吸附相反应技术制备双金属 Ag-Ni 催化剂用于硝基苯液相加氢

 浙江大学化学工程与生物工程学系, 浙江杭州 310027 摘要：采用吸附相技术在乙醇-水体系中分别制备了硅胶和高岭土负载的 Ag-Ni 双金属催化剂, 并用于硝基苯低温液相加氢制苯胺反应. 考察了催化剂中 Ni 含量和 Ni/Ag 比对催化剂形貌和活性的影响. 结果表明, 高岭土或硅胶负载的催化剂在 Ni/Ag = 5 (摩尔比) 时活性较高, 且都存在一个最佳 Ni 含量, 分别为 0.04% 和 0.03%. 在相同条件下, 以高岭土负载的 Ag-Ni 催化剂的活性和苯胺收率更高.     

Surface properties of Ni-Pt/SiO2 catalysts for N2O decomposition and reduction by H2

The surface properties of bimetallic Ni-Pt/SiO2 catalysts with variable Ni/Ni + Pt atomic ratio (0.75, 0.50, and 0.25) were studied using N2O decomposition and N2O reduction by hydrogen reactions as probes. Catalysts were prepared by incipient wetness impregnation of the silica support with aqueous solutions of the metal precursors to a total metal loading of 2 wt %. For both model reactions, Pt/SiO2 catalyst was substantially more active than Ni/SiO2 catalyst. Mean particle size by TEM was about the same (in the range 6-8 nm) for all catalysts and truly bimetallic particles (more than 95%) were evidenced by EDS in the Ni-Pt/SiO2 catalysts. CO adsorption on the bimetallic catalysts showed differences in the linear CO absorption band as a function of the Ni/Pt atomic ratio. Bimetallic Ni-Pt/SiO2 catalysts showed, for the N2O decomposition, a catalytic behavior that points out an ensemble-size sensitive behavior for Ni-rich compositions. For the N2O + H2 reaction, the bimetallic catalysts were very active at low temperature. The following activity order at 300 K was observed: Ni75Pt25 > Ni25Pt75 approximately Ni50Pt50 > Pt. TOF values for these catalysts increased 2-5 times compared to the most active reference catalyst (Pt/SiO2). The enhancement of the activity in the Ni75Pt25 bimetallic catalysts is explained in terms of the presence of mixed Ni-Pt ensembles.     

金属含量对Ni-Pd/H-Y上正癸烷加氢异构化反应活性和产物选择性的影响

在Y分子筛上浸渍0.1 wt% Pd和0.1–0.5 wt% Ni,用X射线衍射表征了该催化剂的结晶度,用透射电镜测得平均金属粒径.催化剂中Pd和Ni的化学态用X射线光电子能谱测定,其酸性则用氨-程序升温脱附进行了表征,发现一些酸位被Ni2+离子交换.采用程序升温还原表征了HY分子筛负载的Pd, Ni和Pd-Ni催化剂的还原性能.正癸烷加氢异构化反应在200–450 oC和1 atm条件下进行.结果发现,当0.1 wt% Pd/HY中Ni添加量增至0.3 wt%时,正癸烷转化率和异构化选择性增加.单支链和双支链异构体选择性的增加表明该反应遵循质子化环丙烷中间体机理. Ni添加量超过阈值导致活性和异构化选择性急剧下降.综上可见,双金属催化剂更有利于选择性生成双支链异构体,其辛烷值更高.     

聚合物固载Ni－Ag双金属催化剂Ⅱ．催化剂的催化性质

聚合物固载Ｎｉ┐Ａｇ双金属催化剂Ⅱ．催化剂的催化性质吴世华朱常英王连邦张松桢（南开大学化学系，天津３０００７１）关键词镍，银，聚合物固载金属催化剂，加氢，燃料电池电极溶剂化金属原子浸渍（ＳＭＡＩ）技术是制备聚合物负载零价金属催化剂的一个非常有用的方法...     

聚合物固载Ni-Ag双金属催化剂Ⅲ.聚合物比表面积对催化剂分散度和活性的影响

聚合物固载ＮｉＡｇ双金属催化剂Ⅲ．聚合物比表面积对催化剂分散度和活性的影响吴世华朱常英黄唯平沈虎峻沈欣李连荣（南开大学化学系，天津３０００７１）关键词镍，银，双金属催化剂，树脂，比表面积，固载型催化剂，加氢，燃料电池电极溶剂化金属原子浸渍（ＳＭＡ...     

负载型双金属催化剂的制备及其等离子体催化氨分解制氢性能

利用等体积浸渍法制备了Fe-Co、Fe-Ni、Mo-Co、Mo-Ni双金属催化剂(总金属含量均为10%(w,质量分数),双金属摩尔比均为1:1),考察了其在等离子体条件下氨分解活性,结果表明Fe-Ni双金属催化剂表现出较好的协同作用。在此基础上,进一步考察了Fe/Ni摩尔比对其活性的影响。结果表明:当Fe/Ni摩尔比为6/4时,氨分解活性最好,而且该双金属催化剂稳定性良好。采用N_2物理吸附、X射线衍射(XRD)、H_2-程序升温还原(H_2-TPR)和高分辨透射电子显微镜(HRTEM)对催化剂的物化性质、还原性能、微观形貌等进行了研究。结果表明:活性较好的Fe-Ni双金属催化剂中,Fe与Ni形成尖晶石结构NiFe_2O_4,该结构有利于Fe和Ni的还原,即活性组分易恢复金属态,这可能是其活性较高的原因。     

硅对铁基费-托合成催化剂的影响

用共沉淀法制备了一系列不同硅含量的铁基催化剂,采用N2吸附和原位X射线衍射对催化剂进行了表征,在固定床反应器中考察了催化剂的费-托合成反应活性、选择性和稳定性.结果表明,含硅的催化剂具有较大的比表面积和较小的平均孔径,在CO还原及费-托合成反应中生成的碳化铁物种的稳定性比不含硅的催化剂高.在费-托合成反应中,不含硅的催化剂具有较高的初始活性,但易失活;含硅的催化剂具有较低的初始活性,但稳定性较高.Fe7C3是活性最高的碳化铁物种.随着硅含量的增加,催化剂的费-托合成反应更易生成低碳数产物.     

Ethanol steam reforming on Ni/Al2O3 catalysts: effect of the addition of Zn and Pt

Ni-based catalysts supported on Zn-modified alumina were investigated in the ethanol steam reforming reaction. A commercial γ-alumina was impregnated with different amounts of zinc nitrate (0, 2, 5, 10, 15, 20 wt.% on Zn basis), calcined, and then impregnated with nickel nitrate aqueous solutions. The samples were characterized by a number of techniques: N(2) adsorption at 77 K, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray fluorescence (XRF), and temperature-programmed reduction (TPR). Their catalytic behavior in the ethanol steam reforming reaction was studied at 873 K, with a H(2)O/ethanol ratio of 5:1. Two effects of the presence of Zn were detected. On the one hand, zinc modifies the surface structure and the surface chemistry of the catalysts by formation of zinc aluminates, and on the other hand, zinc oxide can be reduced to metallic zinc under reaction conditions, thus modifying the catalytic properties of the active phase. The presence of Zn increases the ethanol conversion to gaseous compounds as compared with the catalyst supported on the Zn-free commercial alumina. The addition of a small amount of Pt (1 wt.%) causes a beneficial effect in the reaction. When Ni catalysts were used without a previous reduction treatment, ethylene was formed in high amounts; however, the Pt-Ni catalysts need no reduction pre-treatment to achieve high H(2) yields (close to 70%) and showed a high stability versus time on stream because of the control of the production of ethylene, a coke precursor.     

NiFe双金属催化剂用于月桂酸甲酯加氢的研究

负载型Ni Fe/γ-Al_2O_3双金属催化剂的物理化学性质明显受还原温度的影响,进而影响月桂酸甲酯的加氢活性和产物选择性。金属Ni活性中心主要促进脱羰/脱羧(DOC)反应,Fe的加入能促进月桂酸甲酯发生加氢脱氧反应,促进C_(12)烷烃化合物生成。H_2-TPR、XRD、H_2-TPD和BET结果表明,高的还原温度有利于金属或合金活性中心形成,NiFe双金属催化剂的加氢活性取决于金属Ni、Fe和NiFe合金的含量;NiFe双金属催化剂吸附与活化H_2分子的能力明显受还原温度的影响。在研究的温度范围内,Ni活性中心具有优异的加氢和裂解性能,Fe物种的引入能有效抑制裂解性能。双金属催化剂的加氢活性顺序:NF420NF360NF450NF300,在420℃下经H_2还原制得的NF420催化剂具有最佳的月桂酸甲酯加氢性能,在反应温度为380℃时,月桂酸甲酯加氢转化率和烷烃化合物选择性分别高达93.3%和90.0%。     

In对Ni/SiO2催化剂苯甲醚加氢脱氧性能的影响:苯环加氢及 C-C键氢解的抑制作用

由可再生木质素基生物质油加氢脱氧制三苯(苯、甲苯及二甲苯)及燃油可减少对化石能源依赖、缓解环境问题,加氢脱氧催化剂的研究开发为众多学者密切关注.我们以低成本金属Ni为加氢脱氧活性组分,采用金属In对金属Ni催化剂进行改性,旨在增加以苯甲醚为模型反应物加氢脱氧中的三苯收率、降低金属Ni的C-C键氢解及甲烷化活性,提高反应过程中碳收率、降低耗氢量.采用等体积浸渍-程序升温还原法制备了Ni/SiO2及Ni-In/SiO2催化剂,研究了Ni/In比及Ni含量对In改性Ni/SiO2催化剂结构和苯甲醚加氢脱氧性能的影响,利用H2-TPR,H2化学吸附,XRD,NH3-TPD,XPS,TEM及N2物理吸附-脱附等手段对催化剂及其前驱体进行了表征,采用石英管固定床反应器在300°C、常压、H2/苯甲醚摩尔比25及苯甲醚重时空速0.4 h-1的反应条件下考察了催化剂苯甲醚加氢脱氧性能,分析了催化剂结构与性能之间的关系.H2-TPR结果显示,金属In的加入抑制了催化剂前驱体中Ni物种的还原.XRD,H2化学吸附,HAADF-STEM-EDS及XPS等结果表明,经450°C还原制备的Ni-In/SiO2双金属催化剂中Ni和In接触紧密.In的加入明显降低了催化剂表面金属Ni的活性位数量;并且,Ni/In比越低Ni-In/SiO2催化剂H2化学吸附量越小.XPS结果还显示,Ni-In/SiO2催化剂中存在金属In向Ni转移电子.上述结果说明,在Ni-In/SiO2催化剂中金属Ni与In存在较强的相互作用.在苯甲醚加氢脱氧反应中,与Ni/SiO2催化剂相比,Ni-In/SiO2催化剂虽因表面Ni密度较低而具有较低苯甲醚转化率,但其苯环加氢、C-C键氢解及CO甲烷化活性较低,因而具有较高的三苯及环己烷选择性;并且,随Ni/In比的降低(即In含量的增加),Ni-In/SiO2催化剂的加氢、氢解及甲烷化能力呈减弱趋势.随Ni质量含量提高,Ni-In/SiO2双金属催化剂上苯甲醚转化率提高,但对三苯选择性及C-C键氢解能力影响不明显.经分析认为,与Ni/SiO2相比,Ni-In/SiO2催化剂较低的苯加氢及C-C键氢解活性与In对表面连续Ni位隔离作用及金属镍位电子云密度提高有关.在优化的反应条件下,Ni质量含量为40%、Ni/In比为40的Ni-In/SiO2催化剂上三苯收率为60.4%,高于相同Ni质量含量Ni/SiO2催化剂上三苯收率(51.6%).     

K改性Ni-Co-Al三元复合氧化物催化分解N2O

制备了(Ni+Co)/Al=3、Ni/Co=0.2(原子比)的NiCoAl三元类水滑石样品,焙烧获得NiCoAl复合氧化物,表面浸渍K₂CO₃溶液制备了K改性催化剂,用于N₂O分解反应,考察了K负载量、焙烧温度等制备参数和O₂、H₂O等反应气氛对催化剂活性的影响。用BET、XRD、H₂-TPR、XPS等技术表征了催化剂的组成结构。结果表明,K的表面改性提高了催化剂对N₂O分解反应的催化活性,其中,400℃预焙烧NiCoAl类水滑石制得复合氧化物,初湿浸渍K₂CO₃溶液,K的负载量为K/(Ni+Co)=0.05,400℃ 再焙烧制备的催化剂活性较高,有氧有水条件下500℃ 反应时N₂O可完全分解;在NiCoAl复合氧化物表面负载K₂CO₃组分,降低了催化剂表面Co、Ni元素的电子结合能,弱化了表面Co-O、Ni-O化学键,从而提高了催化剂活性和抗水性能。     

K改性NiAl类水滑石衍生复合氧化物催化分解N2O

制备了Ni/Al=4.1(原子比)的NiAl类水滑石,焙烧获得NiAl复合氧化物,浸渍K2CO3溶液制备了K改性NiAl复合氧化物催化剂,其中K/Ni=0.05~0.2(原子比),用于N2O催化分解反应.通过元素分析、XRD、BET、H2-TPR、XPS等技术表征了催化剂的组成结构,考察了NiAl类水滑石的预处理方式、...     

Formation of bimetallic Ag-Pd nanoclusters via the reaction between Ag nanoclusters and Pd2+ ions

We have investigated systematically the mechanistic aspects of the Ag-Pd bimetallic cluster formation within sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles by using in-situ X-ray absorption spectroscopy (XAS). A two-step sequential reduction method is employed for the synthesis of Ag-Pd bimetallic clusters. The first step involves preparation of Ag nanoclusters, by mixing the Ag+ ions containing the AOT microemulsion system with a reducing agent hydrazine (N2H4) containing the AOT microemulsion system. In the second step, the addition of Pd2+ ions to Ag nanoclusters led to the formation of Ag-Pd bimetallic clusters via the reaction between Ag nanoclusters and Pd2+ ions in AOT reverse micelles. The reduction of silver ions and the formation of corresponding Ag nanoclusters are monitored as a function of the dosage of the reducing agent, hydrazine. In-situ XAS allowed probing of the reaction between Ag nanoclusters and Pd2+ ions during the formation of Ag-Pd bimetallic clusters. Analysis of Ag and Pd K-edge XAS spectra reveals that in the final stage Ag-Pd clusters, in which "Ag" atoms prefer to be surrounded by "Pd" and "Pd" atoms prefer to be surrounded by "Pd", were formed. On the basis of XAS results presented here, we are able to propose a structural model for each step so that this work provides a detailed insight into the mechanism of nucleation and growth of Ag-Pd bimetallic clusters. We also discussed the atomic distribution of Ag and Pd atoms in Ag-Pd bimetallic clusters based on the calculated XAS structural parameters.     

Al2O3基Ni-Cu双金属催化剂上乙酰丙酸氢解（英）

Inexpensive γ-alumina-based nickel-copper bimetallic catalysts were studied for the hydrogenolysis of levulinic acid,a key platform molecule for biomass conversion to biofuels and other valued chemicals,into γ-valerolactone as a first step towards the production of 2-methyltetrahydrofurane.The activities of both monometallic and bimetallic catalysts were tested.Their textural and chemical characteristics were determined by nitrogen physisorption,elemental analysis,temperature-programmed ammonia desorption,and temperature-programmed reduction.The monometallic nickel catalyst showed high activity but the highest bγ-product production and significant amounts of carbon deposited on the catalyst surface.The copper monometallic catalyst showed the lowest activity but the lowest carbon deposition.The incorporation of the two metals generated a bimetallic catalyst that displayed a similar activity to that of the Ni monometallic catalyst and significantly low bγ-product and carbon contents,indicating the occurrence of important synergetic effects.The influence of the preparation method was also examined by studying impregnated- and sol-gel-derived bimetallic catalysts.A strong dependency on the preparation procedure and calcination temperature was observed.The highest activity per metal atom was achieved using the sol-gel-derived catalyst that was calcined at 450 ℃.High reaction rates were achieved;the total levulinic acid conversion was obtained in less than 2 h of reaction time,yielding up to 96%γ-valerolactone,at operating temperature and pressure of 250 ℃ and 6.5 MPa hydrogen,respectively.     

双金属NiCu/MgO催化剂上葡萄糖氢解制备高附加值C2-C4化学品

采用共沉淀法制备了不同 Ni ／Cu 比的 NiCu／MgO 双金属催化剂,并通过 N2物理吸附、X 射线衍射（XRD）、X 射线光电子能谱（XPS）和程序升温还原等方法对 NiCu／MgO 催化剂结构进行表征。表征结果表明,Cu 和 Ni 之间存在协同相互作用,NiMgO2的存在抑制了镍物种的还原和 Cu-Ni 合金的形成,催化剂的 Ni ／Cu 比和焙烧温度对其表面金属组成有非常重要的影响。以葡萄糖氢解反应为探针反应,考察了 Ni ／Cu 比、焙烧温度、H2压力、反应温度、反应时间等因素对 NiCu／MgO 催化性能的影响。研究表明相对于单金属催化剂,双金属催化剂对葡萄糖氢解生成 C2-C4和1,2-PD 具有较高的催化活性,这与铜镍之间的协同作用有关。     

Catalytic Influence of Bimetallic Bifunctional Ni-Pd/H-β and H-Mordenite Nanoporous Catalysts for Hydroisomerisation of <Emphasis Type="Italic">n</Emphasis>-Octane

Zeolite-β and mordenite were impregnated with 0.1 wt% Pd and varying the amount (0.1–0.5 wt%) of Ni. The prepared nanoporous catalyst were characterized by various physico-chemical techniques such as XRD, nitrogen adsorption–desorption isotherm (BET), NH₃-TPD and TPR, XPS and TEM. Hydroisomerisation of n-octane was carried out in the temperature range from 200 to 450 °C in the presence of flowing H₂ gas under 1 atm. Finally we found that Ni addition up to 0.3 and 0.2 wt% over 0.1 wt% Pd/H-β and H-mordenite enhances the n-octane conversion and isomerisation selectivity. As the Ni amount exceeds the threshold values, the conversion decreases with increase in cracked products, and also, the selectivity of mono and dibranched isomers were improved suggestion operation of PCP intermediate mechanism. The bimetallic catalysts were more selective to the formation of dibranched isomers with higher octane number, when compared with monometallic catalysts. Ni-Pd loaded zeolite-β supports always show higher activity and selectivity than mordenite supports. Moreover, we achieved higher conversion (74.9 %) and isomerisation selectivity (92.5 %) at low Ni loading (0.3 Ni wt% over 0.1 Pd wt%/Hβ) for the first time.     

甲醇羰基化制醋酸镍基双金属催化剂的研究

在ＮｉＣ催化剂中分别添加了九种不同的金属组分,在加压和碘甲烷助剂的存在下考察了第二金属组分及含量对甲醇羰基化反应性能的影响。结果表明：分别添加Ｐｄ、Ｍｏ、Ｌａ三种组分可不同程度地提高ＮｉＣ催化剂的羰基化活性,其中以Ｐｄ的效果最佳,Ｎｉ和Ｐｄ之间存在着明显的相互作用。Ｐｄ含量为１％时,羰基化活性达到最高,甲醇转化率和醋酸收率分别为９２４０％和４９７３％。Ｎｉ－ＰｄＣ双金属催化剂的活性中心主要为Ｎｉ０,还有少量Ｐｄ０存在,Ｐｄ能够显著促进ＮｉＯ的还原,这可能是氢溢流现象所致     

Versatile carbon supported mono and bimetallic nanocomposites: synthesis,characterization and their potential application for furfural reduction

Biomass conversion has been developed by testing various metal based carbon catalysts. Most of the reported catalysts either use very expensive metals or support that provides lower selectivity. In this context, we fabricated new carbon based nanocomposites and studied their catalytic application for furfural reduction – a promising biomass derived molecule. The mono (Cu, Co and Ni) and bimetallic (CuCo and CuNi) nanoparticle supported on commercial graphite (CG) were prepared and characterized by TEM, EDS, XRD and Raman spectroscopy. The analysis revealed that the nanocomposites are made up of metallic nanoparticles with average particle size of 5–13 nm on the graphite matrix. The obtained results indicated that the Cu+Ni@CG catalyst exhibited high catalytic activity for furfural reduction, thus leaving Cu+Ni as the finest and cost effective catalyst for this study.     

SiO2负载的Au-Ni双金属催化剂在乙炔选择加氢反应中的应用

负载型Au催化剂在乙炔选择加氢反应中表现出很高的乙烯选择性,但其转化率相对较低.通过添加第二种金属如Pd,Fe,Ag和Cu等,制备双金属催化剂是提高其在加氢反应中催化活性的一种非常有效的手段.其中Au-Pd双金属催化剂是最受关注的体系之一,Pd的加入可以非常显著地提高其催化乙炔选择加氢反应的活性.据文献报道,与Pd同一主族的Ni也具有较好的加氢活性.尽管与Pd相比,Ni很难与Au形成合金,但目前已有Au-Ni双金属催化剂在多种反应中表现出协同效应的报道,如水气变换、CO氧化以及芳香硝基化合物选择加氢等.因此,向Au催化剂中添加Ni也可能提高催化剂在乙炔选择加氢反应中的催化活性.因此,我们采用两步法制备了一系列SiO2负载的具有不同Ni:Au原子比的Au-Ni双金属催化剂,并将其用于乙炔选择加氢反应,发现Au-Ni双金属催化剂在该反应中表现出了显著的协同效应,其活性明显优于相应单金属催化剂的活性.尽管其乙烯选择性略低于单金属Au催化剂,但明显高于单金属Ni催化剂.通过调节还原温度和/或Ni:Au的比例,对催化剂的性能进行了优化.结果显示,当Ni:Au=0.5时,催化剂表现出最优的综合性能,即兼具较高的乙炔转化率和乙烯选择性.为了研究Au-Ni双金属催化剂中金属纳米粒子的结构、组成以及Au-Ni之间的相互作用,我们对催化剂进行了X射线衍射(XRD)、高分辨透射电镜(HRTEM)、能量散射谱(EDS)以及原位红外光谱(DRIFTS)表征.XRD和TEM结果显示,催化剂中的Au-Ni双金属纳米粒子都具有高分散和粒径均匀的特点.通过EDS分析,发现在Au-Ni双金属催化剂中的单个金属纳米粒子同时含有Au和Ni两种元素,尽管每个纳米粒子中Ni:Au的比例有差异.HRTEM结果发现,Au-Ni双金属纳米粒子的晶格间距介于Au(111)和Ni(111)的晶面间距之间,说明在Au-Ni双金属催化剂中有Au-Ni合金形成.原位DRIFTS结果显示,在Au-Ni双金属催化剂中,Au的存在促进了Ni的还原,说明Au与Ni之间存在紧密的相互作用.综上可见,Au和Ni在乙炔选择加氢反应中所表现出的协同效应主要归功于Au-Ni合金的形成,其中金属态Ni起主要的活性作用,而Au的存在则提高了催化剂的乙烯选择性.     

Ni-Fe催化剂乙醇部分氧化制氢的研究

研究了Ni Fe催化剂对乙醇部分氧化制氢反应,系统地考察了不同O2/C2H5OH摩尔比及反应温度下催化剂的性能.发现Ni Fe催化剂对乙醇部分氧化制氢具有较好的催化活性,其中组成为Ni50Fe50催化剂最好,最佳的反应条件是O2/C2H5OH=1.0,T=573 K.XRD谱图表明催化剂主要由尖晶石结构的铁酸盐和FeNi3合金相组成. XPS结果说明,催化剂体相以还原态FeNi3合金相为主,表面以氧化态的铁酸盐为主.稳定性考察的结果表明,催化剂经40 h反应后,对氢的选择性明显下降,此时对应的FeNi3物相衍射峰强度也明显降低,表明催化剂对H2选择性的下降与FeNi3物相的转变有关.