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05 May 2014, Volume 65 Issue 5
    CIESC Journal(HUAGONG XUEBAO)Vol.65 No.5 May 2014
    2014, 65(5):  0-0. 
    Abstract ( 368 )   PDF (8260KB) ( 478 )  
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    Progress of CO2 capture and separation by porous organic polymers
    ZHU Xiang, LÜ Wenjie, HU Jun, WANG Hualin, LIU Honglai
    2014, 65(5):  1553-1562.  doi:10.3969/j.issn.0438-1157.2014.05.001
    Abstract ( 1554 )   PDF (809KB) ( 1310 )  
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    Porous organic polymers (POPs), a new type of porous materials constructed by organic building blocks, have attracted attention and shown significant potential for CO2 capture and separation due to their high physicochemical stability and excellent adsorption capacity. Numerous POPs with good porosity (both surface area and pore volume) are prepared via different organic reactions. The progress of capture and separation of CO2 by POPs is reviewed. Several potential strategies like increasing isosteric heats between sorbent and CO2 molecules by chemical functionalization for enhancing CO2 separation performance are summarized.
    Progress of adsorption-based CO2/CH4 separation by metal organic frameworks
    ZHANG Suoying, LIU Hong, LIU Pengfei, WU Peipei, YANG Zhuhong, YANG Qingyuan, LU Xiaohua
    2014, 65(5):  1563-1570.  doi:10.3969/j.issn.0438-1157.2014.05.002
    Abstract ( 1436 )   PDF (507KB) ( 1654 )  
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    The high energy penalty of CO2 separation from biogas is a core problem in the biomethane process. Metal organic frameworks (MOFs) have recently attracted intense research interest because of their ultra-high CO2 adsorption capacity and potential applications as novel adsorbents to reduce energy cost. The recent progress of experimental researches on adsorption-based CO2/CH4 separation by MOFs is reviewed.
    Progress of Pb2+-recognition-responsive smart polymeric functional materials
    LIU Zhuang, JU Xiaojie, XIE Rui, WANG Wei, CHU Liangyin
    2014, 65(5):  1571-1576.  doi:10.3969/j.issn.0438-1157.2014.05.003
    Abstract ( 985 )   PDF (4919KB) ( 482 )  
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    Some of the anaerobic bacterium fermented bio-methane can adsorb heavy metals, such as Pb2+, which are enriched in biogas slurry and residue. For this reason, the detection and removal of heavy metal ions, such as Pb2+ ion in biogas slurry and residue is one of the key problems in the study of bio-methane systems. 18-crown-6 has remarkable recognition ability towards Pb2+ ion. The Pb2+ ion-recognition-responsive smart materials composed of 18-crown-6 and poly(N-isopropylacrylamide) (PNIPAM) have been developed. In this paper, the progress of investigation on Pb2+ ion-recognition-responsive smart polymeric materials based on 18-crown-6 and poly(N-isopropylacrylamide) for detection and removal of Pb2+ is reviewed.
    Simulation research on anaerobic digestion biogas generation from low-grade biomass
    LI Heng, KE Lanting, WANG Haitao, ZHENG Yanmei, WANG Yuanpeng, HE Ning, LI Qingbiao
    2014, 65(5):  1577-1586.  doi:10.3969/j.issn.0438-1157.2014.05.004
    Abstract ( 1341 )   PDF (543KB) ( 784 )  
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    Anaerobic digestion of low-grade biomass has attracted increasing interest in reducing greenhouse gas emission and facilitating sustainable development of energy supply. The theory of anaerobic digestion biogas generation and feedstocks are presented in this paper. It provides a review on mathematical model of and simulation research on the conversion of C, N, P in the process of anaerobic digestion. First order kinetic model is the simplest mathematical model which can simulate the dynamics of methane production. The advanced mathematical ADM1 is most popular, and simulates the conversion of C, N, P in anaerobic digestion. The model, simulation subjects and results of anaerobic digestion biogas generation of common substrates are given. Methane yield is the main subject of simulation investigation which is studied in almost all simulation researches on anaerobic digestion biogas generation, and some research reports the variation of volatile solid, volatile fatty acid, COD, CH4, CO2 and inorganic carbonate in the process of anaerobic digestion through mathematical modeling, with which the conversion of C can be determined. Simulation researches on the conversion of N include variations of ammonia nitrogen, inorganic nitrogen and total nitrogen. Simulation research on the conversion of P from sludge digestion is also presented. The challenges and future research trends of the conversion of C, N, P in the process of anaerobic digestion are forecasted.
    Research progress of biogas upgrading with external resource of hydrogen gas
    TU Rui, LI Jun, WANG Meng, LIU Chang, LU Xiaohua
    2014, 65(5):  1587-1593.  doi:10.3969/j.issn.0438-1157.2014.05.005
    Abstract ( 949 )   PDF (910KB) ( 438 )  
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    Biogas fermentation has two general problems, low production rate and low methane concentration. From the reaction mechanism for methane formation, if external H2 is supplied, CO2 in the biogas can be converted into CH4, leading to increased yield and concentration of methane. Recently published experimental studies reported that biogas could be purified and upgraded to a quality as biomethane with the addition of hydrogen gas. However, to make this technology practical, two key problems should be resolved. One is to intensify H2 transfer from gas phase to aqueous phase at low mixing speeds. The other is to obtain hydrogen gas with economical methods. A scheme is suggested for biogas upgrading through the integration of H2 generation by photoelectrocatalysis and CH4 production by anaerobic fermentation.
    Facilitated transport membranes for biogas upgrading
    TIAN Zhizhang, LI Yifan, JIANG Zhongyi, WANG Shaofei
    2014, 65(5):  1594-1601.  doi:10.3969/j.issn.0438-1157.2014.05.006
    Abstract ( 1300 )   PDF (569KB) ( 644 )  
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    Biomethane, purified from biogas, can be utilized as substitute for natural gas owing to its high calorific value (HCV). Typically biogas contains 60%—65% CH4, 35%—40% CO2, small amounts of hydrogen sulfide, water vapor and trace amounts of other gases. Treatment of raw biogas must be implemented in order to convert biogas into HCV biomethane. Membrane separation process exhibits many distinct advantages, including low energy consumption, high efficiency, high process flexibility and environment friendliness. Particularly, facilitated transport membrane exhibits predominant features for biogas upgrading because of its unique transport mechanism. Materials for facilitated transport membrane and corresponding preparation methods/technologies are summarized. Influences of impurities, such as water and hydrogen sulfide on membrane separation as well as some techno- economic issues are discussed. Finally, prospects on membrane separation technology in biogas upgrading are presented.
    Effect of temperature on methanogens metabolic pathway and structures of predominant bacteria
    WU Meirong, ZHANG Rui, ZHOU Jun, XIE Xinxin, YONG Xiaoyu, YAN Zhiying, GE Mingmin, ZHENG Tao
    2014, 65(5):  1602-1606.  doi:10.3969/j.issn.0438-1157.2014.05.007
    Abstract ( 1595 )   PDF (415KB) ( 1223 )  
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    Methanogens are strictly anaerobic archaea, which not only take part in the methanogenesis procedure but also limit this process. Temperature plays a key role in the anaerobic fermentation. Temperature could not only directly alter the community structure and function of methanogenic archaea,but also affect the supply of substrates for methanogens,which in turn indirectly regulates the pathways of methanogenic archaea.There are three pathway for methanogenesis, and they are started from acetic acid, H2/CO2 and C-1 compound respetively. Acetoclastic methanogenesis accounts for about two-thirds of the total methane production globally, while hydrogenotrophic methanogenesis accounts for about one third. Methanol- and methyl amine-derived methanogensis is restricted in ocean and saline water. Acetoclastic methanogenesis is the predominant methanogenesis at a low temperature, and methane is produced by acetoclastic and hydrogenotrophic methanogenesis at a medium temperature, while methane is exclusively produced by hydrogenotrophic methanogenesis at a high or ultra-high temperature.
    Application of population balance equation in numerical simulation of multiphase stirred tanks
    LI Qian, CHENG Jingcai, YANG Chao, MAO Zaisha
    2014, 65(5):  1607-1615.  doi:10.3969/j.issn.0438-1157.2014.05.008
    Abstract ( 915 )   PDF (635KB) ( 416 )  
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    The population balance equation (PBE) is generally used to describe the particle size distribution of the dispersed phase in multiphase systems. Considering the influence of particle events, such as aggregation and breakage, on particle size and number density, the PBE is a powerful tool for simulation of stirred reactors. The application of the PBE in stirred tanks is reviewed in this paper. After briefing the construction of the general form of the PBE, different numerical methods for solving the PBE are discussed. Specific applications of the PBE in simulation of precipitation processes, gas-liquid and liquid-liquid systems in stirred tanks are also presented.
    QSAR for predicting toxicity of imidazolium-based ionic liquids
    ZHAO Yongsheng, HUANG Ying, ZHAO Jihong, ZHANG Xiangping
    2014, 65(5):  1616-1621.  doi:10.3969/j.issn.0438-1157.2014.05.009
    Abstract ( 682 )   PDF (495KB) ( 300 )  
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    Due to the unique physical and chemical properties, ionic liquids (ILs) have shown great potential for industrial applications. However, their toxicity and potential environmental impact should be clearly understood. In this paper, five parameters selected by the heuristic method were used to study the minimum inhibitory concentration values of toxicity against E. coli based on the quantitative relationship between toxicity and structure of 40 kinds of imidazolium ionic liquids by using the quantitative structure-activity relationships (QSAR) method. Test set was used to conduct the external validation. This model with good reliability could be used to predict the toxicity of imidazolium-based ionic liquids.
    Thermochemical equilibrium analysis for wood pyrolysis
    QIAN Hongliang, YANG Tingting, LIU Chang, FENG Xin, LU Xiaohua
    2014, 65(5):  1622-1628.  doi:10.3969/j.issn.0438-1157.2014.05.010
    Abstract ( 975 )   PDF (720KB) ( 572 )  
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    Based on the Gibbs free energy minimization method, HSC chemistry software was used to calculate the thermochemical equilibrium of wood pyrolysis. The effect of temperature on composition and proportion of products of wood pyrolysis was discussed and pyrolysis process was divided into four zones. According to the criterion of spontaneous reaction (the relationship between Gibbs free energy and temperature), the reaction among products was discussed for the first time, and then the proper reactions at each zone were determined. At last, the effect of temperature on the wood pyrolysis products reported in literature is summarized, and the calculation results were found to be similar with experimental results of prior authors.
    Non-equilibrium thermodynamics analysis and its application for polymer composites design in tribological fields
    MU Liwen, SHI Yijun, FENG Xin, LU Xiaohua
    2014, 65(5):  1629-1635.  doi:10.3969/j.issn.0438-1157.2014.05.011
    Abstract ( 655 )   PDF (521KB) ( 294 )  
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    The heat generation and transfer process of self-lubricating materials and friction materials was quantitatively described from the fundamental principle of non-equilibrium thermodynamics. The effect of friction coefficient and thermal conductivity on the contact temperature of materials was studied, and the finding could guide the design of polymer composites. For the self-lubricating materials, the frictional heat generation and transfer process was assumed to be two processes in series. The frictional heat generated was the key controlling factor for stable operation of the friction system. For the friction materials, frictional heat transfer process was assumed to be heat transfer and heat distribution, two processes in parallel, and it was required to reduce thermal conductivity of the brake pads in order to lower contact surface temperature.
    Au/TiO2-B catalyst for low-temperature CO oxidation
    WANG Xibing, JI Tuo, LI Licheng, YANG Zhuhong, LU Xiaohua
    2014, 65(5):  1636-1643.  doi:10.3969/j.issn.0438-1157.2014.05.012
    Abstract ( 1072 )   PDF (5030KB) ( 443 )  
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    Exploring the catalytic performance of gold nanoparticles on the novel materials can effectively extend the application of gold catalyst. In this case, TiO2-B is used as a support to load gold nanoparticles for low-temperature CO oxidation. The TiO2-B was shaped in micron-scale fibers with length of 5—20μm, and the gold nanoparticles with size of ~ 3 nm could be uniformly dispersed on the surface of TiO2-B. CO oxidation tests showed that the catalytic performance of gold nanoparticles was influenced by calcination temperature of TiO2-B which gave rise to the difference in gold dispersion and interaction between gold nanoparticles and support. The activity of gold deposited on the support with pure TiO2-B phase could exceed/match that on anatase nanopowders. Moreover, the gold nanoparticles activated at 300℃ showed the best CO oxidation performance, and the catalyst activated in oxidative atmosphere had a better catalytic performance than that in inert or reductive atmosphere.
    Study on catalytic properties of metal-supported ZIF-8 with computational chemistry
    BO Xiaofan, WU Pingyi, LIU Dahuan, YANG Qingyuan, MA Qintian, LAN Ling, WANG Shaohua, ZHANG Yi, ZHONG Chongli
    2014, 65(5):  1644-1651.  doi:10.3969/j.issn.0438-1157.2014.05.013
    Abstract ( 1535 )   PDF (5554KB) ( 794 )  
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    Metal-organic frameworks (MOFs) are a new family of nanoporous functional materials that have shown potential applications in catalysis, due to their unique structural features. In this work, a combination of molecular simulation and density functional theory (DFT) calculation were employed to investigate the catalytic properties of metal-supported ZIF-8 with different metals (Pd, Ag, Pt and Au). First, the radial distribution function between these metal particles and the different atoms in ZIF-8 was analyzed from Monte Carlo (MC) and molecular dynamics (MD) simulations in order to determine the possible locations of the metal particles. Then, DFT calculations were performed at the generalized gradient corrected approximation (GGA) level with PW91 functional and the double numerical plus polarization (DNP) basis set. The binding energy was calculated to evaluate the relative stability of the metal particles (Pd, Ag, Pt and Au) in each site of the framework. The results showed that there were three types of interaction modes between the metals and the framework: carbon-metal-carbon (C-M-C), metal-carbon (M-C) and metal-bond (M-bond) modes, where the first type was the most stable one. For the same interaction type, the order of the stability of ZIF-8 with different metals was: Pd > Ag > Pt > Au. At the same time, the catalytic activity of the metal-supported materials was also investigated using CO as probe molecule. The analysis of the Mulliken population and the electrostatic potential distributions of metals indicated that metal particles were the Lewis acid sites which were related to their capabilities of accepting an electron. The order of their catalytic activities was: Pd > Pt > Ag > Au. The results obtained in this work may provide useful information for the catalytic application of MOFs loaded with metals.
    Solvent effect on catalytic properties of microstructures in metal-organic frameworks
    YING Yunpan, ZENG Fanping, WU Pingyi, YANG Qingyuan, LIU Dahuan, LAN Ling, WANG Shaohua, ZHANG Yi, ZHONG Chongli
    2014, 65(5):  1652-1659.  doi:10.3969/j.issn.0438-1157.2014.05.014
    Abstract ( 1711 )   PDF (4113KB) ( 732 )  
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    The nanoporous structures of metal-organic frameworks (MOFs) can be functionally regulated according to specific targets of interest, and thus such types of solids can be considered as promising industrial catalytic materials. Since interface microenvironments and catalytic properties of MOFs might be affected by the solvents, it is necessary to study the influence of solvent effects on their catalytic activities. Although MOFs with coordinatively unsaturated metal sites (CUMs) have shown promising applications in liquid-phase catalysis, the related solvent effects on the Lewis acid catalytic performance of these CUMs are seldom investigated. In this work, density functional theory calculations were conducted to investigate the solvent effects on the properties of the Lewis acid sites in two typical MOFs, Cu-BTC and MOP-15, where the COSMO (conductor-like solvent model) was used to mimic the dielectric response of the solvent environments. Different relative dielectric constants were considered, including in vacuum, toluene, ethyl acetate, 1, 2-dichloroethane and acetonitrile. Using CO as the probe molecule, the solvent effects were examined by exploring the geometry parameters, the Mulliken charges, and the vibrational frequency as well as the adsorption energy of CO molecule around those CUMs. The strengths of Lewis acid sites could be enhanced with the increase of the dielectric constant. Further, the solvent effects became more evident in CUMs when the organic linkers had higher electronegativity. These observations provide fundamental insights into the regulation of the liquid-phase catalytic activity of MOFs using specific solvents.
    Investigation of performance of SrFe0.6Cu0.3Ti0.1O3-δ mixed conducting membrane for partial oxidation of methane to syngas
    ZHANG Heng, WANG Tingting, NIE Yi, ZHANG Xiangping, LIN Weiming
    2014, 65(5):  1660-1666.  doi:10.3969/j.issn.0438-1157.2014.05.015
    Abstract ( 3236 )   PDF (2271KB) ( 291 )  
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    SrFe0.6Cu0.3Ti0.1O3-δ membrane was used to install a membrane reactor for partial oxidation of methane to syngas. The influences of temperature, space velocity and catalyst particle size on the reaction were studied, and the change of the phase structure of the membrane was analyzed. The interaction between the oxygen permeating process and the partial oxidation reaction caused different reaction performance in membrane reactor compared with fixed bed reactor. The crystallinity of both sides of the SrFe0.6Cu0.3Ti0.1O3-δ membrane declined significantly after the catalytic reaction. The decomposition of the perovskite structure and the formation of SrCO3 and other phases were found in the reaction-side surface of the membrane, along with the emergence of loose porous morphology.
    Production of 2, 3-dihydrobenzofuran and benzene by catalytic pyrolysis of bagasse over base catalysts
    WANG Xinde, LENG Shuai, QIU Huizhe, WANG Lei, LIU Jingmei, MA Fengyun, WANG Jianguo
    2014, 65(5):  1667-1672.  doi:10.3969/j.issn.0438-1157.2014.05.016
    Abstract ( 920 )   PDF (514KB) ( 260 )  
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    The influence of different pyrolysis catalysts (oxide, composite oxide, salts and supported Na2CO3) for bagasse on product (2, 3-dihydrobenzofuran and benzene) yield was investigated by pyrolysis experiment. Oxide, composite oxide and salt catalysts had high selectivity for high value 2, 3-dihydrobenzofuran (2, 3-DHB), with the highest yield (14.15%) over composite oxide. Supported Na2CO3 catalysts had high selectivity for benzene and the yield was as high as 22.4% over Na2CO3/TiO2.
    Gas separation properties of zeolitic imidazolate framework-8 membranes prepared by secondary synthesis
    ZHAO Zhenxia, XU Feng, LI Zhong
    2014, 65(5):  1673-1679.  doi:10.3969/j.issn.0438-1157.2014.05.017
    Abstract ( 899 )   PDF (3920KB) ( 651 )  
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    Permeation and separation properties for CO2/N2 mixtures with high quality, thin (~8.8 μm) zeolitic imidazolate framework-8 (ZIF-8) membranes prepared by the secondary growth method were studied at different temperatures and feed pressures. The crystal structure, surface coverage, uniformity of the prepared ZIF-8 seeding layers and membranes were characterized by using SEM and XRD. The low concentration of the seed suspension and subsequent dip-coating method helped to obtain a more uniform, continuous and ultrathin ZIF-8 seeds layer of support; the synthesized ZIF-8 membranes offered selective permeation for CO2 over N2 with CO2/N2 mixture feed under the experimental conditions studied. The separation factor of CO2/N2 mixed gas through a ZIF-8 film decreased with increasing temperature, but increased with increasing feed pressure. Its separation factor of CO2 over N2 could reach 6 at 298 K, 406 kPa, and CO2 content of 50%, exceeding the Knudsen diffusion selectivity.
    Molecular simulation of CO2 adsorption on amine modified micro/mesoporous composite of AM-5A-MCM-41
    ZHOU Jianhai, ZHAO Huiling, HU Jun, LIU Honglai, HU Ying
    2014, 65(5):  1680-1687.  doi:10.3969/j.issn.0438-1157.2014.05.018
    Abstract ( 818 )   PDF (7393KB) ( 695 )  
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    Combining the advantages of high selectivity of amine groups, high capacity of microporous zeolite, and high transportation of mesoporous structures, amine modified micro/mesoporous composites may exhibit promising CO2 adsorption capability. In this study, a full-atomic mimetic amine modified micro/mesoporous composite of AM-5A-MCM-41 was constructed. CO2 adsorption and separation performance on AM-5A- MCM-41 composite were investigated by the grand canonical Monte Carlo (GCMC), in which a specific combining rule was used to describe the weak chemical interaction between CO2 molecule and amine group. The simulation results demonstrate that CO2 is preferentially adsorbed around amine groups, which is grafted at the surface of mesoporous channels; and the CO2 adsorption capacity and its isosteric heat are greatly improved on AM-5A-MCM-41, whereas those of N2 are almost kept unchanged. For the separation of mixed gas of CO2 and N2, both CO2 adsorption capacity and CO2/N2 selectivity are greatly improved, due to the enhanced interaction between CO2 molecules and amine groups. The chemisorption plays a significant role in the capture of CO2 at low pressures and high temperature, giving a selectivity as high as 87.0 at 573 K and 100 kPa. The overall results show that molecular simulations serve as a powerful implement to assist the design and development of new promising CO2 adsorbents, highlighting the importance of this approach.
    Design and optimization of membrane-based system for bio-methane purification
    RUAN Xuehua, HE Gaohong, XIAO Wu, LI Baojun
    2014, 65(5):  1688-1695.  doi:10.3969/j.issn.0438-1157.2014.05.019
    Abstract ( 816 )   PDF (795KB) ( 366 )  
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    The production of compressed natural gas (CNG) from anaerobic fermentation gas is an important way for large scale use of biomass resources. A discrete simulation model for hollow fiber membrane is established by the finite element method in the process software UniSim Design, which is suitable for membrane separation with high permeation stage cut to purify bio-methane. The key operation condition, membrane feed pressure, which affects membrane process capacity, methane recovery ratio and CNG specific energy consumption, is studied by simulating the single-stage separation process of polyimide membranes. In this system, process capacity and methane recovery ratio are improved by increasing membrane feed pressure, but the lowest specific energy consumption is 0.46 kW·h·m-3 at membrane feed pressure of 2.70 MPa. After analyzing the change of methane content in permeate, a single-stage two-step membrane process is developed, with the advantages of compact process structure, low equipment investment, high methane recovery ratio and high production profit. For processing 1000 m3·h-1 feedstock, the methane recovery ratio is higher than 95%, with 500 m3·h-1 CNG yielded. The overall investment is 3.8×106 CNY, annual operation and depreciation cost is 1.5×106 CNY, and the annual gross economic profit can be 2.5×106 CNY at least.
    Control of pore size in Hf-based metal-organic frameworks and exploration of their adsorption properties
    WANG Keke, LI Liangsha, HUANG Hongliang, YANG Qingyuan, ZHANG Yi, WANG Shaohua, WU Pingyi, LAN Ling, LIU Dahuan, ZHONG Chongli
    2014, 65(5):  1696-1705.  doi:10.3969/j.issn.0438-1157.2014.05.020
    Abstract ( 943 )   PDF (2821KB) ( 818 )  
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    By incorporating three organic carboxylic acids with different lengths, fumaric (FUM), 1,4-benzene- dicarboxylate (BDC) and 4,4'-biphenyl-dicarboxylate (BPDC) acids, three novel Hf-based metal-organic frameworks (MOFs), Hf-FUM, Hf-BDC and Hf-BPDC, were synthesized using a solvothermal method combined with conventional electric heating. These MOFs were characterized by various experimental techniques including PXRD, N2 adsorption, TG and SEM. Moreover, the stabilities of these materials were examined by soaking the samples in water. The PXRD results reveal that all of these Hf-based MOFs have a topology similar to that of UiO-66(Zr), and Hf-FUM is stable up to 400 ℃ while Hf-BDC and Hf-BPDC remain stable at 500 ℃. The structures of Hf-FUM and Hf-BDC are water-resistant, while that of Hf-BPDC will decompose after water treatment. On the basis of the adsorption isotherms of CO2, N2 and CH4 at 298 K, the effect of pore size on the separation of CO2/N2 and CO2/CH4 systems were also investigated. It is found that Hf-FUM with the smallest pore size possesses the highest adsorption selectivity for CO2 over N2 and CH4. This is the first study on the performance of Hf-based MOFs for gas separation, and the knowledge obtained in this work provides a foundation for the design of new nanoporous materials towards CO2 capture from various gas mixtures.
    Synthesis of exceptional stable Hf-based metal-organic frameworks:characterization, stability and CO2 adsorption performance
    LI Liangsha, WANG Keke, HUANG Hongliang, YANG Qingyuan, ZHANG Yi, WANG Shaohua, WU Pingyi, LAN Ling, LIU Dahuan, ZHONG Chongli
    2014, 65(5):  1706-1715.  doi:10.3969/j.issn.0438-1157.2014.05.021
    Abstract ( 934 )   PDF (1052KB) ( 948 )  
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    By a high temperature and high concentration method, a metal-organic framework (MOF), UiO-66(Hf), was synthesized in a high degree of crystalline, and its thermal and chemical stability were examined in various environments including boiling water as well as strong acidic and basic solutions. In order to enhance its performance for gas separation, three new Hf-based MOFs with the pore surfaces having different chemical properties were further synthesized, using three organic ligands with different functional groups, aminoterephthalic acid (H2BDC-NH2), nitroterephthalic acid (H2BDC-NO2) and bromoterephthalic acid (H2BDC-Br). The synthesized materials were characterized using PXRD, TG, and N2 adsorption measurements, and the separation performance of these MOFs towards CO2/N2 and CO2/CH4 systems were also explored on the basis of adsorption isotherms for CO2, N2 and CH4. It is shown that the material presents exceptionally high stability under these conditions. The materials modified with functional groups have the same topology to the parent UiO-66(Hf). In addition, the introduction of polar functional groups, especially the amino (-NH2) group, can greatly improve the separation performance of materials for the removal of CO2 from these two systems. The knowledge obtained may provide theoretical guidance for the synthesis of novel nanoporous materials towards practical applications in the separation of chemical systems of interest.
    CO2 absorption properties of supported [APMIm][Br]
    CHEN Yifeng, WANG Changsong, DING Jian, YANG Zhuhong, LU Xiaohua
    2014, 65(5):  1716-1720.  doi:10.3969/j.issn.0438-1157.2014.05.022
    Abstract ( 1249 )   PDF (484KB) ( 574 )  
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    CO2 was absorbed by 1-aminopropyl-3-methylimidazolium bromine([APMIm][Br])as chemical reaction. The absorbents were prepared by supporting ionic liquids on porous silica gel through the impregnation-evaporation method, and pore structure and absorption capacity were characterized with specific surface pore adsorption apparatus and thermogravimetric analysis, respectively. CO2 absorption was conducted under the following conditions: 10% to 50% of ionic liquids loading, 303.15 K to 323.15 K of temperature, and 10%, 30%, 50% of CO2 in mixed gas. The results suggested that absorption rate was fastest when film thickness of ionic liquids on the silica gel was 86 nm, and was little affected by the change of CO2 concentration and temperature. Equilibrium absorption amount reached 80% of the theoretical uptake in 50% CO2 system, and was reducing with increasing temperature. However, absorption rate and capacity decreased obviously as film thickness of ionic liquid exceeded 230 nm. The properties of supported ionic liquid absorbent remained unchanged after recycling three times, showing the prospect of industrial use.
    Application of choline-based deep eutectic solvents in CO2 capture and separation
    ZHANG Yingying, JI Xiaoyan, LU Xiaohua
    2014, 65(5):  1721-1728.  doi:10.3969/j.issn.0438-1157.2014.05.023
    Abstract ( 1082 )   PDF (446KB) ( 365 )  
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    Choline-based deep eutectic solvents (DESs) are a new class of ionic liquids. With similar properties to ionic liquids, choline-based DESs have the advantages of easy synthesis, low price, low toxicity and biodegradability. In this work, the properties of choline-based DESs related to CO2 capture and separation were investigated, such as gas solubility, CO2 absorption-desorption, density, thermal stability, viscosity and surface tension. The influence of the structure of choline-based DESs on their properties were analyzed. The comparison of choline-based DESs with traditional ionic liquid showed that choline-based DESs could be used as absorbents for CO2 capture and separation due to high CO2 solubility and low viscosity. However, more research needs to be done before commercial application, for example, CO2 selectivity compared to other components in gas mixtures, surface tension as well as thermal-stability.
    Molecular design of metal-organic frameworks with different metal ligands for bio-methane separation
    QIAO Zhiwei, YANG Rendang, WANG Haihui, ZHOU Jian
    2014, 65(5):  1729-1735.  doi:10.3969/j.issn.0438-1157.2014.05.024
    Abstract ( 882 )   PDF (8834KB) ( 538 )  
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    The adsorption and separation capabilities of metal-organic frameworks (MOFs) for CO2 and CH4 gas mixtures were studied by grand canonical Monte Carlo (GCMC) simulations. Three sub-families (M-MOF-74, M-MIL-53 and [M(atz)(bdc)0.5]) (M=Mg, Co, Ni, Zn, Al, Cr) MOFs with different metal ligands were investigated. Simulation results showed that the CO2 adsorption capability of Mg-MOF-74 exceeded the others at high pressures; both amine functionalized [Zn(atz)(bdc)0.5] and [Co(atz)(bdc)0.5] MOFs had superior CO2 separation performance at low pressures. The radial distribution functions and the overlapping snapshots of CO2 adsorption showed that in each sub-family of MOFs, different metal ligands affected their CO2 adsorption configuration and resulted in their different adsorption and separation capabilities. This work could provide some guidance for the design and development of new high performance MOFs for CO2 and CH4 separation.
    Molecular simulations on diameter effect of carbon nanotube for separation of CO2/CH4
    CAO Wei, LÜ Linghong, HUANG Liangliang, WANG Shanshan, ZHU Yudan
    2014, 65(5):  1736-1742.  doi:10.3969/j.issn.0438-1157.2014.05.025
    Abstract ( 655 )   PDF (1389KB) ( 403 )  
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    Biomethane route has large potential in emission reduction and energy saving. One of the key issues is separation of biogas in operating conditions of 333 K and 0.1 MPa. Grand canonical Monte Carlo (GCMC) and equilibrium molecular dynamics simulations (EMD) were used to compute adsorption loadings and self-diffusivities of CH4/CO2 at various diameters of carbon nanotube (CNT) bundles. Single component and equimolar gases were simulated. CO2 always had larger adsorption loading and diffusion coefficient than CH4 as the result of relatively strong interaction between CO2 molecules and tube walls, due to the confined capacity. The permselectivity reached a maximum in closely 1 nm, and under such conditions the separation process was controlled by adsorption rather than diffusion.
    Separation of biogas with W/O emulsion
    LIU Huang, WU Yuqing, CHEN Guangjin, LIU Bei, YANG Lanying, PAN Yong
    2014, 65(5):  1743-1749.  doi:10.3969/j.issn.0438-1157.2014.05.026
    Abstract ( 591 )   PDF (1164KB) ( 321 )  
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    Water in oil emulsion was used to capture CO2 from biogas (CO2/CH4) under hydrate formation condition. Span 20 was used to disperse aqueous phase or hydrate in oil phase. The influences of temperature, feed gas composition, pressure and water cut on the separation efficiency of emulsion were investigated. The separation ability of the absorption-hydration hybrid method was much better than that of the single absorption separation method, and uniform and flowable hydrate slurry could be obtained. The separation ability of the emulsion system increased with decreasing temperature or increasing water cut in specific ranges. Taking into account both separation efficiency and flowability of the slurry, the suitable operation temperature, pressure and water cut were determined as 270.15—272.15 K, around 3.2 MPa and 20%—25%(vol), respectively. Under these conditions, after a two-stage separation, the content of CO2 in vapor phase could be reduced from 31%(mol) to nearly 10%(mol), more than 87%(mol) CO2 could be captured by the slurry.
    Mesoporous TiO2 with different selectivities of protein immobilization performance
    DONG Yihui, AN Rong, ZHUANG Wei, YAO Zhong, ZHU Yudan, LIU Chang, LU Xiaohua
    2014, 65(5):  1750-1758.  doi:10.3969/j.issn.0438-1157.2014.05.027
    Abstract ( 728 )   PDF (2618KB) ( 358 )  
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    Mesoporous TiO2 with adjustable pore diameter, high specific surface area and excellent biocompatibility has a good application prospect in biological molecules immobilization carriers. Mesoporous TiO2-500 were prepared as the stationary phase packing in High Performance Liquid Chromatograph by calcinating H2Ti2O5 at 500℃, and the TiO2 samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption and field-emmission scanning electron microscopy (FESEM). The residence time under different pH of bovine serum albumin, myoglobin and lysozyme through the new chromatograph column were tested. Nearly all three kinds of proteins were immobilized at pH =4.7, and the order of residence time of three proteins was lysozyme >myoglobin > bovine serum albumin under the condition of pH=7.4 and 11. Adsorption of three kinds of proteins on the surface of the mesoporous TiO2-500 under atmospheric pressure was consistent with chromatographic results, and the order of the immobilization capacity of mesoporous TiO2-500 for three kinds of proteins was lysozyme > myoglobin >bovine serum albumin. Therefore, due to the significant difference in protein immobilization performance, the mesoporous TiO2 has a potential application in protein adsorption and separation, immobilizing enzyme and other fields.
    CO2 and CH4 adsorption performance of modified MIL-53(Cr) via ammonia vapor
    YANG Yan, WANG Sha, ZHANG Zhijuan, XIAQibin, LI Zhong
    2014, 65(5):  1759-1763.  doi:10.3969/j.issn.0438-1157.2014.05.028
    Abstract ( 772 )   PDF (524KB) ( 422 )  
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    MIL-53(Cr)crystals were synthesized by the hydrothermal synthesis method, and then modified by ammonia vapor of different concentrations to obtain the modified materials NH3@MIL-53(Cr). The CO2 and water vapor isotherms on the NH3@MIL-53(Cr)were determined by means of the gravity method. Although the specific surface area of the modified materials NH3@MIL-53(Cr)became smaller compared to original MIL-53(Cr), their CO2 adsorption capacities per unit surface area of adsorbent became significantly higher, following the order: NH3@MIL-53(Cr)-3#>NH3@MIL-53(Cr)-2#>NH3@MIL-53(Cr)-1#. In addition, Isotherms of water vapor on the modified samples NH3@MIL-53(Cr) were lower than those on the MIL-53(Cr), suggesting significant improvement of hydrophobicity of the modified samples. The CO2 adsorption capacity of the NH3@MIL-53(Cr)-2# modified by using ammonia vapor of 1 mol·L-1 was the highest among the modified samples. More interestingly, the CO2 adsorption performance of the modified sample NH3@MIL-53 (Cr)-2# was significantly improved, while its CH4 adsorption performance was weakened, which would be helpful to enhance its selectivity for CO2/CH4 adsorption.
    Application of comb-like weak base resin for concentrating succinic acid by circulating desorption
    FANG Fang, LIU Xiaoning, WANG Nan, WANG Shuya, JIANG Min, WEI Rongqing, ZHENG Tao
    2014, 65(5):  1764-1770.  doi:10.3969/j.issn.0438-1157.2014.05.029
    Abstract ( 844 )   PDF (615KB) ( 403 )  
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    An effective and low energy consumption method was established for absorption and circulating desorption of succinic acid using a comb-like weak base polystyrene resin. The behavior of the comblike weak base resin (MKF-D30X) in adsorption and desorption of succinic acid was studied in terms of volume of desorption reagent, stages of desorption, desorption temperature and recycle desorption. MKF-D30X resin had good adsorption effect on succinic acid. And the maximum adsorption capacity could be up to 425 mg succinic acid·(g dry resin)-1. The desorption process for 3 g resin with saturated succinic acid was divided into two stages at 50℃ of each stage of 10 ml, 1.0 mol·L-1 HCl as desorption reagent. In the first stage, the concentration of succinic acid in desorption solution could be up to 52.4 mg·ml-1, and the concentration of succinic acid increased to 209.6% of original concentration (original concentration of 25 mg·ml-1). Recycle desorption not only maintained high concentration of succinic acid in the first stage of desorption, but also obtained twice concentration in the second stage. On the other hand, the concentration of succinic acid in the first desorption stage, as desorption reagent, had no obvious effect on desorption of succinic acid in next stage.
    Electrochemistry of glucose oxidase on modified carbon nanotubes
    WANG Jia, LI Junhua, ZHOU Jian
    2014, 65(5):  1771-1776.  doi:10.3969/j.issn.0438-1157.2014.05.030
    Abstract ( 833 )   PDF (692KB) ( 582 )  
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    Glucose oxidase (GOx) was immobilized on the electrode surface of multi-walled carbon nanotubes, amino functionalized carbon nanotubes (AMWNTs) and carboxyl functionalized carbon nanotubes (MWNTs-COOH). Electrochemical measurements indicated that the formal potentials of GOx immobilized on AMWNTs and MWNTs-COOH did not change, but their peak currents were improved. The peak current of GOx immobilized on AMWNTs was four times larger than that immobilized on MWNTs. The electrochemistry behavior of Nafion/GOx-AMWNTs/GC electrode were further characterized. The results indicated that GOx immobilized on AMWNTs could undergo a direct quasi-reversible electrochemical reaction and show good stability. Amino-functionalized electrodes could significantly improve the performance of GOx-based biofuel cells.
    Direct electrochemistry of glucose oxidase immobilized on mesoporous TiO2
    WU Xinbing, MENG Meng, ZHUANG Wei, LÜ Linghong, LU Xiaohua
    2014, 65(5):  1777-1783.  doi:10.3969/j.issn.0438-1157.2014.05.031
    Abstract ( 552 )   PDF (2654KB) ( 479 )  
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    A novel mesoporous TiO2 material (m-TiO2) was obtained by a soft chemistry method in the absence of any surfactants or templates. It was shown that the m-TiO2 had an anatase crystalline structure with well-distributed mesopores from XRD, N2 adsorption-desorption isotherms, FESEM and TEM. The FT-IR results indicated that glucose oxidase (GOx) could be well immobilized on m-TiO2. The electrochemical tests of the fabricated Nafion/GOx/m-TiO2 modified glass carbon electrode (GCE) showed fast direct electron transfer between GOx molecules and electrode surface, exhibiting a linear response to glucose concentration ranging from 0.1 to 1.2 mmol·L-1, and good sensitivity of 3.44 μA·mmol-1·L·cm-2, which proved that the novel m-TiO2 was a promising material for immobilization of GOx and fabrication of glucose biosensors.
    Biogas production using cornstalks and prokaryotic community composition
    YUAN Yuexiang, WEN Haoshen, HUANG Xianbo, LI Xiangzhen, LIU Xiaofeng, LI Dong, YAN Zhiying
    2014, 65(5):  1784-1791.  doi:10.3969/j.issn.0438-1157.2014.05.032
    Abstract ( 524 )   PDF (680KB) ( 344 )  
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    With pretreated cornstalks as raw material, a mesophilic batch fermentation study using a 10-L anaerobic reactor was carried out to investigate biogas production rate and prokaryotic composition. Fermentation started rapidly, and a peak in biogas production appeared after 3 days with volumetric gas production rate of 0.97 L·L-1·d-1. The rates of biogas production and methane production during 46 days were 236.84 ml·(g VS)-1 and 132.23 ml·(g VS)-1, respectively. During the fermentation process, prokaryotic composition was investigated using pyrosequencing technique. Prokaryotic diversity increased with the fermentation process, and prokaryotic composition shifted dramatically compared to the initial stage. Archaea was dominated by Methanomicrobia (89.63% of total archaeal reads), followed by Thermoplasmata (8.51%). About 22-29 bacterial phyla were identified, including Bacteroidetes (46.07% of total reads), Proteobacteria (20.51%), and Firmicutes (13.09%) as the predominant bacterial communities. Our research provides important implications on the regulation of prokaryotic composition for biogas production using cornstalks.
    Spatial differentiation of prokaryotes enhancing performance of co-fermentation with straw and swine manure
    LI Jiabao, RUI Junpeng, ZHANG Shiheng, SUN Xiaori, YAN Zhiying, LIU Xiaofeng, ZHENG Tao, LI Xiangzhen
    2014, 65(5):  1792-1799.  doi:10.3969/j.issn.0438-1157.2014.05.033
    Abstract ( 864 )   PDF (581KB) ( 466 )  
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    Anaerobic co-fermentation of straw and manure is a potential technique for biogas production. In this process, the spatial and temporal dynamics of prokaryotes associated to straw and sludge, and their correlations with bioreactor performance remain to be unveiled. To address these questions, prokaryotic compositions and dynamics associated to straw and sludge were investigated during co-fermentation of straw and swine manure using pyrosequencing technique. Co-fermentation of straw and swine manure contributed significantly to fermentation performance. Further analysis indicated that spatial distribution pattern of prokaryotes in the co-fermentation system might increase fermentation efficiency. Straw was digested by its associated microbiota, such as genera Treponema, Clostridium Ⅲ, Alkaliflexus and Fibrobacter, providing substrates for the production of volatile fatty acids (VFAs). Propionic acid was most abundant in the sludge. The genera Syntrophomonas, Pelotomaculum, Methanoculleus, Methanosarcina and Methanosaeta metabolize VFAs into methane syntrophically via both hydrogenotrophic and acetocalstic pathways. The genera Aminobacterium and Cloacibacillus involved in amino acid degradation were much abundant in the sludge, indicating that protein was an important substrate for methanogenesis. These findings suggested that spatial distribution of microbiota, steady straw-associated degraders and dynamic microbial communities in the sludge were vital for the performance of biogas co-fermentation system.
    Microbial community compositions and diversity in pit mud of Chinese Luzhou-flavor liquor
    TAO Yong, RUI Junpeng, LI Jiabao, XU Zhancheng, LI Daping, TANG Qinglan, WEI Yong, LI Xiangzhen
    2014, 65(5):  1800-1807.  doi:10.3969/j.issn.0438-1157.2014.05.034
    Abstract ( 775 )   PDF (493KB) ( 675 )  
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    Pit mud (PM) plays a key role in controlling the quality of Chinese Luzhou-flavor liquor in anaerobic fermentation. Here, microbial community composition and diversity in PM samples using pyrosequencing technique were investigated. A total of 494293 valid sequences were obtained. The reads fell into 796 operational taxonomic units (OTUs) affiliated to 21 phyla. The predominant groups were Firmicutes (66.8% of total reads), Bacteroidetes (16.0%), Euryarchaeota (9.0%), Spirochaetes (2.2%), Actinobacteria (1.8%) and Chloroflexi (1.0%). Microbial diversity increased with cellar age until 25 years old, but kept relatively constant from 25 to 50 years. A large difference between microbial communities was observed in the pit muds with different cellar ages. Lactobacillus predominanted in 1-year pit mud (62.3%), but its abundance decreased remarkably in 10-year and older pit muds. In contrast, the abundances of Petrimonas, Clostridium IV and methanogens increased dramatically. In addition, Archaea in PM were mainly composed of hydrogenotrophic methanogens such as Methanobrevibacter, Methanoculleus, Methanobacterium, while the H2/acetate-utilizing Methanosarcina was more abundant in PM with cellar age of 25—50 years (3.1%—4.5%). This research supports the practical experience that old fermentation pits produce high quality Luzhou-flavor liquor.
    Screening strains of desulfurization bacteria by high-throughput sequencing
    XU Ying, SUN Yongming, ZHENG Tao, YUAN Zhenhong, LI Ying, KONG Xiaoying, LI Zhibing
    2014, 65(5):  1808-1814.  doi:10.3969/j.issn.0438-1157.2014.05.035
    Abstract ( 975 )   PDF (1618KB) ( 766 )  
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    In order to provide technical support for high-value utilization of bio-methane, the traditional screening method was combined with high-throughput sequencing to develop a new method for screening strains of desulfurization bacteria. Soil samples were taken from the environment rich in desulfurization bacteria; then the same samples were treated with enriched medium. High-throughput sequencing of samples were performed in the V6 region of 16S rDNA to analyze species content and abundance, alpha diversity and species structures of a single group. The average data utilization ratio of high-throughput sequencing was 99.177%, adequately reflecting the samples' species content and structures of the V6 region. The species composition of soil samples was rich, including some desulfurization bacteria, such as Pseudomonadales, Rhizobiales, Desulfuromonadales, Desulfobacterales and Acidithiobacillales. Species screened from enriched medium mainly contained Pseudomonadales and Rhizobiales, and lower species diversity was observed. The high-throughput sequencing technology provided a more selective method in bacteria screening and enhanced understanding of the samples' species content and structure before screening desulfurization bacteria.
    Influence of tentacles-like support with chain containing epoxy group on activity of immobilized lipase (YCJ01)
    YANG Changqing, ZHENG Tao, YU Chenchen, ZHOU Jun, HE Bingfang, LIU Xiaoning
    2014, 65(5):  1815-1820.  doi:10.3969/j.issn.0438-1157.2014.05.036
    Abstract ( 827 )   PDF (577KB) ( 416 )  
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    In order to improve the enzyme conformation for the negative effect of the rigid immobilized enzyme, the hydrophilic and flexible support PS-acyl-P(acrylamide-co-glycidyl methacrylate) with tentacles-like chain containing epoxy group was prepared with the atom transfer radical polymerization (ATRP) method. A series of chain length of tentacles-like support with epoxy group were prepared via changing the proportion of the total monomers to the initiator, and were used for flexible immobilization of organic solvent-tolerant lipase (YCJ01) covalently. The major objective of this paper was to investigate the effect of different lengthes of chain on the activity of immobilized lipase. The longer the chain length (weight gain <3200%) was, the higher the activity of immobilized lipase was.
    Butanol fermentation by fibrous bed bioreactor integrated with gas stripping
    ZHUANG Wei, ZHAO Xiangyu, YANG Jing, HE Linjiao, WU Jinglan, YANG Zhuhong, YING Hanjie
    2014, 65(5):  1821-1827.  doi:10.3969/j.issn.0438-1157.2014.05.037
    Abstract ( 822 )   PDF (615KB) ( 370 )  
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    Acetone-butanol-ethanol (ABE) fermentation with Clostridium acetobutylicum CGMCC 5234 immobilized in fibrous bed bioreator was studied for its potential utilization to produce ABE that can be easily recovered by gas stripping with gas products CO2 and H2. The process was conducted in fed-batch fermentation for twelve feeding cycles over 309 h, and 133.3 g·L-1 ABE(83.5 g·L-1 butanol, 38.4 g·L-1 acetone, 11.4 g·L-1 ethanol) was produced. The overall productivity and yield were 0.431 g·(L·h)-1 and 0.333 g·g-1 for ABE and 0.270 g·(L·h)-1 and 0.209 g·g-1 for butanol. The concentration of butanol in the fermentation liquid was 8—12 g·L-1. Phase separation of condensed ABE after gas stripping with up to 603.7 g·L-1 butanol in the butanol phase would relieve the burden of subsequent separation and purification. The results showed that the fed-batch fermentation with intermittent gas stripping was feasible and competitive.
    Computer simulation of bioenergy-oriented enzyme immobilization
    ZHAO Daohui, PENG Chunwang, LIAO Chenyi, ZHOU Jian
    2014, 65(5):  1828-1834.  doi:10.3969/j.issn.0438-1157.2014.05.038
    Abstract ( 881 )   PDF (2894KB) ( 341 )  
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    It is becoming increasingly important to get bioenergy from biomass with enzyme immobilization technology. The interactions between enzymes and carrier surfaces strongly influence the orientation of the immobilized enzymes and thereby affect catalytic efficiency. In this work, Parallel Tempering Monte Carlo (PTMC) simulations were performed to study the adsorption orientations of three kinds of bioenergy-related enzymes (lipase, cellobiohydrolase and hydrogenase) on different electrically charged surfaces and under different solution ionic strength conditions. Simulation results showed that the adsorption of the three enzymes was dominated by electrostatic interactions, and largely relied on the distribution of charged surface amino acids and the screening effect from ions in the solution. It was also found that lipase and hydrogenase adsorbed on negatively charged surface with the active sites toward the solution and the electron transfer channel close to the surface, respectively; while cellobiohydrolase took a preferred orientation on the positively charged surface. This work will provide some guidance for immobilization of industrial enzymes on carrier materials with proper orientation.
    Economic analysis of pig farm biogas projects in China and Germany
    LIU Chang, WANG Jun, PU Shaorui, LU Xiaohua
    2014, 65(5):  1835-1839.  doi:10.3969/j.issn.0438-1157.2014.05.039
    Abstract ( 514 )   PDF (402KB) ( 390 )  
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    Biogas projects of large & medium-scale husbandry farms are significant in reducing environmental pollution and getting access to renewable energy. However, they are all generally dependent on government subsidy in China, and their profitability is poor. In this work, we made contrastive analysis on the economy of pig farm biogas projects in China and Germany based on biogas fermentation steady-state model. Biogas fermentation process, generator efficiency and tariff are the key factors that affect economic efficiency. Currently, low electricity tariff [0.42 CNY·(kW·h)-1] is the root cause for the loss of biogas projects. On the basis of improving the technology of biogas and power generation and reaching the level in Germany, changing the policy of giving construction subsidies without paying attention to operational efficiency to attaching importance to actual emission reduction and increasing tariff to 1.5 CNY·(kW·h)-1 can shorten the payback period of the project within 3 years, which is of great importance to accelerating the development of biogas industry in China.
    Component analysis and risk assessment of anaerobically digested slurry from households in China
    KE Lanting, WANG Haitao, WANG Yuanpeng, HE Ning, LI Qingbiao
    2014, 65(5):  1840-1847.  doi:10.3969/j.issn.0438-1157.2014.05.040
    Abstract ( 631 )   PDF (593KB) ( 296 )  
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    Forty-three biogas slurries from household biogas plants using different substrates were collected from different parts of China. The contents of chemical oxygen demand (COD), ammonium nitrogen (NH4+-N), phosphate (PO43-) and heavy metals were determined. The concentrations of COD in cow dung and straw as raw materials were higher than other treatments, reaching 6800 mg·L-1 and 5800 mg·L-1 respectively. The concentrations of NH4+-N in pig manure and mix manure were higher than other treatments, reaching more than 1800 mg·L-1. The concentration of NH4+-N in cow dung was significantly lower than that in other materials, with the average being 450 mg·L-1. Therefore, COD/ NH4+ ratio of 15 in the slurry with cow dung as raw material was significantly higher than those in other three materials (less than 5). The average PO43- concentrations of all raw biogas were lower than 80 mg·L-1. Mercury pollution was serious and universal in different materials and different provinces. Environment risk evaluation showed that the pollution in biogas slurries from Yunnan, Henan and Hubei was medium and could not be ignored.
    Adsorption behavior of Fe-Mn binary oxide towards As(Ⅲ) and As(Ⅴ) and its application in biogas slurry
    PENG Changjun, JIANG Xiuli, JI Hongfang, WANG Yuanpeng, OUYANG Tong, LI Qingbiao
    2014, 65(5):  1848-1855.  doi:10.3969/j.issn.0438-1157.2014.05.041
    Abstract ( 833 )   PDF (2164KB) ( 325 )  
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    The adsorption behavior of arsenite (As(Ⅲ)) and arsenate (As(Ⅴ)) by Fe-Mn binary oxide (FMBO) was studied. The results indicated that FMBO had strong adsorption ability to both As(Ⅲ) and As(Ⅴ) and the maximum adsorption capacity was 111.10, 71.40 mg·g-1 respectively. As(Ⅲ) and As(Ⅴ) were adsorbed on FMBO surface through forming inner-sphere surface complexes by ligand exchange with hydroxyl groups, and As(Ⅲ) removal by FMBO was through an oxidation and adsorption combined process. In addition, the influences of co-existing substances generally present in biogas slurry were examined. Zinc ion could promote As(Ⅲ) and As(Ⅴ) adsorption on FMBO and the adsorption capacity increased with increasing zinc ion concentration. Phosphate had significant effect on As(Ⅲ) and As(Ⅴ) removal. When P/As ratio was equal to 1, the adsorption capacity of As(Ⅲ) and As(Ⅴ) was reduced by 34.70%, 31.50%, respectively. However, organics, such as humic acid, animal protein and carbamide had no significant effect on As(Ⅲ) and As(Ⅴ) removal. Moreover, FMBO as adsorbent for removal arsenic of actual biogas slurry was investigated. The average removal rate of arsenic of actual biogas slurry was about 65%, decreasing the arsenic concentration of some biogas slurry to the drinking water and surface water discharge standard. Therefore, FMBO could be an attractive adsorbent for both As(Ⅴ) and As(Ⅲ) removal from biogas slurry.
    Preparation of biochars from biogas residue and adsorption of ammonia-nitrogen in biogas slurry
    ZHENG Yangqing, YU Qiangqiang, WANG Haitao, WANG Yuanpeng, HE Ning, SHEN Liang, LI Qingbiao
    2014, 65(5):  1856-1861.  doi:10.3969/j.issn.0438-1157.2014.05.042
    Abstract ( 1219 )   PDF (3159KB) ( 497 )  
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    Five types of biochars were prepared through chemical activation utilizing fermentation residue from biogas plants. NaOH, KOH, H2SO4, H3PO4 and ZnCl2 were used as chemical activating agents. Biochars could absorb ammonia-nitrogen in biogas slurry. Biochar derived from KOH treatment (KOH-CC) showed better adsorption efficiency than the others. The adsorption process followed pseudo-second-order kinetics, and the adsorption isotherm could be fitted to Langmuir equation. Simulation test indicated that the maximum adsorption capacity could reach 120 mg·g-1. The properties of KOH-CC were characterized by BET, SEM, XRD and FTIR. The machanism of ammonia-nitrogen adsorption was discussed.
    Start-up process for high-solid anaerobic fermentation of corn straw
    SHI Xiaoshuang, YUAN Xianzheng, JIA Zhili, QIU Yanling, WANG Chuanshui, GUO Rongbo
    2014, 65(5):  1862-1867.  doi:10.3969/j.issn.0438-1157.2014.05.043
    Abstract ( 708 )   PDF (2462KB) ( 422 )  
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    High-solid anaerobic fermentation has the advantages, such as higher biogas yield per unit volume, more organic waste disposal, smaller water requirement and less energy consumption. However, the reactor is difficult to start and easy to acidize due to high concentration of feedstock. Using corn stalk as substrate, the performance of start-up process, different inocula and slurry recycling methods were studied during the start-up process for high solid anaerobic fermentation. The reactor system remained stable during the start-up phase with the combined method of feedstock feeding and slurry recycling. The cumulative biogas yields were 43.54 ml·(g TS)-1 with sludge as inoculum and 115.15 ml·(g TS)-1 with corn straw wet fermentation slurry as inoculum in 22 days. X-Ray diffraction (XRD) showed that the CrI was strongly influenced by the microflora, which showed that semicellulose was mainly dissolved. Fluorescent in situ hybridization (FISH) demonstrated that the methanogenic archaea exhibited an obvious difference in the two methane fermentation systems inoculated with sludge and corn straw biogas slurry, respectively.
    Prokaryotic community structures in biogas plants with swine manure
    RUI Junpeng, LI Jijin, LI Jiabao, WANG Yuanpeng, KE Lanting, ZHANG Shiheng, LI Xiangzhen
    2014, 65(5):  1868-1875.  doi:10.3969/j.issn.0438-1157.2014.05.044
    Abstract ( 1071 )   PDF (721KB) ( 490 )  
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    Slurry samples from 13 industrial biogas plants using swine manure as raw substrate were collected from different regions in China. The prokaryotic community compositions were investigated using 16S rRNA amplicon high-throughput sequencing technique. The results showed that Firmicutes was the most abundant phylum in these biogas plants, followed by Bacteroidetes, Proteobacteria and Chloroflexi. The ratio of ammonium to phosphate was the main factor affecting prokaryotic community structure and diversity for similar temperatures and substrates. A high ratio of ammonium to phosphate enriched Firmicutes, especially the genus Clostridium sensu stricto, while Bacteroidetes and Proteobacteria preferred a low ratio. Ammonium influenced the compositions of methanogens since their tolerance degrees to ammonium were different (hydrogenotrophic methanoges > Methanosarcina > Methanosaeta). Community compositions of methanogens and syntrophs were the most important biotic factors affecting biogas production rate. Biogas production rate could be increased by increasing the abundances of hydrogenotrophic methanoges and syntrophic propionate-oxidizing bacteria.
    Effect of NaOH pretreatment on methane yield of corn straw at different temperatures by anaerobic digestion
    SONG Zilin, SUN Xuewen, YANG Gaihe, YAN Zhiying, YUAN Yuexiang, LI Dong, LI Xiangzhen, LIU Xiaofeng
    2014, 65(5):  1876-1882.  doi:10.3969/j.issn.0438-1157.2014.05.045
    Abstract ( 929 )   PDF (645KB) ( 380 )  
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    Methane production through anaerobic digestion (AD) using agricultural straw is an important way to resolve the energy shortage in rural China. However, the AD technology is limited by low conversion efficiency due to recalcitrant nature of lignocellulosic structure in the straw. In the present study, the effect of sodium hydroxide (NaOH) pretreatment at three temperatures on the biogasification performance of corn straw through AD was evaluated by using a laboratory-scale, continuous anaerobic biogas digester. NaOH pretreatment was effective in biodegradation of the lignocellulosic structure of corn straw. The cellulose content of pretreated straw was decreased by 24.4% to 33.2%, the hemicellulose content decreased by 14.2% to 52.4%, and the lignin content decreased by 9.3% to 29.3%, compared with those of untreated straw. The highest methane yield, 188.7 ml CH4·(g VS)-1, was achieved when the corn straw was pretreated with 8% NaOH at 55℃, which was 84.2% higher than that of untreated straw. Therefore, pretreatment of 8% NaOH at 55℃ is recommended to improve biodegradability and enhance anaerobic digestibility of straw.
    Effect of acid and alkali pretreatment on anaerobic fermentation of artemisia selengensis straw
    XIE Xinxin, ZHOU Jun, WU Meirong, YONG Xiaoyu, WANG Shuya, ZHENG Tao
    2014, 65(5):  1883-1887.  doi:10.3969/j.issn.0438-1157.2014.05.046
    Abstract ( 756 )   PDF (480KB) ( 346 )  
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    In order to compare the effects of different pretreatment methods on gas production performance of artemisia selengensis straw, the straw was pretreated with acid or alkali of different concentrations before anaerobic digestion. Alkali pretreatment could effectively improve the performance of biogas production comparing with the control group, and the 2% NaOH pretreatment was the best. VFA concentration could be up to 4882.34 mg·L-1 at the early stage of anaerobic fermentation in the alkali pretreatment system, which was 705.21% higher than the control group. The gas yield of unit total solid (TS) was 288.42 ml·g-1 in the alkali pretreatment system, which was 17.08% higher than control group, and methane content reached 61.14%.
    Effect of waste heat recovery on net biogas yield in thermophilic biogas plants
    HUA Jing, TENG Ziyan, LU Xiaohua, YANG Zhuhong, WANG Changsong
    2014, 65(5):  1888-1892.  doi:10.3969/j.issn.0438-1157.2014.05.047
    Abstract ( 759 )   PDF (733KB) ( 282 )  
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    As a more productive process, themophilic digestion has not been popularized in China for the possibility of negative net biogas yield. A heat demand model based on the biogas plant at Alviksgården, Sweden was established to calculate the heating load so as to investigate energy consumption and net biogas yield. By comparing to the mesophilic biogas plant with the same scale in Jintan, Jiangsu, the results showed that despite the energy consumption of the thermophilic biogas plant at Alviksgården 2.1 times of the mesophilic one in Jintan, with a much higher biogas volumetric productivity as 2.3 m3·m-3·d-1, the biogas yield increment from increasing the digestion temperature from mesophilic to thermophilic was considerably larger than the energy consumption increment used for heating. Based on the current biogas productivity of the biogas plant at Alviksgården, if waste heat recovery was introduced to further decrease energy demand in substrate heating, net biogas yield could be increased from 82% to 90%. While without waste heat recovery, biogas productivity should be increased to 4.2 m3·m-3·d-1 to reach the same net biogas yield, suggesting that waste heat recovery was more efficient and economical than increasing biogas productivity via improvement of digestion technology to further increase net biogas yield.
    Numerical analysis of steady state self-humidification performance of PEMFC
    LI Ying, ZHOU Qinwen, ZHANG Xiangping
    2014, 65(5):  1893-1899.  doi:10.3969/j.issn.0438-1157.2014.05.048
    Abstract ( 755 )   PDF (596KB) ( 367 )  
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    External humidification for fuel and oxidant gases of PEMFC makes the system complicated, it is of practical interest to operate PEMFCs through self-humidification. The key to improve PEMFC performance of self-humidification operation is to maintain the polymer electrolyte membrane adequately hydrated. Thus, self-humidifying membrane electrode assembly (MEA) is an effective way. In this paper, a mathematical model of water transport balance was developed to predict water content distribution in proton exchange membrane, and further study the feasibility and stability of self-humidification operation. Numerical analysis illustrated that the membrane was thin enough to satisfy the demand of hydration. In order to maintain the membrane hydrated well and achieve good performance of PEMFC, cell temperature and operating pressure were set 60℃ and 0.15 MPa, air stoichiometry was increased to 1.8. Based on these conditions, the performance of PEMFC showed a little difference between self-humidification and full-humidification. But there was a large gap compared to optimized full-humidification. It was applicable for self-humidificaiton to simplify the structure and reduce the cost, mass and complexities of PEMFC. But full humidification cannot be replaced completely.
    Electrical and degradation characteristics of microbial fuel cell using biogas slurry as substrate
    CAO Lin, YONG Xiaoyu, ZHOU Jun, WANG Shuya, YONG Yangchun, SUN Yongming, CHEN Yilu, ZHENG Tao
    2014, 65(5):  1900-1905.  doi:10.3969/j.issn.0438-1157.2014.05.049
    Abstract ( 767 )   PDF (2942KB) ( 387 )  
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    In order to improve the efficiency of biomass energy utilization and reduce the cost for wastewater treatment, an air-cathode membrane-free microbial fuel cell (MFC) was constructed by using carbon cloth as electrode and cattle biogas slurry as anode fed. MFC could use biogas slurry to produce electricity, and the highest output voltage was 330 mV, the internal resistance was 10 kW and maximum power density was 10.98 mW·m-2 . Insoluble substance in MFC was the main reason for low output voltage and power density. After running for 24 h, the degradation rate of COD, total nitrogen and total phosphorus reached 20.73%, 67.82% and 72.56%, respectively. Therefore, MFC as a new way to generate electricity is quite promising in energy conservation and emissions reduction.
    Methane production from corn stalk by wet-dry two-stage anaerobic digestion process
    LIAN Shujuan, SHI Xiaoshuang, YUAN Xianzheng, YANG Zhiman, WANG Chuanshui, GUO Rongbo
    2014, 65(5):  1906-1912.  doi:10.3969/j.issn.0438-1157.2014.05.050
    Abstract ( 872 )   PDF (679KB) ( 426 )  
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    Dry fermentation is a potential trend in biogas industry, but the slow start-up and uneven mass transfer in the fermentation system block its application. In this study, wet fermentation was adopted as the start-up phase of dry fermentation to promote two-stage anaerobic fermentation. The effect of the fermentation time of the first wet fermentation stage (3 d, 5 d, 10 d, 15 d and 25 d) on the two-stage anaerobic fermentation was investigated. Lignocellulose degradation and SCOD (soluble chemical oxygen demand) changes in the first-stage wet fermentation were tested and the kinetics analysis for the two-stage fermentation process was fitted. The total methane yield of the whole fermentation with the wet fermentation period of 3, 5, 10, 15 and 25d were 208.17, 185.83, 218.63, 219.44 and 218.85 ml·(g VS)-1, respectively, which indicated that the period of wet fermentation stage above 10 d was necessary to guarantee biogas production of the dry fermentation process. Kinetics fitting analysis showed that the RC model was more suitable for the experimental study on anaerobic fermentation process, compared with the GM and LM models.
    Basic research on utilization of stillage for biogas production
    FU Shanfei, XU Xiaohui, SHI Xiaoshuang, WANG Chuanshui, QIAO Jiangtao, YANG Zhiman, GUO Rongbo
    2014, 65(5):  1913-1919.  doi:10.3969/j.issn.0438-1157.2014.05.051
    Abstract ( 2047 )   PDF (598KB) ( 1232 )  
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    Anaerobic digestion of stillage residue from the ethanol and wine industry is a promising method to provide energy and reduce waste. In addition, biogas slurry and biogas residue can be used as biological fertilizer after anaerobic digestion. In this study, anaerobic digestion of stillage was tested at medium temperature, meanwhile, the element changes and the feasibility of biogas slurry used as biological liquid fertilizer were investigated. The cumulative biogas yields from corn ethanol stillage, Maotai-flavor stillage, Luzhou-flavor stillage and cassava fuel ethanol stillage were 607.4, 578.7, 434.2, 122.3 ml·g-1(based on VS), respectively. The methane contents of biogas ranged from 60% to 70%. The biogas potential of stillage was proportional to degradation of substrates. The ions content of biogas slurry was in the range of the standard of biological liquid fertilizer.
    Preparation of Al2O3@TiO2 biological composite support and adsorption of bovine serum albumin
    JI Tuo, CHEN Xianfu, JI Xinghong, WANG Xibing, YANG Zhuhong, LU Xiaohua
    2014, 65(5):  1920-1927.  doi:10.3969/j.issn.0438-1157.2014.05.052
    Abstract ( 836 )   PDF (2167KB) ( 460 )  
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    A series of Al2O3@TiO2 composite supports were prepared and they were covered with a layer of mesoporous TiO2 by using titanate sol or titania sol. The differences of structures and properties of two TiO2 samples and their influences on adsorption of bovine serum albumin (BSA) were analyzed. The pore sizes of three alumina supports were 0.37,10.4 and 21.8 mm respectively. The results of XRD and Raman spectroscopy showed that both TiO2 samples were anatase phase. In addition, N2 adsorption-desorption isotherms showed that two samples had similar surface area [(100±10) m2·g-1] and mesoporous structure. Moreover, FESEM image indicated that the morphologies of TiO2 prepared from potassium titanate sol were affected by pore diameter of Al2O3 support. BSA adsorption performance indicated that the adsorption capacity of 20 mm Al2O3@TiO2 composite support prepared with potassium titanate sol (SP20@K-TiO2) was 22.18 mg·g-1, higher than the same size composite support prepared with titania sol. The adsorption capacity of TiO2 in SP20@K-TiO2 waps 150.88 mg·g-1. Compared with TiO2 powder, the BSA adsorption performance of TiO2 in the composite support was promoted.
    Effect of different amino modified conditions on carbon dioxide adsorption of NH2-MIL-53(Al)
    YANG Zhuhong, WU Peipei, ZHANG Suoying, LIU Hong, LIU Pengfei, YANG Qingyuan, LU Xiaohua
    2014, 65(5):  1928-1934.  doi:10.3969/j.issn.0438-1157.2014.05.053
    Abstract ( 1121 )   PDF (769KB) ( 764 )  
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    With the hydrothermal synthesis method, MIL-53(Al) of different amino contents was prepared by changing the content of 2-amino terephthalic acid in ligands. The CO2 adsorption of NH2-MIL-53(Al) was investigated by varing the content, type of amino group and amino functional methods to improve the CO2 capture performance of MIL-53(Al). The synthesized materials were characterized with XRD, TG, infrared spectroscopy and N2 adsorption measurements, and the adsorption performance of NH2-MIL-53 towards CO2 was also investigated on the basis of the adsorption isotherms. The IR results indicated that the peak of —NH2 was found in the range of 3500—3900 cm-1, demonstrating that amino group was loaded successfully. The performance of CO2 adsorption kept fitting with the amino group content of NH2-MIL-53(Al), and when amino group content was 100%, better CO2 adsorption than MIL-53(Al) prepared directly was observed. In addition, when MEA, DBU and MMEN were used for post-synthesis modifications, they all could not improve the adsorption performance of NH2-MIL-53(Al) towards CO2.
    Synthesis and characterization of new type polytetrahydrofuran polyol
    YU Chenchen, LIU Xiaoning, LI Yanmin, YONG Xiaoyu, DING Lingpeng, WEI Rongqing, ZHENG Tao
    2014, 65(5):  1935-1940.  doi:10.3969/j.issn.0438-1157.2014.05.054
    Abstract ( 879 )   PDF (656KB) ( 471 )  
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    Ring-open polymerization of tetrahydrofuran (THF) was investigated with glycerin or water as co-initiator, boron (tri) fluoride etherate (BF3·OEt2) as initiator, and a new type of polytetrahydrofuran triol (PTHF-T) and polytetrahydrofuran glycol (PTMG or PTHF-G) was synthethized. The factors that affect polymerization reaction, such as the amounts of glycerin, glycerin and water, water, reaction time, were discussed. The polymers were characterized by Fourier Transform Infrared Spectrometry (FTIR), gel permeation chromatography (GPC), viscosimetry, hydroxyl value. The degree of functionalization of PTHF varied linearly with the relative glycerin content in glycerin-water mixture. PTHF triol with a narrow molecular weight distribution and a higher yield was obtained when glycerin was used as co-initiator. The relationship between GPC and viscosimetry was obtained. Polytetrahydrofuran triol (PTHF-T) was used in the preparation of polyurethane rapid adsorption material.