过刊目录

2012, Vol. 21, No. 5　Online: 2012-09-27

上一期    下一期

全全选选:

导出引用 EndNote Ris BibTeX

隐藏/显示图片

article

Select

Preparation and characterization of vanadium(IV) oxide supported on SBA-15 and its catalytic performance in benzene hydroxylation to phenol using molecular oxygen Xing Chen, Wenguang Zhao, Feng Wang*, Jie Xu* 2012, 21(5): 481-487.  DOI: 10.1016/S1003-9953(11)60394-0 摘要 ( 9508 )   Preparation of dispersed transition metal oxides catalyst with low oxidation state still remains a challenging task in heterogeneous catalysis. In this study, vanadium oxides supported on zeolite SBA-15 have been prepared under hydrothermal condition using V2O5 and oxalic acid as sources of vanadium and reductant, respectively. The structures of samples, especially the oxidation state of vanadium, and the surface distribution of vanadium oxide species, have been thoroughly characterized using various techniques, including N2-physisorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-visible spectra (UV-Vis) and UV-visible-near infrared spectra (UV-Vis-NIR). It is found that the majority of supported vanadium was in the form of vanadium(IV) oxide species with the low valence of vanadium. By adjusting hydrothermal treatment time, the surface distribution of vanadium(IV) oxide species can be tuned from vanadium(IV) oxide cluster to crystallites. These materials have been tested in the hydroxylation of benzene to phenol in liquid-phase with molecular oxygen in the absence of reductant. The catalyst exhibits high selectivity for phenol (61%) at benzene conversion of 4.6%, which is a relatively good result in comparison with other studies employing molecular oxygen as the oxidant.

Select

Hydrogen generation from methanolysis of sodium borohydride over Co/Al2O3 catalyst Dongyan Xu*, Lin Zhao, Ping Dai, Shengfu Ji 2012, 21(5): 488-494.  DOI: 10.1016/S1003-9953(11)60395-2 摘要 ( 12429 )   Co/Al2O3 catalyst is prepared with an impregnation-chemical reduction method and used to catalyze the methanolysis of sodium borohydride (NaBH4) for hydrogen generation. At solution temperature of 0 ℃, the methanolysis reaction can be effectively accelerated using Co/Al2O3 catalyst and provide a desirable hydrogen generation rate, which makes it suitable for applications under the circumstance of low environmental temperature. The byproduct of methanolysis reaction is analyzed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The characterization results indicate that methanol can be easily recovered after methanolysis reaction by hydrolysis of the methanolysis byproduct, NaB(OCH3)4. The catalytic activity of Co/Al2O3 towards NaBH4 methanolysis can be further improved by appropriate calcination treatment. The catalytic methanolysis kinetics and catalyst reusability are also studied over the Co/Al2O3 catalyst calcined at the optimized temperature.

Select

Stability improvement of the Nieuwland catalyst in the dimerization of acetylene to monovinylacetylene Jianguo Liu, Yizan Zuo, Minghan Han*, Zhanwen Wang, Dezheng Wang 2012, 21(5): 495-500.  DOI: 10.1016/S1003-9953(11)60396-4 摘要 ( 8176 )   In the process of dimerization of acetylene to produce monovinylacetylene (MVA), the loss of active component CuCl in the Nieuwland catalyst due to the formation of a dark red precipitate was investigated. The formula of the precipitate was CuCl·2C2H2·1/5NH3, and it was presumed to be formed by the combination of NH3, C2H2 and [Cu]-acetylene π-complex, which was an intermediate in the dimerization reaction. The addition of hydrochloric acid into the catalyst can reduce the formation of precipitate, whereas excessive H+ is unfavorable to the dimerization reaction of acetylene. To balance between high acetylene conversion and low loss rate of CuCl, the optimum mass percentage of HCl in the added hydrochloric acid was determined. The result showed the optimum mass percentage of HCl decreased from 5.0% to 3.2% when the space velocity of acetylene was from 140 h-1 to 360 h-1. The result in this work also indicated the pH of the Nieuwland catalyst should be kept in the range of 5.80-5.97 during the reaction process, which was good for both catalyst life and acetylene conversion.

Select

Hydrate-based carbon dioxide capture from simulated integrated gasification combined cycle gas Chungang Xu, Xiaosen Li*, Jing Cai, Zhaoyang Chen 2012, 21(5): 501-507.  DOI: 10.1016/S1003-9953(11)60397-6 摘要 ( 7957 )   The equilibrium hydrate formation conditions for CO2/H2 gas mixtures with different CO2 concentrations in 0.29 mol% TBAB aqueous solution are firstly measured. The results illustrate that the equilibrium hydrate formation pressure increases remarkably with the decrease of CO2 concentration in the gas mixture. Based on the phase equilibrium data, a three stages hydrate CO2 separation from integrated gasification combined cycle (IGCC) synthesis gas is investigated. Because the separation efficiency is quite low for the third hydrate separation, a hybrid CO2 separation process of two hydrate stages in conjunction with one chemical absorption process (absorption with MEA) is proposed and studied. The experimental results show H2 concentration in the final residual gas released from the three stages hydrate CO2 separation process was approximately 95.0 mol% while that released from the hybrid CO2 separation process was approximately 99.4 mol%. Thus, the hybrid process is possible to be a promising technology for the industrial application in the future.

Select

Initial estimation of hydrate formation temperature of sweet natural gases based on new empirical correlation Mohammad Mahdi Ghiasi* 2012, 21(5): 508-512.  DOI: 10.1016/S1003-9953(11)60398-8 摘要 ( 7919 )   Production, processing and transportation of natural gases can be significantly affected by clathrate hydrates. Knowing the gas analysis is crucial to predict the right conditions for hydrate formation. Nevertheless, Katz gas gravity method can be used for initial estimation of hydrate formation temperature (HFT) under the circumstances of indeterminate gas composition. So far several correlations have been proposed for gas gravity method, in which the most accurate and reliable one has belonged to Bahadori and Vuthaluru. The main objective of this study is to present a simple and yet accurate correlation for fast prediction of sweet natural gases HFT based on the fit to Katz gravity chart. By reviewing the error analysis results, one can discover that the new proposed correlation has the best estimation capability among the widely accepted existing correlations within the investigated range.

Select

Preferential oxidation of CO in excess H2 over CeO2/CuO catalyst: Effect of calcination temperature Zhiming Gao*, Ming Zhou, Hao Deng, Yong Yue 2012, 21(5): 513-518.  DOI: 10.1016/S1003-9953(11)60399-X 摘要 ( 8537 )   Different from the classical configuration CuO/CeO2 catalyst, the inverse configuration CeO2/CuO catalyst (atomic ratio of Ce/Cu = 10/100) was prepared by impregnation method. Five calcination temperatures were selected to investigate the interaction between CeO2 and CuO support. It is found that as calcination temperature increased from 500 to 900 ℃, sintering of CeO2 particles on the support occurred together with the diffusion of a portion of Ce4+ ions into CuO crystals, forming solid solution. Formation of interface complex Ce–O–Cu was suggested by TPR measurements. The catalyst calcined at 700 ℃ gives the highest activity for preferential oxidation of CO in excess H2 stream.

Select

Partial oxidation of methane in Ba0.5Sr0.5Co0.8Fe0.1Ni0.1O3-δ ceramic membrane reactor Ensieh Ganji Babakhani*, Jafar Towfighi, Zahra Taheri, Ali Nakhaei Pour 2012, 21(5): 519-525.  DOI: 10.1016/S1003-9953(11)60400-3 摘要 ( 8481 )   Ba0.5Sr0.5Co0.8Fe0.1Ni0.1O3-δ (BSCFNiO) perovskite oxides were synthesized using a combined EDTA-citrate complexing method, and then pressed into disk and applied in a membrane reactor. The performance of the BSCFNiO membrane reactor was studied for partial oxidation of methane over Ni/α-Al2O3 catalyst. The time dependence of oxygen permeation rate and catalytic performance of BSCFNiO membrane during the catalyst initiation stage were investigated at 850 ℃. In unsteady state, oxygen permeation rate, methane conversion and CO selectivity were closely related to the state of the catalyst. After 300 min from the initial time, the reaction condition reached to steady state and oxygen permeation rate were obtained about 11.7cm3·cm-2·min-1. Also, the performance of membrane reactor was studied at the temperatures between 750 and 950 ℃. The results demonstrated good performance for the membrane reactor, as CH4 conversion and CO selectivity permeation rate reached 98% and 97.5%, respectively, and oxygen permeation rate was about 14.5 cm3·cm-2·min-1 which was 6.8 times higher than that of air-helium gradient. Characterization of membrane surface by SEM after reaction showed that the original grains disappeared on both surfaces exposed to the air and reaction side, but XRD profile of the polished surface membrane indicated that the membrane bulk preserved the perovskite structure.

Select

Performance assessment of a spiral methanol to hydrogen fuel processor for fuel cell applications Foad Mehri, Majid Taghizadeh* 2012, 21(5): 526-533.  DOI: 10.1016/S1003-9953(11)60401-5 摘要 ( 8550 )   A novel design of plate-type microchannel reactor has been developed for fuel cell-grade hydrogen production. Commercial Cu/Zn/Al2O3 was used as catalyst for the reforming reaction, and its effectiveness was evaluated on the mole fraction of products, methanol conversion, hydrogen yield and the amount of carbon monoxide under various operating conditions. Subsequently, 0.5 wt% Ru/Al2O3 as methanation catalyst was prepared by impregnation method and coupled with MSR step to evaluate the capability of methanol processor for CO reduction. Based on the experimental results, the optimum conditions were obtained as feed flow rate of 5 mL/h and temperature of 250 ℃, leading to a low CO selectivity and high H2 yield. The designed reformer with catalyst coated layer was compared with the conventional packed bed reformer at the same operating conditions. The constructed fuel processor had a good performance and excellent capability for on-board hydrogen production.

Select

Experimental investigation of fluidized-bed reactor performance for oxidative coupling of methane S. Ja?o*, S. Sadjadi, H. R. Godini*, U. Simon, S. Arndt, O. G?rke, A. Berthold 2012, 21(5): 534-543.  DOI: 10.1016/S1003-9953(11)60402-7 摘要 ( 8206 )   Performance of the oxidative coupling of methane in fluidized-bed reactor was experimentally investigated using Mn-Na2WO4/SiO2, La2O3/CaO and La2O3-SrO/CaO catalysts. These catalysts were found to be stable, especially Mn-Na2WO4/SiO2 catalyst. The effect of sodium content of this catalyst was analyzed and the challenge of catalyst agglomeration was addressed using proper catalyst composition of 2%Mn-2.2%Na2WO4/SiO2. For other two catalysts, the effect of Lanthanum-Strontium content was analyzed and 10%La2O3-20%SrO/CaO catalyst was found to provide higher ethylene yield than La2O3/CaO catalyst. Furthermore, the effect of operating parameters such as temperature and methane to oxygen ratio were also reviewed. The highest ethylene and ethane (C2) yield was achieved with the lowest methane to oxygen ratio around 2. 40.5% selectivity to ethylene and ethane and 41% methane conversion were achieved over La2O3-SrO/CaO catalyst while over Mn-Na2WO4/SiO2 catalyst, 40% and 48% were recorded, respectively. Moreover, the consecutive effects of nitrogen dilution, ethylene to ethane production ratio and other performance indicators on the down-stream process units were qualitatively discussed and Mn-Na2WO4/SiO2 catalyst showed a better performance in the reactor and process scale analysis.

Select

Growth mechanism of palladium clusters on rutile TiO2(110) surface Weina Zhao, Huaxiang Lin, Yi Li, Yongfan Zhang, Xin Huang, Wenkai Chen* 2012, 21(5): 544-555.  DOI: 10.1016/S1003-9953(11)60403-9 摘要 ( 11352 )   Oxide-supported transition metal systems have been the subject of enormous interest due to the improvement of catalytic properties relative to the separate metal. Thus in this paper, we embark on a systematic study for Pdn (n = 1-5) clusters adsorbed on TiO2(110) surface based on DFT-GGA calculations utilizing periodic supercell models. A single Pd adatom on the defect-free surface prefers to adsorb at a hollow site bridging a protruded oxygen and a five-fold titanium atom along the [110] direction, while Pd dimer is located on the channels with the Pd–Pd bond parallel to the surface. According to the transition states (TSs) search, the adsorbed Pd trimer tends to triangular growth mode, rather than linear mode, while the Pd4 and Pd5 clusters prefer three-dimensional (3D) models. However, the oxygen vacancy has almost no influence on the promotion of Pdn cluster nucleation. Additionally, of particular significance is that the Pd-TiO2 interaction is the main driving force at the beginning of Pd nucleation, whereas the Pd–Pd interaction gets down to control the growth process of Pd cluster as the cluster gets larger. It is hoped that our theoretical study would shed light on further designing high-performance TiO2 supported Pd-based catalysts.

Select

Desulfurization kinetics of ZnO sorbent loaded on semi-coke support for hot coal gas Zhiwei Ma, Xianrong Zheng, Liping Chang, Ruiyuan He, Weiren Bao* 2012, 21(5): 556-562.  DOI: 10.1016/S1003-9953(11)60404-0 摘要 ( 7784 )   Zn-based sorbent (Z20SC) prepared through semi-coke support in 20 wt% zinc nitrate solution by high-pressure impregnation presents an excellent desulfurization capacity in hot coal gas, in which H2S can not be nearly detected in the outlet gas before 20 h breakthrough time. The effects of the main operational conditions and the particle size of Z20SC sorbent on its desulfurization performances sorbent were investigated in a fixed-bed reactor and the desulfurization kinetics of Z20SC sorbent removing H2S from hot coal gas was calculated based on experimental data. Results showed that the conversion of Z20SC sorbent desulfurization reaction increased with the decrease of the particle size of the sorbent and the increases of gas volumetric flow rate, reaction temperature and H2S content in inlet gas. Z20SC sorbent obtained from hydrothermal synthesis by high-pressure impregnation possessed much larger surface area and pore volume than semi-coke support, and they were significantly reduced after the desulfurization reaction. The equivalent grain model was reasonably used to analyze experimental data, in which ks = 4.382×10-3exp(-8.270×103/RgT) and Dep = 1.262×10-4exp(-1.522×104/RgT). It suggests that the desulfurization reaction of the Z20SC sorbent is mainly controlled by the chemical reaction in the initial stage and later by the diffusion through the reacted sorbent layer .

Select

Effect of copper loading on texture, structure and catalytic performance of Cu/SiO2 catalyst for hydrogenation of dimethyl oxalate to ethylene glycol Bo Zhang, Shengguo Hui, Suhua Zhang, Yang Ji, Wei Li, Dingye Fang* 2012, 21(5): 563-570.  DOI: 10.1016/S1003-9953(11)60405-2 摘要 ( 8078 )   Cu/SiO2 catalysts prepared by a convenient and efficient method using the urea hydrolysis deposition-precipitation (UHDP) technique have been proposed focusing on the effect of copper loading. The texture, structure and composition are systematically characterized by ICP, FT-IR, N2-physisorption, N2O chemisorption, TPR, XRD and XPS. The formation of copper phyllosilicate is observed in Cu/SiO2 catalyst by adopting UHDP method, and the amount of copper phyllosilicate is related to copper loading. It is found the structure properties and catalytic performance is profoundly affected by the amount of copper phyllosilicate. The excellent catalytic activity is attributed to the synergetic effect between Cu0 and Cu+. DMO conversion and EG selectivity are determined by the amount of Cu0 and Cu+, respectively. The proper copper loading (30 wt%) provides with the highest ratio of Cu+/Cu0, giving rise to the highest EG yield of 95% under the reaction conditions of p = 2.0 MPa, T = 473 K, H2/DMO = 80 and LHSV = 1.0 h-1.

Select

Oxidative reforming of methane for hydrogen and synthesis gas production: Thermodynamic equilibrium analysis Antonio C. D. Freitas, Reginaldo Guirardello* 2012, 21(5): 571-580.  DOI: 10.1016/S1003-9953(11)60406-4 摘要 ( 9195 )   A thermodynamic analysis of methane oxidative reforming was carried out by Gibbs energy minimization (at constant pressure and temperature) and entropy maximization (at constant pressure and enthalpy) methods, to determine the equilibrium compositions and equilibrium temperatures, respectively. Both cases were treated as optimization problems (non-linear programming formulation). The GAMS® 23.1 software and the CONOPT2 solver were used in the resolution of the proposed problems. The hydrogen and syngas production were favored at high temperatures and low pressures, and thus the oxygen to methane molar ratio (O2/CH4) was the dominant factor to control the composition of the product formed. For O2/CH4 molar ratios higher than 0.5, the oxidative reforming of methane presented autothermal behavior in the case of either utilizing O2 or air as oxidant agent, but oxidation reaction with air possessed the advantage of avoiding peak temperatures in the system, due to change in the heat capacity of the system caused by the addition of nitrogen. The calculated results were compared with previously published experimental and simulated data with a good agreement between them.

Select

Supported ZnO catalysts for the conversion of alkanes: About the metamorphosis of a heterogeneous catalyst S. Arndt, B. Uysal, A. Berthold, T. Otrebma, Y. Aksu, M. Driess, R. Schom?cker* 2012, 21(5): 581-594.  DOI: 10.1016/S1003-9953(11)60407-6 摘要 ( 8441 )   ZnO could be a suitable catalyst for the oxidative conversion of CH4, C2H6 and C3H8. However, the main drawback is its thermal instability. Therefore, ZnO supported on ZrO2, TiO2, γ-Al2O3 and SiO2 was investigated for the oxidative dehydrogenation of propane and ethane, and the oxidative coupling of methane. The stability of the supported ZnO is partially improved, but ZnO reacts with the support material, forming new compounds (Zn-zirconates, -titanates, -aluminates and -silicates), which already occurs below reaction temperature. This might also be the case for many other heterogeneous catalysts.

Select

Nickel ferrite spinel as catalyst precursor in the dry reforming of methane: Synthesis, characterization and catalytic properties Rafik Benrabaa, Hamza Boukhlouf, Axel L?fberg, Annick Rubbens, Rose-N?elle Vanni 2012, 21(5): 595-604.  DOI: 10.1016/S1003-9953(11)60408-8 摘要 ( 11160 )   Dry reforming of methane by CO2 using nickel ferrite as precursor of catalysts was investigated. Nickel ferrite crystalline particles were prepared by coprecipitation of nitrates with NaOH or ammonia followed by calcination, or by hydrothermal synthesis without calcination step. The textural and structural properties were determined by a number of analysis methods, including X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), among which X-ray diffraction (XRD) was at room and variable temperatures. All synthesized oxides showed the presence of micro or nanoparticles of NiFe2O4 inverse spinel, but Fe2O3 (hematite) was also present when ammonia was used for coprecipitation. The reducibility by hydrogen was studied by temperature-programmed reduction (TPR) and in situ XRD, which showed the influence of the preparation method. The surface area (BET), particle size (Rietveld refinement), as well as surface Ni/Fe atomic ratio (XPS) and the behavior upon reduction varied according to the synthesis method. The catalytic reactivity was investigated using isopropanol decomposition to determine the acid/base properties. The catalytic performance of methane reforming with CO2 was measured with and without the pre-treatment of catalysts under H2 in 650–800 ℃ range. The catalytic conversions of methane and CO2 were quite low but they increased when the catalysts were pre-reduced. A significant contribution of reverse water gas shift reaction accounted for the low values of H2/CO ratio. No coking was observed as shown by the reoxidation step performed after the catalytic reactions. The possible formation of nickel-iron alloy observed during the study of reducibility by hydrogen was invoked to account for the catalytic behavior.

Select

Comparing the deactivation behaviour of Co/CNT and Co/γ-Al2O3 nano catalysts in Fischer-Tropsch synthesis Ahmad Tavasoli*, Saba Karimi, Somayeh Taghavi, Zahra Zolfaghari, Hamideh Amirfir 2012, 21(5): 605-613.  DOI: 10.1016/S1003-9953(11)60409-X 摘要 ( 8946 )   An extensive study of Fischer-Tropsch (FT) synthesis on cobalt nano particles supported on γ-alumina and carbon nanotubes (CNTs) catalysts is reported. 20 wt% of cobalt is loaded on the supports by impregnation method. The deactivation of the two catalysts was studied at 220 ℃, 2 MP and 2.7 L/h feed flow rate using a fixed bed micro-reactor. The calcined fresh and used catalysts were characterized extensively and different sources of catalysts deactivation were identified. Formation of cobalt-support mixed oxides in the form of xCoO. yAl2O3 and cobalt aluminates formation are the main sources of the Co/γ-Al2O3 catalyst deactivation. However sintering and cluster growth of cobalt nano particles are the main sources of the Co/CNTs catalyst deactivation. In the case of the Co/γ-Al2O3 catalyst, after 720 h on stream of continuous FT synthesis increased the average cobalt nano particles diameter from 15.9 to 18.4 nm, whereas, under the same reaction conditions the average cobalt nano particles diameter of the Co/CNTs increased from 11.2 to 17.8 nm. Although, the initial FT activity of the Co/CNTs was 26% higher than that of the Co/γ-Al2O3, the FT activity after 720 h on stream decreased over the Co/CNTs by 49% and that over the Co/γ-Al2O3 by 32%. For the Co/γ-Al2O3 catalyst 6.7% of total activity loss and for the Co/CNTs catalyst 11.6% of total activity loss cannot be recovered after regeneration of the catalyst at the same conditions of the first regeneration step. It is concluded that using CNTs as cobalt catalyst support is beneficial in carbon utilization as compared to γ-Al2O3 support, but the Co/CNTs catalyst is more susceptible for deactivation.