TiO2-Fe2O3氧化物阴极的制备工艺研究

FFC(熔盐电脱氧)工艺是一种用电化学还原法从混合金属氧化物制备Ti-Fe合金的新工艺,具有短流程、低能耗的特点。选择合适的阴极制备工艺对后续的电化学还原至关重要。采用模压成型和烧结的工艺制备TiO2-Fe2O3混合氧化物阴极,研究了阴极片的成型压力、造孔剂种类及用量、烧结温度等阴极成形和烧结过程中的主要因素对阴极孔隙率和微观结构的影响。用SEM及EDS对阴极片的微观结构和元素分布进行分析。结果表明,用碳酸氢氨作造孔剂时,阴极片的孔隙率受温度的影响较大;随着温度的升高和造孔剂含量的增多,烧结的阴极片颗粒直径不断增大,并且在孔隙周边的颗粒直径相对于其他部位要更大些;随着温度的等幅度增加,颗粒直径在造孔剂含量高时随温度升高而增长的幅度较大。对烧结片局部氧元素含量分布不均的现象进行了分析,其原因是高温下物质的内能较高,当能量达到反应活化能时会发生氧化物的分解反应,分解出的氧气通过孔隙向周围扩散,使得局部的氧含量较高。     

Fe2O3转变为Fe3O4粉末的微波碳热还原

以活性炭为还原剂及以氩气为保护气,采用微波碳热还原的方法,将弱磁性的Fe₂O₃还原成强磁性的Fe₃O₄,并研究焙烧温度、保温时间以及SiO₂粉末的加入对其还原焙烧成分及磁化效果的影响规律.结果表明:在配碳量一定的条件下,焙烧温度是微波碳热还原的关键因素,随着温度的升高,还原产物中Fe₃O₄的含量发生有规律的变化;650℃、保温5 min的条件下经微波还原后生成了纯Fe₃O₄粉末,其磁化率和还原度分别达到理论值2.33和11.11%;含SiO₂的Fe₂O₃粉末在750℃以上进行微波还原,会生成大量的硅酸亚铁和氧化亚铁,导致Fe₃O₄含量降低,恶化还原焙烧指标,所以微波磁化焙烧的最佳温度应在570~650℃.     

含Li催化剂和添加剂对Fe2O3还原反应的影响

通过还原试验,研究了LiCl与含Li催化剂对Fe₂O₃的CO还原作用,发现不论是LiCl还是含Li催化剂均对Fe₂O₃的CO还原有催化作用,其中以含Li催化剂对Fe₂O₃的CO还原催化效果最好.用X-rar鉴定含Li催化剂的物相,主要以α-Fe和FeO相存在,说明了含Li催化剂中的α-Fe亦对Fe₂O₃的CO还原有催化作用.     

等离子喷涂Sc2O3、Gd2O3和Y2O3复合稳定ZrO2热障涂层相稳定性及导热性研究

采用化学共沉淀-煅烧法制备了Sc2O3、Gd2O3和Y2O3复合稳定ZrO2陶瓷原粉,陶瓷原粉经球磨、团聚造粒和烧结处理后得到适于等离子喷涂工艺的热喷涂粉末。测试分析了Sc2O3、Gd2O3和Y2O3复合稳定ZrO2热喷涂粉末微观形貌、流动性及其等离子喷涂涂层的相稳定性及导热性。结果表明Sc2O3、Gd2O3和Y2O3复合稳定ZrO2材料及其等离子喷涂涂层具有优异的高温相稳定性,即使在1400℃热处理500小时依然呈四方相结构、无单斜相出现,涂层热导率比单一Y2O3稳定ZrO2涂层明显降低,Sc2O3、Gd2O3和Y2O3复合稳定ZrO2可以用作新型超高温热障涂层材料。     

含碳高硅矿球团在H2-H2O-N2和CO-CO2-N2气氛下还原过程研究

针对高炉炼铁节能减排的新要求,在H₂-H₂O-N₂和CO-CO₂-N₂气氛下研究碳复合团块的反应行为。通过化学分析法、X射线衍射(XRD)和扫描电子显微镜-能谱(SEM-EDS)分析了复合团块的成分、矿相及微观形貌,对CO-CO₂-N₂和H₂-H₂O-N₂气氛下碳复合团块的还原行为进行了分析,并建立了复合团块反应动力学模型。结果表明,在1 073、1 173、1 273、1 373 K温度下,复合团块在H₂-H₂O-N₂气氛下的还原度和碳气化率均高于CO-CO₂-N₂气氛。对2种气氛下含碳团块在1 273 K时的反应过程进行分析,XRD图谱表明,在H₂-H₂O-N₂气氛下反应20 min后,团块中...     

CeO2-SiO2复合氧化物的制备及性能表征

化学沉淀法制备了SiO2和CeO2以及复合氧化物CeO2-SiO2等纳米粉体。对粉体的形貌及物相结构、粒径大小通过TEM及XRD进行了检测分析。SiO2粉体为无定形结构,粒径约500 nm,立方萤石型结构的CeO2及复合氧化物CeO2-SiO2的平均粒径小于10 nm,说明复合氧化物的合成过程抑制了粒径的长大。制备了SiO2/CeO2质量比分别为5%、10%、15%、20%的复合氧化物,煅烧温度为400℃～1000℃,结果显示随着SiO2比例的增加,CeO2的特征峰在逐渐减弱,半高宽变宽,粒径变小;随着煅烧温度的升高,特征峰强度增加,半高宽变窄,颗粒的晶型发育越来越完善,但样品的粒径变大。     

白云鄂博稀土尾矿催化CO还原NO实验研究

针对稀土尾矿催化CO还原NO进行实验研究。实验结果表明,稀土尾矿能有效催化还原NO,且脱硝率随着反应温度的升高和碳氮比的增加而增加。稀土尾矿在中高温段的脱硝率高于纯物质CeO₂、Fe₂O₃、Fe₂O₃/CeO₂和5Fe₂O₃/CeO₂;H₂-TPR测试表明,稀土尾矿在800℃以上出现的还原峰也高于这4种纯物质。XRD分析表明稀土尾矿的主要矿相在脱硝反应前后没有变化,但各矿相特征峰的强度下降,氟碳铈矿特征峰消失。SEM图像显示脱硝反应后稀土尾矿中出现裂缝和孔隙。EDS分析表明,稀土尾矿单一颗粒中存在多种金属元素的重叠区。XPS分析结果表明稀土尾矿脱硝后Fe³⁺和Ce³⁺的比例增加。当反应温度为900℃,碳氮比为4∶1时,稀土尾矿的脱硝率为98%。     

Fe2O3团粒还原制备中空铁颗粒

采用喷雾造粒制备Fe2O3空心球团粒,团粒经过氢气还原得到中空Fe颗粒,通过扫描电镜(SEM)观察Fe2O3空心球团粒及其截面的形貌,研究还原时间对Fe颗粒形貌与截面形貌的影响;采用激光衍射粒度分析仪对Fe颗粒进行粒径分析;采用比表面及孔隙度分析仪表征Fe颗粒的比表面积;采用CSM-MCT显微硬度仪测量空心球状Fe颗粒球壁的硬度和弹性模量。结果表明:Fe2O3空心球团粒和Fe颗粒均为多孔中空球状结构,球壁上存在大量微孔,中空孔直径和球颗粒直径的比值在0.4～0.5;在650℃下还原,随着还原时间增加(4,5,6 h),球壁晶粒逐步长大,中空球状Fe颗粒的比表面积和粒径逐步减小,球壁趋向致密,硬度和弹性模量提高。     

Catalytic combustion of toluene on Pt/Al2O3 and Pd/Al2O3 catalysts with CeO2,CeO2-Y2O3 and La2O3 as coatings

CeO₂,La₂O₃,and CeO₂-Y₂O₃ oxides were coated on the surface of spherical granular AI₂O₃(3-5 mm)through impregnation method,and proved as better supports of Pd and Pt catalysts.The influences of rare earth metal doping on the adsorption rates of Pd and Pt ions,as well as the catalytic performance,were investigated.Results show that the H₂PtCl₆·6H₂O adsorption rates of the Al     

Pt涂层蜂窝金属和Ce改性Fe2O3催化CO的性能对比

铁矿石烧结烟气中含有较高浓度的CO（体积分数0.5%～2%）,因此对其进行CO脱除意义重大。为了探究不同类型催化剂的催化效果,采用浸渍法制备了Pt涂层蜂窝金属催化剂和铁铈氧化物催化剂,并通过X射线荧光光谱分析（XRF）对其组分含量进行了分析。二者在模拟烧结烟气中进行CO脱除性能的对比实验,活性测试表明,不同CO初始体积分数、烟气温度以及水汽含量对CO催化氧化的脱除效率影响较大。当模拟烟气中不含水汽的时候,二者在180 ℃及更高温度下对CO的脱除效率均能达到60%以上。反应温度为180 ℃,水汽体积分数为11.7%时,Pt负载型催化剂中的CO转化率为63.9%,而该条件下Ce改性Fe₂O₃催化剂的CO转化率仅为34.9%。当温度在180～300 ℃范围内,Pt负载型催化剂具有较好的抗水性,且继续升高温度,水汽体积分数增加对催化剂效率的负面影响更显著。如水汽体积分数从0增加到27.1%时,与180 ℃时的催化效率相比,Pt负载型催化剂在240 ℃时的催化效率由73.9%降至62.3%,降幅远远增大。另外,对这两种催化剂进行了抗硫性测试。当水汽体积分数为0时,Ce改性Fe₂O₃催化剂抗硫性更佳,但当SO₂和水汽同时存在的情况下,Pt负载型催化剂具有更好的抗硫性。因此,在实际烧结中建议采取高效的脱硫措施并布置脱水层以减少其对于催化剂的负面影响。      

Study on ceria-modified SnO2 for CO and CH4 oxidation

Sn-Ce-O binary catalysts with different Sn/Ce molar ratios were prepared with co-precipitation method and applied for CO and CH4 oxidation. The catalysts were characterized by means of N2-BET, XRD and H2-TPR techniques. It was found that for those Sn rich samples such as SnCe91 and SnCe73, Ce cations were doped into the matrix of tetragonal rutile SnO2 to form SnO2 -based solid solution. As a consequence, the oxidation activity as well as the thermal stability was significantly improved compared with pure SnO2 . In contrast, for Ce rich samples such as SnCe19, SnCe37 and SnCe55, though the thermal stability was improved, the activity was worse than SnO2,due to the presence of much less amount of active oxygen species. Co-precipitation was found to be the best method to prepare Sn-Ce binary catalysts among all of the methods tried in this study.     

Catalytic Partial Oxidation of Methane over Ni/CeO2-ZrO2-Al2O3

Nickel catalysts supported on CeO2-ZrO2-CeO2,ZrO2-Al2O3 and Al2O3 were prepared and characterized by means of X-ray diffraction（XRD）,BET areas,H2 temperature-programmed reduction（H2-TPR）,and X-ray photoelectron spectroscopy（XPS）.Through the test of catalytic partial oxidation of methane（CPOM）,Ni/CeO2-ZrO2-Al2O3 displayed the highest activity,which resulted from its largest BET area and best NiO dispersion.Furthermore,Ni/CeO2-ZrO2-Al2O3 maintained a long-time stability in CPOM,which was attributed to its best coking resistance among all the prepared catalysts.     

Effect of Fe2O3 Loading Amount on Catalytic Properties of Monolithic Fe2O3/Ce0.67Zr0.33O2 -Al2O3 Catalyst for Methane Combustion

Ce0.67Zr0.33O2-Al2O3 solid solution was prepared by the co-precipitation method. Fe2O3-based catalysts supported on the solid solution were obtained by the impregnation method. The article revealed that the optimal loading amount of Fe2O3 on Ce0.67Zr0.33 O2-Al2O3 in our experimental condition for catalytic combustion of methane was 8% （ mass fraction）. The prepared catalysts were characterized by BET, TPR, XRD analyses, and their catalytic activity was investigated after being calcined at 873 K and after being aged in water gas at 1273 K. When the loading amount of Fe203 was 8% （ mass fraction）, the catalyst held the highest activity, and the best temperature speciality and thermal stability. The complete-conversion temperature of methane for fresh and aged sample was 788 and 838 K, respectively. The range between the light-off temperature and the complete-conversion temperature was only 15 K. The characterization results of XRD indicated that Fe2O3 was well dispersed on the Ce0.67Zr0.33O2-Al2O3 matrix. The results of BET and TPR were in good harmony with the catalytic activity results.     

FeTiO3--Fe2 O3固溶体等温碳热还原

基于粉末煅烧技术合成FeTiO₃和FeTiO₃-Fe₂O₃固溶体体系,在热力学分析的基础上,选取1150℃,以固溶体合成物为原料研究FeTiO₃-Fe₂O₃固溶体体系等温碳热还原过程,并采用X射线衍射仪和扫描电镜-能谱仪对还原产物进行系统分析.研究结果表明:合成产物内部成分均匀.钛铁矿的摩尔分数x越小,xFeTiO₃-(1-x) Fe₂O₃固溶体碳热还原反应越易进行,并且反应速率最大值越大.在反应初期,假板钛矿相(FeTi₂O₅-Fe₂TiO₅(Fe₃Ti₃O₁₀))作为过渡相一直存在,至金属Fe和钛铁晶石Fe₂TiO₄生成后逐渐消失.      

Ln2O3／ZrO2催化合成DOP、DOM和DOA

采用共沉淀－焙烧法制成的Ln2O3/ZrO2(Ln=Nd、Sm、Er)担载型催化剂，由于比表面增大，分散性好，在催化合成DOP、DOM和DOA中效果明显，且Ln2O3的用量比用纯Ln2O3催化剂下降60％左右。     

Ce_xTi_(1-x)O_2 Mixed Oxides Supported CuO Catalyst for NO Reduction by CO

Uptodate ,numerousstudieshaveshownthatrareearthoxidesaretheexcellentstructuralandelec tronicpromoterstoimprovetheactivity ,selectivityandthermalstabilityofcatalysts[1,2 ] .Themostwidelyappliedrareearthoxideinindustrialcatalysisiscer tainlyCeO2 .However ,amajordrawbackofCeO2 isthelossofoxygenstoragecapability (OSC)duetoitssinteringathighertemperature (>75 0℃ ) ,whichleadstothedeactivationofthecatalyst[3 ,4] .Oneap proachpreviouslyusedtostabilizeceriaagainstsinter ingwastodopeitwithotheranti…     

高铁赤泥制备CaO-SiO2-Fe2O3-Al2O3系微晶玻璃

以高铁赤泥、SiO₂等成分为原料,通过熔融-热处理法制备CaO-SiO₂-Fe₂O₃-Al₂O₃体系的赤泥基微晶玻璃.表征母玻璃和热处理后的微晶玻璃的物相组成、微观形貌,计算结晶度以及测试抗弯强度性能等.通过Rietveld全谱拟合方法对各组微晶玻璃的结晶度进行计算,对比分析发现,热处理后微晶玻璃的结晶度增加,随着SiO₂的添加会使得微晶玻璃的结晶度降低.对微晶玻璃进行抗弯强度测试,抗弯强度随着SiO₂/赤泥的增加而增大.      

Effect of CeO2 nanoparticle sizes on catalytic performances of sulfated CeO2/Al2O3 catalyst in NH3-SCR reaction

The sulfated CeO₂/Al₂O₃ catalysts with different sizes of CeO₂ nanoparticles were prepared by using pure H₂O or acetic acid solution as impregnation solvent, and the influence of sizes of CeO₂ nanoparticles on the catalytic performances of the sulfated CeO₂/Al₂O₃ catalyst was studied. The catalytic performance tests show that the sulfated CeO₂/Al₂O₃ catalyst using a...     

A rationale for the development of thermally stable nanostructured CeO2-ZrO2-containing mixed oxides

CeO2-ZeO2 solid solutions are extensively used as oxygen storage promoters in the current automotive three-way catalysts. High thermal stability of the textural properties is one of the most important requirements for practical application since temperatures up to 1273 K are easily experienced by these materials under real working conditions. In the present paper, we investigated how hydrothermal treatments applied to cakes of doped and undoped ZrO2-rich CeO2-ZrO2 precursors might improve the thermal stability of the final CeO2-ZrO2 solid solution. A rationale was developed that allowed to correlate the morphology of the hydrothermaUy treated cake with the thermal stability at 1273 K of the final product, which did not depend on the composition of the mixed oxides.