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。     

Ni catalysts supported on nanocrystalline magnesium oxide for syngas production by CO2 reforming of CH4

CO2 reforming of methane (CDRM) was carried out over MgO supported Ni catalysts with various Ni loadings. The preparation of MgO supported Ni catalysts via surfactant-assisted precipitation method led to the formation of a nanocrystalline carrier for nickel catalysts. The synthesized samples were characterized by XRD, N2 adsorption-desorption, H2 chemisorption, TPR, TPO and SEM techniques. It was found that the high catalytic activity and stability of the prepared catalysts could be attributable to high dispersion of reduced Ni species and basicity of support surface. In addition, the effect of feed ratio, nickel loading and GHSV on the catalytic performance of CDRM over the catalysts were investigated.     

Effect of Ni loadings on the activity and coke formation of MgO-modified Ni/Al2O3 nanocatalyst in dry reforming of methane

MgO-modified Ni/Al₂O₃ catalysts with different Ni loadings were prepared and employed in dry reforming of methane (DRM). The effect of Ni loadings on the activity and coke formation of Ni/MgO-Al₂O₃ catalysts were investigated. The synthesized catalysts were characterized by XRD, N₂ adsorption-desorption, SEM, TPO and TPR techniques. The obtained results showed that increasing nickel loading decreased the BET surface area and increased the catalytic activity and amount of deposited carbon. In addition, the effect of gas hourly space velocity (GHSV) and feed ratio were studied.     

Effect of Ni loadings on the activity and coke formation of MgO-modified Ni/Al_2O_3 nanocatalyst in dry reforming of methane

MgO-modified Ni/Al2O3 catalysts with different Ni loadings were prepared and employed in dry reforming of methane （DRM）. The effect of Ni loadings on the activity and coke formation of Ni/MgO-A1203 catalysts were investigated. The synthesized catalysts were characterized by XRD, N2 adsorption-desorption, SEM, TPO and TPR techniques. The obtained results showed that increasing nickel loading decreased the BET surface area and increased the catalytic activity and amount of deposited carbon. In addition, the effect of gas hourly space velocity （GHSV） and feed ratio were studied.     

Dry reforming reaction over nickel catalysts supported on nanocrystalline calcium aluminates with different CaO/Al2O3 ratios

Nanocrystalline calcium aluminates with different CaO/Al2O3 ratios were prepared by a facile co-precipitation method using Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG, MW: 5800) as a surfactant. They were employed as catalyst support for nickel catalysts in methane reforming with carbon dioxide. The prepared samples were characterized by X-ray diffraction (XRD), N2 adsorption (BET), temperature-programmed reduction and oxidation (TPR-TPO), and scanning electron microscopy (SEM) techniques. Catalysts showed a relatively high catalytic activity and stability. TPR analysis revealed that the catalysts with higher CaO content are more difficult to be reduced. TPO analysis showed that the 5 wt%Ni/CA and 5 wt%Ni/C12A7 catalysts with higher CaO amount were effective against coke deposition.     

载体类型对Ni基催化剂甲烷干重整反应性能的影响

以不同载体负载NiO制备了甲烷干重整催化剂并对所制备的催化剂采用等温氮气吸附、XRD、H₂-TPR、H₂化学吸附等进行了表征。结果表明,载体性质对NiO的存在状态影响较大。SiO₂、TiO₂以及ZrO₂与NiO的相互作用较弱,催化剂易于被还原活化,而正是由于其与NiO的弱相互作用,导致活性金属在反应过程中易迁移聚集而失活。Al₂O₃和MgO均与NiO有强相互作用,易分别生成NiAl₂O₄尖晶石和NiO-MgO固溶体,导致其难以被还原活化。经MgO改性的Al₂O₃载体不仅具有较大的比表面积,而且与NiO的相互作用强度适中,这有利于NiO的分散和稳定,以其为载体制备的催化剂在较高空速下表现出优异的催化反应活性和稳定性,催化剂连续稳定运行100h不失活。     

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。     

Regeneration of C4H10 dry reforming catalyst by nonthermal plasma

Carbon deposition via coke formation is one of the critical problems causing catalyst deactivation during the reforming of hydrocarbons. An effort was made to regenerate the catalyst (Ni/γ-alumina) by oxidation methods. Two approaches were carried out for the regeneration of the deactivated catalyst. The first one involves the plasma treatment of the deactivated catalyst in the presence of dry air over a temperature range of 300～500 °C, while the second one only the thermal treatment in the same temperature range. The performance of the regenerated catalyst was evaluated in terms of C₄H₁₀ and CO₂ conversions and the physicochemical characteristics were examined using a surface area analyzer, an elemental analyzer, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was observed that the carbon deposit (coke) on the catalyst was about 9.89 wt% after reforming C₄H₁₀ for 5 h at 540 °C. The simple thermal treatment at 400 °C reduced carbon content to 6.59 wt% whereas it was decreased to 3.25 wt% by the plasma and heat combination. The specific surface area was fully restored to the original state by the plasma-assisted regeneration at 500 °C. As far as the catalytic activity is concerned, the fresh and regenerated catalysts exhibited similar C₄H₁₀ and CO₂ conversion efficiencies.     

制备方法对甲烷干重整催化剂Ni/La2O3/Al2O3结构及性能的影响

采用浸渍法及蒸发法制备了Ni/La₂O₃/Al₂O₃催化剂,考察了制备方法对其结构及甲烷干重整催化性能的影响。通过XRD、H₂ TPR、BET、TEM、TG-DSC等方法对催化剂进行了表征。结果表明,浸渍法制备的催化剂具有较好的Ni分散性、更均匀的粒径分布,较大的比表面积及更优的孔结构,从而具有更好的Ni抗烧结能力及抗积炭性。浸渍法制备的催化剂平均积炭速率很低,约为0.6737mg/(g_cat·h),相当于蒸发法制备催化剂的21%。活性测试结果表明,浸渍法制备的催化剂上CH₄、CO₂转化率及H₂、CO选择性比蒸发法制备的催化剂分别高约5%、10%及4%、3%,具有更好的稳定性。     

SiO2和Al2O3负载的Ni基催化剂在甲烷干重整中的催化性能差异

CH₄与CO₂干重整反应对于环境保护和天然气资源的合理利用具有重要意义。SiO₂和Al₂O₃是适用于甲烷干重整反应的两种典型的催化剂载体。为了阐明这两种载体对催化剂性能的影响,本研究采用等体积浸渍法制备了Ni/Al₂O₃和Ni/SiO₂催化剂,并利用BET、TEM、H₂-TPR、XRD、TG和Raman等技术对还原和反应后的催化剂进行了表征。结果表明,由于载体的性质不同,Ni基催化剂在甲烷干重整中的催化性能也不同。Ni/SiO₂催化剂的初始活性较高,但由于其金属-载体相互作用较弱,催化稳定性较差,在800℃下反应15h其催化活性急剧下降;较弱的金属-载体相互作用使得Ni/SiO₂催化剂上的Ni颗粒较大,有利于积炭前驱物种的生成,导致催化剂快速失活。而对于Ni/Al₂O₃催化剂,金属-载体相互作用较强,Ni颗粒较小,但由于Ni与Al₂O₃生成了NiAl_xO_y物种,有效活性位减少,其催化活性相对较低,但催化稳定性较好,干重整反应进行50h其活性保持稳定;Ni与Al₂O₃之间较强的相互作用有利于形成小且稳定的Ni粒子,能减少积炭,因而具有优异的催化稳定性。     

CO2 reforming of methane over nickel catalysts supported on nanocrystalline MgAl2O4 with high surface area

In this paper dry reforming of methane (DRM) was carried out over nanocrystalline MgAl2O4-supported Ni catalysts with various Ni loadings. Nanocrystalline MgAl2O4 spinel with high specific surface area was synthesized by a co-precipitation method with the addition of pluronic P123 triblock copolymer as surfactant, and employed as catalyst support. The prepared samples were characterized by X-ray diffraction (XRD), N2 adsorption, H2 chemisorption, temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), temperature- programmed desorption (TPD) and transmission and scanning electron microscopies (TEM, SEM) techniques. The obtained results showed that the catalyst support has a nanocrystalline structure (crystal size: about 5 nm) with a high specific surface area (175 m2 g-1) and a mesoporous structure. Increasing in nickel content decreased the specific surface area and nickel dispersion. The prepared catalysts showed high catalytic activity and stability during the reaction. SEM analysis revealed that whisker type carbon deposited over the spent catalysts and increasing in nickel loading increased the amount of deposited carbon. The nickel catalyst with 7 wt% of nickel showed the highest catalytic activity.     

液相中镍催化剂催化合成气甲烷化的初步研究

采用液相还原法制备非负载型镍催化剂,将非负载型镍催化剂分散在液相供氢溶剂十氢萘中,催化合成气甲烷化反应。在高压反应釜内,考察了反应温度、物质的量比等操作条件下,镍催化剂催化合成气甲烷化反应的反应活性。并对催化剂进行XRD、SEM、H2-TPR表征分析。研究结果表明,在330℃、催化剂用量为2%时,产品气中甲烷含量可达89.39%,CO和H2的转化率分别为94.56%和92.60%;催化剂用量为4%时,产品气中甲烷含量可高达94.26%,CO的转化率可达到99%以上。合成气甲烷化反应的最佳操作温度为330℃,H2/CO物质的量比最佳为2.20~2.67。     

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.     

Influence of samarium on the hydrogenation properties of supported nickel catalyst

The effect of samarium on Ni/sepiolite catalyst was investigated by benzene hydrogenation, methanation of carbon dioxide, CO chemisorption, XPS and CS₂ poisoning, respectively. The result indicates that a proper amount and impregnation order of samarium in the preparation of Ni-Sm/sepiolite catalyst are very efficient to improve the catalytic activity and anti-sulfur ability. At the same time, the mechanism of samarium improving hydrogenation activity of Ni/sepiolite is presented.     

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。     

泡沫镍及负载型镍催化剂制备纳米碳纤维层的研究

纳米碳纤维可用在催化材料、储氢材料、及纳米电子器件等方面。本文对用泡沫镍及负载型镍催化剂催化分解乙烯或丙烯制备纳米碳纤维进行了研究。利用X射线衍射仪、物理吸附仪、扫描电镜进行了分析表征,并考察了催化剂、碳源、生长温度对纳米碳纤维生长量、形貌、结构的影响。结果表明:在生长温度450℃,乙烯流率30mL/m in的条件下,负载型镍催化剂纳米碳纤维的生长量要高出泡沫镍3~6倍,负载型镍催化剂制备的纳米碳纤维直径为40~60纳米,小于泡沫镍的情况。泡沫镍催化分解乙烯制备纳米碳纤维时,纳米碳纤维的生长量和平均直径随温度的降低而逐渐减小。纳米碳纤维在泡沫镍上的最低生长温度为420℃,在低于480℃生长纳米碳纤维时泡沫镍的骨架结构不会被破坏,由此制备的纳米碳纤维在新型结构催化材料中有很好的的应用前景。     

有机蒙脱土负载镍催化剂上乙醇重整制氢

采用浸渍法制备了有机改性蒙脱土(OMt)负载的Ni/有机蒙脱土(Ni/OMt)催化剂,用于乙醇重整制氢;通过XRD、FT-IR、H₂-TPR、SEM、XPS和氮吸附等手段对催化剂进行了表征分析。结果表明,与未改性的蒙脱土负载的Ni催化剂(Ni/MMT)相比,有机改性可显著提高其比表面积、孔容和金属Ni的分散度,降低碳沉积量,改善Ni/MMT催化剂的稳定性。Ni/OMt催化剂表现出较高的乙醇重整制氢催化性能,在773K下反应30 h,乙醇转化率保持在100%,氢气选择性为70%;而Ni/MMT催化剂在反应10 h即开始失活,碳沉积严重,同时产生副产物乙烯和乙醛。使用十六烷基三甲基溴化铵(CTAB)改性可促进Ni高分散在MMT层板上,抑制积炭对活性金属Ni包裹,提高其乙醇重整氢气选择性、降低乙烯和乙醛的选择性。     

氮化SBA-16负载镍基催化剂的制备及其对甲烷二氧化碳重整反应的催化性能

通过软模板法合成了SBA-16分子筛,采用高温氨气氮化的方法使有序介孔硅材料中的氧原子部分被氮原子取代,得到氮化的SBA-16载体(SBA-16-N)。采用满孔浸渍法制备了镍基催化剂,并将制得的Ni/SBA-16和Ni/SBA-16-N催化剂用于甲烷二氧化碳重整反应。通过透射电镜、氮气物理吸附、X射线衍射、X射线光电子能谱和二氧化碳程序升温脱附等手段研究了载体和催化剂的结构,并利用热重分析对反应之后回收催化剂进行了表征。结果表明,高温氮化后的分子筛中掺入了氮元素,增加了载体的碱性,改善了载体对反应气体的吸附活化能力,增强了载体与金属之间的相互作用,从而提高了催化剂的活性和抗积炭性能。     

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.     

Characterization of La-promoted Ni/Al2O3 catalysts for hydrogen production from glycerol dry reforming

In the current paper, dry (CO₂)-reforming of glycerol, a new reforming route, was carried out over alumina (Al₂O₃)-supported, non-promoted and lanthanum-promoted nickel (Ni) catalysts. Both sets of catalysts were synthesized via a wet co-impregnation procedure. Physicochemical characterization of the catalysts showed that the promoted catalyst possessed smaller metal crystallite size, hence higher metal dispersion compared to the virgin Ni/Al₂O₃ catalyst. This was also corroborated by the surface images captured by the FESEM analysis. From temperature-programmed calcination analysis, the derivative weight profiles revealed two peaks, which represent a water elimination peak at a temperature range of 373 to 473 K followed by nickel nitrate decomposition from 473 to 573 K. In addition, BET surface area measurements gave 85.0 m²·g⁻¹ for the non-promoted Ni catalyst, whilst the promoted catalysts showed an average of 1% to 6% improvement depending on the La loadings. Significantly, reaction studies at 873 K showed that glycerol dry reforming successfully produced H₂. The 2%La-Ni/Al₂O₃ catalyst, which possessed the largest BET surface area, gave an optimum H₂ generation (9.70%) at a glycerol conversion of 24.5%.