Reinforced nickel catalysts for steam reforming of methane to synthesis gas

XRD, mercury porosimetry, low-temperature nitrogen adsorption and electron microscopy were used to study peculiarities of the formation of reinforced composite nickel catalysts. The catalysts were prepared by sintering powdered metallic nickel with a supported nickel catalyst (GIAP-3 or NIAP-18) applied to a reinforcing stainless steel gauze. It was found that a metal matrix, in the pores of which supported catalyst particles were distributed, was formed in the composite catalysts. The NIAP-18-based catalyst exceeded the GIAP-3-based catalyst in activity toward the methane steam reforming. The NIAP-18-based catalyst was as active as the Cr₂O₃-doped NIAP-18-based catalyst, but showed a worse coke-resistance. A chromium oxide additive increased the activity of the GIAP-3-based catalyst.     

Promotion of nickel catalysts for the steam reforming of methane

The influence of additives (Cu, Fe and Al₂O₃) on the textural and catalytic properties of nickel in steam reforming of methane is described. The effects of structural promoting by Al₂O₃ and of electronic promoting by copper are reported. The rate of steam reforming of methane was measured in a gradientless reactor at atmospheric pressure.

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(Cu, Fe Al₂O₃) . Al₂O₃ . .

     

Nickel catalysts based on porous nickel for methane steam reforming

The influence of synthesis conditions on the phase composition and texture of porous nickel supports as plates with a magnesium oxide underlayer were investigated by X-ray diffraction, low-temperature nitrogen absorption, and electron microscopy combined with X-ray microanalysis. Nickel catalysts supported on these plates were studied. Thermal treatment of Mg(NO₃)₂ in nitrogen yields a magnesium oxide underlayer with a small specific surface area (support I). The replacement of nitrogen with hydrogen leads to a larger surface area (support II). The formation of MgO is accompanied by the incorporation of Ni²⁺ cations from the oxide film into the underlayer. Upon subsequent reduction with hydrogen or under the action of the reaction medium, these cations form fine crystallites of nickel. The supports having an oxide underlayer show a higher activity in methane steam reforming than the initial metallic nickel. Nickel catalysts on supports I and II show similar activities. The activity of the catalysts was stable throughout 50-h-long tests; no carbon deposits were detected by TEM.     

负载Ni催化剂上低温甘油蒸汽重整制氢

采用等体积浸渍法制备了Al₂O₃、CeO₂、TiO₂及MgO负载Ni催化剂,考察了它们对甘油蒸汽重整制氢反应的催化性能。采用X射线衍射、N₂吸附、透射电镜及H₂程序升温还原等方法对催化剂进行了表征。结果表明,载体对Ni催化剂的活性有显著影响。在400 ℃下Ni/CeO₂的催化活性明显好于其他催化剂,活性次序为Ni/CeO₂> Ni/Al₂O₃ > Ni/TiO₂ ~ Ni/MgO。Ni/CeO₂也具有好的稳定性,反应20 h未见活性下降,甘油转化率70%,氢气收率69.2%。这与CeO₂的本性及其与活性组分的相互作用有关。Al₂O₃具有较大的比表面积与孔体积,有利于CO吸附及甲烷化反应的进行,使得Ni/Al₂O₃催化剂在较高温度下具有很高的甘油转化率85.7%,但H₂选择性较差。由于MgO载体与活性组分强的相互作用而生成NiMgO₂固溶体,导致Ni/MgO低温活性差。     

吸收增强式甲烷水蒸气重整制氢循环反应模拟

吸收增强式甲烷水蒸气重整制氢反应可以生成高浓度的H2和较低浓度的CO、CO2。研究建立了考虑钙基吸收剂活性下降对吸收增强式甲烷水蒸气重整制氢过程影响的多次循环反应模型,在实验数据验证的基础上,计算了三种吸收剂活性下降特性对吸收增强式重整制氢过程的影响。结果表明,对于石灰石吸收剂,产生高纯H2的时间随循环次数的增加而急剧下降;白云石循环反应活性提高,产生高纯H2的时间随循环次数的增加而缓慢下降;CaO/Ca12Al14O33的循环使用次数明显大于石灰石和白云石。     

Kinetic behaviour of commercial catalysts for methane reforming in ethanol steam reforming process

Ethanol steam reforming has been studied in a fluidized bed （in order to ensure bed isothermicity） on commercial catalysts for methane reforming. The results allow analyzing the effect of temperature （in 300-700℃ range）, and both metal and support nature on the reaction indices （ethanol conversion, yields and selectivities to H2 and byproducts （CO2, CO, CH4 and C2H4O））. Special attention has been paid to catalysts＇ stability by comparing the evolution of the reaction indices with time on stream at 500°C （minimum CO formation） and 700℃ （minimum deactivation by coke deposition）. Although they provide a slightly lower H2 yield, the results evidence a good behaviour of Ni based catalysts, indicating that they are an interesting alternative of more expensive Rh based ones.     

Selectivity of the steam reforming of methane over metallic catalysts

The activity and selectivity of the methane-steam reaction has been studied in a gradientless reactor at atmospheric pressure and 700–850 °C. Differences were found in the course of the reaction on Pd relative to other metals, viz. Ni, Pt and Ru, and an interpretation of the results is proposed.

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700–850°C. Pd , ., Ni, Pt Ru, .

     

Alumina as a nickel catalysts support for steam reforming of hydrocarbons

The coking resistance of six alumina supported nickel catalysts in n-butane steam reforming mainly depends on the average size of nickel crystallites. Thus, by using suitable preparative methods, it is possible to produce good, coking resistant nickel catalysts even with Al₂O₃ support.

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Al₂O₃ -, , . . ., , - Al₂O₃.

     

Novel method for comparative activity testing of catalysts for methane steam reforming

The method suggested permits to achieve considerable acceleration in comparative testing of the activity of catalysts for methane steam reforming and to extend the amount of information obtained as well as to improve its quality.

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, .

     

New data on gas-phase radical reactions in the steam reforming of methane in the presence of catalysts: I. Nickel catalysts

Methane pyrolysis and steam reforming were studied over a series of nickel catalysts (Ni-Al₂O₃, Ni/MgO, and Ni/LiAlO₂) under the same conditions (650-750°C, P_CH4 = 0.001-0.03 MPa). Unlike heterogeneous reaction of pyrolysis, some of the steps of steam reforming of methane occur in the gas phase. When gasphase reactions were suppressed, the rate and activation energy of steam reforming are close to the corresponding kinetic characteristics for pyrolysis. Hypothetically, the rate-limiting step of the process is the dissociative adsorption of methane on nickel in this case.     

Ni-Fe/蒙脱土催化剂催化乙醇水蒸气重整制氢的研究

采用浸渍法制备了一系列Ni-Fe/蒙脱土(MMT)催化剂,并应用于乙醇水蒸气重整制氢反应(ESR)。采用X射线衍射(XRD)、N_2吸附脱附分析和H_2-程序升温还原(H_2-TPR)表征手段对催化剂的物理化学性质、还原性能、碳沉积等进行了研究。结果表明,Ni-Fe/MMT催化剂中,Ni、Fe高度分散在载体MMT层间及表面,而且Fe的加入降低了Ni颗粒的粒径,增强了Ni~(2+)与载体的相互作用力。以10Ni5Fe/MMT为催化剂,在反应温度为500℃、水醇比为3∶1、空速为12 h~(-1),反应进行30 h后,乙醇转化率为100%,氢气选择性仍保持72%,副产物CO和CH_4含量明显降低。这是因为催化助剂Fe的引入,一方面,提高了Ni的分散度,使得ESR低温活性较好;另一方面,减小了Ni颗粒粒径,小颗粒的Ni有利于抑制甲烷的生成,并且Fe的加入加强了甲烷重整和水煤气变换反应,提高产物中氢气的选择性。     

Improved catalytic performance of Ni catalysts for steam methane reforming in a micro-channel reactor

Milliseconds process to produce hydrogen by steam methane reforming （SMR） reaction, based on Ni catalyst rather than noble catalyst such as Pd, Rh or Ru, in micro-channel reactors has been paid more and more attentions in recent years. This work aimed to further improve the catalytic performance of nickel-based catalyst by the introduction of additives, i.e., MgO and FeO, prepared by impregnation method on the micro-channels made of metal-ceramic complex substrate. The prepared catalysts were tested in the same micro-channel reactor by switching the catalyst plates. The results showed that among the tested catalysts Ni-Mg catalyst had the highest activity, especially under harsh conditions, i.e., at high space velocity and/or low reaction temperature. Moreover, the catalyst activity and selectivity were stable during the 12 h on stream test even when the ratio of steam to carbon （SIC） was as low as 1.0. The addition of MgO promoted the active Ni species to have a good dispersion on the substrate, leading to a better catalytic performance for SMR reaction.     

Syngas production from methane steam reforming and dry reforming reactions over sintering-resistant Ni@SiO2 catalyst

Research on Chemical Intermediates - Syngas is a very important intermediate in chemical industry for energy chemicals production through F–T synthesis. Methane steam reforming (MSR) and dry...     

Effect of the support on the coking of nickel catalysts in hydrocarbon steam reforming

Experiments on the coking rates of variously prepared nickel catalysts on TiO₂, Al₂O₃ and MgO in n-butane steam reforming show that changes in the relative coking rate at a rising steam excess in the gas phase depend mainly on the kind of support. The results obtained are accounted for by changes in the electron density at the site of nickel crystallite contact with the surface of various supports.

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, TiO₂, Al₂O₃ MgO, - , , , , , . .

     

负载Ni催化剂用于乙二醇蒸汽重整制氢催化性能研究

采用等体积浸渍法和共沉淀法制备了Ni催化剂,在固定床反应器上考察了Ni负载量、焙烧温度、反应温度等因素对乙二醇低温重整制氢反应活性和选择性的影响。应用X射线衍射、氮物理吸附、H₂程序升温还原等技术对负载型Ni催化剂进行了表征。结果表明,共沉淀法制备的Ni/CeO₂催化剂具有较小的NiO颗粒与CeO₂载体颗粒粒径,催化活性较高。添加少量氧化钴到Ni/CeO₂催化剂中可使H₂收率达72.6%,EG转化率达93.1%。在CeO₂中添加Al₂O₃能提高负载Ni催化剂的活性,乙二醇转化率达94.0%,H₂收率达67.0%;但添加SiO₂则使其活性明显变差。     

镍负载量对乙醇水蒸气重整制氢催化性能和催化剂的影响

采用稳态实验对镍负载量对Ni/MgO催化剂在乙醇水蒸气重整反应的影响进行了研究。结果表明,在101.3kPa下,镍负载量越高,催化剂的活性越高。对于催化剂的选择性,存在一个最佳镍负载量为10%Ni/MgO。按选择性从大到小排序,不同镍负载量的催化剂为：10Ni/MgO>15Ni/MgO>12.5Ni/MgO>7.5Ni/MgO≈5Ni/MgO。热分析表明,焙烧过程中不同镍负载量的催化剂镍前体与载体前体之间发生的相互作用不同。XRD和TPR 表征结果显示,催化剂的晶体结构和还原特性也与催化剂上镍的负载量有关。焙烧过程中样品10Ni/MgO上镍前体与载体前体发生了两种相互作用, 并且其氧化态与其他催化剂相比具有特殊的结构和还原性。说明催化剂的选择性不仅受活性相Ni的影响而且受Ni活性相周围环境的影响。     

Superior reactivity of skeletal Ni-based catalysts for low-temperature steam reforming to produce CO-free hydrogen

This paper describes the utilization of skeletal Ni-based catalysts for steam reforming of ethanol to produce CO-free hydrogen, which could be superior in the application of fuel cells. Assistant metals play different roles in the reaction; Pt and Cu suppress the methanation and enhance H(2) production, while Co promotes the methanation.     

Hydrogen production via steam reforming of bio-oil model compounds over supported nickel catalysts

The steam reforming of four bio-oil model compounds(acetic acid,ethanol,acetone and phenol) was investigated over Ni-based catalysts supported on Al2O3 modified by Mg,Ce or Co in this paper.The activation process can improve the catalytic activity with the change of high-valence Ni(Ni2O3,NiO) to low-valence Ni(Ni,NiO).Among these catalysts after activation,the Ce-Ni/Co catalyst showed the best catalytic activity for the steam reforming of all the four model compounds.After long-term experiment at 700°C and the S/C ratio of 9,the Ce-Ni/Co catalyst still maintained excellent stability for the steam reforming of the simulated bio-oil(mixed by the four compounds with the equal masses).With CaO calcinated from calcium acetate as CO2 sorbent,the catalytic steam reforming experiment combined with continuous in situ CO2 adsorption was performed.With the comparison of the case without the adding of CO2 sorbent,the hydrogen concentration was dramatically improved from 74.8% to 92.3%,with the CO2 concentration obviously decreased from 19.90% to 1.88%.     

Yttria promoted metallic nickel catalysts for the partial oxidation of methane to synthesis gas

A metallic Ni catalyst was prepared with nickel sponge, followed by acid treatment. It was further promoted with yttria by an impregnation method. The catalysts were characterized by SEM, BET, XRD, TPR, XPS, etc., and studied in the partial oxidation of methane to syngas. The characterization results showed that the yttria promoted metallic Ni catalysts had high specific surface area and more NiO. The reaction results showed that the yttria promoter increased the CH4 conversion and the selectivity for H2 and CO.