Search

Selective catalytic reduction of NOx by ammonia (NH3‐SCR) was affected by HCl, which was widely present in industrial flue gas. In this study, the SCR performances over MOx‐WO3/TiO2 (MW/Ti, M=Mn, Ce and V) catalysts after HCl treatment were investigated. It was found that HCl poisoning showed inhibition and promotion in NOx conversion over MnW/Ti and CeW/Ti catalysts, respectively. While the SCR activity over VW/Ti catalyst was hardly affected by HCl. Over MnW/Ti catalyst, the rupture of the Mn−O bond by the strong Mn−Cl binding induced the formation of amorphous MnCl2 species. This Cl‐containing species with Mn in a low oxidation state exhibited poorer redox ability and NO activation, resulting in a decrease in low‐temperature SCR activity. However, instead of directly affecting the CeOx and VOx sites, gaseous HCl reacted with NH3 to form NH4Cl species on the surface of CeW/Ti and VW/Ti catalysts. As a result, the SCR activity of VW/Ti catalyst was scarcely influenced by HCl, taking the unchanged redox ability and NH3 adsorption. With a further accumulation of NH4Cl on CeW/Ti catalyst, the NOx conversion at low temperature was evidently enhanced due to the promotion in NO‐to‐NO2 conversion (Fast‐SCR). [ABSTRACT FROM AUTHOR]

Selective catalytic reduction of nitrogen oxides (NOx) with C3H6 (C3H6‐SCR) was investigated over NiO catalysts supported on different metal‐oxides. A NiAlOx mixed oxide phase was formed over NiO/γ‐Al2O3 catalyst, inducing an immediate interaction between NiOx and AlOx species. Such interaction resulted in a charge transfer from Ni to Al site and the formation of Ni species in high oxidation state. In comparison to other NiO‐loaded catalysts, NiO/γ‐Al2O3 catalyst exhibited the highest NOx conversion at temperature higher than 450 °C, but a poor C3H6 oxidation activity due to the decreased nucleophilicity for surface oxygen species. By temperature‐programed NO oxidation, it is indicated that nitrate species were rapidly formed and stably maintained at high temperature over NiO/γ‐Al2O3 catalyst. In situ transient reactions further verified the Langmuir–Hinshelwood mechanism for C3H6‐SCR, where both gaseous NO and C3H6 were adsorbed and activated on catalyst surface and reacted to generate N2. Due to the strong metal‐support interaction over NiO/γ‐Al2O3 catalyst, both nitrate and CxHyOz intermediates were well preserved to attain high C3H6‐SCR activity. [ABSTRACT FROM AUTHOR]

Nitrate, as an important nitrogen source, plays a crucial role in the fields of energy, chemicals, and the environment. Electrocatalytic nitrogen conversion, powered by renewable energy sources, is a viable and promising strategy for the synthesis and conversion of nitrate. In this work, electrocatalytic synthesis and conversion of nitrates associated with five reactions: ammonia oxidation reaction (NH3OR), nitrogen oxidation reaction (N2OR), NO oxidation reaction (NOOR), nitrate reduction reaction (NO3RR), and the electrochemical C-N coupling of CO2 and NO3− (C–N coupling) were reviewed. At present, it is found that most of these reaction processes still suffer from low Faradaic efficiency and product yield. The underlying mechanisms, key steps, and rational catalyst design for these nitrogen electrochemical reactions were summarized. This review aims to provide insights into the fundamentals in the relevant reactions, the development of efficient catalysts, and the advances in the progress of artificial nitrogen cycling processes.Graphical Abstract: Nitrate, as an important nitrogen source, plays a crucial role in the fields of energy, chemicals, and the environment. Electrocatalytic nitrogen conversion, powered by renewable energy sources, is a viable and promising strategy for the synthesis and conversion of nitrate. In this work, electrocatalytic synthesis and conversion of nitrates associated with five reactions: ammonia oxidation reaction (NH3OR), nitrogen oxidation reaction (N2OR), NO oxidation reaction (NOOR), nitrate reduction reaction (NO3RR), and the electrochemical C-N coupling of CO2 and NO3− (C–N coupling) were reviewed. At present, it is found that most of these reaction processes still suffer from low Faradaic efficiency and product yield. The underlying mechanisms, key steps, and rational catalyst design for these nitrogen electrochemical reactions were summarized. This review aims to provide insights into the fundamentals in the relevant reactions, the development of efficient catalysts, and the advances in the progress of artificial nitrogen cycling processes. [ABSTRACT FROM AUTHOR]

In this work, Co 3 O 4 , Co x Cu y and CuO metal oxides catalysts were synthesized by coprecipitation method and tested in catalytic oxidation of Hg0 and NO. The Co3Cu1 catalyst exhibited nearly 100% Hg0 oxidation efficiency at 100–400 ℃ and 84% NO oxidation efficiency at 250 ℃. Respectively, 1155.2 μg g−1 Hg0 adsorption capacity and 92.9 μmol g−1 NO x adsorption capacity over Co3Cu1 catalyst were measured by Hg0-TPD and NO x -TPD. The largest BET specific surface area of Co3Cu1 catalyst was obtained, reaching 26.2 m2 g−1. And H 2 -TPR demonstrated that the first reduction peak temperature (192 ℃) of Co3Cu1 catalyst was much lower than that of other catalysts. O 2 -TPD illustrated that the oxygen storage capacity and oxygen mobility ability of Co3Cu1 catalyst were higher than that of other catalysts. These results were consistent with the results of Hg0 and NO oxidation activity tests. In addition, in-situ DRIFTS spectra of NO adsorption indicated that the band at 1390 cm−1 over Co3Cu1 catalyst disappeared after the pretreatment of Hg0. And the transient experiments of Hg0 adsorption suggested that Hg0 could also be extruded from the surface of Co3Cu1 catalyst after the introduction of NO. It was speculated that there might be competitive adsorption between Hg0 and NO over Co3Cu1 catalyst. Finally, the XPS characterization demonstrated that the O α and the redox cycle of Co3+ + Cu+ ↔ Co2+ + Cu2+ were involved in Hg0-NO simultaneous oxidation. The Co3Cu1 catalyst was an excellent candidate for Hg0-NO oxidation reaction. [Display omitted] • The Co3Cu1 catalyst was highly active for simultaneous catalytic oxidation of Hg0 and NO. • The excellent Hg0 and NO adsorption capacity, redox property and oxygen mobility ability were observed over Co3Cu1 catalyst. • There might be competitive adsorption between Hg0 and NO over Co3Cu1 catalyst. • O α and the redox cycles of Co3+ + Cu+ ↔ Co2+ + Cu2+ were involved in Hg0-NO simultaneous oxidation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hierarchically devised NiFeO x H y catalyst showed high OER activity under alkaline condition. • NiFeO x H y /Ni heterostructure was in-situ formed via a surface reconstruction process. • Charge transfer at the catalyst-electrolyte interface was improved with Fe incorporation into Ni (oxy)hydroxide. • Fe species located at the outer surface of NiOOH structure served as the OER active site. Nickel iron (oxy)hydroxide (NiFeO x H y) is among the most active electrocatalysts for oxygen evolution reaction (OER) in the alkaline media. Development of new design strategy for NiFeO x H y electrode with respect to intrinsic activity and number of active species is highly attractive. Here we report a hierarchical fabrication for NiFeO x H y electrode towards efficient oxygen evolution. Three-dimensional mesoporous NiO was initially prepared and reduced to a polycrystalline Ni metal framework. Despite the poor OER activity for Ni-based catalyst, the incorporation of surface Fe species induced a notably high current density for the oxygen evolution. The results indicated that the Fe species, located at outer surface region, played a key role as the OER active sites. It is also found that the surface of metallic Ni was reconstructed to (oxy)hydroxide phase with ease compared to NiO. As a result, a heterostructure composed of an OER-active NiFe (oxy)hydroxide shell and an electron-conductive Ni core was formed. In this fabricated NiFeO x H y /Ni catalyst, the promoted intrinsic activity, number of active sites and charge-transfer ability all taken into account contribute to an efficient OER process. [ABSTRACT FROM AUTHOR]

We report a FeW mixed composite for oxygen evolution reaction with a low overpotential and a long-term stability. A structural transformation of FeW oxide occurs during the OER process. Theoretical calculation indicates that FeOx is the OER-active site and the neighboring WOx improves the *OH to *O conversion on the Fe site. [ABSTRACT FROM AUTHOR]

A series of Cd-doped NiO catalysts were prepared and tested in the N 2 O catalytic decomposition reaction. In comparison with NiO, it was found that the Cd 0.04 Ni catalyst showed higher N 2 O decomposition activity in the temperature range of 300–450 °C with or without O 2 , and lower activation energy (77.8 kJ mol−1). The incorporation of Cd into the NiO lattice was verified by X-ray diffraction (XRD) patterns and Raman spectra. This led to the distortion of the original NiO structure and weakened the Ni-O bond. X-ray photoelectron spectroscopy (XPS) results showed that compared with NiO and CdO, Cd 0.04 Ni possessed higher Ni2+ and Cd(n+1)+ contents, which might have been induced by the electron transfer behavior between CdO and NiO. A possible mechanism for active site regeneration and O 2 desorption over Cd 0.04 Ni was proposed. The Cd 0.04 Ni catalyst also exhibited good resistance to NO and O 2. [Display omitted] • Catalytic decomposition of N 2 O over NiO was improved by Cd-doping. • Incorporated Cd led to the lattice distortion of NiO and weakened the Ni-O bonds. • Cd 0.04 Ni exhibited unaffected N 2 O decomposition activity with and without O 2. • A possible electron transfer mechanism on Cd 0.04 Ni was proposed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Vanadia species suppress the reducibility and defect sites of ceria. [•] Polymeric VO x , ceria provide Lewis and CeVO4 provide Brønsted acid sites. [•] Polymeric VO x low energy barriers and CeVO4 increase rate constant. [•] The reaction mechanism depends on the temperature. [ABSTRACT FROM AUTHOR]

Abstract: Air-lift artificial upwelling was simulated through a simplified computational fluid dynamics (CFD) model of two-phase flow in an upward pipe. This model is based on the momentum transfer between the two phases. An algebraic turbulence model was employed to enclose the equations. The volumetric flow rates of the liquid and the gas phases, the void fraction distribution, and the pressure and velocity profiles along the axial coordinate were calculated in the stationary state. Numerical tests were conducted to verify the model. The good agreement obtained between the computational results and the field test measurements with cross-shaped air injectors demonstrates the capability of this model for dispersed bubbly flow conditions. Comparisons with the analytical theory were also made. The results indicated that the proposed engineering-oriented model is efficient for the optimization of the system. [Copyright &y& Elsevier]

Highlights: [•] Mn, Co, Ni and Zn are doped into the structure of iron spinel oxides. [•] Surface acidity and redox properties are related to iron spinel structures. [•] Competition of NH3-CR and NH3-CO exists over metal-doped iron spinel catalysts. [•] SCR performance is affected by the redox cycle of Fe3+/Fe2+ in octahedral sites. [Copyright &y& Elsevier]

Highlights: [•] Presence of bulk WO3 on titania surface leads to deficiency of Brønsted acid sites. [•] Two-dimension VO x has a tendency to anchor onto titania surface in vicinity of WO x . [•] WO x shows compressing effects on monolayer VO x species at high vanadium loadings. [•] NH3-SCR performance is mainly dependent on vanadium contents of V W/TiO2 catalysts. [ABSTRACT FROM AUTHOR]

Abstract: (Fe3−x Mn x )1−δ O4 was synthesized using a co-precipitation method and then developed as a catalyst for the low temperature selective catalytic reduction (SCR) of NO with NH3. The SCR activity of (Fe3−x Mn x )1−δ O4 was clearly enhanced with the increase of Mn content. The results of in situ DRIFTS study demonstrated that both the Eley–Rideal mechanism (i.e. reaction of activated ammonia with gaseous NO) and the Langmuir–Hinshelwood mechanism (i.e. reaction of adsorbed ammonia species with adsorbed NO x species) might happen during the SCR reaction over (Fe3−x Mn x )1−δ O4. According to the kinetic analysis, the respective contribution of the Langmuir–Hinshelwood mechanism and the Eley–Rideal mechanism on the SCR reaction was studied. Only the adsorption of NO+O2 on (Fe2.8Mn0.2)1−δ O4 was promoted, so the Langmuir–Hinshelwood mechanism predominated over NO conversion on (Fe2.8Mn0.2)1−δ O4 especially at lower temperatures. Both the adsorption of NO+O2 and the adsorption of NH3 on (Fe2.5Mn0.5)1−δ O4 were obviously promoted, so NO conversion on (Fe2.5Mn0.5)1−δ O4 mainly followed the Eley–Rideal mechanism especially at higher temperatures. Both the nitrate route and the over-oxidization of adsorbed ammonia species contributed to the formation of N2O on (Fe2.8Mn0.2)1−δ O4 above 140°C. However, the formation of N2O on (Fe2.5Mn0.5)1−δ O4 mainly resulted from the over-oxidization of adsorbed ammonia species. Although the activity of (Fe2.5Mn0.5)1−δ O4 was suppressed in the presence of H2O and SO2, the deactivated catalyst can be regenerated after the water washing. [Copyright &y& Elsevier]

Mechanism of hydrodynamic aggregation of swimmers is an intriguing problem, which is usually studied by the immersed boundary (IB) method. In this paper, a loosely coupled partitioned algorithm is used to simulate this fluid-structure interaction (FSI) problem. Specifically, flow field is simulated by finite volume method, and structure field is approximated by solving the momentum equation and bending vibration equation of Euler-Bernoulli beam. First of all, this algorithm is validated through simulating collective behavior of two actively moving two-dimensional (2D) flexible plates in tandem configuration driven by the harmonic plunging motions of their leading edges with identical frequency and amplitude. Then, the hydrodynamic aggregations of multiple (two or three) 2D flexible plates in side-by-side configuration are studied. It is found that two different stable configurations (alternate-leading mode, AL and staggered-following mode, SF) are formed spontaneously in two parallel flexible plates, and are determined by the lateral spacing between them. In three parallel-plates scenario, the middle plate follows behind in SF mode, while the other two plates present AL and SF modes with different lateral spacings accordingly. Besides, the flow details in different configurations are illustrated and the corresponding propulsive properties (velocity, input power and efficiency) of plates are discussed. • Loosely coupled partitioned algorithm is adopted for hydrodynamic schooling problem. • Hydrodynamic aggregation of multiple 2D self-propelled flexible plates is simulated. • Flow details are discussed to explain mechanism by which collective modes are formed. [ABSTRACT FROM AUTHOR]

Wave resonance by forced motions of two bodies in a steady current is investigated in this paper. The work is based on second order theory of potential flow and the simulation is through a higher order finite element method with 12-node elements in time domain. Boundary conditions are imposed on mean positions of all boundaries. The i -th (i = 1,2) order potentials in the fluid domain at each time step are obtained by solving the finite element system and the spatial derivatives of the potential are calculated by differencing the shape functions directly. Numerical cases are given for two rectangular cylinders undergoing in specified oscillations in a steady current. The first and second order resonances have been captured at their resonant frequencies at different current speeds, which does not seem to have been studied yet. The numerical result shows that the current speed has important influence on the wave and force at both first and second order resonances. • A higher order finite element method has been employed to analyze wave-current-body interaction. • Both linear and resultant waves & forces have been affected by the current including amplitude, phase or nonlinearity. • Larger Froude number generally causes linear or second order wave and force to be smaller at its resonant frequency. • Second order wave and force increase as Froude number increases at in vertical motion and at in horizontal motion [ABSTRACT FROM AUTHOR]

Efficient internal mixing stands as a pivotal requirement for droplet-based micro-reactors/micro-mixers facilitated by microfluidic systems. Among the various methods for their production, capillary-generated droplets emerge as a notable approach. Understanding the role of coaxiality within coflow microfluidic devices in influencing internal mixing remains a crucial aspect for optimizing these systems. Coaxiality within inserted cylindrical capillaries significantly affects mixing efficiency according to our experimental observations. Through numerical simulations, the intricate mixing dynamics of reagents inside droplet generated via a coflow capillary microfluidic system has been investigated. We demonstrate that coaxiality profoundly impacts the initial distribution of disperse phases within droplets, shaping subsequent internal mixing dynamics. Contrary to previous assumptions, our findings highlight the substantial impact of marginal deviations in coaxiality, around 20%, on optimizing mixing efficiency. This challenges prior beliefs and emphasizes the nuanced role of coaxiality in microfluidic systems. These insights advance our understanding of coaxiality's critical influence on enhancing mixing efficiency within coflow microfluidic devices, paving the way for improved design strategies and applications in diverse scientific fields. [ABSTRACT FROM AUTHOR]

Hydrodynamic motion of rigid body in narrow space is a common phenomenon in nature and ocean engineering application. In this paper, a new simulation model based on Fluent is proposed to solve this kind of fluid-structure interaction problem in which added-mass effect is strong. In this new model, hydrodynamic force is decomposed, and a new six-degree-of-freedom rigid-body motion equation is formed with added mass force being added to both sides of the motion equation used by 6DOF solver in Fluent. First of all, numerical results of free-floating rigid body in open domain by 6DOF solver and experimental data of free-falling sphere in still water are presented for the validation of this new simulation model. Then, the scope of this model is studied. It is found that 6DOF solver in Fluent cannot solve the hydrodynamic motion of rigid body if added-mass effect is strong, while this new model is apt for this kind of problem and has good convergent characteristics. Finally, hydrodynamic behavior of rigid body in a changing domain is simulated by the new model. Acceleration and spatial displacement curves are obtained, and details of flow at some key moments are presented and analyzed. • A new simulation model improves Fluent in solving hydrodynamic behavior of rigid body with strong added-mass effect. • The scope of the new simulation model is introduced by comparative analyses with 6DOF solver in Fluent. • Added mass of rigid body in the changing domain is estimated. • The hydrodynamic motion of rigid body in the changing domain is analyzed. [ABSTRACT FROM AUTHOR]

Considering the radius similarity of Al3+ (0.50 Å) and Ga3+ (0.62 Å), Al−Co and Ga−Co layered double hydroxides (LDH) was prepared as precursor to improve the synergetic interaction of the transition metals. The Al−Co and Ga−Co spinel catalysts were obtained by the following calcination for the toluene oxidation. The Ga−Co (Ea=79.5 kJ mol−1) showed higher activity than the Al−Co (Ea=95.4 kJ mol−1), and it exhibited excellent stability and resistance to carbon deposition during a 50 h reaction period at 300 °C. Characterization results indicated that the improved activity of Ga−Co spinel could be attributed to the higher reducibility (H2‐TPR), more surface Co3+ and adsorbed oxygen in quantity (XPS) and adsorbed toluene (Toluene‐TPD) than Al−Co spinel. Compared with traditional Ga−Co binary catalyst, the spinel structure possessed more B‐sites cations outermost of the surface and surface oxygen vacancies for the toluene adsorption and ring‐open reaction. It′s all about how big you are: Considering the radius similarity of Al3+ (0.50 Å) and Ga3+ (0.62 Å), Al−Co and Ga−Co LDH were prepared as precursor to improve the synergetic interaction of the transition metals. The Al−Co and Ga−Co spinel were obtained by the following calcination for the toluene oxidation. Characterization results indicated that the improved activity of Ga−Co spinel could be attributed to the higher reducibility, more surface Co3+ and adsorbed oxygen in quantity and adsorbed toluene than Al−Co spinel." [ABSTRACT FROM AUTHOR]

Chlorine species, widely presented in industrial flue gas such as the waste incineration plants, can poison the catalysts and affect the selective catalytic reduction (SCR) performance. In this work, effects of Cl on the SCR performance of V2O5–WO3/TiO2 (VW/Ti) catalysts were investigated by NH4Cl deposition. The results showed that the NOx conversion efficiency at low reaction temperature (< 300 °C) decreased with the loading of NH4Cl after calcination. It was found that instead of causing the chlorination of VW/Ti catalyst the NH4Cl decomposed into volatile Cl species due to the weak V–Cl bonding. Such decomposition reduced significantly the surface non-lattice oxygen species to inhibit NO adsorption and activation, but hardly affected the redox ability and acidity of VW/Ti catalyst. Time–resolved in situ DRIFTs results indicated that NH3 activation and the SCR process predominated by Eley–Rideal mechanism were not influenced with NH4Cl impregnation, while the SCR at low temperature following a Langmuir–Hinshelwood path was limited by the decreased and weaker binding sites for NO activation. [ABSTRACT FROM AUTHOR]

Abstract: Copper‐exchanged H‐SAPO‐47 zeolites were synthesized by an aqueous solution ion exchange method and applied in the selective catalytic reduction of NO with NH3 (SCR). The microporous chabazite (CHA) structure of the catalysts was characterized and confirmed using synchrotron X‐ray diffraction and nitrogen adsorption–desorption experiments. The synthesized Cux‐SAPO‐47 catalysts exhibited excellent SCR activity and nearly 100 % N2 selectivity in a wide temperature range. The Cu0.1‐SAPO‐47 sample exhibited higher activity than the other samples below 250 °C. The weak Lewis acid sites originating from the introduction of Cu2+ were more active than the Brønsted acid sites of the zeolites framework at low temperature. Two types of isolated Cu2+ species with different coordination surroundings were found, namely, Cu2+ cations bonded with the six‐membered rings and those bonded in the CHA cages. The former species exhibited good stability and activity at high temperature, whereas the latter ones were more active at low temperature. The Cu0.1‐SAPO‐47 catalyst provided a considerable amount of isolated Cu2+ bonded in the CHA cages. These results indicated that active Lewis acid sites and isolated Cu2+ species are responsible for their excellent SCR activity. [ABSTRACT FROM AUTHOR]

A direct analysis approach is adopted to handle ejection problem of the independent escape capsule from submarine in still water. Motion characteristics of the capsule and the gap between the capsule and submarine for successful escape are obtained. Ejection process is mainly divided into the translational and coupling motion phases according to forces (including the hydrostatic and hydrodynamic) on the capsule and its corresponding motions. The capsule's coupling motion is solved by using the concept of contact pairs in ABAQUS, and the hydrodynamic force on the capsule is calculated with the commercial computational fluid dynamics (CFD) package Fluent and introduced into numerical model through ABAQUS/AQUA module. The numerical simulation shows that the gap is much smaller than the results obtained by the assumption that the capsule rotates around a fixed supported edge, which indicates that coupling motion is critical to the successful escape of the capsule. The hydrodynamic force prolongs the escaping time and affects the value of the gap and the motion characteristics in both translational and coupling motion phases. In addition, time and the gap are chosen as standard, under which several design parameters are investigated in order to provide suggestions for optimal design of the capsule. [ABSTRACT FROM AUTHOR]

The expansion of offshore wind farms into deeper waters presents economic challenges due to the rising costs of operation and maintenance. To address this issue, the development of targeted opportunistic maintenance strategies for offshore wind farms is crucial. Existing strategies often overlook the interconnections between maintenance activities across wind farms, focusing solely on individual wind farms. However, joint maintenance of wind farms has been acknowledged as an effective approach to reducing maintenance costs at the operational level. This paper introduces an opportunistic maintenance strategy that considers the joint maintenance of two wind farms and establishes reliability thresholds to guide maintenance decisions. Furthermore, the developed maintenance model is improved by incorporating more realistic vessel models and considering various types of maintenance costs. Conclusions can be drawn from a comprehensive analysis of optimization results across multiple scenarios involving maintenance costs, wind farm parameters, and uncertainties. The comparative analysis demonstrates that, in the farthest offshore distance case, the proposed strategy exhibits a reduction in maintenance costs of 15.67% and 4.87% when compared to two traditional strategies, respectively. This effect is further amplified in scenarios where offshore wind farms are located in close proximity to each other and encounter substantial uncertainties. • Developing a novel joint maintenance strategy for two offshore wind farms. • New decision-making structure is established using three decision thresholds. • The strategy is evaluated considering cost, wind farm parameters, and uncertainty. • The proposed strategy saves 15.67% and 4.87% in LCC versus traditional strategies. [ABSTRACT FROM AUTHOR]

[Display omitted] • AgCo-g-CN possessed enhanced catalytic decomposition of N 2 O under O 2 compared with Co 3 O 4. • Metallic Ag and higher content of Co2+ were found on AgCo-g-CN by adding g-CN. • Higher contents of Co2+ could play a beneficial role in the enhancement of N 2 O catalytic decomposition. • Metallic Ag improved the O 2 desorption capacity of AgCo-g-CN. Nitrous oxide (N 2 O) has gained increasing attention as an important greenhouse gas and stratospheric-ozone-depleting substance. Catalytic decomposition is considered an effective method for N 2 O abatement. Herein, AgCo-g-CN catalyst prepared by impregnation synthetic procedure was tested for N 2 O catalytic decomposition in the presence of O 2. The catalytic results indicated that full N 2 O conversion was obtained at 400 °C. The enhancement of catalytic activity was mainly derived from the addition of g-CN compared with bare Co 3 O 4 and AgCo. Metallic Ag and higher content of Co2+ were found over the AgCo-g-CN catalyst. By XPS and kinetic analysis, the catalytic performance was correlated with the content of Co2+, the facilitation of Co2+ contents could play a beneficial role in the enhancement of the AgCo-g-CN catalysts. Besides, HRTEM, XPS, and TPx revealed that metallic Ag improved the O 2 desorption capacity of AgCo-g-CN, which is important during the N 2 O catalytic decomposition. By lowering the valence of Co and Ag species, g-CN enhanced the catalytic performance of N 2 O. This study might provide a reference for designing N 2 O decomposition catalysts and potential applications for g-CN in heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Abstract: A series of non-stoichiometric Fe–Ti spinel (Fe3−x Ti x )1−δ O4 were synthesized using a co-precipitation method and then developed as environmental-friendly and low cost catalysts for the selective catalytic reduction (SCR) of NO with NH3. As Ti was incorporated into γ-Fe2O3, the SCR reaction over (Fe3−x Ti x )1−δ O4 through the Langmuir–Hinshelwood mechanism was restrained. Therefore, the SCR activity of (Fe3−x Ti x )1−δ O4 (x ≠0) was less than that of γ-Fe2O3 at 150–250°C. However, the SCR reaction over (Fe3−x Ti x )1−δ O4 through the Eley–Rideal mechanism was promoted due to the incorporation of Ti. The SCR activity of (Fe3−x Ti x )1−δ O4 (x ≠0) was mainly related to the oxidative ability of Fe3+ cation on the surface, the concentration of NH3 adsorbed on the surface and the concentration of reducible Fe3+ cation on the surface. Although the oxidative ability of Fe3+ cation on the surface decreased due to the incorporation of Ti into γ-Fe2O3, the concentration of NH3 adsorbed on the surface and the concentration of reducible Fe3+ cation on the surface both increased. As a result, (Fe2Ti)0.8O4 showed excellent activity, selectivity, and H2O/SO2 durability for the SCR reaction at 300–400°C. [Copyright &y& Elsevier]

Loosely-coupled scheme is extensively used to simulate fluid-structure interaction (FSI) problems due to its efficiency. However, it meets the numerical difficulty of instability in the strong added-mass scenario. In this paper, a loosely-coupled scheme is proposed for solving the flow-induced flapping problem of two-dimensional (2D) flexible plate with strong added-mass effect. Specifically, finite volume method is used to simulate the flow field and mode superposition method is applied to calculate the structure field. In order to avoid the added-mass induced numerical instability, governing equation of the flexible plate is modified with added mass being added to its both sides. First of all, this proposed scheme is validated through simulating hydrodynamic response of a single cantilever flexible plate in uniform flows. Then, to study the stability of the proposed scheme, the flow-induced oscillations of a cantilever flexible plate with various low mass ratios and strong added-mass effects are studied. The critical stability boundary of the flapping dynamics of a cantilever flexible plate is also presented. Finally, the proposed scheme is applied to simulate the hydrodynamic behaviors of two parallel plates in uniform flows. Two distinct flapping dynamics models (in-phase and out-of-phase oscillations) are obtained and their corresponding flow details are illustrated. • A loosely-coupled scheme is proposed for FSI problem with strong added-mass effect. • Flow-induced motion of a 2D flexible plate with various low mass ratios is discussed. • Two 2D flexible plates with different lateral spacings in uniform flows are studied. [ABSTRACT FROM AUTHOR]

The safe and efficient operation of submarine high-voltage cables depends on their thermal performance. Based on the electromagnetic heat coupling and heat transfer theory, the cables' heat dissipation in multi-layered sediments is simulated using FEM. The proposed models are validated by comparing with the results of IEC 60287 and illustrated the limitation of IEC 60287 which ignores convective heat transfer. Further, the width of the cable embedding layers greater than 9 m can promote heat dissipation when the permeability of the cable embedding layer is relatively high, but the effect of depth is less pronounced. Also, the cable temperatures increase with the decrease of sediments thermal conductivity and increase of the buried depth when permeability is below 10−12 m2. The temperature decreases as the permeability increases, the range of decay is between 10% and 55% when the permeability reaches 10−9 m2. The heat dissipation is great when the permeability is greater than 10−11 m2. When the characteristic of the cable embedding layers is different from its upper and lower layers, the high permeability of the upper layers reduces the cable conductor temperature more efficiently than the lower layers. The findings give some reference in improving the transmission efficiency of cables. • The influence of multi-layered sediment characteristics on the thermal performance of submarine cables is analyzed. • The high permeability could help dissipate heat efficiently, the decay of conductor temperature can be up to 40%. • This paper illustrated the limitation of present methods in IEC 60287 which ignores the effect of convective heat transfer. • The submarine cables buried in sands or coarser sediments are better, and the buried depth is as small as possible. • The width of the cable embedding layers greater than 9 m can effectively promote the convective heat dissipation. [ABSTRACT FROM AUTHOR]

Lignite is widelyused as the fuel for coal-fired power plants, and its flue gas temperatureis about 50–100 °C higher than others. V2O5–WO3/TiO2is extremely restrictedin the selective catalytic reduction (SCR) of NO from the coal-firedpower plants burning lignite due to the drop of NOxconversion, low N2selectivity, and volatilityof vanadium pentoxide at high temperatures. Therefore, a more environmental-friendlySCR catalyst with excellent SCR activity and better N2selectivityat 350–450 °C should be developed for this application.In this work, sulfated Fe–Ti spinel catalyst was developedfor the SCR of NO from the coal-fired power plants burning lignite.The drop of NOxconversion at high temperatureswas mainly related to the simultaneous occurrence of the catalyticoxidization of NH3to NO during the SCR reaction. Ti wasincorporated into γ-Fe2O3to decease theoxidization ability of Fe3+on the surface, and the sitesfor −NH2adsorption and the active components for−NH2oxidization were separated after the sulfationto decrease the probability of the collision between −NH2adsorbed and Fe3+on the surface. They both inhibitedthe catalytic oxidization of NH3to NO over γ-Fe2O3. However, the SCR reaction over γ-Fe2O3was simultaneously restrained after the incorporationTi and the sulfation. Therefore, NOxconversionover γ-Fe2O3at high temperatures dependedon the ratio of NH3conversion through the catalytic oxidizationof NH3to NO to that through the SCR reaction. This ratiodecreased after the incorporation of Ti, and it further decreasedafter the sulfation, resulting in an obvious promotion of NOxconversion at high temperatures. Therefore, sulfatedFe–Ti spinel showed excellent SCR activity, N2selectivity,and H2O+SO2durability at 300–450 °C,which was suitable for the application in the coal-fired power plantsburning lignite. [ABSTRACT FROM AUTHOR]

The subsea tree acts as an important role in underwater production system. During its installation procedure, hydrodynamic loads significantly affect its dynamic performance. Hence, the drag coefficient of the subsea tree is addressed in detail in the paper by experiment and numerical simulation. Numerical simulation was carried out with finite difference method to get the drag force and drag coefficient. A new experimental method was proposed to conduct an array of model experiments for drag coefficient of subsea tree. The numerical results in drag coefficient were slightly different with experimental results, that was to say, the accuracy and reliability of the experimental data were proved. The drag coefficient is 0.432 in x-direction, 0.479 in y-direction and 0.446 in z-direction, which provide the accurate fundamental hydrodynamic data for underwater production system installation. • Hydrodynamic coefficient plays an important role in hydrodynamic and motion response. • Towing test in the tank can obtain the hydrodynamic data of subsea equipment. • Drag force has a gradual rise with the increase of flow velocity. • Drag coefficient is slightly differ with different flow velocity. [ABSTRACT FROM AUTHOR]

The independent escape capsule, an important facility of submarine search and rescue (SAR) system, gains extensive attention recently. However, researches on its ejection performance are rare, not to mention the studies of structural design in terms of this theme. In this paper, the vibration-absorptive materials clinging to the inner wall of its housing are used, and hydrodynamic responses of the capsule at a particular orientation in steady, uniform currents under various design parameters such as rigidity, friction coefficient and thickness are simulated. In order to study this interdisciplinary problem of fluid-structure interaction and multi-body dynamics, a simulation model (loosely coupled scheme) based on Fluent (version 13.0.1) is adopted with complement of the contact force between the capsule and the vibration-absorptive materials. Specifically, Fluent is used to assess the hydrodynamic force acting on the capsule, distributed force mode and material mechanics method are adopted to obtain the contact force, and then fourth-order Runge-Kutta method is implemented to calculate the motion equations of the capsule. Discussion of motion characteristics of the capsule indicates that this vibration-absorptive design helps the ejection of the capsule. Mechanism of vibration-absorptive design is discussed and some design suggestions are given. • Vibration-absorptive design is proposed to improve the ejection performance of capsule. • Contact behavior between the capsule and vibration-absorptive materials is described. • Ejection process of the capsule using vibration-absorptive design is simulated. • Effects of design parameters of the vibration-absorptive materials on the ejection performance are discussed. [ABSTRACT FROM AUTHOR]

Hydrodynamic behavior of an independent escape capsule from a disabled submarine is a complex six-degrees-of-freedom motion, in which added-mass effect is strong and variable constraint conditions happen. In this paper, loosely (or weakly) coupled scheme is adopted to solve this fluid-structure interaction problem. Flow field is simulated by Fluent (version 13.0.1) and motion equations are solved by the fourth-order Runge-Kutta method separately. Unstructured dynamic mesh technology is used to trace the trajectory of capsule. Hydrodynamic force is decomposed into resistance and added mass force, and new motion equations are derived in order to handle the huge added mass. The surfaces of capsule and its chamber come into contact randomly. The variable constraint conditions are analyzed and their corresponding kinematical equations are introduced. This loosely coupled scheme is applied to study the hydrodynamic behavior of a two-dimensional capsule from a narrow space into an open domain under different ocean currents. Hydrodynamic force, motion characteristics and trajectory are obtained. The simulation indicates that the velocity and direction of flow strongly affect the motion of capsule, and the contact force leads to the jamming problem of capsule during its ejection process. • A loosely coupled scheme is proposed for fluid-structure interaction problem under variable constraint conditions. • Fluid-structure interaction problem with strong added-mass effect is studied. • Added mass of rigid body in finite fluid domain is calculated. • Motion characteristics and trajectory of an ejected capsule inside a chamber are analyzed. • The effect of ocean currents on ejection performance of capsule is discussed. [ABSTRACT FROM AUTHOR]

Different Fe/SAPO-34 catalysts were prepared by a solid-state ion exchange method and used to catalyze N 2 O decomposition. The catalytic performance of these catalysts was strongly related to their Fe precursors. Relevant characterization was carried out using X-ray diffraction, N 2 adsorption-desorption, UV–vis spectroscopy, electron paramagnetic resonance, and H 2 temperature-programmed reduction. The data indicated that the nature and distribution of Fe species in the catalysts changed with different Fe precursors used. Furthermore, monomeric Fe3+ ions and small oligomeric Fe x O y were the active Fe species for the Fe/SAPO-34 catalysts. Finally, it is reasonable to speculate that such a Fe source effect could be explored for other reactions. Unlabelled Image • N 2 O decomposition over Fe/SAPO-34 using different Fe precursors was first investigated. • The distribution of Fe species in the catalysts changed with different Fe precursors used. • Monomeric Fe3+ ions and small oligomeric Fe x O y were the active Fe species. [ABSTRACT FROM AUTHOR]

Pt-Au/TiO 2 -CeO 2 catalyst for the co-oxidation of HCHO, H 2 and CO at 25 °C. • The Pt-Au/TiO 2 -CeO 2 catalyst exhibited high catalytic activity for the co-oxidation of HCHO, H 2 and CO at room temperature. • CO restrained the oxidation of HCHO and H2 due to the CO self-poisoning effect. • H2 promoted the oxidation of HCHO and CO because of the generation of OOH and OH active species. • The deactivation was due to chemical state changes of active site and the accumulation of carbonates-like species. The deactivation origins of the Pt-Au/TiO 2 -CeO 2 catalyst for co-oxidation of formaldehyde (HCHO), hydrogen (H 2) and carbon monoxide (CO) at room temperature were studied by means of XRD, BET, H 2 -TPR, O 2 -TPD, XPS and in-situ DRIFTS. The results suggested that the catalyst deactivation was mainly caused by the reduction of Au+ species, the decrease of Ce3+ species and interaction weakness between active components and support. Moreover, during the co-oxidation process, CO showed a negative influence on the oxidation of HCHO and H 2 due to the CO self-poisoning effect, whereas H 2 promoted the oxidation of HCHO and CO because of the generation of OOH and OH active intermediates from the H 2 oxidation. Meanwhile, the accumulations of carbonate-like species as well as the production of H 2 O on the deactivated catalyst were also observed, accounting for the complete catalyst deactivation. [ABSTRACT FROM AUTHOR]