Journal of Energy Chemistry
ISSN 1003-9953
     
能源化学(英文)

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Prof. Bao and co-workers, in their article on pages 257–263, reported a long-term stability test of Mo/HZSM-5 catalysts in methane dehydroaromatization (MDA) reaction with periodic CH4-H2 switch at 1033–1073 K for more than 1000 h. This optimized CH4-H2 switch offers a feasible approach to suppress coke deposition. Using H2 produced in MDA reaction as the regeneration gas, the CH4-H2 switch mode can serve as a valuable reference for future utilization of MDA process.


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2015 Vol.24 No.3, Published: 2015-05-15
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Methane dehydroaromatization with periodic CH4-H2 switch: A promising process for aromatics and hydrogen
Changyong Sun, Guangzong Fang, Xiaoguang Guo, Yuanli Hu, Shuqi Ma, Tianhua Yang, Jie Han, Hao Ma, Dali Tan, Xinhe Bao
2015 Vol. 24 (3): 257-263 [Abstract] ( 113 ) [HTML 1KB] [PDF] ( 0 )

Long-term stability test of Mo/HZSM-5-N catalysts (HZSM-5-N stands for nano-sized HZSM-5) in methane dehydroaromatization (MDA) reaction has been performed with periodic CH4-H2 switch at 1033-1073K for more than 1000h. During this test, methane conversion ranges from 13% to 16%, and mean yield to aromatics (i.e. benzene and naphthalene) exceeds 10%. N2-physisorption, XRD, NMR and TPO measurements were performed for the used Mo/HZSM-5 catalysts and coke deposition, and the results revealed that the periodic hydrogenation can effectively suppress coke deposition by removing the inert aromatic-type coke, thus ensuring Mo/HZSM-5 partly maintained its activity even in the presence of large amount of coke deposition. The effect of zeolite particle size on the catalytic activity was also explored, and the results showed that the nano-sized zeolite with low diffusion resistance performed better. It is recognized that the size effect was enhanced by reaction time, and it became more remarkable in a long-term MDA reaction even at a low space velocity.

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Carbide derived carbon electrode with natural graphite addition in magnesium electrolyte based cell for supercapacitor enhancements
Ramasamy Chandrasekaran, Jesús Palma, Marc Anderson
2015 Vol. 24 (3): 264-270 [Abstract] ( 95 ) [HTML 1KB] [PDF] ( 0 )

Herein, we have presented a supercapacitor based on carbide derived carbon (CDC) electrode with natural graphite (NG) addition. The capacitor was analyzed at 22℃ by cyclic voltammetry, galvanostatic charge-discharge and impedance techniques using a 0.5mol/L of magnesium (II) bis (trifluoro methanesulfonyl) imide (MgTFSI) in ethylene carbonate-propylene carbonate (EC:PC=1:1, v/v) as electrolyte. The results conclude that the CDC cell enhancements have been proven by the composite electrode (5%-30% NG to CDC) especially on the cell efficiency and voltage i.e., the CDC cell around 2.5V limit was improved. An obtainable specific capacitance, real power and energy density are 15F·g-1, 1.2 kW·kg-1 and 15 Wh·kg-1, respectively.

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Preparation of nanostructured mesoporous NiCo2O4 and its electrocatalytic activities for water oxidation
Genyan Hao, Wei Wang, Guofeng Gao, Qiang Zhao, Jinping Li
2015 Vol. 24 (3): 271-277 [Abstract] ( 100 ) [HTML 1KB] [PDF] ( 0 )

Nanostructured mesoporous NiCo2O4, Co3O4 and NiO spinel oxides were prepared through the hydroxide coprecipitation method using EG (ethylene glycol) as solvent without any template. The NiCo2O4 powders were analyzed by TGA, XRD, N2 adsorption-desorption, SEM and EDS. And the electrocatalytic properties of NiCo2O4/Ti, Co3O4/Ti and NiO/Ti electrodes for oxygen evolution in 0.1 mol/L KOH (pH=13) were tested by cyclic voltammetry, Tafel curves and electrolysis. The result shows that NiCo2O4/Ti electrode has higher electrocatalytic activity in oxygen evolution reaction than Co3O4/Ti and NiO/Ti electrodes. NiCo2O4/Ti electrode prepared at 350℃ has the highest apparent current density and the highest true current density. The Tafel slope of NiCo2O4/Ti electrode prepared at 350℃ is 68.49mV/dec.

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Effect of elemental molar ratio on the synthesis of higher alcohols over Co-promoted alkali-modified Mo2C catalysts supported on CNTs
Rohollah M. Kiai, Tahereh Nematian, Ahmad Tavasoli, Ali Karimi
2015 Vol. 24 (3): 278-284 [Abstract] ( 119 ) [HTML 1KB] [PDF] ( 0 )

A series of molybdenum carbide catalysts promoted by potassium and cobalt, supported on carbon nanotubes (CNTs) were prepared by carbothermal hydrogen reduction method using CNTs as a carbon precursor. Firstly, molybdenum and cobalt were loaded by co-precipitation method, and then potassium and additional molybdenum were impregnated to previous resultant. Different Mo/Co and K/Co molar ratio were used in catalyst synthesis. All the catalysts were characterized by ICP, BET, TEM, TPR, XRD and XPS, and the catalysts performances for higher alcohols synthesis (HAS) were investigated in a fixed-bed micro-reactor. The maximum selectivity to higher alcohols (C2+OH) was obtained at Mo/Co and K/Mo molar ratios of 1.66 and 0.6, respectively. XRD results confirmed the formation of K-Mo-C site and Co3Mo3C phase that might play important role in producing C2+OH.

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Phosphonated USY, a promising catalyst for the development of environmentally benign biodiesel (methyl acetate) process
Kakasaheb Y. Nandiwale, Gahana Gopal. C, Vijay V. Bokade
2015 Vol. 24 (3): 285-290 [Abstract] ( 90 ) [HTML 1KB] [PDF] ( 0 )

The present study focuses on the evaluation of the potential applicability of Ultra Stable Y (USY) and phosphonated USY (1 wt%-4 wt% phosphorous loading) as heterogeneous catalysts for biodiesel (methyl acetate) production. The synthesized catalysts were characterized by powder X-ray diffraction (XRD), Brunaer-Emmett-Teller (BET) surface area, total acidity by temperature-programmed desorption of ammonia (TPD-NH3) and Fourier Transform Infrared (FTIR) spectra. The performances of catalysts were evaluated for the transesterification of butyl acetate with methanol (a model reaction in biodiesel production). In view to obtain a maximum yield of methyl acetate, the optimization of process parameters such as reactant molar ratio, catalyst loading, reaction temperature and reaction time was performed. All the phosphonated USY catalysts showed higher catalytic activity than the parent USY, which can be attributed to the increase of total acidity due to phosphonation. 2 wt% P/USY (2% phosphorous loaded on USY) exhibited 92% methyl acetate yield with 100% selectivity, which was proved to be a potential catalyst for biodiesel production. The invented catalyst was found to be stable and reusable for five catalytic cycles, demonstrating that it might be a environmentally benign catalytic process.

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Effects of ultrasound on the desulfurization performance of hot coal gas over Zn-Mn-Cu supported on semi-coke sorbent prepared by high-pressure impregnation method
Xiaoyang Zhang, Xianrong Zheng, Peng Han, Ze Liu, Liping Chang
2015 Vol. 24 (3): 291-298 [Abstract] ( 90 ) [HTML 1KB] [PDF] ( 0 )

Zn-Mn-Cu/SC(U) sorbent was hydrothermally synthesized by ultrasound-assisted high-pressure impregnation method with semi-coke (SC) as support and the mixed solution of zinc nitrate, manganese nitrate and copper nitrate as active component precursors. The desulfurization performances of hot coal gas on the prepared sorbent at a mid-temperature of 500℃ were tested in fixed-bed reactor. Morphology and pore structure of the prepared sorbent were also characterized by TEM, N2 adsorption/desorption isotherms and XRD. For comparison, the sorbent of Zn-Mn-Cu/SC prepared by conventional high-pressure impregnation was also evaluated and characterized in order to study the effects of ultrasound treatment. Zn-Mn-Cu/SC(U) sorbent prepared by high-pressure impregnation under ultrasound-assisted condition showed a better desulfurization performance than Zn-Mn-Cu/SC. It could remove H2S from 1000×10-6 m3/m3 to 0.1×10-6 m3/m3 at 500℃ and maintained for 12.5h with the sulfur capacity of 7.74%, in which both the breakthrough time and sulfur capacity were about 32% and 51% higher than those of Zn-Mn-Cu/SC sorbent. The introduction of ultrasound during high-pressure impregnation process greatly improved the morphology and pore structure of the sorbent. The ultrasonic treatment made particle size of active components smaller and made them more evenly disperse on semi-coke support, which provided more opportunities to contact with H2S in coal-based gases. However, there were no any difference in compositions and existing forms of active components on the Zn-Mn-Cu/SC and Zn-Mn-Cu/SC(U) sorbents.

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Hydrogen production via steam reforming of bio-oil model compounds over supported nickel catalysts
Huaqing Xie, Qingbo Yu, Xin Yao, Wenjun Duan, Zongliang Zuo, Qin Qin
2015 Vol. 24 (3): 299-308 [Abstract] ( 105 ) [HTML 1KB] [PDF] ( 0 )

The steam reforming of four bio-oil model compounds (acetic acid, ethanol, acetone and phenol) was investigated over Ni-based catalysts supported on Al2O3 modified by Mg, Ce or Co in this paper. The activation process can improve the catalytic activity with the change of high-valence Ni (Ni2O3, NiO) to low-valence Ni (Ni, NiO). Among these catalysts after activation, the Ce-Ni/Co catalyst showed the best catalytic activity for the steam reforming of all the four model compounds. After long-term experiment at 700℃ and the S/C ratio of 9, the Ce-Ni/Co catalyst still maintained excellent stability for the steam reforming of the simulated bio-oil (mixed by the four compounds with the equal masses). With CaO calcinated from calcium acetate as CO2 sorbent, the catalytic steam reforming experiment combined with continuous in situ CO2 adsorption was performed. With the comparison of the case without the adding of CO2 sorbent, the hydrogen concentration was dramatically improved from 74.8% to 92.3%, with the CO2 concentration obviously decreased from 19.90% to 1.88%.

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Dissociation behavior of "dry water" C3H8 hydrate below ice point: Effect of phase state of unreacted residual water on a mechanism of gas hydrates dissociation
Andrey O Drachuk, Vladimir P Melnikov, Nadezhda S Molokitina, Anatoliy N Nesterov, Lev S Podenko, Aleksey M Reshetnikov, Andrey Yu Manakov
2015 Vol. 24 (3): 309-314 [Abstract] ( 83 ) [HTML 1KB] [PDF] ( 0 )

The results on a dissociation behavior of propane hydrates prepared from "dry water" and contained unreacted residual water in the form of ice inclusions or supercooled liquid water (water solution of gas) were presented for temperatures below 273K. The temperature ramping or pressure release method was used for the dissociation of propane hydrate samples. It was found that the mechanism of gas hydrate dissociation at temperatures below 273K depended on the phase state of unreacted water in the hydrate sample. Gas hydrates dissociated into ice and gas if the ice inclusions were in the hydrate sample. The samples of propane hydrates with inclusions of unreacted supercooled water only (without ice inclusions) dissociated into supercooled water and gas below the pressure of the supercooled water-hydrate-gas metastable equilibrium.

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Production of high-purity hydrogen by sorption-enhanced steam reforming process of methanol
Xiang Wu, Sufang Wu
2015 Vol. 24 (3): 315-321 [Abstract] ( 100 ) [HTML 1KB] [PDF] ( 0 )

The sorption-enhanced steam reforming process of methanol (SESRP-MeOH) to produce high-purity H2 was thermodynamically and experimentally studied. Thermodynamic calculations showed that at a CO2 adsorption ratio of 95%, product gas contains 98.36% H2, 32.8ppm CO under temperature of 130℃ and steam-to-methanol (S/M) molar ratio of 2. However, without adsorption-enhanced, the product gas contains nearly 74.99% H2 with 24.96% CO2 and 525ppm CO. To verify the thermodynamic calculation results, experiments were performed in a fixed-bed reactor loaded with commercial CuO/ZnO/Al2O3 methanol reforming catalyst and 22% K2CO3-promoted hydrotalcite as CO2 adsorbent. Experimental results showed that 99.61% H2 could be obtained by SESRP-MeOH at reaction temperature of 230℃ and S/M of 2. Under the same CH3OH conversion, the reaction temperature decreased by almost 50℃ and H2 concentration increased of more than 20% using SESRP-MeOH compared with solely steam reforming of methanol. The characterization of the adsorbent and catalyst showed that the adsorbent showed good stability while the catalyst was seriously sintered under the high regeneration temperature of the adsorbent.

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CO2 adsorption performance of different amine-based siliceous MCM-41 materials
Zhilin Liu, Yang Teng, Kai Zhang, Honggang Chen, Yongping Yang
2015 Vol. 24 (3): 322-330 [Abstract] ( 85 ) [HTML 1KB] [PDF] ( 0 )

A series of amine-based adsorbents were synthesized using siliceous MCM-41 individually impregnated with four different amines (ethylenediamine (EDA), diethylenetriamine (DETA), tetraethylenepentamine (TEPA) and pentaethylenehexamine (PEHA)) to study the effect of amine chain length and loading weight on their CO2 adsorption performances in detail. The adsorbents were characterized by FT-IR, elemental analysis, and thermo-gravimetric analysis to confirm their structure properties. Thermo-gravimetric analysis was also used to evaluate the CO2 adsorption performance of adsorbents. Longer chain amine-based materials can achieve higher amine loadings and show better thermal stability. The CO2 adsorption capacities at different temperatures indicate that the CO2 adsorption is thermodynamically controlled over EDA-MCM41 and DETA-MCM41, while the adsorption over TEPA-MCM41 and PEHA-MCM41 is under kinetic control at low temperature. The chain length of amines affects the CO2 adsorption performance and the adsorption mechanism significantly. The results also indicate that CO2 adsorption capacity can be enhanced despite of high operation temperatures, if appropriate amines (TEPA and PEHA) are applied. However, adsorbents with short chain amine exhibit higher adsorption and desorption rates due to the collaborative effect of rapid reaction mechanisms of primary amines and less diffusion resistance of shorter chain length amines.

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Detailed investigation of optimized alkali catalyzed transesterification of Jatropha oil for biodiesel production
Waqas Ahmed, Muhammad Faizan Nazar, Syed Danish Ali, Usman Ali Rana, Salah Ud-Din Khan
2015 Vol. 24 (3): 331-336 [Abstract] ( 90 ) [HTML 1KB] [PDF] ( 0 )

The non-edible oils are believed to be one of the major feedstock for the production of biodiesel in future. In the present study, we investigated the production of Jatropha oil methyl esters (JOMEs) via alkali-catalyzed transesterification route. The biophysical characteristics of Jatropha oil were found within the optimal range in accordance with ASTM standards as a substitute diesel fuel. The chemical composition and production yield of as-synthesized biodiesel were confirmed by various analytical techniques such as FT-IR, 1H NMR, 13C NMR and gas chromatography coupled with mass spectrometry. A high percentage conversion, ~96.09%, of fatty acids into esters was achieved under optimized transesterification conditions with 6:1oil to methanol ratio and 0.9 wt% NaOH for 50min at ~60℃. Moreover, twelve fatty acids methyl esters (FAME) were quantified in the GC/MS analysis and it was interesting to note that the mass fragmentation pattern of saturated, monounsaturated and diunsaturated FAME was comparable with the literature reported values.

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Synergetic influence of ex-situ camphoric carbon nano-grafting on lithium titanates for lithium ion capacitors
Amruthalakshmi Vijayakumar, Ranjusha Rajagopalan, Anoop S. Sushamakumariamma, Jickson Joseph, Amrutha Ajay, Shantikumar V Nair, Deepak Krishna M. S, Avinash Balakrishnan
2015 Vol. 24 (3): 337-345 [Abstract] ( 92 ) [HTML 1KB] [PDF] ( 0 )

The present study provides detailed experimental results on the synthesis and characterization of carbonized lithium titanate spinel (LTO) composites as electrode materials for lithium ion capacitor. The LTO particles were grafted with a porous carbon layer obtained from the pyrolysis of camphor. The graphitic nature of the carbon was confirmed through Raman spectroscopy. The relative contributions from the capacitive and diffusion controlled processes underlying these electrodes were mathematically modeled. Electron transport mechanism underlying these electrodes was determined by measuring the work functions (φ) of LTO and carbon grafted LTO using ultraviolet photoelectron spectroscopy. These carbon grafted LTO composites exhibited an energy density of 330 mWh·L-1 and a peak power density of 2.8kW·L-1, when employed as electrodes in coin cells with excellent cycling stability at the end of 4000 cycles.

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Electrochemical performance of Klason lignin as a low-cost cathode-active material for primary lithium battery
Sergey V Gnedenkov, Denis P Opra, Ludmila A Zemnukhova, Sergey L Sinebryukhov, Iliya A Kedrinskii, Olga V Patrusheva, Valentin I Sergienko
2015 Vol. 24 (3): 346-352 [Abstract] ( 77 ) [HTML 1KB] [PDF] ( 0 )

A few classes of organic compounds are promising electrode-active materials due to their high power and energy densities, low cost, environmental friendliness, and functionality. In the present work, the possibility of using Klason lignin extracted from buckwheat husks as a cathode-active material for a primary lithium battery has been investigated for the first time. The reaction mechanism in the lithium/lignin electrochemical cell was suggested based on the deep galvanostatic discharge (up to 0.005 V) data and cyclic voltammetry results. The dependence of the electrochemical behavior of the Klason lignin on the milling degree was evaluated. The maximum specific capacity of the lignin is equal to 600 mAh·g-1 at a discharge current density of 75 μA·cm-2. Beneficial effect of the thermal treatment of the Klason lignin cathode at 250℃ on the cell performance was established. It was found that the discharge capacity of the cell increased by 30% in the range from 3.3 to 0.9V for the treated cathode material. These results demonstrate the prospects of using Klason lignin-based electrochemical cells as low-rate primary power sources.

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Direct synthesis of propylene carbonate from propylene and carbon dioxide catalyzed by quaternary ammonium heteropolyphosphatotungstate-TBAB system
Gongda Zhao, Yi Zhang, Hengyun Zhang, Jun Li, Shuang Gao
2015 Vol. 24 (3): 353-358 [Abstract] ( 77 ) [HTML 1KB] [PDF] ( 0 )

In this paper, we have developed a highly efficient method for the direct preparation of propylene carbonate from propylene and carbon dioxide (CO2) using quaternary ammonium heteropolyphosphatotungstate-quaternary ammonium halide catalytic system with anhydrous hydrogen peroxide as an oxidant through one-pot two-step process. The effects of the amount of tetrabutylammonium bromide (TBAB), the concentration of hydrogen peroxide and other reaction conditions were investigated. The catalyst system gave an optimum propylene oxide yield (91%) at 75℃ in oxidation step and the highest propylene carbonate yield (99%) at 140℃ and 3.0MPa in cycloaddition step. Based on the results, a reaction mechanism has been proposed.

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Synthesis of Nafion®-stabilized Pt nanoparticles to improve the durability of proton exchange membrane fuel cell
Xin Sun, Hongfeng Xu, Quanren Zhu, Lu Lu, Hong Zhao
2015 Vol. 24 (3): 359-365 [Abstract] ( 84 ) [HTML 1KB] [PDF] ( 0 )

Nafion®-stabilized Pt nanoparticle colloidal solution is synthesized through ethylene glycol reduction. Pt/Nafion® added with carbon black as electric conduction material (labeled Pt/Nafion®-XC72) shows excellent electrochemical property compared with Pt/C. After a 300-cycle discharging durability test, the cell performance of membrane electrode assembly (MEA) with the Pt/Nafion®-XC72 and Pt/C catalysts indicates a 29.9% and 92.2% decrease, respectively. The charge transfer resistances of Pt/Nafion®-XC72 and Pt/C increase by 27.2% and 101.9%, respectively. The remaining electrochemically active surface area of Pt is about 61.7% in Pt/Nafion®-XC72 and about 38.1% in Pt/C after the durability test. The particle size of Pt/C increases from about 5.1nm to about 10.8nm but only from 3.6nm to 5.8nm in the case of Pt/Nafion®-XC72. These data suggest that Pt/Nafion®-XC72 as a catalyst can enhance the durability of PEMFCs compared with Pt/C.

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CO2 reforming of glycerol over La-Ni/Al2O3 catalyst: A longevity evaluative study
Kah Weng Siew, Hua Chyn Lee, Maksudur R. Khan, Jolius Gimbun, Chin Kui Cheng
2015 Vol. 24 (3): 366-373 [Abstract] ( 77 ) [HTML 1KB] [PDF] ( 0 )

This paper reports on the longevity of glycerol-dry (CO2) reforming over the lanthanum (La) promoted Ni/Al2O3 catalysts. The XRD results showed that the Ni particle was well-dispersed in the presence of La promoter. In addition, via the NH3-TPD analysis, it was found that the La promoter has reduced the acidity of Ni catalyst which may have explained the mitigation of carbon laydown. It was determined that the 3.0 wt% La-promoted Ni/Al2O3 catalyst possessed the largest BET specific surface area of 97m2·g-1. Consequently, it yielded the best catalytic longevity performance with conversion attained more than 90%, even after 72h of reaction duration. Significantly, it can be confirmed that the presence of CO2 during the glycerol dry reforming was essential in reducing carbon deposition, most likely via gasification pathway. This has ensured a stability of catalytic activity for a long reaction period (72 h).

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Bimonthly
(Started in 1992)
Renamed from JNGC in 2013

ISSN 2095-4956
CN 21-1585/O4

Editors-in-Chief
Xinhe Bao
Alexis T. Bell


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Editorial Office of
Journal of Energy Chemistry

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Dalian Institute of
Chemical Physics, CAS

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