LiCoO2-based catalysts for generation of hydrogen gas from sodium borohydride solutions

The catalytic performance of lithium cobaltite, LiCoO₂, in sodium borohydride hydrolysis has been studied and compared with catalytic properties of Co₃O₄, CoCl₂ and Co(NO₃)₂. Activation times and observed H₂ generation rates were found dependent on the chemical nature and dispersion of the catalysts, as well as on the reaction temperature. The magnetic susceptibility method was used to demonstrate that all studied cobalt compounds, including cobalt oxides and soluble salts, are being reduced under catalytic conditions to form catalytically active cobalt boride phases. Impregnating LiCoO₂ with Pt and Rh chlorides increases only the initial catalytic activity, which then quickly declines during cyclic stability tests and in just a few cycles approaches that of the starting LiCoO₂ material.     

Preparation of porous PVDF-NiB capsules as catalytic adsorbents for hydrogen generation from sodium borohydride

Porous poly(vinylidene fluoride) (PVDF)-NiB capsules were prepared by phase inversion of PVDF, nickel salt and sodium borohydride (NaBH₄) mixtures in water. During the process, nickel salt was reduced to NiB particles by NaBH₄, and the excess NaBH₄ was hydrolyzed to produce hydrogen gas bubbles which aided the formation of the large holes inside the porous capsules. It was proved that the porous capsules can adsorb about 33 wt.% NaBH₄ in THF/NaBH₄ solution for about 4 h. Most of NiB particles were attached on the surface of the porous capsules with inside holes according to the observation of scanning electron microscopy (SEM) and EDS. The special structure of the capsules was successfully used as catalysts and container simultaneously for hydrogen production via catalytic hydrolysis of NaBH₄ in aqueous solution.     

Effects of electrodeposited Co and Co–P catalysts on the hydrogen generation properties from hydrolysis of alkaline sodium borohydride solution

Co and Co–P catalysts electroplated on Cu in sulfate based solution without or with an addition of H₂PO₂⁻ ions were developed for hydrogen generation from alkaline NaBH₄ solution. The microstructures of the Co and Co–P catalysts and their hydrogen generation properties were analyzed as a function of cathodic current density and plating time during the electrodeposition. An amorphous Co–P electrodeposit with micro-cracks was formed by electroplating in the sulfate based solution containing H₂PO₂⁻ ions. It was found that the amorphous Co–P catalyst formed at 0.01 A/cm² exhibited 18 times higher catalytic activity for hydrolysis of NaBH₄ than did the polycrystalline Co catalyst. The catalytic activity of the electrodeposited Co–P catalyst for hydrolysis of NaBH₄ was found to be a function of both cathodic current density and plating time, that is, parameters determining the concentration of P in the Co–P catalyst. Especially, Co–13 at.% P catalyst electroplated on Cu in the Co–P bath at a cathodic current density of 0.01 A/cm² for 1080 s showed the best hydrogen generation rate of 954 ml/min g-catalyst in 1 wt.% NaOH + 10 wt.% NaBH₄ solution at 30 °C.     

Investigation on modification of Ru/CNTs catalyst for the generation of COx-free hydrogen from ammonia

The modification of Ru/CNTs (CNTs denotes carbon nanotubes) with rare earth, alkali, and alkaline earth compounds were systematically studied. The loading of modifying agents leads to decrease in pore volume and surface area; but improvement in thermal stability of Ru/CNTs. The size and morphology of Ru particles are not affected by the modification. For the catalysts modified by metal nitrates, activities were found in the order of K–Ru>Na–Ru>Li–Ru>Ce–Ru>Ba–Ru>La–Ru>Ca–Ru>Ru, signifying that within the same groups (K, Na and Li; Ba and Ca), the higher the electronegativity of the promoter, the lower is the NH₃ conversion. Of all the potassium salts adopted, KNO₃, KOH, and KCO₃ show similar promotional effect, suggesting that KOH is the active promoter for catalytic activity. The maximum promotional effect was observed at an atomic ratio of K/Ru=2. The electron-withdrawing groups, F⁻¹, Cl⁻¹, Br⁻¹, SO₄²⁻, and PO₄³⁻ are inhibitors of Ru catalysts. The results of N₂-TPD investigation revealed that the promotional effects of a modifier is a combined result of: (i) enhancing combinative desorption of nitrogen atoms, and (ii) decreasing of the apparent activation energy of the decomposition reaction.     

硼氢化钾水解制氢双金属催化剂研究

实验制备了活性炭(AC)负载钴-镍基双金属催化剂,利用XRD对其进行表征。实验研究了不同催化剂、反应温度和硼氢化钾浓度等因素对制氢反应的影响。研究结果显示,10%(wt)Co-Ni/AC催化剂中,金属钴的比例越大,催化剂的活性越好。反应温度对反应速率有很大影响。硼氢化钾浓度对产氢率有一定影响。     

Electrochemical oxidation of boron containing compounds on titanium carbide and its implications to direct fuel cells

Electrochemical oxidation of sodium borohydride (NaBH₄) and ammonia borane (NH₃BH₃) (AB) have been studied on titanium carbide electrode. The oxidation is followed by using cyclic voltammetry, chronoamperometry and polarization measurements. A fuel cell with TiC as anode and 40 wt% Pt/C as cathode is constructed and the polarization behaviour is studied with NaBH₄ as anodic fuel and hydrogen peroxide as catholyte. A maximum power density of 65 mW cm⁻² at a load current density of 83 mA cm⁻² is obtained at 343 K in the case of borhydride-based fuel cell and a value of 85 mW cm⁻² at 105 mA cm⁻² is obtained in the case of AB-based fuel cell at 353 K.     

From soil to lab: Utilization of clays as catalyst supports in hydrogen generation from sodium borohydride fuel

The stabilized aqueous solution of sodium borohydride NaBH₄ is a promising hydrogen fuel but the stored hydrogen has to be released with the help of a catalyst through hydrolysis. In the present study, we developed Co- and clay-based supported catalysts. Three raw clays were taken from soil in Lebanon. Once purified and annealed, they were used as supports. Two of them, mainly composed of kaolinite and illite respectively, showed to be promising owing to their attractive specific surface areas (58.0 and 67.1 m² g⁻¹) as well as the high reactivity of the corresponding 15 wt.% Co catalysts (i.e. NaBH₄ conversions of 100% and hydrogen generation rates up to ∼31 L(H₂) min⁻¹ g⁻¹(Co)). A kinetic study was also carried out. The main results are reported and discussed herein.     

Steam reforming of ethanol over Ni/support catalysts for generation of hydrogen for fuel cell applications

The paper reports experimental results concerning the influence of the support nature (TiO₂, ZnO, Al₂O₃ and Al₂O₃–Fe₂O₃) of nickel catalysts on their activity, selectivity and coking phenomenon in the steam reforming of ethanol in the range of 570–870 K. The chemical transformations of ethanol occurring on the catalyst support make its chemical nature an important factor affecting the productivity and selectivity of the process. It was found that the most suitable supports in nickel catalysts designed for hydrogen generation in the steam reforming of ethanol are ZnO and TiO₂. Taking into consideration both the efficiency of hydrogen generation and the intensity of carbon deposition, the optimum temperature of the process of the steam reforming of ethanol is below 750 K. An improvement in the selectivity of hydrogen generation and diminishing of the formation of undesirable products may be obtained by promoting nickel catalysts with sodium.     

NaBH4溶液催化制氢的阴离子效应研究

研究了Cl-和NO3-阴离子对NaBH4溶液现场制氢反应的影响,发现在制氢反应过程中存在着生成金属硼化物和生成金属氢氧化物的竞争反应.当溶液中阴离子为Cl-时,金属离子在催化NaBH4溶液制氢反应时将与硼结合,促使其活化为高活性金属硼化物,能有效促进制氢反应;当溶液中的阴离子为NO3-时,将诱导金属离子生成没有催化活性的金属氢氧化物,抑制制氢反应.     

随车制氢甲醇裂解催化剂的研究进展

综述了随车制氢甲醇裂解催化剂最新的研究进展,对镍系、贵金属系和铜系催化剂等作了评述。同时指出了铜水泥催化剂应用在随车制氢系统里的优势,并对今后的研究方向做了展望。     

氨合成催化剂研究进展

介绍了氨合成催化剂研究开发进展情况。重点介绍了新型助剂的开发及其加入方式,催化剂母体体系的改进,球形及钌系氨合成催化剂的研制开发情况等。     

乙腈加氢制乙胺的催化剂性能研究

以乙腈和氢气为原料,在过量氨和催化剂的作用下,进行催化反应合成乙胺,考察各种组分加氢催化剂对反应结果的影响,根据最终测试结果选择镍为主催化剂,加入镧为助催化剂,以γ-Al2O3为载体,采用浸渍法制备催化剂,转化率可达到93.16％,总收率达到92.99％,选择性为98.95％.     

硼氢化钠水解制氢用铂基催化剂的研究

选用2种高比表面的碳载体,采用浸渍法制备了担载量为20%的铂基催化剂.经表征20%Pt/乙炔黑的孔径主要分布在2.5～5nm之间,孔径小并且分布集中;而20%Pt/珍珠碳的孔径除少量分布在2.5～5 nm之间外,大部分孔径分布在20～60nm,分布范围较宽.在20min内,20% Pt/珍珠碳和20%Pt/乙炔黑的平均制氢速率分别为1.9 L/min和2.3 L/min,当氢的利用率为100%时,可分别为功率为308W和373 W的质子交换膜燃烧电池持续供氢.     

Catalytic synthesis of methanethiol from hydrogen sulfide and carbon monoxide over vanadium-based catalysts

The direct synthesis of methanethiol, CH₃SH, from CO and H₂S was investigated using sulfided vanadium catalysts based on TiO₂ and Al₂O₃. These catalysts yield high activity and selectivity to methanethiol at an optimized temperature of 615 K. Carbonyl sulfide and hydrogen are predominant products below 615 K, whereas above this temperature methane becomes the preferred product. Methanethiol is formed by hydrogenation of COS, via surface thioformic acid and methylthiolate intermediates. Water produced in this reaction step is rapidly converted into CO₂ and H₂S by COS hydrolysis.

Titania was found to be a good catalyst for methanethiol formation. The effect of vanadium addition was to increase CO and H₂S conversion at the expense of methanethiol selectivity. High activities and selectivities to methanethiol were obtained using a sulfided vanadium catalyst supported on Al₂O₃. The TiO₂, V₂O₅/TiO₂ and V₂O₅/Al₂O₃ catalysts have been characterized by temperature programmed sulfidation (TPS). TPS profiles suggest a role of V₂O₅ in the sulfur exchange reactions taking place in the reaction network of H₂S and CO.     

Effect of support on hydrogen production by auto-thermal reforming of ethanol over supported nickel catalysts

Nickel catalysts supported on various supports such as ZnO, MgO, ZrO₂, TiO₂, and Al₂O₃ were prepared by an impregnation method to investigate the effect of support on catalytic performance in hydrogen production by auto-thermal reforming of ethanol. Among the supported catalysts, the Ni/ZrO₂ and Ni/TiO₂ catalysts showed better catalytic performance than the other catalysts. The electronic structure of nickel species supported on ZrO₂ and TiO₂ was favorably modified for the reaction, and thus, the reducibility of nickel species supported on ZrO₂ and TiO₂ was increased due to the weak interaction between nickel and support. On the other hand, the Ni/MgO and Ni/ZnO catalysts exhibited poor catalytic performance in the auto-thermal reforming of ethanol due to the formation of a solid solution phase.     

Detoxication of water containing 1,1-dimethylhydrazine by catalytic oxidation with dioxygen and hydrogen peroxide over Cu- and Fe-containing catalysts

A number of Cu- and Fe-hydroxide containing catalysts, supported on oxide carriers, were prepared to provide the removal of 1,1-dimethylhydrazine from aqueous solutions via its oxidation by hydrogen peroxide and air oxygen. The Cu-containing samples as well as Fe/ZSM-5 are the most active catalysts in this reaction. The reaction products were analyzed by gas chromatography and UV–Vis spectroscopy. The effect of nature of the oxidizer and catalyst, pH and temperature on both the reaction rate and product composition was studied.     

Combined pre-reforming-desulfurization of high-sulfur fuels for distributed hydrogen applications

A major challenge facing the future Hydrogen Economy is the issue of hydrogen fuel delivery and distribution. In the near term, it may be necessary to deliver high-density hydrocarbon fuels (e.g., diesel fuel) directly to the end-user (e.g., a fueling station) wherein it is reformed to hydrogen, on demand. This approach has the advantages of utilizing the existing fuel delivery infrastructure, and the fact that more energy can be delivered per trip when the tanker is filled with diesel instead of liquefied or compressed hydrogen gas. Reforming high-sulfur hydrocarbon fuels (e.g., diesel, JP-8, etc.) is particularly challenging due to rapid deactivation of conventional reforming catalysts by sulfurous compounds. A new on-demand hydrogen production technology for distributed hydrogen production is reported. In this process, first, the diesel fuel is catalytically pre-reformed to shorter chain hydrocarbons (C₁-C₆) before being fed to the steam reformer, where it is converted to syngas and further to high-purity hydrogen gas. In the pre-reformer, most sulfurous species present in the fuel are converted to H₂S. Desulfurization of the pre-reformate gas is carried out in a special regenerative redox system, which includes an iron-based scrubber coupled with an electrolyzer. The integrated pre-reformer and sulfur-scrubbing unit operated successfully for 100 h at desulfurization efficiency of greater than 95%.     

抽氢气及合成气工艺在合成氨装置的应用

介绍了抽氢气、合成气装置的工艺路线,技术特点,运行情况。该工艺在30万t／a年合成氨装置上的应用为国内首创,7．0MPa甲烷化工艺的工业化应用亦为国内首创。