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.     

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.     

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。     

Effect of O2 and H2O on the tri-reforming of the simulated biogas to syngas over Ni-based SBA-15 catalysts

A series of Ni/SBA-15 catalysts with Ni contents from 7.5 wt% to 15 wt% were prepared by impregnation method. The effect of O2 and H2O on the combined reforming of the simulated biogas to syngas was investigated in a continuous flow fixed-bed micro-reactor. The stability of the catalyst was tested at 800 ℃. The results indicated that 10 wt%Ni/SBA-15 catalyst exhibited the highest catalytic activities for the combined reforming of the simulated biogas to syngas. Under the reaction conditions of the feed gas molar ratios CH4/CO2/O2/H2O = 2/1/0.6/0.6, GHSV = 24000 ml•g{cat}-1\cdoth-1 and the reaction temperatureT = 800 ℃, the conversions of CH4 and CO2 were 92.8% and 76.3%, respectively, and the yields of CO and H2 were 99.0% and 82.0%, respectively. The catalytic activities of the catalyst did not decrease obviously after 100 h reaction time on stream.     

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。     

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。     

Hydrogen and syngas production from two-step steam reforming of methane using CeO2 as oxygen carrier

CeO2 oxygen carrier was prepared by precipitation method and tested by two-step steam reforming of methane (SRM). Two-step SRM for hydrogen and syngas generation is investigated in a fixed-bed reactor. Methane is directly converted to syngas at a H2/CO ratio close to 2 : 1 at a high temperature (above 750 °C) by the lattice oxygen of CeO2; methane cracking is found when the reduction degree of CeO2 was above 5.0% at 850 °C in methane isothermal reaction. CeO2?δ obtained from methane isothermal reaction can split water to generate CO-free hydrogen and renew its lattice oxygen at 700 °C; simultaneously, deposited carbon is selectively oxidized to CO2 by steam following the reaction (C+2H2O→CO2+2H2). Slight deactivation in terms of amounts of desired products (syngas and hydrogen) is observed in ten repetitive two-step SRM process due to the carbon deposition on CeO2 surface as well as sintering of CeO2.     

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.     

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.     

镍基整体式催化剂上生物质粗燃气重整调变的特性研究

采用浸渍法制备了Ni基整体式催化剂,考察了不同条件(温度、时间、空速、水蒸气添加等)对催化剂上生物质粗燃气重整反应性能的影响。结果表明,催化剂在较低温度下(≤500 ℃)只具有CO加氢反应活性,随着反应温度的升高粗燃气重整反应逐渐进行,在800 ℃以上,CH₄和C₂转化率均高达95 %以上,CO₂转化率达到92%,但随着反应空速和水蒸气添加量的增加,CH₄和CO₂等转化率呈现缓慢降低的趋势。此外,通过改变水蒸气添加量可对合成气中H₂/CO体积比在0.85~4.00进行较好调节。结合XRD表征发现,Ni基整体式催化剂中Ni°的生成可较好地促进重整反应的进行。     

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。     

Effect of MgO promoter on Ni-based SBA-15 catalysts for combined steam and carbon dioxide reforming of methane

A series of Ni/SBA-15 catalysts with Ni contents ranging from 5 wt% to 15 wt%, as well as another series of 10%Ni/MgO/SBA-15 catalysts, in which the range of the MgO content was from 1 wt% to 7 wt%, were prepared, and their catalytic performances for the reaction of combined steam and carbon dioxide reforming of methane were investigated in a continuous flow microreactor. The structures of the catalysts were characterized using the XRD, H2-TPR and CO2-TPD techniques. The results indicated that the CO selectivity for this reaction was very close to 100%, and the H2/CO ratio of the product gas could be controlled by changing the H2O/CO2 molar ratio of the feed gas. The simultaneous and plentiful existing of steam and CO2 had a significant influence on the catalytic performance of the 10%Ni/SBA-15 catalyst without modification. After reacting at 850 °C for 120 h over this catalyst, the CH4 conversion dropped from 98% to 85%, and the CO2 conversion decreased from 86% to 53%. However, the 10%Ni/3%MgO/SBA-15 catalyst exhibited a much better catalytic performance, and after reacting for 620 h, the CO2 conversion over this catalyst dropped from 92% to around 77%, while the CH4 conversion was not decreased. Oxidation of the Ni0 species as well as carbon deposition during the reaction were the main reasons for the deactivation of the catalyst without modification. On the other hand, modification by the MgO promoter improved the dispersion of the Ni0 species, and enhanced the CO2 adsorption affinity which in turn depressed the occurring of carbon deposition, and thus retarded the deactivation process.     

催化热解生物质制取富氢气体的研究

在实验室自制的固定床反应器上, 考察了秸秆和锯屑的热解行为, 研究了热解产物分布特别是富氢气体的体积分数和产率, 着重研究了（5种金属氧化物和2种碳酸盐催化剂）的催化效果。结果表明,温度从500 ℃提高到850 ℃, 秸秆和锯屑的热解气产率分别从29.0%提高到40.6%, 35.0％提高到46.5%, 而对应的富氢气体的体积分数分别从41.2％提高到48.2%, 40.6％提高到47.0%；在5种金属氧化物中，Cr2O3显示了最好的催化效果，在750 ℃时对应的热解气产率与不使用催化剂相比提高了10％，富氢气体的体积分数提高了13％；催化剂（CaCO3和Na2CO3）占生物质的质量分数对热解气和富氢气体产率有明显的影响，当质量分数从0增加到30％时， 热解气和富氢气体产率增加较明显，而后其值的增加可以忽略， 因此推荐使用的催化剂质量分数为30％。     

Ethanol reforming processes over ZnO-supported palladium catalysts: Effect of alloy formation

ZnO- and SiO₂-supported palladium catalysts were evaluated in the ethanol steam-reforming and oxidative ethanol steam-reforming reactions in the temperature range 548–723 K. The catalysts were characterized before and after reaction by X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy and infrared spectroscopy using CO as a probe molecule. On silica-supported Pd catalyst, ethanol decomposes into H₂, CO and CH₄ in both steam-reforming and oxidative steam-reforming reactions. In contrast, ZnO-supported catalysts containing the PdZn phase exhibit a better catalytic performance for hydrogen production through dehydrogenation of ethanol into acetaldehyde and ulterior reforming.     

Low CO content hydrogen production from oxidative steam reforming of ethanol over CuO-CeO2 catalysts at low-temperature

CuO-CeO₂ catalysts were prepared by a urea precipitation method for the oxidative steam reforming of ethanol at low-temperature. The catalytic performance was evaluated and the catalysts were characterized by inductively coupled plasma atomic emission spectroscopy, X-ray diffraction, temperature-programmed reduction, field emission scanning electron microscopy and thermo-gravimetric analysis. Over CuO-CeO₂ catalysts, H₂ with low CO content was produced in the whole tested temperature range of 250–450 °C. The non-noble metal catalyst 20CuCe showed higher H₂ production rate than 1%/oRh/CeO₂ catalyst at 300–400 °C and the advantage was more obvious after 20 h testing at 400 °C. These results further confirmed that CuO-CeO₂ catalysts may be suitable candidates for low temperature hydrogen production from ethanol.     

Methane reforming With CO2 to syngas over CeO2-promoted Ni/Al2O3-ZrO2 catalysts Prepared Via a direct sol-gel process

CeO2-promoted Ni/Al2O3-ZrO2 (Ni/Al2O3-ZrO2-CeO2) catalysts were prepared by a direct sol-gel process with citric acid as gelling agent. The catalysts used for the methane reforming with CO2 was studied by infrared spectroscopy (IR), thermal gravimetric analysis (TGA), microscopic analysis, X-ray diffraction (XRD) and temperature-programmed reduction (TPR). The catalytic performance for CO2 reforming of methane to synthesis gas was investigated in a continuous-flow micro-reactor under atmospheric pressure. TGA, IR, XRD and microscopic analysis show that the catalysts prepared by the direct sol-gel process consist of Ni particles with a nanostructure of around 5 nm and an amorphous-phase composite oxide support. There exists a chemical interaction between metallic Ni particles and supports, which makes metallic Ni well dispersed, highly active and stable. The addition of CeO2 effectively improves the dispersion and the stability of Ni particles of the prepared catalysts, and enhances the adsorption of CO2 on the surface of catalysts. The catalytic tests for methane reforming with CO2 to synthesis gas show that the Ni/Al2O3-ZrO2-CeO2 catalysts show excellent activity and stability compared with the Ni/Al2O3 catalyst. The excellent catalytic activity and stability of the Ni/Al2O3-ZrO2-CeO2 are attributed to the highly, uniformly and stably dispersed small metallic Ni particles, the high reducibility of the Ni oxides and the interaction between metallic Ni particles and the composite oxide supports.     

生物质气催化合成甲醇的研究

在高压微型反应装置上进行了生物质气合成甲醇的研究。利用组成为H2/CO/CO2 /N2(体积比)=52.5/21.5/22.8/3.2 的富CO2原料气考察了不同温度、压力和空速条件时甲醇的时空产率和质量分数。结果表明,在所考察的范围内,甲醇的产率和质量分数在260 ℃达到最大。产率和质量分数随反应压力升高而增大,空速增加使产率增大,甲醇的质量分数降低。当p=4 MPa,t=260 ℃,WHSV=5 280 h-1时, 甲醇的时空产率为0.79 g·（mL·h）－１,质量分数为96.2%,与工业合成气相比,分别下降25.8％和1.64％。     

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.     

Steam reforming of dimethyl ether to hydrogen-rich gas

The steam reforming of dimethyl ether (DME) (SR) to a hydrogen-rich gas over a mechanical mixture of WO_x/ZrO₂ (the DME hydration catalyst) and CuZnAlO_x (the methanol SR catalyst) was studied. The mechanically mixed catalyst was shown to provide almost complete conversion of DME to the hydrogen-rich gas containing <0.5 vol.% of CO at 300°C, atmospheric pressure, gas hourly space velocity (GHSV) of 10000 h⁻¹ and molar ratio H₂O/DME = 3. The hydrogen production rate in DME SR was found to reach 180–250 mmol H₂/(g_cat·h) at 250–300°C.