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SCI和EI收录∣中国化工学会会刊
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Table of Content
28 January 2021, Volume 29 Issue 1
    Review
    Perspectives and challenges of hydrogen storage in solid-state hydrides
    Zhen Chen, Zhongliang Ma, Jie Zheng, Xingguo Li, Etsuo Akiba, Hai-Wen Li
    2021, 29(1):  1-12.  doi:10.1016/j.cjche.2020.08.024
    Abstract ( 236 )   PDF (2348KB) ( 406 )  
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    Hydrogen has been widely considered as a clean energy carrier that bridges the energy producers and energy consumers in an efficient and safe way for a sustainable society. Hydrogen can be stored in a gas, liquid and solid states and each method has its unique advantage. Though compressed hydrogen and liquefied hydrogen are mature technologies for industrial applications, appropriate measures are necessary to deal with the issues at high pressure up to around 100 MPa and low temperature at around 20 K. Distinct from those technologies, storing hydrogen in solid-state hydrides can realize a more compact and much safer approach that does not require high hydrogen pressure and cryogenic temperature. In this review, we will provide an overview of the major material groups that are capable of absorbing and desorbing hydrogen reversibly. The main features on hydrogen storage properties of each material group are summarized, together with the discussion of the key issues and the guidance of materials design, aiming at providing insights for new material development as well as industrial applications.
    Fluid Dynamics and Transport Phenomena
    Wet flue gas desulfurization performance of 330 MW coal-fired power unit based on computational fluid dynamics region identification of flow pattern and transfer process
    Jiangyuan Qu, Nana Qi, Kai Zhang, Lifeng Li, Pengcheng Wang
    2021, 29(1):  13-26.  doi:10.1016/j.cjche.2020.08.004
    Abstract ( 159 )   PDF (5111KB) ( 147 )  
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    Wet Flue Gas Desulfurization (WFGD) unit based upon spray scrubber has been widely employed to control SO2 emissions from flue gas in coal-fired power plant. To clarify the dependence of desulfurization performance on inter-phase transfer behaviors with non-ideal contacting patterns of flue gas and slurry droplets, three regions in spray scrubber are distinguished in terms of gas-slurry flow structures using CFD method in the Eulerian-Lagrangian framework. A comprehensive model is established by involving the transfer process between two phases and chemical reactions in aqueous phase, which is validated with the measured data from a WFGD scrubber of 330 MW coal-fired power unit. Numerical results show that the overall uniformity degree of flue gas in whole scrubber is largely determined by the force-balanced droplets in the middle part of scrubber, which is dominated by counter-current mode. Both momentum transfer behavior and SO2 chemical absorption process present the synchronicity with the evolution of gas-slurry flow pattern, whilst the heat transfer together with H2O evaporation has little effect on overall absorption process. Three regions are firstly defined as Gas Inlet Region (GIR), Dominant Absorption Region (DAR) and Slurry Dispersed Region (SDR) from the bottom to top of scrubber. SO2 is mainly scrubbed in DAR, which provides much more intensive interaction between two phases compared to GIR or SDR. A better understanding of the desulfurization process is obtained from the fundamental relationship between transport phenomena and chemical reactions based upon the complicated hydrodynamics of gas-slurry two-phase flow, which should be useful for designing and optimizing the scrubber in coal-fired power unit.
    EMMS-based modeling of gas-solid generalized fluidization: Towards a unified phase diagram
    Juanbo Liu, Xinhua Liu, Wei Ge
    2021, 29(1):  27-34.  doi:10.1016/j.cjche.2020.07.057
    Abstract ( 133 )   PDF (2077KB) ( 53 )  
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    Hydrodynamic features of gas-solid generalized fluidization can be well expressed in the form of phase diagrams, which are important for engineering design. Mesoscale structure presents almost universally in generalized fluidization and should be considered in such phase diagrams. However, current phase diagrams were mainly proposed for cocurrent upward flow according to experimental data or empirical correlations with homogeneous assumption. The energy-minimization multiscale (EMMS) model has shown the capability of capturing mesoscale structure in generalized fluidization, so EMMS-based phase diagrams of generalized fluidization were proposed in this article, which describe more reasonable global hydrodynamics over all regimes including the important engineering phenomena of choking and flooding. These characteristics were also found in discrete particle simulation under various conditions. For wider range of application, the typical hydrodynamic parameters of the phase diagrams were correlated to non-dimensional numbers reflecting the effects of material properties and operation conditions. This study thus shows a possible route to develop a unified phase diagram in the future.
    Using expansion units to improve CO2 absorption for natural gas purification-A study on the hydrodynamics and mass transfer
    Kai Zhu, Chaoqun Yao, Yanyan Liu, Guangwen Chen
    2021, 29(1):  35-46.  doi:10.1016/j.cjche.2020.08.025
    Abstract ( 95 )   PDF (4620KB) ( 46 )  
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    The usage of capillary tubes for CO2 absorption suffers from small residence time, which leads to reduced performance for large throughput. This work presents a method of connecting expansion units to capillary tubes to serve as a residence time delayer. The effect of the expansion unit on gas-liquid hydrodynamics, pressure drop and mass transfer coefficient (kLa) are investigated under various operating pressures up to 4.0 MPa, for both physical and chemical absorption. A novel periodic jetting flow is found in the expansion unit, which can intensify the CO2 absorption. Experimental results show that the strategy can significantly decrease the pressure drop while maintaining the absorption performance to a large extent. The overall kLa for physical and chemical absorption are correlated to pressure drop, respectively. Besides, CO2 loading in rich absorbents increases dramatically compared to literature studies with only micromixers or capillary tubes, which is beneficial to regenerate solvent. The study verifies the concept that pre-treatment with water can largely reduce the usage of amines, and can also provide a guide for process design in natural gas purification such as biogas recovery.
    Simulation and experimental study on the surface morphology and energy lost of the target material under non-overlapping impact of angular particles
    Xuewen Cao, Chenyang Fu, Zhenqiang Xie, Chao Wu, Xiaoyang Sun
    2021, 29(1):  47-56.  doi:10.1016/j.cjche.2020.06.042
    Abstract ( 116 )   PDF (3396KB) ( 32 )  
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    In order to further understand the effect of solid impurities on pipeline wall during erosion, the particle impact process without fluid was extracted for specific study. The effect of multi-impact particles on the wall of pipeline was studied experimentally and simulated. In this experiment, an improved ejection apparatus was implemented to carry out multi-impacts non-overlapping impingement by rhombic particles made of high speed steel(W18Cr4V) on the AA6061 aluminum alloy plate through changing particle angle, incident angle, orientation angle and impact velocity. As a result, each particle's penetration depth was investigated and particles' rebound trajectory can be described through this experiment as well as surface morphology of the target material after impingement. The ductile damage criterion, shear damage criterion and MSFLD damage criterion were jointly implemented in ABAQUS/CAE software to simulate the whole process of collision which proved to be effective by getting consistent result compared with experimental data. It is found that under the condition of continuous non-overlapping impact, the target material produces a small work hardening effect in the impact area by converting kinetic energy of moving particles into internal energy of plate so as to reduce the penetration depth of each impact particle.
    Numerical optimization for blades of Intermig impeller in solid-liquid stirred tank
    Xiaolong Li, Hongliang Zhao, Zimu Zhang, Yan Liu, Ting'an Zhang
    2021, 29(1):  57-66.  doi:10.1016/j.cjche.2020.08.044
    Abstract ( 144 )   PDF (4253KB) ( 59 )  
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    The multiphase flow in the solid-liquid tank stirred with a new structure of Intermig impeller was analyzed by computational fluid dynamics (CFD). The Eulerian multiphase model and standard k-ε turbulence model were adopted to simulate the fluid flow, turbulent kinetic energy distribution, mixing performance and power consumption in a stirred tank. The simulation results were also verified by the water model experiments, and good agreement was achieved. The solid-liquid mixing performances of Intermig impeller with different blade structures were compared in detail. The results show that the improved Intermig impeller not only enhances the solid mixing and suspension, but also saves more than 20% power compared with the standard one. The inner blades have relatively little influence on power and the best angle of inner blades is 45°, while the outer blades affect greatly the power consumption and the optimized value is 45°.
    Separation Science and Engineering
    Dynamic control analysis of interconnected pressure-swing distillation process with and without heat integration for separating azeotrope
    Jingwei Yang, Zhengkun Hou, Yao Dai, Kang Ma, Peizhe Cui, Yinglong Wang, Zhaoyou Zhu, Jun Gao
    2021, 29(1):  67-76.  doi:10.1016/j.cjche.2020.07.059
    Abstract ( 160 )   PDF (4882KB) ( 62 )  
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    Dynamic controls of pressure-swing distillation with an intermediate connection (PSDIC) process of ethyl acetate and ethanol separation were investigated. The double temperature/composition cascade control structure can perfectly implement effective control when ±20% feed disturbances were introduced. This control structure did not require the control of the flowrate of the side stream. The dynamic controllability of PSDIC with partial heat integration (PHIPSDIC) was also explored. The improved control structure can effectively control ±20% feed disturbances. However, in industrial production, simple controller, sensitive and easy to operate, is the optimal target. To avoid the use of component controllers or complex control structure, the original product purities could be maintained using the basic control structure for the PSDIC process if the product purities in steady state were properly increased, albeit by incurring a slight rise in the total annual cost (TAC). This alternative method without a composition controller combined with the energy-saving PSDIC process provides a simple and effective control scheme in industrial production.
    The development of Fructus corni quality standard considering the effects of processing
    Xingchu Gong, Junlin Guo, Jingjing Pan, Zhenfeng Wu
    2021, 29(1):  77-84.  doi:10.1016/j.cjche.2020.04.006
    Abstract ( 137 )   PDF (1170KB) ( 49 )  
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    The quality standards for Fructus Corni have been established based on the effects of the manufacturing processes. Three critical process parameters (CPPs) of extraction, filtration, and concentration to prepare Fructus Corni concentrate were identified by Plackett-Burman design with a single batch of Fructus Corni, which were heating medium temperature, extraction time, and water addition. Morroniside yield, loganin yield, and dry matter yield were process critical quality attributes (CQAs). CPPs arranged with a Box-Behnken design were applied to treat different batches of Fructus Corni. After constructing a model that included CPPs, material properties, and process CQAs, loganin content was found to be the critical material attribute (CMA). The design space was calculated with a probability method. According to the limits of process CQAs, the minimum content of loganin in Fructus Corni was calculated with an error propagation method, which was 6.92 mg·g-1. When the content of loganin in Fructus Corni reaches up to 6.92 mg·g-1, the material is considered high-quality and is most suitable for the process. High-quality material can be used for production of Fructus Corni concentrate. This method can also be used to set material quality standards for other Chinese medicines.
    Spray coating of polysulfone/poly(ethylene glycol) block polymer on macroporous substrates followed by selective swelling for composite ultrafiltration membranes
    Dongwei Ma, Zhaogen Wang, Tao Liu, Yunxia Hu, Yong Wang
    2021, 29(1):  85-91.  doi:10.1016/j.cjche.2020.05.002
    Abstract ( 150 )   PDF (1899KB) ( 43 )  
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    Polysulfone (PSF) is extensively used for the production of ultrafiltration (UF) membranes thanks to its high strength, chemical stability, and good processibility. However, PSF is intrinsically hydrophobic, and hydrophilic modification is always required to PSF-based membranes if they are intended to be used in aqueous systems. Facile strategies to prepare hydrophilic PSF membranes are thus highly demanded. Herein we spray coat a PSF-based amphiphilic block polymer onto macroporous substrates followed by selective swelling to prepare flat-sheet PSF UF membranes. The polymer is a triblock polymer containing PSF as the majority middle block tethered with shorter block of polyethylene glycol (PEG) on both ends, that is, PEG-b-PSF-b-PEG. We use the technique of spray coating to homogeneously dispense diluted triblock polymer solutions on the top of macroporous supports, instantly resulting in uniform, defect-free polymer coating layers with the thickness down to ~1.2 μm. The bi-layered composite structures are then immerged in ethanol/acetone mixture to generate mesoscale pores in the coating layers following the mechanism of selective swelling-induced pore generation, thus producing composite membranes with the mesoporous triblock polymer coating as the selective layers. This facile strategy is free from additional hydrophilic modification and much smaller dosages of polymers are used compared to conventional casting methods. The pore sizes, porosities, hydrophilicity, and consequently the separation properties of the membranes can be flexibly tuned by changing the swelling duration and the composition of the swelling bath. This strategy combining spray coating and selective swelling is upscalable for the production of high-performance PSF UF membranes.
    Unravel the potential of zinc oxide nanoparticle-carbonized sawdust matrix for removal of lead (II) ions from aqueous solution
    Racheal Aigbe, Doga Kavaz
    2021, 29(1):  92-102.  doi:10.1016/j.cjche.2020.05.007
    Abstract ( 142 )   PDF (4490KB) ( 82 )  
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    Zinc oxide nanoparticles (ZnOnp) are molecular nanoparticles synthesized by a chemical precipitation method from zinc nitrate tetrahydrate and sodium hydroxide. Carbonized sawdust (CSD) was prepared from sawdust obtained from a local wood mill. The matrix of both provides a better material as an adsorbent. The present study applied the functionality of ZnOnp, CSD, and ZnOnp-CSD matrix as adsorbent materials for the removal of Pb (Ⅱ) ions from aqueous solution. The method of batch process was employed to investigate the potential of the adsorbents. The influence of pH, contact time, initial concentration of adsorbate, the dosage of adsorbents, and the temperature of adsorbate-adsorbent mixture on the adsorption capacity were revealed. The adsorption isotherm studies indicate that both Freundlich and Langmuir isotherms were suitable to express the experimental data obtained with theoretical maximum adsorption capacities (qm) of 70.42, 87.72, and 92.59 mg·g-1 for the adsorption of Pb (Ⅱ) ions onto ZnOnp, CSD, and ZnOnp-CSD matrix, respectively. The separation factors (RL) calculated showed that the use of the adsorbents for the removal of Pb (Ⅱ) ions is a feasible process with RL < 1. The thermodynamic parameters obtained revealed that the processes are endothermic, feasible, and spontaneous in nature at 25-50 ℃. Evaluation of the kinetic model elected that the processes agreed better with pseudo-second order where the values of rate constant (k2) obtained for the adsorption of Pb (Ⅱ) ions onto ZnOnp, CSD, and ZnOnp-CSD matrix are 0.00149, 0.00188, and 0.00315 g·mg-1·min-1, respectively. The reusability potential examined for four cycles indicated that the adsorbents have better potential and economic value of reuse and the ZnOnp-CSD matrix indicates improved adsorbent material to remove Pb (Ⅱ) ions from aqueous solution.
    Preparation of hybridizing zeolitic imidazolate frameworks with carboxymethylcellulose for adsorption separation of n-hexane/3-methylpentane
    Xiujuan Li, Le Chen, Dandan Zhu, Song Yang, Zhong Wu, Mingyang He, Zhihui Zhang, Qun Chen
    2021, 29(1):  103-109.  doi:10.1016/j.cjche.2020.05.023
    Abstract ( 136 )   PDF (1777KB) ( 49 )  
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    A novel ZIF-8-CMC hybrid material was fabricated from the hybridization of ZIF-8 and carboxymethylcellulose (CMC) by impregnation method for n-hexane/3-methylpentane separation. The surface properties of ZIF-8 were tailored by introducing CMC into ZIF-8 nanoparticles. In this work, adsorption separation of n-hexane (nHEX) and 3-methylpentane (3MP) on ZIF-8-CMC were investigated by batch vapor-phase adsorption and liquid-phase breakthrough adsorption. The adsorption selectivity of nHEX/3MP reversed from preferable adsorption of nHEX to preferable adsorption of 3MP upon the increasing of CMC containing in the hybrid materials. As the temperature increases, the adsorption amounts of nHEX and 3MP decrease. With the increasing of CMC contents, the nHEX uptake decreased, the uptake capacity of 3MP increased gradually. For liquid-phase breakthrough adsorption, the dynamic adsorption capacity of nHEX also decreased with the increasing of temperature.
    Design and synthesis of Al-MOF/PPSU mixed matrix membrane with pollution resistance
    Shujuan Xiao, Xiaowen Huo, Shuxin Fan, Kui Zhao, Shouwu Yu, Xiaoyao Tan
    2021, 29(1):  110-120.  doi:10.1016/j.cjche.2020.05.030
    Abstract ( 91 )   PDF (4059KB) ( 119 )  
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    To enhance the performance of the polyphenylene sulfone (PPSU) membrane, a novel mixed matrix membrane with hydrophilicity and antifouling properties was prepared. Using PPSU as the basic membrane material, polyvinyl pyrrolidone (PVP) as the porogen, N-Methyl pyrrolidone (NMP) as the solvent, and MOF-CAU-1 (Al4(OH)2(OCH3)4(H2N-BDC)3·xH2O) as the filler, PPSU/CAU-1 mixed matrix membrane (MMM) was prepared by an immersion precipitation and phase transformation technique. By changing the amount of MOF-CAU-1, the properties and performance of the MMM membrane were investigated in terms of hydrophilicity, pore morphology, surface roughness, and dye removal. The results show that the highest pure water flux of the mixed reached 47.9 L·m-2·h-1, when the CAU-1 addition amount was 1.0 wt%, which was 23% higher than that of the pure PPSU membrane. Both the rejection rate and the antifouling performance of the MMM membrane also noticeably improved.
    Implications from γ-globulin adsorption onto cation exchangers fabricated by sequential alginate grafting and sulfonation
    Xianxiu Li, Yan Sun, Xiaoyan Dong
    2021, 29(1):  121-125.  doi:10.1016/j.cjche.2020.06.017
    Abstract ( 116 )   PDF (669KB) ( 22 )  
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    Our previous work proved that high adsorption capacity and uptake rate of lysozyme were achieved on alginate (Alg)-grafted resin with an ionic capacity (IC) of 240 mmol·L-1 (Alg-FF-240). Moreover, the salt-tolerant feature of Alg-FF-230 was improved by using sequential alginate grafting and sulfonation strategy. Inspired by the enhanced adsorption performance of lysozyme, we have herein proposed to investigate the static and dynamic adsorption behaviors of γ-globulin on a series of Alg-grafted resins with different grafting densities and sulfonation degrees. The adsorption capacity of γ-globulin decreased with increasing alginate-grafting density (IC) from 160 to 230 mmol·L-1 at 0 mmol·L-1 NaCl because of the steric hindrance caused by the alginate-grafting layer. Effects of ionic strength (IS) indicated that the adsorption capacities of the resins with the IC value of 230-370 mmol·L-1 were much higher than CM Sepharose FF at 50-100 mmol·L-1 NaCl, and the uptake rate of Alg-FF-230 was about twice as much as that of CM Sepharose FF. This work demonstrated the important effects of alginate-grafting layer and IS in γ-globulin adsorption behavior, which would be helpful in the design of Alg-grafted resins and the selection of proper IS condition for protein purification.
    A further study of the kinetics and optimization of the essential oil hydrodistillation from lavender flowers
    Aleksandra Perović, Mihajlo Z. Stanković, Vlada B. Veljković, Milan D. Kostić, Olivera S. Stamenković
    2021, 29(1):  126-130.  doi:10.1016/j.cjche.2020.06.028
    Abstract ( 141 )   PDF (686KB) ( 86 )  
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    Hydrodistillation has commonly been used to recover essential oil from various plant materials, including lavender (Lavandula officinalis) flowers. The main objectives of the present study were to model the kinetics of the lavender essential oil (LEO) hydrodistillation using a phenomenological model, to evaluate the statistical significance of the hydromodule and hydrodistillation time on LEO yield combining a 42 full factorial design with the response surface methodology, to model statistically LEO yield by multiple non-linear regression and to determine the optimal process conditions that provided the maximum LEO yield. The fast-essential oil distillation (washing stage) in the initial period and the slow diffusion stage until the saturation occurring simultaneously were observed, justifying the use of the phenomenological model. With increasing the hydromodule, the saturation LEO yield and the washable fraction of the LEO decreased while the washing and diffusion rate constants increased. Knowledge of the LEO oil yield and the hydrodistillation kinetics is important from the techno-economical point of view.
    Desorption of Cl- from Mg-Al layered double hydroxide intercalated with Cl- using CO2 gas and water
    Tomohito Kameda, Hiroki Uchida, Shogo Kumagai, Yuko Saito, Keiichi Mizushina, Ichirou Itou, Tianye Han, Toshiaki Yoshioka
    2021, 29(1):  131-134.  doi:10.1016/j.cjche.2020.07.015
    Abstract ( 101 )   PDF (547KB) ( 47 )  
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    Mg-Al layered double hydroxide intercalated with CO32- (CO3·Mg-Al LDH) is effective for treating HCl exhaust gas. HCl reacts with CO32- in CO3·Mg-Al LDH, resulting in the formation of Cl·Mg-Al LDH. We propose that CO2 can be used for the desorption of Cl- from Cl·Mg-Al LDH to regenerate CO3·Mg-Al LDH. Herein, we studied the desorption of Cl- from Cl·Mg-Al LDH by adding water to Cl·Mg-Al LDH and blowing CO2 into it. We also analyzed the effects of temperature and water addition speed on the desorption of Cl- from Cl·Mg-Al LDH. Our results show that the added water adhered to Cl·Mg-Al LDH and that CO2 in the gaseous phase was dissolved in this adhered water, thus generating CO32-. Therefore, anion exchange occurred between CO32- and Cl- in the Cl·Mg-Al LDH, thus desorbing Cl-.
    The performance of activated carbon/NiFe2O4 magnetic composite to retain heavy metal ions from aqueous solution
    S. I. Moussa, M. M. S. Ali, Reda R. Sheha
    2021, 29(1):  135-145.  doi:10.1016/j.cjche.2020.07.036
    Abstract ( 156 )   PDF (2394KB) ( 39 )  
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    A novel magnetic activated carbon composite (AC/NiF) was synthesized by a precipitation method and applied in retention of Cu(Ⅱ), and Zn(Ⅱ) ions from aqueous solutions. The impact of different sorption parameters such as: equilibration time, solution pH value, competing cations and ionic strength on the amount sorbed of Cu(Ⅱ), and Zn(Ⅱ) was clarified. Results illustrated that the magnetic composite had retention ability towards both metal ions significantly higher than that of activated carbon (AC). The magnetic composite exhibited an affinity to adsorb Cu(Ⅱ) higher than Zn(Ⅱ) ions. The maximum sorption capacities (Qmax) of the applied magnetic composite (AC/NiF) towards Cu(Ⅱ) and Zn(Ⅱ) were 105.8 and 75.1 mg·g-1, respectively. Retention of Cu(Ⅱ) and Zn(Ⅱ) was proposed to be achieved though an ion exchange and surface adsorption in neutral conditions, while precipitation was believed to be the relevant mechanism in their removal from basic solutions. The kinetic studies showed that sorption process followed the kinetics of pseudo-second-order reactions with rate constant of 3 × 10-3 and 2 × 10-3 min-1 for sorption of Cu(Ⅱ) and Zn(Ⅱ) onto AC/NiF composite. Removal of Cu(Ⅱ) slightly decreased with increasing the ionic strength of aqueous solution, using NaCl as a background electrolyte. In contrast, presence of Mn(Ⅱ), Mg(Ⅱ) and Co(Ⅱ) in reaction solutions highly depressed the sorption of Cu(Ⅱ) and Zn(Ⅱ) with a competing efficiency followed the order: Mg(Ⅱ) > Mn(Ⅱ) > Co(Ⅱ).The magnetic composite was rapidly recovered from aqueous solution by an external magnetic field, and effectively regenerated using 0.1 mol·L-1 HCl and 0.1 mol·L-1 FeCl3 as eluents. Sorption of Cu(Ⅱ) and Zn(Ⅱ) onto the surface of AC/NiF composite occurred via a spontaneous reaction. And thermodynamically favorable process had ΔHo values of 30.9 kJ·mol-1 and 19.7 kJ·mol-1, respectively. The results confirm that the magnetic composite can be viewed as a promising novel composite opens new opportunities for the attainment of required adsorption and operative magnetic separation.
    Multivariate optimization of high removal of lead(II) using an efficient synthesized Ni-based metal-organic framework adsorbent
    Saeideh Dermanaki Farahani, Javad Zolgharnein
    2021, 29(1):  146-153.  doi:10.1016/j.cjche.2020.08.011
    Abstract ( 174 )   PDF (2491KB) ( 71 )  
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    A new metal-organic framework (MOF) with the chemical formula of [Ni2F2(4,4'-Bipy)2(H2O)2](VO3)2·8H2O was introduced to adsorb Pb(Ⅱ) with the highest capacity. The sorbent was characterized by thermogravimetric analysis (TGA), infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX), and elemental analysis. The optimum conditions were obtained by a face-centered central composite design (FCCD) as follows: adsorbent dosage (m)=1.2 mg, initial concentration of Pb(Ⅱ) (C)=390 mg·L-1, and pH=5. According to the Langmuir model (R2=0.9999), the maximum monolayer uptake capacity of lead(Ⅱ) is 2400.7 mg·g-1, which is the highest observed amount for lead(Ⅱ) adsorption. Neither of the old adsorbents for lead(Ⅱ) has the uptake capacity over 2000 mg·g-1. The model of pseudo-second-order describes well the process kinetics. The adsorption process of lead (Ⅱ) is independent of temperature changes. This compound can adsorb lead (Ⅱ) from tap water. In addition to introducing a new MOF with the highest uptake capacity for removal of Pb(Ⅱ) that is the outright novelty of this study, the concurrent modeling of both the removal percent (R) and the uptake capacity (q) is another important advantage. Because it achieves the more economical and favorable optimum conditions in comparison with the single optimization of each response.
    Growth process and short chain alcohol separation performance of fluoride-containing NaY zeolite membrane
    Xiaopan Chen, Meihua Zhu, Sitong Xiang, Tian Gui, Ting Wu, Yuqin Li, Na Hu, Izumi Kumakiri, Xiangshu Chen, Hidetoshi Kita
    2021, 29(1):  154-159.  doi:10.1016/j.cjche.2020.09.005
    Abstract ( 152 )   PDF (3420KB) ( 30 )  
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    Growth process of the NaY zeolite membranes was investigated by fluoride-containing precursor synthesis gel. Compared with the fluoride-free precursor synthesis gel, the irregular NaY zeolite crystals were dissolved into amorphous by the fluoride-containing precursor synthesis gel initially, the amorphous contained the Y-type zeolite characteristic bands by the IR characterization. The fine square NaY zeolite crystals arose from the amorphous, which were accumulated and gradually grew into a dense NaY zeolite layer on the support surface after 6.5 h. Because the excessive NaY zeolites were dissolved by the strong alkaline and fluoride-containing precursor synthesis gel, there was plenty of amorphous on NaY zeolites layer for prolonging the crystallization time. The as-synthesized NaY zeolite membranes had a good separation performance and repeatability for separation of 10 wt% methanol (MeOH)/methyl methacrylate (MMA) mixture by pervaporation, the flux and separation factor were (1.27 ± 0.07) kg·m-2·h-1 and (4900 ± 1500) at 323 K, respectively. Besides, the NaY zeolite membranes were applied to separate the other short chain alcohol from the various alcohol/organic ester and alcohol/organic ether mixtures, the NaY zeolite membranes showed high short chain alcohol perm-selectivity.
    Enhancement of CO2 capture and microstructure evolution of the spent calcium-based sorbent by the self-reactivation process
    Rongyue Sun, Hongliang Zhu, Rui Xiao
    2021, 29(1):  160-166.  doi:10.1016/j.cjche.2020.09.025
    Abstract ( 78 )   PDF (1567KB) ( 23 )  
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    The effect of self-reactivation on the CO2 capture capacity of the spent calcium based sorbent was investigated in a dual-fixed bed reactor. The sampled sorbents from the dual-fixed bed reactor were sent for XRD, SEM and N2 adsorption analysis to explain the self-reactivation mechanism. The results show that the CaO in the spent sorbent discharged from the calciner absorbs the vapor in the air to form Ca(OH)2 and further Ca(OH)2·2H2O under environmental conditions, during which process the CO2 capture capacity of the spent sorbent can be self-reactivated. The microstructure of the spent sorbent is improved by the self-reactivation process, resulting in more porous microstructure, higher BET surface area and pore volume. Compared with the calcined spent sorbent that has experienced 20 cycles, the pore volume and BET surface area are increased by 6.69 times and 56.3% after self-reactivation when φ=170%. The improved microstructure makes it easier for the CO2 diffusion and carbonation reaction in the sorbent. Therefore, the CO2 capture capacity of the spent sorbent is enhanced by self-reactivation process. A self-reactivation process coupled with calcium looping process was proposed to reuse the discharged spent calcium based sorbent from the calciner. Higher average carbonation conversion and CO2 capture efficiency can be achieved when self-reactivated spent sorbent is used as supplementary sorbent in the calciner rather than fresh CaCO3 under the same conditions.
    Catalysis, Kinetics and Reaction Engineering
    Efficient elimination and detection of phenolic compounds in juice using laccase mimicking nanozymes
    Hui Huang, Lulu Lei, Juan Bai, Ling Zhang, Donghui Song, Jingqi Zhao, Jiali Li, Yongxin Li
    2021, 29(1):  167-175.  doi:10.1016/j.cjche.2020.04.012
    Abstract ( 137 )   PDF (1671KB) ( 44 )  
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    Residual phenols in the juice can cause turbidity and affect its sensory quality. Laccase is used to remove phenolic compounds from fruit juices. In order to overcome the shortcomings of natural laccase instability and high cost, in this work, we prepared a laccase mimic enzyme based on copper ion and adenosine monophosphate (AMP-Cu nanozymes). At the same mass concentration (1 mg·ml-1), the catalytic activity of the nanozyme is about 15 times that of laccase. The AMP-Cu nanozymes had a higher Vmax and a lower Km than laccase. The laccase mimic enzyme had a good stability under the condition of 30-90 ℃ and pH > 6. It also maintained high catalytic activity at high salt concentrations and 9 days storage time. Furthermore, the AMP-Cu nanozymes maintained an initial catalytic activity of about 80% after six consecutive cycles of reaction. The linear range of detection of phenolic compounds by AMP-Cu nanozymes was 0.1-100 μmol·L-1 with a detection limit of 0.033 μmol·L-1. The phenol removal rate of AMP-Cu nanozymes was much higher than that of laccase under different reaction times. When the reaction was performed for 5 h, the phenol removal rate of the fruit juice by AMP-Cu nanozymes was about 65%. The efficient removal of phenolic compounds from different juices by AMP-Cu nanozymes indicates that they have good application prospect in the food juice industry.
    Density functional theory and kinetic Monte Carlo simulation study the strong metal-support interaction of dry reforming of methane reaction over Ni based catalysts
    Xueyan Zou, Xiaodong Li, Xiaoyu Gao, Zhihua Gao, Zhijun Zuo, Wei Huang
    2021, 29(1):  176-182.  doi:10.1016/j.cjche.2020.05.009
    Abstract ( 175 )   PDF (1839KB) ( 83 )  
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    Oxide supports modify electronic structures of supported metal nanoparticles, and then affect the catalytic activity associated with the so-called strong metal-support interaction (SMSI). We herein report the strong influence of SMSI employing Ni4/α-MoC(111) and defective Ni4/MgO(100) catalysts used for dry reforming of methane (DRM, CO2 + CH4 → 2CO + 2H2) by using density functional theory (DFT) and kinetic Monte Carlo simulation (KMC). The results show that α-MoC(111) and MgO(100) surface have converse electron and structural effect for Ni4 cluster. The electrons transfer from α-MoC(111) surface to Ni atoms, but electrons transfer from Ni atoms to MgO(100) surface; an extensive tensile strain is greatly released in the Ni lattice by MgO, but the extensive tensile strain is introduced in the Ni lattice by α-MoC. As a result, although both catalysts show good stability, H2/CO ratio on Ni4/α-MoC(111) is obviously larger than that on Ni4/MgO(100). The result shows that Ni/α-MoC is a good catalyst for DRM reaction comparing with Ni/MgO catalyst.
    Kinetic study for the oxidation of cyclohexanol and cyclohexanone with nitric acid to adipic acid
    Detao Pan, Guangxiao Li, Yuanhai Su, Huilong Wei, Zhenghong Luo
    2021, 29(1):  183-189.  doi:10.1016/j.cjche.2020.05.011
    Abstract ( 135 )   PDF (1217KB) ( 100 )  
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    The adipic acid is an important intermediate in the production of nylon, polyurethane and polyester resins. The industrial approach for preparing adipic acid is through the liquid catalytic oxidation of KA oil with nitric acid. In this work, a comprehensive model is developed for this reaction based on the kinetic study conducted in a continuous flow tubular reactor. The kinetic model fits well with the experimental results across the experimental conditions, and the average relative error between the calculated and experimental values is 5.7%. Results show that there was an induction period at the early stage of reaction. Moreover, it is found that at temperature range of 328-358 K, the formation rate of adipic acid strongly dependents on the temperature and nitric acid concentration. The developed model is used to predict the yield of adipic acid at 359-368 K. The work in this study could provide much knowledge for industrial tubular reactor design.
    Catalytic oxidation of low concentration formaldehyde over Pt/TiO2 catalyst
    Yuan Su, Keming Ji, Jiayao Xun, Kan Zhang, Ping Liu, Liang Zhao
    2021, 29(1):  190-195.  doi:10.1016/j.cjche.2020.04.024
    Abstract ( 92 )   PDF (1147KB) ( 72 )  
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    Formaldehyde (HCHO) is an important indoor pollutant. Catalytic oxidize low concentration HCHO is an effective way to eliminate indoor pollution. In this study, a series of Pt/TiO2 catalysts are prepared by impregnation and reduced by NaBH4. The effects of loading amount of Pt and crystal type of TiO2 on the physical and chemical properties and the catalytic performance in HCHO oxidation reaction are investigated. The results show that the quantity of active site and the oxygen vacancy of catalysts increased with increasing Pt content, which is beneficial to promote the further performance of catalysts. Nevertheless, with the further rises of Pt content, the specific surface area further decreases, and the proportion of Pt2+ species on the catalyst surface which is significant to catalytic properties also decreases, causing catalytic performance decreases. Compared with the catalyst supporting on rutile, the Pt/a-TiO2 catalyst supporting on anatase has larger specific surface area, more Pt2+ phase and easier to form oxygen vacancy in the support, which cause better catalytic performance. The catalyst with Pt content of 0.1 wt% and supported by anatase TiO2 has the best catalytic performance. The HCHO conversion efficiency reaches 98% and 100% at 50 ℃ and 100 ℃, and the stabilization time is longer than 140 h.
    High nitrogen carbon material with rich defects as a highly efficient metal-free catalyst for excellent catalytic performance of acetylene hydrochlorination
    Fangjie Lu, Dong Xu, Yusheng Lu, Bin Dai, Mingyuan Zhu
    2021, 29(1):  196-203.  doi:10.1016/j.cjche.2020.06.008
    Abstract ( 198 )   PDF (2121KB) ( 28 )  
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    In this work, we developed a simple strategy to synthesize a carbon material with high nitrogen and rich carbon defects. Our approach polymerized diaminopyridine (DAP) and ammonium persulfate (APS). Following a range of different temperature pyrolysis approaches, the resulting rough surface was shown to exhibit edge defects due to N-doping on graphite carbon. A series of catalysts were evaluated using a variety of characterization techniques and tested for catalytic performance. The catalytic performance of the N-doped carbon material enhanced alongside an increment in carbon defects. The NC-800 catalyst exhibited outstanding catalytic activity and stability in acetylene hydrochlorination (C2H2 GHSV=30 h-1, at 220 ℃, the acetylene conversion rate was 98%), with its stability reaching up to 450 h. Due to NC-800 having a nitrogen content of up to 13.46%, it had the largest specific surface area and a high defect amount, as well as strong C2H2 and HCl adsorption. NC-800 has excellent catalytic activity and stability to reflect its unlimited potential as a carbon material.
    Photochemical microfluidic synthesis of vitamin D3 by improved light sources with photoluminescent substrates
    Wenhao Niu, Yuanzhi Zheng, Ying Li, Le Du, Wei Liu
    2021, 29(1):  204-211.  doi:10.1016/j.cjche.2020.07.016
    Abstract ( 99 )   PDF (4624KB) ( 38 )  
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    This study presents a novel technique for the controllable preparation of photoluminescent substrates to enhance the photochemical microfluidic synthesis of vitamin D3. The dip-coating method to prepare the substrates was experimentally optimized, and the corresponding emission behaviors were systematically investigated. The substrates were successfully used to enhance the ultraviolet B (UVB) emission of a low-power light source (e.g., an 8 W lamp), whose UVB emission intensity was increased by approximately 11 times. By virtue of the novel light source, the productivity of a single set of photochemical microreactor with a 12-meter-long channel (0.6 mm i.d.) was increased to 1.83 kg·a-1, which was 42% higher than that of a 100 W lamp, and no cooling devices were used. The method is simple and has great potential to replace traditional medium-pressure mercury lamps for UVB-irradiated photochemical reactions.
    Upgrading Siberian (Russia) crude oil by hydrodesulfurization: Kinetic parameter estimation in a trickle-bed reactor
    Kening Sun, Xixi Ma, Ruijun Hou
    2021, 29(1):  212-220.  doi:10.1016/j.cjche.2020.07.021
    Abstract ( 100 )   PDF (1269KB) ( 87 )  
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    Hydrodesulfurization (HDS) of sour crude oil is an effective way to address the corrosion problems in refineries and is an economic way to process sour crude oil in an existing refinery built for sweet oil. Siberian crude oil transported through the Russia-China pipeline could be greatly sweetened and could be refined directly in local refinery designed for Daqing crude oil after the effective HDS treatment. In this study, the HDS of Siberian crude oil was carried out in a continuous flow isothermal trickle-bed reactor over Ni-Mo/γ-Al2O3. The effects of temperature, pressure and LHSV were investigated in the ranges of 320-360 ℃, 3-5 MPa and 0.5-2 h-1, keeping constant hydrogen to oil ratio at 600 L·L-1. The HDS conversion could be up to 92.89% at the temperature of 360 ℃, pressure of 5 MPa, and LHSV of 0.5 h-1, which is sufficient for local refineries (> 84%). A three phase heterogeneous model was established to analyze the performance of the trickle-bed reactor based on the two-film theory using Langmuir-Hinshelwood mechanism. The order of sulfur component is estimated as 1.28, and the order of hydrogen is 0.39. By simulating the reactor using the established model, the concentration of H2, H2S and sulfur along the catalyst bed is discussed. The model is significantly useful for industrial application with respect to reactor analysis, optimization and reactor design, and can provide further insight of the HDS of Siberian crude oil.
    Homogeneous Co3O4 film electrode with enhanced oxygen evolution electrocatalysis via surface reduction
    Xiang Li, Bo Yang, Yaqin Wu, Saisai Lin, Lin Zhang
    2021, 29(1):  221-227.  doi:10.1016/j.cjche.2020.08.008
    Abstract ( 101 )   PDF (2433KB) ( 32 )  
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    Homogeneous NaBH4-reduced Co3O4 thin film electrodes with enhanced oxygen evolution electrocatalysis were obtained via a controlled-synthesis route. Firstly CoOx colloids were synthesized via ethylene glycol solvothermal method and cast on conductive glass substrates. The oxygen evolution reaction (OER) electrocatalysis of these as-prepared Co3O4 thin films were then significantly enhanced via a simple surface reduction by NaBH4 solution. The OER catalytic performance of the NaBH4-reduced thin films was strongly dependent on the NaBH4 concentration. The use of NaBH4-reduced thin film electrodes for OER in alkaline solution supported higher current density and consequently negative shifts of the onset potential compared to that of the pristine. The optimal B12.5, 20-Co3O4 thin films exhibited excellent OER catalytic performances: At the current density of 10 mA·cm-2, a low overpotential of 365 mV and a small Tafel slope of 59.0 mV·dec-1 were observed. In addition, these B12.5, 20-Co3O4 thin film electrodes possessed good stability that can well recover its OER performance in a 24-h chronoamperometric stability test.
    Process Systems Engineering and Process Safety
    Numerical study on effects of the cofferdam area in liquefied natural gas storage tank on the leakage and diffusion characteristics of natural gas
    Zirong Lin, Shuangfeng Wang, Shuxun Fu, Jiepeng Huo
    2021, 29(1):  228-241.  doi:10.1016/j.cjche.2020.07.049
    Abstract ( 134 )   PDF (12761KB) ( 18 )  
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    The leakage and diffusion characteristics of natural gas were investigated in the condition of the leakage of liquefied natural gas (LNG) in the storage tank. Fluent was adopted to simulate the process in a series of three-dimension unsteady state calculations. The effects of different heights of the cofferdam (1.0 m, 2.0 m and 3.0 m), wind directions, ambient temperature, leakage location, leakage volume on the diffusion process of natural gas were investigated. The diffusion characteristics of the natural gas clouds over cofferdam were found. Under windless condition, when the gas clouds met, the gas clouds rose due to the collision, which made them easier to cross the cofferdam and spread out. The higher the ambient temperature was, the higher the gas concentration around the cofferdam was, and the smaller the gas concentration difference was. When the leakage occurred, the higher cofferdam was more beneficial to delay the outward diffusion of gas clouds. However, when the leakage stopped, the higher cofferdam went against the dissipation of gas clouds. Under windy condition, the time to form stable leakage flow field was faster than that of windless, and the lower cofferdam further reduced this time. Therefore, considering the effect of barrier and dissipation, it was suggested that the rational height of cofferdam should be designed in the range of 1.0 m to 2.0 m. In case of emergency, the leakage of gas should be deduced reasonably by combining the measurement of gas concentration with the rolling of gas clouds. When windless, the leakage area should be entered between the overflows of gas clouds.
    Optimization and mechanisms analysis of indigo dye removal using continuous electrocoagulation
    Kamel Hendaoui, Malika Trabelsi-Ayadi, Fadhila Ayari
    2021, 29(1):  242-252.  doi:10.1016/j.cjche.2020.07.065
    Abstract ( 146 )   PDF (1866KB) ( 108 )  
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    Electrocoagulation (EC) is among the most effective techniques that remove color and decontaminate effluent. Coagulants are delivered in situ by anode corrosion. In this research, indigo dye removal using iron electrodes in continuous electrocoagulation process and the responsible species for decolorization were investigated. The Response Surface Methodology (RSM) was used to optimize the process parameters. The finding in this study shows that at fixed conductivity at 15,000 μS·cm-1, the neutral conditions (pH from 6 to 8), the low absorbance, the low flow rate and the high voltage level enhance the color removal efficiency. The high R2 value of 97.8% and ANOVA analyses show a good correlation between the experimental and predicted results. Under the optimum conditions, which are pH of 7.5, solution concentration of 60 mg·L-1, inlet flow rate of 2 L·min-1 and voltage of 47 V, the predicted decolorization of 94.083% was achieved at 93.972% with a total cost of 0.0927 USD·m-3 of treated effluent. At the optimum pH (7.5), the zeta potential value (-4 mV) of the effluent during EC match with the one of iron Ⅲ hydroxide. The dye removal is ensured thanks to physical adsorption and flocculation. The results exposed in this work prove that the continuous electrocoagulation process could be successfully used for indigo dye removal at industrial scale.
    Improved process monitoring using the CUSUM and EWMA-based multiscale PCA fault detection framework
    Muhammad Nawaz, Abdulhalim Shah Maulud, Haslinda Zabiri, Syed Ali Ammar Taqvi, Alamin Idris
    2021, 29(1):  253-265.  doi:10.1016/j.cjche.2020.08.035
    Abstract ( 125 )   PDF (3533KB) ( 137 )  
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    Process monitoring techniques are of paramount importance in the chemical industry to improve both the product quality and plant safety. Small or incipient irregularities may lead to severe degradation in complex chemical processes, and the conventional process monitoring techniques cannot detect these irregularities. In this study to improve the performance of monitoring, an online multiscale fault detection approach is proposed by integrating multiscale principal component analysis (MSPCA) with cumulative sum (CUSUM) and exponentially weighted moving average (EWMA) control charts. The new Hotelling's T2 and square prediction error (SPE) based fault detection indices are proposed to detect the incipient irregularities in the process data. The performance of the proposed fault detection methods was tested for simulated data obtained from the CSTR system and compared to that of conventional PCA and MSPCA based methods. The results demonstrate that the proposed EWMA based MSPCA fault detection method was successful in detecting the faults. Moreover, a comparative study shows that the SPE-EWMA monitoring index exhibits a better performance with lower values of missed detections ranging from 0% to 0.80% and false alarms ranging from 0% to 21.20%.
    Enhanced temperature difference control of distillation columns based on the averaged absolute variation magnitude
    Yang Yuan, Kejin Huang, Xing Qian, Haisheng Chen, Lijing Zang, Liang Zhang
    2021, 29(1):  266-278.  doi:10.1016/j.cjche.2020.08.051
    Abstract ( 110 )   PDF (3046KB) ( 24 )  
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    Temperature difference control (TDC) schemes can clearly suppress the adverse influence of pressure variations on product quality control of various distillation columns (DCs) by employing temperature differences (TDs) between the sensitive stage temperature (TS) and reference stage temperature (TR), i.e., TS-TR, to infer the controlled product qualities. However, because the TDC scheme has failed to specially take the corresponding relationship between the TD employed in each control loop and the controlled product quality into account, it may suffer from relatively large steady-state errors in the controlled product qualities. To address this problem, an enhanced TDC (ETDC) scheme is proposed in the current article, in which an enhanced TD (ETD), i.e., TS-α×TR, is employed to replace the conventional TD for each control loop. While the locations of the sensitive and reference stages of the ETD are respectively determined according to sensitivity analysis and SVD analysis, the adjusted coefficient α is set to be the ratio between the averaged absolute variation magnitudes (AAVMs) of the TS and TR so that the relationship between the TS and TR can be appropriately coordinated. With reference to the operations of three different distillation systems, i.e., one conventional DC distilling an ethanol (E)/butanol (B) binary mixture, one conventional DC distilling an E/propanol (P)/B ternary mixture, and one dividing-wall distillation column distilling an E/P/B ternary mixture, the performance of the ETDC scheme is assessed by compared with the conventional TDC scheme and the double TD control (DTDC) scheme. The dynamic simulation results show that the ETDC scheme is better than the conventional TDC scheme with reduced steady-state errors in the controlled product qualities and improved dynamic responses, and is comparable with the DTDC scheme despite the less temperature measurements are employed.
    Chemical Engineering Thermodynamics
    Interaction of tetradecyltrimethylammonium bromide with bovine serum albumin in different compositions: Effect of temperatures and electrolytes/urea
    Joynal Abedin, Shamim Mahbub, Mohammad Majibur Rahman, Anamul Hoque, Dileep Kumar, Javed Masood Khan, Ahmed M. El-Sherbeeny
    2021, 29(1):  279-287.  doi:10.1016/j.cjche.2020.07.062
    Abstract ( 130 )   PDF (670KB) ( 73 )  
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    Herein, the interaction of a protein, bovine serum albumin (BSA), with tetradecyltrimethylammonium bromide (TTAB, a cationic surfactant), has been investigated using the conductivity measurement technique in pure water and some sodium salts (NaCl, Na2SO4, Na2CO3, and Na3PO4) solutions at temperature range of 295.15-320.15 K. Results reveal that, in the plot of specific conductivity versus the concentration of TTAB, only a single critical micelle concentration (cmc) was found for the TTAB + BSA mixed system in all solvents media studied. The addition of BSA in aqueous TTAB solution, the value of cmc undergoes a change from its pure form, which indicates the presence of strong interaction operating between the BSA and TTAB molecules. In aqueous system, the cmc values of the TTAB + BSA mixtures are obtained higher compared to the values found for single TTAB surfactant. However, the addition of salt decreases the cmc value of mixed TTAB + BSA system. The values of cmc of the BSA + TTAB mixed system at 310.15 K and 1.00 mmol·kg-1 ionic strength of salt followed the order: cmcNa2CO3 > cmcNa3PO4 > cmcNaCl > cmcNa2SO4. The cmc values of TTAB + BSA mixture were found to be lowered in urea solution within the concentrations studied. The values of degree of dissociation (α) and fraction of counter ion binding (β) were found to be dependent on additives and temperature. The free energy of micellization (△Gmo) is negative for all the systems, which manifests that the micellization phenomenon is energetically spontaneous. The enhancement of the negative value of △Gmo in aqueous salt solutions reveals an increase of spontaneity of the TTAB + BSA micellization process. The values of △Gmo also reveal that the spontaneity of micelle formation is enhanced at higher temperatures in all media studied. The values of free energy of transfer (△Gm, to) were also determined for numerous solvent media used in the present study and described with appropriate reasoning.
    Designing and optimizing a parallel neural network model for predicting the solubility of diosgenin in n-alkanols
    Huichao Lv, Dayong Tian
    2021, 29(1):  288-294.  doi:10.1016/j.cjche.2020.09.009
    Abstract ( 81 )   PDF (1199KB) ( 29 )  
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    Accurate estimation of the solubility of a chemical compound is an important issue for many industrial processes. To overcome the defects of some thermodynamic models and simple correlations, a parallel neural network (PNN) model was conceived and optimized to predict the solubility of diosgenin in seven n-alkanols (C1-C7). The linear regression analysis of the parity plots indicates that the PNN model can give more accurate descriptions of the solubility of diosgenin than the ordinary neural network (ONN) model. The comparison of the average root mean square deviation (RMSD) shows that the suggested model has a slight advantage over the thermodynamic NRTL model in terms of the calculating precision. Moreover, the PNN model can reflect the effects of the temperature and the chain length of the alcohol solvent on the solution behavior of diosgenin correctly and can estimate its solubility in the n-alkanols with more carbon atoms.
    Displacement of shale gas confined in illite shale by flue gas: A molecular simulation study
    Tong Tao, Shitao Wang, Yixin Qu, Dapeng Cao
    2021, 29(1):  295-303.  doi:10.1016/j.cjche.2020.09.015
    Abstract ( 83 )   PDF (3055KB) ( 30 )  
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    The shale gas is an unconventional supplementary energy to traditional fossil energy, and is stored in layered rocks with low permeability and porosity, which leads to the difficulty for exploration of shale gas. Therefore, using CO2 gas to displace shale gas has become an important topic. In this work, we use molecular simulations to study the displacement of shale gas by flue gas rather than CO2, in which flue gas is modeled as a binary mixture of CO2 and N2 and the shale model is represented by inorganic Illite and organic methylnaphthalene. CH4 is used as a shale gas model. Compared to the pure CO2, flue gas is easily available and the cost of displacement by flue gas would become lower. Results indicate that the pore size of shale is an important factor in the process of displacing shale gas and simultaneously sequestrating flue gas, while the flue gas N2-CO2 ratio shows a small effect on the process of CH4 displacement, because the high partial pressure of flue gas is the main driving force for displacement of shale gas. Moreover, the geological condition also has a significant effect on the process of CH4 displacement by flue gas. Therefore, we suggest that the burial depth of 1 km is suitable operation condition for shale gas displacement. It is expected that this work provides a useful guidance for exploitation of shale gas and sequestration of greenhouse gas.
    Special Topic: Biocatalysis
    Preface to special issue of biocatalysis
    Jun Ge, Huilei Yu
    2021, 29(1):  304-304.  doi:10.1016/j.cjche.2020.06.034
    Abstract ( 48 )   PDF (843KB) ( 26 )  
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    Asymmetric bioreduction of γ- and δ-keto acids by native carbonyl reductases from Saccharomyces cerevisiae
    Chunlei Ren, Tao Wang, Xiaoyan Zhang, Jiang Pan, Jianhe Xu, Yunpeng Bai
    2021, 29(1):  305-310.  doi:10.1016/j.cjche.2020.07.014
    Abstract ( 56 )   PDF (1631KB) ( 39 )  
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    Optically pure (R)-γ- and (R)-δ-lactones can be prepared by intramolecular cyclization of chiral hydroxy acids/esters reduced asymmetrically from γ- and δ-keto acids/esters using Saccharomyces cerevisiae (S. cerevisiae) as a whole-cell biocatalyst. However, some of the enzymes catalyzing these reactions in S. cerevisiae are still unknown up to date. In this report, two carbonyl reductases, OdCR1 and OdCR2, were successfully discovered, and cloned from S. cerevisiae using a genome-mining approach, and overexpressed in Escherichia coli (E. coli). Compared with OdCR1, OdCR2 can reduce 4-oxodecanoic acid and 5-oxodecanoic acid asymmetrically with higher stereoselectivity, generating (R)-γ-decalactone (99% ee) and (R)-δ-decalactone (98% ee) in 85% and 92% yields, respectively. This is the first report of native enzymes from S. cerevisiae for the enzymatic synthesis of chiral γ- and δ-lactones which is of wide uses in food and cosmetic industries.
    Immobilization of trophic anaerobic acetogen for semi-continuous syngas fermentation
    Lijuan Zhang, Peng Hu, Jiang Pan, Huilei Yu, Jianhe Xu
    2021, 29(1):  311-316.  doi:10.1016/j.cjche.2020.07.041
    Abstract ( 58 )   PDF (1167KB) ( 17 )  
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    The massive consumption of fossil energy forces people to find new sources of energy. Syngas fermentation has become a hot research field as its high potential in renewable energy production and sustainable development. In this study, trophic anaerobic acetogen Morella thermoacetica was successfully immobilized by calcium alginate embedding method. The ability of the immobilized cells on production of acetic acid through syngas fermentation was compared in both airlift and bubble column bioreactors. The bubble column bioreactor was selected as the better type of bioreactor. The production of acetic acid reached 32.3 g·L-1 in bubble column bioreactor with a space-time yield of 2.13 g·L-1·d-1. The immobilized acetogen could be efficiently reused without significant lag period, even if exposed to air for a short time. A semi-continuous syngas fermentation was performed using immobilized cells, with an average space-time acetic acid yield of 3.20 g·L-1·d-1. After 30 days of fermentation, no significant decrease of the acetic acid production rate was observed.
    An enzyme-loaded reactor using metal-organic framework-templated polydopamine microcapsule
    Jing Wang, Yongqin Lv
    2021, 29(1):  317-325.  doi:10.1016/j.cjche.2020.07.042
    Abstract ( 69 )   PDF (3461KB) ( 37 )  
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    Ultrathin polydopamine microcapsules with hierarchical structure and porosity were prepared for the immobilization of multienzymes using metal-organic framework (MOF) as the template. The multienzyme/MOF composite was first prepared using a “one-pot” co-precipitation approach via the coordination and self-assembly of zinc ions and 2-methylimidazole in the presence of enzymes. The obtained nanoparticles were then coated with polydopamine thin layer through the self-polymerization of dopamine under alkaline condition. The polydopamine microcapsules with an ultrathin shell thickness of ~48 nm were finally generated by removing the MOF template at acidic condition. Three enzymes were encapsulated in PDA microcapsules including carbonic anhydrase (CA), formate dehydrogenase (FateDH), and glutamate dehydrogenase (GDH). FateDH that catalyzed the main reaction of CO2 reduction to formic acid retained 94.7% activity of equivalent free FateDH. Compared with free multienzymes, the immobilized ones embedded in PDA microcapsules exhibited 4.5-times higher of formate production and high catalytic efficiency with a co-factor-based formate yield of 342%.
    Simulation study on the gasification process of Ningdong coal with iron-based oxygen carrier
    Fei Xie, Mei An, Ping Li, Xiude Hu, Hongcun Bai, Qingjie Guo
    2021, 29(1):  326-334.  doi:10.1016/j.cjche.2020.05.017
    Abstract ( 52 )   PDF (1938KB) ( 19 )  
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    Chemical looping gasification (CLG) of Ningdong coal by using Fe2O3 as the oxygen carriers (OCs) was studied, and the gasification characteristics were obtained. A computation fluid dynamics (CFD) model based on Eulerian‐-Lagrangian multiphase framework was established, and a numerical simulation the coal chemical looping gasification processes in fuel reactor (FR) was investigated. In addition, the heterogeneous reactions, homogeneous reactions and Fe2O3 oxygen carriers' reduction reactions were considered in the gasification process. The characteristics of gas flow and gasification in the FR were analyzed and it was found that the experiment results were consistent with the simulation values. The results show that when the O/C mole rate was 0.5:1, the gasification temperature was 900 ℃ and the water vapor volume flow rate was 2.2 ml·min-1, the mole fraction of syngas reached a maximum value of the experimental result and simulation value were 71.5% and 70.2%, respectively. When the O/C mole rate was 0.5:1, the gasification temperature was 900 ℃, and the water vapor volume flow was 1.8 ml·min-1; the gasification efficiency reached the maximum value was 62.2%, and the maximum carbon conversion rate was 84.0%.
    Chemical looping gasification of sewage sludge using copper slag modified by NiO as an oxygen carrier
    Nanhang Dong, Ruiqiang Huo, Ming Liu, Lisheng Deng, Zhengbing Deng, Guozhang Chang, Zhen Huang, Hongyu Huang
    2021, 29(1):  335-343.  doi:10.1016/j.cjche.2020.09.007
    Abstract ( 93 )   PDF (1137KB) ( 38 )  
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    Chemical looping gasification (CLG) provides a novel approach to dispose the sewage sludge. In order to improve the reactivity of the calcined copper slag, NiO modification is considered as one of the good solutions. The copper slag calcined at 1100 ℃ doped with 20 wt% NiO (Ni20-CS) was used as an oxygen carrier (OC) in sludge CLG in the work. The modification of NiO can evidently enhance the reactivity of copper slag to promote the sludge conversion, especially for sludge char conversion. The carbon conversion and valid gas yield (Vg) increase from 67.02% and 0.23 m3·kg-1 using the original OC to 78.34% and 0.29 m3·kg-1 using the Ni20-CS OC, respectively. The increase of equivalent coefficient (Ω) facilitates the sludge conversion and a suitable Ω value is determined at 0.47 to obtain the highest valid gas yield (0.29 m3·kg-1). A suitable steam content is assigned at 27.22% to obtain the maximum carbon conversion of 87.09%, where an acceptable LHV of 12.63 MJ·m-3 and Vg of 0.39 m3·kg-1 are obtained. Although the reactivity of Ni20-CS OC gradually decreases with the increase in cycle numbers because of the generation of NiFe2O4-δ species, the deposition of sludge ash containing many metallic elements is beneficial to the sludge conversion. As a result, the carbon conversion shows a slight uptrend with the increase of cycle numbers in sludge CLG. It indicates that the Ni20-CS sample is a good OC for sludge CLG.
    Study of sodium lignosulfonate prepare low-rank coal-water slurry: Experiments and simulations
    Lin Li, Chuandong Ma, Mengyu Lin, Mingpu Liu, Hao Yu, Qingbiao Wang, Xiaoqiang Cao, Xiaofang You
    2021, 29(1):  344-353.  doi:10.1016/j.cjche.2020.07.064
    Abstract ( 69 )   PDF (1495KB) ( 28 )  
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    The effect of sodium lignosulfonate (SL) as additive on the preparation of low-rank coal-water slurry (LCWS) was studied by experiments and molecular dynamics (MD) simulations. The experimental results show that the appropriate amount of additives is beneficial to reduce the viscosity of LCWS and increase the slurry concentration. Adsorption isotherm studies showed that SL conforms to single-layer adsorption on the coal surface, and △Gads0 was negative, proving that the reaction was spontaneous. Zeta potential measurements showed that SL increased the negative charge on coal. FTIR scanning and XPS wide-range scanning were performed on the coal before and after adsorption, and it was found that the content of oxygen functional groups on coal increased after adsorption. Simulation results show that when a large number of SL molecules exist in the solution, some SL molecules will bind to hydrophobic hydrocarbon groups on coal. The rest of the SL molecules, their hydrophobic alkyl tails, come into contact with each other and aggregate in solution. The agglomeration of SL molecules and the surface of coal with static electricity will also produce electrostatic interaction, which is conducive to the even dispersion of coal particles. The results of mean square displacement (MSD) and self-diffusion coefficient (D) show that the addition of SL reduces the diffusion rate of water molecules. Simulation results correspond to experimental results, indicating that MD simulation is accurate and feasible.
    Design and analysis of dual mixed refrigerant processes for high-ethane content natural gas liquefaction
    Ting He, Wensheng Lin
    2021, 29(1):  354-364.  doi:10.1016/j.cjche.2020.09.019
    Abstract ( 56 )   PDF (1781KB) ( 124 )  
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    Recovery and purification of ethane has a significant impact on economic benefit improvement of the high-ethane content natural gas. However, current LNG-NGL integrated processes mainly focus on conventional natural gas, which are not applicable to natural gas with high ethane content. To fill this gap, three dual mixed refrigerant processes are proposed for simulation study of high-ethane content natural gas liquefaction. The proposed processes are optimized by a combination method of sequence optimization and genetic algorithm. Comparatively analysis is conducted to evaluate the three processes from the energetic and exergetic points of view. The results show that the power consumption of Process 3 which compressing natural gas after distillation is the lowest. For safety or other considerations, some common compositions of the mixed refrigerant may need to be removed under certain circumstances. Considering this, case studies of mixed refrigerant involving six composition combinations are carried out to investigate the effects of refrigerant selection on the process performance.
    Experimental and modeling study of the kinetics of methane hydrate formation and dissociation
    Vafa Feyzi, Vahid Mohebbi
    2021, 29(1):  365-374.  doi:10.1016/j.cjche.2020.08.045
    Abstract ( 59 )   PDF (1706KB) ( 28 )  
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    In this work, several experiments were conducted at isobaric and isothermal condition in a CSTR reactor to study the kinetics of methane hydrate formation and dissociation. Experiments were performed at five temperatures and three pressure levels (corresponding to equilibrium pressure). Methane hydrate formation and dissociation rates were modeled using mass transfer limited kinetic models and mass transfer coefficients for both formation and dissociation were calculated. Comparison of results, shows that mass transfer coefficients for methane hydrate dissociation are one order greater than formation conditions. Mass transfer coefficients were correlated by polynomials as relations of pressure and temperature. The results and the method can be applied for prediction of methane production from naturally occurring methane hydrate deposits.
    Pyrolysis of single large biomass particle: Simulation and experiments
    Kai Wang, Huiyan Zhang, Sheng Chu, Zhenting Zha
    2021, 29(1):  375-382.  doi:10.1016/j.cjche.2020.09.032
    Abstract ( 63 )   PDF (2462KB) ( 72 )  
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    Pyrolysis and heat transfer characteristics of single large biomass particle were investigated using three-dimensional unsteady heat transfer model coupled with chemical reactions. The consumption of biomass and the production of products were simulated. Some experiments were designed to provide model parameters for simulation calculations. The simulation was verified by pyrolysis experiments of large biomass particle in a vertical tube furnace. The simulation results show the internal heat and mass transfer law during the pyrolysis of large biomass particle. When the biomass particle diameter is between 10 and 30 mm, for every 5 mm increase in particle diameter, the time required for complete pyrolysis will increase on average by about 50 s. When the pyrolysis temperature is between 673 K and 873 K, a slight decrease in the pyrolysis temperature will cause the time required for the biomass to fully pyrolyze to rise significantly. And the phenomenon is more obvious in the low temperature range. The results indicate that the numerical simulation agrees well with the experimental results.
    A polypropylene melt-blown strategy for the facile and efficient membrane separation of oil-water mixtures
    Zhenqiang Zhang, Danfeng Yu, Xiubin Xu, Huayi Li, Taoyan Mao, Cheng Zheng, Jianjia Huang, Hui Yang, Zihan Niu, Xu Wu
    2021, 29(1):  383-390.  doi:10.1016/j.cjche.2020.03.033
    Abstract ( 69 )   PDF (4282KB) ( 79 )  
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    Porous materials with selective wettability and permeability have significant importance in oil-water separation, but complex fabrication processes are typically required to obtain the desired structures with suitable surface chemistry. In this work, an industrial melt-blown strategy that utilized commercially available polypropylene (PP) was used for the large-scale fabrication of superhydrophobic/superoleophilic membranes with staggered fabric structures. These membranes could readily separate different oils including pump oil and crude oil from various aqueous solutions such as strongly acidic, alkaline, and saline media. In addition, the separation efficiencies of these membranes exceeded 99%, and they could remain functional even after exposure to corrosive media. We anticipate that this work will further the design of membranes and enhance their applicability in oil-water separation, and provide researchers and engineers with a more effective tool for performing challenging separations and mitigating pollution.
    Application of an immobilized microbial consortium for the treatment of pharmaceutical wastewater: Batch-wise and continuous studies
    Shabnam Murshid, Gnana Prakash Dhakshinamoorthy
    2021, 29(1):  391-400.  doi:10.1016/j.cjche.2020.04.008
    Abstract ( 54 )   PDF (1788KB) ( 33 )  
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    In the present investigation, a microbial consortium consisting of four bacterial strains was selected for the treatment of pharmaceutical industry wastewater. The consortium was immobilized on a natural support matrix-Luffa and used for the treatment of real-time pharmaceutical wastewater in batch and continuous processes. The batch process was carried out to optimize the culture conditions and monitor the enzymatic activity. An array of enzymes such as alcohol dehydrogenase, aldehyde dehydrogenase, monooxygenase, catechol 2,3-dioxygenase and hydroquinol 1,2-dioxygenase were produced by the consortium. The kinetics of the degradation in the batch process was analyzed and it was noted to be a first-order reaction. For the continuous study, an aerobic fixed-film bioreactor (AFFBR) was utilized for a period of 61 days with variable hydraulic retention time (HRT) and organic loading rate (OLR). The immobilized microbes treated the wastewater by reducing the COD, phenolic contaminants and suspended solids. The OLR ranged between (0.56 ± 0.05) kg COD·m-3 d-1 to 3.35 kg COD·m-3·d-1 and the system achieved an average reduction of 96.8% of COD, 92.6% of phenolic compounds and 95.2% of suspended solids. Kinetics of the continuous process was interpreted by three different models, where the modified Stover Kincannon model and the Grau second-order model proved to be best fit for the degradation reaction with the constant for saturation value, KL being 95.12 g·L-1·d-1, the constant for maximum utilization of the substrate Umax being 90.01 g·L-1 d-1 and substrate removal constant KY was 1.074 d-1 for both the models. GC-MS analysis confirmed that most of the organic contaminants were degraded into innocuous metabolites.
    Engineering practice and economic analysis of ozone oxidation wet denitrification technology
    Yang Li, Defu Che, Chenglong Yang, Mingyu Yao, Tingwen Zhao, Kangli Fu, Hanchen Zhao
    2021, 29(1):  401-408.  doi:10.1016/j.cjche.2020.08.042
    Abstract ( 40 )   PDF (1375KB) ( 16 )  
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    SO2 and NO emitted from coal-fired power plants have caused serious air pollution in China. In this study, a test system for NO oxidation using O3 is established. The basic characteristics of NO oxidation and products forms are studied. A separate test system for the combined removal of SO2 and NOx is also established, and the absorption characteristics of NOx are studied. The characteristics of NO oxidation and NOx absorption were verified in a 35 t·h-1 industrial boiler wet combined desulfurization and denitrification project. The operating economy of ozone oxidation wet denitrification technology is analyzed. The results show that O3 has a high rate and strong selectivity for NO oxidation. When O3 is insufficient, the primary oxidation product is NO2. When O3 is present in excess, NO2 continues to get oxidized to N2O5 or NO3. The removal efficiency of NO2 in alkaline absorption system is low (only about 15%). NOx removal efficiency can be improved by oxidizing NOx to N2O5 or NO3 by increasing ozone ratio. When the molar ratio of O3/NO is 1.77, the NOx removal efficiency reaches 90.3%, while the operating cost of removing NOx per kilogram is 6.06 USD (NO2).
    Materials and Product Engineering
    An efficient preparation of porous polymeric microspheres by solvent evaporation in foam phase
    Yang Yu, Guiying Li, Wanqing Han, Linhua Zhu, Tian Si, Hong Wang, Yanlin Sun, Yanping He
    2021, 29(1):  409-416.  doi:10.1016/j.cjche.2020.09.002
    Abstract ( 48 )   PDF (2287KB) ( 74 )  
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    This paper reports an efficient method of preparing porous polymeric microspheres by solvent evaporation in foam phase, in which phase separation between polymer and porogen occurs in foam phase instead of that in water phase by using the traditional solvent evaporation method. The method provides outstanding features, including being time-saving, of high-yield and able for continuous production, in which formation of porous polymeric microspheres finished within 3 min with a high production yield up to approximate 95 wt% and the process was able to be developed into a continuous process for production of porous polymeric microspheres. It was also universal to non-crosslinked polymers since the method is a development on the traditional emulsion solvent evaporation method. The new method is efficient and can be used potentially on the industrial scale for continuous production of porous polymeric microspheres.
    Preparation and properties of a low-cost porous ceramic support from low-grade palygorskite clay and silicon-carbide with vanadium pentoxide additives
    Zhaoru Fan, Shouyong Zhou, Ailian Xue, Meisheng Li, Yan Zhang, Yijiang Zhao, Weihong Xing
    2021, 29(1):  417-425.  doi:10.1016/j.cjche.2020.08.018
    Abstract ( 70 )   PDF (2162KB) ( 58 )  
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    A low-cost porous ceramic support was prepared from low-grade palygorskite clay (LPGS) and silicon carbide (SiC) with vanadium pentoxide (V2O5) additives by a dry-press forming method and sintering. The effects of SiC-LPGS ratio, pressing pressure, carbon powder pore-forming agent and V2O5 sintering additives on the microstructure and performance of the supports were investigated. The addition of an appropriate amount of SiC to the LPGS can prevent excessive shrinkage of the support during sintering, and increase the mechanical strength and open porosity of the supports. The presence of SiC (34.4%) led to increases in the open porosity and mechanical strength of 40.43% ± 0.21% and (17.76 ± 0.51) MPa, respectively, after sintering at 700 ℃ for 3 h. Because of its low melting point, V2O5 can melt to liquid during sintering, which increases the mechanical strength of the supports and retains the porosity. Certainly, this can also encourage efficient use of the LPGS and avoid wasting resources.
    Highly interconnected macroporous MBG/PLGA scaffolds with enhanced mechanical and biological properties via green foaming strategy
    Chaobo Song, Jiapeng Zhang, Shuang Li, Shengbin Yang, Eryi Lu, Zhenhao Xi, Lian Cen, Ling Zhao, Weikang Yuan
    2021, 29(1):  426-436.  doi:10.1016/j.cjche.2020.07.063
    Abstract ( 48 )   PDF (2827KB) ( 33 )  
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    In this study, mesoporous bioactive glass particles (MBGs) are incorporated into poly(lactic-co-glycolic acid) (PLGA) to fabricate highly interconnected macroporous composite scaffolds with enhanced mechanical and biological properties via a developed supercritical carbon dioxide (scCO2) foaming method. Scaffolds show favorable highly interconnected and macroporous structure through a high foaming pressure and long venting time foaming strategy. Specifically, scaffolds with porosity from 73% to 85%, pore size from 120 μm to 320 μm and interconnectivity of over 95% are controllably fabricated at MBG content from 0 wt% to 20 wt%. In comparison with neat PLGA scaffolds, composite scaffolds perform improved strength (up to 1.5 folds) and Young's modulus (up to 3 folds). The interconnected macroporous structure is beneficial to the ingrowth of cells. More importantly, composite scaffolds also provide a more promising microenvironment for cellular proliferation and adhesion with the release of bioactive ions. Hopefully, MBG/PLGA scaffolds developed by the green foaming strategy in this work show promising morphological, mechanical and biological features for tissue regeneration.