Papers by Keyword: Catalyst Preparation

Abstract: High temperature water gas shift (HT-WGS) is an important catalytic process connected with reforming process in hydrogen production. Ni/CeO₂-Al₂O₃ (or Al₂O₃) catalysts were studied in this work on the effect of catalyst preparation method toward the physicochemical properties and the HT-WGS activity. Ni/CeO₂-Al₂O₃ were prepared by sol-gel and impregnation methods whereas Ni/Al₂O₃ was prepared by impregnation method. The catalyst samples were characterized by XRD, H₂-TPR and H₂-TPD techniques. The catalytic activities of HT-WGS catalysts was demonstrated at 550°C, GHSV of 2x10⁵ mLh^-1gcat^-1and steam-to-CO ratio of 3. Nickel was detected as a nickel aluminate phase in the calcined catalyst. Ni strongly interacted with support in the calcined catalyst prepared by sol-gel method. The strong metal-support interaction can be resisted by preparing catalyst via impregnation and CeO₂ can promote the H₂O dissociation in HT-WGS mechanism. The highest metal dispersion, largest metal surface area and greatest HT-WGS activity were consequently achieved by Ni/CeO₂-Al₂O₃ prepared from impregnation method.

Abstract: In the present studies, different characterization techniques have been utilized to evaluate the stability of catalysts prepared by modified impregnation method. The results indicated that strong metal-support (Mo-support) interaction existed in the γ-Al₂O₃-CeO₂ supported catalyst with higher CeO₂ loading as compared to the Mo/γ-Al₂O₃ catalyst. This suggested that the addition of CeO₂ into the γ-Al₂O₃ enhanced the metal-support interaction, thus decreases the reducibility, depending on the CeO₂ loading. Similarly, the catalyst with higher CeO₂ loading exhibited lower Ce 3d and higher Mo 3d binding energies respectively, supporting the TPR results.

Abstract: The effect of the chromium-magnesium precursor preparation techniques on physicochemical properties (BET surface area, total pore volume, mean pore diameter) and catalysts activity in the gas-phase hydrofluorination of perchloroethylene to pentafluoroethane (Freon 125) was studied. Kinetics of the catalytic reactions was studied for the most active catalyst. Based on the experimental data, the pathway of perchloroethylene fluorination with HF was suggested.

Abstract: Carbon nanospheres (CNSs) were synthesized from commercial activated carbons and cooking oil as carbon precursors using simple pyrolytic process and then were used as anode materials of lithium secondary batteries Prior to the synthesis of CNSs, a series of Fe catalysts supported on commercial activated carbons were prepared by two different methods, namely impregnations and adsorptions. The effect of preparation method on the characteristics of CNSs were then studied by scanning electron microscopy (SEM) , transmission electron microscope (TEM) and BET surface area measurements. Preliminary electrochemical measurements of as-synthesized CNTs were carried out using cyclic voltammetry instruments at constant scan rate to see the mechanism of Li-ion insertion and extraction into/from CNSs structures during cycle tests.

Abstract: An ammonia synthesis using magnetic field to replace Haber-Bosch’s ammonia production is great technological challenge in novel magnetized catalysts area. The carbon nanofiber supported iron catalyst was prepared by modifying carbon nanofiber support surface and later using urea to precipitate iron nitrate by deposition precipitation. It was found that the particle size was in a range of 5-50nm and well dispersion of iron was shown by transmission electron microscopy. This was strongly influenced by alteration of carbon nanofiber surface from hydrophobic to hydrophilic and with high adsorption sites as oxygen functional groups and defects. The lower iron loading between 5 and 40%wt, the lower iron accumulation and the narrower the particle size distribution of 10-20nm. The result suggests that the iron particles are in a good size range for iron catalyst activity for ammonia synthesis as reported by Morawski et.al and Figurski et.al authors.

Abstract: Here we report that ethylene-derived multi-walled carbon nanotubes (MWCNTs) can be successfully used in the “as prepared” form for the synthesis of Pt/MWCNTs catalysts in aqueous solutions without the need in special wetting agents or specific treatments. The MWCNTs strongly accelerate the hydrolysis of metal precursor, thereby allowing rapid deposition of Pt oxide under mild conditions. Upon reduction, Pt nanoparticles with uniform distribution over the carbon surface can be obtained, the particle size (2-5 nm) being dependent on BET surface area of MWCNTs (120-350 m²/g) and Pt loading (5-30 wt.% of Pt relative to MWCNTs).

Abstract: CuO/γ-Al2O3 catalysts were prepared by supercritical CO2 (SC-CO2) impregnation method. The preparation was carried out in SC-CO2 with Cu(NO3)2 as precursor, methanol as assistant solvent, and γ-Al2O3 as support. The effects of impregnation parameters such as temperature and pressure of SC-CO2, impregnation time, ratio of precursor to support, and amount of assistant solvent on catalyst preparation were investigated. The as-prepared catalysts were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis and compared to that prepared by the conventional impregnation method. The SC-CO2 impregnation method provided higher adsorption rate, larger adsorption quantity, more homogeneous dispersion of precursor, and stronger interaction between precursor and support. The catalytic degradation of methylene blue (MB) was used as probe reaction to estimate the catalytic activity of two catalysts prepared by two methods. The catalyst prepared by SC-CO2 impregnation method exhibits significantly improved catalytic activity. These results show that the inorganic metallic reagents as precursor with assistant solvent can be used as an alternative for the organometallic precursors in SC-CO2 impregnation method.

Abstract: Ce-Y-palygorskite catalysts were prepared by chemical blending method. The effect of preparation conditions on catalytic performance of Ce-Y-palygorskite catalyst for NO decomposition was investigated in a fixed bed flow reactor. The characteristics of the Ce-Y-palygorskite catalysts were studied by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The obtained results provided substantial evidence that the catalysts preparation conditions would have strong effect on the catalytic activity for NO decomposition. The Ce-Y-palygorskite catalyst prepared under the optimal conditions: rare earth content, Ce/Y, pH value of the chemical blending and calcination treatment temperature was 3%, Ce_xY_(1-x)(x=0.9), 7 and 350°C, respectively, was identified as the most active catalyst for the NO decomposition, and the denitration rate could be up to 67.3% under the experimental reaction conditions.

Abstract: In this work the method of single-wall carbon nanotube synthesis based on chemical vapor deposition from ethanol vapor has been developed. The films grown have been characterized in detail by the electron microscopy and the Raman scattering techniques. A typical split tangential mode (at 1592 cm-1) and a number of "breathing" modes (150-270 cm-1) have been revealed in the Raman spectra for a variety of synthesis regimes. It was possible to change the geometrical parameters of nanotubes by playing with the synthesis conditions. A key role of the catalyst (Co, Co:Mo) preparation has been revealed. A special procedure of the catalyst crystal growth has been developed.