Co基费托合成催化剂研究进展

概述了co基费托合成催化剂的制备方法,介绍了Co盐种类、浸渍方法、浸渍溶液的pH值、Co盐溶剂、金属Co负载量和干燥温度等制备条件对Co基催化剂活性的影响,介绍了Co基催化剂的改性方法。并在此基础上对Co基催化剂今后的研究发展方向进行了展望。     

制备方法对Co-Pd/TiO2催化剂催化CH4-CO2梯阶转化的影响

以钴、钯为活性金属, 分别采用浸渍法和溶胶-凝胶法制备了Co-Pd/TiO₂催化剂, 考察了不同制备方法制备的Co-Pd/TiO₂催化剂对CH₄-CO₂梯阶转化直接合成C₂含氧化合物的影响。利用XRD、XPS和N₂-吸附-脱附对催化剂进行了表征。结果表明:两种方法制备的催化剂反应前与反应后表面织构都存在较大变化, 且催化剂中均存在CoTiO₃物种, 这是活性金属Co与载体TiO₂之间发生强相互作用, CO²⁺替代TiO₂晶格中的Ti⁴⁺的结果;CoO和金属Pd可能是该反应的活性中心;反应前与反应后溶胶-凝胶法制备的催化剂的表面Co含量均低于浸渍法制备的催化剂, 而表面Pd含量则均高于浸渍法制备的催化剂, 且溶胶-凝胶法制备的催化剂各种产物的生成速率均高于浸渍法制备的催化剂, 因此, 与浸渍法制备的催化剂相比, 溶胶-凝胶法制备的催化剂具有更好的催化活性。     

热活化提升Pd/C催化剂甲酸电氧化性能的研究

通过微波辅助多元醇方法以XC-72碳黑作为基体材料制备了Pd/C材料,对其进行惰性气氛下热活化处理,制备了热活化Pd/C催化剂,并对不同温度制备的Pd/C催化剂的电催化甲酸氧化反应的性能进行了探究。在电化学测试中,热活化后的Pd/C催化剂的电催化活性和长时间运行稳定性都得到了显著提升。此外,在对热活化温度优化后,发现当热活化温度达到500℃时,所制备的Pd/C-500℃催化剂的甲酸电氧化活性和稳定性达到最佳水平。分析认为,催化性能的提升来源于Pd纳米颗粒的结晶性的提高,以及更强的金属载体的相互作用。     

制备方法对钯碳催化剂表面性质及其加氢性能影响

采用浸渍法制备Pd/C催化剂,考察了浸渍方法、还原方法和条件对催化剂活性的影响,用XRD及XPS对催化剂进行表征,并用对苯二甲酸加氢精制体系进行活性评价,与工业上使用的进口Pd/C催化剂进行比较。结果表明:采用EDTA处理载体后,再分2次浸渍PdC l2溶液制备的0.5%Pd/C催化剂,表面Pd的摩尔分数可达8%以上,但对催化剂活性影响不显著;还原温度过高会使H2还原法制备出的催化剂中Pd晶粒变大,导致催化剂活性降低;采用甲酸钠还原和250℃下H2还原方法有利于提高催化剂活性。     

Co/Cu/γ-Al_2O_3催化剂制备及其性能

以钴盐为主催化剂,以铜盐为助催化剂,采用等体积浸渍法,以γ-Al_2O_3为载体,制备了Co/Cu/γ/-Al_2O_3催化剂,以对甲酚为原料对催化活性进行测试,并采用XRD、FT—IR、XPS和BET表征方法对催化剂的晶体结构、表面电子状态和比表面积进行表征,研究各种因素对催化活性的影响。结果表明,Co_3O_4为催化剂的活性组分,催化剂中活性组分未与载体发生强烈的相互作用,且其比表面积最大,有利于活性组分的分散。Co/Cu/γ-Al_2O_3催化剂最佳制备条件为:Co与Cu物质的量比为5:1,浸渍液质量浓度为6%,焙烧温度400℃,对羟基苯甲醛收率为41.5%。     

介孔USY沸石负载Pd催化剂对大分子芘的深度加氢性能研究

通过水蒸气脱铝的方法制备含有介孔结构的超稳Y沸石(USYM),同时采用四氯化硅蒸汽脱铝方法制备了缺乏介孔的超稳Y沸石(USYSI).采用等体积浸渍方法将金属Pd负载到载体USYM,USYSI和Al-MCM-41 上用于大分子芘的加氢反应.芘加氢反应活性在USYM负载的Pd催化剂上明显高于USYSI和Al-MCM-41负载的Pd催化剂.催化剂的表征结果表明,与 USYSI相比,引入到USYM沸石中的介孔结构有利于大分子芘的扩散;Al-MCM-41相比,USYM沸石具有强酸中心有利于负载Pd催化剂对芳烃分子加氢活性的提高.     

制备方法对钯碳催化剂表面性质及其加氢性能影响

钯碳催化剂是一种常用的加氢催化剂，广泛应用于羰基加氢、烯烃加氢、硝基和亚硝基加氢等领域。Pd／C催化剂的制备大多采用浸渍法，一般包括载体预处理，活性金属浸渍、干燥、还原等步骤，还原过程大多采用H2还原。     

浸渍法制备Pt-Sn/γ-Al_2O_3催化剂及其催化性能

采用等体积共浸渍法和分步浸渍法制备Pt-Sn/γ-Al_2O_3催化剂,并在固定床反应器上进行正丁烷脱氢实验研究。结果表明,与共浸渍法相比,分步浸渍法制备的催化剂表现出更高的催化活性。采用等体积浸渍法制备催化剂时,活性组分与载体之间会发生竞争吸附作用,这会影响活性金属组分在载体表面的分散度,进而影响催化剂活性。     

浸渍法制备Pt-Sn/γ-Al2O3催化剂及其催化性能

采用等体积共浸渍法和分步浸渍法制备Pt-Sn/γ-Al₂O₃催化剂,并在固定床反应器上进行正丁烷脱氢实验研究。结果表明,与共浸渍法相比,分步浸渍法制备的催化剂表现出更高的催化活性。采用等体积浸渍法制备催化剂时,活性组分与载体之间会发生竞争吸附作用,这会影响活性金属组分在载体表面的分散度,进而影响催化剂活性。     

烷基苯酚加氢用Pd/C催化剂性能研究

采用浸渍法制备不同助剂改性的Pd/C催化剂,并与未添加助剂的Pd/C催化剂对比,考察不同助剂对苯酚加氢制备环己酮用Pd/C催化剂性能影响。结果表明,助剂Zn对催化剂活性和选择性影响较小,助剂Mg、Fe、Co使烷基苯酚加氢用Pd/C催化剂活性和选择性均有所提升,且以CoCl2为Co源,质量含量为2.0%Co修饰的Pd/C催化剂效果较优,催化剂重复使用性能良好。     

The effect of plasma pre-treatment of carbon used as a Pt catalyst support for methanol electrooxidation

Vulcan XC-72 carbon black for use as a catalyst support was treated in three different plasma atmospheres, H₂, Ar and O₂. The results showed that the microstructure and surface functional groups were significantly changed after plasma treatment. Pt/C catalysts were prepared by chemical reduction of H₂PtCl₆ with HCHO and those with untreated and plasma treated carbon black supports were characterized and tested for methanol electrooxidation. TEM showed that the platinum nanoparticles on H₂ and Ar plasma treated carbon were uniform and well distributed. Those on untreated carbon were uniform in most regions but coalesced in others. On O₂ plasma treated carbon agglomeration of the platinum nanoparticles was significant. XRD showed that the catalysts were composed of face-centered cubic Pt nanoparticles and XPS showed that they were metallic with no oxides present. Cyclic voltammetry and chronoamperometry were used to study methanol electrooxidation on the Pt/C catalysts in a solution of 0.5 M H₂SO₄ + 0.5 M CH₃OH, and showed that the catalytic activity those using H₂ and Ar plasma treated carbon was higher than for the untreated one. Catalysts supported by O₂ plasma treated carbon showed no catalytic activity. The treatment atmosphere of carbon therefore had a large effect on the catalyst performance, with the H₂ plasma being the best.     

Effect of a carbon black surface treatment on the microwave properties of poly(ethylene terephthalate)/carbon black composites

A surface treatment was applied to carbon black to improve the electrical and microwave properties of poly(ethylene terephthalate) (PET)-based composites. Three different formamide solutions with 1, 2, and 3 wt % concentrations were prepared to modify the surface chemistry of carbon black. Microwave properties such as the absorption loss, return loss, insertion loss, and dielectric constant were measured in the frequency range of 8–12 GHz (X-band range). Composites containing formamide-treated carbon black exhibited enhancements in the electrical conductivity, electromagnetic interference (EMI) shielding effectiveness, and dielectric constant values when compared to composites with untreated carbon black. In addition, increases in the formamide solution concentration and carbon black content of composites resulted in an increase in the electrical conductivity, EMI shielding effectiveness, and dielectric constant values. The percolation threshold concentration of PET composites shifted from a 3 to 1.5 wt % carbon black composition with the surface treatment. The best EMI shielding effectiveness was around 27 dB, which was obtained with the composite containing 8 wt % carbon black treated with a 3 wt % formamide solution. Moreover, this composition gave the lowest electrical resistivity and the highest dielectric constant among the produced composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mixing of carbon black and polymer: Interaction and reinforcement

Interaction between carbon black and polymer starts during the mixing process; a primary agglomerate is formed, the composition of which is dependent upon the structure. The important carbon black properties are surface area, specific activity, structure (void, volume, anisometry), and porosity of the particles. On heat treatment of black at 3000°C., it loses its sites of high specific activity. Structure and specific activity determine incorporation time and further dispersion. During mixing, bound rubber is formed which is used as a measure of specific surface activity. In the final vulcanizate, the filler–polymer interaction is evident in reduced swelling in solvents (benzene, chloroform, cyclohexane,) etc. Below a certain critical degree of swelling, the percentage swelling is no longer dependent upon the amount of filler in the vulcanizate. Graphitized black vulcanizates exhibit in all solvents the same degree of swelling as the unfilled vulcanizate. This phenomenon is explained by the assumption of mobile adsorption of rubber chains on the carbon black surface. In untreated blacks the mobility on the surface is limited by sites of high energy of adsorption. In graphitized blacks such sites are no longer found, and swelling is unhindered by the presence of black. Reinforcement is explained by the more homegeneous distribution of tension between molecular chains due to slippage on the carbon surface.     

Conversion of natural gas to hydrogen and carbon black by plasma and application of plasma carbon black

In a microwave plasma-catalytic system, methane decomposition was carried out with 2.45 GHz microwave plasma and then the high conversion and yield of hydrogen and carbon black were obtained efficiently. It was found that hydrogen and carbon black were produced at the mole ratio of 2:1, and carbon black of around 30 nm was produced, which is comparable to classical furnace black. In a study of catalyst effect, Pt-loaded catalysts showed higher activities than a Pd catalyst for the conversion of methane by plasma-catalytic process. The productivity of carbon black increased with platinum loading up to 3 wt.%.     

用于降低卷烟烟气中CO含量的Pd-Cu/活性炭催化剂

用浸渍法制备用于降低卷烟烟气中CO含量的Pd-Cu/活性炭催化剂,考察该催化剂对模拟卷烟烟气[4.4%CO-4.2%H2O-19.2%O2-72.2%N2(体积分数)]中的CO常温催化氧化性能,研究催化剂活性组分及其负载量、催化剂栽体、原料气中CO浓度和气体空速对催化剂的CO常温氧化活性的影响.研究表明,生产成本较低的...     

Effects of ozone treatment of carbon support on Pt-Ru/C catalysts performance for direct methanol fuel cell

This research is aimed to increase the activity and utilization of Pt-Ru alloy catalysts and thus to lower the catalyst loading in anodes for methanol electrooxidation. The Pt-Ru/C catalysts were prepared by chemical reduction. The support of Vulcan XC-72 carbon black was pretreated by ozone at different temperatures for different times. The specific surface area of the samples was evaluated by the standard BET method. The surface concentrations of oxygen were determined by XPS. The results showed that the surface concentrations of oxygen on the carbon were first decreased and then increased with pretreating times, and the specific surface area of the carbon was decreased with pretreating times at the same temperature. The specific surface area was increased with increasing temperature, and the surface concentration of oxygen was first decreased and then increased with increasing temperature for the same pretreating time. Pt-Ru/C catalysts supported by untreated and O₃ treated carbon black were characterized and tested for methanol electrooxidation. X-ray diffraction (XRD) was used to characterize the influence of carbon treated with ozone on Pt-Ru/C catalysts. It was found that the catalysts were composed only of f.c.c. Pt-Ru alloy particles without metallic Ru or Ru oxide. Cyclic voltammetry (CV) and Tafel curves were used for methanol electrooxidation on Pt-Ru/C catalysts in a solution of 0.5 mol/L CH₃OH and 0.5 mol/L H₂SO₄, showing that the catalytic activity of Pt-Ru/C catalysts supported by ozone treated carbon was higher than that by the untreated one. The ozone treatment time and temperature, which affect the performance of Pt-Ru/C catalysts, were discussed. Electrochemical measurements showed that the catalysts supported by the carbon after ozone treatment for 6 min at 140 °C had the best performance.     

炭载体前处理对Pt-Ru/C催化剂性能影响

为研究水蒸气处理后热处理对炭黑表面特性的影响,提高DMFC阳极催化剂的催化活性,利用先水蒸气处理后热处理的Vnlcan XC-72炭黑为载体制备Pt-Ru/C催化剂,与水蒸气处理的和未经处理的炭载体制备Pt-Ru/C催化剂的性能进行比较.采用XPS和BET测试了处理后的炭粉表面的含氧浓度和比表面,结果表明：水蒸气处理后,炭载体比表面积增大,含氧浓度降低;水蒸气处理后热处理,炭载体比表面积进一步减小,含氧浓度增加.用XRD对催化剂的结构进行了表征,结果表明：水蒸气处理后热处理的炭黑为载体制备Pt-Ru/C催化剂结晶状态良好,催化剂颗粒较小.在0.5mol/L CH3OH和0.5mol/L H2SO4混合溶液中,利用玻炭电极测试了循环伏安曲线和阶跃电位曲线,结果表明：用先水蒸气处理后热处理的炭粉为载体制备的催化剂比仅水蒸气处理和未经处理的炭粉为载体制备的催化剂的活性最高.     

以KMnO4改性炭黑为载体的Pd-Ni催化剂的制备和性能

以不同浓度的KMnO4溶液预处理的炭黑为载体，通过沉淀共还原法合成了3种Pd1Ni1/ACx (x=3,5,7)催化剂，并将3种催化剂与商业Pd/C催化剂进行了性能对比。用XPS、ICP、XRD和TEM对催化剂了进行表征。结果表明：Pd1Ni1/AC5的Pd负载量（质量分数，下同）最大（3.66%），Pd晶粒的平均粒径最小（4.71 nm），且均匀地分布在KMnO4氧化处理后的碳载体上，活性位点较多；XRD显示，3种Pd1Ni1/ACx催化剂中的Ni均以无定形存在。在电化学性能测试中，3种催化剂均表现出比商业Pd/C更好的电化学稳定性和存活率；其中，Pd1Ni1/AC5电化学活性表面积达62.21 m2/gPd，且乙醇催化活性为1797.85 A/gPd。     

Effect of surface acid groups associated with amorphous and structured carbon on the catalytic hydrodechlorination of chlorobenzenes

BACKGROUND: Catalytic hydrodechlorination (HDC) is a progressive approach to treating chlorinated waste streams. While carbon is widely used as a catalyst support, the influence of carbon surface functionality on HDC performance has not been established. This work sets out to assess the impact of surface acid groups associated with activated carbon (AC), graphite and graphitic nanofibers (GNF) on Pd promoted gas phase HDC of chlorobenzene (CB) and 1,3‐dichlorobenzene (DCB). RESULTS: The acid groups were introduced by HNO₃ washing and the HDC reaction performed over bulk Pd and Pd physically mixed with each carbon. The carbon was subjected to a thermal treatment to remove the surface acidity. Characterization was by temperature programmed decomposition (TPD), temperature programmed hydrogen treatment (TPH), BET area, acid‐base titration, scanning and transmission electron microscopy. TPD, TPH and titration analyses served to establish the presence of surface oxygen groups after acid washing and facilitated an evaluation of the effectiveness of the thermal treatment to remove these groups. CONCLUSIONS: The surface acid groups inhibited HDC activity, a response most pronounced for Pd + AC, less so for Pd + graphite, while the effect was slight for Pd + GNF. HDC inhibition is attributed to chloroarene interaction with the surface functional (notably carboxylic) groups that impedes HDC. Fractional dechlorination of DCB was equivalent to or lower than CB HDC; there is some evidence of DCB interactions with heat treated graphite and GNF that served to raise HDC activity. Effective HDC over carbon based catalysts requires removal of surface acid groups. Copyright © 2008 Society of Chemical Industry     

Effect of carbon black structure on the effectiveness of carbon black thermal interface pastes

Thermal pastes are needed for improving thermal contacts. The structure of carbon black, as described by the DBP value, governs the effectiveness of the black as a thermally conductive solid component in a thermal paste, as shown for pastes with a polyol ester vehicle. Carbon black with a lower DBP value (i.e., a lower structure) is more effective, as shown by a higher value of the thermal contact conductance measured across copper surfaces of roughness 15 μm. This is because a carbon black with a lower structure gives a smaller bond-line thickness, which is preferably less than 3 μm. In addition, this is because a lower structure gives a lower viscosity for the paste, thereby promoting conformability. The carbon black volume fraction has an optimum value for attaining maximum thermal conductance. A lower structure results in a higher value of the optimum carbon black volume fraction, due to the viscosity effect. For the same type of carbon black, this optimum is higher when the paste is tested between rougher surfaces. By using Tokaiblack #3800 carbon black (with DBP value 60 ml/g and optimum carbon black content 15 vol.%), a thermal paste that is more effective than the previously reported paste with Vulcan XC72 carbon black (with DBP value 188 ml/g and optimum carbon black content 2.4 vol.%) has been attained.