Reforming of CH4 with CO2 over Co/Mγ-Al oxide catalyst

A series of Co/Mg–Al oxide samples,CoMgAl-x(x=(Mg+Co)/Al molar ratio of 1–5),were prepared by the self-combustion method followed by H2reduction.The catalytic performance and stability of the samples were studied in dry reforming of CH4.XRD and H2-TPR characterization results showed that the reduced CoMgAl-x samples mainly consisted of solid solution and spinel phases with cobalt particles.The spinel phases contained Co3O4 and Con Mg1-n Al2O4(0≦n≦1)varying with the(Mg+Co)/Al ratio.The effect of (Mg+Co)/Al molar ratio on the catalytic behavior was investigated in detail and CoMgAl-3 exhibited the highest catalytic activity and stability among the catalysts studied.     

Characterization and reactivity of γ-Al_2O_3 supported Pd–Cu bimetallic nanocatalysts for the selective oxygenization of cyclopentene

In this work, Pd–Cu/γ-Al_2O_3 is prepared by the impregnation method and investigated for selective oxygenization of cyclopentene to cyclopentanone. A series of bimetallic Pd–Cu/γ-Al_2O_3 nanocatalysts were prepared and the structures characterized by XRD, XPS and TEM. We determined that the obtained Pd–Cu/γ-Al_2O_3(molar ratio Pd:Cu = 5:1) was an efficient catalyst for the oxygenization of cyclopentene to cyclopentanone with 95% selectivity and 85% conversion(100 °C, 1 MPa initial O_2 pressure, 7 h).     

CO2重整甲烷制合成气催化剂六铝酸盐LaNiy/Al12-yO19-δ的研究

A series of Ni modified hexaaluminates LaNi y Al 12- y O 19- δ ( y =0 3, 0 6, 0 9, 1 0) were prepared by decomposition of nitrates and calcination at high temperature. The crystalline structure and catalytic properties for CO 2 reforming of methane to synthesis gas were investigated by using XRD, XPS, TPR and TGA techniques. The results showed that a pure hexaaluminate LaNi y Al 12- y O 19- δ phase is formed only when y value is in 0< y ≤1. The reduced hexaaluminates LaNi y Al 12- y O 19- δ exhibit significant catalytic activity and stability for the reaction of CO 2 reforming of methane to synthesis gas at 780 ℃, and no deactivation resulting from carbon deposition is found. In the meantime, the catalytic activity is obviously affected by the modifier Ni in the hexaaluminate lattices. Under the same reaction conditions, the conversion of CH 4 and CO 2 increase with increase in the amount ( y value) of the modifier Ni.     

Methanation of carbon dioxide on Ni/ZrO2-Al2O3 catalysts:Effects of ZrO2 promoter and preparation method of novel ZrO2-Al2O3 carrier

The novel nickel-based catalysts with a nickel content of 12 wt% were prepared with the zirconia-alumina composite as the supports. The new carriers, ZrO2 improved alumina, were synthesized by three methods, i.e., impregnation-precipitation, co-precipitation, and impregnation method. The catalytic properties of these catalysts were investigated in the methanation of carbon dioxide, and the samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), temperature-programmed reduction (TPR) and temperature-programmed desorption (TPD) techniques. The new catalysts showed higher catalytic activity and better stability than Ni/γ-Al2O3. Furthermore, as a support for new nickel catalyst, the ZrO2-Al2O3 composite prepared by the impregnation-precipitation method was more efficient than the other supports in the methanation of carbon dioxide. The highly dispersed zirconium oxide on the surface of γ-Al2O3 inhibited the formation of nickel aluminate-like phase, which was responsible for the better dispersion of Ni species and easier reduction of NiO species, leading to the enhanced catalytic performance of corresponding catalyst.     

Doping Effect on the Grain Growth of Spinel LiMn2O4 Prepared by Sol-Gel Methods

The cathode-active materials, Li1+yMxMn2-xO4 (M = Al, Co, Ni, Zn, y = 0.02, x = 0.02) powder, were synthesized by sol-gel method using LiOH, Mn(NO3)2 as the starting materials, citric acid as a carrier and Al(NO3)3·9H2O or Co(NO3)2·6H2O or Ni(NO3)2·6H2O or Zn(NO3)2·6H2O as dopants. The influence of different doping elements on the structural properties of the as-prepared samples was investigated by X-ray diffraction (XRD), infrared (IR) spectroscopy and scanning electron microscopy (SEM). X-ray diffraction patterns of the prepared samples were identified as the spinel structure with space group Fd3m. The grain size increases gradually as the sintering temperature rises and corresponding activation energies for the grain growth have been estimated using Arrhenius’ empirical relation.     

Performance and characterization of iron-nickel catalysts for light olefin production

A series of x (Fe, Ni)/Al2O3 catalysts (x = 2--12 wt%) were prepared using incipient wetness method and studied for the conversion of synthesis gas to light olefins. 6 wt%(Fe, Ni)/Al2O3 catalyst was found to be the optimal catalyst for the production of C2--C4 olefins. The effects of calcination behaviors and operational conditions on the catalytic performance of the optimal catalyst were investigated. The best operational conditions were molar feed ratio H2/CO = 2/1, T = 260 ℃, gas hourly space velocity (GHSV) = 2600 h-1 and the pressure of 3 bar. Characterizations of both precursors and catalysts were carried out using X-ray diffraction (XRD), temperature-programmed reduction (TPR), scanning electron microscopy (SEM), N2-adsorption-desorption measurement, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC).     

Carbon dioxide catalytic conversion to nano carbon material on the iron–nickel catalysts using CVD-IP method

The over-consumption of fossil fuels resulted in the large quantity emission of carbon dioxide(CO2), which was the main reason for the climate change and more extreme weathers. Hence, it is extremely pressing to explore efficient and sustainable approaches for the carbon-neutral pathway of CO2 utilization and recycling. In our recent works with this context, we developed successfully a novel "chemical vapor deposition integrated process(CVD-IP)" technology to converting robustly CO2 into the value-added solid-form carbon materials.The monometallic Fe Ni0–Al2O3(FNi0) and bimetallic Fe Nix–Al2O3(FNi2, FNi4, FNi8 and FNi20) samples were synthesized and effective for this new approach. The catalyst labeled FNi8 gave the better performance, exhibited the single pass solid carbon yield of 30%. These results illustrated alternative promising cases for the CO2 capture utilization storage(CCUS), by means of the CO2 catalytic conversion into the solid-form nano carbon materials.     

Hydrogen evolution-assisted one-pot aqueous synthesis of hierarchical trimetallic PdNiRu nanochains for hydrazine oxidation reaction

A hydrogen evolution-assisted one-pot aqueous approach was developed for facile synthesis of trimetallic Pd Ni Ru alloy nanochain-like networks(Pd Ni Ru NCNs) by only using KBH_4 as the reductant, without any specific additive(e.g. surfactant, polymer, template or seed). The products were mainly investigated by transmission electron microscopy(TEM), X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS). The hierarchical architectures were formed by the oriented assembly growth and the diffusioncontrolled deposition in the presence of many in-situ generated hydrogen bubbles. The architectures had the largest electrochemically active surface area(ECSA) of 84.32 m~2 g~(–1) Pdthan Pd Ni nanoparticles(NPs,65.23 m~2 g~(–1) Pd), Pd Ru NPs(23.12 m~2 g~(–1) Pd), Ni Ru NPs(nearly zero), and commercial Pd black(6.01 m~2 g~(–1) Pd), outperforming the referenced catalysts regarding the catalytic characters for hydrazine oxygen reaction(HOR). The synthetic route provides new insight into the preparation of other trimetallic nanocatalysts in fuel cells.     

Catalytic activity and crystal structure modification of Pd/γ-Al_2O_3–TiO_2 catalysts with different Al_2O_3 contents

Pd/γ-Al_2O_3–TiO_2 catalysts containing various compositions of titania and alumina were prepared by sol–gel and wet-impregnation methods in attempt to study the particle size, nature of phases, morphology and structure of the composite samples. The ethanol oxidation experiments, N_2 adsorption–desorption,FTIR, XRD and XPS were conducted, and the effects of Al_2O_3 content on the surface area, phase transformation and structural properties of TiO_2 were investigated. The optimal value of ethanol conversion appeared on Pd/Al(0.05)–Ti and Pd/Al(0.90)–Ti catalysts irrespective of the ethanol oxidation temperature, and we call this as a double peaks phenomenon of catalytic activity. The XRD results reveal that the phase composition and crystallite size of the mixed oxides depend on Al_2O_3/TiO_2 ratio and calcination temperature. Al_2O_3 can effectively prevent the agglomeration of TiO_2 and this can be ascribed to the formation of Al–O–Ti chemical bonds in Al_2O_3–TiO_2 crystals. Binding energy and Pd surface concentration of the catalysts were modified apparently, which may also lead to catalyst activity changes.     

Coking-resistant Ni-ZrO2/Al2O3 catalyst for CO methanation

Highly coke-resisting Zr O2-decorated Ni/Al2O3 catalysts for CO methanation were prepared by a two-step process. The support was first loaded with Ni O by impregnating method and then modified with Zr O2 by deposition-precipitation method(IM-DP). Nitrogen adsorptiondesorption, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, H2 temperatureprogrammed reduction and desorption, NH3temperature-programmed desorption, and zeta potential analysis were employed to characterize the samples. The results revealed that, compared with the catalysts with the same composition prepared by co-impregnation(CI) and sequential impregnation(SI) methods, the Ni/Al2O3 catalyst prepared by IM-DP showed much enhanced catalytic performance for syngas methanation under the condition of atmospheric pressure and a high weight hourly space velocity of 120000 m L g-1 h-1. In a 80 h life time test under the condition of 300–600°C and 3.0 MPa, this catalyst showed high stability and resistance to coking, and the amount of deposited carbon was only 0.4 wt%. On the contrary, the deposited carbon over the catalyst without Zr O2 reached 1.5 wt% after a 60 h life time test. The improved catalytic performance was attributed to the selective deposition of Zr O2 nanoparticles on the surface of Ni O rather than Al2O3, which could be well controlled via changing the electrostatic interaction in the DP procedure. This unique structure could enhance the dissociation of CO2 and generate surface oxygen intermediates, thus preventing carbon deposition on the Ni particles in syngas methanation.     

2-乙基蒽醌在双金属整体式催化剂上的氢化反应: 实验和DFT研究

过氧化氢(H2O2)是一种绿色化工原料和环境友好氧化剂. 目前, 超过 98% 的H2O2是通过蒽醌法生产. 蒽醌法主要包括 2-乙基蒽醌氢化生成 2-乙基氢蒽醌和 2-乙基氢蒽醌氧化生成 2-乙基蒽醌和H2O2的过程. 其中, 2-乙基蒽醌氢化是关键步骤. 在氢化过程中, 生成的 2-乙基氢蒽醌和四氢-2-乙基氢蒽醌是目标产物, 同时生成许多副产物. 目前, Pd 颗粒催化剂是广泛使用的催化剂, 但是蒽醌氢化过程中, 质量传递是主要的控制因素. 与颗粒催化剂对比, 整体式催化剂可以减弱整个反应的内外扩散, 提高反应速率. 很多研究结果显示, 整体式催化剂的传质优于颗粒催化剂, 可以提高催化效率. 近期许多研究显示, 双金属颗粒催化剂在很多氢化反应中体现出优异的催化性能. 本工作制备了双金属整体式催化剂, 考察了其在蒽醌氢化过程中的催化性能.首先, 通过浸渍法制备了4 种双金属整体式催化剂 Pd-M/SiO2/COR (M = Ni, Fe, Mn和 Cu)以及Pd/SiO2/COR和Ni/SiO2/COR两种单金属整体式催化剂. 催化活性结果显示, Ni/SiO2/COR的H2O2产量低于 Pd/SiO2/COR, 而且在 700 oC还原的 Pd-Ni/SiO2/COR 整体式催化剂在 Pd/M = 2 时取得了最高选择性 (95.3%) 和H2O2产量 (7.5 g/L). 然后, 考察了金属负载量的影响. 结果显示, 在金属负载量低于 0.4% 时, 随着金属负载量增加, 选择性和H2O2产量增加, 在金属负载量高于0.4% 时, 随着金属负载量增加, 选择性和H2O2产量降低. TEM结果表明, 添加第二种金属后, 双金属整体式催化剂颗粒尺寸变小, 分布更均匀. EDS结果显示, 双金属形成了合金. H2-TPR结果显示, 随着Pd/M比率增加, 还原温度降低, 说明Pd有助于第二种金属氧化物的还原. 这可能是由于 Pd 表面的氢溢流到第二种金属 (Ni, Fe, Mn和 Cu) 表面. 此外, 文献结果表明, 合金的形成能够抑制 PdH 的形成. 本工作表明添加第二种金属 (Ni, Fe, Mn和Cu) 后, PdH 的峰强度减弱或者峰消失, 也说明形成了合金. XPS 结果显示, 添加第二种金属后,在 336.3 ± 0.1 和 341.4 ± 0.1 eV 出现了新的 Pd 3d5/2和 Pd 3d3/2峰, 说明形成了合金. H2-O2滴定结果表明, Pd-Ni/SiO2/COR的Pd分散度和Pd比表面积都高于其他双金属催化剂, 说明第二种金属 Ni 更有利于促进 Pd 的分散, 减弱颗粒集聚, 揭示了Pd 和 Ni 之间强烈的相互作用. DFT 计算结果显示, Pd3M1(M = Ni, Fe, Mn和Cu) 双金属整体式催化剂和 2-乙基蒽醌之间的结合能低于 Pd/SiO2/COR和 2-乙基蒽醌之间的结合能, 但是 Pd3M1(M = Ni, Fe和Mn) 双金属催化剂和 2-乙基氢蒽醌之间的结合能减小得很少, 这可能是由于 2-乙基蒽醌的 C=O 和第二种金属之间具有强烈相互作用的缘故. Pd3Cu1双金属催化剂和 2-乙基氢蒽醌之间的结合能减小很多, 主要是由于 Pd3Cu1表面不利于 2-乙基氢蒽醌的吸附.因此, Pd-Ni/SiO2/COR 比 Pd/SiO2/COR, Ni/SiO2/COR 和其他的双金属整体式催化剂具有更高的选择性和H2O2产量, 主要是由于合金的形成以及 2-乙基氢蒽醌的 C=O 双键和 2-乙基氢蒽醌强烈的相互作用.     

CeO2和Pd在Ni/γ-Al2O3催化剂中的助剂作用

采用脉冲微反技术研究了添加n型半导体氧化物CeO2及贵金属Pd对Ni/γ Al2O3催化剂上CH4积炭/CO2消炭反应性能的影响,并运用BET、TPR、CO2 TPSR及氢吸附等技术对催化剂进行了表征.结果表明, n型半导体氧化物CeO2的添加可以降低Ni/γ Al2O3催化剂上CH4裂解积炭活性,提高CO2消炭活性,添加少量贵金属Pd可以进一步改变载体Al2O3、助剂CeO2和活性组分Ni之间的相互作用,从而改善Ni/γ Al2O3催化剂的抗积炭性能.通过Ni Ce Pd/γ Al2O3催化剂上CH4积炭/CO2消炭模型对上述作用机制作出了新的解释.     

Pd-Cu/γ-Al2O3催化苯乙炔选择性加氢反应

为了提高苯乙炔加氢反应中的苯乙烯选择性, 本文采用“胶体-等体积浸渍”两步法制备了Pd-Cu/γ-Al₂O₃双金属催化剂. 利用高分辨率透射电镜(HRTEM)、X射线光电子能谱(XPS)、CO脉冲化学吸附、N2物理吸附、电感耦合等离子体原子发射光谱(ICP-AES)等技术表征了Pd-Cu/γ-Al₂O₃的结构性质, 考察了Cu/Pd 摩尔比、Pd负载量以及金属引入顺序对Pd-Cu/γ-Al₂O₃催化苯乙炔选择性加氢性能的影响. 结果表明, 与Pd/γ-Al₂O₃单金属催化剂相比, Pd-Cu/γ-Al₂O₃的苯乙烯选择性大幅度提高, 尤其是当Pd负载量为0.3%(w), 且Cu/Pd摩尔比为0.6时, Pd-Cu/γ-Al₂O₃表现出优异的加氢选择性; 在0.1 MPa和40 ℃下, 当苯乙炔转化率为90%时, 双金属催化剂的苯乙烯选择性可达95%; 当转化率达到99%以上时, 苯乙烯选择性仍保持在82%左右. 分析表明, Pd-Cu/γ-Al₂O₃中形成了Pd-Cu合金, 但是两种金属间不存在电子转移, Cu对Pd的几何效应才是导致Pd-Cu/γ-Al₂O₃苯乙烯选择性增加的主要原因.     

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…     

金属离子修饰的Ru-Pt/γ-Al2O3催化p-CNB选择性加氢

催化还原法制备卤代苯胺因具有产品质量好、收率高和三废少等优点而日益受到重视．近年来,研究较多的是高分子化合物稳定的Pt,Pd,Ru单金属或双金属胶体催化剂以及负载型单金属或双金属催化剂．用第三金属组分修饰的胶体催化剂的催化性能更好,但反应后催化剂与产物分离     

Co3O4纳米片的制备及对H2O2电还原反应的催化性能简

通过恒电势电沉积和加热处理在泡沫镍基体上制备了Co3O4纳米片. 利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)和X射线光电子能谱(XPS)等手段对纳米片的形貌和结构进行了表征. 采用线性伏安扫描和计时电流技术研究了Co3O4纳米片电极对H2O2的电还原性能. 结果表明,在3.0 mol/L KOH 和 0.4 mol/L H2O2溶液中,当电压为-0.4 V(vs. Ag/AgCl)时,线性伏安扫描电流密度达到-0.386 A/cm2,在1000 s 测试时间内,计时电流密度衰减很小,表明Co3O4纳米片电极对H2O2具有很高的活性和稳定性.     

胶原纤维接枝多酚负载钯-镍双金属催化剂的制备及其催化硝基苯的加氢性能

 以胶原纤维 (CF) 接枝表棓儿茶素棓酸酯 (EGCG) 为载体, 制备了新型 Pd-Ni/CF-EGCG 催化剂. EGCG 作为“桥分子”对 Pd-Ni 纳米粒子起着分散和锚定作用. 通过热重分析、扫描电镜、透射电镜、X 射线光电子能谱和 X 射线衍射对该催化剂进行了表征. 结果表明, 该催化剂具有规整的纤维结构, 在纤维表面形成了高分散的平均粒径为 2.2 nm 的 Pd-Ni 合金颗粒. 液相硝基苯催化加氢反应结果表明, 当 Ni 和 Pd 摩尔比为 0.8 时, Pd-Ni/CF-EGCG 催化剂具有最佳的双金属协同作用, 在 308 K 和 1.0 MPa 氢压下, 加氢速率达 237 min?1, 比单金属的 Pd/CF-EGCG 快 1 倍, 重复使用 5 次后仍具有较高的催化活性.     

甲烷部分氧化制合成气Pt-Ni/Al~2O~3催化剂的研究

研究了Ni/Al~2O~3,Pt/Al~2O~3和一系列Pt-Ni/Al~2O~3催化剂对甲烷部分氧化制合成气的催化作用,发现Pt-Ni/Al~2O~3催化剂显示了比Ni/Al~2O~3和Pt/Al~2O~3更高的活性和稳定性。H~2-TPR,CO-TPD,CO~2-TPD,SEM,XPS和XRD等结果证明:Pt和Ni之间存在较强的相互作用,Pt和部分Ni形成固溶体合金并且Pt在催化剂表面富集。Pt和Ni之间的相互作用提高了催化剂的活性和稳定性,甲烷在Pt-Ni/Al~2O~3上的催化部分氧化具有不同于在Pt/Al~2O~3和Ni/Al~2O~3上的反应性能。