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91.
Influence of Support Type and Metal Loading in Methane Decomposition over Iron Catalyst for Hydrogen Production 下载免费PDF全文
Ahmed A. Ibrahim Ahmed S. Al‐Fatesh Wasim U. Khan Mostafa A. Soliman Raja L. AL Otaibi Anis H. Fakeeha 《中国化学会会志》2015,62(7):592-599
Natural gas resources, stimulate the method of catalytic methane decomposition. Hydrogen is a superb energy carrier and integral component of the present energy systems, while carbon nanotubes exhibit remarkable chemical and physical properties. The reaction was run at 700 °C in a fixed bed reactor. Catalyst calcination and reduction were done at 500 °C. MgO, TiO2 and Al2O3 supported catalysts were prepared using a co‐precipitation method. Catalysts of different iron loadings were characterized with BET, TGA, XRD, H2‐TPR and TEM. The catalyst characterization revealed the formation of multi‐walled nanotubes. Alternatively, time on stream tests of supported catalyst at 700 °C revealed the relative profiles of methane conversions increased as the %Fe loading was increased. Higher %Fe loadings decreased surface area of the catalyst. Iron catalyst supported with Al2O3 exhibited somewhat higher catalytic activity compared with MgO and TiO2 supported catalysts when above 35% Fe loading was used. CH4 conversion of 69% was obtained utilizing 60% Fe/Al2O3 catalyst. Alternatively, Fe/MgO catalysts gave the highest initial conversions when iron loading below 30% was employed. Indeed, catalysts with 15% Fe/MgO gave 63% conversion and good stability for 1 h time on stream. Inappropriateness of Fe/TiO2 catalysts in the catalytic methane decomposition was observed. 相似文献
92.
Ultra high performance liquid chromatography with mass spectrometry method for the simultaneous determination of phenolic constituents in honey from various floral sources using multiwalled carbon nanotubes as extraction sorbents 下载免费PDF全文
Saikh Mohammad Wabaidur Yacine Badjah Hadj Ahmed Munir Saeed Obbed Nasser Mohamed AL‐Harbi Turki Mohammad AL‐Turki 《Journal of separation science》2015,38(15):2597-2606
An ultra high performance liquid chromatography with mass spectrometry method has been developed for the simultaneous separation, identification and determination of 22 phenolic constituents in honey from various floral sources from Yemen. Solid‐phase extraction was used for extraction of the target phenolic constituents from honey samples, while multiwalled carbon nanotubes were used as solid‐phase adsorbent. The chromatographic separation of all phenolic constituents was performed on a BEH C18 column using a linear gradient elution with a binary mobile phase mixture of aqueous 0.1% formic acid and methanol. The quantitation was carried out in selected ion reaction monitoring acquisition mode. The total amount of phenolic acids, flavonoids and other phenols in each analyzed honey was found in the range of 338–3312, 122–5482 and 2.4–1342 μg/100 g of honey, respectively. 4‐Hydroxybenzoic acid was found to be the major phenolic acid. The main detected flavonoid was chrysin, while cinnamic acid was found to be the major other phenol compound. The regeneration of solid phase adsorbent to be reused and recovery results confirm that the proposed method could be potentially used for the routine analysis of phenolic constituents in honey extract. 相似文献
93.
Functionalized nanoparticles based solid‐phase membrane micro‐tip extraction and high‐performance liquid chromatography analyses of vitamin B complex in human plasma 下载免费PDF全文
Imran Ali Umma Kulsum Zeid A. AL‐Othman Abdulrahman Alwarthan Kishwar Saleem 《Journal of separation science》2016,39(14):2678-2688
Iron nanoparticles were prepared by a green method following functionalization using 1‐butyl‐3‐methylimidazolium bromide. 1‐Butyl‐3‐methylimidazole iron nanoparticles were characterized using FTIR spectroscopy, energy dispersive X‐ray fluorescence, X‐ray diffraction, scanning electron microscopy and transmission electron microscopy. The nanoparticles were used in solid‐phase membrane micro‐tip extraction to separate vitamin B complex from plasma before high‐performance liquid chromatography. The optimum conditions obtained were sorbent (15 mg), agitation time (30 min), pH (9.0), desorbing solvent [water (5 mL) + methanol (5 mL) + sodium hydroxide (0.1 N) + acetic acid (d = 1.05 kg/L, pH 5.5), desorbing volume (10 mL) and desorption time (30 min). The percentage recoveries of all the eight vitamin B complex were from 60 to 83%. A high‐performance liquid chromatography method was developed using a PhE column (250 × 4.6 mm, 5.0 μm) and water/acetonitrile (95:5, v/v; pH 4.0 with 0.1% formic acid) mobile phase. The flow rate was 1.0 mL/min with detection at 270 and 210 nm. The values of the capacity, separation and resolution factor were 0.57–39.47, 1.12–6.00 and 1.84–26.26, respectively. The developed sample preparation and chromatographic methods were fast, selective, inexpensive, economic and reproducible. The developed method can be applied for analyzing these drugs in biological and environmental matrices. 相似文献
94.
James D. Morrison Edward R. Grandbois Sachiko I. Howard Gary R. Weisman 《Tetrahedron letters》1981,22(28):2619-2622
Four chiral aminodiols from ring opening of ()-propylene oxide and ethylene oxide wiht n-butylamine and () or ()-α-methylbenzylamine were used to modify LiAlH4. Assymetric reduction of acetophenone and propiophenone gave the highest percent enantiomeric excess when the modifier was made from ()-oxide and ()-amine. 相似文献
95.
Two types of time resolved experiments have been performed on the intermediate sized polyatomic molecule diethylamine, in the liquid phase, in order to elucidate the pathway for vibrational relaxation of the ν = 3 level of the NH stretching mode, which has 9420 cm?1 of energy. Both techniques had calibrated absolute sensitivities and were specific for vibrational modes of ca. 3000 cm?1, yet with neither were transient populations in such modes observable. It is inferred that population relaxation in this highly excited room temperature system proceeds on the subpicosecond time scale to lower lying levels. The importance of intramolecular channels for this decay is suggested. 相似文献