Determination of resistance to coking in the steam reforming of hydrocarbons

For a long time the microbalance reactor has played an important role in catalyst deactivation studies, but it has a number of limitations. The initial temperatures of coking of Ni and Ni-Mo catalysts in the temperature-programmed reaction (TPReaction) of n-butane with steam are compared with the results of coking rates obtained by the traditional thermogravimetric method. The investigations show good agreement of the results.     

制备条件对用于甘油蒸汽重整反应Ni基催化剂性能的影响

研究了制备参数对用于甘油蒸汽重整反应的Ni基催化剂性能的影响。采用过量浸渍法、等体积浸渍法和改进的平衡沉积过滤(EDF)法制备了一系列Al2O3负载的8 wt%Ni催化剂,运用X射线衍射(XRD)、电感耦合等离子体光谱仪、N2吸附-脱附、扫描电镜(SEM)、透射电镜和H2程序升温还原(TPR)表征了催化剂的表面和体相性质;采用CHN分析仪和SEM表征了使用后催化剂以测定其表面沉积的碳及其形貌。结果表明,制备方法对所制催化剂的织构、结构和表面性质影响很大,导致氧化铝表面Ni物种的分散和种类的不同。即使XRD和TPR结果证实形成了铝酸镍晶相,但Ni/Al-edf催化剂中β峰的贡献大于其它两个催化剂的,表明在这种情况下铝酸镍更容易还原。在550 oC以上CO2选择性增加和CO选择性不变,表明Ni/Al-wet和Ni/Al-edf催化剂可成功催化水汽变换反应。另外,650oC时Ni/Al-edf催化剂上甘油生成气相产物的转化率、氢气产率以及烯丙醇、乙醛和乙酸选择性最高,且它在所有催化剂中的积炭量也最低。将催化剂结构性质、分散度和还原性与其催化性能相关联,发现EDF法制得的催化剂比表面积和活性相分散度更高,更易被还原,因而其活性和生成H2的选择性更高,也更抗积碳。     

镍基催化剂上稻草水蒸气重整制富氢合成气

采用浸渍法制备了SiO₂, γ-Al₂O₃, CaO和TiO₂负载的Ni催化剂, 以及不同MgO含量的MgO-7.5%Ni/γ-Al₂O₃催化剂,利用X射线衍射和N₂吸附-脱附技术表征了催化剂的结构,在固定床反应器上评价了它们在稻草水蒸气催化重整制合成气反应中的催化性能,考察了反应条件对催化剂性能的影响.结果表明, 以γ-Al₂O₃为载体时Ni催化剂活性最高,其中7.5%Ni/γ-Al₂O₃催化剂的H₂收率可达1071.3ml/g,H₂:CO的体积比为1.4:1;同时,MgO的添加进一步提高了该催化剂的性能,当MgO含量为1.0%时,H₂收率可达1194.6ml/g,H₂:CO体积比可达3.9:1.可见MgO的加入促进了Ni基催化剂上稻草水蒸气催化重整制合成气反应的进行,同时使得合成气中CO发生水-汽转换反应,从而大大提高了合成气中H₂含量.     

镍基催化剂上乙醇水蒸气重整反应的研究

考察了载体对Ni催化剂乙醇水蒸气重整制氢反应性能的影响。结果表明,Ni/CeO2催化剂具有较好的低温活性和氢气选择性。对Ni担载量和焙烧温度考察发现,400℃焙烧的15%NiCeO2催化剂具有较好的催化性能;继续升高焙烧温度引起NiO和CeO2粒子的显著增大,导致对氢气选择性的降低。较小的Ni和CeO2粒子有利于乙醇水汽重整反应的进行,而大的粒子倾向于乙醇的分解反应。 350℃时,在反应过程中分别添加CO、CO2和CH4的结果表明没有发生CO和CO2甲烷化反应,而发生了一定程度的CH4水汽重整反应。     

Ni-based catalysts obtained from perovskites oxides for ethanol steam reforming

Perovskites as host structures of cations were used in order to generate in situ active and stable catalysts for ethanol steam reforming. For this purpose, La_1-xMg_xAl_1-yNi_yO₃ (x = 0.1; y= 0, 0.1, 0.2, 0.3) perovskites were synthetized by the citrate method. Ni segregation is evident for a substitution level higher than 0.2. The segregation of Ni as NiO generated species interacts with different metal-support after the reduction step. The y= 0.1 catalyst presents the highest H₂ yield value about 85% during reaction time, with low mean values of CH₄ and CO selectivities of 3.4% and 11%, respectively and a low carbon formation. The better performance of y= 0.1 catalyst could be attributed to the minor proportion of segregated phases, thus a controlled expulsion of Ni is successfully reached.     

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.     

A review on butanol steam reforming for renewable hydrogen production

Butanol is a renewable bio-oxygenate that can be prepared by fermentation of lignocellulosic biomass. Steam reforming of bio-derived butanol is an attractive and feasible option for producing renewable hydrogen. In the present work, all the studies on butanol steam reforming are reviewed comprehensively. The thermodynamics for the reaction, the optimized reaction conditions such as temperature, pressure, steam to carbon (S/C) ratio and the innovations in catalyst designs are described in depth. Based on the type of catalyst and support, different reaction routes for butanol reforming are possible. Ni, Co, Rh and Pt catalyst are more appropriate for butanol reforming. The challenges associated in utilizing bio-butanol as feed and design of cost effective and coke resistant catalyst are discussed. Such discussions on butanol reforming are still missing and the present work will fill this gap.     

MgO纳米晶负载镍催化剂用于甲烷蒸汽重整反应(英文)

Nanocrystalline MgO with a relatively high surface area and mesoporous structure was synthesized by a surfactant assisted precipitation method for use as the support of nickel catalysts for steam reforming of methane. The samples were characterized by X‐ray diffraction, N2 adsorption, temperature‐programmed reduction, temperature‐programmed oxidation, scanning electron microscopy, and transmission electron microscopy. The catalysts showed high catalytic activity and good stability in the steam reforming of methane. Increasing the nickel loading up to 10 wt% gave increased activity. Catalysts with higher nickel loadings showed more deposited carbon after reaction. The excellent anti‐coking performance of the catalysts was attributed to the formation of a nickel‐magnesia solid solution, basicity of the support surface, and nickel‐support interaction.     

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。     

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。     

两种甲醇水蒸气重整制氢催化剂的研究

对采用共沉淀法制备的CuZnAlO类铜系催化剂和采用水滑石类层柱材料（LDHs）前驱体制备的催化剂在甲醇水蒸气重整制氢反应中的性能进行了研究。对共沉淀法制备的CuZnAlO类铜系催化剂考察了ZrO2助剂的加入对催化剂反应性能的影响，发现Zr的质量分数为10％的催化剂显著提高CuZnAlO催化剂的反应性能。该催化剂的最佳反应条件：0.1 MPa、250 ℃、H2O/MeOH摩尔比1.0～1.3、3.56 h－1。在此反应条件下进行了COPZr2催化剂150 h稳定性实验。结果表明，该催化剂具有很好的反应稳定性。甲醇转化率和氢产率分别约为88％和83％，产物湿基组成中H2和CO的质量分数分别为>63％和0.20％～0.31％。对LDHs前驱体制备的催化剂，进行了70 h反应稳定性实验，结果表明，催化剂虽具有较高的起始活性，但随反应进行，活性有所下降，30?h后基本保持稳定，甲醇转化率和产氢率分别为73％和66％，产物湿基组成中H2和CO的质量分数分别为>55％和0.07%～0.08%。该类催化剂的反应稳定性虽较差，但却可以显著降低产物湿基组成中CO的摩尔分数。对LDHs前驱体制备的催化剂进行XRD和SEM表征结果表明，ZrO2的加入使催化剂中CuO晶粒分散更为均匀，颗粒更细。     

湿混法制备甲醇氧化重整制氢CuZnAlZr催化剂

用简易湿混法制备了用于甲醇氧化重整制氢的CuZnAlZr催化剂,与共沉淀法制备的催化剂比较,结果表明,湿混法制备的催化剂具有相当的中高温活性和略低的低温活性,有较高的CO2选择性。XRD、TPR、TG-DSC等表征结果显示,湿混法制备的催化剂中铜组分易于向表面迁移和富集,并可能与氧化铝作用生成铜铝复合氧化物,具有了更高的Cu分散度和Cu0比表面浓度。湿混法制备的催化剂对甲醇氧化重整反应有较好的稳定性,经100 h的连续反应,在275 ℃时甲醇转化率在90％以上,重整气中氢气体积分数大于60％,CO2选择性接近99％。     

中温镍水蒸汽转化催化剂积碳动力学与机理研究

研究了833-948K和常压下, C7H16在镍催化剂上进行水蒸汽转化过程中的积碳反应动力学, 获得了相应的动力学方程。并探讨了相应的反应机理, 提出在镍表面同时进行的水蒸汽转化和积碳反应是两个相对独立的反应。指出在较高温度下, 水蒸汽会从简单非解离吸附转变为解离吸附, 这一变化不仅改变了反应级数, 更重要的是它提高了水蒸汽参与表面反应的能力, 特别是加强了氢对积碳反应的作用; 同时庚烷的吸附热也随之产生相当大变化。分析了出现在本温度区内积碳反应负表观活化能的来源。     

Kinetics of methane steam reforming on a Ni on alumina-titania catalyst

The kinetics of methane steam reforming on a nickel on alumina-titania catalyst, was studied in the range of 773–873 K. A Hougen-Watson type model gives good agreement with the experimental rates.     

Evaluation of naphtha reforming catalysts by accelerated deactivation tests

Accelerated deactivation tests of four commercial Pt−Re/Al₂O₃ catalysts have been carried out in a pilot plant at RON values of 98–100. From this 350-hour test, specific performance data for objective comparison of catalysts were obtained.     

Catalytic steam reforming of biomass over Ni-based catalysts: Conversion from poplar leaves to hydrogen-rich syngas

A series of Ni/SBA-15 catalysts with Ni contents from 5 wt%–20 wt%and CaO-12.5%Ni/SBA-15 catalysts with CaO contents from 1.4 wt%–9.8 wt%have been prepared.The structure of the catalysts was characterized using X-ray diffraction(XRD),N2 adsorption-desorption,transmission electron microscopy(TEM)and X-ray photoelectron spectroscopy(XPS).The performance of catalytic steam reforming of the poplar leaves to the hydrogen-rich syngas was tested in a fixed-bed reactor.The results indicate that the 7.0wt%CaO-12.5wt%Ni/SBA-15 catalyst exhibits the best performance for the catalytic steam reforming of poplar leaves to hydrogen-rich syngas.The ratio of H2:CO can reach ca 5:1 in the hydrogen-rich syngas.The yield of H2 can reach 273.30 mL/g(poplar leaves).In the CaO-Ni/SBA-15 catalyst,Ni active component mainly fills the role of catalytic steam reforming of the poplar leaves,and CaO active component mainly plays the role as water-gas shift and CO2 sorbent.     

Effect of crystallite size on the catalysis of alumina-supported cobalt catalyst for steam reforming of ethanol

The selectivity for steam reforming of ethanol on alumina-supported cobalt catalysts is closely related to the crystallite size of cobalt, which varies the strength of ethanol adsorption.     

铈源对甲醇水蒸气重整制氢CuO/CeO2催化剂的影响

采用沉淀法合成了CeO_2载体,再经浸渍法负载活性组分得到CuO/CeO_2催化材料,探究了铈源(Ce(NO_3)_3·6H_2O、Ce Cl_3·6H_2O、Ce(NH_4)_2(NO_3)_6、Ce(SO_4)_2·4H_2O)对CuO/CeO_2催化性能的影响。通过采用XRD、SEM、N_2O滴定、BET和H_2-TPR等表征手段对催化材料的结构和性质研究发现,四种铈源合成的CuO/CeO_2催化材料在Cu比表面积、还原性能以及活性组分和载体间的相互作用方面存在着明显差别。其中,由Ce(NO_3)_3·6H_2O合成的CuO/CeO_2催化材料的Cu比表面积较大,CuO还原温度较低,CeO_2载体与CuO之间相互作用较强,在甲醇水蒸气重整反应过程中,表现出较佳的催化活性,在反应温度为553 K,水醇比n(H_2O)/n(MeOH)为1.2,甲醇水蒸气气体空速(GHSV)为1760 h~(-1)时,甲醇的转化率为100%,重整气中CO摩尔含量为0.84%。     

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.     

n-Octane reforming over modified catalysts: effect of regeneration on the catalyst performance

The effect of multiple oxidation-reduction cycles on the catalyst performance was studied. Pt-Sn-Sn, Pt-Sn-Ir, Pt-Sn-Au and Pt-Sn-Pd supported on g-Al₂O₃ were compared with the reference Pt-Sn/-Al₂O₃ catalyst in n-octane test reactions. The carbonaceous deposits were burned off from the catalysts after each reaction. The regeneration procedure consisted only two steps: the burn off in air and the reduction in hydrogen. No significant change, as a consequence of the regeneration, was observed in the conversion, the liquid yield and the product distribution, except at the Pt-Sn-Pd and Pt-Sn-Au catalysts. These catalysts lost part of their activity. With the palladium modified catalyst the rupture reactions became more dominant with the number of regeneration cycles. The aromatic part of the product decreased, the isoparaffin part increased in the case of both modified catalysts. The reference, the tin and iridium modified catalysts had stable catalytic performance: the activity and selectivity of the catalysts remained constant after a few oxidation cycles.