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Table of Content
28 May 2020, Volume 28 Issue 5
    Fluid Dynamics and Transport Phenomena
    Gas dispersion and solid suspension in a three-phase stirred tank with triple impellers
    Hanbin Wang, Zhengming Gao, Bingjie Wang, Yuyun Bao, Ziqi Cai
    2020, 28(5):  1195-1202.  doi:10.1016/j.cjche.2019.09.013
    Abstract ( 302 )   PDF (1329KB) ( 62 )  
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    The hydrodynamics is still not fully understood in the three-phase stirred tank equipped with multi-impeller due to the intensive interaction between phases. In this work, the solid critical suspension speed (NJSG), relative power demand (RPD) and overall gas holdup (εG) were measured in an air-water-glass beads stirred tank equipped with multi-impeller, which consists of a parabolic blade disk turbine below two down-pumping hydrofoils. Results show that either the NJSG or the specific power consumption increases when increasing the volumetric solid concentration or superficial gas velocity. RPD changes less than 10% when solid volumetric concentration ranges from 0 to 15%. εG decreases with the increase of solid concentration, and increases with the increase of both superficial gas velocity and the total specific power consumption. The quantitative correlations of NJSG, RPD and εG were regressed as the function of superficial gas velocity, specific power consumption, Froude number and gas flow number, in order to provide the reference in the design of such three-phase stirred tank with similar multi-impellers.
    Effects of porous material on transient natural convection heat transfer of nano-fluids inside a triangular chamber
    Mohsen Izadi
    2020, 28(5):  1203-1213.  doi:10.1016/j.cjche.2020.01.021
    Abstract ( 222 )   PDF (7164KB) ( 22 )  
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    This study numerically investigates the impact of porous materials, nano-particle types, and their concentrations on transient natural convection heat transfer of nano-fluid inside a porous chamber with a triangular section. The governing equations of the two-phase mixture model are separated on the computational domain and solved using the Finite Volume Method, taking into account the Darcy-Brinkman model for porous medium. It was observed that convection heat transfer inside the triangular chamber consists of three stages named initial, transient, and semi-steady. The features of each step are provided in detail. The results suggested that the use of a hybrid nano-fluid (water/aluminum oxide-cooper) inside a porous glass material and an increase in volume fraction of nano-particles have adverse effects on heat transfer rate. In contrast, as the nano-particle volume fraction of the single nano-fluid (water/aluminum oxide) inside the chamber increased, convection heat transfer rate improved. At the same time, it was observed that the use of both nano-fluids (single and hybrid) in the porous environment of the aluminum foam could improve convection.
    Plume dynamics and dispersion characteristics in oil horizontal release from damaged submarine pipeline
    Jun Zhang, Hongzhou He, Shaohui Yang
    2020, 28(5):  1214-1224.  doi:10.1016/j.cjche.2020.03.004
    Abstract ( 272 )   PDF (4377KB) ( 39 )  
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    The dynamics model of plume for underwater oil spill is improved by considering the drag force of the plume. The comparisons between prediction and experiment show that the improved model is viable. The improved model combining the Lagrangian random walk method is used to simulate the entire oil transport process from release exit to water surface in underwater oil horizontal release and some new results are obtained. Firstly, the release rate, the current velocity and its direction have evident influence on plume dynamics. The plume length increases as release flow rate increases. For small oil release rate, the plume length is very short so that the plume stage can be ignored due to the small initial momentum. When the oil release in direction is the same as the current, the current will play a positive role in the plume motion and the plume will therefore extend a longer distance. In this case, the greater the current velocity is, the longer the plume extension length will be. And when the oil release in direction is opposite to the current, the plume first moves forward and then is reversed to move along the opposite direction. The position of the reversal point depends on the current velocity and the release rate. Secondly, the release rate and the current velocity also have a significant effect on oil droplet diffusion. For small oil release rate, the oil distribution area is narrow and the concentration near upper side of droplets moving path is relatively higher. As the release rate or current velocity increases, the oil droplet diffusion area expands away from the release point. Finally, the movement characteristics of oil droplets in the plume and diffusion stages will affect the time and location for oil droplets reaching the surface. In a small release rate as well as a small current velocity, the time for oil droplet reaching surface is very short and the horizontal position reaching surface is closer to release point. In this case, the time spent in the plume stage is extremely short compared to the time spent in the entire oil motion process. Therefore, the plume dynamics stage can be ignored in this case. With the increase of release rate or current velocity, the plume will be extended and the time spent in plume dynamics stage will also be longer, so the plume dynamics stage can no longer be ignored for larger release rate or current velocity. In the case of reverse current, as the plume momentum be partially consumed by the reverse current, the plume is reversed and decays quickly, the time taken in the plume dynamics stage is relatively shorter than that for positive current. Correspondingly, the total time is also somewhat shortened.
    Mixed convection in the heated semi-circular lid-driven cavity for nonNewtonian power-law fluids: Effect of presence and shape of the block
    Krunal M. Gangawane, Hakan F. Oztop
    2020, 28(5):  1225-1240.  doi:10.1016/j.cjche.2020.03.005
    Abstract ( 253 )   PDF (9182KB) ( 23 )  
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    The present work delineates the hydrodynamics and thermal characteristics due to mixed convection in the liddriven semi-circular cavity affected by the presence of the adiabatic block at its geometric center for twodimensional, steady-state, laminar and for non-Newtonian power-law fluids. The semi-circular cavity has a diameter of D. The horizontal wall/lid is sliding with a uniform horizontal velocity (u=U) and is subjugated to the ambient thermal condition; while the curved surface is subjugated to a higher isothermal temperature. The convective characteristics inside the system is explored for the broad range of Richardson number (0.1 ≤ Ri ≤ 10), Prandtl number (1 ≤ Pr ≤ 100) and non-Newtonian power-law index (0.5 ≤ n ≤ 1.5) at a constant Grashof number of 104. Apart from this, the effect of shape (cross-section) of the inserted block, i.e., circular, square and triangular on heat transfer characteristics has also been explored. It is observed that the shear thickening fluids display better cooling characteristics. Besides, the cavity with immersed triangular block shows better heat transfer results than the circular and square blocks. The deviations observed in the flow and heat transfer characteristics in the cavity by inserting an adiabatic block as compared with cavity without block have been ascertained by calculating normalized Nusselt number (NuN). The presence of the block was found to have a diminishing effect on the heat transfer due to convection in the cavity. In the end, the results of the study are summarized in the form of a predictive correlation exhibiting the functional dependence of average Nusselt number with Prandtl number, power-law index, and Richardson number.
    Formation of mono-dispersed droplets with electric periodic dripping regime in electrohydrodynamic (EHD) atomization
    Zhentao Wang, Qisi Wang, Yaosheng Zhang, Yimin Jiang, Lei Xia
    2020, 28(5):  1241-1249.  doi:10.1016/j.cjche.2020.03.008
    Abstract ( 219 )   PDF (2286KB) ( 57 )  
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    The formation of controllable size and dripping frequency in electrohydrodynamic (EHD) atomization with electric periodic dripping regime are of much interest and importance because of significant and wide applications, such as micro-encapsulation and ink-printing. In the present study, the experimental and theoretical works were carried out to explore droplet formation in periodic dripping regime in presence of an electric field. The dimensionless electric charge carried by each droplet produced is smaller than the 50% of critical value of the Rayleigh limit, where charge-to-mass ratio of droplets was obtained through the deflection distance in the presence of an electric field. The droplet in electric periodic dripping regime usually undergoes oscillating deformation, and finally forms a spherical droplet below the tip no more than ten times out diameter of tube. The droplet size tens of microns to one hundreds of microns decreases with an increase in applied potential. In the electric dripping mode, droplets size is independent of flow rate and affected by flow rate due to adsorption of surface active species in micro-dripping. The simplified model to predict droplets size was derived from the balance of electric, surface tension and gravity forces. The droplets size calculated in good agreement with the experiments. Meanwhile, the dripping frequency of droplets with rang of a few to several hundred hertz obtained from timeresolved images is highly dependent of liquid flow rate and electric potential. The largest dripping frequency was predicted and in reasonable agreement with the experimental results. In electric periodic dripping regime drop-on-demand droplets in size and dripping frequency further our understanding on the formation of identical droplets and are beneficial to many practical applications.
    Separation Science and Engineering
    Performance evaluation of a bubble generator and a bubble separator designed for the gas removal system of a small thorium molten salt reactor
    Licheng Sun, Liang Zhao, Min Du, Zhengyu Mo, Jiguo Tang, Guo Xie
    2020, 28(5):  1250-1259.  doi:10.1016/j.cjche.2019.01.035
    Abstract ( 258 )   PDF (5236KB) ( 127 )  
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    In the present study, a bubble generator and a bubble separator were designed and evaluated for an independent off-gas removal system of a small thorium molten salt reactor (TMSR) with reference to the design of the Oak Ridge National Laboratory (ONRL). The bubble generator employed a Venturi tube as its main body owing to its simplicity and highly reliable structure. A centrifugal separator was used as the bubble separator, taking advantage of the kinetic energy of fluid to create a centrifugal force to separate gas bubbles from the mixture flow. Both the bubble generator and the separator were demonstrated to have good potential to meet the performance requirements of an off-gas removal system for a small TMSR. With water and air as the working fluids, for the final designs of the two key pieces of equipment, a liquid flow rate exceeding 15 m3·h-1 can essentially make their performance meet the requirements of the off-gas removal system in terms of the average size of the generated bubbles and gas separation efficiency.
    A bifunctional MnOx@PTFE catalytic membrane for efficient low temperature NOx-SCR and dust removal
    Shasha Feng, Mengdi Zhou, Feng Han, Zhaoxiang Zhong, Weihong Xing
    2020, 28(5):  1260-1267.  doi:10.1016/j.cjche.2019.11.014
    Abstract ( 173 )   PDF (4081KB) ( 37 )  
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    Low-temperature selective catalytic reduction of NOx combined with dust removal technique due to its energy conservation characteristic has been attracted much attention for fume purification. In this work, the MnOx wrapped PTFE membrane with efficient dust removal and low-temperature NH3-SCR has been prepared with a facile route. MnOx with different crystal structures was uniformly grown around the PTFE fibrils through water bath. The flower-sphere-like MnOx@PTFE(O-MnOx@PTFE) and lamellar-interlaced ripple-like MnOx@PTFE(W-MnOx@PTFE) have large specific surface area which is favorable for enhancing catalytic performance. Also, the uniformly wrapped W-MnOx around the PTFE fibrils optimized the pore structure for ultrafine dust capture. The membrane can almost 100% reject particles that are smaller than 1.0 μm with a low filtration resistance. Meanwhile, W-MnOx@PTFE with more surface chemisorbed oxygen has the best NO conversion efficiency of 100% at a comparatively low and wide activity temperature window of 160-210℃, which is far to the thermal limitation of the PTFE. Therefore, this efficient and energy conserving membrane has a bright application prospects for tail gas treatment compared to the original treatment process.
    Separation of methane from different gas mixtures using modified silicon carbide nanosheet: Micro and macro scale numerical studies
    Golchehreh Bayat, Roozbeh Saghatchi, Jafar Azamat, Alireza Khataee
    2020, 28(5):  1268-1276.  doi:10.1016/j.cjche.2019.12.005
    Abstract ( 257 )   PDF (4557KB) ( 169 )  
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    This research discusses the separation of methane gas from three different gas mixtures, CH4/H2S, CH4/N2 and CH4/CO2, using a modified silicon carbide nanosheet (SiCNS) membrane using both molecular dynamics (MD) and computational fluid dynamics (CFD) methods. The research examines the effects of different structures of the SiCNSs on the separation of these gas mixtures. Various parameters including the potential of the mean force, separation factor, permeation rate, selectivity and diffusivity are discussed in detail. Our MD simulations showed that the separation of CH4/H2S, and CH4/CO2 mixtures was successful, while simulation demonstrated a poor result for the CH4/N2 mixture. The effect of temperature on the diffusivity of gas is also discussed, and a correlation is introduced for diffusivity as a function of temperature. The evaluated value for diffusivity is then used in the CFD method to investigate the permeation rate of gas mixtures.
    Conceptual design of energy-saving stripping process for industrial sour water
    Hengjun Gai, Shuo Chen, Kaiqiang Lin, Xiaowei Zhang, Chun Wang, Meng Xiao, Tingting Huang, Hongbing Song
    2020, 28(5):  1277-1284.  doi:10.1016/j.cjche.2019.12.020
    Abstract ( 189 )   PDF (986KB) ( 322 )  
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    Sour water contains ammonia, carbon dioxide, and hydrogen sulfides, producing from oil refining, coking, and coal gasification. To reduce the energy consumption in sour water stripping, a novel process is proposed which integrates with the bottom flashing mechanical vapor recompression heat pump (MVRHP) for treating such wastewater. Here, Aspen PlusTM as a powerful set of chemical process simulation software is utilized to investigate the economy and feasibility of the novel process. Comparison of the results of two process simulations, it can be seen that it is possible to reduce the total annual cost by nearly 45% to adopt the novel process, despite the capital investment increase 45% more than the conventional process. Thus, the provided conceptual design will play a guiding role in the industrialization of the process.
    High-performance SSZ-13 membranes prepared using ball-milled nanosized seeds for carbon dioxide and nitrogen separations from methane
    Xinping Li, Yaowei Wang, Tangyin Wu, Shichao Song, Bin Wang, Shenglai Zhong, Rongfei Zhou
    2020, 28(5):  1285-1292.  doi:10.1016/j.cjche.2020.02.004
    Abstract ( 276 )   PDF (1499KB) ( 92 )  
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    SSZ-13 membranes with high separation performances were prepared using ball-milled nanosized seeds by once hydrothermal synthesis. Separation performances of SSZ-13 membranes in CO2/CH4 and N2/CH4 mixtures were enhanced after synthesis modification. Single-gas permeances of CO2, N2 and CH4 and ideal selectivities were recorded through SSZ-13 membranes. The effects of temperature, pressure, feed flow rate and humidity on separation performance of the membranes were discussed. Three membranes prepared after synthesis modifications had an average CO2 permeance of 1.16×10-6 mol·(m2·s·Pa)-1 (equal to 3554 GPU) with an average CO2/CH4 selectivity of 213 in a 50 vol%/50 vol% CO2/CH4 mixture. It suggests that membrane synthesis has a good reproducible. The membrane also displayed a N2 permeance of 1.07×10-7 mol·(m2·s·Pa)-1 (equal to 320 GPU) with a N2/CH4 selectivity of 13 for a 50 vol%/50 vol% N2/CH4 mixture. SSZ-13 membrane displayed stable and good separation performance in the wet CO2/CH4 mixture for a long test period over 100 h at 348 K. The current SSZ-13 membranes show great potentials for the simultaneous removals of CO2 and N2 in natural gas purification as a facile process suitable for industrial application.
    Hydrogen bond promoted thermal stability enhancement of acetate based ionic liquid
    Ling Zhang, Ligang Wei, Shangru Zhai, Dingwei Zhao, Jian Sun, Qingda An
    2020, 28(5):  1293-1301.  doi:10.1016/j.cjche.2020.02.019
    Abstract ( 232 )   PDF (2078KB) ( 123 )  
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    Acetate-based imidazolium ionic liquids (ILs) are of great importance and widely applied in biomass processing and engineering but under stability issue due to the structure self-rearrangement induced by C2-H deprotonation, by which the IL based biomass processing will be challenging. Herein, we demonstrated that the thermal stability of normal acetate-based imidazolim[C8C1Im] [OAc] could be significantly improved by changing its cation and anion environment with the presence of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide IL ([C4C1Im] [NTf2]). When the molar fraction of[C8C1Im] [OAc] was 0.3, the thermal stability of[C8C1Im] [OAc] could be significantly improved (ΔT5%dec=+43℃). Detailed information obtained from thermal gravimetric analysis (TGA) and nuclear magnetic resonance (NMR) revealed that the addition of[C4C1Im] [NTf2] played a significant role in enhancing the thermal stability of[C8C1Im] [OAc]. It was proposed that the formation of an anion-π+ structure network between[C8C1Im] [OAc] and[C4C1Im] [NTf2] via strong hydrogen bond interactions greatly affects the environment of hydrogen atom in the imidazolium ring of each IL.
    Catalysis, Kinetics and Reaction Engineering
    Preparation of ZSM-5 containing vanadium and Brønsted acid sites with high promoting of styrene oxidation using 30% H2O2
    Xianfeng Liu, Fu Yang, Shuying Gao, Bo Shao, Shijian Zhou, Yan Kong
    2020, 28(5):  1302-1310.  doi:10.1016/j.cjche.2020.01.002
    Abstract ( 371 )   PDF (2579KB) ( 78 )  
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    Design and synthesis of low cost and efficacious industrial catalyst for the oxidation of styrene has been an important research project. Herein, ZSM-5 zeolite containing tetrahedral vanadium (V) and Brønsted acid sites (V-H-ZSM-5) was prepared, and identified by characterizations such as XRD, SEM, UV-vis, NH3-TPD, H2-TPR N2-adsorption/desorption and FTIR. V-H-ZSM-5 performed extremely enhanced catalytic activity for the oxidation of styrene with 30% H2O2 at 40℃. Moreover, in-situ FTIR spectrum was used to investigate the catalytic mechanism. The results demonstrate that Brønsted acid site could not only increase the adsorption concentration of styrene in the micropores of V-H-ZSM-5 via the π complex interaction between double bond of styrene and Brønsted acid sites, but also increase the oxidation potential of H2O2. The synergetic action of tetrahedral vanadium (V) and Brønsted acid enhanced the catalytic activity for the oxidation of styrene with 30% H2O2. Impressively, V-H-ZSM-5 performed high reusability within five runs at a low reaction temperature (40℃) for the first time.
    Hydrothermal treatment of metallic-monolith catalyst support with selfgrowing porous anodic-alumina film
    Chuanqi Zhang, Yuanjing Pu, Feng Wang, Hecheng Ren, Hua Ma, Yu Guo
    2020, 28(5):  1311-1319.  doi:10.1016/j.cjche.2020.01.012
    Abstract ( 310 )   PDF (3150KB) ( 77 )  
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    Metallic-monolith catalyst support with self-growing porous anodic alumina (PAA) film was prepared by anodizing Al plate. The effect of hydrothermal treatment (HTT) on the crystalline state and textural properties of PAA film was investigated by XRD, BET, SEM and TG. The HTT treatment above 50℃ and the subsequent calcination above 300℃ could convert the amorphous skeleton alumina into γ-alumina and increase the specific surface area (SBET). However, SEM images showed the HTT modification was a non-uniform process along the thickness of PAA film. The promotion effect of HTT on SBET was non-linear, and the slope of SBET gradually decreased with the HTT temperature or time increased. The limited HTT effect should be attributed to a changed pore structure caused by an unfavorable pore sealing limitation. Pore widening treatment (PWT) before HTT could break the pore sealing limitation, because of the reduced internal diffusion resistance of hydrothermal reaction. The synergistic combination of PWT and HTT developed a PAA support with a large SBET comparable to commercial γ-alumina. In the catalytic combustion of toluene, the Pt-based catalyst prepared by using the PWT and HTT comodified PAA support gave higher Pt dispersion and more favorable catalytic activity than that treated by HTT alone. The presence of a bimodal pore structure was suggested to be a decisive reason.
    A circular microreaction method to the safe and efficient synthesis of 3-methylpyridine-N-oxide
    Funing Sang, Jinpei Huang, Jianhong Xu
    2020, 28(5):  1320-1325.  doi:10.1016/j.cjche.2020.02.002
    Abstract ( 280 )   PDF (1600KB) ( 127 )  
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    3-Methylpyridine-N-oxide is an essential intermediate in the preparation of 2-chloro-5-methylpyridine, which can be used to synthesize nicotine insecticides such as imidacloprid and acetamiprid. The traditional method of production of 3-methylpyridine-N-oxide is catalytic oxidation of 3-methylpyridine in semi-batch reactors. Due to strong exothermic reaction and explosive property of 3-methylpyridine, the reaction efficiency and safety is low using batch technology. Therefore, the development of a safer and efficient 3-methylpyridine-N-oxide production process is very necessary in industrial production. In this paper, microreaction systems were introduced into the preparation of 3-methylpyridine-N-oxide. The comparison of three different methods (traditional semibatch method, co-current microreaction method, and circular microreaction method) showed that the circular microreaction method was the most applicable, with relative higher product yield (~90%), less side reaction and better reaction control.
    Kinetics and the difference for extraction of praseodymium and neodymium from nitrate aqueous solution by[A336] [NO3] using the single drop technique
    Xiaoqin Wang, Kun Huang, Wenjuan Cao, Pan Sun, Weiyuan Song, Huizhou Liu
    2020, 28(5):  1326-1333.  doi:10.1016/j.cjche.2020.02.010
    Abstract ( 268 )   PDF (1716KB) ( 46 )  
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    The kinetics and the difference for Pr(III) and Nd(III) extraction from nitrate aqueous solution using trialkylmethylammonium nitrate ([A336] [NO3]) as extractant were investigated by the single drop technique. The dependence of the extraction rate of Pr(III) and Nd(III) on the concentrations of free Pr(III) and Nd(III) ions, the concentrations of NaNO3 and H+ in aqueous solutions, and the concentrations of[A336] [NO3] in kerosene solutions were discussed and the corresponding extraction rate equations for Pr(III) and Nd(III) were obtained. These equations demonstrated that the reaction rate constant of Pr(III) with[A336] [NO3] was double than that of Nd(III). The effect of the addition of diethylenetriaminepentaacetic acid (DTPA) on the difference in the extraction rate of Pr(III) and Nd(III) by[A336] [NO3] was also investigated. It was revealed that the difference in the complex formation rates of Pr(III) and Nd(III) with DTPA made a significant impact on the difference in the extraction rates of Pr(III) and Nd(III) with[A336] [NO3]. The ratio of extraction rates of Pr(III) to Nd(III) with[A336] [NO3] was in proportion to the ratio of complex formation rates of Pr(III) to Nd(III) with DTPA. The extraction rate difference for Pr(III) and Nd(III) with[A336] [NO3] increased due to a higher complex formation rate constant of DTPA with the free and un-complexed Nd(III) ions in the aqueous nitrate solution than that with Pr(III) ions. Therefore, the addition of DTPA in the aqueous nitrate solution is an effective method to intensify the separation of Pr(III) and Nd(III) in kinetics. The study on the extraction mechanism indicated that both the extraction of Pr(III) and Nd(III) by[A336] [NO3] were diffusion controlled, and the reactions obeyed SN2 mechanism. The present work highlights a possible approach to strengthen the kinetic separation of Pr(III) and Nd(III).
    Bio-synthesized palladium nanoparticles using alginate for catalytic degradation of azo-dyes
    Yi Xiong, Liping Huang, Sakil Mahmud, Feng Yang, Huihong Liu
    2020, 28(5):  1334-1343.  doi:10.1016/j.cjche.2020.02.014
    Abstract ( 271 )   PDF (9503KB) ( 19 )  
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    Palladium nanoparticles (PdNPs) were synthesized in a green way using sodium alginate functioning as both reductant and stabilizer. The formation of as-synthesized PdNPs was supervised by Ultraviolet-visible (UV-Vis) spectroscopy and confirmed by the surface plasmon resonance (SPR) band. The effect of several synthesis factors such as precursor ratio, solution pH, reaction time, and temperature were investigated by the factorial design of experiments in order to optimize the experimental conditions. The optimal synthesis parameters were achieved by heating 1.0 ml of 1.0% sodium alginate (SA), 3.0 ml of 10-2 mol·L-1 H2PdCl4 at 80℃ for a period of 30 min in a neutral reaction medium (pH=6). High-resolution transmission electron microscope (HRTEM), energy dispersive X-ray (EDX) spectroscopy, selected area electron diffraction (SAED) pattern, X-ray powder diffraction (XRD), and dynamic light scattering (DLS) were used to confirm the uniform spherical shapes and high crystallinity of PdNPs with average particle size of (2.12 ±1.42) nm. The SEM images show the distribution of PdNPs presented among the SA. FTIR spectra indicate that SA is a good capping agent to stabilize PdNPs for a long time. The catalytic degradation of model azo-dyes such as mono-azo (Cibacron Yellow FN-2R) and di-azo (Cibacron Deep Red S-B) were confirmed the catalytic activity of PdNPs. The PdNPs can accelerate the degradation rate by more than 80 and 10 times respectively as confirmed by kinetics constant (k) values.
    Process Systems Engineering and Process Safety
    Simultaneous synthesis of sub and above-ambient heat exchanger networks including expansion process based on an enhanced superstructure model
    Yu Zhuang, Rui Yang, Lei Zhang, Jian Du, Shengqiang Shen
    2020, 28(5):  1344-1356.  doi:10.1016/j.cjche.2020.02.026
    Abstract ( 193 )   PDF (661KB) ( 60 )  
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    Synthesis of heat exchanger networks including expansion process is a complex task due to the involvement of both heat and work. A stream that expands through expanders can produce work and cold load, while expansion through valves barely affects heat integration. In addition, expansion through expanders at higher temperature produces more work, but consumes more hot utility. Therefore, there is a need to weigh work production and heat consumption. To this end, an enhanced stage-wise superstructure is proposed that involves synchronous optimization of expander/valve placement and heat integration for each pressure-change sub-stream in stages. A mixed-integer nonlinear programming (MINLP) model is established for synthesizing sub and aboveambient heat exchanger networks with multi-stream expansion, which explicitly considers the optimized selection of end-heaters and end-coolers to adjust temperature requirement. Our proposed method can commendably achieve the optimal selection of expanders and valves in a bid for minimizing exergy consumption and total annual cost. Four example studies are conducted with two distinct objective function (minimization of exergy consumption and total annual cost, respectively) to illustrate the feasibility and efficacy of the proposed method.
    Amine-based solvent for CO2 absorption and its impact on carbon steel corrosion: A perspective review
    Zhe Lun Ooi, Pui Yee Tan, Lian See Tan, Swee Pin Yeap
    2020, 28(5):  1357-1367.  doi:10.1016/j.cjche.2020.02.029
    Abstract ( 306 )   PDF (2803KB) ( 693 )  
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    Carbon dioxide (CO2) is one of the commonly emitted gaseous by-products in industrial processes. While CO2 gas is the main cause to greenhouse effect, various CO2 capture technologies have been proposed and implemented to sequester the CO2 before the waste gases being released into the atmosphere. One of the mature technologies for CO2 absorption is by using amine-based solvents. In this regard, different single amine solvents or blended amine solvents have been proven for their capability to remove CO2. However, the dissolution and reaction of CO2 gas with the amine solvents turn the solution corrosive. Such phenomenon is undesired as it posts corrosion problem to the absorption column, which normally built of carbon steel material. Henceforth, understanding the behaviour of different amine-based solvents in absorbing CO2 and its subsequent impact on carbon steel corrosion is very significant. In this review article, we will outline some of the more commonly used solvents and their respective advantages and disadvantages, motivating further investigation into the corrosion tendency. Meanwhile, existing gaps in this research area are discussed for future investigation.
    Chemical Engineering Thermodynamics
    A novel approach to study the interactions between polymeric stabilized micron-sized oil droplets by optical tweezers
    An Chen, Shaowei Li, Jianhong Xu
    2020, 28(5):  1368-1374.  doi:10.1016/j.cjche.2019.12.010
    Abstract ( 187 )   PDF (2083KB) ( 67 )  
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    The well understanding of interaction forces between single dispersed droplets is crucial to the understanding of emulsion stabilization mechanism. Recently, many studies have reported the direct quantitative measurements of interaction forces between 20-200 μm single droplet coated polymers by atomic force microscope (AFM). These studies have revealed many important results about the relationship of the interaction forces and the droplet deformation. However, these studies of the quantitative relationship between the measured interaction forces and the separation distance of the front end of the droplet have rarely been reported. Optical tweezer instrument can make it possible to establish the quantitative relationship between the measured force and the separation distance of the front end of the droplet, which will make better understanding of the interaction mechanisms between droplets. Due to the differences of the measuring mechanism between atomic force microscopy (AFM) and optical tweezers, the theory model of AFM measurements cannot be fitted with the force measurement by optical tweezers. We have made an exhaustive comparison of the measuring differences between AFM and optical tweezer instrument in this work. Moreover, we built a numerical model to derive the repulsive pressure through the measured force curve in order to quantify the measured force of two micron-sized oil droplet coated polymers by optical tweezers. Furthermore, the novel method can be extended to other micron-sized emulsion systems, and these findings will be a vital progress on quantitative force measurements between micron-sized droplets.
    Energy, Resources and Environmental Technology
    Single and competitive adsorption affinity of heavy metals toward peanut shell-derived biochar and its mechanisms in aqueous systems
    Rui Shan, Yueyue Shi, Jing Gu, Yazhuo Wang, Haoran Yuan
    2020, 28(5):  1375-1383.  doi:10.1016/j.cjche.2020.02.012
    Abstract ( 238 )   PDF (3688KB) ( 248 )  
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    Converting peanut shells into biochar by pyrolysis was considered an environmentally friendly and efficient method for agricultural solid waste disposal. The properties of peanut shell-derived biochar (PBC) under different temperature and its adsorption capacity of heavy metals were investigated. It was found that PBC400 exhibited the highest cumulative capability for heavy metals elimination in single solute because of its high specific surface area and rich functional groups. Furthermore, the competitive adsorption revealed that PBC had a substantial difference in adsorption affinity from diverse heavy metal ions, sorption capacity decreased as Pb2+ > Cu2+ > Cd2+ > Ni2+ > Zn2+, which was lower than in a single solute. The adsorption process using selected biochar was optimized with respect to pH, reaction time, adsorbent dose, and initial concentration of heavy metals. The kinetic data was well fitted with PSO model, and the Langmuir model was adopted for adsorption equilibrium data in both cases of single solutes and mixed solutes for all heavy metals, which indicated that the removal course was primarily explained by monolayer adsorption, and chemical adsorption occupied an important role. Therefore, peanut shells derived biochar could be a potential and green adsorbent for wastewater treatment.
    Optimization of a continuous ultrasound assisted oxidative desulfurization (UAOD) process of diesel using response surface methodology (RSM) considering operating cost
    Mohammad Dana, Mohammad Amin Sobati, Shahrokh Shahhosseini, Aminreza Ansari
    2020, 28(5):  1384-1396.  doi:10.1016/j.cjche.2019.12.007
    Abstract ( 314 )   PDF (4655KB) ( 198 )  
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    A continuous-flow ultrasound-assisted oxidative desulfurization (UAOD) of partially hydro-treated diesel has been investigated using hydrogen peroxide-formic acid as simple and easy to apply oxidation system. The effects of different operating parameters of oxidation stage including residence time (2-24 min), formic acid to sulfur molar ratio (10-150), and oxidant to sulfur molar ratio (5-35) on the sulfur removal have been studied using response surface methodology (RSM) based on Box-Behnken design. Considering the operating costs of the continuous-flow oxidation stage including chemical and electrical energy consumption, the appropriate values of operating parameters were selected as follows:residence time of 16 min, the formic acid to sulfur molar ratio of 54.47, and the oxidant to sulfur molar ratio of 8.24. In these conditions, the sulfur removal and the volume ratio of the hydrocarbon phase to the aqueous phase were 86.90% and 4.34, respectively. By drastic reduction in the chemical consumption in the oxidation stage, the volume ratio of the hydrocarbon phase to the aqueous phase was increased up to 10. Therefore, the formic acid to sulfur molar ratio and the oxidant to sulfur molar ratio were obtained 23.64 and 3.58, respectively, which lead to sulfur removal of 84.38% with considerable improvements on the operating cost of oxidation stage in comparison with the previous works.
    Photodegradation of benzothiazole ionic liquids catalyzed by titanium dioxide and silver-loaded titanium dioxide
    Jinghang Li, Huimin Zang, Shun Yao, Zicheng Li, Hang Song
    2020, 28(5):  1397-1404.  doi:10.1016/j.cjche.2020.02.006
    Abstract ( 219 )   PDF (2606KB) ( 40 )  
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    In recent years, ionic liquids (ILs) have been widely used in extraction, synthesis, electrochemistry and other fields. Meanwhile, the environmental impact of ILs has been attracting a lot of attention, and eco-friendly treatment for ILs is becoming a necessary subject. In this study, photocatalytic degradations of benzothiazole ILs catalyzed by titanium dioxide (TiO2) and silver-loaded titanium dioxide (Ag/TiO2) were studied for the first time. The degradation of benzothiazole hexafluorophosphate ([C4Bth]PF6) could reach more than 99% within 240 min with the catalysis of TiO2. To improve catalytic efficiency, Ag/TiO2 was synthesized and characterized by UV-Vis diffuse reflectance absorption spectra (DRS) and X-ray photoelectron spectroscopy (XPS). The degradation of[C4Bth]PF6 could reach more than 99% within 120 min in the degradation catalyzed by Ag/TiO2. The photodegradation products of benzothiazole ILs are composed of inorganic substances or organic substances with simpler structures, which are easier to decompose and less toxic. The degradation system proposed by this study could provide a simple, green, safe, and economical method for the efficient treatment of benzothiazole ILs.
    Materials and Product Engineering
    Hollow MnO2/GNPs serving as a multiresponsive nanocarrier for controlled drug release
    Zheng Zhang, Yuanhui Ji, Wei Chen
    2020, 28(5):  1405-1414.  doi:10.1016/j.cjche.2019.12.013
    Abstract ( 320 )   PDF (3162KB) ( 148 )  
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    In this work, hollow manganese dioxide/gold nanoparticle (MnO2/GNPs) hybrid drug nanocarriers were prepared by coupling the gold nanoparticles (GNPs) with hollow structure manganese dioxide (MnO2). Among them, GNPs have been used as near-infrared (NIR)-responsive element for photothermal effect under NIR laser irradiation. The glutathione (GSH)-responsive and pH-responsive performances of drug release were derived from hollow MnO2. Particularly, Doxorubicin hydrochloride (DOX) can be loaded into hollow MnO2/GNPs with the drug loading efficiency up to 82.0%. Moreover, the photothermal effect and GSH-/pH-responsive properties of hollow MnO2/GNPs were investigated. The hollow MnO2/GNPs possessed satisfactory drug release efficiency (ca. 87.4% of loaded drug released in 12 h) and have high photothermal conversion efficiency, multiresponsive properties, and degradability. Finally, the kinetics of drug release was discussed in detail. Thus, our finding highlights that the multiresponsive nanocarriers are of great potential in the field of drug controlled release.
    Fabrication of poly(vinylidene fluoride) membrane via thermally induced phase separation using ionic liquid as green diluent
    Xiaozu Wang, Xiaogang Li, Juan Yue, Yangming Cheng, Ke Xu, Qian Wang, Fan Fan, Zhaohui Wang, Zhaoliang Cui
    2020, 28(5):  1415-1423.  doi:10.1016/j.cjche.2020.01.011
    Abstract ( 307 )   PDF (4048KB) ( 136 )  
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    Ionic liquid (IL), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6) as a new and environmentally friendly diluent was introduced to prepare poly(vinylidene fluoride) (PVDF) membranes via thermally induced phase separation (TIPS). Phase diagram of PVDF/[BMIM]PF6 was measured. The effects of polymer concentration and quenching temperature on the morphologies, properties, and performances of the PVDF membranes were investigated. When the polymer concentration was 15 wt%, the pure water flux of the fabricated membrane was up to nearly 2000 L·m-2·h-1, along with adequate mechanical strength. With the increasing of PVDF concentration and quenching temperature, mean pore size and water permeability of the membrane decreased. SEM results showed that PVDF membranes manufactured by ionic liquid (BMImPF6) presented spherulite structure. And the PVDF membranes were represented as β phase by XRD and FTIR characterization. It provides a new way to prepare PVDF membranes with piezoelectric properties.
    Weak base favoring the synthesis of highly ordered V-MCM-41 with well-dispersed vanadium and the catalytic performances on selective oxidation of benzyl alcohol
    Jing Zhao, Yifu Zhang, Lei Xu, Fuping Tian, Tao Hu, Changgong Meng
    2020, 28(5):  1424-1435.  doi:10.1016/j.cjche.2020.02.027
    Abstract ( 180 )   PDF (6695KB) ( 51 )  
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    The key to improve the performance of heteroatom catalysts is to ensure the orderliness of catalysts and the good dispersion of heteroatoms. The alkalinity plays the indispensable role in synthetic process of V-MCM-41 catalyst. The excessive alkalinity of synthetic system will make the MCM-41 difficult to crystallize, even to dissolve. It is easy to accumulate for heteroatomic species in the system of low alkalinity. Herein, the highly ordered VMCM-41 with high vanadic content in framework is synthesized in the condition of excessive NH3·H2O in this paper. A series of characterization results prove the good dispersion of vanadium species, and most of vanadium gets into the framework of MCM-41 with the states of tetravalence and pentavalence. Furthermore, the modified MCM-41 by other transition metals is successful synthesized by the method of V-MCM-41 in this paper. The VMCM-41 shows well catalytic activity for the selective oxidation of benzyl alcohol, which up to 74.83% for the conversion of benzyl alcohol and 96.20% for selectivity of benzaldehyde when initial V/Si=0.10. The paper provides the possibility for industrial application of V-MCM-41 in the oxidation of benzyl alcohol for benzaldehyde. Besides, the work provides a significant idea for the synthesis of modified MCM-41 by well-dispersed transition metals.
    Combined electronic/atomic level computational, surface (SEM/EDS), chemical and electrochemical studies of the mild steel surface by quinoxalines derivatives anti-corrosion properties in 1 mol·L-1 HCl solution
    F. Benhiba, Z. Benzekri, A. Guenbour, M. Tabyaoui, A. Bellaouchou, S. Boukhris, H. Oudda, I. Warad, A. Zarrouk
    2020, 28(5):  1436-1458.  doi:10.1016/j.cjche.2020.03.002
    Abstract ( 287 )   PDF (15795KB) ( 26 )  
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    This work is devoted to the study of the inhibition of corrosion of mild steel (MS) in molar hydrochloric acid (1 mol·L-1 HCl) by two named quinoxaline derivatives namely, 2-(2,4-dichlorophenyl)-1,4-dihydroquinoxaline (HQ) and 2-(2,4-dichlorophenyl)-6-methyl-1,4-dihydroquinoxaline (CQ). The inhibitory efficacy of HQ and CQ compounds is first evaluated using the gravimetric method and using electrochemical techniques (stationary and transient techniques). The results showed that our compounds are efficient corrosion inhibitors and the inhibition rates (ηEIS%) reached up to 91% and 94.2% at 10-3 mol·L-1 for HQ and CQ, respectively. The mentioned molecules are classified as mixed-type inhibitors. The adsorption of these inhibitors on the surface of steel in hydrochloric HCl 1 mol·L-1 medium obeys the Langmuir adsorption isotherm. The results of the scanning electron microscope (SEM) showed the formation of a protective film on the surface of the steel in the presence of the inhibitors studied. Elementary analysis is obtained by energy dispersive X-ray spectroscopy (EDS). The inhibition property was further elucidated by theoretical approaches such as:Density Functional Theory (DFT), quantum chemical descriptors (QCD), local reactive indices, solvent effect, theoretical complexation, Molecular Dynamic (MD) simulation, effect of temperature on adsorption energy (Eads), Radial Distribution Function (RDF), and Mean Square Displacement (MSD). The results of these approaches support the experimental results.
    The study on the mechanical properties of PU/MF double shell selfhealing microcapsules
    Guohao Du, Jianfeng Hu, Jianhui Zhou, Guangwu Wang, Shengli Guan, Hailing Liu, Man Geng, Chuang Lü, Yaoqiang Ming, Jinqing Qu
    2020, 28(5):  1459-1473.  doi:10.1016/j.cjche.2020.03.003
    Abstract ( 125 )   PDF (3987KB) ( 77 )  
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    The self-healing microcapsules can be buried in the coating to improve the anticorrosive ability. In this paper, self-healing microcapsules of polyurea (PU)/melamine resin (MF) double shell were prepared by in-situ polymerization and interfacial polymerization with isocyanate as the core material. Scanning electron microscope was used to observe the microcapsule morphology. The structures of microcapsules prepared with different chain extenders were characterized by Fourier transform infrared spectroscopy. The micromanipulation system was used to loading-holding, loading-unloading and loading to rupture individual microcapsules, so as to explore the mechanical properties of microcapsules. The Young's modulus corresponding to microcapsules was calculated by mathematical model fitting. The self-healing properties of microcapsule coating were characterized by optical microscope. The experimental results showed that the microcapsule shell prepared under optimized conditions had a complete morphology and good mechanical properties. The microcapsule was in the elastic deformation stage under small deformation, and the plastic deformation stage under large deformation. The Young's modulus range of microcapsules was 9.29-14.51 MPa, and the corresponding Young's modulus could be prepared by adjusting the process. The surface crack of the coating containing microcapsule could heal itself after 48 h in a humid environment.
    Preparation, characterization and antibacterial properties of cobalt doped titania nanomaterials
    Dai Shi, He Yang, Xiangxin Xue
    2020, 28(5):  1474-1482.  doi:10.1016/j.cjche.2020.03.017
    Abstract ( 131 )   PDF (20447KB) ( 26 )  
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    Cobalt-doped titania (Co-TiO2) nanomaterials were synthesized by the sol-gel method at different calcination temperatures. Using Escherichia coli (a), Staphylococcus aureus (b) and Candida albicans (c) as target strains, the antibacterial activity in visible light of the nanomaterials were studied. Co-TiO2 nanomaterials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectrum (FT-IR) and X-ray photoelectron spectroscopy (XPS). The Co ions in the Co-TiO2 nanomaterial exist in the form of CoTiO3 phase. The antibacterial properties of Co-TiO2 nanomaterials on E. coli (a), S. aureus (b) and C. albicans (c) were investigated with the oscillating flask method and the inhibition zone method. The nanomaterials calcined at 600℃ exhibit excellent antibacterial activity. The bacteriostatic rates for E. coli, S. aureus and C. albicans reached 99.5%, 91.3% and 93.4% respectively. The diameters of the antibacterial rings were up to 36 mm, 37 mm, 30 mm respectively, and the clarity of the ring was clear. The antibacterial properties of Co-TiO2 nanomaterials were compared with those of traditional silver sol, zinc oxide sol and Zn-doped TiO2 nanomaterials The mechanism of the influences of Co ions doping on the antibacterial activity of TiO2 nanomaterials was also discussed. The doping of Co ions inhibits the particle size of the antibacterial agent and extends the photocatalytic response range, thereby improving the photocatalytic performance of the antibacterial agent.