金催化剂在环氧丙烷尾气回收中的应用研究

采用沉积-沉淀法制备了Au负载催化剂。通过对CO在催化剂上的低温催化氧化反应的研究,考察了载体选择,Au的质量分数,金属助剂修饰和反应温度等对反应的影响。结果表明,载体的选择和Au的含量对催化活性都有较大影响,γ-Al2O3是除氧实验中性能优良的催化剂载体材料。使用金属氧化物修饰载体可起到提高催化剂活性,增强催化剂稳定性的作用。     

甲烷在Cr改性Pd/Al2O3催化剂上的催化燃烧性能

研究了Cr改性Pd/Al2O3催化剂上低浓度甲烷的催化燃烧反应,考察了载体Cr Al的制备方法和活性组分Pd的负载方法对催化剂催化活性的影响以及添加Ce对催化剂高温稳定性的影响。采用X射线衍射、程序升温还原等表征手段分析了催化剂结构和氧化还原性。结果表明,与采用沉淀法制备的载体P-Cr Al相比,采用浸渍法制备的载体I-Cr Al具有较高的比表面积和反应活性;用Na BH3对Pd负载过程进行还原处理能明显提高催化剂活性,其原因是还原过程加强了催化剂上Pd与载体Cr Al之间的作用,通过H2-TPR证明了其还原能力得到了增加;添加Ce缓解了Al2O3高温条件下的烧结,增强了催化剂的高温稳定性。     

液相原位还原法制备钯基催化剂

采用液相原位还原法制备Pd/α-Al2O3催化剂,并应用于CO氧化偶联合成草酸二甲酯反应。对比实验发现,甲醛液相原位还原法制得的Pd基催化剂具有优异的催化活性,当Pd负载质量分数低至0.1%时,催化剂仍表现出较高的活性和稳定性。采用XRD和BET等对催化剂及载体进行表征,结果表明,催化剂活性与载体的比表面积、孔容和孔径没有必然联系。通过TEM发现,0.1%-Pd/α-Al2O3催化剂中的主要活性组分Pd具有较小的颗粒和较高的分散性,通过HRTEM发现,液相原位还原法制备的催化剂能够有效暴露出Pd(111)晶面。     

载体γ-Al_2O_3的改性对担载型催化剂La_(0.8)K_(0.2)-Mn_(0.95)Cu_(0.05)O_3/γ-Al_2O_3碳烟催化燃烧性能的影响

采用混合法制备La0.8K0.2Mn0.95Cu0.05O3/γ-Al2O3担载型钙钛矿型催化剂,担载前载体于0.5 mol/L的H2SO4溶液中进行浸渍改性。运用程序升温氧化对各担载型催化剂进行活性评价,考察载体改性时间对催化剂活性的影响。采用XRD和FTIR对催化剂进行了表征,结果显示,改性后的担载型催化剂能够保持良好的钙钛矿结构;与6 h和24 h的相比较,发现载体γ-Al2O3经过12 h浸渍改性后,混合法制备的担载量为20%的担载型催化剂表现出较好的催化活性,将碳烟的起燃温度降至389℃,该温度在柴油车排气温度范围内。     

催化剂MnyCezOx/Al2O3催化氧化乙酸乙酯的性能

采用浸渍法制备了Mn基负载型催化剂,测定了它们催化氧化乙酸乙酯的活性以及水蒸气对其催化性能的影响,研究结果表明所制备的催化剂对乙酸乙酯都具有明显的催化活性,其中催化剂Mn0.8Ce0.2Ox/Al2O3催化氧化乙酸乙酯的活性最高,其T90仅为225℃。催化剂Mn0.8Ce0.2Ox/Al2O3的抗水蒸气影响的能力也要高于催化剂MnOx/Al2O3。     

Au/La_2O_3+Co_3O_4催化剂制备及其对CO催化氧化性能和稳定性的研究

为了能够得到高催化活性、高热稳定性的Au催化剂,本文选择了混合氧化物La_2O_3+Co_3O_4为载体,制备了两种Au/La_2O_3+Co_3O_4催化剂,并考察了此催化剂对CO氧化反应的催化活性及稳定性。实验结果表明:Au/La_2O_3+Co_3O_4催化剂活性好于250℃焙烧的Au/La_2O_3+Co_3O_4(C)催化剂,Au/La_2O_3+Co_3O_4(C)催化剂稳定性好于Au/La_2O_3+Co_3O_4催化剂。     

甘油氢解制1,2-丙二醇Cu/ZrO_2催化剂的稀土改性

用等体积浸渍法制备了稀土改性的Zr O2负载铜催化剂,考察其在质量分数40%甘油水溶液进料时气相氢解制1,2-丙二醇反应的性能,并用比表面积及孔径分析仪(BET)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)和氢气程序升温还原(H2-TPR)表征了催化剂的孔结构、形貌、晶相和还原性。典型的氢解反应条件为220℃、1MPa、氢与甘油的摩尔比值为100,液时空速为0.25 g甘油/(g催化剂·h)。首先在预实验中对Al2O3、Si O2和Zr O23种载体进行对比实验,发现未改性的负载铜催化剂均不稳定。浸渍Ce改性的Cu/Si O2催化剂稳定性有较大改善,但只维持700 h左右。接着考察用共沉淀法在Zr O2载体中添加稀土元素铈(Ce)、镧(La)和钇(Y)的改性效果,发现均能显著提高催化活性和选择性,而加Y稳定的氧化锆(YSZ)载体性能最佳。最后浸渍Ce对Cu/YSZ催化剂进行改性,并对Ce的含量进行了优化,结果证明,18%Cu~4%Ce O2/YSZ(均为质量分数)催化剂活性和选择性最佳,1,2-丙二醇得率超过93%。该催化剂具有开放性孔结构,比表面积达到107 m2/g,前躯体中Cu O晶粒最小,还原温度最低。对最优条件下制备的催化剂进行了长运转考察,稳定运行超过1 600 h,1,2-丙二醇收率维持在94%以上。     

Ce0.8Cu0.2O2-δ氧化物直接涂载的整体式催化剂的化性能研究

以Ce0.8Cu0.2O2-δ氧化物为前驱体,通过浸渍法制备了Ce0.8Cu0.2O2-δ氧化物整体式催化剂.超声波振荡结果表明,Ce0.8Cu0.2O2-δ氧化物涂层具有良好的抗振荡性.以乙酸乙酯完全燃烧为模型反应,发现Ce0.8Cu0.2O2-δ氧化物直接涂载的整体式催化剂具有良好的催化活性.BET和H2-TPR结果表明,催化剂的活性与涂层的有效成分Ce0.8Cu0.2O2-δ固溶体的量有密切的关系.当Ce0.8Cu0.2O2-δ固溶体的质量分数为3%时,涂层的抗振荡性能和粘结强度较好,催化剂的活性也相对较高.     

Ce0．8Cu0．2O2—δ氧化物直接涂载的整体式催化剂的催化性能研究

以Ce0.8Cu0.2O2-δ氧化物为前驱体,通过浸渍法,制备了Ce0.8Cu0.2O2-δ氧化物整体式催化剂.超声波振荡结果表明,Ce0.8Cu0.2O2-δ氧化物涂层具有良好的抗振荡性.以乙酸乙酯完全燃烧为模型反应,发现Ce0.8Cu0.2O2-δ氧化物直接涂载的整体式催化剂具有良好的催化活性.BET和H2-TPR结果表明,催化剂的活性同涂层的有效成分Ce0.8Cu0.2O2-δ固溶体的量有密切的关系.当Ce0.8Cu0.2O2-δ固溶体的量为3叭%时,涂层的抗振荡性能和粘结强度比较好,催化剂的活性也相对较高.     

Ce0.8Cu0.2O2-δ氧化物直接涂载的整体式催化剂的催化性能研究

Ce0.8Cu0.2O2-δ氧化物为前驱体,通过浸渍法制备了Ce0.8Cu0.2O2-δ氧化物整体式催化剂。超声波振荡结果表明,Ce0.8Cu0.2O2-δ氧化物涂层具有良好的抗振荡性。以乙酸乙酯完全燃烧为模型反应,发现Ce0.8Cu0.2O2-δ氧化物直接涂载的整体式催化剂具有良好的催化活性。BET和H2-TPR结果表明,催化剂的活性与涂层的有效成分Ce0.8Cu0.2O2-δ固溶体的量有密切的关系。当Ce0.8Cu0.2O2-δ固溶体的质量分数为3％时,涂层的抗振荡性能和粘结强度较好,催化剂的活性也相对较高。     

尖晶石型Mn_(1-x)M_xCo_2O_4柴油车尾气处理催化剂的制备及其应用

尖晶石型复合氧化物因具有独特的结构特征而成为相对理想的柴油车尾气处理催化剂。采用溶胶-凝胶法制备尖晶石型Mn_(1-x)M_xCo_2O_4催化剂,通过X射线衍射(XRD)和程序升温氧化(TDO)等对Mn_(1-x)M_xCo_2O_4催化剂进行表征。结果表明,制备的样品Mn_(1-x)M_xCo_2O_4均为尖晶石型复合氧化物;掺杂Cu、Ce后,催化剂的氧化性能有不同程度的变化。在固定床微型反应器上对催化剂催化活性进行评价,结果表明,与纯MnCo_2O_4相比,Mn_(0.9)Ce_(0.1)Co_2O_4催化剂催化活性提高,Mn_(0.9)Cu_(0.1)Co_2O_4催化剂催化活性降低,但CO_2选择性增加。     

Catalytic performance of perovskite-like oxide doped cerium(La_(2-x)Ce_xCoO_(4±y)) as catalysts for dry reforming of methane

A series of oxides(La_(2-x)Ce_xCoO_(4±y)) with perovskite-like structure were prepared by the Pechini sol–gel method for dry reforming of methane reaction(DRM). The prepared catalysts were characterized by BET, XRD,TGA, H_2-TPR and SEM. Experimental results indicate that the addition of Ce can impact both sample morphology and catalytic performance significantly compared with La_2CoO_4 catalyst, and LaCeCoO_4 presented the highest catalytic ability among all the samples. The Ce addition tends to increase the specific surface area of La_(2-x)Ce_xCoO_(4±y)from 0.2 to 8.5 m~2·g~(-1), suggesting that LaCeCoO_4 catalyst contained more well-dispersed active sites and more space to reaction. Moreover, the catalytic performance and anti-coking ability were substantially improved after Ce addition during DRM, which may be attributed to the decrease of LaCoO_3 particle size and growth of oxygen storage capacity, respectively.     

火焰喷雾合成法制备La0.8Sr0.2Mn1-xCuxO3催化氧化CO性能研究

采用火焰喷雾合成法制备了Sr²⁺、Cu²⁺分别取代A、B位的La_0.8Sr_0.2Mn_1-xCu_xO₃ （x=0,0.1,0.2,0.3,0.4）钙钛矿催化剂,并用于CO催化氧化实验,研究了水蒸气和CO₂对催化剂CO氧化活性的影响。对不同取代量La_0.8Sr_0.2Mn_1-xCu_xO₃ 催化剂进行了XRD、SEM、EDS、BET、XPS、H₂-TPR和O₂-TPD等表征测试。结果表明,火焰喷雾合成法制备的钙钛矿催化剂具有良好的钙钛矿相、疏松多孔结构和催化氧化活性。其中,La_0.8Sr_0.2Mn_0.9Cu_0.1O₃分别在119.4℃和133.3℃实现50%和90%的CO转化率。掺杂水蒸气和CO₂会与CO在催化剂表面形成竞争吸附,导致5种催化剂性能衰减,但La_0.8Sr_0.2Mn_0.9Cu_0.1O₃仍能在150.2℃实现90%的CO催化转化,在连续稳定性催化氧化测试中,5种催化剂性能衰减不超过10%。结合上述CO催化氧化实验,火焰喷雾合成法制备的催化剂具有良好的稳定性和催化活性,适合制备高CO催化氧化活性的钙钛矿催化剂。     

锰铈固溶体复合氧化物用于CO和CH_4催化氧化

采用氧化还原共沉淀法制备系列不同配比的锰铈复合氧化物,用于CO和CH4催化氧化,考察不同焙烧温度对催化剂性能的影响。研究表明,焙烧温度500℃和Mn与Ce物质的量比为5∶5的催化剂具备最优的CO和CH4催化氧化性能。催化剂在90℃时,CO转化率可达100%;对于CH4催化氧化,反应温度500℃时,CH4转化率为80%。通过N2吸附-脱附、H2-TPR和XRD等研究其物化结构性能,结果表明,在系列催化剂中,焙烧温度500℃和Mn与Ce物质的量比为5∶5的催化剂具有最高的比表面积和最活泼的晶格氧,可能是其具有优异催化活性的原因。     

An investigation of NO/CO reaction over perovskite-type oxide La0.8Ce0.2B0.4Mn0.6O3 (B = Cu or Ag) catalysts synthesized by reverse microemulsion

The perovskite-type oxides La_0.8Ce_0.2Cu_0.4Mn_0.6O₃ and La_0.8Ce_0.2Ag_0.4Mn_0.6O₃ prepared by reverse microemulsion and sol–gel methods (denoted as R and S, respectively), have been investigated on their catalytic performance for the (NO + CO) reaction, and characterized by means of temperature-programmed desorption (TPD), X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). XRD measurements proved the presence of the perovskite phase with a considerable amount of CeO₂ phase and the formation of CeO₂ phase was restrained with the reverse microemulsion method. TEM investigations revealed that the La_0.8Ce_0.2Cu_0.4Mn_0.6O₃-R nanoparticles were uniform spheres in shape with diameters ranging from 40 to 50 nm, whereas an aggregation of particles was found for the La_0.8Ce_0.2Cu_0.4Mn_0.6O₃-S catalyst. The activity of NO reduction with CO decreased in the order of La_0.8Ce_0.2Cu_0.4Mn_0.6O₃-R > La_0.8Ce_0.2Cu_0.4Mn_0.6O₃-S > La_0.8Ce_0.2Ag_0.4Mn_0.6O₃-R > La_0.8Ce_0.2Ag_0.4Mn_0.6O₃-S. In NO-TPD experiments, the principal desorbed species detected in the effluent was NO with a trace amount of O₂ and N₂O, suggesting that the non-dissociated adsorption of NO on the surface of the perovskite-type oxides was dominant. The XPS results revealed that Ce⁴⁺ and Cu⁺ was the predominant oxidation state for Ce and Cu components in La_0.8Ce_0.2Cu_0.4Mn_0.6O₃ and La_0.8Ce_0.2Ag_0.4Mn_0.6O₃ catalysts. The existence of Cu⁺ ions and its redox reaction (Cu⁺ ↔ Cu²⁺) would benefit the NO adsorption and reduction by CO.     

Effect of Ru on LaCoO3 perovskite-derived catalyst properties tested in oxidative reforming of diesel

The oxidative reforming of diesel over Co/La₂O₃ and Ru–Co/La₂O₃ catalysts derived from LaCoO₃ perovskite precursors was studied. Physicochemical characterization by XPS, TPR and XRD revealed that the incorporation of Ru to LaCoO₃ produces changes in LaCoO₃ evidenced by a smaller size of the LaCoO₃ particles and cobalt segregation on the LaCoO₃ surface. The modifications in the structure of LaCoO₃ induced by the addition of Ru directly affect the dispersion and morphology of Co particles developed under the reaction. The active phases derived from pretreatment of perovskites evolve differently with time on stream, being observed that the presence of a greater proportion of perovskite phase in the Ru/LaCoO₃ sample produces an increase in catalyst stability. TPD-MS analysis also indicates that bulk oxygen release from the Ru–Co/La₂O₃ sample could improve its catalytic behaviour. The characterization of used samples reveals that improvements in the cobalt surface concentration and Co–La₂O₃ interactions contribute to the better catalytic stability of the Ru–Co/La₂O₃-derived catalyst.     

邻二氯苯在钒-钨-钛催化剂上的完全催化氧化

采用等体积浸渍法制备不同系列钒-钨-钛催化剂,以与二噁英TCDD化学结构式相似的邻二氯苯作为替代物,研究催化剂对邻二氯苯的去除效率,考察钒负载质量分数和钨负载质量分数对邻二氯苯催化氧化性能的影响,通过XRD和催化剂比表面积分析对催化剂的微观结构进行表征。结果表明,随着钒负载质量分数的增加,催化剂比表面积降低,催化剂性能降低;随着钨负载质量分数的增加,催化剂比表面积增加,催化剂性能提高。钨的加入有利于促进活性钒的分散,提高催化剂的比表面积,催化剂比表面积是影响催化剂性能的关键因素。     

Kinetics of the water–gas shift reaction over nanostructured copper–ceria catalysts

Water–gas shift reaction was studied over two nanostructured Cu_xCe_1−xO_2−y catalysts: a Cu_0.1Ce_0.9O_2−y catalyst prepared by a sol–gel method and a Cu_0.2Ce_0.8O_2−y catalyst prepared by co-precipitation method. A commercial low temperature water–gas shift CuO–ZnO–Al₂O₃ catalyst was used as reference. The kinetics was studied in a plug flow micro reactor at an atmospheric pressure in the temperature interval between 298 and 673 K at two different space velocities: 5.000 and 30.000 h⁻¹, respectively. Experimentally estimated activation energy, E_af, of the forward water–gas shift reaction at CO/H₂O = 1/3 was 51 kJ/mol over the Cu_0.1Ce_0.9O_2−y, 34 kJ/mol over the Cu_0.2Ce_0.8O_2−y and 47 kJ/mol over the CuO–ZnO–Al₂O₃ catalyst. A simple rate expression approximating the water–gas shift process as a single reversible surface reaction was used to fit the experimental data in order to evaluate the rate constants of the forward and backward reactions and of the activation energy for the backward reaction.     

Supported Co-based perovskites as catalysts for total oxidation of methane

Supported LaCoO₃ perovskites with 2, 5, 10, 15, 20 and 30 wt.% loading were prepared by impregnation of a Ce_0.8Zr_0.2O₂ support (40 m² g⁻¹) with: (i) a solution of La and Co nitrates and (ii) a “citrate” solution, namely containing La and Co nitrates, and citric acid. All precursors were decomposed and calcined at 700 °C for 5 h. XRD investigations indicated the formation of a pure perovskite phase only if citrates were used. These materials were tested as catalysts for methane combustion in the temperature range 300–700 °C. All catalysts showed a lower T₅₀ (the temperature at which the conversion level of methane is 50%) than the Ce_0.8Zr_0.2O₂ support or non-supported LaCoO₃. The activity increased continuously with the perovskite loading. The samples prepared from citrates were slightly more active than from nitrates. This is due to a more homogeneous surface, as indicated by XPS measurements. The presence of a well-characterized perovskite phase (as opposed to highly dispersed elements) seems necessary for good activity. A higher reaction rate per perovskite weight is observed for low loadings when compared to bulk LaCoO₃, but the variation with perovskite loading presents a breakpoint, suggesting complex interactions in the catalysts or in the oxidation mechanism.

In spite of the experimental impossibility to evaluate the area developed by the supported perovskite, an approximative approach strongly suggests a synergy between the support and supported species.     

四效催化剂La-K-Co-Mn同时去除CO、C_xH_y、PM和NOx的研究

四效催化剂的活性组分La0.8K0.2Co0.7Mn0.3O3的合成温度对柴油烟气的净化效果有较大影响,通过X射线衍射、电子扫描电镜、程序升温、比表面积检测和在线效率检测发现,750℃合成的四效催化剂净化柴油烟气的效果最好。通过K和Mn同时部分取代La Co O3中La和Co,探讨K和Mn对钙钛矿结构和烟气净化效果的影响。比表面积检测发现,涂覆改性γ-Al2O3后,整体式催化剂比表面积增加,催化性能得到有效改善。