稀土掺杂改性对Cu/ZnAl水滑石衍生催化剂甲醇水蒸气重整制氢性能的影响

采用原位合成法在γ-Al₂O₃表面合成了锌铝水滑石,再通过顺次浸渍法制备了一系列掺杂稀土改性的M（M=Y、La、Ce、Sm、Gd）/Cu/ZnAl催化材料,并将其应用于甲醇水蒸气重整制氢反应。探讨了稀土掺杂改性对Cu/ZnAl催化剂催化性能的影响,并采用XRD、SEM-EDS、BET、H₂-TPR、XPS和N₂O滴定等手段对催化剂进行了表征。结果表明,催化剂的活性与Cu比表面积和催化剂的还原性质密切相关,Cu比表面积越大,还原温度越低,催化活性越高。稀土Ce、Sm、Gd的引入能改善活性组分Cu的分散度、Cu比表面积以及催化剂的还原性质,进而提高催化剂的催化活性。其中,Ce/Cu/ZnAl催化剂表现出最佳的催化活性,在反应温度为250 ℃时,甲醇转化率达到100%,CO含量为0.39%,相比Cu/ZnAl催化剂,甲醇转化率提高了近40%。     

Influence of copper precursors in the steam reforming of methanol over Cu/SnO2/SiO2 catalysts

Cu/SnO₂/SiO₂ catalysts, prepared with three different copper precursors (copper nitrate, sulfate and chloride), were characterized and investigated for the steam reforming of methanol. Cu/SnO₂/SiO₂ catalyst, prepared with copper nitrate, showed the highest activity among the tested catalysts. The highest activity of the catalyst prepared with copper nitrate was ascribed to the highly dispersed Cu particles from CO adsorption experiment. The selectivity of methanol to H₂ decreased with an increase in the amount of acid on the surface of Cu/SnO₂/SiO₂ catalysts from FT-IR experiments.This revised version was published online in December 2005 with corrections to the Cover Date.     

Influence of Ce substitution in LaMO3 (M = Co/Ni) perovskites for COx-free hydrogen production from ammonia decomposition

The La based perovskite type LaMO₃ (M = Ni, Co) oxides were prepared by combustion synthesis method using citric acid as organic fuel. These catalyst precursors tested for ammonia decomposition. The LaNiO₃ and LaCoO₃ catalysts showed good activity for NH₃ decomposition. The LaNiO₃ catalyst displayed greater activity than LaCoO₃. This due to high surface area and easily reducibility of Ni species. A 50% of La was substituted by Ce in both LaNiO₃ and LaCoO₃ catalysts. A remarkable effect on catalytic performance was observed with the partial substitution of La by Ce in perovskite catalyst especially at lower temperatures. The La_0.5Ce_0.5NiO₃ catalyst exhibited highest activity among all prepared samples. The achieved superior activity is due to boost in surface area, reducibility and suitable basicity. The SEM elemental mapping of La_0.5Ce_0.5NiO₃ catalyst concluded that metal oxide constituents dispersed homogeneously. The La_0.5Ce_0.5NiO₃ catalyst showed excellent stable catalytic performance during 50 h time on study at 550 °C.     

NiCu bimetallic catalysts derived from layered double hydroxides for hydroconversion of n-heptane

Supported Ni Cu bimetallic catalysts have been produced in-situ on commercial Al₂O₃ by using layered double hydroxides as precursors. The resulting catalysts show a uniform Ni and Cu distribution, thus providing good activity and selectivity in the reforming reaction of n-heptane. The catalytic performance has been found to depend on the Cu/Ni ratio, revealing the synergic catalysis between homogeneously dispersed Ni and Cu sites. The good catalysis of Ni Cu bimetallic cata...     

有氧气氛中碱金属改性CuAl复合氧化物催化分解N2O的活性

合成了Cu/Al原子比分别为2.0、3.1、4.1的CuAl类水滑石样品,焙烧得到CuAl复合氧化物。在Cu/Al原子比为3.1的CuAl氧化物表面浸渍碱金属盐溶液,制备改性CuAl复合氧化物,用AES、XRD、FT-IR、BET、H₂-TPR、XPS等技术对催化剂进行了结构表征,考察了CuAl复合氧化物组成、碱金属助剂类型和K的前驱物对改性催化剂在有氧气氛中催化分解N₂O活性的影响。结果表明,Na、K、Cs改性CuAl复合氧化物均提高了催化剂活性,但K助剂的增强效应最显著;钾的不同前驱物改性CuAl复合氧化物的催化活性有显著差异,加入碳酸钾、草酸钾提高了催化剂的活性,而加入醋酸钾、硝酸钾反而降低了催化剂活性。优化出的K改性CuAl复合氧化物催化剂在含氧含水气氛的N₂O分解反应中表现出了较高的活性。     

沉淀方法及铈掺杂对铜锰氧化物催化剂催化氧化CO性能的影响

The influence of Ce doping and the precipitation method on structural properties and the catalytic activity of copper manganese oxides for CO oxidation at ambient temperature have been investigated. The catalysts were characterized by means of the powder X-ray diffraction and N₂ adsorption-desorption, the inductively coupled plasma atomic emission spectrometry, the temperature programmed reduction, diffuse reflectance UV-Vis spectra, and the X-ray photoelectron spectroscopy. It was found that after doping little amount of Ce in copper manganese oxide, CeO₂ phase was highly dispersed and could prevent sintering and aggregating of the catalyst, the size of the catalytic material was decreased, the reducibility was enhanced, the specific surface area was increased and the formation of the active sites for the oxidation of CO was improved significantly. Therefore, the activity of the rare earth promoted catalyst was enhanced remarkably.     

Ce-Cu-Co/CNTs催化剂催化合成气制低碳醇及乙醇的研究

采用共浸渍法制备了不同Ce含量的Ce-Cu-Co/CNTs 催化剂, 考察了其在合成气制低碳醇反应中的催化性能, 借助X射线衍射(XRD)、程序升温还原(H₂-TPR)、N₂吸脱附实验(BET)、透射电镜(TEM)和CO程序升温脱附(CO-TPD)对这些催化剂进行了表征. 结果表明, 当Ce的质量分数为3%时, 低碳醇的时空收率和选择性达到最高, 分别为696.4 mg·g^-1·h^-1和59.7%, 其中乙醇占总醇的46.8%, 适量Ce的添加能提高Cu物种在催化剂上的分散度和催化剂的还原性能, 能显著地增加催化剂吸附CO的能力, 促进合成醇活性位的形成, 进而明显提高催化剂的活性和总醇的选择性. 研究表明, 将具有高活性和高碳链增长能力的CuCo基催化剂与碳纳米管的限域效应结合, 可实现缩窄产物分布、大幅度提高乙醇选择性的目的.     

Effect of copper precursors on the catalytic activity of Cu/ZSM-5 catalysts for selective catalytic reduction of NO by NH<Subscript>3</Subscript>

The Cu/ZSM-5 catalysts prepared by different copper precursors were used for the selective catalytic reduction (SCR) of NO _x with NH₃. The Cu/ZSM-5 catalyst prepared by the copper nitrate (Cu/ZSM-5-N) presented the best performance among the Cu/ZSM-5 catalysts and showed above 90 % NO _x conversion at 225–405 °C. The average particle size of CuO was 5.82, 9.20, and 11.01 nm over Cu/ZSM-5-N, Cu/ZSM-5-S (prepared by copper sulfate), and Cu/ZSM-5-C (prepared by copper chloride), respectively. The Cu/ZSM-5-N catalyst showed the highly dispersed copper species, the strong surface acidity, and the excellent redox ability compared with the Cu/ZSM-5-C and Cu/ZSM-5-S catalysts. The Cu⁺ and Cu²⁺ existed in the Cu/ZSM-5 catalysts and the abundant Cu⁺ over Cu/ZSM-5-N might be responsible for the superior SCR activity.     

改性SCR催化剂对Hg0催化氧化性能的研究

采用一系列金属氧化物对商用SCR催化剂进行掺杂改性,筛选出最优Ce掺杂SCR催化剂,模拟实际烟气组分,考察了Ce改性催化剂对烟气中Hg⁰氧化的影响。实验结果表明,Ce掺杂比例适当可显著提高其催化活性,Ce最佳负载量为9%时,Hg⁰的催化氧化效率比未掺杂SCR催化剂提高近40%,BET和XRD也显示,CeO₂在催化剂表面分散程度较好,未出现聚集现象。烟气工况对Hg⁰的催化氧化具有重要影响,其中,烟气组分HCl显著促进了Ce改性催化剂对Hg⁰的氧化,在一定温度范围内,Hg⁰的氧化效率随着温度升高而增加,在最佳空速、温度和烟气组分浓度时,Hg⁰的催化氧化效率可达95.11%。此外,掺杂CeO₂之后SCR催化剂的脱硝性能并未受到影响。     

Ce掺杂对碳纳米管负载Mn催化剂结构及SCR反应性能的影响

采用等体积浸渍法制备多壁碳纳米管(MWCNTs)负载Ce-Mn的催化剂,考察了Ce掺杂对Mn/MWCNTs催化剂上NH₃选择性催化还原(SCR)NO_x反应活性的影响.并运用透射电镜扫描、N₂吸附-脱附、程序升温还原、X射线光电子能谱、X射线衍射等手段,重点考察了Ce掺杂对Mn/MWCNTs催化剂结构性质的影响.结果表明,Ce掺杂能显著提高催化剂的SCR活性,其活性增量随着Ce含量的增加先增大后减小;当Ce/Mn为0.6时,催化剂活性最佳.表征结果显示,Mn/MWCNTs中添加Ce后,金属氧化物在MWCNTs上的分散程度提高;催化剂的比表面积和孔体积增大,平均孔径减小;氧化能力提高;表面氧含量增加,Mn化合价升高;结晶度降低,Mn主要以无定形或微晶形式存在,Ce主要以CeO₂物相存在.     

Highly Ordered Mesoporous Cobalt-Copper Composite Oxides for Preferential CO Oxidation

Highly ordered mesoporous cobalt-copper composite oxides were prepared by the nanocasting method with various Co and Cu ratios. The catalysts obtained were characterized by X-ray diffraction, N₂ adsorption–desorption, H₂-temperature programmed reduction, CO-temperature programmed desorption and X-ray photoelectron spectroscopy. All of the catalysts had uniform mesopores and high surface areas. The distinct catalytic properties of these well-characterized mesoporous materials were demonstrated for preferential CO oxidation. It is found that the mesoporous cobalt-copper composite oxides, exhibited the higher catalytic activity for CO conversion and selectivity compared with the mesoporous Co₃O₄ and mesoporous CuO. Among these catalysts the mesoporous cobalt-copper catalyst with Co:Cu molar ratio of 70:30, shows the best catalytic activity and the broadest operating temperature “window” for the high CO conversion in the range of 125–200^oC. The higher catalytic activity was attributed to the higher CO adsorption and oxygen vacancies.     

Effect of promoters on the catalytic performance of Ni/Al2O3 catalyst for partial oxidation of methane to syngas

The effect of promoters such as Ce, La and Ca on catalytic performance of Ni catalyst was measured in a continuous fixed bed reactor. The effect of promoters on Ni/a-Al₂O₃ catalyst is more significant than on Ni/g-Al₂O₃ catalyst. Ce was proved to be the best promoter among the three promoters tested and the optimum loading of Ce was 1%. The catalyst was characterized by TG, XPS, TPR and XRD techniques. TPR results showed that Ce can improve the reducibility of the Ni/Al₂O₃ catalyst. XRD results indicated that Ce was highly dispersed when its loading was low, but at higher loading it was crystallized into bulk CeO₂, thus, decreased the catalytic activity. This revised version was published online in June 2006 with corrections to the Cover Date.     

Ni/CeO2-SiO2催化剂的制备、表征及其甲烷部分氧化制合成气性能

以硝酸亚铈（Ce（NO₃）₃·6H₂O）和正硅酸四乙酯（C₈H₂₀O₄Si）为前驱体,采用溶胶-凝胶法合成了系列具有大比表面积的xCeO₂-（1-x）SiO₂（x = 0,0.25,0.50,0.75,1）复合氧化物载体,然后浸渍活性组分Ni制得用于甲烷部分氧化制合成气的Ni催化剂。运用N₂物理吸附-脱附、X射线粉末衍射、扫描电镜、紫外-可见漫反射光谱、氢程序升温还原、氨程序升温脱附和热重等手段对所得催化剂的组织结构、还原性、表面酸性和积炭行为等进行了表征;同时考察了催化剂的组成、焙烧温度和反应时间等对催化剂在甲烷部分氧化制合成气中催化性能的影响。表征结果表明,该系列Ni/CeO₂-SiO₂催化剂具有大比表面积,CeO₂晶粒较小,NiO的分散性好且易被还原,表面酸性弱,不容易积炭。当Ce/Si摩尔比为1：1,活性组分Ni的质量分数为10%,焙烧温度为700℃时,所制备的Ni/CeO₂-SiO₂催化剂表现出较好的稳定性、最高的CH₄转化率（~84%）和对产物CO及H₂的选择性（>87%）。     

Preparation and operating conditions for cobalt cerium oxide catalysts used in the conversion of synthesis gas into light olefins

Cobalt cerium oxides, prepared using a co-precipitation procedure, were studied as catalysts for the conversion of synthesis gas to light olefins (C₂-C₄). Specifically, we studied the effect of a range of preparation variables, including the molar ratio of the [Co]/[Ce] of the precipitation solution, ageing time and calcination temperature. In addition, the effects of supports and promoters on the catalysts’ activity and selectivity and a range of reaction temperatures using synthesis gas with different H₂/CO molar feed ratios were investigated. The catalyst containing a molar ratio of 80% Co and 20% Ce, aged for 2 h, supported with 15 wt% SiO₂ without any promoter, at an operating temperature of 450 °C and an H₂/CO feed ratio of 2/1 (GHSV = 4500 h^?1), performed optimally for the conversion of synthesis gas to light olefins. The characterization of both the precursors and the calcined catalysts by powder X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller specific surface area measurements and thermal analysis methods, including TGA and DSC, show that all the preparation variables influenced the catalyst precursor structure.     

合成方法对Rh/CeO2-ZrO2-La2O3催化剂的结构、表面性能及DeNOx活性的影响

用沉积沉淀法合成两种不同系列的CeO2-ZrO2-La2O3混合氧化物(ZrO2和La2O3沉积CeO2粒子(标记为A-x)以及CeO2和La2O3沉积ZrO2粒子(标记为B-x)),并用作Rh催化剂的载体。XRD、拉曼、TPR、XPS和O2脉冲等表征结果显示出不同的沉积顺序将导致不同的结构和氧化还原性能,且B-x具有更高的氧迁移性、储氧能力和表面Ce浓度。当其负载Rh后,Rh/B-x催化剂具有更高的NO和CO转化率及N2选择性,且Ce的最佳含量为50at%。这可能归因于Rh负载于富铈表面形成更多有利于NO分解的表面Ce3+活性位。     

Synthesis of Fe—Ni—Ce trimetallic catalyst nanoparticles via impregnation and co-precipitation and their application to dye degradation

In this study, trimetallic catalysts were prepared via the co-precipitation and impregnation methods. In order to investigate the effect of impregnation on the catalytic activity and crystallite size, a trimetallic catalyst, Fe—Ni—Ce, was prepared through the co-precipitation method in one set of experiments, and cerium was impregnated with the Ni—Fe mixture in the final stage of the preparation in another set. Fourier transform infrared spectroscopy was employed to confirm the formation of trimetallic catalysts and the success of the impregnation method. The Brunauer-Emmett-Teller nitrogen adsorption isotherm exhibits a high specific surface area (approximately 39 m² g^?1) for the nanoparticles obtained by the impregnation method. The crystallography and morphology of the trimetallic catalysts thus prepared were characterised by X-ray diffraction and scanning electron microscopy. UV-VIS spectroscopy and methylene blue dye degradation tests were also performed to investigate the catalytic activity of the synthesised catalysts. The crystalline size was found to be smaller for the catalysts prepared by the impregnation method. In addition, the samples synthesised using the cerium impregnation method showed superior activity in the methylene blue dye degradation test. The effect of the catalyst dosage on dye degradation, as well as the effect of the initial dye concentration on the catalyst activity, was also studied for both methods.     

Dehydrogenation activities of highly dispersed transition metal oxides on NaY zeolite

Highly dispersed α-Fe_2O_3/NaY,NiO/NaY,and CuO/NaY catalyst systems were pre-pared by impregnation method.Dispersion thresholds of the transition metal oxides on NaY" zeolitewere determined by XRD phase analysis.The dispersion capacities of the transition metal oxides on NaYzeolite are much lower than that estimated on the basis of a closed packed monolayer in the micropores.The catalytic activity and selectivity of the highly dispersed oxide catalyst systems for ethylben-zene and cyclohexane dehydrogenation reactions were reported.     

氧化铈气凝胶担载氧化铜催化剂上的一氧化碳氧化

 以一氧化碳氧化为探针反应,考察了氧化铈气凝胶担载氧化铜催化剂的催化活性,研究了催化剂中氧化铜的含量、载体及催化剂的焙烧温度对催化剂活性的影响．结果表明,氧化铈气凝胶担载的氧化铜催化剂对一氧化碳氧化反应呈现出高催化活性,适当温度下焙烧载体及催化剂有利于提高催化剂的催化活性;随着催化剂中氧化铜含量的增加,一氧化碳完全转化的温度降低,但当w（CuO）＞12％时,过量的氧化铜以体相形式而不是以高分散形式存在,对催化剂活性的影响很小．     

Ce改性的Pt/γ-AlO3催化剂用于富氢气氛下CO选择氧化

研究了Ce改性的Pt/γ-AlO3对于富氢气氛下CO选择氧化反应的催化行为考察了制备条件（共沉积沉淀法、分步沉积沉淀法以及沉积沉淀温度）对催化活性的影响．结果表明，在80℃时用共沉积沉淀方法制备的催化剂Pt/γ-AlO3-CP-80对CO氧化反应表现出良好的活性和选择性，CO转化率在120℃时可以达到85％．利用氢气程序升温还原和原位漫反射红外光谱对不同条件下制备的催化剂进行了表征，分析了Cc的促进作用．