性中心的形成,有利于加氢反应的进行;但是过度负载的NiO容易堵塞Al₂O₃载体中的介孔通道,降低反应的转化率与选择性。在釜式反应器中进行反应,对加氢反应条件进行了优化,发现在反应压力为3 MPa、反应温度150℃、机械搅拌速率为1000 r/min时,Ni/Al₂O₃催化2-甲基呋喃加氢制2-甲基四氢呋喃具有较高的选择性。当NiO负载量为25%时,2-甲基四氢呋喃的选择性最高为97.1%,2-甲基呋喃的转化率达到99.4%。     

Ta/Al-Fe2O3薄膜电极的制备及其光电催化降解亚甲基蓝性能

采用简单的涂滴法制备出新型的Al、Ta 共掺杂的三元铁氧化物(Ta/Al-Fe₂O₃)可见光响应型光催化薄膜. 运用X射线光电子能谱(XPS)和紫外-可见(UV-Vis)光谱等手段对其进行了表征, 考察了其光电化学性能, 并研究了复合电极光电催化降解亚甲基蓝(MB)废水的反应性能. 由表面谱学分析可知, Ta 和Al 成功掺入Fe₂O₃中, Ta 会改变催化剂表面Al 和O的化学环境. 在可见光照射下的光电催化(PEC)反应中, Ta/Al-Fe₂O₃降解MB的反应速率约为Al-Fe₂O₃的2 倍, 光电催化共作用的效果优于单纯光催化作用(PC)和电催化(EC)作用的效果.结果表明, Ta掺杂有利于提高Ta/Al-Fe₂O₃薄膜的光电催化活性.     

Ce0.67Zr0.33O2对CH4燃烧催化剂Fe2O3/Al2O3的改性作用

固定n(Ce)/n(Zr)比为0.67/0.33, 用共沉淀法制得一系列CeO2-ZrO2-Al2O3固溶体. 采用这些固溶体作载体, 以Fe2O3为活性组分, 用浸渍法制备了一系列催化剂. BET结果显示, 将适量Ce0.67Zr0.33O2引入到Al2O3载体中有助于催化剂保持较高的比表面积. TPR结果显示, 载体中引入适量的Ce0.67Zr0.33O2可以改善催化剂的氧化还原性能. XRD结果表明, Fe2O3在CeO2-ZrO2-Al2O3载体上呈现出良好的分散状况, 老化前后催化剂的晶相结构基本无明显变化. 特别是当载体中m(Ce0.67Zr0.33O2)∶m(Al2O3)的值为1∶2时, Fe2O3/CeO2-ZrO2-Al2O3催化剂在甲烷催化燃烧中显示出最佳的催化性能和抗高温老化性能.     

XANES研究Al2O3包覆LiNi0.4Co0.2Mn0.4O2材料的稳定性

采用溶胶凝胶水解法在LiNi0.4Co0.2Mn0.4O2(NCM)表面包覆了0.5 wt%Al2O3.透射电镜(TEM)表明在NCM表面形成了均匀的Al2O3包覆层;分别采用恒电位极化及热重分析(TG)研究了包覆前后NCM的析氧特性;采用X射线吸收近边结构谱(XANES)研究了包覆前后O的电子结构.结果表明,包覆后的NCM析氧量更少;Al2O3包覆使得NCM表面层中与金属3d轨道杂化的O比例减少,而更稳定的、与金属4sp轨道杂化的O比例增加.这些因素导致Al2O3包覆后的NCM更加稳定、安全性更高.     

Fe2O3/TiO2纳米管阵列的制备及其光催化性能

在钛基体上采用阳极氧化法制备了TiO₂纳米管阵列,采用化学浴方法在TiO₂纳米管阵列上修饰了Fe₂O₃纳米颗粒.利用扫描电镜、X射线衍射和紫外可见漫反射光谱等手段对材料进行了表征,同时测试了材料的光电化学性能及其光催化降解亚甲基蓝染料废水的性能.结果表明,Fe₂O₃纳米颗粒的修饰将TiO₂纳米管阵列的光响应拓宽至可见光区域,提高了光电流,Fe₂O₃/TiO₂纳米管阵列的光电流是未修饰的TiO₂纳米管阵列的9倍.而在光催化反应中,亚甲基蓝最高降解率可达80%,比未修饰的TiO₂纳米管阵列高出30%.     

Highly selective oxidation of amines to imines by Mn2O3 catalyst under eco-friendly conditions

Mn₂O₃ calcined at 450 ℃ by a simple template-free oxalate route gave 96.2% selectivity of imine at 100% conversion of benzylamine. The high selectivity of the imines clearly depended on the Mn³⁺/Mn⁴⁺ ratio. The probable reaction pathway for amines oxidation catalyzed by manganese oxides was proposed for the first time. This catalytic process was carried out under milder conditions, no base additives, and air as the only oxidant.     

NiO/Mn3O4整体式催化剂催化分解臭氧的性能

将原料Ni(NO₃)₂·6H₂O、Mn₃O₄粉末和拟薄水铝石用球磨机球磨,以所得的浆料浸渍堇青石,经过焙烧,得到不同比例的NiO/Mn₃O₄催化剂。 通过催化分解臭氧活性测试发现,在空速为20000 h^-1时, 30NiO/Mn₃O₄(NiO占总质量的30%)催化剂的活性最高,臭氧分解率达到98%,催化剂活性稳定。 当提高空速为40000 h^-1,50NiO/Mn₃O₄(NiO占总质量的50%)催化剂的活性最高,臭氧分解率在90%左右,并且出现失活现象。 通过X射线衍射(XRD)、程序升温(TPR)、X射线光电子能谱分析(XPS)、BET比表面积法等表征,发现Mn₃O₄和NiO复合催化剂的比表面积大于单一金属氧化物催化剂的比表面积并且在Mn₃O₄和NiO复合催化剂中Mn₃O₄与NiO发生电子相互作用。 催化剂中的Mn₃O₄与NiO的协同催化作用。 使得Mn₃O₄与NiO混合物催化剂的还原温度降低,分解臭氧(O₃)活性提高。     

Mn3O4的溶剂热法制备及晶粒生长动力学研究

非化学计量M n3O4-δ由八面体的M n2O3-δ相与四面体的M nO相组成,结构中的氧空位是其催化活性中心[1]。M n3O4-δ用途广泛,其高催化活性可用于环保领域分解去除废气中的CO、N2O、NO与NH3等气体或从废气中去除有机物等[2~4],高纯四方相M n3O4-δ纳米晶适用于制作软磁性材料如高     

Mn_3O_4/氧化石墨烯纳米复合物的制备及其超级电容性能

利用锰前驱体与氧化石墨烯(GO)原位反应制备了Mn3O4/GO纳米复合物超级电容器电极材料;采用扫描电镜、透射电镜及X射线衍射仪分析了纳米复合物的形貌和结构;并利用交流阻抗分析及充放电测试测定了纳米复合材料的电化学性质和电容性质.结果表明,引入氧化石墨烯可增强纳米复合物的导电性及稳定性,提高Mn3O4的电容特性,从而使得纳米复合物具有较高的比电容(350F/g)和较长的循环寿命(超过1 000次).     

Solid state synthesis of lithiated manganese oxides from mechanically activated Li2CO3–Mn3O4 mixtures

The solid state formation of lithium manganese oxides has been studied from the thermal decomposition of mixtures Li₂CO₃–Mn₃O₄ with X_Li (lithium cationic fraction)=0.33 (LiMn₂O₄), 0.50 (LiMnO₂) and 0.66 (Li₂MnO₃). The analysis of the reactivity has been performed mainly by thermoanalytical (TG/DSC) and diffractometric (XRPD) techniques either on physical mixtures and on mixtures subjected to mechanical activation by high energy milling. At X_Li=0.33, the cubic lithium manganese spinel oxide (LiMn₂O₄) forms in air. TG measurements showed that the reaction starts at a considerably lower temperature in the activated mixture. By variable temperature X-ray diffraction it has been assessed that, upon mechanical activation, LiMn₂O₄ forms directly and its formation is completed within 700 °C whereas, starting from a physical mixture, the formation goes through Mn₂O₃ and is complete only at 800 °C. At T>820 °C LiMn₂O₄ reversibly decomposes to LiMnO₂ and Mn₃O₄ with an enthalpy of 30.05 kJ mol⁻¹ of LiMn₂O₄. At X_Li=0.50, by annealing under nitrogen flow for 6 h at 650 °C the activated mixture, the orthorhombic LiMnO₂ is formed. Such a formation goes through a mixture of LiMnO₂ and LiMn₂O₄. The enthalpy of LiMnO₂ solid state formation from the activated mixture has been determined to be 57.4 kJ mol⁻¹ of LiMnO₂. At X_Li=0.66 in air the mechanical activation considerably lowers the temperature within the monoclinic phase Li₂MnO₃ forms. Besides the reaction enthalpy could be determined as 40.13 kJ mol⁻¹ of Li₂MnO₃. The reaction, when performed under nitrogen flow, goes through the formation of LiMnO₂. Such a first stage of the reaction is affected by the temperature of reaction rather than by mechanical activation. The activation greatly enhances the second stage of the reaction leading from LiMnO₂ to Li₂MnO₃.     

Catalytic decomposition of H2O2 on Co3O4 doped with MgO and V2O5

The effects of doping of Co₃O₄with MgO (0.4–6 mol%) and V₂O₅ (0.20–0.75 mol%) on its surface and catalytic properties were investigated using nitrogen adsorption at −196°C and decomposition of H₂O₂ at 30–50°C. Pure and doped samples were prepared by thermal decomposition in air at 500–900°C, of pure basic cobalt carbonate and basic carbonate treated with different proportions of magnesium nitrate and ammonium vanadate. The results revealed that, V₂O₅ doping followed by precalcination at 500–900°C did not much modify the specific surface area of the treated Co₃O₄ solid. Treatment of Co₃O₄ with MgO at 500–900°C resulted in a significant increase in the specific surface area of cobaltic oxide. The catalytic activity in H₂O₂ decomposition, of Co₃O₄ was found to suffer a considerable increase by treatment with MgO. The maximum increase in the catalytic reaction rate constant (k) measured at 40°C on Co₃O₄ due to doping with 3 mol% MgO attained 218, 590 and 275% for the catalysts precalcined at 500, 700 and 900°C, respectively. V₂O₅-doping of Co₃O₄ brought about a significant progressive decrease in its catalytic activity. The maximum decrease in the reaction rate constant measured at 40°C over the 0.75 mol% V₂O₅-doped Co₃O₄ solid attained 68 and 93% for the catalyst samples precalcined at 500 and 900°C, respectively. The doping process did not modify the activation energy of the catalyzed reaction but much modified the concentration of catalytically active constituents without changing their energetic nature. MgO-doping increased the concentration of CO³⁺–CO²⁺ ion pairs and created Mg²⁺–CO³⁺ ion pairs increasing thus the number of active constituents involved in the catalytic decomposition of H₂O₂. V₂O₅-doping exerted an opposite effect via decreasing the number of CO³⁺–CO²⁺ ion pairs besides the possible formation of cobalt vanadate.     

Preparation of Mn2O3 and Mn3O4 nanofibers via an electrospinning technique

Thin PVA/manganese acetate composite fibers were prepared by using sol-gel processing and electrospinning technique. After calcinations of the above precursor fibers, Mn₂O₃ and Mn₃O₄ nanofibers with a diameter of 50-200 nm could be successfully obtained. The fibers were characterized by TG-DTA, Scanning electron microscopy, FT-IR, WAXD, respectively. The results showed that the crystalline phase and morphology of nanofibers were largely influenced by the calcination temperature.     

Fe2O3/Al2O3氧载体用于甲烷化学链燃烧：负载量与制备方法的影响

以不同方法制备了系列Fe₂O₃/Al₂O₃氧载体,采用XRD、H₂-TPR、CH₄-TPR、O₂-TPD和BET等分析技术对氧载体进行了表征。研究了不同Fe₂O₃负载量氧载体的甲烷化学链燃烧性能,考察了不同制备方法对Fe₂O₃/Al₂O₃氧载体结构、反应性和产物选择性的影响。结果表明,Fe₂O₃负载量对氧载体活性及产物中CO₂选择性的影响较大,负载量较低时氧载体活性较低且引起甲烷部分氧化产物CO含量增加。制备方法亦对氧载体与甲烷的反应活性有所影响,整体上共沉淀法制备的质量分数60％Fe₂O₃/Al₂O₃氧载体具有较高的氧化活性和化学链循环稳定性。其在反应温度850℃、反应时间15 min、30次循环后甲烷转化率及产物中CO₂选择性均未见明显降低。     

TiO2包覆对LiCo1/3Ni1/3Mn1/3O2材料的表面改性

为了提高材料LiCo1/3Ni1/3Mn1/3O2的循环性能, 采用浸渍-水解法对其进行TiO2包覆. 用X射线衍射(XRD)、电化学交流阻抗谱(EIS)、电感耦合等离子体发射光谱(ICP-OES)和恒流充放电测试研究包覆材料的结构和电化学性能. TiO2仅在材料表面形成包覆层, 并未改变材料的结构. TiO2包覆能提高材料LiCo1/3Ni1/3Mn1/3O2的倍率性能和循环性能, TiO2包覆后的材料在5.0C(1.0C=160 mA·g-1)下的放电容量达到0.2C下的66.0%, 而包覆前的材料在5.0C下的放电容量仅为其0.2C下的31.5%. 包覆后的材料在2.0C下循环12周后的容量没有衰减, 而未包覆的材料容量保持率仅为94.4%. EIS测试表明包覆材料性能的提高是由于循环过程中材料的界面稳定性得到了提高. 循环后材料的XRD和ICP-OES测试表明, 包覆层能提高材料LiCo1/3Ni1/3Mn1/3O2的结构稳定性.     

Oxidative dehydrogenation of propane over Mo/g-Al2O3. effect of precursor

Alumina supported molybdenum oxide was prepared using ammonium heptamolybdate and molybdenum acetate as different precursors. The catalysts were characterized by BET, AAS, SEM-EDAX, XRD, TPR and surface acidity measurements. The characterization results and the catalytic behavior in oxydehydrogenation of propane were similar irrespective of precursor. This revised version was published online in August 2006 with corrections to the Cover Date.