铈锆氧化物固溶体对全钯三效催化剂性能的影响

铈锆氧化物固溶体对全钯三效催化剂性能的影响     

Ce-Zr-O固溶体的制备和表征

采用硝酸盐直接分解法、共沉淀法、苹果酸溶胶 凝胶法和柠檬酸溶胶 凝胶法制备了Ce Zr O复合氧化物并进行了表征。溶胶 凝胶法制得的Ce Zr O为立方的Ce0 .5Zr0 .5O2 复合氧化物 (其中少量具有立方性质的t″相 ) ,而直接分解和共沉淀法制得的是由立方Ce0 .8Zr0 .2 O2 和四方Ce0 .2 Zr0 .8O2 固溶体组成的复合氧化物。不同制备方法制得的样品由于物相组成不同 ,还原性能也有较大差别。差热分析和X射线衍射分析结果表明 ,凝胶在燃烧的同时生成了Ce0 .5Zr0 .5O2 固溶体。     

用Pr修饰的(Ce-Zr)O2固溶体在三效催化剂中的作用

采用溶胶－凝胶法制备了三效催化剂助剂（Ce-Zr)O2,(Pr-Ce-Zr)O2和（Pr-Zr)O2，并对它们进行了XRD，EXAFS和BET比表面的测定，采用H2的程序升温还原（TPR）表征该类助剂的还原特征，以考察此类含有镨的混合氧化物作为三效催化剂储氧组分的可能性。在≥800℃高温时，（Pr-Zr)O2形成了立方相固溶休，并且变得更容易被还原，含少量Pr的三元固溶体（Pr-Ce-Zr)O2在其还原过程中起着重要的作用，也具有易被还原的重要特性，测量了含有Pt,Pd和Rh的三次催化剂活性，即固定反应气氛组成（S＝1.00）时CO，C3H6和NOx转化的起燃温度。结果表明，在（Ce-Zr)O2固溶体中加入少量的镨可使得C3H6和NOx转化的起燃温度降低，所有含镨的催化剂对NOx转化均表现出较高的活性，并且在富氧区（S≥1.00）具有更大的S值宽度。     

固体强酸催化剂S_2O_8~(2-)/ZrO_2-Al_2O_3-M_2O_3(M=Cr,Ce,La)的制备

固体强酸具有酸强度高 ,不腐蚀设备 ,不污染环境 ,与产物分离方便等特点 ,是一种对环境友好的催化剂。业已发现固体强酸对许多重要的有机反应如烃类异构化、傅克酰基化、傅克烷基化、酯化、缩合、聚合、氧化等具有良好的催化活性 ,可替代传统的浓 H2 SO4 及 Al Cl3、HF等高污染催化剂。在前文 [1]基础上 ,本文通过添加 Cr2 O3、Ce2 O3和 La2 O3对催化剂 S2 O2 - 8/Zr O2 - Al2 O3改进后制备出 S2 O2 - 8/Zr O2 -Al2 O3- M2 O3( M=Cr,Ce,La)系列固体强酸催化剂 ,用对乙酸和正丁醇的酯化转化率评价了催化活性 ,用 XRD、BET、流…     

Ce0.5Zr0.5O2修饰的Ni/SiC、Fe/SiC和Co/SiC催化燃烧甲烷性能

以铈锆固溶体(Ce0.5Zr0.5O2)修饰的高比表面积SiC为载体,采用两步浸渍法制备了Ni、Fe和Co基催化剂,研究了其在煤层气催化燃烧脱氧中的催化活性和稳定性.利用X射线衍射(XRD)、X射线光电子能谱(XPS)、电感耦合等离子体质谱(ICP-MS)、高分辨透射电子显微镜(HRTEM)、比表面积(BET)、热重分析(TGA)和H2程序升温还原(H2-TPR)对催化剂进行了表征.分析结果表明,Ni、Fe和Co部分进入Ce0.5Zr05O2固溶体晶格内部,导致催化剂体相形成更多的缺陷;同时Ce0.5Zr0.5O2固溶体有助于加速金属氧化物和金属之间氧化还原过程的进行,促进了氧吸附、传输和对甲烷的活化.另外,SiC和Ce0.5Zr0.5O2固熔体良好的抗积碳性能,有效避免了催化剂在富甲烷反应气氛中因积碳而失活,从而使三种催化剂均具有优良的催化燃烧脱氧活性和稳定性.其中,Co/Ce0.5zr0.5O2/SiC活性最高,可在320 ℃活化催化甲烷,并在410 ℃实现完全脱氧.     

Effect of SO2 on Performance of Solid Oxide Fuel Cell Cathodes

Effects of SO₂ in ambient air on the performance and durability of solid oxide fuel cell(SOFC) cathode were evaluated by galvanostatic measurement. Comparison between two cathode materials was made to consider the cathode degradation mechanisms. The degradation performance is associated with a slow decomposition of the La_0.6Sr_0.4Co_0.2Fe_0.8O₃(LSCF) due to the segregation of strontium oxide. Negligible deterioration for (La_0.7Sr_0.3)MnO₃ (LSM) cathode was caused by SO₂ poisoning under a current density of 200 mA/cm². Metal sulphate formation may explain a slight deterioration under increasing high the concentration of SO₂. It was verified that the poisoning mechanism for the two cathode materials resulted from the gradual decomposition of the cathode materials.     

贫燃条件下丙烯选择还原一氧化氮新型锡锆固溶体催化剂性能

采用双股江流共沉淀方法制备了锡锆固溶体DeNO_x催化剂,在反应气组成为1. 212*10~(-3)NO,1.095*10~(-3)C_3H_6和2.09%O_2,反应空速为17000h~(-1)条件下 ,含SnO_2为w(SnO_2)=60%的样品在350 ℃时有最大NO还原转化率71%。固定锡锆比 w(SnO_2)=60%,采用尿素均相沉淀法制备的样品在相同测试条件下,350℃的最大 NO转化率达74%。对该样品在不同温度、不同氧气及丙烯浓度、不同反应空速及水 热处理条件下的NO还原性能进行考察。结果表明,锡锆固溶体催化剂具有较高的热 稳定性和水热稳定性,以及较好的抗氧性能和对高空速的耐受特性。结合对丙烯转 化率的分析,锡锆固溶体上丙烯完全燃烧活性的抑制有利于提高NO的还原活性。     

Ce0.5Zr0.5O2修饰的Ni/SiC、Fe/SiC和Co/SiC催化燃烧甲烷性能

以铈锆固溶体(Ce0.5Zr0.5O2)修饰的高比表面积SiC为载体,采用两步浸渍法制备了Ni、Fe和Co基催化剂,研究了其在煤层气催化燃烧脱氧中的催化活性和稳定性.利用X射线衍射(XRD)、X射线光电子能谱(XPS)、电感耦合等离子体质谱(ICP-MS)、高分辨透射电子显微镜(HRTEM)、比表面积(BET)、热重分析(TGA)和H2程序升温还原(H2-TPR)对催化剂进行了表征.分析结果表明,Ni、Fe和Co部分进入Ce0.5Zr0.5O2固溶体晶格内部,导致催化剂体相形成更多的缺陷;同时Ce0.5Zr0.5O2固溶体有助于加速金属氧化物和金属之间氧化还原过程的进行,促进了氧吸附、传输和对甲烷的活化.另外,SiC和Ce0.5Zr0.5O2固熔体良好的抗积碳性能,有效避免了催化剂在富甲烷反应气氛中因积碳而失活,从而使三种催化剂均具有优良的催化燃烧脱氧活性和稳定性.其中,Co/Ce0.5Zr0.5O2/SiC活性最高,可在320℃活化催化甲烷,并在410℃实现完全脱氧.     

铽改性铈锆固溶体

铽改性铈锆固溶体;Ce0.6Zr0.4-xTbxO2-y固溶体;三效催化剂;储氧材料;共沉淀法;溶胶-凝胶法     

CF4 decomposition over solid ternary mixture NaF-Si-MO（MO=La2O3,CeO2,Pr6O-（11）,Nd2O3,Y2O3）

A solid ternary mixture consisting of NaF,silicon and one metal oxide such as La2O3,CeO2,Pr6O11,Nd2O3,and Y2O3 was prepared and usedas de-fluorinated reagent for CF4 decomposition.The results show that 90% conversion of CF4 can be reached initially over NaF-Si-La2O3,NaF-Si-CeO2,NaF-Si-Nd2O3,and NaF-Si-Y2O3 at 850 C.The fresh and used reagents were characterized using XRD and XPS techniques.It was found that the active components of NaF and metal oxides in NaF-Si-CeO2,NaF-Si-Pr6O11,NaF-Si-Nd2O3,and NaF-Si-Y2O3 weretransformed into inert phases of mixed metal fluorides and silicates,respectively,resulting in an ineffective utilization of these de-fluorinatedreagents,whereas no inert phases from NaF and La2O3 can be observed in the used NaF-Si-La2O3,indicating the NaF-Si-La2O3 reagent couldbe utilized more efficiently than the other reagents in CF4 decomposition.     

Partial P-Type Metal Ions Doping Induced Variation of Both Crystal Structure and Oxygen Vacancy Within Cu/SnO2 Metastable Solid Solution Nanofibers for Highly Sensitive C2H2 Sensor

Partial P-type metal ions doping(PPMID) is an alternative method to further enhance the gas sensing performance of N-type metal oxides(NMOs) in contrast to that of P-N metal oxides heterojunctions, but the influences of the introduction of PPMID on the grain size and oxygen vacancies of NMOs have been rarely investigated. Herein, a simple and effective route has been demonstrated to address this problem with Cu²⁺-doped SnO₂ metastable solid solution nanofibers(CSMSSNs) as model and C₂H₂ as target molecule by combining electrospinning and calcination technique. It seems that the introduction of PPMID can also affect crystal structure and oxygen vacancies of NMOs, proven by combining X-ray diffraction(XRD) and X-ray photoelectron spectra(XPS). Thus, PPD, crystal structure and oxygen vacancies have been combined to clarify the enhanced sensing performance of Cu-doped SnO₂ metastable solid solution nanofibers angainst C₂H₂.     

La0.5>RE0.3Sr0.2FeO3－δ (RE = Nd、Ce、Sm)体系双稀土阴极材料的制备与电性能

采用甘氨酸-硝酸盐法(GNP)合成了La0.5RE0.3Sr0.2FeO3－δ(RE=Nd、Ce、Sm)系列复合氧化物粉体. 用X射线衍射(XRD)和TG-DSC分析了样品钙钛矿物相的形成过程, 用Archimedes排水法测量体积密度并计算烧结样品的相对密度, 用四端子技术测量电导率. 结果显示, 掺Nd的样品1200 ℃烧结2 h成为单一立方钙钛矿结构, 掺Ce样品有明显的CeO2立方相析出, 掺Sm样品主相为钙钛矿结构伴有微弱的杂峰. 1250 ℃烧结2 h的La0.5Nd0.3Sr0.2FeO3－δ在600 ℃时电导率高达100 S•cm-1以上, 明显高于La0.5Ce0.3Sr0.2FeO3－δ及La0.5Sm0.3Sr0.2FeO3－δ样品的电导率, 预示着La0.5Nd0.3Sr0.2FeO3－δ可能是一种良好的中温固体氧化物燃料电池(SOFC)阴极材料.     

Oxygen Storage Materials for Automotive Catalysts: Ceria-Zirconia Solid Solutions

This paper reviews progress in the development of oxygen storage materials for automotive exhaust catalysts. The research was mainly conducted as a study and development exercise in the author's laboratory in Japan.Ceria-lanthana solid solutions (CL) and the first generation of ceriazirconia solid solutions (CZ) were developed as excellent oxygen storage materials for automotive catalysts in the 1980s. These materials consist of ceria doped with less than 20 mol% of La⁴⁺ or Zr⁴⁺. An increase in oxygen defects in CL and CZ under reductive conditions is responsible for an enhanced oxygen storage capability on the cerium atoms. An accurate measure of the oxygen storage capacity (OSC) per cerium is very important for theoretical and practical treatments of the catalyst. The term partial OSC was introduced to describe this capacity and to differentiate it from the usual definition of the OSC, known also as the total OSC. After the development of CL and CZ, a new technology was developed to dissolve more than 20 mol% of zirconia in the ceria, allowing second generation CZ and third generation CZ (known as ACZ, which is doped with alumina) to be successfully developed in the 1990s. The partial OSC of these materials increases with increasing amounts of zirconia dissolved in the ceria, and also with decreasing material particle size after an engine durability test. In the case of ACZ, alumina was added to CZ based on the diffusion barrier concept, in which a diffusion barrier layer inhibits the coagulation of CZ and A when the material is required for duty at high temperature in air.Furthermore, the relationship between the total or partial OSC and the structure of the ceriazirconia solid solutions is explained in this paper.For ceriazirconia solid solutions composed of equimolar CeO₂ and ZrO₂(Ce/Zr=1), the total or partial OSC of the -phase CeZrO₄, in which the cerium and zirconium ions are regularly distributed, was about twice as large as that of a ceriazirconia solid solution with a relatively irregular distribution of cerium and zirconium ions, and about five times larger than that of a mixture of ceria powder and zirconia containing only a small amount of ceriazirconia solid solution. It corresponds to about 89% of the theoretical maximum value.For a ceriazirconia solid solution composed of non-equimolar CeO₂ and ZrO₂(Ce/Zr 1), the partial OSC of a ceria--phase solid solution with a zirconia content of between 30 and 50mol% is much higher than that of a ceriazirconia solid solution of the same zirconia content. The partial OSC of a -phase and zirconia mixed oxide, which is formed by reducing the material at 1200 °C, reaches a value above 0.20 mol-O₂/mol-Ce (about 80% of the theoretical maximum value of the partial OSC), when the zirconia content is between 50 and 80 mol%.The Toyota Motor Corp. has put automotive three-way catalysts containing the first, second and third generations of CZ into practical use on a global basis.     

共模板法一步合成绣球状BiOCl/Br固溶体光催化剂

以乙二醇/十二烷基三甲基溴化铵(EG/DTAB)为共模板剂,一步制得BiOCl/Br的固溶体光催化剂,利用X射线衍射仪、扫描电子显微镜、能谱仪、N2吸附-脱附仪和紫外-可见漫反射光谱仪进行了表征.结果表明,与采用溶剂热法制得的BiOCl分级微球相比,采用EG/DTAB共模板法制得的BiOCl/Br固溶体具有更明显的分层结构,呈绣球状.同时,DTAB的Br-插入到BiOCl的晶格中,形成固溶体,减小了禁带宽度.绣球状BiOCl/Br固溶体具有比商用P25、二维BiOCl纳米片和三维BiOCl分级微球更优异的可见光间接敏化降解染料性能,当nDTAB/nKCl=0.75时,制得的BiOCl/Br固溶体8 min内在可见光下对罗丹明B(Rh B)的降解率达到97.2%;1 h后在可见光下对甲基橙(MO)的降解率达到83.6%.     

白钨矿结构物相含稀土异价固溶体的形成规律

运用原子参数-支持向量机算法(SupportVectorMachine,SVM)和熔盐相图智能数据库技术,研究了白钨矿型钼酸盐、钨酸盐和含稀土钼酸盐、钨酸盐形成异价固溶体的条件,建立了碱金属-稀土钼酸盐和钨酸盐的晶型以及这些化合物与稀土钼酸盐或钨酸盐形成连续固溶体的判据,并求得这类化合物的晶胞参数的计算式。计算表明:各组分元素的离子半径和电负性是影响固溶体形成、晶型和晶胞参数的主要因素。根据本文所得经验式估计TlPr(MoO4)2-Pr2(MoO4)3系固溶体情况与实测结果一致。     

Photocatalytic Activities for Water Splitting of RuO_2-loaded MGa_2O_4（M=Zn,Ni） with d~（10） Configuration

MGa2O4(M=Zn,Ni) rods with similar crystallinity and BET surface area were prepared via a facile template-engaged reaction.The photocatalytic activities for water splitting of RuO2-loaded MGa2O4(M=Zn,Ni) were investigated under high-pressure Hg lamp.RuO2-loaded ZnGa2O4 catalyst exhibited much higher photocatalytic activity than RuO2-loaded NiGa2O4.Factors affecting the photocatalytic activities of RuO2-loaded MGa2O4(M=Zn,Ni) were discussed.It was suggested that the electronic structure of oxide semiconductor was a predominant factor of the photocatalytic behavior for RuO2-loaded MGa2O4(M=Zn,Ni).     

CeO2-MOx (M=La3+, Ca2+)改性Pd/γ-Al2O3催化甲烷燃烧性能

采用沉积-沉淀法制备了固溶体CeO2-MOx(M=La3+, Ca2+)改性的Pd/γ-Al2O3催化剂, 利用XRD、Raman和XPS对催化剂进行了表征. 结果表明, 金属(M)离子进入CeO2的晶格, 形成CeO2-MOx固溶体, Raman谱上463 cm-1处对应于Ce—O键的F2g对称伸缩振动强度降低. 其中, 样品Pd/γ-Al2O3-CeO2-CaO在615 cm-1处出现一小峰, 样品Pd/γ-Al2O3-CeO2-La2O3在320 cm-1处出现的肩峰, 都表明固溶体CeO2-MOx的形成使O2-亚晶格结构对称性降低. XPS分析表明, 固溶体改性的Pd/γ-Al2O3催化剂中Pd 的3d5/2结合能比正常价态的PdO的结合能高出0.5-0.6 eV, 形成了一种高度离子化的, 与载体具有强相互作用的Pd物种. 催化甲烷燃烧实验证明, 固溶体CeO2-MOx(M=La3+, Ca2+)改性的Pd/γ-Al2O3催化剂的低温活性和稳定性均高于未经改性的Pd/γ-Al2O3催化剂和仅用CeO2改性的Pd/γ-Al2O3催化剂, 在空速为50000 h-1时, 可使1%CH4-99%空气(体积分数)混合气中甲烷的10%转化温度降至254 ℃, 转化率100%时的转化温度降至340 ℃.     

CuO/CeO2-MOx(M=C0,Mn,Al和La)催化剂富氢条件下CO氧化性能的研究

研究了MOx(M=Co,Mn,Al和La)对CuO/CeO2催化剂富氢条件下CO选择性氧化性能的影响,并运用XRD,XPS,BET,TPR和TPD等手段对催化剂进行了表征.结果表明,MnOx和Co3O4的引入能提高CuO/CeO2催化剂富氢条件下CO选择性氧化的活性,其中以MnOx的改性效果最好,80 ℃时CO转化率达58%,140℃为100%.与其他CuO/CeO2-MOx催化剂相比,CuO/CeO2-MnOx催化剂中活性组分与载体的相互作用较强,铜原子外电子云密度升高,表面Cu和晶格氧含量较多,CO的吸附量较大.     

磁固相萃取结合高效液相色谱检测农田灌溉水中4种苯甲酰脲类农药

采用溶剂热法制备了磁性金属有机骨架吸附剂Fe_3O_4-NH_2@MIL-101,通过电子显微镜、红外光谱、X射线衍射对吸附剂的形貌和组成进行了表征,磁强计对吸附剂的磁强度进行了测定。使用该吸附剂进行磁固相萃取,结合高效液相色谱-紫外检测,对农田灌溉水中4种苯甲酰脲类杀虫剂(氯吡脲、氟幼脲、氟铃脲和虱螨脲)进行分析。实验对吸附和洗脱条件进行了优化,包括吸附剂用量、吸附时间、pH值、离子强度、洗脱溶剂种类以及洗脱时间和体积。在最佳实验条件下,方法能够有效富集灌溉水中的苯甲酰脲类杀虫剂。4种苯甲酰脲类杀虫剂在0. 010～3. 0 mg/L浓度范围内线性关系良好,相关系数(r)均大于0. 999 5,检出限为0. 03～0. 09μg/L,定量下限为0. 10～0. 30μg/L。方法的加标回收率为81. 7%～95. 4%,RSD小于10%。该方法前处理操作简便,萃取用时不超过15 min,可用于农田灌溉水中苯甲酰脲类杀虫剂的检测。     

商用SCR脱硝催化剂K2O中毒后再生:(NH4)2SO4溶液

利用(NH₄)₂SO₄溶液对K₂O中毒后烟气SCR (selective catalytic reduction)脱硝商用催化剂活性进行再生。采用湿法浸渍法使催化剂表面负载不同质量K₂O,前驱体为KNO₃溶液。经过再生工艺处理后,在不同模拟烟气空速及氧浓度条件下均具有良好的活性。进一步利用离子色谱(IC)、N₂吸附脱附分析(BET)、扫描电镜及其元素能谱分析(SEM-Maps, EDX)、红外光谱分析(FT-IR)等技术对再生前后催化剂进行表征。结果表明,再生工艺对K₂O去除效果明显,有效地恢复了催化剂表面活性位V=O。此外,再生过程没有导致催化剂表面物质的流失及机械强度的降低。