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1.
The design of supported Co‐based Fischer–Tropsch (F–T) catalysts with suitable reducibility, dispersion, loading, and nanoparticle structure is necessary so that high catalytic activity and selectivity for C5+ hydrocarbons can be achieved. Herein, we report that pyrolyzing a Co‐metal–organic framework‐71 precursor can provide porous carbon‐supported Co catalysts with completely reduced, well‐dispersed face‐centered cubic (FCC) Co nanoparticles (~10 nm in average size). The catalysts can be further tailored dimensionally by doping with Si species, and the FCC Co nanoparticles can be partially transformed into hexagonal close‐packed Co via a Co2C intermediate. All the as‐prepared catalysts had extremely high Co site density (>3.5 × 10?4 mol/g‐cat.) because they had a high number of Co active sites and low mass. Aside from having high F–T activity and C5+ selectivity, with diesel fuels being the main constituents, they showed unprecedentedly high C5+ space time yields (up to 1.45 g/(g‐cat. h)) as compared to conventional Co catalysts. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2935–2944, 2017  相似文献   

2.
J. Qiao  N. Zhang  Z. Wang  Y. Mao  K. Sun  Y. Yuan 《Fuel Cells》2009,9(5):729-739
CeO2‐Ni/YSZ anodes for methane direct oxidation were prepared by the vacuum mix‐impregnation method. By this method, NiO and CeO2 are obtained from nitrate decomposition and high temperature sintering is avoided, which is different from the preparation of conventional Ni‐yttria‐stabilised zirconia(YSZ) anodes. Impregnating CeO2 into the anode can improve the cell performance, especially, when CH4 is used as fuel. The investigation indicated that CeO2‐Ni/YSZ anodes calcined at higher temperature exhibited better stability than those calcined at lower temperature. Under the testing temperature of 1,073 K, the anode calcined at 1,073 K exhibited the best performance. The maximum power density of a cell with a 10 wt.‐%CeO2‐25 wt.‐%Ni anode calcined at 1,073 K reached 480 mW cm–2 after running on CH4 for 5 h. At the same time, high discharge current favoured cell operation on CH4 when using these anodes. No obvious carbon was found on the CeO2‐Ni anode after testing in CH4 as revealed from SEM and corresponding linear EDS analysis. In addition, cell performance decreased at the beginning of discharge testing which was attributed to the anode microstructure change observed with SEM.  相似文献   

3.
The anodes for direct utilisation of hydrocarbon fuels have been developed by using Cu/Ceria‐based nano‐composite powders. The CuO/GDC/YSZ–YSZ or CuO/GDC‐GDC nano‐composite powders were synthesised by coating nano‐sized CuO and CeO2 particles on the YSZ or GDC core particles selectively by the Pechini process. Their microstructures and electrical properties have been investigated with long‐term stability in reactive gases of dry methane and air. The anodes fabricated using Cu‐based nano‐composite anodes showed almost no carbon deposition until 500 h in dry CH4 atmosphere. The type of an electrolyte‐supported single cell in conjunction with the Cu/Ceria‐based anode must be selected together for the low melting temperature of Cu/CuO. The GDC electrolyte supported unit cell with the Cu/GDC–GDC anode showed the maximum power density of 0.1 Wcm–2 and long‐term stability for more than 500 h under electronic load of 0.05 Acm–2 at 650 °C in dry methane atmosphere.  相似文献   

4.
Anode microstructure has a great influence on the cell performance. The addition of urea into impregnated solution has been proposed to tailor the distribution and/or morphology of Cu when fabricating the Cu-based anodes by impregnation method. While the previous reports demonstrated the single cell performance has not been improved in this route, in this paper, fuel cells with Cu/yttria-stabilized zirconia (YSZ) and Cu–CeO2/YSZ anodes were fabricated and evaluated with improved outputs. The microstructure of Cu in anodes appeared significantly different after the addition of urea. The electronic conductivity obtained from the anodes impregnated with adding urea was twice as high as the ones without. Performance of fuel cells increases by 12% while operating on H2 at 700 °C upon adding urea. Furthermore, the performance improvement was more prominent when such method was adopted in the fabrication of Cu–CeO2/YSZ composite anodes. Cells with Cu–CeO2/YSZ composite anodes operating in H2 at 700 °C exhibited an increase of cell performance by 37%, from 337 to 462 mW cm−2, by simply adding urea to the impregnated solution. And the performance enhancement for such fuel cells is also as high as 28% when using CH4 as fuel.  相似文献   

5.
A series of imbiber terpolymer beads was prepared by radical suspension copolymerization of styrene–divinylbenzene with varied contents of acrylated vinyl monomers, n‐butyl acrylate and 2‐ethyl hexyl acrylate, as the third comonomer. A DVB content of 6 wt % and a mixture of 60/40 wt % toluene/n‐heptane as the diluent were used throughout this study. The influence of acrylated vinyl comonomers on bead properties and swelling properties was investigated. The imbiber beads are capable of absorption and desorption of organic solvents having solubility parameters in the range of 14.9–20.9 (MPa)1/2. Styrenic imbiber beads were swelled in a toluene/n‐heptane mixture of 50% by volume and the kinetics of absorption was studied. The imbiber beads could absorb the toluene/n‐heptane mixture completely within 20 min and yielded a maximum swelling ratio of 6.8. The diffusion coefficient values of these beads were in the range of 6.40 × 10−6 to 1.52 × 10−5 cm2 s−1. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 504–516, 2001  相似文献   

6.
Anodes for Solid Oxide Fuel Cell that is capable of directly using hydrocarbon without external reforming have been of great interest recently. In this paper, a three‐layer structure anode running on methane is fabricated by tape casting and screen printing method. The slurry of catalyst layer Cu‐LSCM‐CeO2 (with weight ratios of 1.5:7.0:1.5, 2.0:7.0:1.0, 2.15:7.0:0.85 and 2.25:7.0:0.75, weight ratios of Cu/CeO2 is 1:1, 2:1, 2.5:1 and 3:1, respectively) is screen‐printed on LSCM‐YSZ support layer and Ni‐ScSZ active layer. Thus, LSCM‐YSZ/Ni‐ScSZ anodes with Cu‐LSCM‐CeO2 catalyst layer (denoted as LSCM‐YSZ1010, LSCM‐YSZ2010, LSCM‐YSZ2510 and LSCM‐YSZ3010, respectively) are obtained. Single cells with three‐layer structure anode are also fabricated and measured, of which the maximum power density reaches 491 and 670 mW cm−2 for the cell with LSCM‐YSZ2510 anode running on methane at 750 °C and 800 °C, respectively. No significant degradation in performance has been observed after 240h of cell testing when LSCM‐YSZ2510 anode is exposed to methane at 750 °C. Very little carbon deposition is detected on the anode, suggesting that carbon deposition is limited during cell operation. Consequently, Cu‐LSCM‐CeO2 catalyst layer on the surface of LSCM‐YSZ support layer makes it possible to have good stability for long‐term operation in methane due to very little carbon deposition.  相似文献   

7.
Q. Li  V. Thangadurai 《Fuel Cells》2009,9(5):684-698
In this paper, we report the synthesis, structure and electrical conductivity of Mo‐doped compounds with a nominal chemical formula of Ce1–xMoxO2+δ (x = 0.05, 0.07, 0.1) (CMO). The formation of fluorite‐like structure with a small amount of Ce8Mo12O49 impurity (JCPDS Card No. 31‐0330) was confirmed using a powder X‐ray diffraction (PXRD). The fluoride‐type structure was retained under wet H2 and CH4 atmospheres at 700 and 800 °C, while diffraction peaks due to metal Mo were observed in dry H2 under the same condition. AC impedance measurements showed that the total conductivity increases with increasing Mo content in CMO, and among the investigated samples, Ce0.9Mo0.1O2+δ exhibited the highest electrical conductivity with a value of 2.8 × 10–4 and 5.08 × 10–2 S cm–1 at 550 °C in air and wet H2, respectively. The electrical conductivity was found to be nearly the same, especially at high temperatures, in air, O2 and N2. Chemical compatibility of Ce0.9Mo0.1O2+δ with 10 mol‐% Y2O3 stabilised ZrO2 (YSZ) and Ce0.9Gd0.1O1.95 (CGO) oxide ion electrolytes in wet H2 was evaluated at 800–1,000 °C, using PXRD and EDX analyses. PXRD showed that CMO was found to react with YSZ electrolyte at 1,000 °C. The area specific polarisation resistance (ASPR) of Ce0.9Mo0.1O2+δ on YSZ was found to be 8.58 ohm cm2 at 800 °C in wet H2.  相似文献   

8.
Porous composite anodes consisting of a yttria-stabilized zirconia (YSZ) backbone that was impregnated with CeO2 and various amounts of metallic components including Cu, Co and Pd were fabricated. The performance of these anodes was then tested in a solid oxide water electrolysis cell under conditions where the anode was exposed to the reducing gasses H2, CH4 and CO. The reducing gasses were used to decrease the electrochemical potential of the cell and increase overall efficiency. The results of this study show that Cu–CeO2–YSZ anodes have low catalytic activity for the oxidation of CO and CH4 and are not very effective in lowering the cell potential while operating in the reducing gas assisted mode. The addition of Co to the Cu–CeO2–YSZ anode resulted in a modest increase in the catalytic activity and enhanced the thermal stability of the anode. A Pd–C–CeO2–YSZ anode was found to have the highest catalytic activity of those tested and gave the largest reductions in the operating potential of the solid oxide electrolysis cell.  相似文献   

9.
Thermogravimetric analysis (TGA) has been used to investigate the carburization kinetics of Mo–W sulfide using an H2:C3H8 feed mixture. The effect of heating rate over the range 1–10 K min?1 showed that up to four different carburized products may be formed but the critical (peak) temperature for formation of these species and the amount (peak height) of each species formed are highly dependent on the heating rate employed. The critical temperature increased linearly with heating rate for each of the four products. The four TGA peaks corresponding to the four phase transformation species are consistent with XRD identifiable species, namely; α‐Mo2C, β‐Mo2C, W and MoC1?x. Isothermal conversion–time data at three different temperatures are described by a reaction‐controlled shrinking core model implicating a first‐order dependency on the H2:C3H8 ratio. The reaction exhibited fractional order dependence on the metal sulfide concentration, the associated global activation energy estimated as 227 kJ mol?1 is representative of a non‐catalytic gas–solid reaction. Copyright © 2004 Society of Chemical Industry  相似文献   

10.
The reaction of the Cu(II) bis N,O‐chelate‐complexes of L‐2,4‐diaminobutyric acid, L‐ornithine and L‐lysine {Cu[H2N–CH(COO)(CH2)nNH3]2}2+(Cl)2 (n = 2–4) with terephthaloyl dichloride or isophthaloyl dichloride gives the polymeric complexes {‐OC–C6H4–CO–NH–(CH2)n–CH(nh2)(COO)Cu(OOC)(NH2)CH–CH2)n–NH‐}x 1 – 5 . From these the metal can be removed by precipitation of Cu(II) with H2S. The liberated ω,ω′‐N,N′‐diterephthaloyl (or iso‐phthaloyl)‐diaminoacids 6 – 10 react with [Ru(cymene)Cl2]2, [Ru(C6Me6)Cl2]2, [Cp*RhCl2]2 or [Cp*IrCl2]2 to the ligand bridged bis‐amino acidate complexes [Ln(Cl)M–(OOC)(NH2)CH–(CH2)nNH–CO]2–C6H4 11 – 14 .  相似文献   

11.
In this work, La0.6Sr0.4CoO3 – δ/Ce1 – xGdxO2 – δ (LSC/GDC) composite cathodes are investigated for SOFC application at intermediate temperatures, especially below 700 °C. The symmetrical cells are prepared by spraying LSC/GDC composite cathodes on a GDC tape, and the lowest polarisation resistance (Rp) of 0.11 Ω cm2 at 700 °C is obtained for the cathode containing 30 wt.‐% GDC. For the application on YSZ electrolyte, symmetrical LSC cathodes are fabricated on a YSZ tape coated on a GDC interlayer. The impact of the sintering temperature on the microstructure and electrochemical properties is investigated. The optimum temperature is determined to be 950 °C; the corresponding Rp of 0.24 Ω cm2 at 600 °C and 0.06 Ω cm2 at 700 °C are achieved, respectively. An YSZ‐based anode‐supported solid oxide fuel cell is fabricated by employing LSC/GDC composite cathode sintered at 950 °C. The cell with an active electrode area of 4 × 4 cm2 exhibits the maximum power density of 0.42 W cm–2 at 650 °C and 0.54 W cm–2 at 700 °C. More than 300 h operating at 650 °C is carried out for an estimate of performance and degradation of a single cell. Despite a decline at the beginning, the stable performance during the later term suggests a potential application.  相似文献   

12.
This research is aimed to improve the activity and stability of ternary alloy Pt–Ru–Ni/C catalyst. A novel anodic catalyst for direct methanol fuel cell (DMFC), carbon supported Pt–Ru–Ni–P nanoparticles, has been prepared by chemical reduction method by using NaH2PO2 as a reducing agent. One glassy carbon disc working electrode is used to test the catalytic performances of the homemade catalysts by cyclic voltammetric (CV), chronoamperometric (CA) and amperometric it measurements in a solution of 0.5 mol L–1 H2SO4 and 0.5 mol L–1 CH3OH. The compositions, particle sizes and morphology of home‐made catalysts are evaluated by means of energy dispersive analysis of X‐ray (EDAX), X‐ray diffraction (XRD) and transmission electron micrographs (TEM), respectively. TEM images show that Pt–Ru–Ni–P nanoparticles have an even size distribution with an average diameter of less than 2 nm. The results of CV, CA and it curves indicate that the Pt–Ru–Ni–P/C catalyst shows significantly higher activity and stability for methanol electrooxidation due to the presence of non‐metal phosphorus in comparison to Pt–Ru–Ni/C one. All experimental results indicate that the addition of non‐metallic phosphorus into the Pt–Ru–Ni/C catalyst has definite value of research and practical application for enhancing the performance of DMFC.  相似文献   

13.
Gas–liquid chromatography is used to study the thermodynamic interactions between polystyrene and n‐alkanes (C6–C10). Polystyrene is used as a stationary phase with n‐alkanes as the probe molecules. Retention times and specific retention volumes are measured over the temperature interval of 60 to 170°C. Partial molar free energy of mixing, polymer–solvent interaction parameter, glass‐transition temperature, and solubility parameter of polystyrene at infinite dilution are calculated. Experimental results are discussed in terms of the theoretical calculations and size of the probe molecules. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1291–1298, 2001  相似文献   

14.
The kinetics of CO hydrogenation over coprecipitated 36 wt% Co/Al2O3 was studied in a fixed-bed microreactor at atmospheric pressure. Intrinsic kinetic data were obtained in the initial rate region using four different CO concentrations and two different H2/CO ratios over the 473–523 K temperature range. The surface carbide mechanism with dissociative adsorption of hydrogen as the rate controlling step gives the most plausible kinetic model among the eight different models tested. C1–C4 production rates are found to be strongly influenced by temperature, and optimum C1–C4 hydrocarbon selectivity is obtained at 508 K. The activation energy for CO consumption and CH4 formation are calculated as 74±2 kJ mol−1 and 84±2 kJ mol−1 respectively. ©1997 SCI  相似文献   

15.
Amine‐terminated poly(arylene ether sulfone)–carboxylic‐terminated butadiene‐acrylonitrile–poly(arylene ether sulfone) (PES‐CTBN‐PES) triblock copolymers with controlled molecular weights of 15,000 (15K) or 20,000 (20K) g/mol were synthesized from amine‐terminated PES oligomer and commercial CTBN rubber (CTBN 1300x13). The copolymers were utilized to modify a diglycidyl ether of bisphenol A epoxy resin by varying the loading from 5 to 40 wt %. The epoxy resins were cured with 4,4′‐diaminodiphenylsulfone and subjected to tests for thermal properties, plane strain fracture toughness (KIC), flexural properties, and solvent resistance measurements. The fracture surfaces were analyzed with SEM to elucidate the toughening mechanism. The properties of copolymer‐toughened epoxy resins were compared to those of samples modified by PES/CTBN blends, PES oligomer, or CTBN. The PES‐CTBN‐PES copolymer (20K) showed a KIC of 2.33 MPa m0.5 at 40 wt % loading while maintaining good flexural properties and chemical resistance. However, the epoxy resin modified with a CTBN/8K PES blend (2:1) exhibited lower KIC (1.82 MPa m0.5), lower flexural properties, and poorer thermal properties and solvent resistance compared to the 20K PES‐CTBN‐PES copolymer‐toughened samples. The high fracture toughness with the PES‐CTBN‐PES copolymer is believed to be due to the ductile fracture of the continuous PES‐rich phases, as well as the cavitation of the rubber‐rich phases. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1556–1565, 2002; DOI 10.1002/app.10390  相似文献   

16.
The synthesis times required to produce high energy density compounds (C2B4H2)n and (C2B10H4)n by gas phase pyrolysis of the carboranes C2B4H6 and C2B10H12, respectively, have been measured at 1150–2000 K and carborane pressures of (0.3–3.0)⋅10−3 MPa. Kinetic model simulations of the synthesis have been performed. The temperatures, carborane pressures, and synthesis times required to produce small‐scale (C2B4H2)n and (C2B10H4)n particles of 10 to 30 nm diameter are determined.  相似文献   

17.
For hydrogen generation from alkaline sodium borohydride (NaBH4) solution, Co–Fe–B catalysts with different Co/(Co + Fe) molar ratios (χCo) were prepared by the chemical reduction of CoCl2 and FeCl3 ethanol solution with KBH4 solution. The X‐ray diffraction (XRD) and scanning electron microscopy (SEM) analyses revealed that the as‐prepared Co–Fe–B catalysts were in amorphous form and ultrafine. The hydrogen generation measurements showed that as‐prepared Co–B and Co–Fe–B catalysts exhibited excellent catalytic activity. Co–Fe–B with the Co/(Co + Fe) molar ratio (χCo) of 0.85 was the best. Its maximum hydrogen generation rate at 298 K was 4,310 mL min–1 g–1, while the Co–B was 2,773 mL min–1 g–1. The enhanced activity could be attributed to large active surface area, electron transfer from B and Fe to active Co sites, and improvement in the dispersion of Co–B with Fe2O3. The activation energy of Co–Fe–B catalyst with the molar ratio χCo = 0.85 was decreased to 29.09 kJ mol–1 as compared to 30.85 kJ mol–1 obtained with Co–B.  相似文献   

18.
The series of bimetallic complexes, [(η5‐C5Me5)Zr(Me)2]2 [N(t‐Bu)C(Me)N (CH2)n NC(Me)N(t‐Bu)] 3 (n=8), 4 (n=6), and 5 (n=4) were prepared in high yield through a simple, one‐pot synthesis involving 2 equiv. of in situ generated (η5‐C5Me5)Zr(Me)3 and the corresponding bis‐carbodiimide, (t‐Bu)NCN (CH2)n NCN(t‐Bu). Compounds 3 – 5 were found to be highly isoselective for the living Ziegler–Natta polymerization of propene upon 100% activation using 2 equiv. of the borate co‐initiator, [PhNHMe2] [B(C6F5)4] ( 2 ), with the degree of stereoselectivity decreasing slightly as the two metal centers are brought closer together [cf., 3 (σ=0.92)> 4 (σ=0.91)> 5 (σ=0.89)]. Under conditions of sub‐stoichiometric activation by 2 , all three bimetallic initiators, 3 – 5 , were found to engage in degenerative transfer living Ziegler–Natta polymerization involving rapid and reversible methyl group transfer between active, (cationic) and dormant, (neutral) methyl, polymeryl zirconium centers. Under these conditions, the frequency of mr triad stereoerror incorporation into the polypropene (PP) microstructure decreases as the two metal centers are brought closer together as a result of increasing barriers for metal‐centered epimerization within the neutral metal site due to correspondingly greater non‐bonded steric interactions vis‐à‐vis mononuclear 1 .  相似文献   

19.
J. Li  C. Zhong  X. Meng  H. Wu  H. Nie  Z. Zhan  S. Wang 《Fuel Cells》2014,14(6):1046-1049
The high‐temperature solid oxide electrolysis cell (SOEC) is one of the most promising devices for hydrogen mass production. To make SOEC suitable from an economical point of view, each component of the SOEC has to be optimized. At this level, the optimization of the oxygen electrode is of particular interest since it contributes to a large extent to the cell polarization resistance. The present paper is focused on an alternative oxygen electrode of Zr0.84Y0.16O2–δ‐Sr2Fe1.5Mo0.5O6–δ (YSZ‐SFM). YSZ‐SFM composite oxygen electrodes were fabricated by impregnating the YSZ matrix with SFM, and the ion‐impregnated YSZ‐SFM composite oxygen electrodes showed excellent performance. For a voltage of 1.2 V, the electrolysis current was 223 mA cm−2, 327 mA cm−2 and 310 mA cm−2 at 750 °C for the YSZ‐SFM10, YSZ‐SFM20, and YSZ‐SFM30 oxygen electrode, respectively. A hydrogen production rate as high as 11.46 NL h−1 has been achieved for the SOEC with the YSZ‐SFM20 electrode at 750 °C. The results demonstrate that YSZ‐SFM fabricated by impregnating the YSZ matrix with SFM is a promising composite electrode for the SOEC.  相似文献   

20.
The main objective of this study is to predict the performance of an industrial‐scale (ID = 5.8 m) slurry bubble column reactor (SBCR) operating with iron‐based catalyst for Fischer–Tropsch (FT) synthesis, with emphasis on catalyst deactivation. To achieve this objective, a comprehensive reactor model, incorporating the hydrodynamic and mass‐transfer parameters (gas holdup, εG, Sauter‐mean diameter of gas bubbles, d32, and volumetric liquid‐side mass‐transfer coefficients, kLa), and FT as well as water gas shift reaction kinetics, was developed. The hydrodynamic and mass‐transfer parameters for He/N2 gaseous mixtures, as surrogates for H2/CO, were obtained in an actual molten FT reactor wax produced from the same reactor. The data were measured in a pilot‐scale (0.29 m) SBCR under different pressures (4–31 bar), temperatures (380–500 K), superficial gas velocities (0.1–0.3 m/s), and iron‐based catalyst concentrations (0–45 wt %). The data were modeled and predictive correlations were incorporated into the reactor model. The reactor model was then used to study the effects of catalyst concentration and reactor length‐to‐diameter ratio (L/D) on the water partial pressure, which is mainly responsible for iron catalyst deactivation, the H2 and CO conversions and the C5+ product yields. The modeling results of the industrial SBCR investigated in this study showed that (1) the water partial pressure should be maintained under 3 bars to minimize deactivation of the iron‐based catalyst used; (2) the catalyst concentration has much more impact on the gas holdup and reactor performance than the reactor height; and (3) the reactor should be operated in the kinetically controlled regime with an L/D of 4.48 and a catalyst concentration of 22 wt % to maximize C5+ products yield, while minimizing the iron catalyst deactivation. Under such conditions, the H2 and CO conversions were 49.4% and 69.3%, respectively, and the C5+ products yield was 435.6 ton/day. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3838–3857, 2015  相似文献   

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