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Table of Content
28 April 2021, Volume 32 Issue 4
    A comprehensive review of the effect of different kinetic promoters on methane hydrate formation
    Ekta Chaturvedi, Sukumar Laik, Ajay Mandal
    2021, 32(4):  1-16.  doi:10.1016/j.cjche.2020.09.027
    Abstract ( 245 )   PDF (4247KB) ( 247 )  
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    Gas hydrates have recently emerged as a better alternative for the production, storage, and transportation of natural gases. However, factors like slow formation rate and limited storage capacity obstruct the possible industrial application of this technique. Different types of promoters and synergists have been developed that can improve the kinetics and storage capacity of gas hydrates. This review focuses on different kinetic promoters and synergists that can be utilized to enhance the storage capacity of hydrates. The main characteristics, structure and the possible limitations of the use of these promoters are likewise portrayed in detail. The relationship between structure and storage capacity of hydrates have also been discussed in the review. Current status of production of gas from hydrates, their restrictions, and future difficulties have additionally been addressed in the ensuing areas of the review.
    Fluid Dynamics and Transport Phenomena
    An experimental study on the choked flow characteristics of CO2 pipelines in various phases
    Yuxing Li, Shuaiwei Gu, Datong Zhang, Qihui Hu, Lin Teng, Cailin Wang
    2021, 32(4):  17-26.  doi:10.1016/j.cjche.2020.09.068
    Abstract ( 109 )   PDF (8035KB) ( 75 )  
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    High pressure pipeline transportation has been an established technology for economically transporting large amounts of CO2. However, there are still issues and associated risks that have to be effectively addressed and adequately understood. It is well known that a strong Joule-Thomson Cooling effect can occur when pressurized CO2 flows through a choke valve. Thus, to investigate the choking characteristics especially the temperature drop of high pressure CO2, a new laboratory scale experimental setup (total length of 14.85 m and the inner diameter of 15 mm) was constructed. Steady choked flow and transient choked flow tests were carried out respectively for pressurized CO2 in various initial phases. The phase transitions and temperature drop characteristics were then studied following the choked flow and the results show that the phase transitions in steady choked flow differs significantly from that in transient choked flow. For transient choked flow of various initial phases, all the flows downstream would transfer from single phase to gas-liquid two-phase flow. Furthermore, the effect of water on transient choked flow of supercritical CO2 pipeline was investigated, and the phenomena of solid particles deposition was captured which was paramount importance of ensuring the safety operation of CO2 pipelines when throttling by the choke valves.
    Hydrothermal and entropy generation specifications of a hybrid ferronanofluid in microchannel heat sink embedded in CPUs
    Amin Shahsavar, Majid Jafari, Pouyan Talebizadehsardari, Davood Toghraie
    2021, 32(4):  27-38.  doi:10.1016/j.cjche.2020.08.053
    Abstract ( 73 )   PDF (17768KB) ( 33 )  
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    The objective of this numerical work is to evaluate the first law and second law performances of a hybrid nanofluid flowing through a liquid-cooled microchannel heatsink. The water-based hybrid nanofluid includes the Fe3O4 and carbon nanotubes (CNTs) nanoparticles. The heatsink includes a microchannel configuration for the flow field to gain heat from a processor placed on the bottom of the heatsink. The effects of Fe3O4 concentration (φFe3O4), CNT concentration (φCNT) and Reynolds number (Re) on the convective heat transfer coefficient, CPU surface temperature, thermal resistance, pumping power, as well as the rate of entropy generation due to the heat transfer and fluid friction is examined. The results indicated higher values of convective heat transfer coefficient, pumping power, and frictional entropy generation rate for higher values of Re, φFe3O4 and φCNT. By increasing Re, φFe3O4 and φCNT, the CPU surface temperature and the thermal resistance decrease, and the temperature distribution at the CPU surface became more uniform. To achieve the maximum performance of the studied heatsink, applying the hybrid nanofluid with low φFe3O4 and φCNT was suggested, while the minimum entropy generation was achieved with the application of nanofluid with high φFe3O4 and φCNT.
    Experimental and Numerical Study of Gas-Liquid Flow in a Sectionalized External-Loop Airlift Reactor
    Shivanand M. Teli, Channamallikarjun S. Mathpati
    2021, 32(4):  39-60.  doi:10.1016/j.cjche.2020.10.023
    Abstract ( 82 )   PDF (20195KB) ( 41 )  
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    The external loop airlift reactor (EL-ALR) is widely used for gas-liquid reactions. It's advantage of good heat and mass transfer rates compared to conventional bubble column reactors. In the case of fermentation application where a medium is highly viscous and coalescing in nature, internal in riser helps in the improvement of the interfacial area as well as in the reduction of liquid-phase back mixing. The computational fluid dynamic (CFD) as a tool is used to design and scale-up of sectionalized external loop airlift reactor. The present work deals with computational fluid dynamics (CFD) techniques and experimental measurement of a gas hold-up, liquid circulation velocity, liquid axial velocity, Sauter mean bubble diameter over a broad range of superficial gas velocity 0.0024 ≤ UG ≤ 0.0168 m·s-1. The correlation has been made for bubble size distribution with specific power consumption for different plate configurations. The effects of an internal on different mass transfer models have been completed to assess their suitability. The predicted local mass transfer coefficient has been found higher in the sectionalized external loop airlift reactor than the conventional EL-ALR.
    Numerical simulation of heavy fuel oil atomization using a pulsed pressure-swirl injector
    S. M. A. Najafi, P. Mikaniki, H. Ghassemi
    2021, 32(4):  61-69.  doi:10.1016/j.cjche.2020.07.053
    Abstract ( 77 )   PDF (9821KB) ( 33 )  
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    It is known that increasing the injection pressure reduces the breakup length and the droplet size. Adding pulses, on the other hand, helps to atomize the liquid into finer droplets, similar to air-assisted injectors but without altering the air-to-fuel concentration.
    To further reduce the droplet size and breakup length, a novel injector type, called "Pulsed Pressure-Swirl" (PPS), is introduced in this work, which is a combination of pressure-swirl and ultrasonic pulsed injectors. A pressure-swirl atomizer was designed and fabricated specifically for Mazut HFO (Heavy Fuel Oil). The droplet formation process and droplet size distribution have been studied experimentally (by shadowgraphy high speed imaging) and numerically (with the open-source Volume-of-Fluid code Gerris).
    Changing liquid injection pressure effect on the spray angle and film thickness has been quantified. These simulations have been used to study the primary breakup process and quantify the droplet size distributions, using different injection pulse frequencies and pressures.
    The numerical results have revealed that the new injector concept successfully produces finer droplets and results in a decrease in the breakup length, especially when applying high pulse frequencies, with no significant changes in the spray angle.
    Experimental research on steady-state operation characteristics of gas-solid flow in a 15.5 m dual circulating fluidized bed system
    Yangjun Wei, Leming Cheng, Erdong Wu, Liyao Li
    2021, 32(4):  70-76.  doi:10.1016/j.cjche.2020.10.013
    Abstract ( 72 )   PDF (6358KB) ( 106 )  
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    Gas-solid hydrodynamic steady-state operation is the operating basis in a chemical looping dual-reactor system. This study reported the experimental results on the steady-state operation characteristics of gas-solid flow in a 15.5 m high dual circulating fluidized bed (CFB) cold test system. The effects of superficial gas velocity, static bed material height and solid returning modes on the steady-state operation characteristics between the two CFBs were investigated. Results suggest that the solid distributions in the dual CFB test system was mainly determined by the superficial gas velocity and larger solid inventory may help to improve the solid distributions. Besides, cross-returning mode coupled with self-returning is good for steady-state running in the dual-reactor test system.
    Thermal performance assessment of self-rotating twisted tapes and Al2O3 nanoparticle in a circular pipe
    Chuanshuai Dong, Lin Lu, Tao Wen, Shaojie Zhang
    2021, 32(4):  77-86.  doi:10.1016/j.cjche.2020.10.045
    Abstract ( 69 )   PDF (8715KB) ( 13 )  
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    In view of the practical importance of the heat transfer devices in various thermal engineering fields including chemical and nuclear engineering, this study aims at developing an effective method of heat transfer enhancement by using self-rotating twisted tapes (SRTTs) and Al2O3 nanoparticles. The effect of the self-rotating twisted tapes and Al2O3 nanoparticles on the thermal performance was comprehensively investigated in a circular pipe. The experimental results indicated the heat transfer rate was effectively improved by SRTTs in comparison of plain tube. In addition, the heat transfer multiplier with SRTTs decreased from 1.38 to 1.08 with the Reynolds number increasing from 19,322 to 64,407, while the friction factor multiplier decreased from 1.61 to 1.32. Besides, the results indicated that the employment of Al2O3 nanoparticles and SRTTs demonstrated superior thermal performance to the single SRTTs. As Reynolds number increases from 19,322 to 64,407, the heat transfer multiplier decreased from 2.08 to 1.18 in the mass concentration of 3.0% and from 1.38 to 1.08 in mass concentration of 0.0%. Finally, the new heat transfer and friction factor correlations considering the combined effect of Al2O3 nanoparticle and SRTTs were developed within 10% deviation of experimental values.
    Time-series analysis of the characteristic pressure fluctuations in a conical fluidized bed with negative pressure
    Sheng Fang, Yanding Wei, Lei Fu, Geng Tian, Haibin Qu
    2021, 32(4):  87-99.  doi:10.1016/j.cjche.2020.09.042
    Abstract ( 71 )   PDF (1615KB) ( 47 )  
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    The negative pressure conical fluidized bed is widely used in the pharmaceutical industry. In this study, experiments based on the negative pressure conical fluidized bed are carried out by changing the material mass and particle size. The pressure fluctuation signals are analyzed by the time and the frequency domain methods. A method for absolutely characterizing the degree of the energy concentration at the main frequency is proposed, where the calculation is to divide the original power spectrum by the average signal power. A phenomenon where the gas velocity curve temporarily stops growing is observed when the material mass is light, and the particle size is small. The standard deviation and kurtosis both rapidly change at the minimum fluidization velocity and thus can be used to determine the flow regime, and the variation rule of the kurtosis is independent of both the material mass and particle size. In the initial fluidization stage, the dominant pressure signal comes from the material movement; with the increase in the gas velocity, the power of a 2.5 Hz signal continues to increase. A method of dividing the main frequency by the average cycle frequency can conveniently determine the fluidized state, and a novel concept called stable fluidized zone proposed in this paper can be obtained. Controlling the gas velocity within the stable fluidized zone ensures that the fluidized bed consistently remains in a stable fluidized state.
    Adopting inclined channel to decline the salinity mixing for rotary energy recovery device: Simulation and optimization
    Wenjie Li, Yue Wang, Jie Zhou, Xiaoyu Qiao, Shichang Xu
    2021, 32(4):  100-107.  doi:10.1016/j.cjche.2020.09.069
    Abstract ( 59 )   PDF (6600KB) ( 57 )  
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    After years of research, the energy efficiency of energy recovery device has been raised to a high level, but the salinity mixing has not been effectively improved. Mixing will lead to a rise of high-pressure seawater salinity, which will increase the operating cost. In this paper, the computational fluid dynamics (CFD) simulation of the rotary energy recovery device (RERD) is carried out. It is found that the unstable flow caused by the non-parallel between the channel and the flow direction of fluid is an important reason for mixing. After the inclined channel structure is adopted, the non-parallel problem is improved. The formation of unstable flow is effectively controlled. Under the commercial product operating conditions, the volumetric mixing of the optimized device is reduced from 3.34% to 1.29%, showing the effectiveness of the structure.
    A numerical study of accelerated moderate or intense low-oxygen dilution (MILD) combustion stability for methane in a lab-scale furnace by off-stoichiometric combustion technology
    Mengqian Xie, Fangqin Dai, Yaojie Tu
    2021, 32(4):  108-118.  doi:10.1016/j.cjche.2020.09.053
    Abstract ( 72 )   PDF (4044KB) ( 63 )  
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    Moderate or intense low-oxygen dilution (MILD) combustion has become a promising low-NOX emission technology, while the delayed mixing of reactants and slower oxidation rate could potentially cause ignition instability in some scenarios. This paper proposes a new idea for enhancing the ignition stability for methane MILD combustion by combining with off-stoichiometric combustion (OSC), and its performances have been numerically assessed through a comparison against the original MILD combustion burner. The results reveal although non-premixed pattern has the lowest NO emission, it suffers from a larger liftoff distance, thus less ignition stability. Contrarily, both partially-premixed and fully premixed patterns exhibit excellent ignition stability. Among the considered OSC conditions, the pattern of Inner ultra-rich and Outer lean produces the lowest NO emission while maintains a high ignition stability. Furthermore, the enhancement of the combustion stability by implementing OSC to the original MILD combustion burner is shown by comparing the operational range of furnace wall temperature (Tf), CO and NO emissions, as well as the evolution of chemical flame. The comparison reveals that OSC can extend the lowest operational Tf from 900 K to 800 K. More importantly, OSC can significantly improve the ignition stability in the whole range of Tf as compared to the original MILD combustion burner.
    A level set based immersed boundary method for simulation of non-isothermal viscoelastic melt filling process
    Qiang Li, Fangcao Qu
    2021, 32(4):  119-133.  doi:10.1016/j.cjche.2020.09.057
    Abstract ( 76 )   PDF (17214KB) ( 164 )  
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    In this work, the polymer melt filling process is simulated by using a coupled finite volume and level-set based immersed boundary (LS-IB) method. Firstly, based on a shape level set (LS) function to represent the mold boundary, a LS-IB method is developed to model the complex mold walls. Then the nonisothermal melt filling process is simulated based on non-Newtonian viscoelastic equations with different Reynolds numbers in a circular cavity with a solid core, and the effects of Reynolds number on the flow patterns of polymer melt are presented and compared with each other. And then for a true polymer melt with a small Reynolds number that varies with melt viscosity, the moving interface, the temperature distributions and the molecular deformation are shown and analyzed in detail. At last, as a commonly used application case, a socket cavity with seven inserts is investigated. The corresponding physical quantities, such as the melt velocity, molecular deformation, normal stresses, first normal stress difference, temperature distributions and frozen layer are analyzed and discussed. The results could provide some predictions and guidance for the polymer processing industry.
    Separation Science and Engineering
    Experimental study on sand particles accumulation, migration and separation efficiency in slug catcher
    Xianchao Liang, Limin He, Xiaoming Luo, Qingping Li, Yuanpeng You, Yiqiu Xu
    2021, 32(4):  134-143.  doi:10.1016/j.cjche.2020.09.059
    Abstract ( 65 )   PDF (6572KB) ( 59 )  
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    Sand production often leads to the failure of production equipment on offshore platform. Therefore, a new idea has been put forward, which is installing cyclone or baffle in the internal of the slug catcher for better sand control. In this paper, an experimental study is presented, which mainly includes sand particles accumulation shape, migration law and separation performance. The results suggest that the accumulation area is mainly divided into two zones:the crowded settlement zone and the free settlement zone. The crowded settlement zone has a special shape, which can be characterized by two parameters:accumulation length and accumulation angle. Axial sampling analysis shows obvious particle classification. Median particle size decreases with the increase of the axial distance, and the range of particle size distribution narrows gradually. The separation experiment shows that the gas velocity has the greatest influence on the separation efficiency. When the gas velocity is 14 m·s-1, the separation efficiency drops sharply, which can be abated by installing cyclone separator. In addition, the separation efficiency tends to be a constant under different gas velocities by installing baffle with appropriate height. Then the effectiveness and rationality of installing internal components can be strongly proved. All these provide important guidance for maximizing the sand control function of the slug catcher.
    Simultaneously spray-assisted assembling reversible superwetting coatings for oil-water separation
    Dexin Chen, Zhixin Kang, Wei Li, Fenghua Su
    2021, 32(4):  144-150.  doi:10.1016/j.cjche.2020.07.033
    Abstract ( 69 )   PDF (3831KB) ( 50 )  
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    Here, superhydrophobic cuprous oxide (Cu2O) with hierarchical micro/nanosized structures was synthesized via spray-assisted layer by layer assembling. The as-prepared superhydrophobic meshes with high contact angle (159.6°) and low sliding angle (1°) are covered with Cu2O "coral reef" -like micro/nanosized structures. Interestingly, the superhydrophobic mesh surfaces became superhydrophilic again due to the oxidization of Cu2O to CuO by annealing at a higher temperature (300℃). And the superhydrophobic properties would be recovered by heating at 120℃. Furthermore, the superwetting meshes were applied to design a miniature device to separate light or heavy oil from the water-oil mixtures with excellent separation efficiency. These superwetting surfaces by simultaneously spray-assisted layer by layer assembling technique show the potential application in universal oil-water separation.
    Static and dynamic studies of adsorption by four macroporous resins to enrich oridonin from Rabdosia rubescens
    Ling Meng, Xia Gui, Zhi Yun
    2021, 32(4):  151-158.  doi:10.1016/j.cjche.2020.08.030
    Abstract ( 65 )   PDF (3097KB) ( 56 )  
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    Oridonin, one of the active ingredients in Rabdosia rubescens (R. rubescens), has been reported to induce cell apoptosis and cell cycle arrest in many cancers. Conventional extraction methods tend to result in unsatisfied enrichment and poor quality of oridonin present in a given biomass. This paper aims to evaluate the performance and separation characteristics of four different macroporous resins to arrive at the most suitable methodology for the isolation and purification of high-quality oridonin. Static absorption kinetics, thermodynamic and dynamic adsorption were evaluated. HP-20 was selected for further study due to its high adsorption capacity of 32 mg·g-1 and desorption ratio with 98.5%. The pseudo-secondorder model was considered to be the most suitable for kinetic results, and Langmuir model was chosen to better describe the absorption thermodynamics. Under optimum conditions (flow rate of 4 ml·min-1, bed depth with 6 cm and initial concentration of 2.15 mg·ml-1), the effective content of oridonin increased from 33.9% to 79.1% in the dry extract with a recovery of 81% and the purity of oridonin improved from 76% to 93%. The results confirm that HP-20 provides an efficient method to purify most oridonin from R. rubescens.
    Catalysis, Kinetics and Reaction Engineering
    Catalytic ozonation of volatile organic compounds (ethyl acetate) at normal temperature
    Jiahao Cui, Shejiang Liu, Hua Xue, Xianqin Wang, Ziquan Hao, Rui Liu, Wei Shang, Dan Zhao, Hui Ding
    2021, 32(4):  159-167.  doi:10.1016/j.cjche.2020.09.021
    Abstract ( 57 )   PDF (10256KB) ( 36 )  
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    Catalytic treatments of VOCs at normal temperature can greatly reduce the cost and temperature of processing, and improve the safety factor in line with the requirements of green chemistry. Activated carbon fiber (ACF) was pretreated with 10% H2SO4 by single factor optimization to increase specific surface area and pore volume obviously. The catalytic ozonation performance of ACF loaded with Au, Ag, Pt and Pd noble metals on ethyl acetate was investigated and Pd/ACF was selected as the optimal catalyst which had certain stability. Pd is uniformly distributed on the surface of ACF, and Palladium mainly exists in the form of Pd0 with a amount of Pd+2. The specific surface area of the catalysts gradually decreases as the loading increases. The activation energy of ethyl acetate calculated by Arrhenius equation is 113 kJ·mol-1. With 1% Pd loading and the concentration ratio of ozone to ethyl acetate is 3:1, catalytic ozonation performance is maximized and the conversion rate of ethyl acetate reached to 60% in 30-50℃ at 15,000-30,000 h-1.
    One-step synthesis of Ni@Pd/NH2-Fe3O4 nanoparticles as affordable catalyst for formic acid dehydrogenation
    Mohammad Reza Nabid, Yasamin Bide, Mahsa Jafari
    2021, 32(4):  168-174.  doi:10.1016/j.cjche.2020.07.067
    Abstract ( 64 )   PDF (10706KB) ( 19 )  
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    Currently, one of the critical issues in the world is finding an appropriate green alternative to fossil fuels due to the concerns about global warming. As a hydrogen source, formic acid has been given particular attention owing to the attractive features such as high-energy density, no toxicity, high stability at ambient temperature and high hydrogen content. Introducing an affordable and highly efficient catalyst with easy recovery from the reaction mixture for selective dehydrogenation of formic acid is still demanding. In this report, we used a simple one-step process to synthesize Ni@Pd core shell nanoparticles on 3-aminopropyltriethoxysilane modified Fe3O4 nanoparticles. The existence of Ni and Pd results in a synergic effect on the catalytic activity. The -NH2 groups play an important role for obtaining well-dispersed ultrafine particles with high surface area and active sites. In addition, Fe3O4 lead to convenient magnetic recovery of the catalyst from reaction mixture. Our results indicate that the as-prepared catalyst give the superb turnover frequency of 5367.8 h-1 with no additive, which is higher than most of the previously reported catalysts.
    Controllable synthesis of polyoxymethylene dimethyl ethers by ionic liquids encapsulated in mesoporous SBA-16
    Chaofeng Zhang, Tonglu Zhang, Jing Zhang, Jiandong Zhang, Ruifeng Li
    2021, 32(4):  175-182.  doi:10.1016/j.cjche.2020.09.016
    Abstract ( 65 )   PDF (1942KB) ( 65 )  
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    The promising combustion and emission properties of polyoxymethylene dimethyl ethers (PODEn) are of significant interest. However, the synthesis of PODEn products with desired chain lengths is still a problem facing synthetic PODEn. Herein, a series of unique IL@SBA-16-Cx solid catalysts are prepared by encapsulation of ionic liquids (ILs) within the nanocage of SBA-16 through a silylation method. The structure of the encapsulated catalyst was characterized by UV-vis spectra, Fourier transform infrared (FT-IR), N2 adsorption-desorption isotherms, Powder X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Elemental analysis. The encapsulated catalysts show similar catalytic activity to the homogeneous counterparts and display higher selectivity to the targeted PODE3-5 products than their homogeneous counterparts in the synthesis of PODEn from methanol (MeOH) and trioxymethylene (TOM). The encapsulated catalysts exhibit a superior PODE3-5 selectivity and could be the promising catalysts for PODE n synthetic reaction.
    Kinetic degradation of amoxicillin by using the electro-Fenton process in the presence of a graphite rods from used batteries
    Hakima Kadji, Idris Yahiaoui, Zehira Garti, Abdeltif Amrane, Farida Aissani-Benissad
    2021, 32(4):  183-190.  doi:10.1016/j.cjche.2020.08.032
    Abstract ( 59 )   PDF (3318KB) ( 73 )  
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    This study reports the removal of amoxicillin (AMX) in aqueous media using the electro-Fenton process in the presence of a graphite cathode recovered from used batteries. The impact of the relevant parameters on the electro-Fenton process, namely the applied current intensity, the temperature, the initial concentration of AMX and the initial concentration of ferrous ions were investigated. The results showed that the optimal values were:I=600 mA, T=25℃,[AMX]0=0.082 mmol·L-1 and[Fe2+]=1 mmol·L-1, leading to 95% degradation and 74% mineralization. The model parameters of AMX mineralization were determined using nonlinear methods, showing that it follows a pseudo-second-order kinetic. The Energy consumption (EC) calculated under the optimal values was found to be 0.79 kW·h·g-1, which was of the same order of magnitude of those reported in other findings; while it is noteworthy that the electrodes used in our study are of a lower cost.
    Electrochemical oxidation of Rhodamine B with cerium and sodium dodecyl benzene sulfonate co-modified Ti/PbO2 electrodes: Preparation, characterization, optimization, application
    Zhen Wei, Xuanqi Kang, Shangyuan Xu, Xiaokang Zhou, Bo Jia, Qing Feng
    2021, 32(4):  191-202.  doi:10.1016/j.cjche.2020.09.044
    Abstract ( 81 )   PDF (18006KB) ( 29 )  
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    Regulation of the electronic structure and interface property becomes a major strategy in the preparation of electro-catalyst. This paper reports the synthesis of cerium (Ce) and sodium dodecyl benzene sulfonate (SDBS) co-modified Ti/PbO2 electrodes (Ti/PbO2-Ce-SDBS). Ce and SDBS could greatly change the electronic structure and interface property of PbO2. Ti/PbO2-Ce-SDBS exhibited excellent electrocatalytic activity and stability in Rhodamine B (RhB) electrocatalytic oxidation reaction. The improved electrocatalytic activity associates with the synergistic effect of electronic and interface factors. In the electrochemical degradation of RhB, the removal efficiencies of RhB and COD are about 0.880 and 0.694 respectively after the electrolysis of 220 min with Ti/PbO2-Ce-4-SDBS-40, which are higher than the contrast Ti/PbO2 electrodes. In the meantime, the accelerated lifetime of Ti/PbO2-Ce-4-SDBS-40 is more than 6.2 times than that of Ti/PbO2.
    Dehydrogenation of isobutane to isobutene over a Pt-Cu bimetallic catalyst in the presence of LaAlO3 perovskite
    Yanyong Li, Meng Ge, Jiameng Wang, Mengquan Guo, Fanji Liu, Mingxun Han, Yanhong Xu, Lihong Zhang
    2021, 32(4):  203-211.  doi:10.1016/j.cjche.2020.07.027
    Abstract ( 73 )   PDF (3284KB) ( 52 )  
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    In this study, isobutane dehydrogenation to isobutene reaction was carried out in a series of Pt-Cu bimetallic catalysts prepared by co-impregnation method. The catalysts were characterized by means of several techniques, including XRD, N2 adsorption-desorption, TEM, XPS, H2-TPR and TG. The results show that the existence of LaAlO3 perovskite can enhance the dispersion and sintering resistance of metal nanoparticles and facilitate the transfer of carbon deposits from active sites to the support. Interestingly, the perovskite nanoparticles can also inhibit the reduction of CuOx and the formation of PtCu alloys, resulting in the suitable interaction between Pt and Cu. The Pt-Cu/LaAlO3/SiO2 catalyst exhibits the optimal dehydrogenation performance with an isobutane conversion of 47% and isobutene selectivity of 92% after 310 min reaction, which was ascribed to the unique role of LaAlO3 perovskite as well as the appropriate Pt-Cu interaction.
    2-Hydroxy-1, 4-napthoquinone solubilization, thermodynamics and adsorption kinetics with surfactant
    Zoya Zaheer, Ekram Yousif Danish, Samia A. Kosa
    2021, 32(4):  212-223.  doi:10.1016/j.cjche.2020.09.064
    Abstract ( 68 )   PDF (1640KB) ( 97 )  
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    2-Hydroxy-1, 4-napthoquinone (lawsone) natural red-orange dye was extracted from fresh henna (Lawsonia inermis) leaves in an alkaline media. The lawsone-surfactant solubilization constants (KLS) were calculated for the first time by using cationic cetyltrimethylammonium bromide (CTAB) and anionic sodium dodecyl sulphate (SDS). The standard free energy, concentration of solubilized lawsone and number of lawsone molecules solubilized into micelles were calculated and discussed. Surface excess, minimum surface area per molecule, surface pressure, free energy (adsorption and aggregation) and equilibrium constants of different states were determined from tensiometry. Different metal ions (Ag+, Co2+, Cu2+, Ni2+, Fe3+, Zn2+ and Al3+) were used to determine the complex forming ability with lawsone. Out of these, Ag+ ions have strong binding capacity with lawsone. The adsorption of lawsone on the surface of glass with silver ions in presence of CTAB was also observed at pH ≥ 9.0. The pseudo-first, secondorder kinetic equation, intraparticles diffusion and Elovich models were used to determine the kinetics of lawsone adsorption onto the surface of glass and a probable mechanism has been discussed. Lawsone adsorption followed second-order kinetic equation (k2=0.019 g·mg-1·min-1).
    Effect of preparation methods on the hydrocracking performance of NiMo/Al2O3 catalysts
    Jiake Yang, Tongjiu Zuo, Jiangyin Lu
    2021, 32(4):  224-230.  doi:10.1016/j.cjche.2020.06.009
    Abstract ( 48 )   PDF (1861KB) ( 42 )  
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    In this work, NiMo catalysts with various contents of MoO3 were prepared through incipient wetness impregnation by a two-step method (NM-xA) and one-pot method (NM-xB). The catalysts were then characterized by XRD, XPS, NH3-TPD, H2-TPR, HR-TEM, and N2 adsorption-desorption technologies. The performance of the NiMo/Al2O3 catalysts was investigated by hydrocracking low-temperature coal tar. When the MoO3 content was 15 wt%, the interaction between Ni species and Al2O3 on the NM-15B catalyst was stronger than that on the NM-15A catalyst, resulting in the poor performance of the former. When the MoO3 content was 20 wt%, MoO3 agglomerated on the surface of the NM-20A catalyst, leading to decreased number of active sites and specific surface area and reduced catalytic performance. The increase in the number of MoS2 stack layers strengthened the interaction between Ni and Mo species of the NM-20B catalyst and consequently improved its catalytic performance. When the MoO3 content reached 25 wt%, the active metals agglomerated on the surface of the NiMo catalysts, thereby directly decreasing the number of active sites. In conclusion, the two-step method is suitable for preparing catalysts with large pore diameter and low MoO3 content loading, and the one-pot method is more appropriate for preparing catalysts with large specific surface area and high MoO3 content. Moreover, the NM-xA catalysts had larger average pore diameter than the NM-xB catalysts and exhibited improved desulfurization performance.
    Selective catalytic reduction failure of low NH3-NOx ratio
    Piqiang Tan, Xiaoyu Li, Shiyan Wang, Zhiyuan Hu, Diming Lou
    2021, 32(4):  231-240.  doi:10.1016/j.cjche.2020.07.055
    Abstract ( 71 )   PDF (2142KB) ( 139 )  
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    An insufficient amount of NH3 (ammonia) will reduce the conversion efficiency of NOx, which may lead to excess NOx emissions, resulting in NH3-SCR failure. In this article, SCR failure caused by a low NH3-NOx ratio is studied systematically by experiments. The main reasons for a low NH3-NOx ratio in SCR include insufficient urea injection, hydrothermal aging of catalysts and urea crystallization. It was found from an insufficient urea injection experiment that with the increase of NH3-NOx ratio, the NOx conversion efficiency of the SCR system increased, but the ammonia leakage also increased. The main influencing factors of NOx conversion efficiency are different under different NH3-NOx ratios. A flow reactor system was used in the catalyst hydrothermal aging experiment to investigate the effect of hydrothermal aging on catalyst activity. After a 24 h hydrothermal aging experiment at 800℃, the NOx conversion efficiency of the copper-based zeolite catalysts decreased significantly at the boundary of medium and low temperature regions. And the NO2-NOx ratio in the mixture had a significant effect on the catalytic performance. Thermogravimetry coupled to Fourier transform infrared spectroscopy (TG-FTIR) was used to analyze the composition of urea deposits in a urea deposits analysis experiment. It was found that the main components of urea deposits were urea and isocyanic acid (HNCO). Preventing HNCO polymerization, especially the formation of CYA, can decrease the formation of urea deposits.
    Process Systems Engineering and Process Safety
    Numerical investigation of granular mixing in an intensive mixer: Effect of process and structural parameters on mixing performance and power consumption
    Zhijian Zuo, Shuguang Gong, Guilan Xie
    2021, 32(4):  241-252.  doi:10.1016/j.cjche.2020.10.036
    Abstract ( 48 )   PDF (14967KB) ( 8 )  
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    Discrete element method (DEM) simulations of particle mixing process in an intensive mixer were conducted to study the influence of structural and process parameters on the mixing performance and power consumption. The DEM model was verified by comparing the impeller torque obtained from simulation with that from experiment. Impeller and vessel torque, coordination number (CN) and mixing index (Relative standard deviation) were adopted to qualify the particle dynamics and mixing performance with different parameters. A method based on cubic polynomial fitting was proposed to determine the critical mixing time and critical specific input work during the mixing process. It is found that the mixing performance and energy efficiency increases with the decrease of impeller offset. The mixing performance is improved slightly with the increase of blade number and the impeller with 3 blades has the highest energy efficiency due to its low input torque. Results indicate that the energy efficiency and the mixing performance increase with the decrease of filling level when the height of granular bed is higher than that of blade.
    Pore plugging effects on the performance of ZSM-5 catalyst in MTP reaction using a discrete model
    Yudong Shen, Hao Liang, Zuwei Liao, Binbo Jiang, Jingdai Wang, Yongrong Yang, Minggang Li, Yibin Luo, Xingtian Shu
    2021, 32(4):  253-263.  doi:10.1016/j.cjche.2020.10.038
    Abstract ( 60 )   PDF (6083KB) ( 85 )  
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    Coke is an important medium for connecting reaction and regeneration of the methanol to propylene process on the ZSM-5 catalyst. Coke grows in the meso and macro pores, it gradually worsens the diffusion inside the catalyst particle. Furthermore, pore plugging is inevitable which causes the deactivation of ZSM-5 catalyst. However, current continuum model cannot reflect the changes in pore structure with clear physical concepts. A discrete model that is verified by the carbon deposition experiments is introduced to indicate the behavior of pore plugging effects. Results show that the pore plugging has a significant effect on the performance of the catalyst. The time varying profile of effectiveness factor is obtained, indicating a regular reduction with the increase of the pore plugging effect. Spatial distributions of pore size that would significantly enhance the plugging effect are also identified.
    Vacuum pressure swing adsorption process for coalbed methane enrichment
    Bo Lu, Yuanhui Shen, Zhongli Tang, Donghui Zhang, Gaofei Chen
    2021, 32(4):  264-280.  doi:10.1016/j.cjche.2020.08.043
    Abstract ( 43 )   PDF (4003KB) ( 86 )  
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    The enrichment of low concentration coalbed methane using adsorption process with activated carbon adsorbent was studied in this work. Adsorption isotherms of methane, nitrogen and carbon dioxide on activated carbon were measured by volumetric method, meanwhile a series of breakthrough tests with single component, binary components and three components feed mixture has been performed for exploring dynamic adsorption behaviors. Moreover, a rigorous mathematical model of adsorption bed containing mass, energy, and momentum conservation equation as well as dual-site Langmuir model with the Linear driving force model for gas-solid phase mass transfer has been proposed for numerical modeling and simulation of fixed bed breakthrough process and vacuum pressure swing adsorption process. Furthermore, the lumped mass transfer coefficient of methane, nitrogen and carbon dioxide on activated carbon adsorbent has been determined to be 0.3 s-1, 1.0 s-1 and 0.06 s-1 by fitting the breakthrough curves using numerical calculation. Additionally, a six bed VPSA process with twelve step cycle sequence has been proposed and investigated for low concentration coalbed methane enrichment. Results demonstrated that the methane molar fraction in feed mixture ranged from 10% to 50% could be enriched to 32.15% to 88.75% methane in heavy product gas with a methane recovery higher than 83% under the adsorption pressure of 3 bar (1 bar=105 Pa) and desorption pressure of 0.1 bar. Energy consumption of this VPSA process was varied from 0.165 kW·h·m-3 CH4 to 0.649 kW·h·m-3 CH4. Finally, a dual-stage VPSA process has been successfully developed to upgrade a low concentration coalbed methane containing 20% methane to a target product gas with methane purity higher than 90%, meanwhile the total methane recovery was up to 98.71% with a total energy consumption of 0.504 kW·h·m-3 CH4.
    Chemical Engineering Thermodynamics
    High surface area and mesoporous activated carbon from KOH-activated dragon fruit peels for methylene blue dye adsorption: Optimization and mechanism study
    Ali H. Jawad, Ahmed Saud Abdulhameed, Lee D. Wilson, Syed Shatir A. Syed-Hassan, Zeid A. ALOthman, Mohammad Rizwan Khan
    2021, 32(4):  281-290.  doi:10.1016/j.cjche.2020.09.070
    Abstract ( 121 )   PDF (5366KB) ( 437 )  
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    In this study, an alternative precursor for production of activated carbon was introduced using dragon fruit (Hylocereus costaricensis) peel (DFP). Moreover, KOH was used as a chemical activator in the thermal carbonization process to convert DFP into activated carbon (DFPAC). In order to accomplish this research, several approaches were employed to examine the elemental composition, surface properties, amorphous and crystalline nature, essential active group, and surface morphology of the DFPAC. The Brunauer-Emmett-Teller test demonstrated a mesoporous structure of the DFPAC has a high surface area of 756.3 m2·g-1. The cationic dye Methylene Blue (MB) was used as a probe to assess the efficiency of DFPAC towards the removal of MB dye from aqueous solution. The effects of adsorption input factors (e.g. DFPAC dose (A:0.04-0.12 g·g-1), pH (B:3-10), and temperature (C:30-50℃)) were investigated and optimized using statistical analysis (i.e. Box-Behnken design (BBD)). The adsorption kinetic model can be best categorized as the pseudo-first order (PFO). Whereas, the adsorption isotherm model can be best described by Langmuir model, with maximum adsorption capacity of DFPAC for MB dye was 195.2 mg·g-1 at 50℃. The adsorption mechanism of MB by DFPAC surface was attributed to the electrostatic interaction, p-p interaction, and H-bonding. Finally, the results support the ability of DFP to be a promising precursor for production of highly porous activated carbon suitable for removal of cationic dyes (e.g. MB).
    Experimental results for the vapor-liquid equilibria of (formaldehyde + 1,3,5-trioxane + methanol + salt + water) systems and comparison with predictions
    Xianming Zhang, Mengchen Li, Yufeng Hu, Zhichang Liu, Shuqin Mo
    2021, 32(4):  291-300.  doi:10.1016/j.cjche.2020.11.019
    Abstract ( 56 )   PDF (722KB) ( 39 )  
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    The salt effect on the vapor-liquid phase equilibrium (VLE) of solvent mixtures is of significant interest in the industrial production of 1,3,5-trioxane. Experimental data for the VLE of quinary systems (formaldehyde + 1,3,5-trioxane + methanol + salt + water) and their ternary subsystems (formaldehyde + salt + water), (1,3,5-trioxane + salt + water), and (methanol + salt + water) were systematic measured under atmospheric pressure. The salts considered included KBr, NaNO3, and CaCl2. The extended UNIFAC model was used to describe the VLE of the salt-containing reactive mixtures. The model parameters were determined from the experimental VLE data of ternary systems or obtained from the literature, and then were used to predict the VLE of systems (1,3,5-trioxane + KBr + water), (methanol + KBr + water), (formaldehyde + KBr + water), and (formaldehyde + 1,3,5-trioxane + methanol + salt + water) with salt=KBr, NaNO3, and CaCl2. The predicted results showed good agreements with the measured results. Furthermore, the model was used to uncover the salt effect on the VLE of these multisolvent reactive systems.
    Biotechnology and Bioengineering
    Tailoring polymeric composite gel beads-encapsulated microorganism for efficient degradation of phenolic compounds
    Xueping Liu, Ping Xue, Feng Jia, Dongya Qiu, Keren Shi, Weiwei Zhang
    2021, 32(4):  301-306.  doi:10.1016/j.cjche.2020.08.002
    Abstract ( 43 )   PDF (3928KB) ( 38 )  
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    Phenol and its derivatives are highly toxic pollutants in industrial wastewater for the ecological environments, so there is essential attention to develop effective means of removing these harmful substances from water. In this work, the microorganism was immobilized into polymeric composite gel beads prepared by the effective recombination of natural abundant chitosan (CS) and industrial polyvinyl alcohol (PVA) for treating phenolic compounds. The degradation rate of 99.5% can be achieved to treat 100 mg·L-1 of phenol at 30℃ using the fresh resultant immobilized microorganism, where only 21.1% degradation rate was obtained by the free microorganism under the identical conditions. The recycling experiments of repeated 90 times to treat 100 mg·L-1 of phenol displayed that the degradation rate of phenol was stable to 99% with the appearance of beads unchanged significantly, indicating the immobilized microorganism possessed excellent operating stability. Moreover, while the phenol derivatives of 100 mg·L-1 were treated catalytically including p-methylphenol, catechol, and o-aminophenol for 24 h by the immobilized microorganism, the degradation rates were all above 95%. The immobilized microorganism into PVA-CS polymeric composite with excellent operating stability and degradation activity would provide a feasible solution for treating phenolic compounds in water in industrial applications.
    Hydrogenolysis of organosolv hydrolyzed lignin over high-dispersion Ni/Al-SBA-15 catalysts for phenolic monomers
    Ying Xu, Pengru Chen, Wei Lv, Chenguang Wang, Longlong Ma, Qi Zhang
    2021, 32(4):  307-314.  doi:10.1016/j.cjche.2020.10.008
    Abstract ( 49 )   PDF (6502KB) ( 49 )  
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    Efficiency and recycling of catalysts are important for the lignin hydrogenolysis to obtain phenolic monomers. In this work, a series of high-dispersion Ni/Al-SBA-15 catalysts were prepared by a direct and effective preparation method, and then used in the hydrogenolysis of diphenyl ether (DE) and organosolv hydrolyzed lignin (OHL) for phenolic monomers. The universality of as-made catalysts in different solvents and cyclic performance were investigated. Results showed that the addition of ethylene glycol (EG) during the loading process of Ni promoted the dispersion of metal efficiently. High dispersion of Ni species could highly enhance the conversion of DE and the OHL which Ni/Al-SBA-15(1EG) exhibited the excellent catalytic performance. Decalin was found to be most effective solvent on the conversion of DE (99.16%). 84.77% liquefaction ratio and 21.36% monomer yield were achieved, and no obvious char was observed after the depolymerization of OHL in ethanol solvent at 280℃ for 4 h over the Ni/Al-SBA-15(1EG) catalyst.
    An efficient route towards R-2-phenoxypropionic acid synthesis for biotransformative production of R-2-(4-hydroxyphenoxy)propionic acid
    Haiyan Zhou, Yizuo Li, Rui Jiang, Xianlin Wang, Yuanshan Wang, Yaping Xue, Yuguo Zheng
    2021, 32(4):  315-323.  doi:10.1016/j.cjche.2020.06.013
    Abstract ( 69 )   PDF (2903KB) ( 111 )  
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    R-2-(4-hydroxyphenoxy)propionic acid (R-HPPA) is a key intermediate for the synthesis of classic herbicides with high selectivity against grassy weed. The main route for R-HPPA biosynthesis is to hydroxylate the substrate R-2-phenoxypropionic acid (R-PPA) at C-4 position with microbes. In order to provide sufficient R-PPA for the industrial production of R-HPPA, an effective R-PPA synthesis method was established and optimized in this work. The synthesis process mainly consisted of two steps:(1) synthesis of S-2-chloropropionic acid from L-alanine via diazotization and chlorination reactions; and (2) synthesis of R-PPA from S-2-chloropropionic acid and phenol via etherification reaction. The optimal reaction conditions were as follows:HCl:NaNO2:KI:L-Ala=2.0:1.2:0.7:1.0 (in molar), 125℃ reflux for 1.5 h, with KI as catalyst, and KI:S-2-chloropropionic acid:phenol=0.075:1.2:1.0 (in molar). Under these conditions, an improved molar conversion rate (74.9%, calculated in phenol) was achieved. After extraction using anionic exchange resin Amberlite IRA-400 (CI), R-PPA product with a purity of 95.08% was obtained. The purified R-PPA was identified and evaluated in the application of the biotransformative production of R-HPPA. The results indicated that the synthesized R-PPA supported the R-HPPA biosynthesis with a comparable yield as that of the standard R-PPA. The R-PPA synthesis method provided herein exhibited the advantages of low price and easy availability of raw materials, less toxicity of reagents, simple manipulations, and low equipment/instrument requirements.
    Energy, Resources and Environmental Technology
    Investigation of the methane hydrate surface area during depressurization-induced dissociation in hydrate-bearing porous media
    Xuke Ruan, Xiao-Sen Li
    2021, 32(4):  324-334.  doi:10.1016/j.cjche.2020.10.014
    Abstract ( 66 )   PDF (4567KB) ( 60 )  
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    The surface area of hydrate during dissociation in porous media is essentially important for the kinetics of hydrate dissociation. In this study, the methane hydrate surface area was investigated by the comparison results of experiments and numerical simulations during hydrate decomposition in porous media. The experiments of methane hydrate depressurization-induced dissociation were performed in a 1D high pressure cell filled with glass beads, an improved and valid 1D core-scale numerical model was developed to simulate gas production. Two conceptual models for hydrate dissociation surface area were proposed based on the morphology of hydrate in porous media, which formed the functional form of the hydrate dissociation surface area with porosity, hydrate saturation and the average radius of sand sediment particles. With the establishment of numerical model for depressurization-induced hydrate dissociation in porous media, the cumulative gas productions were modeling and compared with the experimental data at the different hydrate saturations. The results indicated that the proposed prediction equations are valid for the hydrate dissociation surface area, and the grain-coating surface area model performs well at lower hydrate saturation for hydrate dissociation simulation, whereas at higher hydrate saturation, the hydrate dissociation simulation from the pore-filling surface area model is more reasonable. Finally, the sensitivity analysis showed that the hydrate dissociation surface area has a significant impact on the cumulative gas production.
    Effect of operating parameters on the performance of thermally regenerative ammonia-based battery for low-temperature waste heat recovery
    Yu Shi, Liang Zhang, Jun Li, Qian Fu, Xun Zhu, Qiang Liao, Yongsheng Zhang
    2021, 32(4):  335-340.  doi:10.1016/j.cjche.2020.09.031
    Abstract ( 69 )   PDF (2508KB) ( 27 )  
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    This study investigated the important factors that affect the operating parameters of thermally regenerative ammonia-based batteries (TRABs), including the metal electrode type, membrane type, electrode surface area, electrode distance, electrolyte concentration, and ammonia concentration. The experimental results showed that the maximum power density of TRABs with a Cu electrode was 40.0 W·m-2, which was considerably higher than that with Ni (0.34 W·m-2) and Co (0.14 W·m-2) electrodes. TRABs with an anion exchange membrane had a 28.6% higher maximum power density than those with a cation exchange membrane. An increased electrode surface resulted in an increased maximum power but a decreased maximum power density. Within a certain range, TRAB performance was enhanced with decreased electrode distance and increased electrolyte concentration. An increased ammonia concentration resulted in enhanced ammonia transfer and improved the TRAB performance.
    Synthesis and characterization of a series of cross-linked polyamines for removal of Erichrome Black T from aqueous solution
    Mohammad Saood Manzar, Shamsuddeen A. Haladu, Mukarram Zubair, Nuhu Dalhat Mu'azu, Aleem Qureshi, Nawaf I. Blaisi, Thomas F. Garrison, Othman Charles S. Al Hamouz
    2021, 32(4):  341-352.  doi:10.1016/j.cjche.2020.09.052
    Abstract ( 64 )   PDF (9497KB) ( 20 )  
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    A new series of polymers comprising four terpolymers was synthesized via Mannich polycondensation of benzene-1,4-diamine, formaldehyde and piperazine by varying the benzene-1,4-diamine and piperazine ratio. The new polyamines (labeled Dipip) were characterized using 13C solid-state NMR, FT-IR, TGA, DSC, XRD, SEM and EDX. The adsorptive performances of the synthesized polymers for Erichrome Black T (EBT) uptake from aqueous solution were investigated under batch process. Equilibrium, kinetic, and thermodynamic studies were conducted to determine the influence of different operational parameters of the adsorption process. The two most promising polymers among the series show an excellent EBT removal efficiency of ~100% and ~95% with high adsorption capacities of 775 mg·g-1 and 917 mg·g-1, respectively at a meager dosage of 5 mg. The sorption of EBT on the polymers was well described by Redlich-Peterson & Langmuir model while the kinetic studies indicate that pseudo-second order model was followed. For the thermodynamic studies, the negative DG and positive DH values obtained suggest a spontaneity of the sorption process which was endothermic in nature. The results of reusability test of the resins were promising even at the fourth cycle, showcasing the potentials of the new polymers in dyes contaminated water treatment.
    Investigation on the fabrication of lightweight aggregate with acid-leaching tailings of vanadium-bearing stone coal minerals and red mud
    Chunguang Song, Hongling Zhang, Yuming Dong, Lili Pei, Honghui Liu, Junsheng Jiang, Hongbin Xu
    2021, 32(4):  353-359.  doi:10.1016/j.cjche.2020.09.020
    Abstract ( 50 )   PDF (3183KB) ( 43 )  
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    Proper treatment of acid-leaching tailings (ALTs) of vanadium-bearing stone coal minerals is of great urgency. One approach is adding it into the raw materials during the preparation of lightweight aggregate (LWA). But clay is always needed. In this paper, another solid waste, red mud, was mixed with ALTs as a source of flux components instead of clay. Evaluation of the physical characteristics, morphological structures, as well as crystal phases during the sintering process were investigated. When their mixtures with a proper ratio were sintered at 1080℃, a glassy phase with certain viscosity was formed, and the gases generated simultaneously were encapsulated by the melt. Finally, LWA with a one-hour water absorption as low as 1.46%, a bulk density as low as 728.76 kg·m-3 and a compressive strength as high as 10.77 MPa was fabricated.
    Performance evaluation of the incorporation of different wire meshes in between perforated current collectors and membrane electrode assembly on the Passive Direct methanol fuel cell
    Muralikrishna Boni, S. Srinivasa Rao, G. Naga Srinivasulu
    2021, 32(4):  360-367.  doi:10.1016/j.cjche.2020.07.038
    Abstract ( 65 )   PDF (5766KB) ( 74 )  
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    Passive Direct methanol fuel cells (DMFC) are more suitable for charging small capacity electronic devices. In passive DMFC, the fuel and oxidant are supplied by diffusion and natural convection process on the anode and cathode sides respectively. Current collectors (CC) play a vital importance in fuel cell performance. This paper presents the combined impact of perforated and wire mesh current collectors (WMCC) on passive DMFC performance. Three types of open ratios of perforated current collectors (PCC), such as 45.40%, 55.40% and 63.40% and two types of wire mesh current collectors with open ratios of 38.70% and 45.40% were chosen for the experimental work. A combination of Taguchi-L9 rule is considered. A combination of three PCC and two WMCC on both anode and cathode was used. Methanol concentration was varied from 1 mol·L-1-5 mol·L-1 for nine combinations of PCC and WMCC. From the experimental results, it is noticed that the combination of PCC and WMCC with an open ratio of 55.40% and 38.70% incorporated passive DMFC produced peak power density at 5 mol·L-1 of methanol concentration. The passive DMFC performance was evaluated in terms of maximum power density and maximum current density. The combined current collectors of PCC and WMCC open ratios of 55.40% + 38.70% have more stable voltage than single PCC of open ratio 63.40% at 4 mol·L-1 of methanol concentration.
    Modified corn-core powder for enhancing sludge dewaterability: Synthesis, characterization and sludge dewatering performance
    Zhiying Guo, Liping Ma, Quxiu Dai, Xinbo Yang, Ran Ao, Jie Yang, Jing Yang, Wengang Li
    2021, 32(4):  368-377.  doi:10.1016/j.cjche.2020.09.022
    Abstract ( 69 )   PDF (4547KB) ( 20 )  
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    The high water content of sludge has always posed significant challenges for its treatment. Synthetic flocculants, which are widely used in sewage treatment plants, can cause secondary pollution during their production and use. Thus, natural polymer flocculants made of natural materials have received increased research attention recently. Corn-core, an agricultural waste, was modified through alkalization with sodium hydroxide (NaOH) and etherification with cetyltrimethylammonium bromide (CTMAB) in this study. The L16 (45) orthogonal array was used to study the modification conditions. The moisture content (MC) of treated sludge was reduced by approximately 37% with the addition of modified corn-core powder (MCCP), which was synthesized under optimal conditions. In addition, changes in the functional groups of the material before and after modification were determined by FT-IR. Thermogravimetric analysis indicated that MCCP was steady at room temperature, moreover, BET analysis showed that MCCP had greater surface area. The microstructures of material before and after modification were examined by scanning electron microscopy, revealing that MCCP had a flake-shaped structure and had an increased area of contact area with sludge particles. MCCP is a dehydrating agent that can enhance sludge dewaterability through charge neutralization and re-agglomeration and provide superior economic benefits.
    Synthesis of cation exchange resin-supported iron and magnesium oxides/hydroxides composite for nitrate removal in water
    Trung Thanh Nguyen, Vu Anh Khoa Tran, Le Ba Tran, Phuoc Toan Phan, Minh Tan Nguyen, Long Giang Bach, Surapol Padungthon, Cong Khiem Ta, Nhat Huy Nguyen
    2021, 32(4):  378-384.  doi:10.1016/j.cjche.2020.11.032
    Abstract ( 56 )   PDF (9610KB) ( 9 )  
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    In this study, we reported on the concept and practical use of cation exchange resin (CER) for removing anions in water via pretreating the CER with metal salts. The cation exchange resin-supported iron and magnesium oxides/hydroxides composite (Fe-Mg/CER) was synthesized and introduced as a new and potential adsorbent for selective removal of nitrate ion in the water environment. Characteristics of Fe-Mg/CER were determined by techniques such as Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. The results showed that Fe-Mg/CER material had a high nitrate adsorption capacity of 200 mg NO3-·g-1 with a fast equilibrium adsorption time of 30 min at pH 5. In addition, it had good durability of at least 10 times of regeneration, which could be applied to practical water and wastewater treatment.
    Fabrication of a highly efficient new nanocomposite polymer gel for controlling the excess water production in petroleum reservoirs and increasing the performance of enhanced oil recovery processes
    Sajad Asadizadeh, Shahab Ayatollahi, Bahman ZareNezhad
    2021, 32(4):  385-392.  doi:10.1016/j.cjche.2020.12.023
    Abstract ( 58 )   PDF (2532KB) ( 33 )  
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    A new nanocomposite polymer gel is synthesized for reduction of excess water production in petroleum reservoirs at real operating conditions. This new nanocomposite gel contains SiO2 nanoparticles, partially hydrolyzed polyacrylamide (HPAM) and chromium triacetate. High pressure and high temperature tests using porous carbonate core are carried out to evaluate the effects of nanoparticles on the synthesized polymer gel performance. It is shown that the residual resistance factor ratio of water to oil using the synthesized polymer gel nanocomposite in this work is much higher than that of the ordinary polymer gels. The presented results confirm the high performance of the synthesized nanocomposite polymer gel for decreasing the water flow through porous carbonate bed. A mathematical model for description of oil and water flow behavior in the presence of synthesized nanocomposite polymer gel is also presented. The presented nano polymer gel leads to considerable cost saving in enhanced oil recovery (EOR) processes.
    An advanced ash fusion study on the melting behaviour of coal, oil shale and blends under gasification conditions using picture analysis and graphing method
    Yang Meng, Peng Jiang, Yuxin Yan, Yuxin Pan, Xinyun Wu, Haitao Zhao, Nusrat Sharmin, Edward Lester, Tao Wu, Cheng Heng Pang
    2021, 32(4):  393-407.  doi:10.1016/j.cjche.2020.10.011
    Abstract ( 67 )   PDF (9128KB) ( 53 )  
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    This study investigates the potential of solid fuel blending as an effective approach to manipulate ash melting behaviour to alleviate ash-related problems during gasification, thus improving design, operability and safety. The ash fusion characteristics of Qinghai bituminous coal together with Fushun, Xinghua and Laoheishan oil shales (and their respective blends) were quantified using a novel picture analysis and graphing method, which incorporates conventional ash fusion study, dilatometry and sintering strength test, in a CO/CO2 atmosphere. This image-based characterisation method was used to monitor and quantify the complete melting behaviour of ash samples from room temperature to 1520℃. The impacts of blending on compositional changes during heating were determined experimentally via X-ray diffraction and validated computationally using FactSage. Results showed that the melting point of Qinghai coal ash to be the lowest at 1116℃, but would increase up to 1208℃, 1161℃ and 1160℃ with the addition of 30%-50% of Laoheishan, Fushun, and Xinghua oil shales, respectively. The formation of high-melting anorthite and mullite structures inhibits the formation of low-melting hercynite. However, the sintering point of Qinghai coal ash was seen to decrease from 1005℃ to 855℃, 834℃, and 819℃ in the same blends due to the formation of low-melting aluminosilicate. Results also showed that blending directly influences the sintering strength during the various stages of melting. The key finding from this study is that it is possible to mitigate against the severe ash slagging and fouling issue arising from high calcium and iron coals by co-gasification with a high silica-alumina oil shale. Moreover, blending coals with oil shales can also modify the ash melting behaviour of fuels to create the optimal ash chemistry that meets the design specification of the gasifier, without adversely affecting thermal performance.
    Evaluation of oxygen uncoupling characteristics of oxygen carrier using micro-fluidized bed thermogravimetric analysis
    Lei Liu, Zhenshan Li, Ye Li, Ningsheng Cai
    2021, 32(4):  408-415.  doi:10.1016/j.cjche.2020.11.023
    Abstract ( 57 )   PDF (6936KB) ( 8 )  
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    Oxygen uncoupling characteristics of a natural manganese ore and a perovskite-type oxide CaMn0.5Ti0.375Fe0.125O3 were studied by using a microfluidized bed thermogravimetric analysis (MFB-TGA) technology which is based on a real-time mass measurement of fluidizing particles inside a bubbling bed reactor. The chemical stability, kinetics of the oxygen release and uptake reactions and fluidization property were investigated and the experimental data measured by MFB-TGA were compared with the results in a regular TGA instrument (TGA Q500). The regular TGA Q500 results show the reactivity of both the manganese ore and perovskite oxide are stable for multi cycles, and the oxygen uncoupling capacity of the manganese ore is ~1.2% (mass) which is ~2 times higher than that of the perovskite oxide. However, the experimental results from the MFB-TGA indicated that there is a serious agglomeration for the manganese ore. A very important finding is that the reaction rate of oxygen release and oxygen uptake of the perovskite oxide measured by the MFB-TGA are ~2 and ~4 times faster than that of testedby the TGA Q500. We can conclude that MFB-TGA is a very useful tool to measure the reactivity stability and kinetics of oxygen carriers in high-throughput analysis instead of the regular TGA.
    Porous nitrogen-enriched hollow carbon nanofibers as freestanding electrode for enhanced lithium storage
    Xiaosa Xu, Yuqian Qiu, Jianping Wu, Baichuan Ding, Qianhui Liu, Guangshen Jiang, Qiongqiong Lu, Jiangan Wang, Fei Xu, Hongqiang Wang
    2021, 32(4):  416-422.  doi:10.1016/j.cjche.2020.09.055
    Abstract ( 86 )   PDF (5388KB) ( 39 )  
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    One-dimensional porous carbons bearing high surface areas and sufficient heteroatom doped functionalities are essential for advanced electrochemical energy storage devices, especially for developing freestanding film electrodes. Here we develop a porous, nitrogen-enriched, freestanding hollow carbon nanofiber (PN-FHCF) electrode material via filtration of polypyrrole (PPy) hollow nanofibers formed by in situ self-degraded template-assisted strategy, followed by NH3-assisted carbonization. The PN-FHCF retains the freestanding film morphology that is composed of three-dimensional networks from the entanglement of 1D nanofiber and delivers 3.7-fold increase in specific surface area (592 m2·g-1) compared to the carbon without NH3 treatment (FHCF). In spite of the enhanced specific surface area, PNFHCF still exhibits comparable high content of surface N functionalities (8.8%, atom fraction) to FHCF. Such developed hierarchical porous structure without sacrificing N doping functionalities together enables the achievement of high capacity, high-rate property and good cycling stability when applied as self-supporting anode in lithium-ion batteries, superior to those of FHCF without NH3 treatment.
    Comparative study of different hydro-dynamic flow in microbial fuel cell stacks
    Suransh Jain, Arvind Kumar Mungray
    2021, 32(4):  423-430.  doi:10.1016/j.cjche.2020.10.016
    Abstract ( 62 )   PDF (3760KB) ( 39 )  
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    This work has investigated the scale-up potential of microbial fuel cells (MFCs) under stacking mode. Stacking was done in batch mode and continuous mode. Batch feeding mode stacks were operated in electrical series (S) and parallel (P) mode. Continuous feeding mode stacks were kept in electrically parallel mode with different hydro-dynamic patterns. The two continuous stacks were connected hydrodynamically in series (i.e. Parallel Dependent; PD) and parallel (i.e. Parallel Independent; PID) configurations. The performance of the continuous stacks was evaluated on the basis of COD consumption rate, power generation and coulombic efficiency. PID obtained highest power (0.47 mW) which was approximately 3.6 times that of PD configuration (0.13 mW). The rate of COD consumption was also highest in PID stack (3091.75 mg·L-1·d-1). Coulombic efficiency of the PID stack was 14.26% which was approximately 292.8% of the PD stack. The results confirmed that the parallel electrical connection hybridized with the independent hydro-dynamic flow gives the best possible results when working with stacking of MFCs.
    Modeling viscosity of methane, nitrogen, and hydrocarbon gas mixtures at ultra-high pressures and temperatures using group method of data handling and gene expression programming techniques
    Farzaneh Rezaei, Saeed Jafari, Abdolhossein Hemmati-Sarapardeh, Amir H. Mohammadi
    2021, 32(4):  431-445.  doi:10.1016/j.cjche.2020.07.008
    Abstract ( 53 )   PDF (8331KB) ( 12 )  
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    Accurate gas viscosity determination is an important issue in the oil and gas industries. Experimental approaches for gas viscosity measurement are time-consuming, expensive and hardly possible at high pressures and high temperatures (HPHT). In this study, a number of correlations were developed to estimate gas viscosity by the use of group method of data handling (GMDH)-type neural network and gene expression programming (GEP) techniques using a large data set containing more than 3000 experimental data points for methane, nitrogen, and hydrocarbon gas mixtures. It is worth mentioning that unlike many of viscosity correlations, the proposed ones in this study could compute gas viscosity at pressures ranging between 34 and 172 MPa and temperatures between 310 and 1300 K. Also, a comparison was performed between the results of these established models and the results of ten well-known models reported in the literature. Average absolute relative errors of GMDH models were obtained 4.23%, 0.64%, and 0.61% for hydrocarbon gas mixtures, methane, and nitrogen, respectively. In addition, graphical analyses indicate that the GMDH can predict gas viscosity with higher accuracy than GEP at HPHT conditions. Also, using leverage technique, valid, suspected and outlier data points were determined. Finally, trends of gas viscosity models at different conditions were evaluated.
    Materials and Product Engineering
    Synthesis and characterization of high strength polyimide/silicon nitride nanocomposites with enhanced thermal and hydrophobic properties
    Tadele Daniel Mekuria, Lei Wang, Chunhong Zhang, Ming Yang, Qingtao Lv, Diaa Eldin Fouad
    2021, 32(4):  446-453.  doi:10.1016/j.cjche.2020.09.066
    Abstract ( 57 )   PDF (10476KB) ( 11 )  
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    Polyimide (PI) composite films were synthesized incorporating amino modified silicon nitride (Si3N4) nanoparticles into PI matrix via in situ polymerization technique. The mechanical and thermal performances as well as the hydrophobic properties of the as prepared composite films were investigated with respect to the dosage of the filler in the PI matrix. According to Thermogravimetric (TGA) analysis, meaningful improvements were achieved in T5 (5% weight loss temperature) and T10 (10% weight loss temperature) up to 54.1℃ and 52.4℃, respectively when amino functionalized nano-Si3N4 particles were introduced into the PI matrix. The differential scanning calorimetry (DSC) results revealed that the glass transition temperature (Tg) of the composites was considerably enhanced up to 49.7℃ when amino functionalized Si3N4 nanoparticles were incorporated in the PI matrix. Compared to the neat PI, the PI/Si3N4 nanocomposites exhibited very high improvement in the tensile strength as well as Young's modulus up to 105.4% and 138.3%, respectively. Compared to the neat PI, the composites demonstrated highly decreased water absorption behavior which showed about 68.1% enhancement as the content of the nanoparticles was increased to 10 wt%. The SEM (Scanning electron microscope) images confirmed that the enhanced thermal, mechanical and water proof properties are essentially attributed to the improved compatibility of the filler with the matrix and hence, enhanced distribution inside the matrix because of the amino groups on the surface of Si3N4 nanoparticles obtained from surface functionalization.
    Synthesis of zinc oxide nanoparticles reinforced clay and their applications for removal of Pb (II) ions from aqueous media
    Abdul Samad, Muhammad Imran Din, Mahmood Ahmed, Saghir Ahmad
    2021, 32(4):  454-461.  doi:10.1016/j.cjche.2020.09.043
    Abstract ( 44 )   PDF (5216KB) ( 88 )  
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    The aim of the study was to synthesize zinc oxide nanoparticles (ZnONPs) composite with clay by a novel route and then to explore the capability of composite of ZnONPs and silty clay (SC) as adsorbents for Pb (II) eradication from aqueous media by batch adsorption method. The effect of different operating factors like temperature, pH, dose and time of contact on the adsorption process were studied to optimize the conditions. Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherms were applied for the interpretation of the process. The R2 and q values obtained from Langmuir model suggested that the process is best interpreted by this model. The values of adsorption capacity (qm) noted were 12.43 mg·g-1 and 14.54 mg·g-1 on SC and ZnONPs-SC respectively. The kinetic studies exposed that pseudo second order (PSO) kinetics is followed by the processes suggesting that more than one steps are involved to control the rate of reactions. Various thermodynamic variables such as change in free energy (ΔGΘ), change in enthalpy (ΔHΘ) and change in entropy (ΔSΘ) were calculated. Thermodynamic data suggested that Pb (II) adsorption on SC and ZnONPs-SC are spontaneous, endothermic and feasible processes.
    Preparation and antibacterial properties of polycaprolactone/quaternized chitosan blends
    Anrong Zeng, Yangtao Wang, Dajun Li, Juedong Guo, Qiaowen Chen
    2021, 32(4):  462-471.  doi:10.1016/j.cjche.2020.10.001
    Abstract ( 57 )   PDF (4124KB) ( 38 )  
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    This article is a preliminary study on antibacterial blends of polycaprolactone, chitosan and quaternized chitosan by melt processing. Blends were characterized, mechanical test and antibacterial evaluation against Escherichia coli and Staphylococcus aureus, were conducted. Results showed that the antibacterial potential of chitosan was limited in blends and polycaprolactone/chitosan did not show significant antibacterial effect compared with neat polycaprolactone (PCL). Inhibition rates of polycaprolactone/quaternized chitosan were 39.2%-99.9% against Escherichia coli, while inhibition rate was 40.9%-99.9% against Staphylococcus aureus. When quaternized chitosan (QCTS) content was up to 20%, blends exhibited 99.9% inhibition rates against both two types of bacteria.
    Synthesis and optimization of high surface area mesoporous date palm fiber-based nanostructured powder activated carbon for aluminum removal
    Alfarooq O. Basheer, Marlia M. Hanafiah, Mohammed Abdulhakim Alsaadi, Y. Al-Douri, Abbas A. Al-Raad
    2021, 32(4):  472-484.  doi:10.1016/j.cjche.2020.09.071
    Abstract ( 53 )   PDF (15735KB) ( 8 )  
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    Date palm fiber (DPF) derived from agrowaste was utilized as a new precursor for the optimized synthesis of a cost-effective, nanostructured, powder-activated carbon (nPAC) for aluminum (Al3+) removal from aqueous solutions using carbonization, KOH activation, response surface methodology (RSM) and central composite design (CCD). The optimum synthesis condition, activation temperature, time and impregnation ratio were found to be 650℃, 1.09 hour and 1:1, respectively. Furthermore, the optimum conditions for removal were 99.5% and 9.958 mg·g-1 in regard to uptake capacity. The optimum conditions of nPAC was analyzed and characterized using XRD, FTIR, FESEM, BET, TGA and Zeta potential. Moreover, the adsorption of the Al3+ conditions was optimized with an integrated RSM-CCD experimental design. Regression results revealed that the adsorption kinetics data was well fitted by the pseudo-second order model, whereas the adsorption isotherm data was best represented by the Freundlich isotherm model. Optimum activated carbon indicated that DPF can serve as a cost-effective precursor adsorbent for Al3+ removal.
    Structure-dependent re-dispersibility of graphene oxide powders prepared by fast spray drying
    Yexun Shi, Chang Li, Liming Shen, Ningzhong Bao
    2021, 32(4):  485-492.  doi:10.1016/j.cjche.2020.08.023
    Abstract ( 59 )   PDF (2284KB) ( 55 )  
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    The graphene oxide powder (GOP) obtained from the spray drying process often exhibits poor redispersibility which is considered due to the partial reduction of GO sheets. The reduction of drying temperature can effectively increase the re-dispersibility of GOP, but result in a decreased drying efficiency. Herein, we found that the re-dispersibility of GOP is strongly affected by its microstructure, which is determined by the feed concentration. With the increase of feed concentration, the GO nanosheet assembly varies from the disordered stacking to relatively oriented assembly, making the morphology of the GOP transform from ball-like (the most crumpled one) to flake-like (the least crumpled one), and the 0.8 mg·ml-1 is the threshold concentration for the morphology, structure, and re-dispersibility change. Once the feed concentration reaches 0.8 mg·ml-1, the appearance of the nematic phase in droplet ensures the relatively oriented assembly of GO sheets to form the layered structure with a low crumpling degree, which greatly improves the polar parts surface tension of the solid GOP, making the GOP easier to form hydrogen bonding with water during the redispersion process, thus stabilizing dispersion. This work provides useful information for understanding the relationships between the morphology, microstructure, and final re-dispersibility of GOPs.