Sep 2013, Volume 7 Issue 3

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    Elena Yu. KONYSHEVA

    Reduction behavior of pure and doped CeO2, the multi-phase La0.6Sr0.4CoO3?xCeO2, La0.8Sr0.2MnO3 ?xCeO2, and La0.95Ni0.6Fe0.4O3?xCeO2 composites, was studied under hydrogen containing atmosphere to address issues related to the improvement of electrochemical and catalytic performance of electrodes in fuel cells. The enhanced reduction of cerium oxide was observed initially at 800°C in all composites in spite of the presence of highly reducible transition metal cations that could lead to the increase in surface concentration of oxygen vacancies and generation of the electron enriched surface. Due to continuous reduction of cerium oxide in La0.6Sr0.4CoO3?xCeO2 and La0.8Sr0.2MnO3?xCeO2 (up to 10 h) composites the redox activity of the Ce4+/Ce3+ pair could be suppressed and additional measures are required for reversible spontaneous regeneration of Ce4+. After 3 h exposure to H2-Ar at 800°C the reduction of cerium oxides and perovskite phases in La0.95Ni0.6Fe0.4O3?xCeO2 composites was diminished. The extent of cerium oxide involvement in the reduction process varies with time, and depends on its initial deviation from oxygen stoichiometry (that results in the larger lattice parameter and the longer pathway for O2- transport through the fluorite lattice), chemical origin of transition metal cations in the perovskite, and phase diversity in multi-phase composites.

    Alan J. McCue, Jura Aponaviciute, Richard P.K. Wells, James A. Anderson

    The addition of Au as a promoter/modifier for alumina supported Co catalyst has been studied by combined in-situ high temperature, high pressure Fourier transform infrared (FTIR) and on-line gas chromatography. The combination of these tools permitted the state of the active catalyst surface to be monitored while following the elution of reaction products during the first 5–7 h on stream of the catalyst. The catalysts under study were a 10%Co/Al2O3 and a 2.5%Au/10%Co/Al2O3. Samples were characterised before use using Raman and temperature programmed reduction (TPR). During the initial stages of reaction, hydrocarbons were built up on the surface of the catalyst as monitored by FTIR and the nature and amount of these species were assessed in terms of CH2/CH3 ratio and the density of these alkyl fragments by employing absorption coefficients for the individual components. The nature and reducibility of the Co particles were modified by the presence of Au while the later also shifted the CO/H2 balance by acting as an effective water-gas shift catalyst during the early stages of reaction. This characteristic was lost during reaction as a consequence of redistribution of the two metallic phases.

    Ruixue GU, Guangming ZENG, Jingjing SHAO, Yuan LIU, Johannes W. Schwank, Yongdan LI

    A macro-meso-porous monolithic Ni-based catalyst was prepared via an impregnation route using polystyrene foam as the template and then used in the steam reforming of ethanol to produce a H2-rich gas. The Ni/Mg-Al catalyst has a hierarchically macro-meso-porous structure as indicated by photographs and scanning electron microscopy (SEM). The surface area of the catalyst was 230 m2?g-1 and the Ni dispersion was 5.62%. Compared to the pelletized sample that was prepared without a template, the macro-meso-porous Ni/Mg-Al monolith exhibited superior reactivity in terms of H2 production and also had lower CH4 yields at 700oC and 800oC. Furthermore, the monolithic catalyst maintained excellent activity and H2 selectivity after 100-h on-stream at 700oC, as well as good resistance to coking and metal sintering.


    A two-step process was employed to convert methane or ethane to light olefins via the formation of an intermediate monoalkyl halide. A novel K4RuOCl10/TiO2 catalyst was tested for the oxidative chlorination of methane and ethane. The catalyst had high selectivity for methyl and ethyl chlorides, 80% and 90%, respectively. During the oxychlorination of ethane at T≥250°C, the formation of ethylene as a reaction product along with ethyl chloride was observed. In situ Fourier transform infrared studies showed that the key intermediate for monoalkyl chloride and ethylene formation is the alkoxy group. The reaction mechanism for the oxidative chlorination of methane and ethane over the Ru-oxychloride catalyst was proposed. The novel fiber glass catalyst was also tested for the dehydrochlorination of alkyl chlorides to ethylene and propylene. Very high selectivities (up to 94%–98%) for ethylene and propylene formation as well as high stability were demonstrated.

    Piyawat PUE-ON, Vissanu MEEYOO, Thirasak RIRKSOMBOOON

    Methane partial oxidation (MPO) is considered as an alternative method to produce hydrogen because it is an exothermic reaction to afford a suitable H2/CO ratio of 2. However, carbon deposition on a catalyst is observed as a major cause of catalyst deactivation in MPO. In order to find suitable catalysts that prevent the carbon deposition, NiO-MgO/Ce0.75Zr0.25O2 (CZO) supported catalysts were prepared via the co-impregnation (C) and sequential incipient wetness impregnation (S) methods. The amount of Ni loading was fixed at 15 wt-% whereas the amount of MgO loading was varied from 5 to 15 wt-%. The results revealed that the addition of MgO shifted the light-off temperatures to higher temperatures. This is because the Ni surface was partially covered with MgO, and the strong interaction between NiO and NiMgO2 over CZO support led to the difficulty in reducing NiO to active Ni0 and thus less catalytic activity. However, among the catalysts tested, the 15Ni5Mg/CZO (S) catalyst exhibited the best catalytic stability for MPO after 18 h on stream at 750°C. Moreover, this catalyst had a better resistance to carbon deposition due to its high metallic Ni dispersion at high temperature.

    Qiang XIAO, Xiaodan TANG, Yefeng LIU, Yijun ZHONG, Weidong ZHU

    A comparison study has been conducted on the strategies for synthesizing nanocrystalline Li2ZrO3 and K-doped Li2ZrO3 absorbents for CO2 capture at high temperatures, including solid-state and liquid-phase methods, citrate route, and starch-assisted sol-gel method combined with freeze-drying technique. The absorption properties, including uptake rate and absorption capacity, of synthesized absorbents were investigated by thermogravimetric analysis (TGA) at different CO2 partial pressures. The nanosized Li2ZrO3 crystals synthesized by the citrate route exhibit a faster uptake and a higher, nearly stoichiometric absorption capacity than those synthesized by the solid-state and liquid-phase methods. The doping of K into Li2ZrO3 can significantly improve the uptake rate of CO2, especially at low CO2 partial pressures. For the synthesis of K-doped Li2ZrO3, the citrate route has poor reproducibility and scalability, whereas the starch-assisted sol-gel method combined with freeze-drying technique is reproducible and easily scaled up, and the thus synthesized absorbents possess excellent CO2 capture properties.

    Hua ZHANG, Hongji ZHU, Shipeng WANG, Weihua WANG

    Response surface method (RSM), based on Box-Behnken design, was used to optimize the enzymatic hydrolysis conditions of flatfish skin protein hydrolysates (FSPH). Among the tested proteases, the combination of nutrase and trypsin was selected. The optimal hydrolysis conditions were as follows: pH 7.3, temperature 51.8°C, and the enzyme/substrate (E/S) ratio 2.5; under these conditions, the maximum peptide yield (PY) was 69.41±0.43%. The physiochemical analysis showed that the amino acids (His, Asp and Glu) of FSPH accounted for 18.15%, and FSPH was a mixture of polypeptides mostly distributed among 900–2000 Da. FSPH could exhibit a 93% chelating effect on ferrous ion at a concentration of 400 μg/mL, and also a notable reducing power. This study showed bioprocess for the production of FSPH for the first time, which had a good potential for valuable ingredients in the food, cosmetic and medicine industries.

    Gautam SEN, G. Usha RANI, Sumit MISHRA

    Poly(2-hydroxyethylmethacrylate) chains were grafted onto the backbone of agar using a microwave assisted method involving a combination of microwave irradiation and ceric ammonium nitrate to initiate the grafting reaction. The synthesized graft copolymers were characterized by intrinsic viscosity measurements, Fourier transform infrared spectroscopy, elemental analysis (C, H, N, O and S) and scanning electron microscopy. Ag-g-P(HEMA)-2 showed a much higher flocculation efficacy than agar. The optimized dosage of flocculation for Ag-g-P(HEMA)-2 in the wastewater was found to be 0.75 ppm. Compared to agar, Ag-g-P(HEMA)-2 was found to considerably reduce the pollutant load in the wastewater.

    Liang ZHU, Jingkang WANG

    A simple and direct method without a derivation step for routine analysis of tobramycin has been developed. This method used reversed-phase ion-pair high performance liquid chromatography (HPLC) with a refractive index (RI) detector and a C18 column which is stable at pH above 1.00. The presence of 4.50 mg·mL-1 trifluoroacetic acid (TFA) in the mobile phase improved the protonation of tobramycin and the formation of ion-pairs, and thus reduced its hydrophility. This unique separation–detection combination showed good linearity with correlation coefficients 0.9996 in the concentration range of 0.25–2.50 mg·mL-1. The quantitation limit and detection limit were determined to be 0.23 mg·mL-1 and 0.071 mg·mL-1, respectively. Tobramycin was recovered in 98.00%, 98.84% and 99.64% for tobramycin solutions at concentrations of 2.25 mg·mL-1, 1.50 mg·mL-1 and 0.75 mg·mL-1, respectively. The relative standard deviations for six spiked samples ranged from 0.20% to 2.40%, indicating a good reproducibility of this method.

    M. S. Shalaby, H. Abdallah

    With the hope of overcoming the generation of hazardous materials to human health and environment, serious and great endeavor have been made in catalyst fabrication using green chemistry technology. In this paper, the manganese (III) acetylacetonate nanoparticles with diameters of about 146 nm were prepared by a simple and environmentally benign route based on hydrolysis of KMnO4 followed by reaction with acetylacetone in rapid stirring rate or ultrasonication. The as-prepared samples were characterized by X-ray diffraction, energy dispersive X-ray fluorescence (EDIX), Fourier transfer infrared spectroscopy and scanning electron microscope. Various parameters were investigated, and the pure and stable crystals of manganese (III) acetylacetonate could be obtained in 98% conversion at a molar ratio 7∶1 of acetylacetone to KMnO4 and 75°C after 60 min. We further proposed a mathematical model, and the predicted results from model were in good agreement with experimental results.

    Li XU, Zhi GUO, Lishun DU

    This work was conducted to study the ability of anodic oxidation of azo dye C.I. Acid Red 73 (AR73) using the yttrium-doped Ti/SnO2-Sb electrodes. The effects of Sb doping level, yttrium doping level, thermal decomposition temperature and cycle times of dip-coating thermal decomposition on the properties of the electrodes were investigated. The results showed that the excellent electrochemical activity of Ti/SnO2-Sb-Y electrode can be achieved at a 7∶1 molar ratio of Sn∶Sb and thermal decomposition temperature of 550°C. Moreover when the cycle times of dip-coating and thermal decomposition were up to 10 times, the performance of the electrode tends to be stable. The Ti/SnO2-Sb electrodes doped with yttrium (0.5 mol-%) showed the most excellent electrochemical activity. In addition, the influences of operating variables, including current density, initial pH, dye concentration and support electrolyte, on the colour removal, chemical oxygen demand (COD) removal and current efficiency were also investigated. Our results confirmed that the current efficiency increased with the concentrations of dye and sodium chloride. Moreover, increasing the current density and the initial pH would reduce the current efficiency.

    Zhikai LI, Zhangfeng QIN, Yagang ZHANG, Zhiwei WU, Hui WANG, Shuna LI, Mei DONG, Weibin FAN, Jianguo WANG

    The control system of a catalytic flow reversal reactor (CFRR) for the mitigation of ventilation air methane was investigated. A one-dimensional heterogeneous model with a logic-based controller was applied to simulate the CFRR. The simulation results indicated that the controller developed in this work performs well under normal conditions. Air dilution and auxiliary methane injection are effective to avoid the catalyst overheating and reaction extinction caused by prolonged rich and lean feed conditions, respectively. In contrast, the reactor is prone to lose control by adjusting the switching time solely. Air dilution exhibits the effects of two contradictory aspects on the operation of CFRR, i.e., cooling the bed and accumulating heat, though the former is in general more prominent. Lowering the reference temperature for flow reversal can decrease the bed temperature and benefit stable operation under rich methane feed condition.

    J. Sargolzaei, A. Hedayati Moghaddam

    Various simulation tools were used to develop an effective intelligent system to predict the effects of temperature and pressure on an oil extraction yield. Pomegranate oil was extracted using a supercritical CO2 (SC-CO2) process. Several simulation systems including a back-propagation neural network (BPNN), a radial basis function neural network (RBFNN) and an adaptive-network-based fuzzy inference system (ANFIS) were tested and their results were compared to determine the best predictive model. The performance of these networks was evaluated using the coefficient of determination (R2) and the mean square error (MSE). The best correlation between the predicted and the experimental data was achieved using the BPNN method with an R2 of 0.9948.

    A. A. Olajire

    The clean development mechanism (CDM) of the Kyoto Protocol offers developing countries the opportunity to participate in the effort to reduce global greenhouse gas levels and also benefit from sustainable development opportunities. To date, the majority of CDM investments have gone to emerging markets such as China, India, Brazil, and Mexico, while developing countries such as Nigeria have largely been absent from the program. Chemical sequestration using aqueous ammonia process (AAP) offers a clean low carbon technology for the efficient conversion of captured CO2 into clean CO2 which could be injected into oil field for enhanced oil recovery or as fertilizer source. CDM-CCS (carbon capture and storage) project with AAP has the potential as intervention for leveraging sustainable livelihood development (organic fertilizer for food production) as well as for tackling local (land air and water) and global pollution (reduce methane, SOx and NOx emissions).