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

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Prof. Zhang and coworkers, in their article on pages 1-8, report the effects of pore size on the performance of ultra-high surface area nanoporous carbon for high-pressure hydrogen storage. Nanoporous carbon having a distribution of pore sizes was prepared, and the impact of pore size on hydrogen storage performance at different pressures and temperatures was investigated. This work provides a systematic understanding for improving the hydrogen storage capacity of carbon-based materials for on-board applications.


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2015 Vol.24 No.1, Published: 2015-01-23
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Pore size effects of nanoporous carbons with ultra-high surface area on high-pressure hydrogen storage
Zhen Geng, Cunman Zhang, Dabin Wang, Xiangyang Zhou, Mei Cai
2015 Vol. 24 (1): 1-8 [Abstract] ( 302 ) [HTML 1KB] [PDF] ( 0 )

In this work, the morphologies and pore structures of a series of corncob-derived activated carbons and zeolite templated carbon with ultrahigh surface area were carefully investigated by SEM, HRTEM and N2-sorption characterization technologies. The high-pressure hydrogen uptake performance was analyzed using standard Pressure-Composition-Temperature apparatus in order to study the pore size effects on hydrogen uptake. These as-obtained porous carbons showed different characteristics of pore size distribution as well as specific surface area. The results indicate that the most effective pores for adsorbing hydrogen depended on the storage pressure. These ultramicropores (0.65-0.85 nm) could be the most effective pores on excess H2 uptake at 1 bar, however, micropores (0.85-2 nm) would play a more important role in excess H2 uptake at higher pressure at 77 K. At room temperature, pore size effects on H2 uptake capacity were very weak. Both specific surface area and total pore volume play more important roles than pore size for H2 uptake at room temperature, which was clearly different from that at 77 K. For applications in future, the corncob-derived activated carbons can be more available than zeolite templated carbons at 77 K. Element doping enhanced hydrogen uptake could be main research direction for improving H2 uptake capacity at room temperature.

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Inhibiting effect of tungstic compounds on glucose hydrogenation over Ru/C catalyst
Junying Zhang, Baolin Hou, Xuefei Wang, Zhenlei Li, Aiqin Wang, Tao Zhang
2015 Vol. 24 (1): 9-14 [Abstract] ( 249 ) [HTML 1KB] [PDF] ( 0 )

The effect of acid component including various conventional acids and tungstic compounds on glucose hydrogenation over a series of binary catalyst system containing Ru/C catalyst was investigated. The results showed that HCl, H2SO4, H3BO3, H3PO4, and HNO3 had negligible effect, while all the tungstic compounds imposed inhibiting effects on the hydrogenation of glucose over Ru/C catalyst, and the suppressing effect followed the order of H2WO4 >HPW>WO3 >AMT>HSiW. This order is the same as the order of ethylene glycol (EG) yields in the one-pot conversion of glucose to EG, suggesting the important role of competition between glucose hydrogenation and retro-aldol condensation in controlling the selectivity of EG.

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Oxygen permeability and CO2-tolerance of Ce0.8Gd0.2O2-δ-LnBaCo2O5+δ dual-phase membranes
Longfei Luo, Hongwei Cheng, Guangshi Li, Xionggang Lu, Bo Jiang
2015 Vol. 24 (1): 15-22 [Abstract] ( 278 ) [HTML 1KB] [PDF] ( 0 )

A series of oxygen permeable dual-phase composite oxides 60 wt% Ce0.8Gd0.2O2-δ-40 wt% LnBaCo2O5+δ (CGO-LBCO, Ln=La, Pr, Nd, Sm, Gd and Y) were synthesized through a sol-gel route and effects of the Ln3+ cations on their phase structure, oxygen permeability and chemical stability against CO2 were investigated systemically by XRD, SEM, TG-DSC and oxygen permeation experiments. XRD patterns reveal that the larger Ln3+ cations (La3+, Pr3+ and Nd3+) successfully stabilized the double-layered perovskite structure of sintered LBCO, while the smaller ones (Sm3+, Gd3+, and Y3+) resulted in the partial decomposition of LBCO with some impurities formed. CGO-PBCO yields the highest oxygen permeation flux, reaching 2.8×10-7 mol·-1·cm-2 at 925 ℃ with 1 mm thickness under air/He gradient. The TG-DSC profiles in 20 mol% CO2/N2 and oxygen permeability experiments with CO2 as sweep gas show that CGO-YBCO demonstrates the best chemical stability against CO2, possibly due to its minimum basicity. The stable oxygen permeation flux of CGO-YBCO under CO2 atmosphere reveals its potential application in the oxy-fuel combustion route for CO2 capture.

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Numerical simulation of packed-bed reactor for oxidative coupling of methane
Zhao Zhang, Ziqi Guo, Shengfu Ji
2015 Vol. 24 (1): 23-30 [Abstract] ( 282 ) [HTML 1KB] [PDF] ( 0 )

A three-dimensional geometric model of the oxidative coupling of methane (OCM) packed-bed reactor loaded with Na2WO4-Mn/SiO2 particulate catalyst was set up, and an improved Stansch kinetic model was established to calculate the OCM reactions using the computational fluid dynamics method and Fluent software. The simulation conditions were completely the same with the experimental conditions that the volume velocity of the reactant was 80 mL/min under standard state, the ratio of CH4/O2 was 3, the temperature and pressure were 800 ℃ and 1 atm, respectively. The contour of the characteristics parameters in the catalyst bed was analyzed, such as the species mass fractions, temperature, the heat flux on side wall surface, pressure, fluid density and velocity. The results showed that the calculated values matched well with the experimental values on the conversion of CH4 and the selectivity to products (C2H6, C2H4, CO2, CO) in the reactor outlet with an error range of ±2%. The mass fractions of CH4 and O2 decreased from 0.6 and 0.4 in the catalyst bed inlet to 0.436 and 0.142 in the outlet, where the mass fractions of C2H6, C2H4, CO and CO2 were 0.035, 0.061, 0.032 and 0.106, respectively. Due to the existence of laminar boundary layer, the contours of each component bent upwards in the vicinity of the boundary layer. This OCM reaction was volume increase reaction and the total moles of products were greater than those of reactants. The flow field in the catalyst bed maintained constant temperature and pressure. The fluid density decreased gradually from 2.28 kg/m3 in the inlet of the catalyst bed to 2.22 kg/m3 in the outlet of the catalyst bed, while the velocity increased from 0.108 m/s to 0.115 m/s.

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Promising supercapacitor electrodes based immobilization of proteins onto macroporous Ni foam materials
Mohamed Khairy, Sherif A. El-Safty
2015 Vol. 24 (1): 31-38 [Abstract] ( 290 ) [HTML 1KB] [PDF] ( 0 )

Immobilizing biocomponents on solid surfaces is a critical step in the development of new devices for future biological, medical, and electronic applications. Therefore, numerous integrated films were recently developed by immobilizing different proteins or enzymes on electrode surfaces. In this work, hemeproteins were safely immobilized onto macroporous nickel-based electrodes while maintaining their functionality. Such modified electrodes showed interesting pseudo-capacitive behavior. Among hemeproteins, hemoglobin (Hb) film has a higher electrochemical performance and greater charge/discharge cycling stability than myoglobin (Mb) and cytochrome C (CytC). The heme group in an alkaline medium could induce the formation of superoxides on the electrode surface. These capacitive features of hemeprotein-Ni electrode were related to strong binding sites between hemeproteins and porous Ni electrode, the accumulation of superoxide or radicals on the Ni surface, and facile electron transfer and electrolyte diffusion through the three-dimensional macroporous network. Thus, these new protein-based supercapacitors have potential use in free-standing platform technology for the development of implantable energy-storage devices.

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Pt/WO3/C nanocomposite with parallel WO3 nanorods as cathode catalyst for proton exchange membrane fuel cells
Meiling Dou, Ming Hou, Zhilin Li, Feng Wang, Dong Liang, Zhigang Shao, BaolianYi
2015 Vol. 24 (1): 39-44 [Abstract] ( 313 ) [HTML 1KB] [PDF] ( 0 )

Pt/WO3/C nanocomposites with parallel WO3 nanorods were synthesized and applied as the cathode catalyst for proton exchange membrane fuel cells (PEMFCs). Electrochemical results and single cell tests show that an enhanced activity for the oxygen reduction reaction (ORR) is obtained for the Pt/WO3/C catalyst compared with Pt/C. The higher catalytic activity might be ascribed to the improved Pt dispersion with smaller particle sizes. The Pt/WO3/C catalyst also exhibits a good electrochemical stability under potential cycling. Thus, the Pt/WO3/C catalyst can be used as a potential PEMFC cathode catalyst.

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Effects of surface states over core-shell Ni@SiO2 catalysts on catalytic partial oxidation of methane to synthesis gas
Chuanmin Ding, Xiaofeng Gao, Yulin Han, Xishun Ma, Junwen Wang, Shibin Liu, Kan Zhang
2015 Vol. 24 (1): 45-53 [Abstract] ( 283 ) [HTML 1KB] [PDF] ( 0 )

In the present work, core-shell Ni@SiO2 catalysts were investigated in order to evaluate the relevance of catalytic activity and surface states of Ni core as well as Ni nanoparticles size to catalytic partial oxidation of methane (POM). The catalysts were characterized by N2 adsorption, H2-TPR, XRD, TEM and XPS techniques. The catalytic performance of the core-shell catalysts was found to be dependent on the surface states of catalyst, which influenced the formation of products. It was considered that carbon dioxide formed on the oxidized nickel sites (NiO) and carbon monoxide produced on the reduced sites (Ni). The surface states of active metal in the dynamic were influenced both by the size of Ni core and the porosity of silica shell. However, the catalytic activity would be debased when the size of Ni core was under a certain extent, which can be ascribed to the fact the carbon deposition increased with the increasing content of NiO. The effects of surface states of Ni@SiO2 catalyst on the catalytic performance were discussed and the reaction pathway over Ni core encapsulated inside silica shell was proposed.

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Simultaneous syngas production with different H2/CO ratio in a multi-tubular methane steam and dry reformer by utilizing of CLC
Mohsen Abbasi, Mehdi Farniaei, Mohammad Reza Rahimpour, Alireza Shariati
2015 Vol. 24 (1): 54-64 [Abstract] ( 298 ) [HTML 1KB] [PDF] ( 0 )

For syngas production, the combustion of fossil fuels produces large amounts of CO2 as a greenhouse gas annually which intensifies global warming. In this study, chemical looping combustion (CLC) has been utilized for the elimination of CO2 emission to atmosphere during simultaneous syngas production with different H2/CO ratio in steam reforming of methane (SR) and dry reforming of methane (DR) in a CLC-SR-DR configuration. In CLC-SR-DR with 184 reformer tubes (similar to an industrial scale steam reformer in Zagros Petrochemical Company, Assaluyeh, Iran), DR reaction occurs over Rh-based catalysts in 31 tubes. Also, SR reaction is happened over Ni-based catalysts in 153 tubes. CLC via employment of Mn-based oxygen carriers supplies heat for DR and SR reactions and produces CO2 and H2O as raw materials simultaneously. A steady state heterogeneous catalytic reaction model is applied to analyze the performance and applicability of the proposed CLC-SR-DR configuration. Simulation results show that combustion efficiency reached 1 at the outlet of fuel reactor (FR). Therefore, pure CO2 and H2O can be recycled to DR and SR sides, respectively. Also, CH4 conversion reached 0.2803 and 0.7275 at the outlet of SR and DR sides, respectively. Simulation results indicate that, 3223 kmol·h-1 syngas with a H2/CO ratio equal to 9.826 was produced in SR side of CLC-SR-DR. After that, 1844 kmol·h-1 syngas with a H2/CO ratio equal to 0.986 was achieved in DR side of CLC-SR-DR. Results illustrate that by increasing the number of DR tubes to 50 tubes and considering 184 fixed total tubes in CLC-SR-DR, CH4 conversions in SR and DR sides decreased 2.69% and 3.31%, respectively. However, this subject caused total syngas production in SR and DR sides (in all of 184 tubes) enhance to 5427 kmol·h-1. Finally, thermal and molar behaviors of the proposed configuration demonstrate that CLC-SR-DR is applicable for simultaneous syngas production with high and low H2/CO ratios in an environmental friendly process.

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A density functional theory study on the decomposition of aliphatic hydrocarbons and cycloalkanes during coal pyrolysis in hydrogen plasma
Xiaoyuan Huang, Dangguo Cheng, Fengqiu Chen, Xiaoli Zhan
2015 Vol. 24 (1): 65-71 [Abstract] ( 288 ) [HTML 1KB] [PDF] ( 0 )

To get deep understanding of the reaction mechanism of coal pyrolysis in hydrogen plasma, the decomposition reaction pathways of aliphatic hydrocarbons and cycloalkanes, which are two main components in volatiles from coal, were investigated. Methane and cyclohexane were chosen as the model compounds. Density functional theory was employed, and many reaction pathways were involved. Calculations were carried out in Gaussian 09 at the B3LYP/6-31G(d,p) level of the theory. The results indicate that the main pyrolysis products of methane and cyclohexane in hydrogen plasma are both hydrogen and acetylene, and the participation of active hydrogen atoms makes dehydrogenation reactions more favorable. H2 mainly comes from dehydrogenation process, while many reaction pathways are responsible for acetylene formation. During coal pyrolysis in hydrogen plasma, three main components in volatiles like aliphatic hydrocarbons, cycloalkanes and aromatic hydrocarbons lead to the formation of hydrogen and acetylene, but their contributions to products distribution are different.

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Microwave assisted liquefaction of wheat straw alkali lignin for the production of monophenolic compounds
Xinping Ouyang, Guodian Zhu, Xiangzhen Huang, Xueqing Qiu
2015 Vol. 24 (1): 72-76 [Abstract] ( 273 ) [HTML 1KB] [PDF] ( 0 )

The microwave assisted liquefaction process of wheat straw alkali lignin was investigated to obtain monophenolic compounds as the precursor of bio-fuel. It is found that the total yield of monophenolic compounds is significantly improved under microwave irradiation, reaching 15.77% under a relatively mild liquefaction condition of 10 wt% H2SO4 as the catalyst, 10 wt% phenol as the hydrogen-donor reagent at 120 ℃ for 40 min. Compared with conventional thermal liquefaction process, microwave irradiation promotes the cleavage of C-C bonds, which gives an extra 29% of Caryl-Cα bond cleavage, and increases the yield of monophenolic compounds from 0.92% to 13.61% under the same conditions. The excessive temperature and prolonged time under microwave irradiation will promote the recondensation of degraded lignin fragments, so the key to obtain high yield of monophenolic compounds is to avoid the recondensation reaction. The selected solid catalyst promotes the dissociation of methoxy groups, and the addition of phenol into liquefaction can only slightly improve the yield of monophencolic compounds.

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Deoxygenation of methyl laurate to hydrocarbons on silica-supported Ni-Mo phosphides: Effect of calcination temperatures of precursor
Zhengyi Pan, Rijie Wang, Mingfeng Li, Yang Chu, Jixiang Chen
2015 Vol. 24 (1): 77-86 [Abstract] ( 275 ) [HTML 1KB] [PDF] ( 0 )

SiO2-supported Ni-Mo bimetallic phosphides were prepared by temperature-programmed reduction (TPR) method from the phosphate precursors calcined at different temperatures. Their properties were characterized by means of ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), H2 temperature-programmed reduction (H2-TPR), X-ray diffraction (XRD), transmission electron microscopy (TEM), CO chemisorption, H2 and NH3 temperature-programmed desorptions (H2-TPD and NH3-TPD). Their catalytic performances for the deoxygenation of methyl laurate were tested in a fixed-bed reactor. When the precursors were calcined at 400 and 500 ℃, respectively, NiMoP2 phase could be formed apart from Ni2P and MoP phases in the prepared C400 and C500 catalysts. However, when the precursors were calcined at 600, 700 and 800 ℃, respectively, only Ni2P and MoP phases could be detected in the prepared C600, C700 and C800 catalysts. Also, in C400, C500 and C600 catalysts, Mo atoms were found to be entered in the lattice of Ni2P phase, but the entering extent became less with the increase of calcination temperature. As the calcination temperature of the precursor increased, the interaction between Ni and Mo in the prepared catalysts decreased, and the phosphide crystallite size tended to increase, subsequently leading to the decrease in the surface metal site density and the acid amount. C600 catalyst showed the highest activity among the tested ones for the deoxygenation of methyl laurate. As the calcination temperature of the precursor increased, the selectivity to C12 hydrocarbons decreased while the selectivity to C11 hydrocarbons tended to increase. This can be mainly attributed to the decreased Ni-Mo interaction and the increased phosphide particle size. In sum, the structure and performance of Ni-Mo bimetallic phosphide catalyst can be tuned by the calcination temperature of precursor.

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Alkali salts of heteropoly tungstates: Efficient catalysts for the synthesis of biodiesel from edible and non-edible oils
Rekha Sree, Sunny Kuriakose
2015 Vol. 24 (1): 87-92 [Abstract] ( 291 ) [HTML 1KB] [PDF] ( 0 )

Alkali salts of tungsten based heteropoly acids with different central atom such as P, Si and Co were prepared and evaluated for transesterification of both edible and non-edible oils to their corresponding fatty acid methyl esters. The catalyst of sodium salt of tungstic acid with Co as central atom (Na5CoW12O40) showed optimum activity towards transesterification compared with other heteropoly tungstates. The catalysts activities were correlated with the observed physico-chemical characteristics derived from FT-infrared (FT-IR), X-ray diffraction (XRD), temperature-programmed desorption of ammonia (NH3-TPD) and carbon dioxide (CO2-TPD). The Na5CoW12O40 catalyst exhibiting high activity even at 65 ℃ is due to the presence of strong acidic as well as basic sites. The disclosed catalyst is tolerable towards water and free fatty acids present in the oils. The influence of catalyst loading, reaction time and reaction temperature is studied to optimize the reaction parameters.

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A statistical method for assessment of the existing correlations of hydrate forming conditions
Javad Sayyad Amin, Somayye Nikkhah, Mehdi Veiskarami
2015 Vol. 24 (1): 93-100 [Abstract] ( 308 ) [HTML 1KB] [PDF] ( 0 )

Hydrate formation in the oil and gas industries has been a serious problem for a long time. It may cause many difficulties for instance in gas pipelines blockages. In order to determine the hydrate forming condition, gas gravity method has been used. Several correlations have been proposed based on gas gravity method. Checking the accuracy of the applied correlations is important. In this paper, the leverage approach is used for this purpose. Leverage approach is a statistical method for detection outliers which identifies the applicability domain (AD) of hydrate data predicting correlations and the quality of the existing data. Moreover, the Williams plot is sketched, which is a graphical depiction for determination of the doubtful points. The obtained results showed the existing correlations are all statistically correct and valid to predict hydrate formation temperature, just one data point is out of the applicability domains, and none of the experimental data can be chosen as outliers.

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Investigation of the characteristics and deactivation of catalytic active center of Cr-Al2O3 catalysts for isobutane dehydrogenation
Deren Fang, Jinbo Zhao, Wanjun Li, Xu Fang, Xin Yang, Wanzhong Ren, Huimin Zhang
2015 Vol. 24 (1): 101-107 [Abstract] ( 288 ) [HTML 1KB] [PDF] ( 0 )

Deactivation mechanism of Cr-Al2O3 catalyst and the interaction of Cr-Al in the dehydrogenation of isobutane, as well as the nature of the catalytic active center, were studied using XRD, SEM, XPS, H2-TPR, isobutane-TPR and TPO techniques. The results revealed that the deactivation of Cr-Al2O3 catalyst was mainly caused by carbon deposition on its surface. The Cr3+ ion could not be reduced by hydrogen but could be reduced to Cr2+ by hydrocarbons and monoxide carbon. The active center for isobutane dehydrogenation could be Cr2+/Cr3+ produced from Cr6+ by the on line reduction of hydrocarbon and carbon monoxide. The binding energy of Al3+ was strongly affected by the state of chromium cations in the catalysts.

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Coking kinetics and influence of reaction-regeneration on acidity, activity and deactivation of Zn/HZSM-5 catalyst during methanol aromatization
Guiquan Zhang, Xin Zhang, Ting Bai, Tengfei Chen, Wentao Fan
2015 Vol. 24 (1): 108-118 [Abstract] ( 289 ) [HTML 1KB] [PDF] ( 0 )

The coking kinetics and reaction-regeneration on Zn/HZSM-5 (Zn/HZ) catalyst in the conversion of methanol to aromatics were investigated. The highest initial benzene, toluene and xylene (BTX) yield of ca. 67.7% was obtained on fresh Zn/HZ catalyst, which showed the worst catalytic stability. The cycle of reaction-regeneration significantly modified the texture and acidity of Zn/HZ catalyst, which in turn affected its catalytic performance and coking behavior in methanol conversion to BTX. The residual carbon located on the surface of Zn/HZ catalyst led to the decrease of acid sites and the change on the acid sites distribution, which played an important roles on its activity and deactivation. It was found that the high B/L ratio and the low total acid sites concentration of the Zn/HZ catalyst favored to the high BTX yield and good catalytic stability in methanol conversion.

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Theoretic heat sink simulation and experimental investigation of the pyrolysis of substituted cyclohexanes
Daoan Sun, Yongmei Du, Chunying Li, Jianwei Zhang, Juyou Lu, Zhixuan Wang, Jiaoyi Li, Jian Lü
2015 Vol. 24 (1): 119-125 [Abstract] ( 268 ) [HTML 1KB] [PDF] ( 0 )

Reaxgen program for the pyrolysis mechanism of cycloalkanes was adopted to simulate the heat sink of substituted cyclohexanes. Thermal cracking of cyclohexanes was performed to examine the cracking performance, wherein the substituent effects were detailedly discussed under supercritical condition. It was found that Reaxgen program played a good part in the screening and optimization of cyclohexanes. A good agreement with the experimental data for the mono-substituted and bi-substituted cyclohexanes was demonstrated, however, some deviation for the tri-substituted cyclohexanes were observed. The experiment results indicated that the gaseous product yield increased sharply for mono-substituted cyclohexanes with short substituents containing no more than two carbons. Nevertheless, continuous increase in the alkyl chain depressed the gaseous product yield smoothly. The cyclic substituent dramatically inhibited the pyrolysis of cyclohexanes. All the substituents but cyclohexyl had no obvious effect on the yield of hydrogen and olefins (≤C4). For bi-substituted cyclohexanes, the more close the distance between the two substituents, the higher the gaseous product yield was obtained. However, opposite result on the selectivity to hydrogen and olefins (≤C4) was generally obtained except 1,3-dimethylcyclohexane. The position of tri-substituents acted little significance on the gaseous product yield, as well as the selectivity to hydrogen and olefins (≤C4).

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(Started in 1992)
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ISSN 2095-4956
CN 21-1585/O4

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Xinhe Bao
Alexis T. Bell


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Journal of Energy Chemistry

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