不同焙烧温度制备的类钙钛矿型复合氧化物La2NiO4的性能研究

本文采用溶胶-凝胶法在不同温度下制备了纳米级的类钙钛矿型复合氧化物La2NiO4.采用XRD、TPR、SEM和TG-DTA等实验技术对催化剂进行了表征,并且考察了该催化剂对CH4/CO2重整反应的催化活性.实验结果表明高于850 ℃焙烧制备的La2NiO4催化剂,其催化活性、稳定性及抗积炭性能较好.     

类钙钛矿型复合氧化物La_2NiO_4的制备和性能研究

采用共沉淀法、硝酸盐分解法、溶胶-凝胶法3种不同的方法制备了纳米级的类钙钛矿型复合氧化物La2NiO4;采用XRD、SEM、BET等实验技术对催化剂进行了表征,并且考察了该催化剂对CH4/CO2重整反应的催化活性。实验结果发现,不同方法制备的催化剂在粒子大小、比表面积、催化活性等方面存在差异,其中溶胶-凝胶法制备的催化剂表现较好。     

钙钛矿型复合氧化物对甲烷的部分氧化及在混合太阳能氧化还原过程的应用

利用固相法合成了3种钙钛矿型复合氧化物Fe2O3-CaTixM1?xO3,研究了其结构、晶型和氧化还原活性。在固定床反应器中考察了该氧化物对两步法甲烷催化氧化制合成气及水分解制氢的活性及选择性。X射线衍射结果表明3种钙钛型复合氧化物均由正交晶系钙钛矿相和赤铁矿相组成。3种钙钛矿复合氧化物对甲烷的氧化活性顺序为Fe2O3-CaTi0.85Ni0.15O3Fe2O3-CaTi0.85Co0.15O3Fe2O3-CaTi0.85Fe0.15O3。固定床反应结果表明,以Fe2O3-CaTi0.85Ni0.15O3为氧载体催化剂,CH4转化率可达96%,CO和H2产率达71%,同时水分解反应的转化率为40%。利用Aspen Plus?对Fe2O3-CaTi0.85Ni0.15O3在混合太阳能氧化还原过程的效率及合成油和H2产率进行了模拟。模拟计算结果证明基于复合氧化物的混合太阳能氧化还原过程可以有效提高CH4利用率。     

A2BO4类钙钛矿型复合氧化物在催化领域的应用研究进展

概述了A₂BO₄类钙钛矿型复合氧化物的结构和性能，与ABO₃钙钛矿型氧化物进行了比较，简述了类钙钛矿型复合氧化物的制备方法和对复合氧化物的结构以及性能的影响，重点介绍了Ni系、Cu系和Co系等A₂BO₄型复合氧化物在尾气净化、NOx消除、氧化反应和甲烷氧化偶联等催化领域中的应用。     

纳米Ni/MgO催化剂在CO_2重整CH_4反应中影响因素的研究

采用纳米Ni/MgO催化剂,在CO2重整CH4反应中,研究了还原温度、还原时间、反应温度、镍含量和空间速度等因素对反应的影响,结果表明,在适宜的反应条件下,纳米Ni/MgO催化剂具有很好的活性和稳定性。     

钙钛矿型复合氧化物对甲烷的部分氧化及在混合太阳能氧化还原过程的应用

利用固相法合成了3种钙钛矿型复合氧化物Fe₂O₃-CaTi_xM_1-xO₃,研究了其结构、晶型和氧化还原活性。在固定床反应器中考察了该氧化物对两步法甲烷催化氧化制合成气及水分解制氢的活性及选择性。X射线衍射结果表明3种钙钛型复合氧化物均由正交晶系钙钛矿相和赤铁矿相组成。3种钙钛矿复合氧化物对甲烷的氧化活性顺序为Fe₂O₃-CaTi_0.85Ni_0.15O₃ >Fe₂O₃-CaTi_0.85Co_0.15O₃ >Fe₂O₃-CaTi_0.85Fe_0.15O₃。固定床反应结果表明,以Fe₂O₃-CaTi_0.85Ni_0.15O₃为氧载体催化剂,CH₄转化率可达96%,CO和H₂产率达71%,同时水分解反应的转化率为40%。利用Aspen Plus^®对Fe₂O₃-CaTi_0.85Ni_0.15O₃在混合太阳能氧化还原过程的效率及合成油和H₂产率进行了模拟。模拟计算结果证明基于复合氧化物的混合太阳能氧化还原过程可以有效提高CH₄利用率。     

钙钛矿型La_（1-x）AxCoO_3的制备及其对CH_4燃烧的催化性能

用Na2CO3.10H2O和NaOH混合碱为沉淀剂制得了钙钛矿型结构的La1-XAxCoO3（A：Sr,Ba,Dy,Y;X：0,0.1,0.2）复合氧化物,考察了焙烧温度对催化剂结构和催化活性的影响,发现A位取代后可使催化剂对CH4的催化氧化活性提高;通过与柠檬酸络合法制得的La1-xAxCoO3复合氧化物比较,比较制备方法对催化剂的催化活性也有很大的影响。     

煤层气转化制合成气Ni基催化剂的研究

采用10%Ni/4%MgO-Al2O3催化剂,在常压固定床反应器上进行CO2重整CH4制合成气反应的研究;系统考察了载体制备方法、MgO含量、焙烧温度及焙烧方式等因素对催化剂性质的影响;并采用N2物理吸附、XRD等检测手段对催化剂进行了表征。结果表明,采用共沉淀法,MgO质量分数为4%,在FAir中550℃下焙烧4 h的10%Ni/4%MgO-Al2O3的催化活性较好,CH4和CO2的转化率可以达到82%和92%。     

Mg、Ce修饰纳米Al_2O_3负载Ni催化剂对CH_4、CO_2重整反应制合成气的影响

考察了助剂Mg、Ce修饰的纳米A l2O3负载N i催化剂对CH4、CO2重整反应制合成气的反应性能影响,采用正交实验筛选催化剂。结果表明,N i含量在9%~13%时,催化剂表现出较好的活性;随Mg含量的增加,反应活性基本呈下降趋势,说明Mg降低了催化剂体系的反应性能;Ce的加入总体上提高了反应活性,但是当Ce含量为3%时,反应活性最好;从不经预还原实验和低温点反应实验推断出,CH4和CO2重整反应中关键反应步骤是CH4的裂解;助剂Ce有利于提高催化剂的稳定性,而Mg却会使催化剂的稳定性下降很快。     

nx：ny对PdO／CexZryO2催化剂三效催化性能的影响

采用溶胶-凝胶法制备了一系列CexZryO2(x=0～1,y=1～x)复合氧化物,并以该复合氧化物为栽体制备负栽贵金属的PdO/CexZryO2催化剂,选择NO-CO反应和CO以及CH4氧化反应为模型反应对催化剂的三效催化性能进行评价,并通过XRD、H2-TPR等手段对栽体和催化剂进行初步表征.结果表明:nx:ny对CexZryO2栽体及负栽PdO催化剂三效催化性能均存在重要影响,不同nx:ny的CexZryO2复合氧化物栽体具有不同的晶相结构及还原性能,由其负载的PdO催化剂也各不相同.同时,催化剂的NO还原活性与CO氧化活性与α还原峰存在一定的对应关系.     

Rh(1%)@CexZr1−xO2–Al2O3 nanocomposites: Active and stable catalysts for ethanol steam reforming

Rh(1%)@Ce_xZr_1−xO₂–Al₂O₃ nanocomposites have been investigated as active and thermally stable catalysts for ethanol steam reforming. Preformed Rh nanoparticles have been efficiently protected from deactivation/sintering by a porous layer of nanocomposite oxides. Chemisorption and activity data confirm the good accessibility of the metal phase to the reaction mixture. No appreciable deactivation is observed after 160 h of reaction at 873 K. The ceria–zirconia mixed oxides favour reforming reactions, reduce coke formation and facilitate its removal. The alumina component is important to stabilize the ceria–zirconia mixed oxides, preventing their sintering.     

Effect of support on the conversion of methane to synthesis gas over supported iridium catalysts

A partial oxidation of methane was carried out using iridium catalysts supported on several metal oxides. The productivity of the synthesis gas from methane was strongly affected by the choice of support oxides for the catalysts. The synthesis gas production proceeded basically via a two-step reaction consisting of methane combustion to give H₂O and CO₂, followed by the reforming of methane from CO₂ and steam. Although the combustion and the reforming of methane from steam did not depend upon the catalyst support, a large variation in the catalytic activity for the reforming of methane from CO₂ was observed over Ir catalysts with different supports. The support activity order in the reforming of methane from CO₂ with iridium catalysts was as follows: TiO₂≧ZrO₂≧Y₂O₃>La₂O₃>MgO≧Al₂O₃>SiO₂. The same order was observed in the synthesis gas production from the partial oxidation of methane. This revised version was published online in August 2006 with corrections to the Cover Date.     

CeO2的制备及其在催化剂载体中的应用研究进展

概述了 CeO₂的制备方法对其性能的影响以及CeO2在催化剂载体中的运用,指出 CeO₂独特的储放氧性能使其在氧化反应、甲醇裂解、重整及变换反应和氮氧化物的还原等反应过程中呈现了良好的载体功能;溶胶-凝胶法以及超临界干燥等方法可以制备大比表面积的载体 CeO₂。制约载体 CeO₂工业应用的因素在于其机械强度和耐热性。     

Resistance to Coking Determination by Temperature Programmed Reaction of n-Butane with Steam

Resistance to coking is one of the most important characteristics of nickel catalysts used for steam reforming of hydrocarbons, CO₂ reforming or methanation of carbon oxides. Microbalance reactors have for a long time played an important role in catalyst deactivation studies, providing coking and coke gasification rates. However, conventional thermogravimetric microbalances have a number of limitations. The aim of this paper is to compare initial temperatures of coking of Ni and Ni-Mo catalysts (with different resistance to coking) obtained in the temperature-programmed reaction of _n-butane with steam with the results of coking rates obtained by the traditional thermogravimetric method. The investigations showed great agreement of the results.     

Cu-based spinel catalysts CuB2O4 (B = Fe, Mn, Cr, Ga, Al, Fe0.75Mn0.25) for steam reforming of dimethyl ether

Cu-based spinel-oxides CuB₂O₄ (B = Fe, Mn, Cr, Ga, Al, or Fe_0.75Mn_0.25) were synthesized via a sol–gel method and subsequent solid-state reaction. The spinels mechanically mixed with γ-Al₂O₃ were evaluated for production of hydrogen from dimethyl ether steam reforming (DME SR). The reduction behavior and crystal property of these spinel-oxides, and the Cu oxidation state in spinel catalysts were investigated by temperature-programmed reduction, X-ray diffraction, and X-ray photoelectron spectroscopy techniques. The reduced phases of the Cu-based spinel catalysts that strongly affected the catalytic activity and durability were composed of metallic copper with metal oxides (MnO (B = Mn), Cr₂O₃ (B = Cr), and Al₂O₃ (B = Al)) or with spinels (CuGa₂O₄ (B = Ga), Fe₃O₄ (B = Fe), and MnFe₂O₄ (B = Fe_0.75Mn_0.25). The stability of B metal oxides and the interaction between copper species and B metal oxides significantly contributed to the reforming performance.     

The role of oxygen and hydroxyl support species on the mechanism of H2 production in the steam reforming of phenol over metal oxide-supported-Rh and -Fe catalysts

The aim of this work was to probe for the first time the back-spillover of labile O and OH species during steam reforming of phenol towards H₂ production over Rh and Fe supported on MgO, Mg-Ce-O and Mg-Ce-Zr-O metal oxides. This was made possible through SSITKA and other transient isotopic experiments (use of D₂O and ¹⁸O₂). The size of the active pool of H-containing species (H and/or OH) present under reaction conditions as a function of reaction T and catalyst composition, and deuterium kinetic isotope effects were measured.     

Fischer-Tropsch synthesis on the cobalt impregnated catalyst using carbon-coated Ni/SiO<Subscript>2</Subscript>

Carbon-coated Ni/SiO₂ prepared by dry reforming of CH₄ with CO₂ was applied for the preparation of the cobalt-based Fischer-Tropsch synthesis (FTS) catalyst with 20 wt%Co to elucidate the metal-support interaction to FTS activity after carbon depositions on the Ni/SiO₂. The deposited carbons on the reforming catalyst of Ni/SiO₂, which were mainly in the form of filamentous or encapsulated carbons, largely increased CO conversion compared with the fresh Ni/SiO₂ without a significant variation of hydrocarbon distributions. The deposited carbons on the Ni/SiO₂ play an important role in increasing the reducibility of cobalt oxides due to a mitigated metal-support interaction. The enhanced catalytic activity during FTS reaction is mainly attributed to the proper modification of the Ni/SiO₂ surfaces with encapsulated carbons on the exposed nickel surfaces, which largely alters the reducibility of cobalt oxides by reducing the interaction of cobalt particles with the carbon-coated Ni/SiO₂ surfaces.     

Metal oxide catalysts for DME steam reforming: Ga2O3 and Ga2O3–Al2O3 catalysts

The steam reforming of dimethyl ether (DME) was performed on Ga₂O₃–Al₂O₃ mixed oxides prepared by sol–gel method. Ga₂O₃ significantly affects the catalytic performance with respect to the DME conversion and H₂ yield. The catalytic activity increases with the Ga concentration in Ga₂O₃–Al₂O₃ mixed oxides. It is very interesting that without the aid of an additional transition metal component, Ga₂O₃ and Ga₂O₃ containing Al₂O₃ mixed oxide system exhibit good activity in the reforming reaction. To the best of our knowledge, this is the first report that reveals the reforming ability of Ga₂O₃ for the production of H₂ from DME and/or methanol.     

Investigation of Ni/Ce-ZrO2 catalysts in the autothermal reforming of methane

Nickel catalysts supported on α-Al₂O₃, CeO₂, ZrO₂ and Ce-ZrO₂ were investigated in the autothermal reforming of methane. Ce-ZrO₂ supports formed a solid solution and presented better oxygen storage capacity per unit of mass of Ce when compared to CeO₂. Diffuse reflectance UV-Vis spectroscopy spectra and temperature-programmed reduction profiles, showed the presence of Ni²⁺ in tetrahedral and octahedral geometries for catalysts supported on mixed oxides. Temperature-programmed surface reaction experiments showed that the catalytic activity for autothermal reforming is proportional to the amount of metallic sites on the surface. However, when operating under severe coking conditions, catalysts with a higher oxygen storage capacity were more stable in the autothermal reforming of methane. Time-differential angular correlation experiments provided an atomic view on how the mobility of oxygen on CeZrO₂ is enhanced by the presence of Ni, which increases the stability of the catalyst.