Ce0.67Zr0.33O2对CH4燃烧催化剂Fe2O3/Al2O3的改性作用

固定n(Ce)/n(Zr)比为0.67/0.33,用共沉淀法制得一系列CeO2-ZrO2-Al2O3固溶体.采用这些固溶体作载体,以Fe2O3为活性组分,用浸渍法制备了一系列催化剂.BET结果显示,将适量Ce0.67Zr0.33O2引入到Al2O3载体中有助于催化剂保持较高的比表面积.TPR结果显示,载体中引入适量的Ce0.67Zr0.33O2可以改善催化剂的氧化还原性能.XRD结果表明,Fe2O3在CeO2-ZrO2-Al2O3载体上呈现出良好的分散状况,老化前后催化剂的晶相结构基本无明显变化.特别是当载体中m(Ce0.67Zr0.33O2)∶m(Al2O3)的值为1∶2时,Fe2O3/CeO2-ZrO2-Al2O3催化剂在甲烷催化燃烧中显示出最佳的催化性能和抗高温老化性能.     

Cu/SO42-/La2O3-ZrO2-Al2O3催化剂的制备及其对C3H6选择还原NO的催化性能

以Al₂O₃为基质，添加ZrO₂和La₂O₃，制成La₂O₃-ZrO₂-Al₂O₃复合载体，然后采用SO₄^2-进行改性，再负载上Cu²⁺，制备了铜基SO₄^2-改性的复合载体催化剂(Cu/SO₄^2-/La₂O₃-ZrO₂-Al₂O₃)。考察了它在富氧条件下对丙烯选择还原NO的催化性能，并借助XRD、SEM、TG、Py-IR、NH₃-TPD、FTIR和TPR等方法研究了Cu/SO₄^2-/La₂O₃-ZrO₂-Al₂O₃的结构和性能的关系。结果表明，ZrO₂的加入主要有利于提高催化剂的低温活性；La₂O₃的加入则主要有利于提高催化剂的热稳定性和还原性能；SO₄^2-能够与Zr形成螯合双配位结构，大幅度促使催化剂表面酸量增加并且酸性增强；因此，有效地提高了Cu/SO₄^2-/La₂O₃-ZrO₂-Al₂O₃在富氧条件下对丙烯选择还原NO的催化活性和水热稳定性。在无水条件下，Cu/SO₄^2-/La₂O₃-ZrO₂-Al₂O₃能使NO的最大转化率高达84.3%，即使在275 ℃ 10%水蒸气存在的情况下，仍能使NO的转化率高达81.2%。     

整体式Co3O4/YSZ- -Al2O3＋CYZ催化剂上的甲烷催化燃烧

用质量比为3∶2的YSZ-γ-Al₂O₃和CeO₂-Y₂O₃-ZrO₂的混合物(以YSZA＋CYZ表示)作载体, 制备了不同Co₃O₄含量的整体式甲烷燃烧催化剂, 同时制备了分别以YSZA和CYZ为载体的催化剂作为对比, 研究了它们老化前后的反应性能, 并用BET, XPS, XRD, TPR等研究了催化剂的比表面、表面状态、晶相结构和还原性能. 结果表明, YSZ- -Al₂O₃和CeO₂-Y₂O₃-ZrO₂混合载体能有效地抑制CoAl₂O₄的生成, 并能充分发挥各自的优点, 因此负载一定量的钴后表现出很高的甲烷催化燃烧活性和抗老化性, 尤其是含8 wt% Co₃O₄的样品性能最佳, 有望成为实用的甲烷燃烧催化剂之一.     

高分散CuO/CeO2-Al2O3催化剂中铜物种的精细结构表征

采用化学吸附-水解法制备了系列CuO/CeO₂-Al₂O₃催化剂，运用XANES、EXAFS、XRD和H2-TPR等方法对催化剂的结构进行了表征，探讨了不同焙烧温度对催化剂中高分散Cu物种的微观局域结构、分散状态和存在形式的影响，并与样品的CO氧化性能关联。结果表明，500 ℃焙烧样品中Cu物种主要以高分散的CuO微晶形式存在，与载体及CeO₂的作用相对较弱；当焙烧温度提高至650 ℃，存在3种铜物种，即与Al相似文献   

Al2O3-ZrO2复合膜的制备与表征

以异丙醇铝和氧氯化锆为原料,用溶胶-凝胶法在Al₂O₃中空纤维上制备了Al₂O₃-ZrO₂复合膜。应用TG、DTA、XRD、SEM等测试手段对复合膜的热稳定性、结构、形貌进行了表征。结果表明复合膜的热稳定性比单一由氧化铝或氧化锆制成的膜有显著的提高,在1100℃之前,复合膜以t-ZrO₂存在,1200℃时,出现了m-ZrO₂和α-Al₂O₃相。扫描电镜分析表明,膜表面完整、无缺陷。气体渗透实验进一步表明所得膜具有一定的气体选择性,0.3MPa和0.5MPa下对氮气和氩气的分离因子α分别为1.191和1.185,和氮气与氩气的理论分离因子(α=1.194)相当,说明气体通过膜的扩散以Knudsen扩散传质为主。用等温氮气吸附实验测定了非担载膜的孔径大小和分布,最可几孔径约为4.3nm。     

CeO2-ZrO2复合氧化物的制备及协同抛光性能

Sub-micrometer ultra fine CeO₂-ZrO₂ mixed oxides have been prepared by milling solid cerium carbonate and zirconium oxy-chloride with ammonia and followed by filtering, drying and calcining procedures. The effects of Ce/Zr molar ratio, milling time and calcining temperature on the phase composition, particle size and morphology, surface charge, as well as the polishing property were investigated. The results show that the mixed oxide calcined at 1 000 ℃ is composed of cubic ceria doped with zirconium and tetragonal zirconia doped with cerium, and the phase composition varies with calcination temperature and the Ce/Zr molar ratio. The monoclinic zirconia is observed when decreasing calcination temperature and shortening milling time, demonstrating that milling and calcining can force the phase transformation from monoclinic zirconia to cerium stabilized tetragonal zirconia and zirconium doped cubic ceria solid solutions. The removal rate for the optical glass polishing varies with Ce/Zr molar ratio. A synergetic polishing effect is found when Ce/Zr molar ratio below 4, and the optimal Ce/Zr molar ratio is 1∶1. At the same time, the cubic ceria content, density, particle size and surface charge all increase when calcination temperature increasing from 800 ℃ to 1 100 ℃. However, the particle morphology changes from disperse quasi-sphere to irregular aggregation and the maximal removal rate for optical glass polishing lies at 1 000 ℃.These facts show that the polishing property of the synthesized ceria-zirconia mixed oxide is affected by the particle physical characteristics comprehensively.     

B2O3/TiO2-ZrO2的结构表征及其与酸性和催化性能间的关系

采用XRD、N₂吸附、 ¹¹B MAS NMR、NH₃-TPD和催化性能评价等方法研究了B₂O₃/TiO₂-ZrO₂催化剂的结构、酸性及催化环己酮肟气相Beckmann重排反应性能间的关系。结果表明,催化剂中的B₂O₃同时以三配位的BO₃和四配位的BO₄结构单元存在;     

环己酮肟气相Beckmann重排反应B2O3/TiO2-ZrO2催化剂的失活与再生

对环己酮肟气相Beckmann重排反应制己内酰胺B₂O₃/TiO₂-ZrO₂催化剂的失活原因和再生方法进行了研究。通过对失活催化剂进行N₂吸附、XRD、NH₃-TPD等表征后发现，引起催化剂失活的主要原因是催化剂表面因积炭所引起的酸性改变。失活催化剂在600℃于空气气氛中焙烧8h可完全恢复到新鲜催化剂的水平。     

预处理气氛对CuO/CeO2/γ-Al2O3催化剂表面性质及“NO+CO”反应性能的影响

用不同的预处理气氛制备了CeO₂/γ-Al₂O₃载体以调节表面Ce的价态,并以Cu(CH₃COO)₂为前驱体制备了CuCeAl催化剂。XRD和H₂-TPR的结果表明在还原气氛下处理的CeO₂/γ-Al₂O₃载体具有更多的活性氧原子,因此相应的CuCeAl催化剂表面有更多分散态的Cu²⁺/Cu⁺物种。NO+CO反应的结果表明分散态的Cu²⁺/Cu⁺是NO转化的活性物质,而Cu⁰在低温下具有较好的N₂选择性。因此,同时含有分散态Cu²⁺/Cu⁺和少量晶相Cu⁰的催化剂具有最好的催化性能。     

碳纳米管负载的Fe2O3催化剂制备

Carbon nanotubes were modified by FeSO₄-H₂O₂ system, iron hydroxides were adsorbed on the wall of carbon nanotubes simultaneously. These precursors were treated at 723K for 2 h under hydrogen, nitrogen and air atmosphere to prepare carbon nanotubes supported γ-Fe₂O₃catalyst, γ-Fe₂O₃and α-Fe₂O₃compound catalyst and amorphous Fe₂O₃catalyst, respectively. This is green method to prepare high Fe₂O₃loading (≥50 %) catalyst without adding other cation. The different structures Fe₂O₃catalysts can be synthesized by controlling the condition of thermal treatment to content active phase requirements for different catalytic reactions. The paper presents a new method to prepare carbon nanotubes supported catalysts.     

La2O3对CuO/CeO2水煤气变换反应催化剂微观结构及催化性能的影响（英文）

以La2O3为助剂,采用共沉淀法制备了具有良好催化活性和热稳定性的CuO/CeO2-La2O3水煤气变换反应催化剂,其中,当La2O3含量为2wt%时,催化剂的催化性能最为优异.同时运用X射线衍射、N2吸附-脱附、Raman光谱、程序升温还原等手段,研究了不同含量的La2O3对CuO/CeO2催化剂微观结构及催化性能的影响.结果表明,La2O3助剂进入了载体CeO2的晶格并对CuO/CeO2催化剂的微观结构和催化性能产生了直接影响,适量La2O3的添加可以抑制CuO和CeO2晶格的长大、增强CuO与CeO2间的相互作用、提高催化剂的比表面积、促进CeO2载体中生成更多的氧空位,CuO/CeO2催化剂的催化活性和热稳定性也明显改善.     

负载型Pd三效催化剂：载体CeO2-ZrO2-BaO的制备及催化性能

制备了不同BaO含量的CeO2-ZrO2储氧材料,并以此材料为载体浸渍H2PdCl6制得三效催化剂.结果表明,不论新鲜还是1 000 ℃老化状态下,以10%BaO添加CeO2-ZrO2储氧材料制备的Pd三效催化剂活性最佳,起燃和完全转化温度最低.XPS结果证实,10%BaO添加.通过稳定PdO活性组分并改变其电子环境使得催化剂有最佳活性.而随着BaO含量持续增加,Pd活件组分相对处于较氧化状态.储氧量、低温N2吸附-脱附测试以及XRD测试结果均表明10%BaO添加的材料储氧量,比表面积以及孔容均最大,而且有适应三效催化的孔径.这些结果均有助于以其制备的Pd三效催化剂获得更好的活性以及热稳定性.     

表面覆盖SiO2用于提高Pt-Pd/CeO2-ZrO2-Al2O3商用柴油机氧化型催化剂的抗硫性

向Pt-Pd/CeO₂-ZrO₂-Al₂O₃ （Pt-Pd/CZA）商用柴油机氧化型催化剂（DOC）中加入多孔SiO₂以提高其抗硫性. 使用多层涂覆法在Pt-Pd/CZA 催化剂表面覆盖一层多孔SiO₂,从而制得SiO₂/Pt-Pd/CeO₂-ZrO₂-Al₂O₃（SiO₂/Pt-Pd/CZA）抗硫DOC. 并使用扫描电子显微镜（SEM）,H₂程序升温还原（H₂-TPR）,氮气吸脱附,X射线能谱（EDX）和热重分析（TGA）等对其进行表征. SEM结果显示,SiO₂层以多孔形式均匀覆盖在催化剂表面. 氮气吸脱附结果表明,所添加的SiO₂的织构性质与Pt-Pd/CZA 催化剂的织构性质相似,因而表面覆盖的SiO₂并未明显改变Pt-Pd/CZA催化剂的比表面积和孔结构. H₂-TPR结果证实表面覆盖的SiO₂不影响Pt-Pd/CZA催化剂的还原性能. EDX和TGA结果说明表面覆盖SiO₂可以抑制硫物种在催化剂表面的形成及累积. 最终,本文所制备的SiO₂/Pt-Pd/CZA催化剂在保持Pt-Pd/CZA商用DOC的高活性及耐久性的同时有效提高了其抗硫性.     

Effect of La2O3 on a Precipitated Iron Catalyst for Fischer-Tropsch Synthesis

A series of La₂O₃-promoted precipitated iron catalysts (100Fe/2.8Si/nLa, n = 0, 0.5, 1, 2, and 4, atomic ratio) were prepared and characterized by in situ X-ray diffraction, CO temperature-programmed reduction, and N₂ adsorption-desorption. The catalytic performance for Fischer-Tropsch synthesis was studied in a fixed-bed reactor. It was found that the addition of a small amount of La₂O₃ (La/Fe ≤ 0.01) gave a large decrease in the particle size of Fe₂O₃, which increased the specific surface area and dispersion of the catalysts. This also favored the formation of iron carbides, which gave a high catalytic activity in Fischer-Tropsch synthesis. With increasing La₂O₃ content (La/Fe ≥ 0.02), a high La₂O₃ coverage and the formation of a LaFeO₃ compound decreased the formation of iron carbides, and the reaction activity decreased. The optimum La₂O₃ content was La/Fe = 0.01. The addition of La₂O₃ increased the selectivity for methane and suppressed the formation of C₅₊ hydrocarbons.     

碱性CeO2载体对Ru/CeO2催化剂氨合成活性的影响

钌基催化剂因其在低温低压下具有比常规的铁基催化剂更具活性的特点成为合成氨催化剂的理想选择.我们研究了CeO₂载体表面碱性对Ru基合成氨催化剂的影响.通过调节KOH沉淀剂的量来制备具有不同碱性位点的CeO₂载体（pH=10/11/12）,证明了催化剂适当碱性位点密度提高了合成氨催化活性.催化性能测试结果表明,1.25% Ru/CeO₂-11催化剂在3.8 MPa,450℃,H₂/N₂=3（60 mL·min^-1）下表现出优异的氨合成活性（7040 μmol·g^-1·h^-1）.CeO₂-11的碱性位点增强了载体的电子给予能力,这有利于电子向活性金属Ru转移,从而促进了N₂的活化.碱金属和碱土金属的引入提高了活性金属Ru的还原能力.4% Cs-1.25% Ru/CeO₂-11（12 000 μmol·g^-1·h^-1）催化剂具有更多的氧空位,这增加了Ru周围的电子密度并促进了N≡N的裂解.通过XRD,BET,SEM,CO₂-TPD,H₂-TPR和XPS分析了不同碱性CeO₂载体对合成氨催化反应的影响.     

Effect of CeO2 and CaO Promoters on Ignition Performance for Partial Oxidation of Methane over Ni/MgO-Al2O3 Catalyst

The effect of CeO2 and CaO promoters on the ignition performance over Ni/MgO-Al2O3 catalyst for the partial oxidation of methane （POM） to synthesis gas was investigated. It was found that the POM reaction could not be ignited over lwt%Ni/MgO-Al2O3 catalyst without the promoters in the temperature range from 773 K to 1073 K. CeO2 and CaO promoters enhanced the ignition performance and the POM reactivity of lwt%Ni/MgO-Al2O3 catalyst remarkably. Moreover, the improving effect became greater with the increase of the promoter content under the investigated reactiorrconditions. The modification effects of CeO2 and CaO promoters were closely related to the concentration and reducibility of the surface and bulk oxygen species.     

La2O3对Ni/γ-Al2O3甲烷化催化剂的助催化作用

我国将稀土作为助剂引入镍基甲烷化催化剂,大大提高了催化剂的活性和热稳定性,并已投入工业应用［1－3］．稀土对不同镍催化剂反应性能及其作用机理的研究已有一些报导［3－7］．谢有畅等观察到镍负载在经单层La2O3改性的γ－Al2O3表面,其晶粒要比没有La2O3时小得多．Rotgerink等认为添加La后反应速率的增加不只是由于几何效应,而是La对甲烷化本身有促进作用,单位镍表面的活性是随La含量不同而改变的,活性增加的同时表观活化能也增加［5］．作为助剂的La2O3在氢还原和反应过程中的变化及其作用的研究和讨论较少,目前一般认为添…     

负载催化剂SmMn2O5/γ-Al2O3负载量对NO氧化的影响

贵金属催化剂对NO_x催化氧化具有优异的催化性能,但催化剂成本较高,而负载型催化剂及非贵金属催化剂受到了广泛的关注。 本文中采用水热法和浸渍法分别制备了SmMn₂O₅纯相催化剂和SmMn₂O₅/γ-Al₂O₃负载催化剂,探索了活性成分SmMn₂O₅含量对NO催化氧化的影响。 对负载SmMn₂O₅不同质量分数(5%~100%)的复合催化剂进行了扫描电子显微镜、比表面积、孔径分布、程序升温还原和程序升温脱附的表征以及NO催化氧化的研究。 当SmMn₂O₅负载量小于50%(35%、25%、15%、5%)时,负载量为25%的催化剂显示出最低的燃点温度(260 ℃),继续增加负载量到50%和75%,与负载25%的复合催化剂相比,起燃温度降低10 ℃,仅高于纯相催化剂40 ℃。 该探索对于SmMn₂O₅催化剂的有效利用将具有一定的指导作用,并为负载型非贵金属催化剂的设计提供一定的思路。     

Effect of La2O3 on Catalytic Performance of Au/TiO2 for CO Oxidation

Pure TiO₂ and La-doped TiO₂ were prepared by the sol-gel method. Au was supported on TiO₂ by the deposition-precipitation (DP) method, and its catalytic activity for CO oxidation was tested. The results showed that doping La in Au/TiO₂ could improve its catalytic activity obviously for CO oxidation. The analyses of X-ray diffraction (XRD), temperature-programmed desorption (TPD), and Brunauer-Emmett-Teller (BET) surface area further showed that the presence of La in TiO₂ not only increased its surface area and restrained the growth of TiO₂ crystallites, but could also enhance the microstrain of TiO₂. In terms of O₂-TPD, a new adsorbed species O⁻ appeared on the surface of La-doped TiO₂. The results of in-situ Fourier transform-infrared (FT-IR) spectroscopy illustrated that the high activity of Au/La₂O₃-TiO₂ was attributed to the presence of La promoting the reactivity of CO adsorbed on the Au site and the formation of the second active site on the surface of TiO₂     

La2O3助剂对Au/TiO2催化氧化CO性能的影响

采用溶胶-凝胶法制备了TiO2以及La2O3-TiO2载体, 再用沉积沉淀法制备Au/TiO2和Au/La2O3-TiO2催化剂, 并对催化剂的CO氧化反应活性进行测试. 结果表明, La2O3助剂可以显著提高催化剂催化氧化CO的活性. X射线衍射(XRD)、程序升温脱附(TPD)、N2吸附-脱附(BET)表征结果表明, La2O3助剂不仅提高了催化剂比表面积, 抑制了TiO2晶粒尺寸的长大, 并且增强了TiO2的晶格应变, 在O2气氛吸附过程中主要在TiO2表面形成O-物种. 原位傅立叶变换红外(FT-IR)结果进一步表明, La的掺杂不仅提高了吸附在Au活性位CO的氧化速率, 还使TiO2表面形成第二种活性位, 从而显著提高了催化活性.