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 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.     

Hydrogen production by steam reforming of glycerol over Ni/Ce/Cu hydroxyapatite-supported catalysts

Hydroxyapatite-supported Ni-Ce-Cu catalysts were synthesised and tested to study their potential for use in the steam reforming of glycerol to produce hydrogen. The catalysts were prepared by the deposition-precipitation method with variable nickel, cerium, and copper loadings. The performance of the catalysts was evaluated in terms of hydrogen yield at 600°C in a tubular fixed-bed microreactor. All catalysts were characterised by the BET surface area, XRD, TPR, TEM, and FE-SEM techniques. The reaction time was 240 min in a fixed-bed reactor at 600°C and atmospheric pressure with a water-to-glycerol feed molar ratio of 8: 1. It was found that the Ni-Ce-Cu (3 mass %-7.5 mass %-7.5 mass %) hydroxyapatite-supported catalyst afforded the highest hydrogen yield (57.5 %), with a glycerol conversion rate of 97.3 %. The results indicate that Ni/Ce/Cu/hydroxyapatite has great potential as a catalyst for hydrogen production by steam reforming of glycerol.     

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.     

钙钛矿型氧化物负载Ni催化剂上甲烷二氧化碳重整反应研究

采用浸渍法制备了一系列MTiO₃(M=Mg、Ca、Sr、Ba)钙钛矿型氧化物负载的Ni催化剂(Ni的负载量为5%,质量分数),通过XRD、氮吸附、H₂-TPR、CO₂-TPD、XPS和TG等技术对催化剂进行了表征,对其甲烷二氧化碳重整反应的催化性能进行了研究。结果表明,M为不同碱土金属时,催化剂上金属载体相互作用、活性组分的表面原子浓度以及催化剂晶格氧的流动性都发生了变化。Ni/CaTiO₃催化剂上金属载体相互作用较强,还原出的活性组分Ni的含量较多,晶格氧流动性较高,因而具有较好的催化性能。SrTiO₃载体颗粒粒径较大,Ni/SrTiO₃催化剂上Ni的分散度不高,金属载体的相互作用较弱,表面Ni原子相对含量较低,晶格氧的流动性较差,其甲烷二氧化碳重整反应活性也最低。     

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。     

Thermal dry reforming of methane over La2O3 co-supported Ni/MgAl2O4 catalyst for hydrogen-rich syngas production

Research on Chemical Intermediates - The excess emission of greenhouse gases (GHGs) such as CO2 and CH4 is posing an acute threat to the environment, and efficient ways are being sought to utilize...     

Syngas production by biogas reforming over the Co-based multicomponent catalysts

The new multicomponent Co-based catalysts with additives of group 8 metal and rare earth elements and supported on alumina have been tested in the dry and steam conversion of a model biogas. The processes were carried out in a flow quartz reactor under the following conditions: atmospheric pressure, a gas hourly space velocity of 1000 h^?1 and temperatures of 300–800°C. The catalysts were characterised using electron microscopy, BET and X-ray analysis. The methane is almost completely converted in the dry reforming of biogas at T≤800°C. Synthesis gas with a ratio of H₂/CO>1.0 is a main product of biogas reforming over the multicomponent catalysts studied. Adding steam in a feed composition increases both the methane conversion and the hydrogen yield at lower temperatures. Almost complete methane conversion occurs at T<750°C in the steam reforming of biogas. The catalysts are highly effective and exhibit stable activity throughout 100 h of continuous testing.      

Methanation of syngas over coral reef-like Ni/Al_2O_3 catalysts

Coral reef-like Ni/Al2O3 catalysts were prepared by co-precipitation of nickel acetate and aluminium nitrate with sodium carbonate aqueous solution in the medium of ethylene glycolye.Methanation of syngas was carried out over coral reef-like Ni/Al2O3 catalysts in a continuous flow type fixed-bed reactor.The structure and properties of the fresh and used catalysts were studied by SEM,N2 adsorption-desorption,XRD,H2-TPR,O2-TPO,TG and ICP-AES techniques.The results showed that the coral reef-like Ni/Al2O3 catalysts exhibited better activity than the conventional Ni/Al2O3-H2O catalysts.The activities of coral reef-like catalysts were in the order of Ni/Al2O3-673>Ni/Al2O3-573>Ni/Al2O3- 473>Ni/Al2O3-773.Ni/Al2O3-673-EG catalyst showed not only good activity and improved stability but also superior resistance to carbon deposition,sintering,and Ni loss.Under the reaction conditions of CO/H2(molar ratio)=1:3,593 K,atmospheric pressure and a GHSV of 2500 h-1,CH4 selectivity was 84.7%,and the CO conversion reached 98.2%.     

Steam reforming of ethylene glycol over Ni-based catalysts: the effect of K

The effect of K on the activities of Ni/Al₂O₃ catalysts in steam reforming of ethylene glycol was investigated. Ni/Al₂O₃ catalysts were prepared by incipient wetness impregnation and co-precipitation methods. The addition of K was achieved using an incipient wetness impregnation method. The prepared catalysts were characterized by N₂ physisorption, inductively coupled plasma-atomic emission spectroscopy, X-ray diffraction, temperature-programmed reduction, and scanning electron microscopy. Irrespective of the preparation method, the promotional effect of K was observed and the optimum K content (~5 wt%) was verified for K-promoted Ni/Al₂O₃ catalysts. The addition of K to the Ni–Al₂O₃ catalyst prepared by co-precipitation led to higher catalytic activity than addition of K to the Ni/Al₂O₃ catalyst prepared by incipient wetness impregnation.     

Ni-La催化剂上乙醇水蒸气重整制氢——燃料电池氢源技术

采用浸渍法制备出γ-Al2O3、SiO2和γ-Al2O3·SiO2负载的Ni-La催化剂,用XRD、TPR、XPS、H2-TPD、NH3-TPD和TG等手段对催化剂进行了表征,结果表明:这3种负载型催化剂中的活性组分Ni的分散度较高,La3 氧化物高度分散于载体表面.在温度为400℃、水醇比为4.0和液体空速为8.0 mL h-1 g-1cat的条件下,催化剂进行稳定性测试,结果表明:γ-Al2O3·SiO2负载的Ni-La催化剂在整个100 h稳定性测试过程中,氢气的选择性保持在67.0%左右,且稳定性良好.对经过稳定性测试后的Ni-La催化剂进行热重分析,发现γ-Al2O3·SiO2负载的Ni-La催化剂具有较少的积碳量,仅仅是0.86 g C·g-1cat,其中石墨碳占42.81%.     

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.     

Ultra-stable Ni catalysts for methane reforming by carbon dioxide

Methane reforming by carbon dioxide has been studied over ultra-stable Ni catalysts. The catalyst was characterized by XRD, IR and TEM and temperature programmed hydrogenation. The nickel–magnesia solid solution catalyst containing low nickel has shown excellent stability (>3000 h) and no carbon deposition in the methane reforming by carbon dioxide. It was also found that the small nickel metal particle interaction with support surface is effective for the inhibition of carbon formation.     

Energy-efficient syngas production through catalytic oxy-methane reforming reactions

The considerable recent interest in the conversion of stranded methane into transportable liquids as well as fuel cell technology has provided a renewed impetus to the development of efficient processes for the generation of syngas. The production of syngas (CO/H2), a very versatile intermediate, can be the most expensive step in the conversion of methane to value-added liquid fuels. The catalytic oxy reforming of methane, which is an energy-efficient process that can produce syngas at extremely high space-time yields, is discussed in this Review. As long-term catalyst performance is crucial for the wide-scale commercialization of this process, catalyst-related studies are abundant. Correspondingly, herein, emphasis is placed on discussing the different issues related to the development of catalysts for oxy reforming. Important aspects of related processes such as catalytic oxy-steam, oxy-CO2, and oxy-steam-CO2 processes will also be discussed.     

Steam reforming of methanol over Ni, Co, Pd and Pt supported on ZnO

Pd/ZnO and Pt/ZnO exhibited anomalously high selectivity for the steam reforming of methanol, when PdZn and PtZn alloys phases were developed. The selectivity decreased over the catalysts having metal phases.     

B改性CuZnAlOx催化剂对甲醇水蒸气重整制氢性能的研究

采用共沉淀法制备CuZnAlO_x（CZA）催化剂,通过浸渍法得到一系列不同硼（B）负载量的yB/CZA（y=0.28%、0.38%、0.73%、0.89%和4.10%,质量分数）催化剂,并将其用于甲醇水蒸气重整制氢反应。此外,为探究催化剂的构效关系,采用ICP、BET、SEM、N₂O化学吸附、TEM、XRD、H₂-TPR和XPS等手段对催化剂进行表征。结果表明,B引入主要影响催化剂的Cu分散性、还原性及Cu-B间相互作用,进而影响甲醇水蒸气重整制氢性能。其中,0.38B/CZA催化剂获得最高催化活性,这与其具有较高的Cu分散性与较强的Cu-B相互作用力有关;在反应温度为250℃,n（H₂O）：n（CH₃OH）=3,空速为9000 mL/（g·h）时,CH₃OH转化率达到93%,CO选择性仅有0.3%,且反应102 h后仍未失活。     

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。     

Hydrogen production from simulated hot coke oven gas by catalytic reforming over Ni/Mg（Al）O catalysts

Hydrogen production by catalytic reforming of simulated hot coke oven gas (HCOG) with toluene as a model tar compound was investigated in a fixed bed reactor over Ni/Mg(Al)O catalysts. The catalysts were prepared by a homogeneous precipitation method using urea hydrolysis and characterized by ICP, BET, XRD, TPR, TEM and TG. XRD showed that the hydrotalcite type precursor after calcination formed (Ni, Mg)Al₂O₄ spinel and Ni-Mg-O solid solution structure. TPR results suggested that the increase in Ni/Mg molar ratio gave rise to the decrease in the reduction temperature of Ni²⁺ to Ni⁰ on Ni/Mg(Al)O catalysts. The reaction results indicated that toluene and CH₄ could completely be converted to H₂ and CO in the catalytic reforming of the simulated HCOG under atmospheric pressure and the amount of H₂ in the reaction effluent gas was about 4 times more than that in original HCOG. The catalysts with lower Ni/Mg molar ratio showed better catalytic activity and resistance to coking, which may become promising catalysts in the catalytic reforming of HCOG.     

Steam reforming of toluene as model of tar compound over Mo catalysts derived from hydrotalcites

This study evaluated the catalytic activity of Mo catalysts derived from hydrotalcite-like compounds for steam reforming of toluene as a model compound for tar. The catalysts with 1.5, 3 and 4.5 Mo loadings (wt%), denoted as Mo_1.5MgAl, Mo₃MgAl and Mo_4.5MgAl respectively, were prepared by coprecipitation and characterized by BET, XRD, SEM, TEM, FT-IR and UV–VIS. The results showed that toluene conversion increased with increasing molybdenum content. The hydrogen amount depended on two factors: the presence of molybdate species on the surface and the presence of aluminum cations in tetrahedral sites (Mo₃MgAl), with molybdenum influence being more pronounced. The H₂/CO ratio decreased at increasing temperature while, the H₂/CO₂ ratio increased proportionally with temperature. Mo_1.5MgAl catalyst was more selective for CO₂ and H₂, while, Mo₃MgAl and Mo_4.5MgAl were more selective for CO and H₂.