Hydrogen Production from Ethanol Steam Reforming Over Supported Cobalt Catalysts

Hydrogen production was carried out via ethanol steam reforming over supported cobalt catalysts. Wet incipient impregnation method was used to support cobalt on ZrO₂, CeO₂ and CeZrO₄ followed by pre-reduction with H₂ up to 677 °C to attain supported cobalt catalysts. It was found that the non-noble metal based 10 wt.% Co/CeZrO₄ is an efficient catalyst to achieve ethanol conversion of 100% and hydrogen yield of 82% (4.9 mol H₂/mol ethanol) at 450 °C, which is superior to 0.5 wt.% Rh/Al₂O₃. The pre-reduction process is required to activate supported cobalt catalysts for high H₂ yield of ethanol steam reforming. In addition, support effect is found significant for cobalt during ethanol steam reforming. 10% Co/CeO₂ gave high H₂ selectivity while suffered low conversion due to the poor thermal stability. In contrast to CeO₂, 10 wt.% Co/ZrO₂ achieved high conversion while suffered lower H₂ yield due to the production of methane. The synergistic effect of ZrO₂ and CeO₂ to promote high ethanol conversion while suppress methanation was observed when CeZrO₄ was used as a support for cobalt. This synergistic effect of CeZrO₄ support leads to a high hydrogen yield at low temperature for 10 wt.% Co/CeZrO₄ catalyst. Under the high weight hourly space velocity (WHSV) of ethanol (2.5 h⁻¹), the hydrogen yield over 10 wt.% Co/CeZrO₄ was found to gradually decrease to 70% of its initial value in 6 h possibly due to the coke formation on the catalyst.     

Ethanol Steam Reforming Followed by Water-Gas Shift Reaction over Ce-Ni/MCM-41 and Fe-Based Catalysts

Current research focuses on hydrogen production from ethanol steam reforming (ESR) followed by water-gas shift (WGS) reaction. Ce-Ni/MCM-41 and Fe/Ce/M (where M = K, La, Ti) catalysts were prepared by the wet-impregnation technique and used for the ESR and WGS reactions, respectively. All experiments were carried out at 600 °C. The effects of the reduction time, the ratio of the two catalysts, and their arrangement were also investigated. The best results were obtained using Fe/Ce/Ti as WGS catalyst and with a separate array because the H₂ production and CO₂ level in the product gas were improved while that of CO was reduced. To generate high-purity hydrogen, the CaO-based adsorbent was used as a third layer to adsorb CO₂ from the gaseous products.     

Hydrogen Production from Ethanol Steam Reforming Over Ni/CeO2 Nanocomposite Catalysts

The organic polymer chitosan was used as the polymeric precursor for the synthesis of Ni/CeO₂ nanocomposite catalysts. The materials were characterized by N₂ physisorption, H₂ chemisorption, AA, XRD, TGA, TPR, SEM and TEM analyses. The catalysts provide very good reactivity in ethanol steam reforming compared to the conventional Ni/CeO₂ catalyst prepared by the impregnation method using a commercial support. High hydrogen selectivity (>75%) was obtained on Ni/CeO₂ catalysts by operating at a temperature range of 325–500 °C and a H₂O/C₂H₅OH molar ratio of 3. It was verified that the catalytic behavior could be influenced depending on the experimental conditions employed.     

On the Catalytic Activity of Cobalt Oxide for the Steam Reforming of Ethanol

The paper presents an investigation on the catalytic activity for the ethanol steam reforming of Co₃O₄ oxidized, reduced and supported on MgO, and of CoO in MgO solid solution. Only samples containing metallic cobalt are found to be active for reforming reaction. H₂-TPR characterization of aged samples shows that reaction mixture oxidizes a small fraction of metallic cobalt to Co⁺². A distinct role of Co⁺² and Co⁰ in the reaction is enlightened.     

Steam reforming of ethanol over Pt–Ni Catalysts

A parametric study was conducted over Pt–Ni/δ-Al₂O₃ to explore the effect of Pt and Ni contents on the ethanol steam reforming characteristics of the bimetallic catalyst. Experiments with catalysts having 0.2–0.3 wt%Pt and 10–15 wt%Ni contents indicated that the best ethanol steam reforming performance is achieved over 0.3 wt%Pt–15 wt%Ni/δ-Al₂O₃. Kinetics of ethanol steam reforming was studied over this catalyst in the 673–823 K interval using differential and integral methods of data analysis. A power-function rate expression was obtained with reaction orders of 1.01 and −0.09 in ethanol and steam, respectively, and the apparent activation energy of ethanol steam reforming over 0.3 wt%Pt–15 wt%Ni/δ-Al₂O₃ was calculated as 59.3 ± 2.3 kJ mol⁻¹.     

Reactivity of Aluminum Spinels in the Ethanol Steam Reforming Reaction

Aluminum spinels, MAl₂O₄ with M²⁺ = Cu, Zn or Ni, were prepared by citrate method and its reactivity in the ethanol steam reforming reaction was studied at 500 °C. They were characterized by TG, BET surface area, XRD, FTIR and TPR techniques. The catalytic behavior depended strongly on the nature of divalent metal which determines the physico-chemical properties of samples. In all cases, very active catalysts with a complete ethanol conversion were reached. Hydrogen yield follows the order of ZnAl > NiAl > CuAl.     

载体对镍基催化剂及其甲苯水蒸气重整性能的影响

采用等体积浸渍法制备了MgO、HZSM-5、y-Al2O3、TiO2和SiO2负载的镍催化剂,考察了不同载体负载的镍基催化剂在甲苯水蒸汽重整反应中的活性和稳定性,并通过X射线衍射(XRD),程序升温还原(H2-TPR)以及程序升温脱附(NH3-TPD)等方法对催化剂的性质进行表征.结果表明,Ni/MgO催化剂中的镍镁固溶体和Ni/y-Al2O3催化剂中的镍铝尖晶石的形成有利于提高催化剂的活性,而载体的酸性容易导致催化剂积碳而不利于催化剂的稳定性.     

助剂对镍基生物质焦油重整催化剂性能影响的研究进展

分别以碱及碱土金属、过渡金属以及稀土金属3种常见助剂类型,探讨了不同助剂对镍基催化剂催化生物质裂解及气化重整制氢催化活性、催化剂物化特性及催化剂失活特性的影响。添加碱金属组分后,生物质热解反应速率会大幅上升,生物质焦的水蒸气气化反应得到促进,并且达到最大热解速率所需的温度也有所降低,热解产物趋向于小分子量产物;过渡金属对生物质气化过程中生成焦油的催化裂解重整具有较好的催化活性;稀土元素对甲醇水蒸气重整等催化反应有着重要的作用,镍基催化剂中加入Ce和Pr能提高甲醇转化率、改善产气组分、提高H₂的选择性。结合国内外的研究情况发现钴、镧等金属助剂有利于提升镍基催化剂重整制氢活性,催化剂积炭及表面活性颗粒的聚集是造成催化剂失活的主要原因。     

Ni-Cu/蒙脱土乙醇水蒸气重整制氢催化剂性能研究

生物乙醇重整制氢是一种具有良好应用前景的制氢技术,是当前低碳能源领域的研究热点.本文采用离子交换法制备了Ni-Cu/蒙脱土双金属催化剂,并将其应用于乙醇水蒸气重整制氢.采用X射线衍射(XRD)、比表面积测定(BET)、H2-程序升温还原(H2-TPR)和透射电子显微镜(TEM)等表征手段对催化剂的物相结构、织构性质、还原性能、微观形貌等进行了研究.结果表明:Ni、Cu均为乙醇水蒸气重整制氢的活性组分,铜的加入可以减少镍颗粒的尺寸、优化镍组分的分布状态.此外,Ni-Cu双金属催化剂的双功能特性使其优于单一金属催化剂.Ni-Cu/蒙脱土在焙烧温度500℃、水醇比为8∶1、空速为80000 mL/gcat·h,反应进行10 h后,仍保持72.09％的氢气的选择性,说明Ni-Cu/蒙脱土双金属催化剂在乙醇水蒸气重整制氢中具有良好的催化活性和稳定性.     

金属／MgO上的乙醇水蒸气重整制氢

研究了氧化镁负载镍、铁、钴、锰、钼、铜和锡等金属催化剂在乙醇水蒸气重整反应的性能,结果表明在650℃,101．3kpa条件下,所有催化剂的活性都较高,乙醇接近完全转化,而对氢的选择性顺序为：Ni〉Co〉Sn〉Cu〉Fe〉Mo〉Mn。除镍的选择性是随温度上升之外,其他催化剂的选择性都随温度变化有个最佳值。镍催化剂的TPR和XRD表征表明,催化剂中存在3种形态的镍。     

Hydrogen Production by Steam Reforming of Ethanol on Potassium-Doped 12CaO · 7Al2O3 Catalyst

The performance of hydrogen production from steam reforming of ethanol were investigated by using the K-doped 12CaO · 7Al₂ O₃ catalyst (defined as C12A7–O⁻/x%K). The conversion of ethanol and hydrogen yield over C12A7–O⁻/x%K catalyst mainly depended on the temperature, K-doping amount, steam-to-carbon ratios (S/C) and contact time (W/F). In order to identify the catalyst’s characteristic and active species on the catalyst’s surface, Brunauer-Emmett-Teller (BET) surface area, CO₂ temperature programmed desorption (CO₂TPD), X-ray diffraction (XRD), Fourier transform infrared (FT–IR) and X-ray photoelectron spectroscopy (XPS) were carried out. Based on the characterization, it was found that active oxygen species and doped potassium play important roles in steam reforming of ethanol over C12A7–O⁻/27.3%K catalyst.     

Steam Reforming of Bio‐Oil for Hydrogen Production: Effect of Ni‐Co Bimetallic Catalysts

Various Ni‐Co bimetallic catalysts were prepared by incorporating sol‐gel and wet impregnation methods. A laboratory‐scale fixed‐bed reactor was employed to investigate their effects on hydrogen production from steam reforming of bio‐oil. The catalyst causes the condensation reaction of bio‐oil, which generates coke and inhibits the formation of gas at temperatures of 250 °C and 350 °C. At 450 °C and above the transformation of bio‐oil is initiated and gaseous products are generated. The catalyst also can promote the generation of H₂ as well as the transformation of CO and CH₄ and plays an active role in steam reforming of bio‐oil or gaseous products from bio‐oil pyrolysis. The developed 3Ni9Co/Ce‐Zr‐O catalyst achieved maximum hydrogen yield and lowest coke formation rate and provided a better stability than a commercial Ni‐based catalyst.     

Deactivation Studies of Rh/Ce0.8Zr0.2O2 Catalysts in Low Temperature Ethanol Steam Reforming

Rapid deactivation of Rh/Ce_0.8Zr_0.2O₂ catalysts during low temperature ethanol steam reforming was studied. A significant build-up of reaction intermediates, instead of carbon deposit, was observed at low reaction temperatures. This appears to be the cause of rapid catalyst deactivation. Co-feed experiments indicated that possible intermediate products acetone and ethylene caused more severe catalyst deactivation than other oxygenates such as acetic acid and acetaldehyde.     

The Effects of PdZn Crystallite Size on Methanol Steam Reforming

Exceptional activity and selectivity of Pd/ZnO catalysts for methanol steam reforming have been attributed to the formation of PdZn alloy. In this paper, we evaluated the crystallite size effects of PdZn alloy on methanol steam reforming. An organic preparation method was used to avoid the complexity from the alteration of ZnO morphology typically associated with the conventional aqueous preparation method. Both Pd loading and reduction temperature (>350 °C) were used to vary the crystallite size of PdZn alloy. Experimental activity studies and transmission electron microscope (TEM) characterizations indicated that formation of large sized PdZn crystallites exhibit high reactivity and low CO selectivity during methanol steam reforming.     

烃类蒸汽转化催化剂表面改性的研究

本文介绍了烃类蒸汽转化催化剂表面改性的试验, 经表面改性后, 在不降低催化剂原有低温还原性及强度等性能的基础上, 其样品的初活性及活性稳定性明显提高, 试验达到了预期的目的。     

甲醇水蒸气重整制氢催化剂性能的研究

研究共沉淀法制备Cu/Al2O3甲醇水蒸气重整制氢催化剂，考察催化剂组成和焙烧温度对催化剂性能的影响。结果表明当Cu质量分数为30．9％，焙烧温度为500℃时，催化剂性能最佳。并采用X射线衍射（XRD），程序升温还原（TPR）和热重分析等方法对催化剂表面性质进行探讨。     

复合载体Ni催化剂乙醇水蒸气重整制氢研究

用沉积-沉淀法制备了以ZnO为主要组分的多种复合载体（ZnO-Al2O3、ZnO-TiO2、ZnO-MgO、ZnO-CeO2、ZnO-ZrO2）Ni基催化剂,在固定床反应器上考查了催化剂的乙醇水蒸气重整制氢反应性能。结果表明,催化剂复合载体组分对乙醇水蒸气重整制氢性能有影响,其中,在较低温度（400～470℃）Ni/ZnO催化剂的催化性能最优,而在较高温度（485～550℃）Ni/ZnO-TiO2催化剂有相对最优的催化性能。催化剂的XRD、SEM等表征表明,Ni催化剂活性组分分散良好,催化剂颗粒大小较为均匀,同时也观察到使用后的催化剂表面有积炭生成。     

中低温乙醇水蒸气重整制氢的催化剂性能研究

本文用浸渍——热分解-氢还原法（IHDHR）制备了Ni／La2O3和Ni／Y2O3催化剂,采用固定床反应器对催化剂的催化性能进行实验测试。结果表明,催化剂对中低温乙醇水蒸气重整反应表现出较高的活性和稳定性。     

低镍/ZnO-TiO2催化剂的乙醇水蒸气重整制氢

为考察低镍负载量对乙醇水蒸气重整制氢催化剂性能的影响,利用沉积-沉淀法(DP)制备了镍负载最质量分率为0.5%～5.0%的Ni/ZnO-TiO2催化剂,并在内径14 mm的固定床管式反应器中对低镍催化剂进行了性能评价.结果表明,低镍/ZnO-TiO2催化剂具有较好的乙醇水蒸气重整制氢性能.在水醇物质的量比为13:1及反...     

Methanol Steam Reforming Over NiAl and Ni (M) Al Layered Double Hydroxides (M = Au, Rh, Ir) Derived Catalysts

This paper deals with an experimental investigation concerning steam reforming of methanol at 280, 340 and 380 °C over NiAl and Ni (Au, Rh or Ir)Al layered double hydroxides (LDHs) derived catalysts. Incorporation of noble metal ions into the NiAl-LDH framework was evidenced by XRD, TGA and TEM techniques. High selectivity to H₂ and CO₂ with less than 5% (volume) CO and trace CH₄ was observed over the NiAl-LDH catalyst. Whereas CO and H₂ are major products at lower temperatures after addition of Au, Rh and Ir to the NiAl-LDH system. They are significantly reduced with the concomitant increase in CH₄ and CO₂ as the temperature increased.