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2013, Vol. 22, No. 5　Online: 2013-09-20


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Zuo and coworkers in their article on pages 685–689 reported graphene nanopowder is a good candidate of advanced electrode materials, which can be used to fabricate modified electrodes for electro-catalytic oxidation of dopamine and uric acid in the presence of ascorbic acid.

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COMMUNICATION

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Effect of O2/CH4 ratio on the optimal specific-energy-input (SEI) for oxidative reforming of biogas in a plasma-shade reactor Jinglin Liu, Xiaobing Zhu, Xiaosong Li, Kai Li, Chuan Shi, Aimin Zhu 2013, 22(5): 681-684.  摘要 ( 8985 )   PDF(601KB) ( 960 )   In a novel plasma-shade reactor for oxidative reforming of biogas (CH4/CO2=3/2), the effects of specific-energy-input (SEI) on CH4 and CO2 conversions and energy cost of syngas were investigated at O2/CH4 ratios ranged from 0.42 to 0.67. At each of O2/CH4 ratios, V-shape profiles of energy cost of syngas increasing with SEI were observed, reaching the lowest value at the optimal SEI (Opt-SEI). With the increase of O2/CH4 ratio, the Opt-SEI decreased significantly. Moreover, at the Opt-SEI, O2 and CH4 conversions and dry-basis concentration of syngas increased and energy cost of syngas decreased greatly with the increase of O2/CH4 ratio.

ARTICLES

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The graphene nanopowder for electro-catalytic oxidation of dopamine and uric acid in the presence of ascorbic acid Yuan Bu, Wenle Dai, Nan Li, Xinran Zhao, Xia Zuo 2013, 22(5): 685-689.  摘要 ( 6590 )   PDF(452KB) ( 676 )   The graphene nanopowder for electro-catalytic oxidation of dopamine and uric acid in the presence of ascorbic acid has been investigated by cyclic voltammetry, linear polarization and chronoamperometry. The graphene nanopowder modified electrode was prepared using the drop coating method, which displayed excellent electrocatalytic activity towards the oxidation of dopamine and uric acid compared with the bare glassy carbon electrode in phosphate buffer solution at pH=7.0. Linear responses for dopamine and uric acid were obtained in the ranges of 3.3 μmol/L to 249.1 μmol/L and 6.7 μmol/L to 386.3 μmol/L with detection limits of 1.5 μmol/L and 2.7 μmol/L (S/N=3), respectively. The response time was less than 2 s in case of dopamine and 3 s in case of uric acid, respectively. The results demonstrated that the graphene nanopowder had potential for detecting dopamine and uric acid.

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Activity and basic properties of KOH/mordenite for transesterification of palm oil Pisitpong Intarapong, Sotsanan Iangthanarat, Pitchaya Phanthong, Apanee Luengnaruemitchai, Samai Jai-In 2013, 22(5): 690-700.  摘要 ( 5619 )   PDF(1521KB) ( 2007 )   The catalytic performance of KOH/mordenite has been studied for transesterification of palm oil using a batch reactor and a packed-bed reactor at 60℃ and atmospheric pressure. The KOH/mordenite processed transesterification in the batch reactor gave the highest methyl ester yield of 96.7% under optimum conditions, while a methyl ester content over 94.5% was obtained in the packed-bed reactor. This comparison indicates that transesterification in a batch-type reactor gives a higher methyl ester yield than that of a continuous-flow reactor. Dealumination was found in the calcined catalysts and had a significant effect on the physical structure and chemical composition of the catalysts. Leaching of the potassium species was negligible, whereas depositing and washing of the reacted mixture with acetone on the catalyst surface were observed by FTIR.

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Soot formation and oxidation during bio-oil gasification: experiments and modeling Younes Chhiti, Marine Peyrot, Sylvain Salvador 2013, 22(5): 701-709.  摘要 ( 6556 )   PDF(789KB) ( 1277 )   A model is proposed to describe soot formation and oxidation during bio-oil gasification. It is based on the description of bio-oil heating, devolatilization, reforming of gases and conversion of both char and soot solids. Detailed chemistry (159 species and 773 reactions) is used in the gas phase. Soot production is described by a single reaction based on C2H2 species concentration and three heterogeneous soot oxidation reactions. To support the validation of the model, three sets of experiments were carried out in a lab-scale Entrained Flow Reactor (EFR) equipped with soot quantification device. The temperature was varied from 1000 to 1400℃ and three gaseous atmospheres were considered: default of steam, large excess of steam (H2O/C=8), and the presence of oxygen in the O/C range of 0.075-0.5. The model is shown to accurately describe the evolution of the concentration of the main gas species and to satisfactorily describe the soot concentration under the three atmospheres using a single set of identified kinetic parameters. Thanks to this model the contribution of different mechanisms involved in soot formation and oxidation in various situations can be assessed.

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Selective hydrogenation of benzene to cyclohexene over Ce-promoted Ru catalysts Haijie Sun, Yajie Pan, Shuaihui Li, Yuanxin Zhang, Yingying Dong, Shouchang Liu, Zhongyi Liu 2013, 22(5): 710-716.  摘要 ( 5991 )   PDF(44KB) ( 55 )   Ru-Ce catalysts were prepared by a co-precipitation method. The effects of Ce precursors with different valences and Ce contents on the catalytic performance of Ru-Ce catalysts were investigated in the presence of ZnSO4. The Ce species in the catalysts prepared with different valences of the Ce precursors all exist as CeO2 on the Ru surface. The promoter CeO2 alone could not improve the selectivity to cyclohexene of Ru catalysts. However, almost all the CeO2 in the catalysts could react with the reaction modifier ZnSO4 to form (Zn(OH)2)3(ZnSO4)(H2O)3 salt. The amount of the chemisorbed salt increased with the CeO2 loading, resulting in the decrease of the activity and the increase of the selectivity to cyclohexene of Ru catalyst. The Ru-Ce catalyst with the optimum Ce/Ru molar ratio of 0.19 gave a maximum cyclohexene yield of 57.4%. Moreover, this catalyst had good stability and excellent reusability.

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SMFs-supported Pd nanocatalysts in selective acetylene hydrogenation: Pore structure-dependent deactivation mechanism Elaheh Esmaeili, Ali Morad Rashidi, Yadollah Mortazavi, Abbas Ali Khodadadi, Mehdi Rashidzadeh 2013, 22(5): 717-725.  摘要 ( 6099 )   PDF(42KB) ( 52 )   In the present study, CNFs, ZnO and Al2O3 were deposited on the SMFs panels to investigate the deactivation mechanism of Pd-based catalysts in selective acetylene hydrogenation reaction. The examined supports were characterized by SEM, NH3-TPD and N2 adsorption-desorption isotherms to indicate their intrinsic characteristics. Furthermore, in order to understand the mechanism of deactivation, the resulted green oil was characterized using FTIR and SIM DIS. FTIR results confirmed the presence of more unsaturated constituents and then, more branched hydrocarbons formed upon the reaction over alumina-supported catalyst in comparison with the ones supported on CNFs and ZnO, which in turn, could block the pores mouths. Besides the limited hydrogen transfer, N2 adsorption-desorption isotherms results supported that the lowest pore diameters of Al2O3/SMFs close to the surface led to fast deactivation, compared with the other catalysts, especially at higher temperatures.

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Kinetic study of propane dehydrogenation and catalyst deactivation over Pt-Sn/Al2O3 catalyst Farnaz Tahriri Zangeneh, Abbas Taeb, Khodayar Gholivand, Saeed Sahebdelfar 2013, 22(5): 726-732.  摘要 ( 7137 )   PDF(237KB) ( 8314 )   The kinetics of propane dehydrogenation and catalyst deactivation over Pt-Sn/Al2O3 catalyst were studied. Performance test runs were carried out in a fixed-bed integral reactor. Using a power-law rate expression for the surface reaction kinetics and independent law for deactivation kinetics, the experimental data were analyzed both by integral and a novel differential method of analysis and the results were compared. To avoid fluctuation of time-derivatives of conversion required for differential analysis, the conversion-time data were first fitted with appropriate functions. While the time-zero and rate constant of reaction were largely insensitive to the function employed, the rate constant of deactivation was much more sensitive to the function form. The advantage of the proposed differential method, however, is that the integration of the rate expression is not necessary which otherwise could be complicated or impossible. It was also found that the reaction is not limited by external and internal mass transfer limitations, implying that the employed kinetics could be considered as intrinsic ones.

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Ni-Co/Mg-Al catalyst derived from hydrotalcite-like compound prepared by plasma for dry reforming of methane Huali Long, Yan Xu, Xiaoqing Zhang, Shijing Hu, Shuyong Shang, Yongxiang Yin, Xiaoyan Dai 2013, 22(5): 733-739.  摘要 ( 6373 )   PDF(890KB) ( 1540 )   Ni-Co bimetallic catalysts with different Ni/Co content were derived from cold plasma jet decomposition and reduction of hydrotalcite-like compounds containing Ni, Co, Mg and Al, and their catalytic performance was investigated with dry reforming of methane. Experimental results showed that the hydrotalcite-like precursors could be completely decomposed and partly reduced by cold plasma jet, and the Ni-contained catalysts exhibited much higher activity than the catalyst without Ni. Especially, the catalyst with Ni/Co ratio of 8/2 achieved not only the highest conversions of 80.3% and 69.3% for CH4 and CO2, respectively, but also the best stability in 100 h testing. The catalysts were characterized by XRD, XPS, TEM and N2 adsorption techniques, and the results showed that the better performance of the 8Ni2Co bimetallic catalyst was attributed to its higher metal dispersion, smaller metal particle size, as well as the interaction effect between Ni and Co, which were brought by the special catalyst preparation method.

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Comparative study of fluidized-bed and fixed-bed reactor for syngas methanation over Ni-W/TiO2-SiO2 catalyst Bo Liu, Shengfu Ji 2013, 22(5): 740-746.  摘要 ( 8609 )   PDF(686KB) ( 4229 )   In this work, syngas methanation over Ni-W/TiO2-SiO2 catalyst was studied in a fluidized-bed reactor (FBR) and its performance was compared with a fixed-bed reactor (FIXBR). The effects of main operating variables including feedstock gases space velocity, coke content, bed temperature and sulfur-tolerant stability of 100 h life were investigated. The structure of the catalysts was characterized by XRD, N2 adsorption-desorption and TEM. It is found that under same space velocity from 5000 h-1 to 25000 h-1 FBR gave a higher CH4 yield, lower coke content, and lower bed temperature than those obtained in FIXBR. Ni-W/TiO2-SiO2 catalyst possessed excellent sulfur-tolerant stability on the feedstock gases less than 500 ppm H2S in FBR. The carbon deposits formed on the spent catalyst were in the form of carbon fibers in FBR, while in the form of dense accumulation distribution appearance in FIXBR.

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Performance enhancement of bimetallic Co-Ru/CNTs nano catalysts using microemulsion technique Ahmad Tavasoli, Somayeh Taghavi 2013, 22(5): 747-754.  摘要 ( 9440 )   PDF(774KB) ( 1688 )   Bimetallic cobalt-ruthenium nano catalysts supported on carbon nanotubes (CNTs) are prepared using microemultion technique with water-to-surfactant ratios of 0.5-1.5. The nano catalysts were extensively characterized by different methods and their activity and selectivity in Fischer-Tropsch synthesis (FTS) have been assessed in a fixed-bed microreactor. The physicochemical properties and performance of the nanocatalysts were compared with the catalyst prepared by impregnation method. Very narrow particle size distribution has been produced by the microemulsion technique at relatively high loadings of active metals (15 wt% Co and 1 wt% Ru). According to TEM images, small Co particles (2-7 nm) were mostly confined inside the CNTs. Comparing with the catalyst prepared by impregnation, the use of microemulsion technique with water to surfactant ratio of 0.5 decreased the average cobalt oxide particle size to 4.8 nm, the dispersion was almost doubled and the reduction increased by 28%. Activity and selectivity were found to be dependent on the catalyst preparation method and water-to-surfactant ratio (as well as cobalt particle sizes). CO conversion increased from 59.1% to 75.1% and the FTS rate increased from 0.291 to 0.372 gHC/(gcat·h). C5+ liquid hydrocarbons selectivity decreased from 92.4% to 87.6%.

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Co-feeding with DME: An effective way to enhance gasoline production via low temperature aromatization of LPG Xiangxue Zhu, Yuzhong Wang, Xiujie Li, Hongbing Li, Peng Zeng, Jie An, Fucun Chen, Sujuan Xie, Hongping Lan, Dawei Wang, Shenglin Liu, Longya Xu 2013, 22(5): 755-760.  摘要 ( 6187 )   PDF(306KB) ( 713 )   The aromatization of light alkenes in liquefied petroleum gas (LPG) with and without dimethyl ether (DME) addition in the feed was investigated on a modified ZSM-5 catalyst. The results showed that under the given reaction conditions the selectivity of alkenes to high-octane gasoline blending components was markedly enhanced and the formation of propane and butanes was greatly suppressed with the addition of DME. It was also found that the distribution of C5+ components was changed a lot with DME addition into the LPG feed. The formation of branched hydrocarbons (mainly C6-C8 i-paraffin) and multi-methyl substituted aromatics, which are high octane number gasoline blending components, was promoted significantly, while the content of n-paraffins and olefins in C5+ components was decreased obviously, indicating that in addition to the oligomerization, cracking, hydrogen-transfer and dehydrogenation-cyclization of alkenes, the methylation of the formed aromatics and olefins intermediates also plays an important role in determining the product distribution due to the high reactivity of surface methoxy groups formed by DME. And this process, in combination with the syngas-to-methanol/DME technology, provides an alternative way to the production of high-octane gasoline from coal, natural gas or renewable raw materials.

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Hierarchical ZSM-11 with intergrowth structures: Synthesis, characterization and catalytic properties Qingjun Yu, Chaoyue Cui, Qiang Zhang, Jing Chen, Yang Li, Jinpeng Sun, Chunyi Li, Qiukai Cui, Chaohe Yang, Honghong Shan 2013, 22(5): 761-768.  摘要 ( 6480 )   PDF(2510KB) ( 2893 )   Hierarchical ZSM-11 microspheres with intercrystalline mesoporous properties and rod-like crystals intergrowth morphology have been synthesized using a spot of tetrabutylammonium as a single template. XRD, FTIR, SEM, TEM and N2 adsorption analysis revealed that each individual particle was composed of nanosized rod crystals inserting each other and the intercrystalline voids existing among rods gave a significant mesopore size distribution. Steam treatment result demonstrated the excellent hydrothermal stability of samples. Various crystallization modes including constant temperature crystallization (one-stage crystallization) and two-stage temperature-varying crystallization with different 1st stage durations were investigated. The results suggested that the crystallization modes were mainly responsible for the adjustable particle size and textural properties of samples while the small amount of tetrabutylammonium bromide was mainly used to direct the formation of both ZSM-11 framework and its intergrowth morphology. Furthermore, the performance of optimal ZSM-11 as an active component for the catalytic pyrolysis of heavy oil was also investigated. Compared with the commercial pyrolysis catalyst, the hierarchical ZSM-11 catalyst exhibited a high selectivity to desired products (LPG+gasoline+diesel), as well as a much lower dry gas and coke yield, plus a high selectivity and yield of light olefins (C3=-C4=) and very poor selectivity to benzene. Therefore, fully open micropore-mesopore connectivity would make such hierarchically porous ZSM-11 zeolites very attractive for applications in clean petrochemical catalysis field.

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Catalytic performance of hierarchical H-ZSM-5/MCM-41 for methanol dehydration to dimethyl ether Yu Sang, Hongxiao Liu, Shichao He, Hansheng Li, Qingze Jiao, Qin Wu, Kening Sun 2013, 22(5): 769-777.  摘要 ( 7790 )   PDF(2270KB) ( 2287 )   Micro-mesoporous composite molecular sieves H-ZSM-5/MCM-41 were prepared by the hydrothermal technique with alkali-treated H-ZSM-5 zeolite as the source and characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, X-ray diffraction, N2 adsorption-desorption measurement and NH3 temperature-programmed desorption. The catalytic performances for the methanol dehydration to dimethyl ether over H-ZSM-5/MCM-41 were evaluated. Among these catalysts, H-ZSM-5/MCM-41 prepared with NaOH dosage (nNa/nSi) varying from 0.4 to 0.47 presented excellent catalytic activity with more than 80% methanol conversion and 100% dimethyl ether selectivity in a wide temperature range of 170-300℃, and H-ZSM-5/MCM-41 prepared with nNa/nSi=0.47 showed constant methanol conversion of about 88.7%, 100% dimethyl ether selectivity and excellent lifetime at 220℃. The excellent catalytic performances were due to the highly active and uniform acidic sites and the hierarchical porosity in the micro-mesoporous composite molecular sieves. The catalytic mechanism of H-ZSM-5/MCM-41 for the methanol dehydration to dimethyl ether process was also discussed.

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Effect of Sr loading on oxydehydrogenation of propane to propylene over Al2O3-supported V-Mo catalysts Meilana Dharma Putra, Saeed M. Al-Zahrani, Ahmed E. Abasaeed 2013, 22(5): 778-782.  摘要 ( 6640 )   PDF(628KB) ( 929 )   Incorporation of strontium into V-Mo alumina-supported catalyst enhanced its performance (increased conversion and selectivity, decreased reducibility and improved stability) in propane oxydehydrogenation to propylene. 12.5% Sr loading was shown to be the optimum content to the V-Mo catalyst. The results were supported by various characterization techniques, namely, BET, XRD, SEM, FTIR and TPD.

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Effect of impregnation methods on sorbents made from lignite for desulfurization at middle temperature Yurong Dong, Xiurong Ren, Meijun Wang, Qiang He, Liping Chang, Weiren Bao 2013, 22(5): 783-789.  摘要 ( 5271 )   PDF(339KB) ( 1092 )   With lignite after vacuum drying as the raw material, a series of Zn-based sorbents were prepared by static impregnation, ultrasonic-assisted impregnation, bubbling-assisted impregnation and high-pressure impregnation. The physical properties and the desulfurization performances of Zn-based sorbents were studied systematically by XRD, BET, AAS characterization techniques and the fixed-bed desulfurization evaluation apparatus. The sorbents obtained by high-pressure impregnation method have a larger specific surface area, pore volume and pore diameter comparing with other methods, which is conducive to the sulfidation reaction of hydrogen sulfide gas in the sorbent. The effects of pressure during the high-pressure impregnation and concentration of Zn(NO3)2 precursor solution on the sorbents properties and desulfurization behavior were investigated. The higher the impregnation pressure and the concentration of impregnation solution are, the greater the amount of the active components are uploaded. However, overhigh impregnation pressure can cause collapse and blocking of the carrier pore. The optimal operating condition of high-pressure impregnation method for preparing the sorbents was the impregnation pressure of 20 atm and the solution concentration of 41%. Under that condition, the sorbent had the best desulfurization ability with a sulfur capacity of 13.94 gS/100 gsorbent and a breakthrough time of 54 h. Its desulfurization precision and efficiency of removing H2S before sorbent breakthrough from the middle temperature gases of 400℃ can reach <5 ppm and >99%, respectively. Sorbents could be regenerated under the condition of 1 vol% O2, 20 vol% H2O, 0.5 vol%NH3, and N2 balance gas. The regenerated sorbent could be used for repeated absorption of H2S with a slight decrease in desulfurization effect.

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Enhanced cyclability of sulfur cathodes in lithium-sulfur batteries with Na-alginate as a binder Weizhai Bao, Zhian Zhang, Yongqing Gan, Xiwen Wang, Jie Lia 2013, 22(5): 790-794.  摘要 ( 5846 )   PDF(996KB) ( 2813 )   Na-alginate as a binder in an aqueous solvent has been applied in the preparation of sulfur cathodes for lithium-sulfur batteries. Their electrochemical performances have been investigated by a charge-discharge cycle test and electrochemical impedance spectroscopy (EIS). The EIS tests indicated that the alginate sulfur cathode had lower resistance and better kinetic characteristics than those of the poly(vinylidene fluoride) (PVDF) sulfur cathode using PVDF as a binder in a N-methy-2-pyrrolidone (NMP) solvent. The charge-discharge tests showed that the discharge capacity and the capacity retention rate of Na-alginate sulfur cathode were 508 mAh·g-1 and 65.4% at the 50th cycle with a current density of 335 mA·g-1. Compared with PVDF sulfur cathode, the alginate sulfur cathode showed a remarkably better cycle performance. These results show that the alginate binder has promising potential for lithium-sulfur battery applications.

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Effect of mass transfer limitations on catalyst performance during reduction and carburization of iron based Fischer-Tropsch synthesis catalysts Akbar Zamaniyan, Yadollah Mortazavi, Abbas Ali Khodadadi, Ali Nakhaei Pour 2013, 22(5): 795-803.  摘要 ( 5511 )   PDF(1437KB) ( 1729 )   Existence of intraparticle mass transfer limitations under typical Fischer-Tropsch synthesis has been reported previously, but there is no suitable study on the existence of intraparticle diffusion limitations under pretreatment steps (reduction and activation) and their effect on catalytic performance for iron based catalysts. In this study, Fe-Cu-La-SiO2 catalysts were prepared by co-precipitation method. To investigate the intraparticle mass transfer limitation under reduction, activation and reaction steps, and its effect on catalytic performance, catalyst pellets with different sizes of 6, 3, 1 and 0.5 mm have been prepared. All catalysts were calcined, pretreated and tested under similar conditions. The catalysts were activated in hydrogen (5% H2 in N2) at 450℃ for 3 h and exposed to syngas (H2/CO=1) at 270℃ and atmospheric pressure for 40 h. Afterwards, FTS reaction tests were performed for approximately 120 h to reach steady state conditions at 290℃, 17 bar and a feed flow (syngas H2/CO=1) rate of 3 L/h (STP). Using small pellets resulted in higher CO conversion, FT reaction rate and C5+ productivity as compared with larger pellets. The small pellets reached steady state conditions just 20 h after starting the reaction. Whereas for larger pellets, CO conversion, FT reaction rate and C5+ productivity increased gradually, and reached steady state and maximum values after 120 h of operation. The results illustrate that mass transfer limitations exist not only for FTS reaction but also for the reduction and carburization steps which lead to various phase formation through catalyst activation. Also the results indicate that some effects of mass transfer limitations in activation step, can be compensated in the reaction step. The results can be used for better design of iron based catalyst to improve the process economy.

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Creation of surface defects on carbon nanofibers by steam treatment Zhengfeng Shao, Min Pang, Wei Xia, Martin Muhler, Changhai Liang 2013, 22(5): 804-810.  摘要 ( 6618 )   A direct strategy for the creation of defects on carbon nanofibers (CNFs) has been developed by steam treatment. Nitrogen physisorption, XRD, Raman spectra, SEM and TEM analyses proved the existence of the new defects on CNFs. BET surface area of CNFs after steam treatment was enhanced from 20 to 378 m2/g. Pd catalysts supported on CNFs were also prepared by colloidal deposition method. The different activity of Pd/CNFs catalysts in the partial hydrogenation of phenylacetylene further demonstrated the diverse surfaces of CNFs could be formed by steam treatment.

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Synthesis gas production on glass cloth catalysts modified by Ni and Co oxides G. B. Aldashukurova, A. V. Mironenko, Z. A. Mansurov, N. V. Shikina, S. A. Yashnik, V. V. Kuznetsov, Z. R. Ismagilov 2013, 22(5): 811-818.  摘要 ( 5803 )   PDF(1126KB) ( 1213 )   The catalytic activity of nanostructured low percent (1%) Co-Ni catalysts on the basis of glass fiber (GF) prepared by a "solution combustion" (SC) method was studied. The catalytic activity of the prepared samples was studied in the reaction of dry reforming of methane (DRM) with CO2. The obtained samples were characterized by a number of physico-chemical methods, including XRD, SEM, TEM, TGA and AFM. The active component was shown to be dispersed in the near-surface layer of the support as nanoparticles of 10-20 nm in size. The active component showed a Co3O4 or (Co, Ni)Co2O4 spinel structure, depending on the catalyst composition. The spinel structure of the active component interacted strongly with the carrier, providing resistance to carbonization, high catalytic activity toward DRM, and high activity and stability in oxidation reactions.