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Ab Intio Calculations on Reaction Process of Piperazine Absorbing CO 2

Energy Procedia 2017年 114卷 2121-2127页

作者： Tingting Zhang Yunsong Yu Guoxiong Wang Zaoxiao Zhang School of Chemical Engineering and Technology Xi’an Jiaotong University No.28 Xianning West Road Xi’an 710049 P.R. China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University No.28 Xianning West Road Xi’an 710049 P.R. China School of Chemical Engineering University of Queensland Brisbane Qld. 4072 Australia

The increasing amount of CO 2 emitted to the atmosphere has a deep impact on the environment. It is urgent to take effective measures to reduce CO 2 emissions from its intensive emission source. Chemical absorption is an effective way to cover the large reduction of CO 2 , and piperazine (PZ) is one of the amines that have good performance on CO 2 capture. To make a deep understanding of the chemical mechanism of PZ absorbing CO 2 , computational studies on PZ chemically absorbing CO 2 are discussed in this work using Density functional theory (DFT). Possible reaction pathways of PZ absorbing CO 2 are analyzed. Due to the special chemical structure of PZ, the reaction processes can be divided into two parts, the process of (PZ+CO 2 )+PZ and (PZ+2CO 2 )+PZ. To make a good understanding of the reaction process, a comparison of that between PZ and MEA are discussed. The results show that PZ has lower forward and backward energy barriers than MEA in the zwitterion formation, but in the intermolecular hydrogen transfer process, PZ has higher forward and backward barriers than MEA. For the reaction process of PZ+2CO 2 , it can be stated as a two-step zwitterion formation with two transition states. For the following intermolecular hydrogen transfer of PZ(COO) 2 +PZ, the atom movements are similar to that of (PZCOO+PZ). All the discussions provide theoretical information of PZ chemical absorbing CO 2 .

关键词： CO 2 absorption Piperazine Reaction mechanism DFT Energy barriers

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Aqueous Synthesis of Ultrathin Platinum/Non‐Noble Metal Alloy Nanowires for Enhanced Hydrogen Evolution Activity

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Angewandte Chemie 2018年第36期130卷

作者： Zhaojun Liu Jing Qi Moxuan Liu Shumeng Zhang Qikui Fan Hongpo Liu Kai Liu Haoquan Zheng Yadong Yin Chuanbo Gao Frontier Institute of Science and Technology and State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710054 China School of Chemistry and Chemical Engineering Shaanxi Normal University Xi'an Shaanxi 710119 China Department of Chemistry University of California Riverside CA 92521 USA

Although aqueous synthesis of nanocrystals is advantageous in terms of the cost, convenience, environmental friendliness, and surface cleanness of the product, nanocrystals of Pt and non‐noble metal alloys are difficult to obtain with controlled morphology and composition from this synthesis owing to a huge gap between the reduction potentials of respective metal salts. This huge gap could now be remedied by introducing a sulfite into the aqueous synthesis, which is believed to resemble an electroless plating mechanism, giving rise to a colloid of Pt‐M (M=Ni, Co, Fe) alloy nanowires with an ultrasmall thickness (ca. 2.6 nm) in a high yield. The sulfite also leads to the formation of surface M−S bonds and thus atomic‐level Pt/M–S(OH) interfaces for greatly boosted hydrogen evolution kinetics under alkaline conditions. An activity of 75.3 mA cm −2 has been achieved with 3 μg of Pt in 1 m KOH at an overpotential of 70 mV, which is superior to previously reported catalysts.

关键词： Dimetall-Legierungen Nanodrähte Platin Wasserstoffentwicklung Wässrige Synthesen

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An experimental study of two-phase pressure drop of liquid nitrogen in circular horizontal channels 1

An experimental study of two-phase pressure drop of liquid n...

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1st International Conference IIR of Cryogenics and Refrigeration Technology, ICCRT 2016

作者： Chen, Xingya Zhang, Qiaoyu Xue, Rong Lai, Tianwei Hou, Yu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University No.28 Xianning West Road Xi'an China School of Energy and Power Engineering Xi'an Jiaotong University No.28 Xianning West Road Xi'an China

ISBN: (纸本)9782362150173

Two-phase cryogenic flow are involved in many cooling systems. In order to study the mechanism of cryogenic two phase flow. Two-phase pressure drop of liquid nitrogen (LN2) in a circular horizontal channels was experimentally studied. A wide range of flow conditions: inlet pressure from 0.15 MPa to 0.30 MPa and mass flux from 120 kg/m2s to 320 kg/m2s, and tube diameters of 4 mm were performed in the experiment. The frictional pressure drop of two-phase LN2 in circular horizontal channel is estimated using two models, the homogeneous model and the separated flow model. In addition, the measured pressure drops are compared with those calculated from correlation models available for mini-scales. As a result, the homogeneous model with the Cicchitti et al. predict better than the other correlations mentioned in this study. © 2016, International Institute of Refrigeration. All rights reserved.

关键词： Two phase flow

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Recent advances in nanoporous graphene membrane for gas separation and water purification

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Science Bulletin 2015年第21期60卷 1807-1823页

作者： Chengzhen Sun Boyao Wen Bofeng Bai State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University

Graphene is a one-atom-thick sheet of graphite comprising sp2-hybridized carbon atoms arranged in the hexagonal honeycomb lattices. By removing the honeycomb lattices and forming nanopores with specific geometry and size, nanoporous graphene has been demonstrated as a very high-efficiency separation membrane, due to the ultrafast molecular permeation rate for its one-atom thickness. This review focuses on the recent advances in nanoporous graphene membrane for the applications of gas separation and water purification, with a major emphasis on the molecular permeation mechanisms and the advanced fabrication methods of this state-of-the-art membrane. We highlight the advanced theoretical and experimental works and discuss the gas/water molecular transport mechanisms through the graphene nanopores accompanied with theoretical models. In addition, we summarize some representative membrane fabrication methods, covering the graphene transfer to porous substrates and the pore generation. We anticipate that this review can provide a platform for understanding the current challenges to make the conceptual membrane a reality and attracting more and more attentions from scientists and engineers.

关键词： Nanoporous graphene Gas separationWater purification Molecular permeationmechanism Membrane fabrication

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Movement of Oil-Water-Solid Three-Phase Contact Line under Velocity Gradients

Movement of Oil-Water-Solid Three-Phase Contact Line under V...

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2016年大连国际微流控和芯片实验室大会

作者： Wenxiu ZHENG Chengzhen SUN Bofeng BAI State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

The movement of three-phase contact line which formed in the oil-water-solid three-phase area is of great importance in a number of applications,such as oil recovery,groundwater remediation,decontamination and *** process of oil droplets/film migration and detachment,which are controlled by the moving contact line,has shown its great significance in oil *** are various factors which can drive the contact line to move,such as pressure and electrical driving forces,etc,which will generate a velocity gradient for the flow near the *** this paper,we dedicate to investigate the moving rule of contact line under a velocity gradient from molecular dynamics(MD) ***,MD simulations are implemented by the FORCITE module in the Material Studio software to obtain the microscopic view of the moving contact *** size of the system is about 14 nm×3 nm×50 nm,including 2880 oil molecules and 33080 water *** interatomic interactions are described by COMPASS force field,for which van der Waals interaction is described by 9-6 Lennard-Jones potential and electronic interaction is described by Coulombic potential *** water and oil molecules are arranged on a silica substrate and the velocity gradient is generated by moving the upper *** water molecules we used SPC/E *** cutoff radius is 1.25 nm to the short-range intermolecular *** long-range Coulombic interactions are handled with the Ewald *** on the MD simulations,the configuration of water and oil molecules shows us the morphology of the contact line and variations of the contact angle at different velocity *** results exhibit that the contact line will move only when the velocity gradient is larger than a certain *** force inside the contact line region such as friction force and shear stress are calculated to make a deep understanding of the moving contact *** property of water/oil molecules and velocity profile

关键词： Movement of Oil-Water-Solid Three-Phase Contact Line under Velocity Gradients Velocity

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The effects of Na+ and Cl- ions on the oil-water interface:a molecular dynamics study

The effects of Na+ and Cl- ions on the oil-water interface:a...

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2016年大连国际微流控和芯片实验室大会

作者： Boyao Wen Chengzhen Sun Bofeng Bai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

Ions at the oil-water interface is a ubiquitous phenomenon which plays a important role in many industrial processes,such as extraction separation,nanoparticle assembly,enhanced oil recovery,*** the petroleum industry,due to the long-term interaction with solids and crude oil,the water including formation water,injection water and aqueous solution dissolves lots of ions,such as Na,K,Ca,Mg Cl,SO,*** migration of charged ions in the bulk phase or interface between oil and water has a significant influence on the molecular packing of active species at the interface,zeta potential of oil droplets and microstructure and strength of interfacial film by changing the interfacial tension,interface viscosity and electrical repulsion of charged ganglia,thus affecting the stability of crude oil emulsions and the oil displacement in porous ***,more detailed knowledge of how ions affect the properties of oil-water interface is ***,we perform a molecular dynamics（MD） study on the effects of ions on the oil-water interface using the LAMMPS package in the NVT *** temperature of the system is kept at 300 K via Nose-Hoover *** simulation box,whose volume equals to4×4×11.4 nm,is divided into two layers of oil and water *** boundary conditions are applied in x-,y-and *** is adopted as the oil phase according to "equivalent alkane carbon number"（EACN） value of crude *** are arranged uniformly in the water *** and Clions are involved,because they are basic components of brine and quite common in the *** atomic interactions between decane molecules are described by the OPLS-AA potential while the TIP3 P model of water is adopted to consider both dispersive and electrostatic *** cut-off distance of all potentials is 10 *** results demonstrate that the structures and dynamics of the oil-water interface is significantly affected by Na and *** kosmotropes,Na ions remain strongly h

关键词： The effects of Na and Cl ions on the oil-water interface:a molecular dynamics study

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Study on the Enhancement Effect of Dielectric Barrier Discharge on the Premixed Methane/Oxygen/Helium Flame Velocity

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Plasma Science and Technology 2015年第12期17卷 1019-1026页

作者：穆海宝喻琳李平汤成龙王金华张冠军 State Key Laboratory of Electrical Insulation and Power Equipment School of Electrical EngineeringXi'an Jiaotong University State key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

Recently,plasma-assisted combustion has become a potentially applicable technology in many combustion *** this paper,a dielectric barrier discharge（DBD） plasma generator is designed to explore the effect of plasma on the CH4 oxidation process,and several properties of combustion are ***,in the presence or absence of plasma discharge,physical appearance of the flame is examined and ***,the flame propagation velocity is calculated by the flame front extracted from the imaging data with the Bunsen burner ***,the main molecular components and their intensity variation in the flame and the plasma zones are identified with an emission spectrograph to analyze the effect of active species on the combustion *** also discuss the possible kinetic regime of plasma-assisted *** results imply that plasma discharge applied to the premixed CH_4/O_2/He mixture significantly raises the flame speed with equivalence ratios ranging from 0.85 to 1.10,with the flame speed improved by 17%to 35%.It can be seen that plasma can improve methane oxidation efficiency in the premixed fuel/oxidizer,especially at a low equivalence ratio.

关键词： combustion flame Oxygen equivalence appearance Velocity scenarios burning camera hydrocarbon

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Influence of wettability on motion of compound droplets on solid surface in microchannel flow

Influence of wettability on motion of compound droplets on s...

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2016年大连国际微流控和芯片实验室大会

作者： Xinglong Shang Bofeng Bai State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University

To understand droplet motion on solid surfaces is very important for many applications such as enhanced oil recovery（Freitas et al.2011）,droplet spreading,manipulation and fabrication of droplets in microfluidic devices（Worner et al.2012）.Solid surface wettability affects significantly the movement of the contact line and hence dominants the motion of droplets on solid surfaces,especially when the flow is confined to ***,the compound droplets are often common with the applications mentioned above（e.g.,water-in-oil-in-water and oil-in-water-in-oil type compound droplet）.Furthermore,the wettability of solid surfaces is often heterogeneous that make the drop motion more *** aim of this work is to investigate the influence of solid surface wettability（e.g.,solid surface wettability gradient and contact angle hysteresis） on the motion of compound droplets in microchannel *** this end,we develop a three-dimensional model by combining the front tracking method for drop surface motion and the generalized Navier boundary condition（Qian et al.2003） for contact line *** front tracking method to model the deformation and motion of compound droplets surrounded by elastic interfaces has been developed and validated in our previous work（Bai et al.2012;Luo et al.2015）.The presence of inner droplet significantly influences the deformation and motion of compound droplets on solid *** to the results from previous two-dimensional front tracking methods（Huang et al.2004） and other numerical methods（Ding et al.2010）,the pattern of ripples is observed in our simulations on the drop *** effects of dimensionless numbers including the Reynolds number,the capillary number and the volume ratio of the inner to the outer droplet are ***,it is demonstrated that the gradient of solid surface wettability and the hysteresis of contact angle have a remarkable effect on the deformation and motion of compound droplets.

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A ‐Oriented Hittorf's Phosphorus Nanorods/Polymeric Carbon Nitride Heterostructure for Boosting Wide‐Spectrum‐Responsive Photocatalytic Hydrogen Evolution from Pure Water

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Angewandte Chemie 2019年第2期132卷

作者： Yukun Zhu Chunxiao Lv Zhuocheng Yin Jun Ren Xianfeng Yang Chung‐Li Dong Hongwei Liu Rongsheng Cai Yu‐Cheng Huang Wolfgang Theis Shaohua Shen Dongjiang Yang State Key Laboratory of Bio-fibers and Eco-textiles Shandong Collaborative Innovation Center of Marine Biobased Fibers and Ecological Textiles Institute of Marine Biobased Materials School of Environmental Science and Engineering Qingdao University Qingdao 266071 P. R. China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 P. R. China School of Chemical and Environmental Engineering North University of China Taiyuan 030051 P. R. China Analytical and Testing Centre South China University of Technology Guangzhou 510640 P. R. China Research Center for X-ray Science & Department of Physics Tamkang University Tamsui 25137 Taiwan The Australian Centre for Microscopy & Microanalysis The University of Sydney Sydney New South Wales 2006 Australia Nanoscale Physics Research Laboratory School of Physics and Astronomy University of Birmingham Birmingham B15 2TT UK

Red phosphorus is a promising photocatalyst with wide visible‐light absorption up to 700 nm, but the fast charge recombination limits its photocatalytic hydrogen evolution reaction (HER) activity. Now, [001]‐oriented Hittorf's phosphorus (HP) nanorods were successfully grown on polymeric carbon nitride (PCN) by a chemical vapor deposition strategy. Compared with the bare PCN and HP, the optimized PCN@HP hybrid exhibited a significantly enhanced photocatalytic activity, with HER rates reaching 33.2 and 17.5 μmol h −1 from pure water under simulated solar light and visible light irradiation, respectively. It was theoretically and experimentally indicated that the strong electronic coupling between PCN and [001]‐oriented HP nanorods gave rise to the enhanced visible light absorption and the greatly accelerated photoinduced electron–hole separation and transfer, which benefited the photocatalytic HER performance.

关键词： Heterostrukturen Nanostäbe Hittorfscher Phosphor Kohlenstoffnitrid Wasserspaltung

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Multi-source driven capillary plane radiation air conditioning system

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AIP Conference Proceedings 2017年第1期1864卷

作者： Juanjuan Hu Mofeng Qu Huasheng Wang Shiyao Ni State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an China

A new absorption refrigeration system, which is driven by solar energy, biomass energy and geothermal energy simultaneously, was designed with capillaries as its radiation surface. Likewise, variations of water temperature in the capillaries with the change in both time and its flow rate were experimentally researched as well as how COP of the system varies with the surrounding temperature. The following conclusions have been obtained: Common refrigeration demand can be met by the system after its operation in 1 hour; with the increase in water flow rate in the capillaries, its temperature, which drops down after an increase, gets its peak value at the flow rate of 4.5-5.5 L/min; COP of the system decreases with the rise of surrounding temperature, thus it’s better to keep it from direct sunlight. With the utilization of natural energy and the structure of capillaries, the system’s advantages in simple structure, low cost, environment-friendly working process and nice performance lead to promising application prospects, especially in residence refrigeration in countryside.

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