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Probing the catalytic activity of M-N

Fan Ge, Qingan Qiao, Xin Chen, You Wu

《化学科学与工程前沿(英文)》 2021年 第15卷 第5期   页码 1206-1216 doi: 10.1007/s11705-020-2017-7

摘要: In this work, the detailed oxygen reduction reaction (ORR) catalytic performance of M-N O (M= Fe, Co, and Ni; = 1–4) has been explored via the detailed density functional theory method. The results suggest that the formation energy of M-N O shows a good linear relationship with the number of doped O atoms. The adsorption manner of O on M-N O changed from end-on ( = 1 and 2) to side-on ( = 3 and 4), and the adsorption strength gradually increased. Based on the results for binding strength of ORR intermediates and the Gibbs free energy of ORR steps on the studied catalysts, we screened out two highly active ORR catalysts, namely Co-N O and Ni-N O , which possess very small overpotentials of 0.27 and 0.32 V, respectively. Such activities are higher than the precious Pt catalyst. Electronic structure analysis reveals one of the reasons for the higher activity of Co-N O and Ni-N O is that they have small energy gaps and moderate highest occupied molecular orbital energy levels. Furthermore, the results of the density of states reveal that the O doping can improve the electronic structure of the original catalyst to tune the adsorption of the ORR intermediates.

关键词: M-N-C catalyst     oxygen doping     oxygen reduction reaction     catalytic activity     density functional theory    

New insight into effect of potential on degradation of Fe-N-C catalyst for ORR

Yanyan GAO, Manman QI, Liang HE, Haiping CHEN, Wenzhe LUO, Ming HOU, Zhigang SHAO

《能源前沿(英文)》 2021年 第15卷 第2期   页码 421-430 doi: 10.1007/s11708-021-0727-2

摘要: In recent years, Fe-N-C catalyst is particularly attractive due to its high oxygen reduction reaction (ORR) activity and low cost for proton exchange membrane fuel cells (PEMFCs). However, the durability problems still pose challenge to the application of Fe-N-C catalyst. Although considerable work has been done to investigate the degradation mechanisms of Fe-N-C catalyst, most of them are simply focused on the active-site decay, the carbon oxidation, and the demetalation problems. In fact, the 2e pathway in the ORR process of Fe-N-C catalyst would result in the formation of H O , which is proved to be a key degradation source. In this paper, a new insight into the effect of potential on degradation of Fe-N-C catalyst was provided by quantifying the H O intermediate. In this case, stability tests were conducted by the potential-static method in O saturated 0.1 mol/L HClO . During the tests, H O was quantified by rotating ring disk electrode (RRDE). The results show that compared with the loading voltage of 0.4 V, 0.8 V, and 1.0 V, the catalysts being kept at 0.6 V exhibit a highest H O yield. It is found that it is the combined effect of electrochemical oxidation and chemical oxidation (by aggressive radicals like H O /radicals) that triggered the highest H O release rate, with the latter as the major cause.

关键词: proton exchange membrane fuel cells (PEMFCs)     oxygen reduction reaction (ORR)     Fe-N-C catalyst     potential     H2O2     degradation    

ThMn12型永磁合金 Review

G.C. Hadjipanayis, A.M. Gabay, A.M. Schönhöbel, A. Martín-Cid, J.M. Barandiaran, D. Niarchos

《工程(英文)》 2020年 第6卷 第2期   页码 140-146 doi: 10.1016/j.eng.2018.12.011

摘要:

具有四方ThMn12型结构的富铁化合物有潜力满足当下人们对于高磁能积、工作温度为150~200 ℃的贫稀土永磁体的需求。尽管磁体制备技术的发展滞后于相关磁性材料的研究是正常的,但对于ThMn12型磁性材料而言,这种研究进展的差异非常显著。近年来,随着以含少量结构稳定元素(如SmFe11V或Sm0.8Zr0.2Fe9.2Co2.3Ti0.5)或者不含该类元素的材料(如SmFe9.6Co2.4薄膜)为基础所合成的具有优异内禀磁性化合物研究的突破,这一差距进一步扩大。在日益强大的理论计算的帮助下,人们对于理想的化合物的探寻从未停步。遗憾的是,基于聚合物键合填隙改性粉末的磁体的研究仍然处于边缘阶段。人们发现,引入镧(La)可以提高Sm(Fe,Ti)12中少数低熔点相的稳定性,从而首次使得液相烧结成为可能。然而,La金属的高反应活性会明显地破坏材料的矫顽力(Hc)。最初被抑制的ThMn12型相的可控结晶使得“块状”磁硬化成为可能,这不仅在Sm-Fe-V合金中可以实现(自20世纪90年代便为人所知),并且在添加La的(Ce,Sm)(Fe,Ti)12合金中也可以实现。然而,块状硬化所得的合金的性能仍然不能令人满意。机械化学合成的(Sm,Zr)(Fe,Si)12和(Sm,Zr)(Fe,Co,Ti)12粉末可能适合烧结成具有高强度的全致密磁体,尽管在此之前,两者都已开发出较高的各向异性,而后一种合金已开发出较高的矫顽力。

关键词: 永磁体,稀土永磁体,ThMn 12 结构    

Coupling the porous conditional moment closure with the random pore model: applications to gasification and CO

N. SAULOV, C. R. CHODANKA, M. J. CLEARY, A. Y. KLIMENKO

《化学科学与工程前沿(英文)》 2012年 第6卷 第1期   页码 84-93 doi: 10.1007/s11705-011-1164-2

摘要: Gasification of coal or biomass with in situ CO capture simultaneously allows production of clean hydrogen at relatively low cost and reduced emission of CO into the atmosphere. Clearly, this technology has a great potential for a future carbon constrained economy. Therefore, the development of a comprehensive, physically-based gasifier model is important. The sub-models that describe reactive transport processes in coal particles as well as in particles of CO sorbent material are among the key sub-models, which provide a necessary input for an overall gasifier model. Both coal and sorbent are materials that have complicated pore structures. The porous conditional moment closure (PCMC) model proves to be adequate for modeling reactive transport through porous media with fixed pore structure. Consumption of coal in the heterogeneous gasification reaction, however, widens the pores and reduces the surface area available for this reaction. At the same time, formation of a carbonate layer narrows the pores in the sorbent material and reduces the reaction rate of CO sorption. In both cases the pore structures are affected. Such changes are not taken into account in the existing PCMC model. In this study, we obtain the parameters of the diffusive tracer distribution based on the pore size distribution given by the widely applied random pore model (RPM), while coupling PCMC with RPM. Such coupling allows taking into account changes in pore structure caused by heterogeneous reactions and thus improves the accuracy of these key sub-models.

关键词: gasification     CO2 capture     PCMC     RPM    

Enhancing the efficiency of nitrogen removing bacterial population to a wide range of C:N ratio (1.5:1 to 14:1) for simultaneous C & N removal

《环境科学与工程前沿(英文)》 2022年 第16卷 第8期 doi: 10.1007/s11783-022-1522-y

摘要:

• Simultaneous C & N removal in Methammox occurs at wide C:N ratio.

关键词: Methanogens     Biological Nitrogen Removal (BNR)     Simultaneous     Methammox     C:N ratio    

Controllable synthesis of a large TS-1 catalyst for clean epoxidation of a C=C double bond under mild

《化学科学与工程前沿(英文)》 2023年 第17卷 第6期   页码 772-783 doi: 10.1007/s11705-022-2280-x

摘要: Development of a titanium silicalite-1 (TS-1) catalyst with good crystallinity and a four-coordinate Ti framework is critical for efficient catalytic oxidation reaction under mild conditions. Herein, a size-controlled TS-1 zeolite (TS-1#0.1ACh (acetylcholine)) was synthesized via steam-assisted crystallization by introducing acetylcholine as a crystal growth modifier in the preparation process, and TS-1#0.1ACh was also employed in epoxidations of different substrates containing C=C double bonds. The crystalline sizes of the as-synthesized TS-1#0.1ACh catalysts were controlled with the acetylcholine content, and characterization results showed that the particle sizes of highly crystalline TS-1#0.1ACh zeolite reached 3.0 μm with a good Ti framework. Throughout the synthetic process, the growth rate of the crystals was accelerated by electrostatic interactions between the connected hydroxyl groups of the acetylcholine modifier and the negatively charged skeleton of the pre-zeolites. Furthermore, the TS-1#0.1ACh catalyst demonstrated maximum catalytic activity, good selectivity and high stability during epoxidation of allyl chloride. Importantly, the TS-1#0.1ACh catalyst was also highly versatile and effective with different unsaturated substrates. These findings may provide novel, easily separable and large TS-1 catalysts for efficient and clean industrial epoxidations of C=C double bonds.

关键词: size-controlled TS-1     crystal modifier     steam-assisted crystallization     epoxidation    

Monte Carlo simulation of the PEMFC catalyst layer

WANG Hongxing, CAO Pengzhen, WANG Yuxin

《化学科学与工程前沿(英文)》 2007年 第1卷 第2期   页码 146-150 doi: 10.1007/s11705-007-0027-3

摘要: The performance of the polymer electrolyte membrane fuel cell (PEMFC) is greatly controlled by the structure of the catalyst layer. Low catalyst utilization is still a significant obstacle to the commercialization of the PEMFC. In order to get a fundamental understanding of the electrode structure and to find the limiting factor in the low catalyst utilization, it is necessary to develop the mechanical model on the effect of catalyst layer structure on the catalyst utilization and the performance of the PEMFC. In this work, the structure of the catalyst layer is studied based on the lattice model with the Monte Carlo simulation. The model can predict the effects of some catalyst layer components, such as Pt/C catalyst, electrolyte and gas pores, on the utilization of the catalyst and the cell performance. The simulation result shows that the aggregation of conduction grains can greatly affect the degree of catalyst utilization. The better the dispersion of the conduction grains, the larger the total effective area of the catalyst is. To achieve higher utilization, catalyst layer components must be distributed by means of engineered design, which can prevent aggregation.

关键词: catalyst utilization     PEMFC     commercialization     Pt/C catalyst     conduction    

A density functional theory study of methane activation on MgO supported NiM cluster: role of M on C–H

《化学科学与工程前沿(英文)》 2022年 第16卷 第10期   页码 1485-1492 doi: 10.1007/s11705-022-2169-8

摘要: Methane activation is a pivotal step in the application of natural gas converting into high-value added chemicals via methane steam/dry reforming reactions. Ni element was found to be the most widely used catalyst. In present work, methane activation on MgO supported Ni–M (M = Fe, Co, Cu, Pd, Pt) cluster was explored through detailed density functional theory calculations, compared to pure Ni cluster. CH4 adsorption on Cu promoted Ni cluster requires overcoming an energy of 0.07 eV, indicating that it is slightly endothermic and unfavored to occur, while the adsorption energies of other promoters M (M = Fe, Co, Pd and Pt) are all higher than that of pure Ni cluster. The role of M on the first C–H bond cleavage of CH4 was investigated. Doping elements of the same period in Ni cluster, such as Fe, Co and Cu, for C–H bond activation follows the trend of the decrease of metal atom radius. As a result, Ni–Fe shows the best ability for C–H bond cleavage. In addition, doping the elements of the same family, like Pd and Pt, for CH4 activation is according to the increase of metal atom radius. Consequently, C–H bond activation demands a lower energy barrier on Ni–Pt cluster. To illustrate the adsorptive dissociation behaviors of CH4 at different Ni–M clusters, the Mulliken atomic charge was analyzed. In general, the electron gain of CH4 binding at different Ni–M clusters follows the sequence of Ni–Cu (–0.02 e) < Ni (–0.04 e) < Ni–Pd (–0.08 e) < Ni–Pt (–0.09 e) < Ni–Co (–0.10 e) < Ni–Fe (–0.12 e), and the binding strength between catalysts and CH 4 raises with the CH4 electron gain increasing. This work provides insights into understanding the role of promoter metal M on thermal-catalytic activation of CH4 over Ni/MgO catalysts, and is useful to interpret the reaction at an atomic scale.

关键词: CH4 dissociation     Ni–M     C–H bond activation     charge transfer    

Effect of noble metal nanoparticle size on CN bond cleavage performance in hydrodenitrogenation: a study

《化学科学与工程前沿(英文)》 2023年 第17卷 第12期   页码 1986-2000 doi: 10.1007/s11705-023-2337-5

摘要: Breakage of the C–N bond is a structure sensitive process, and the catalyst size significantly affects its activity. On the active metal nanoparticle scale, the role of catalyst size in C–N bond cleavage has not been clearly elucidated. So, Ru catalysts with variable nanoparticle sizes were obtained by modulating the reduction temperature, and the catalytic activity was evaluated using 1,2,3,4-tetrahydroquinoline and o-propylaniline with different C–N bond hybridization patterns as reactants. Results showed a 13 times higher reaction rate for sp3-hybridized C–N bond cleavage than sp2-hybridized C–N bond cleavage, while the reaction rate tended to increase first and then decrease as the catalyst nanoparticle size increased. Different concentrations of terrace, step, and corner sites were found in different sizes of Ru nanoparticles. The relationship between catalytic site variation and C–N bond cleavage activity was further investigated by calculating the turnover frequency values for each site. This analysis indicates that the variation of different sites on the catalyst is the intrinsic factor of the size dependence of C–N bond cleavage activity, and the step atoms are the active sites for the C–N bond cleavage. When Ru nanoparticles are smaller than 1.9 nm, they have a strong adsorption effect on the reactants, which will affect the catalytic performance of the Ru catalyst. Furthermore, these findings were also confirmed on other metallic Pd/Pt catalysts. The role of step sites in C–N bond cleavage was proposed using the density function theory calculations. The reactants have stronger adsorption energies on the step atoms, and step atoms have d-band center nearer to the Fermi level. In this case, the interaction with the reactant is stronger, which is beneficial for activating the C–N bond of the reactant.

关键词: sp3/sp2-hybridized C–N bond     noble metal nanoparticle     catalytic active site     turnover frequency     DFT    

Application of statistical design for the production of inulinase by

M. DILIPKUMAR, M. RAJASIMMAN, N. RAJAMOHAN

《化学科学与工程前沿(英文)》 2011年 第5卷 第4期   页码 463-470 doi: 10.1007/s11705-011-1112-1

摘要: A Plackett-Burman design was employed for screening 18 nutrient components for the production of inulinase using sp. and pressmud as the substrate via solid-state fermentation (SSF). From the experiments, three nutrients viz. yeast extract, FeSO ·7H O, and NH NO were found to be the most significant components. Hence these three components were selected and optimized using Response Surface Methodology (RSM). The optimum conditions are: yeast extract 0.00274 g/gds, FeSO ·7H O 0.00011 g/gds and NH NO 0.00772 g/gds. The effect of the substrate concentration and initial moisture content were also studied. A substrate concentration of 12 g and an initial moisture content of 65% are optimum for the maximum production of inulinase (89 U/gds).

关键词: inulinase     pressmud     Response Surface Methodology (RSM)     streptomyces sp    

Atomistic simulations of plasma catalytic processes

Erik C. Neyts

《化学科学与工程前沿(英文)》 2018年 第12卷 第1期   页码 145-154 doi: 10.1007/s11705-017-1674-7

摘要: There is currently a growing interest in the realisation and optimization of hybrid plasma/catalyst systems for a multitude of applications, ranging from nanotechnology to environmental chemistry. In spite of this interest, there is, however, a lack in fundamental understanding of the underlying processes in such systems. While a lot of experimental research is already being carried out to gain this understanding, only recently the first simulations have appeared in the literature. In this contribution, an overview is presented on atomic scale simulations of plasma catalytic processes as carried out in our group. In particular, this contribution focusses on plasma-assisted catalyzed carbon nanostructure growth, and plasma catalysis for greenhouse gas conversion. Attention is paid to what can routinely be done, and where challenges persist.

关键词: atomic scale simulation     plasma-catalyst    

Effects of preparation methods of support on the properties of nickel catalyst for hydrogenation of m-dinitrobenzene

LIU Yingxin, WEI Zuojun, CHEN Jixiang, ZHANG Jiyan

《化学科学与工程前沿(英文)》 2007年 第1卷 第3期   页码 287-291 doi: 10.1007/s11705-007-0052-2

摘要: Using tetraethyl orthosilicate (TEOS) as the precursor of silica, the silica aerogel and xerogel, which were used as supports of nickel-based catalysts for liquid hydrogenation of -dinitrobenzene to -phenylenediamine, were prepared by the sol-gel method combined with supercritical drying (SCD) and conventional drying, respectively. Then, a series of nickel-based catalyst samples supported on these supports were prepared by the incipient wetness impregnation method with an aqueous solution of nickel nitrate as well as lanthanum nitrate as impregnation liquids. Based on the characterization results of nitrogen adsorption-desorption (BET), X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature-programmed desorption of hydrogen (H-TPD), and catalytic activity evaluation, the physico-chemical properties and catalytic performances of the catalysts were investigated. The results show that the nickel crystallites on the binary nickel catalyst using silica aerogel as support are of smaller particle size. However, compared with the sample supported on silica xerogel, the nickel catalyst supported on the silica aerogel exhibits lower activity and selectivity for the hydrogenation of -dinitrobenzene because it has a lesser amount of active sites and weaker absorption ability to reactants caused by sintering of the nickel crystallites. The addition of promoter LaO could increase the activity and selectivity of the catalysts. Among all the nickel-based catalyst samples prepared, the LaO promoted ternary nickel-based catalyst supported on silica xerogel exhibits the highest activity and selectivity for the hydrogenation of -dinitrobenzene to -phenylenediamine, which could be attributed to its highest active surface area and appropriate absorption strength to reactants. Over this promising catalyst, the conversion of -dinitrobenzene and the yield of -phenylenediamine could reach 97.0% and 93.1%, respectively, under proper reaction conditions of hydrogen pressure 2.6 MPa, temperature 373 K, and reaction time 1 h.

Uncertainty propagation analysis by an extended sparse grid technique

JIA, C. JIANG, C. M. FU, B. Y. NI, C. S. WANG, M. H. PING

《机械工程前沿(英文)》 2019年 第14卷 第1期   页码 33-46 doi: 10.1007/s11465-018-0514-x

摘要: In this paper, an uncertainty propagation analysis method is developed based on an extended sparse grid technique and maximum entropy principle, aiming at improving the solving accuracy of the high-order moments and hence the fitting accuracy of the probability density function (PDF) of the system response. The proposed method incorporates the extended Gauss integration into the uncertainty propagation analysis. Moreover, assisted by the Rosenblatt transformation, the various types of extended integration points are transformed into the extended Gauss-Hermite integration points, which makes the method suitable for any type of continuous distribution. Subsequently, within the sparse grid numerical integration framework, the statistical moments of the system response are obtained based on the transformed points. Furthermore, based on the maximum entropy principle, the obtained first four-order statistical moments are used to fit the PDF of the system response. Finally, three numerical examples are investigated to demonstrate the effectiveness of the proposed method, which includes two mathematical problems with explicit expressions and an engineering application with a black-box model.

关键词: uncertainty propagation analysis     extended sparse grid     maximum entropy principle     extended Gauss integration     Rosenblatt transformation     high-order moments analysis    

Negative weights in network time model

Zoltán A. VATTAI, Levente MÁLYUSZ

《工程管理前沿(英文)》 2022年 第9卷 第2期   页码 268-280 doi: 10.1007/s42524-020-0109-1

摘要: Time does not go backward. A negative duration, such as “time period” at first sight is difficult to interpret. Previous network techniques (CPM/PERT/PDM) did not support negative parameters and/or loops (potentially necessitating recursive calculations) in the model because of the limited computing and data storage capabilities of early computers. Monsieur Roy and John Fondahl implicitly introduced negative weights into network techniques to represent activities with fixed or estimated durations (MPM/PDM). Subsequently, the introduction of negative lead and/or lag times by software developers (IBM) apparently overcome the limitation of not allowing negative time parameters in time model. Referring to general digraph (Event on Node) representation where activities are represented by pairs of nodes and pairwise relative time restrictions are represented by weighted arrows, we can release most restraints in constructing the graph structure (incorporating the dynamic model of the inner logic of time plan), and a surprisingly flexible and handy network model can be developed that provides all the advantages of the abovementioned techniques. This paper aims to review the theoretical possibilities and technical interpretations (and use) of negative weights in network time models and discuss approximately 20 types of time-based restrictions among the activities of construction projects. We focus on pure relative time models, without considering other restrictions (such as calendar data, time-cost trade-off, resource allocation or other constraints).

关键词: graph technique     network technique     construction management     scheduling    

Catalytic activity of manganese oxide supported on alumina in the synthesis of quinoxalines

Rekha M., H. Kathyayini, N. Nagaraju

《化学科学与工程前沿(英文)》 2013年 第7卷 第4期   页码 415-421 doi: 10.1007/s11705-013-1360-3

摘要: Two catalysts, alumina and manganese oxide supported on alumina, have been prepared by calcination and precipitation-impregnation methods, respectively. The catalysts are characterised by the following techniques: Brunner-Emmett-Teller-N adsorption-desorption for surface area, temperature programmed desorption of NH and -butyl amine back titration methods for surface acidity, powder X-ray diffraction for textural properties, and Fourier transform infrared spectroscopy for the anionic radicals. The catalytic activity has been determined under heterogeneous conditions in the condensation reaction between -phenylenediamine and benzil. The product purity is checked by thin-layer chromatography and melting point. The products are also analysed by LC-MS and H-NMR techniques. The yields of the products have been found to be good and catalysts exhibited excellent recyclability. The effect of changing the reaction parameters such as temperature, reaction time, amount of the catalyst, nature of solvent and molar ratio of reactants on the yield of the product has been studied. The surface acidity of the catalysts plays an important role in activating the reaction.

关键词: alumina     manganese oxide deposited on alumina     quinoxaline synthesis    

标题 作者 时间 类型 操作

Probing the catalytic activity of M-N

Fan Ge, Qingan Qiao, Xin Chen, You Wu

期刊论文

New insight into effect of potential on degradation of Fe-N-C catalyst for ORR

Yanyan GAO, Manman QI, Liang HE, Haiping CHEN, Wenzhe LUO, Ming HOU, Zhigang SHAO

期刊论文

ThMn12型永磁合金

G.C. Hadjipanayis, A.M. Gabay, A.M. Schönhöbel, A. Martín-Cid, J.M. Barandiaran, D. Niarchos

期刊论文

Coupling the porous conditional moment closure with the random pore model: applications to gasification and CO

N. SAULOV, C. R. CHODANKA, M. J. CLEARY, A. Y. KLIMENKO

期刊论文

Enhancing the efficiency of nitrogen removing bacterial population to a wide range of C:N ratio (1.5:1 to 14:1) for simultaneous C & N removal

期刊论文

Controllable synthesis of a large TS-1 catalyst for clean epoxidation of a C=C double bond under mild

期刊论文

Monte Carlo simulation of the PEMFC catalyst layer

WANG Hongxing, CAO Pengzhen, WANG Yuxin

期刊论文

A density functional theory study of methane activation on MgO supported NiM cluster: role of M on C–H

期刊论文

Effect of noble metal nanoparticle size on CN bond cleavage performance in hydrodenitrogenation: a study

期刊论文

Application of statistical design for the production of inulinase by

M. DILIPKUMAR, M. RAJASIMMAN, N. RAJAMOHAN

期刊论文

Atomistic simulations of plasma catalytic processes

Erik C. Neyts

期刊论文

Effects of preparation methods of support on the properties of nickel catalyst for hydrogenation of m-dinitrobenzene

LIU Yingxin, WEI Zuojun, CHEN Jixiang, ZHANG Jiyan

期刊论文

Uncertainty propagation analysis by an extended sparse grid technique

JIA, C. JIANG, C. M. FU, B. Y. NI, C. S. WANG, M. H. PING

期刊论文

Negative weights in network time model

Zoltán A. VATTAI, Levente MÁLYUSZ

期刊论文

Catalytic activity of manganese oxide supported on alumina in the synthesis of quinoxalines

Rekha M., H. Kathyayini, N. Nagaraju

期刊论文