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Solid-state NMR for metal-containing zeolites: From active sites to reaction mechanism

Xingling Zhao, Jun Xu, Feng Deng

《化学科学与工程前沿（英文）》 2020年 第14卷 第2期   页码 159-187 doi: 10.1007/s11705-019-1885-1

摘要： Metal-containing zeolite catalysts have found a wide range of applications in heterogeneous catalysis. To understand the nature of metal active sites and the reaction mechanism over such catalysts is of great importance for the establishment of structure-activity relationship. The advanced solid-state NMR (SSNMR) spectroscopy is robust in the study of zeolites and zeolite-catalyzed reactions. In this review, we summarize recent developments and applications of SSNMR for exploring the structure and property of active sites in metal-containing zeolites. Moreover, detailed information on host-guest interactions in the relevant zeolite catalysis obtained by SSNMR is also discussed. Finally, we highlight the mechanistic understanding of catalytic reactions on metal-containing zeolites based on the observation of key surface species and active intermediates.

关键词： metal-containing zeolites     solid-state NMR     active site     host-guest interaction     reaction mechanism    

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Multifunctional heteroatom zeolites: construction and applications

《化学科学与工程前沿（英文）》 2021年 第15卷 第6期   页码 1462-1486 doi: 10.1007/s11705-021-2099-x

摘要： Multifunctional heteroatom zeolites have drawn broad attentions due to the possible synergistic effects in the catalytic reactions. Remarkable achievements have been made on the synthesis, characterization and catalytic applications of multifunctional heteroatom zeolite, while a review on this important topic is still missing. Herein, current research status of multifunctional heteroatom zeolites is briefly summarized, aiming to boost further researches. First, the synthesis strategies toward heteroatom zeolites are introduced, including the direct synthesis and postsynthesis routes; then, the spectroscopic techniques to identify the existing states of heteroatom sites and the corresponding physiochemical properties are shown and compared; finally, the catalytic applications of multifunctional heteroatom zeolites in various chemical reactions, especially in one-step tandem reactions, are discussed.

关键词： zeolite     multifunctional active sites     heteroatom     characterization     catalysis    

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noble metal nanoparticle size on C–N bond cleavage performance in hydrodenitrogenation: a study of activesites

《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    

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Insights into carbon-based materials for catalytic dehydrogenation of low-carbon alkanes and ethylbenzene

《化学科学与工程前沿（英文）》 2023年 第17卷 第11期   页码 1623-1648 doi: 10.1007/s11705-023-2328-6

摘要： Direct dehydrogenation with high selectivity and oxidative dehydrogenation with low thermal limit has been regarded as promising methods to solve the increasing demands of light olefins and styrene. Metal-based catalysts have shown remarkable performance for these reactions, such as Pt, CrOx, Co, ZrOx, Zn and V. Compared with metal-based catalysts, carbon materials with stable structure, rich pore texture and large surface area, are ideal platforms as the catalysts and the supports for dehydrogenation reactions. In this review, carbon materials applied in direct dehydrogenation and oxidative dehydrogenation reactions including ordered mesoporous carbon, carbon nanodiamond, carbon nanotubes, graphene and activated carbon, are summarized. A general introduction to the dehydrogenation mechanism and active sites of carbon catalysts is briefly presented to provide a deep understanding of the carbon-based materials used in dehydrogenation reactions. The unique structure of each carbon material is presented, and the diversified synthesis methods of carbon catalysts are clarified. The approaches for promoting the catalytic activity of carbon catalysts are elaborated with respect to preparation method optimization, suitable structure design and heteroatom doping. The regeneration mechanism of carbon-based catalysts is discussed for providing guidance on catalytic performance enhancement. In addition, carbon materials as the support of metal-based catalysts contribute to exploiting the excellent catalytic performance of catalysts due to superior structural characteristics. In the end, the challenges in current research and strategies for future improvements are proposed.

关键词： carbon materials     dehydrogenation     active sites     mechanism     catalytic performance     support    

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High-gravity intensified iron-carbon micro-electrolysis for degradation of dinitrotoluene

《化学科学与工程前沿（英文）》 2023年 第17卷 第10期   页码 1595-1605 doi: 10.1007/s11705-022-2204-9

摘要： The application of iron–carbon (Fe–C) micro-electrolysis to wastewater treatment is limited by the passivation potential of the Fe–C packing. In order to address this problem, high-gravity intensified Fe–C micro-electrolysis was proposed in this study for degradation of dinitrotoluene wastewater in a rotating packed bed (RPB) using commercial Fe–C particles as the packing. The effects of reaction time, high-gravity factor, liquid flow rate and initial solution pH were investigated. The degradation intermediates were determined by gas chromatography-mass spectrometry, and the possible degradation pathways of nitro compounds by Fe–C micro-electrolysis in RPB were also proposed. It is found that under optimal conditions, the removal rate of nitro compounds reaches 68.4% at 100 min. The removal rate is maintained at approximately 68% after 4 cycles in RPB, but it is decreased substantially from 57.9% to 36.8% in a stirred tank reactor. This is because RPB can increase the specific surface area and the renewal of the liquid–solid interface, and as a result the degradation efficiency of Fe–C micro-electrolysis is improved and the active sites on the Fe–C surface can be regenerated for continuous use. In conclusion, high-gravity intensified Fe–C micro-electrolysis can weaken the passivation of Fe–C particles and extend their service life.

关键词： high-gravity technology     rotating packed bed     Fe–C micro-electrolysis     dinitrotoluene wastewater     active sites    

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Effects of preparation methods on the activity of CuO/CeO

Huanhuan Shang, Xiaoman Zhang, Jing Xu, Yifan Han

《化学科学与工程前沿（英文）》 2017年 第11卷 第4期   页码 603-612 doi: 10.1007/s11705-017-1661-z

摘要： CO oxidation has been investigated on three CuO/CeO catalysts prepared by impregnation, co-precipitation and mechanical mixing. The origin of active sites was explored by the multiple techniques. The catalyst prepared by impregnation has more highly dispersed CuO and stronger interactions between CuO and CeO to promote the reduction of CuO to Cu species at the Cu-Ce interface, leading to its highest catalytic activity. For the catalyst prepared by co-precipitation, solid solution structures observed in Raman spectra suppress the formation of the Cu-Ce interface, where the adsorbed CO will react with active lattice oxygen to form CO , and thus it displays a lower catalytic performance. No Cu-Ce interface exists in the catalyst prepared by the mechanical mixing method due to the separate phases of CuO and CeO , resulting in its lowest activity among the three catalysts.

关键词： CuO/CeO2     CO oxidation     interfaces     structure-performance relationship     active sites    

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Microemulsion-mediated hydrothermal synthesis of flower-like MoS

Yuxia Jiang, Donge Wang, Zhendong Pan, Huaijun Ma, Min Li, Jiahe Li, Anda Zheng, Guang Lv, Zhijian Tian

《化学科学与工程前沿（英文）》 2018年 第12卷 第1期   页码 32-42 doi: 10.1007/s11705-017-1677-4

摘要： Flower-like intercalated MoS nanomaterials have been successfully synthesized via a microemulsion-mediated hydrothermal (MMH) method, and characterized by X-ray diffraction, Raman spectroscopy, element analysis, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy in detail. Their catalytic performance for anthracene hydrogenation was evaluated using a slurry-bed batch reactor with an initial hydrogen pressure of 80 bar at 350 °C for 4 h. The intercalated MoS nanoflowers synthesized from Na MoO (MoS -S) and H MoO (MoS -A) as molybdenum precursors have diameters of about 150 and 50 nm, respectively. MoS nanosheets on MoS -S and MoS -A possess stacking layer numbers of 5–10 and 2–5, and slab lengths of about 15 and 10 nm, respectively. The interlayer distances of MoS -S and MoS -A are both enlarged from 0.62 nm to about 0.95 nm due to the intercalation of NH and surfactant molecules. The MoS nanoflowers have high catalytic activities for anthracene hydrogenation. The selectivity for octahydroanthracene, a deeply hydrogenated product, over MoS -A is 89.8%, which is 31.0 times higher than that over commercial bulk MoS . Fully hydrogenated product (perhydroanthracene) was also detected over MoS nanoflowers with a selectivity of 3.7%. The enhanced hydrogenation activities of MoS nanoflowers can be ascribed to the high exposure of catalytic active sites, resulting from the smaller particle size, fewer stacking layer, shorter slab length and enlarged interlayer distance of MoS nanoflowers compared with commercial bulk MoS . In addition, a possible growth mechanism of MoS nanoflowers synthesized via the MMH method was proposed.

关键词： microemulsion     intercalated MoS2     catalytic hydrogenation     active sites    

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Dual-functional sites for synergistic adsorption of Cr(VI) and Sb(V) by polyaniline-TiO hydrate: Adsorptionbehaviors, sites and mechanisms

《环境科学与工程前沿（英文）》 2022年 第16卷 第8期 doi: 10.1007/s11783-022-1526-7

摘要：

• PANI/Ti(OH)n(4–n)+ exhibited excellent adsorption capacity and reusability.

关键词： Polyaniline/TiO2     Chromium     Antimony     Adsorption     Desorption     Mechanism    

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Influence of Fe on electrocatalytic activity of iron-nitrogen-doped carbon materials toward oxygen reduction reaction

Lin LI, Cehuang FU, Shuiyun SHEN, Fangling JIANG, Guanghua WEI, Junliang ZHANG

《能源前沿（英文）》 2022年 第16卷 第5期   页码 812-821 doi: 10.1007/s11708-020-0669-0

摘要： The development of highly active nitrogen-doped carbon-based transition metal (M-N-C) compounds for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) greatly helps reduce fuel cell cost, thus rapidly promoting their commercial applications. Among different M-N-C electrocatalysts, the series of Fe-N-C materials are highly favored because of their high ORR activity. However, there remains a debate on the effect of Fe, and rare investigations focus on the influence of Fe addition in the second heat treatment usually performed after acid leaching in the catalyst synthesis. It is thus very critical to explore the influences of Fe on the ORR electrocatalytic activity, which will, in turn, guide the design of Fe-N-C materials with enhanced performance. Herein, a series of Fe-N-C electrocatalysts are synthesize and the influence of Fe on the ORR activity are speculated both experimentally and theoretically. It is deduced that the active site lies in the structure of Fe-N , accompanied with the addition of appropriate Fe, and the number of active sites increases without the occurrence of agglomeration particles. Moreover, it is speculated that Fe plays an important role in stabilizing N as well as constituting active sites in the second pyrolyzing process.

关键词： oxygen reduction reaction     Fe-N-C     active sites     Fe addition     second heat treatment    

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Evaluation of the wind energy potential of two south west sites in Nigeria

Olaleye M. AMOO

《能源前沿（英文）》 2012年 第6卷 第3期   页码 237-246 doi: 10.1007/s11708-012-0201-2

摘要： Wind resource assessment is a crucial first step in gauging the potential of a site to produce energy from wind turbines. In this paper, the wind energy potential of Abeokuta (07°03'N, 03°19'E) and Ijebu-Ode (06°47'N, 03°58'E), two south west sites in Nigeria were examined. Twenty years (1990–2010) of monthly mean wind data from a 10 m height were subjected to two-parameter Weibull analysis and other statistical analyses. The results show that the average annual mean wind speed variation for Abeokuta ranges from 2.2 to 5.0 m/s. For Ijebu-Ode, it ranges from 2.0 to 5.0 m/s. The wind power density variation based on the Weibull analysis ranges from 4.26 to 24.51 W/m for Abeokuta and from 8.54 to 76.46 W/m for Ijebu-Ode. Ijebu-Ode was found to be the better of the two sites in terms of annual variation of mean wind speed.

关键词： wind potential     wind speed     wind power density     wind gust     turbulence intensity     Nigeria    

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Microwave-induced high-energy sites and targeted energy transition promising for efficient energy deployment

《能源前沿（英文）》 2022年 第16卷 第6期   页码 931-942 doi: 10.1007/s11708-021-0771-y

摘要： Diverse interactions between microwaves and irradiated media provide a solid foundation for identifying novel organization pathways for energy flow. In this study, a high-energy-site phenomenon and targeted-energy transition mechanism were identified in a particular microwave heating (MH) process. Intense discharges were observed when microwaves were imposed on irregularly sized SiC particles, producing tremendous heat that was 8-fold the amount generated in the discharge-free case. Energy efficiency was thereby greatly improved in the electricity-microwaves-effective heat transition. Meanwhile, the dispersed microwave field energy concentrated in small sites, where local temperatures could reach 2000°C– 4000°C, with the energy density reaching up to 4.0 × 105 W/kg. This can be called a high-energy site phenomenon which could induce further processes or reactions enhancement by coupling effects of heat, light, and plasma. The whole process, including microwave energy concentration and intense site-energy release, shapes a targeted-energy transition mechanism that can be optimized in a controlled manner through morphology design. In particular, the discharge intensity, frequency, and high-energy sites were strengthened through the fabrication of sharp nano/microstructures, conferring twice the energy efficiency of untreated metal wires. The microwave-induced high-energy sites and targeted energy transition provide an important pathway for high-efficiency energy deployment and may lead to promising applications.

关键词： microwave discharge     high-energy sites     targeted-energy transition     morphology design     energy efficiency    

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Scale study of sites and pavilions for World Expo 2010

ZHOU Zhuoyan, CHEN Yi

《结构与土木工程前沿（英文）》 2008年 第2卷 第1期   页码 102-106 doi: 10.1007/s11709-008-0012-z

摘要： The scale of sites and pavilions for World Expo 2010 (Shanghai World Expo) mainly refers to the study of their size including the area and number of exhibition hall needed in each pavilion and site with appropriate waiting area. All the design data of scale studied should reasonably meet the requirements during World Expo 2010 to accommodate large number of people for visiting and waiting to the full.

关键词： pavilion     study     number     appropriate     design    

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On the monolayer dispersion behavior of Co3O4 on HZSM-5 support: designing applicable catalysts for selective catalytic reduction of nitrogen oxides by ammonia

《化学科学与工程前沿（英文）》 2023年 第17卷 第11期   页码 1741-1754 doi: 10.1007/s11705-023-2332-x

摘要： Based on monolayer dispersion theory, Co3O4/ZSM-5 catalysts with different loadings have been prepared for selective catalytic reduction of nitrogen oxides by ammonia. Co3O4 can spontaneously disperse on HZSM-5 support with a monolayer dispersion threshold of 0.061 mmol 100 m–2, equaling to a weight percentage around 4.5%. It has been revealed that the quantities of surface active oxygen (O2–) and acid sites are crucial for the reaction, which can adsorb and activate NOx and NH3 reactants effectively. Below the monolayer dispersion threshold, Co3O4 is finely dispersed as sub-monolayers or monolayers and in an amorphous state, which is favorable to generate the two kinds of active sites, hence promoting the performance of ammonia selective catalytic reduction of nitrogen oxide. However, the formation of crystalline Co3O4 above the capacity is harmful to the reaction performance. 4% Co3O4/ZSM-5, the catalyst close to the monolayer dispersion capacity, possesses the most abundant active O2– species and acidic sites, thereby demonstrating the best reaction performance in all the samples. It is proposed the optimal Co3O4/ZSM-5 catalyst can be prepared by loading the capacity amount of Co3O4 onto HZSM-5 support.

关键词： Co3O4/ZSM-5     NOx-SCR by NH3     monolayer dispersion threshold effect     surface acid sites     surface active O2– anions    

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advanced engineering measures on displacement and stress field of surrounding rock in tunnels crossing active

《结构与土木工程前沿（英文）》 doi: 10.1007/s11709-023-0966-x

摘要： Based on significant improvements in engineering materials, three advanced engineering measures have been proposed—super anchor cables, high-strength concrete anti-fault caverns, and grouting modification using high-strength concrete-to resist fault dislocation in the surrounding rock near tunnels crossing active strike-slip faults. Moreover, single- or multiple-joint advanced engineering measures form the local rock mass-anti-fault (LRAF) method. A numerical method was used to investigate the influence of LRAF methods on the stress and displacement fields of the surrounding rock, and the anti-fault effect was evaluated. Finally, the mechanism of action of the anchor cable was verified using a three-dimensional numerical model. The numerical results indicated that the anchor cable and grouting modification reduced the displacement gradient of the local surrounding rock near the tunnels crossing fault. Furthermore, anchor cable and grouting modifications changed the stress field of the rock mass in the modified area. The tensile stress field of the rock mass in the modified anchor cable area was converted into a compressive stress field. The stress field in the modified grouting area changed from shear stress in the fault slip direction to tensile stress in the axial tunnel direction. The anti-fault cavern resisted the dislocation displacement and reduced the maximum dislocation magnitude, displacement gradient, and shear stress. Among the three advanced engineering measures, the anchor cable was the core of the three advanced engineering measures. An anchor cable, combined with other LRAF measures, can form an artificial safety island at the cross-fault position of the rock mass to protect the tunnel. The research results provide a new supporting idea for the surrounding rock of tunnels crossing active strike-slip faults.

关键词： anti-fault effect     engineering measures     LRAF method     stress and displacement field     tunnel-crossing active faults    

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Advances in Active Suspension Systems for Road Vehicles

Min Yu,Simos Evangelou,Daniele Dini,

《工程（英文）》 doi: 10.1016/j.eng.2023.06.014

摘要： Active suspension systems (ASSs) have been proposed and developed for a few decades, and have now once again become a thriving topic in both academia and industry, due to the high demand for driving comfort and safety and the compatibility of ASSs with vehicle electrification and autonomy. Existing review papers on ASSs mainly cover dynamics modeling and robust control; however, the gap between academic research outcomes and industrial application requirements has not yet been bridged, hindering most ASS research knowledge from being transferred to vehicle companies. This paper comprehensively reviews advances in ASSs for road vehicles, with a focus on hardware structures and control strategies. In particular, state-of-the-art ASSs that have been recently adopted in production cars are discussed in detail, including the representative solutions of Mercedes active body control (ABC) and Audi predictive active suspension; novel concepts that could become alternative candidates are also introduced, including series active variable geometry suspension, and the active wheel-alignment system. ASSs with compact structure, small mass increment, low power consumption, high-frequency response, acceptable economic costs, and high reliability are more likely to be adopted by car manufacturers. In terms of control strategies, the development of future ASSs aims not only to stabilize the chassis attitude and attenuate the chassis vibration, but also to enable ASSs to cooperate with other modules (e.g., steering and braking) and sensors (e.g., cameras) within a car, and even with high-level decision-making (e.g., reference driving speed) in the overall transportation system—strategies that will be compatible with the rapidly developing electric and autonomous vehicles.

关键词： Active suspension     Vehicle dynamics     Robust control     Ride comfort     Chassis attitude    

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标题 作者 时间 类型 操作

Solid-state NMR for metal-containing zeolites: From active sites to reaction mechanism

Xingling Zhao, Jun Xu, Feng Deng

期刊论文

Multifunctional heteroatom zeolites: construction and applications

期刊论文

noble metal nanoparticle size on C–N bond cleavage performance in hydrodenitrogenation: a study of activesites

期刊论文

Insights into carbon-based materials for catalytic dehydrogenation of low-carbon alkanes and ethylbenzene

期刊论文

High-gravity intensified iron-carbon micro-electrolysis for degradation of dinitrotoluene

期刊论文

Effects of preparation methods on the activity of CuO/CeO

Huanhuan Shang, Xiaoman Zhang, Jing Xu, Yifan Han

期刊论文

Microemulsion-mediated hydrothermal synthesis of flower-like MoS

Yuxia Jiang, Donge Wang, Zhendong Pan, Huaijun Ma, Min Li, Jiahe Li, Anda Zheng, Guang Lv, Zhijian Tian

期刊论文

Dual-functional sites for synergistic adsorption of Cr(VI) and Sb(V) by polyaniline-TiO hydrate: Adsorptionbehaviors, sites and mechanisms

期刊论文

Influence of Fe on electrocatalytic activity of iron-nitrogen-doped carbon materials toward oxygen reduction reaction

Lin LI, Cehuang FU, Shuiyun SHEN, Fangling JIANG, Guanghua WEI, Junliang ZHANG

期刊论文

Evaluation of the wind energy potential of two south west sites in Nigeria

Olaleye M. AMOO

期刊论文

Microwave-induced high-energy sites and targeted energy transition promising for efficient energy deployment

期刊论文

Scale study of sites and pavilions for World Expo 2010

ZHOU Zhuoyan, CHEN Yi

期刊论文

On the monolayer dispersion behavior of Co3O4 on HZSM-5 support: designing applicable catalysts for selective catalytic reduction of nitrogen oxides by ammonia

期刊论文

advanced engineering measures on displacement and stress field of surrounding rock in tunnels crossing active

期刊论文

Advances in Active Suspension Systems for Road Vehicles

Min Yu,Simos Evangelou,Daniele Dini,

期刊论文