Institutional Repository of GuangZhou Institute of Energy Conversion, CAS

    Experimental study on the kinetic effect of N-butyl-N-methylpyrrolidinium bromide on CO2 hydrate

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    The kinetic effects of N-butyl-N-methylpyrrolidinium bromide ([Py14]-Br) on the formation of CO2 gas hydrates were experimentally investigated. Both of the induction time of CO2 hydrates formation and the formation rates were investigated in the aqueous solutions of [Py14]-Br at different concentrations. Pressure and temperature changes versus time during the hydrate formation process were measured under the isochoric conditions. The induction time had a trend to decrease with the increase of initial pressure or subcooling. [Py14]-Br aqueous solution could delay the induction time compared with pure water system at relatively high subcooling, while it appeared to have no inhibition effect at low subcooling, even enhanced the formation of gas hydrates. It was interesting to find that [Py14]-Br at a low mass fraction could slow the formation rate of CO2 gas hydrate, while it had a promotion effect at high mass fraction. The same promotion effect was also found by PVP at the mass fraction of 2.0%. So [Py14]-Br not only acted as kinetic inhibitor but also promoter of CO2 gas hydrate under different situations. (C) 2016 Elsevier B.V. All rights reserved

    Analysis on geologic conditions affecting the performance of gas production from hydrate deposits

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    Potential of gas production from hydrate deposits depends on occurrence features of the hydrate deposits and production methods, and fundamentally it is determined by geologic conditions of the hydrate reservoir. The geologic conditions mainly include reservoir porosity (Phi), hydrate saturation (S-H), formation permeability (K), thickness of hydrate-bearing layer (HBL) (H), initial pressure (P-0) and temperature (T-0) of the HBL. Profound differences of the conditions have been revealed by the global marine drilling programs. Orthogonal design, as a statistic method, is employed in this work to systematically investigate the relative importance of these diverse geologic conditions on hydrate decomposition as well as production performance of gas and water from the Class 2 offshore hydrate accumulations. The analysis results show that the order of the significance levels of the geologic conditions on cumulative gas production is K > Phi> S-H > T-0> P-0> H; while the order of that on the water-to-gas ratio is P-0>K>Phi>S-H>H>T-0. The results suggest that it is favorable for production from the hydrate deposits characterized by the conditions of the high permeability, moderate porosity (40%), moderate-to-high hydrate saturation (38%-67%) and the low initial pressure (10.79-13.38 MPa). This research gives a forward sight for production prediction and provides a reference in selection of production target. (C) 2016 Elsevier Ltd. All rights reserved

    A new approach of microalgal biomass pretreatment using deep eutectic solvents for enhanced lipid recovery for biodiesel production

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    The biomass of Chlorella sp. was pretreated with three different aqueous deep eutectic solvents (aDESs), i.e. aqueous choline chloride-oxalic acid (aCh-O), aqueous choline chloride-ethylene glycol (aCh-EG) and aqueous urea-acetamide (aU-A). The effect of aDESs pretreatment of microalgae biomass was evaluated in terms of lipid recovery rate, total carbohydrate content, fatty acid composition, and thermal chemical behavior of biomass. Results indicated that, lipid recovery rate was increased from 52.03% of untreated biomass to 80.90%, 66.92%, and 75.26% of the biomass treated by aCh-O, aCh-EG and aU-A, respectively. However, there were no major changes observed in fatty acid profiles of both untreated and treated biomass, specifically palmitic acid, palmitoleic acid and stearic acid under various pretreatments. Furthermore, characterizations of untreated and treated biomass were carried out using Fourier transform infrared (FTIR), thermogravimetry analysis (TGA) and scanning electron microscope (SEM) to understand the enhanced lipids recovery. (C) 2016 Published by Elsevier Ltd

    Effect of the temperature on the dissolution of corn straw in ethanol solution

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    Lgnocellulosic biomass is undissolvable in water and conventional solvents for its complex natural recalcitrance, which significantly hinders its efficient utilization. Herein, we provided an efficient process for the dissolution of corn straw under mild conditions with the solution of ethanol, H2SO4, H2O2 and H2O. The research emphasis is the effect of temperature on the dissolution process. Results showed that the components of cellulose, hemicellulose and lignin can be separated from the corn straw by adjusting the dissolution temperature. Part of the dissolved cellulose and hemicellulose were further converted into sugars and chemicals (such as furfural, 5-hydroymethylfurfural, ethyl levulinate, levulinic acid) during the dissolution process. Released lignin was destroyed into fragments and was recovered as organosolv lignin with lower molecular weight. Furthermore, residues and the recovered lignin obtained at different dissolution temperature were characterized carefully by FTIR, NMR, GPC and elemental analysis and the dissolution mechanism was discussed

    Optical properties and possible sources of brown carbon in PM2.5 over Xi'an, China

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    To quantify optical and chemical properties of PM2.5 brown carbon (BrC) in Xi'an, 58 high-volume ambient PM2.5 samples were collected during 2 November 2009 to 13 October 2010. Mass concentrations of chemical components were determined, including water-soluble ions, water-soluble organic carbon, levoglucosan, organic carbon (OC), and element carbon (EC). BrC, as an unidentified and wavelength-dependent organic compound, was also measured from water-soluble carbon (WSOC) at 340 nm using UV-vis spectrometer. The wavelength-dependent absorption coefficient (b(abs)) and mass absorption coefficient (MAC) were much abundant at 340 nm, and the high Absorption Angstrom coefficient (AAC) values were observed around 5.4, corresponding to the existence of BrC in ambient PM2.5, especially in winter. Good correlations (R > 0.60) between b(abs) and biomass burning markers, such as levoglucosan and K+, in winter indicated significant amounts of primary BrC from biomass burning emissions. Secondary organic carbon BrC (SOC-BrC) was more abundant in winter than in summer. SOC-BrC in winter was mainly fresh SOC formed from aqueous phase reactions while in summer, aged SOC from photo-chemical formation. Source profiles of BrC optical parameters were detected, which verified sources of BrC from biomass burning and coal burning emissions in areas surrounding Xi'an. The rapidly decreasing b(abs-340nm) values from biomass burning smoldering to straw pellet burning suggested that burning straw pellet instead of burning straw directly is an effective measure for reducing BrC emissions. (C) 2016 Elsevier Ltd. All rights reserved

    Ni/La2O3-ZrO2 catalyst for hydrogen production from steam reforming of acetic acid as a model compound of bio-oil

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    Hydrogen production from steam reforming of acetic acid was investigated over Ni/La2O3-ZrO2 catalyst. A series of Ni/La2O3-ZrO2 catalysts were synthesized by sol-gel method coupled with wet impregnation, which was characterized by XRD, BET, TEM, EDS, TG, SEM and TPR. Catalytic activity of Ni/La2O3-ZrO2 was evaluated by steam reforming of acetic acid at the temperature range of 550-750 A degrees C. The tetragonal phase La0.1Zr0.9O1.95 is formed through the doping of La2O3 into the ZrO2 lattice and nickel species are highly dispersed on the support with high specific surface area. H-2 yield and CO2 yield of Ni/La2O3-ZrO2 catalyst with 15%wt Ni reaches 89.27% and 80.41% at 600 A degrees C, respectively, which is attributed to high BET surface area and sufficient Ni active sites in strong interaction with the support. 15%wt Ni supported on La2O3-ZrO2 catalyst maintains relatively stable catalytic activities for a period of 20 h

    Combustion characteristics of non-premixed methane micro-jet flame in coflow air and thermal interaction between flame and micro tube

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    The combustion characteristics of non-premixed methane micro-jet flame in coflow air were investigated experimentally and numerically. A detailed reaction mechanism was employed in the two-dimension numerical computation. The thermal interaction between the flame and solid tube was considered by using fluid-solid coupled thermal boundaries in the numerical computation. Four typical flames, lifted flame, attached flame, hemisphere flame and umbrella flame, were observed in different fuel flow velocity ranges in experiments. The flame heights, blow off and extinction limits in coflow airs at different velocities were measured. The OH and CH distributions of non-premixed micro-jet flames were obtained by experiments, and the computational results agree well with those from the experiments. The computational temperature distributions show that there are thermal interactions between flames and solid tube. The heat exchanges through surfaces of the solid tube were analyzed in detail. The fresh fuel gas in the solid tube is preheated by the thermal recirculation. Consequently, the combustion intensity of the micro-jet flame is enhanced. The thermal interaction is essentially affected by the flame shape, and it is significant for the hemisphere flame. (C) 2016 Elsevier Ltd. All rights reserved

    Synthesis of GO-modified Cu2O nanosphere and the photocatalytic mechanism of water splitting for hydrogen production

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    A new one-step method for synthesize cuprous oxide nanosphere without any additive surfactant in room temperature and atmospheric pressure was carried. The nanospheres with the diameters less than 100 nm were well-dispersed and formed the core shell structure with the GO. The partial reduction of GO increases the atomic percentage of sp(2) carbon (graphene sheets). It was found that sp(2) carbon with better conductivity plays an important role in mitigating electron hole recombination and enhancing electron transfer between Cu2O and GO and thus enhance the photocatalytic activity. The highest hydrogen yields for GO-modified samples (118.3 p.mol) were more than twice as large as that of bare Cu2O nanosphere (44.6 umol). 2016 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC

    Precisely controllable fabrication of Er3+-doped glass ceramic fibers: novel mid-infrared fiber laser materials

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    We demonstrated remarkably enhanced 2.7 mu m emission in glass-ceramic (GC) fibers containing NaYF4: Er3+ nanocrystals with 980 nm excitation for the first time. The melt-in-tube technique is of scientific and technical significance for the fabrication of GC fibers in comparison to the conventional rod-in-tube technique. The obtained precursor fibers, in which the structure can be maintained well, exhibit no obvious element diffusion or crystallization during the fiber-drawing process. After a careful heat treatment, NaYF4 nanocrystals were controllably precipitated in the glass fiber core. Owing to the incorporation of Er3+ ions into the low phonon energy NaYF4 nanocrystals, enhanced 2.7 mu m emission was achieved from the Er3+-doped GC fibers, which was almost undetectable in precursor fibers due to the high phonon energy of the borosilicate glass fiber matrix. Moreover, the 2.7 mm emission lifetime was obtained due to the excellent emission properties of Er3+ in the GC fibers. The transmission loss values of precursor fibers and GC fibers at 1310 nm were measured to be 7.44 dB m(-1) and 11.81 dB m(-1), respectively. In addition, a theoretical simulation based on the rate equations and propagation equations was performed to evaluate the possibility of 2.7 mu m laser output. The excellent optical properties endow the GC fibers with potential applications for mid-infrared fiber lasers
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