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。     

Fe掺杂对La_(0.9)Sr_(0.1)Co_(1-x)FexO_3催化剂同时净化NO和碳烟活性规律研究

采用柠檬酸-EDTA络合法制备了纳米钙钛矿催化剂La_(0.9)Sr_(0.1)Co_(1-x)FexO_3,催化剂具有较好的同时去除NO和碳烟(soot)催化活性,其中La_(0.9)Sr_(0.1)Co_(0.7)Fe_(0.3)O_3展现出最佳的催化活性,其在380.0℃时NO转化率为32.5%,soot最大燃烧速率温度(T_m)为368.5℃。H_2-程序升温还原(H_2-TPR)和NO-程序升温脱附(NO-TPD)结果表明,Fe掺杂能显著提高催化剂低温还原性能、表面氧物种活性及NO吸附性能,这有利于其改善催化活性。X射线光电子能谱(XPS)结果表明,Fe掺杂能增加催化剂表面吸附氧浓度和高价离子(Co~(4+)),这对提高催化氧化能力至关重要。采用颗粒物捕集器(DPF)作为载体涂覆CeO_2涂层用于负载La_(0.9)Sr_(0.1)Co_(0.7)Fe_(0.3)O_3催化剂进行柴油机台架实验,结果表明该催化剂具有较好的同时去除NO_x和soot催化活性,最大NO转化率为23.0%,T_m为341.0℃,表明Fe掺杂对提高催化活性至关重要。     

Sr掺杂强化LaCo0.5Cu0.5O3型钙钛矿活化过一硫酸盐的性能

采用溶胶-凝胶法制备A位掺Sr的La_xSr_1-xCo_0.5Cu_0.5O₃钙钛矿增强传统B位掺杂钙钛矿活化过一硫酸盐（PMS）的能力。本文选取效果最好的La_0.7Sr_0.3Co_0.5Cu_0.5O₃型钙钛矿为研究对象,以偶氮染料AO7为目标污染物,考察了钙钛矿投加量、PMS浓度、pH和染料废水中常见Cl^-对La_0.7Sr_0.3Co_0.5Cu_0.5O₃/PMS体系降解AO7的影响,并测试了材料的重复利用性和矿化能力。结果表明,La_0.7Sr_0.3Co_0.5Cu_0.5O₃/PMS降解AO7的速度随着材料投加量和PMS浓度的增加而加快,在中性条件下反应速度最快且矿化率良好。该体系主要活性物种之一为·OH,但Sr掺杂后钙钛矿的O空位增多使得¹O₂也参与到降解过程之中。     

氨分解制氢棒状La x Ce1-x O y 负载Ru催化剂

氨分解得到的H₂不含CO _x 、SO _x 、NO _x 等有害物质,是其他所有含碳资源为原料制氢所不能比拟的。本文采用无模板水热法制备了一系列棒状载体,并采用沉积沉淀法制备了Ru/La _x Ce_1-x O _y 催化剂,考察了制备方法、催化剂组成对性能的影响,并通过扫描电镜（SEM）、X射线衍射（XRD）、BET、H₂-程序升温还原（TPR）和CO₂-程序升温脱附（TPD）进行了表征。结果表明,La₂O₃掺杂量为40%的Ru/La_0.4Ce_0.6O_1.8催化剂在常压、7800h^-1、450℃下氨分解转化率为98%。该催化剂活性高归因于部分还原的CeO_2-x 对Ru的供电子性能和Ru/La_0.4Ce_0.6O_1.8催化剂表面的强碱性增加了对Ru活性位的给电子能力。同时考察了K₂O含量的影响,最优的催化剂为Ru-2%K/La_0.4Ce_0.6O_1.8,在400℃、7800h^-1氨气转化率可以达到93%。结果表明Ru-2%K/La_0.4Ce_0.6O_1.8可以作为一种新型高效氨分解催化剂,为工业化应用提供了可能,具有良好的发展前景。     

镧基钙钛矿材料的制备与催化碳烟性能研究

以La、K、Co, Ni的硝酸盐为主要原材料，采用柠檬酸溶胶凝胶法制备钙钛矿La_1-xK_xCo_0.1Ni_0.9O₃(x=0.1,0.3,0.5,0.7,0.9)催化剂。利用扫描电子显微镜，X射线衍射仪等对钙钛矿催化剂的形貌，物相进行表征。并用使用同步热分析仪研究钙钛矿催化剂对Soot(碳烟颗粒)催化性能。结果表明：La_0.7K_0.3Co_0.1Ni_0.9O₃钙钛矿纯度高，成相好，并且呈多孔结构，颗粒分布均匀，K⁺取代La³⁺,低价态的K⁺的原子半径大于高价态La³⁺的原子半径，会产生新的氧空位，同时吸附活化了晶格中的O₂,提高氧化还原性能，改善催化活性，有效提高了对Soot的催化效果。     

LaMn1-x-yFexCoyO3-δ钙钛矿载氧体用于化学链部分氧化

采用溶胶-凝胶法制备了B位Fe和Co共取代的LaMn_1-x-yFe_xCo_yO_3-δ钙钛矿型复合氧化物,并用于化学链甲烷部分氧化制合成气。X射线衍射（XRD）结果表明Fe和Co均进入了LaMnO₃的晶格形成钙钛矿晶相,活性和稳定性测试表明LaMn_1/3Fe_1/3Co_1/3O_3-δ载氧体具有最佳的化学链甲烷部分氧化性能。CH₄程序升温还原（CH₄-TPR）表征发现LaMn_1/3Fe_1/3Co_1/3O_3-δ具有比LaBO₃（B=Co, Mn, Fe）更高的甲烷活化能力和晶格氧迁移性能。甲烷恒温脉冲反应（CH₄-pulse reaction）进一步证实了B位离子的协同作用可以提高LaBO₃（B=Co, Mn, Fe）的表面反应速率。程序升温氢气还原（H₂-TPR）表明,LaMn_1/3Fe_1/3Co_1/3O_3-δ中晶格氧具有适中的氧化还原能力,适合用于化学链甲烷部分氧化。     

Mn掺杂对尖晶石型NiFe1.97Pd0.03O4-δ催化剂脱硝性能的影响

采用生物模板法,通过掺杂Mn对尖晶石型NiFe_1.97Pd_0.03O_4-δ催化剂中的Fe离子进行取代,制备一系列不同Mn掺杂量的NiFe_1.97-xMn_xPd_0.03O_4-δ催化剂（x=0、0.01、0.02、0.05、0.10）,并在单管固定床反应器中进行H₂-SCR脱硝性能评价。运用X射线衍射仪（XRD）、场发射扫描电子显微镜（FE-SEM）、程序升温-脱附（NH₃-TPD）和程序升温还原（H₂-TPR）以及傅里叶红外光谱仪（FTIR）等手段对催化剂进行表征、分析。结果表明：适量Mn的掺杂不仅可以提高活性物种Pd在催化剂上的分散度,还显著提高了其催化剂表面的总酸量及其氧化还原能力,从而提高了NiFe_1.97Pd_0.03O_4-δ催化剂在低温下的H₂-SCR脱硝活性,并拓宽了其催化活性温度窗口。在实验范围内,NiFe_1.92Mn_0.05Pd_0.03O_4-δ催化剂在150℃下的NO转化率高达95%,且在150~200℃温度区间内,NO转化率均在90%以上。     

可逆固体氧化物电池La0.2Sr0.8TiO3–δ基纤维燃料极的浸渍改性

开发适合可逆操作的高性能燃料极材料对可逆固体氧化物电池的发展至关重要。为解决La_xSr_1–xTiO₃燃料极材料催化活性差及离子电导率低等问题,采用静电纺丝技术直接制备富含连通孔洞的La_0.2Sr_0.8TiO_3–δ (LST)/氧化钇稳定型氧化锆(YSZ)复合纤维,构建了以LST骨架为电子通道主路、YSZ颗粒为离子通道穿插的三维网络混合导体通路,并通过浸渍Ce_0.9M_0.1O_2–δ (M=Fe、Co、Ni)纳米颗粒对燃料极骨架修饰改性,增强燃料极与电解质层间的界面结合,研究不同浸渍物对纤维基燃料极催化活性的影响。结果表明：浸渍Ce_0.9Ni_0.1O_2–δ的燃料极兼具有较强的氢氧化能力和氢还原能力,在浸渍物和Ni纳米颗粒析出的共同作用下,单电池在850℃、3%(体积分数) H₂O/H₂下...     

Cu、Fe掺杂六铝酸盐催化剂的催化还原脱硝性能

采用共沉淀法制备Cu和Fe掺杂的六铝酸盐催化剂（SrCu_xFe_1-xAl₁₁O_19-δ,x=0、0.2、0.4、0.5、0.6、0.8、1）,通过XRD、H₂-TPR和BET等方法对催化剂结构及性能进行研究,并考察以CO为还原剂的催化脱硝活性。结果表明,用碳酸铵作为沉淀剂在1 200 ℃焙烧4 h可形成完整的六铝酸盐晶型,Cu和Fe能取代Al³⁺,较好地促进六铝酸盐晶体结构的形成;SrCu_xFe_1-xAl₁₁O_19-δ催化剂脱硝催化活性较好,在温度不超过450 ℃和空速6 000 h-1条件下,均使NO转化率超过99%。在SrCu_xFe_1-xAl₁₁O_19-δ六铝酸盐催化剂中,Cu和Fe均为催化脱硝的主要活性元素,两种元素按一定量配比更有利于提升脱硝效果,最优催化剂为SrCu_0.5Fe_0.5Al₁₁O_19-δ。     

钙钛矿阳极固体氧化物燃料电池在CO–CO2燃料下的性能和稳定性

以原位析出纳米Co–Fe颗粒的La_0.4Sr_0.6Co_0.2Fe_0.7Nb_0.1O_3–δ(LSCFN)钙钛矿为阳极,考察了直接使用CO–CO₂燃料时的阳极结构演变、单电池电化学性能和稳定性。结果表明:在CO燃料中,ABO₃钙钛矿结构LSCFN转变为A₂BO₄层状钙钛矿结构;在CO中引入少量CO₂后,LSCFN则以单钙钛矿结构为主,并有效抑制了碳沉积。单电池在CO燃料下的最大功率密度可达0.6 W/cm²(850℃),并在n(CO):n(CO₂)=5:1(摩尔比)燃料下运行超过100 h。     

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。     

Activation of methane using solid oxide membranes

Dense membranes of mixed-conducting perovskite-type oxides La_0.6Sr_0.4,CO_0.8Fe_0.2O₃ and La_0.8Ba_0.2Co_0.8Fe_0.2O₃ were used for methane coupling by application of pressure-driven O₂ permeation. High operating temperatures, typically above 800°C, were needed to obtain reasonable oxygen fluxes. Conversions were small (1–3%). Both compositions showed comparable C₂ selectivities at low methane partial pressures. At higher pressures the selectivity to C₂ hydrocarbons for La_0.6Sr_0.4CO_0.8Fe_0.2O₃ increased to 67%, whereas La_0.8Ba_0.2CO_0.8Fe_0.2O₃ showed small C₂ selectivities. Strong surface segregation of Sr and Ba was shown by SEM for both compositions.     

Influence of oxygen supply rates on performances of catalytic membrane reactors: Application to the oxidative coupling of methane

The impact of oxygen permeability using an ionic oxygen conducting membrane reactor with surface catalyst was investigated for the oxidative coupling of methane to higher hydrocarbons. Dense Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCFO), Ba_0.5Sr_0.5Mn_0.8Fe_0.2O_3−δ (BSMFO) and BaBi_0.4Fe_0.6O₃ (BBFO) membrane disks with Pt/MgO catalysts were prepared by sol–gel deposition or wash-coating. It is demonstrated that the oxygen supply by permeation needs to fit to the consumption during the coupling reaction. In case of insufficient oxygen supply comparably poor conversions are observed while higher oxygen fluxes lead to increased methane conversions, especially in the presence of an efficient catalyst. Generally, increasing catalytic activity leads to lower C₂ selectivity, especially for low oxygen permeation fluxes. The concept of a reactor employing dense catalytic membranes is viable, but the present study identifies further potential when the activity of the catalyst for the oxidative coupling is improved, leading to an overall enhanced performance of the membrane reactor.     

Study of Ag/La0.6Sr0.4MnO3 catalysts for complete oxidation of methanol and ethanol at low concentrations

Ag-modified La_0.6Sr_0.4MnO₃-based catalysts with the perovskite-type structure were prepared by using a citric acid sol–gel method, and their catalytic performance for complete oxidation of methanol and ethanol was evaluated and compared with that of the γ-Al₂O₃-supported catalysts, Ag/γ-Al₂O₃, Pt/γ-Al₂O₃, and Pd/γ-Al₂O₃. The results showed that the Ag-modified La_0.6Sr_0.4MnO₃-based catalysts with the perovskite-type structure displayed the activity significantly higher than that of the supported precious metal catalysts, 0.1%Pd/γ-Al₂O₃ and 0.1%Pt/γ-Al₂O₃ in the temperature range of 370–573 K. Over a 6%Ag/20%La_0.6Sr_0.4MnO₃/γ-Al₂O₃ catalyst, the T₉₅ temperature for methanol oxidation can be as low as 413 K. Even at such low reaction temperature, there were little HCHO and CO detected in the reaction exit-gas. However, for the 0.1%Pd/γ-Al₂O₃ and 0.1%Pt/γ-Al₂O₃ catalysts, the HCHO content in the reaction exit-gas reached 200 and 630 ppm at their T₉₅ temperatures. Over a 6%Ag/La_0.6Sr_0.4MnO₃ catalyst, the T₉₅ temperature for ethanol oxidation can be as low as 453 K, with a corresponding content of CH₃CHO in the exit-gas at 782 ppm; when ethanol oxidation is performed at 493 K, the content of acetaldehyde in the exit-gas can be below 1 ppm. Characterization of the catalysts by X-ray diffraction (XRD), TEM, XPS, laser Raman spectra (LRS), hydrogen temperature-programmed reduction (H₂-TPR) and oxygen temperature-programmed desorption (O₂-TPD) methods revealed that both the surface and the bulk phase of the perovskite La_0.6Sr_0.4MnO₃ played important roles in the catalytic oxidation of the alcohols, and that γ-Al₂O₃ as the bottom carrier could be beneficial in creating a large surface area of catalyst. Moreover, a small amount of Ag⁺ doped onto the surface of La_0.6Sr_0.4MnO₃ was able to partially occupy the positions of La³⁺ and Sr²⁺ due to their similar ionic radii, and thus, became stabilized by the perovskite lattice, which would be in favor of preventing the aggregation of the Ag species on the surface and enhancing the stability of the catalyst. On the other hand, modification of the Ag⁺ to the surface of La_0.6Sr_0.4MnO₃ resulted in an increase in relative content of the surface O₂²⁻/O⁻ species highly reactive toward the alcohols and aldehydes as well as CO. Besides, solution of low-valence metal oxides SrO and Ag₂O with proper amounts in the lattice of the trivalent metal perovskite-type oxide LaMnO₃ would also lead to an increase in the content of the reducible Mnⁿ⁺ and the formation of anionic vacancies, which would be favorable for the adsorption-activation of oxygen on the functioning catalyst and the transport of the lattice and surface oxygen species. All these factors would contribute to the pronounced improvement of the catalyst performance.     

Synthesis, characterization and catalytic activity for NO–CO reaction of Pd–(La, Sr)2MnO4 system

La_xSr_2−xMnO₄ (0 ≤ x ≤ 0.8) oxides were synthesized and single-phase K₂NiF₄-type oxides were obtained in the range of 0.1 ≤ x < 0.5. The catalytic activity of La_xSr_2−xMnO₄ for NO–CO reaction increased with increasing x in the range of solubility limit of La. La_0.5Sr_1.5MnO₄ showed the highest activity among La_xSr_2−xMnO₄ prepared in this study, but its activity was inferior to perovskite-type La_0.5Sr_0.5MnO₃. Among the Pd-loaded catalysts, however, Pd/La_0.8Sr_1.2MnO₄ showed the higher activity and the selectivity to N₂ than Pd/La_0.5Sr_0.5MnO₃ and Pd/γ-Al₂O₃. The excellent catalytic performance of Pd/La_0.2Sr_1.2MnO₄ could be ascribable to the formation of SrPd₃O₄ which was detected by XRD in the catalyst but not in the other two catalysts.     

La2O3/AC催化剂在CO同时还原SO2和NO反应中的性能

以改性活性炭为载体,采用等体积浸渍法制备了La₂O₃/AC催化剂。采用XRD和BET手段对催化剂进行表征,使用微型固定床反应器考察催化剂的脱硫脱硝活性。结果表明,La₂O₃/AC催化剂对CO同时还原SO₂和NO具有良好活性,负载质量分数10%的La₂O₃/AC催化剂活性较好,SO₂和NO转化率达到90%的反应温度最低,分别为335 ℃和325 ℃;载体与活性组分之间存在协同作用,引入活性炭载体能够降低反应温度并提高催化活性。     

Decomposition of nitric oxide over perovskite oxide catalysts: effect of CO2, H2O and CH4

Direct nitric oxide decomposition over perovskites is fairly slow and complex, its mechanism changing dramatically with temperature. Previous kinetic study for three representative compositions (La_0.87Sr_0.13Mn_0.2Ni_0.8O_3−δ, La_0.66Sr_0.34Ni_0.3Co_0.7O_3−δ and La_0.8Sr_0.2Cu_0.15Fe_0.85O_3−δ) has shown that depending on the temperature range, the inhibition effect of oxygen either increases or decreases with temperature. This paper deals with the effect of CO₂, H₂O and CH₄ on the nitric oxide decomposition over the same perovskites studied at a steady-state in a plug-flow reactor with 1 g catalyst and total flowrates of 50 or 100 ml/min of 2 or 5% NO. The effect of carbon dioxide (0.5–10%) was evaluated between 873 and 923 K, whereas that of H₂O vapor (1.6 or 2.5%) from 723 to 923 K. Both CO₂ and H₂O inhibit the NO decomposition, but inhibition by CO₂ is considerably stronger. For all three catalysts, these effects increase with temperature. Kinetic parameters for the inhibiting effects of CO₂ and H₂O over the three perovskites were determined. Addition of methane to the feed (NO/CH₄=4) increases conversion of NO to N₂ about two to four times, depending on the initial NO concentration and on temperature. This, however, is still much too low for practical applications. Furthermore, the rates of methane oxidation by nitric oxide over perovskites are substantially slower than those of methane oxidation by oxygen. Thus, perovskites do not seem to be suitable for catalytic selective NO reduction with methane.