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Table of Content
28 September 2018, Volume 26 Issue 9
    CFD-PBE simulation of a bubble column in OpenFOAM
    Jingcai Cheng, Qian Li, Chao Yang, Yongqiang Zhang, Zaisha Mao
    2018, 26(9):  1773-1784.  doi:10.1016/j.cjche.2017.11.012
    Abstract ( )   PDF (1351KB) ( )  
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    A general CFD-PBE (computational fluid dynamics-population balance equation) solver for gas-liquid poly-dispersed flows of both low and high gas volume fractions is developed in OpenFOAM (open-source field operation and manipulation) in this work. Implementation of this solver in OpenFOAM is illustrated in detail. The PBE is solved with the cell average technique. The coupling between pressure and velocity is dealt with the transient PIMPLE algorithm, which is a merged PISO-SIMPLE (pressure implicit split operator-semi-implicit method for pressure-linked equations) algorithm. Results show generally good agreement with the published experimental data, whereas the modeling precision could be improved further with more sophisticated closure models for interfacial forces, the models for the bubble-induced turbulence and those for bubble coalescence and breakage. The results also indicate that the PBE could be solved out the PIMPLE loop to save much computation time while still preserving the time information on variables. This is important for CFD-PBE modeling of many actual gas-liquid problems, which are commonly high-turbulent flows with intrinsic transient and 3D characteristics.
    Fluid Dynamics and Transport Phenomena
    Experimental study on gas-liquid dispersion and mass transfer in shear-thinning system with coaxial mixer
    Baoqing Liu, Yijun Zheng, Ruijia Cheng, Zilong Xu, Manman Wang, Zhijiang Jin
    2018, 26(9):  1785-1791.  doi:10.1016/j.cjche.2018.02.009
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    The effects of impeller type, stirring power, gas flow rate, and liquid concentration on the gas-liquid mixing in a shear-thinning system with a coaxial mixer were investigated by experiment, and the overall gas holdup, relative power demand, and volumetric mass transfer coefficient under different conditions were compared. The results show that, the increasing stirring power or gas flow rate is beneficial in promoting the overall gas holdup and volumetric mass transfer coefficient, while the increasing system viscosity weakens the mass transfer in a shearing-thinning system. Among the three turbines, the six curved-blade disc turbine (BDT-6) exhibits the best gas pumping capacity; the six 45° pitched-blade disc turbine (PBDT-6) has the highest volumetric mass transfer coefficient at the same unit volume power.
    A three-dimensional CFD study of the hydrodynamic behavior of equal and unequal-sized in-line methane bubbles at high pressure
    Nikolaos A. Avgerinos, Dionissios P. Margaris
    2018, 26(9):  1792-1802.  doi:10.1016/j.cjche.2017.12.009
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    The hydrodynamic behavior of multiple bubbles rising upward is a field of ongoing research since various aspects of their interaction require further analysis. Shape deformation, rise velocity, and drag coefficient are some of the uncertainties to be determined in a bubble upward flow. For this study the predictions of the three-dimensional numerical simulations of the volume of fluid (VOF) CFD model were first compared with experimental results available in the literature, serving as benchmark cases. Next, 28 cases of pairs of equal and unequal-sized in-line pairs of bubbles moving upwards were simulated. The bubble size varied between 2.0-10 mm. Breakthrough of the present study is the small initial distance of 2.5 R between the center of the bubbles. To provide a more practical nature in this study material properties were selected to match methane gas and seawater properties at deepsea conditions of 15 MPa and 4℃, thus yielding a fluid-to-bubble density ratio λ=7.45 and viscosity ratio n=100.46. This is one of the few studies to report results of the coalescence procedure in this context. The hydrodynamic behavior of the leading and trailing bubbles was thoroughly studied. Simulation results of the evolution of the rise velocity and the shape deformation with time indicate that the assumption that the leading bubble is rising as a free rising single one is not valid for bubbles between 2.0-7.0 mm. Finally, results of the volume of the daughter bubble exhibited an oscillating nature.
    Hydrodynamics features of dispersed bubbles in the ventilated wake flow of a cylinder
    Ning Mao, Can Kang, Wisdom Opare, Yang Zhu
    2018, 26(9):  1803-1813.  doi:10.1016/j.cjche.2018.04.002
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    An experimental study was conducted to investigate the 2D bubbly flow downstream of a cylinder. Sparsely distributed bubbles were produced using the ventilation method. The carrier flow was measured using the particle image velocimetry (PIV) technique. The shadow imaging technique was used to capture instantaneous bubbly flow images. An image-processing code was compiled to identify bubbles in acquired image, calculate the bubble equivalent diameter and the bubble velocity. The effects of Reynolds number and the flow rate of the injected air were considered. The result indicates that the carrier flow is featured by distinct flow structures and the wake region is suppressed as the upstream velocity increases. Regarding the bubbles trapped in the wake flow, the number of small bubbles increases with the upstream velocity. On the whole, the bubble velocity is slightly lower than that of the carrier flow. The consistency between small bubbles and the carrier flow is high in terms of velocity magnitude, which is justified near the wake edge. The difference between the bubble velocity and the carrier flow velocity is remarkable near the wake centerline. For certain Reynolds number, with the increase in the air flow rate, the bubble equivalent diameter increases and the bubble void fraction is elevated.
    Separation Science and Engineering
    Separation of chalcopyrite and pyrite from a copper tailing by ammonium humate
    Cuicui Lü, Yongliang Wang, Peng Qian, Ya Liu, Guoyan Fu, Jian Ding, Shufeng Ye, Yuanfa Chen
    2018, 26(9):  1814-1821.  doi:10.1016/j.cjche.2018.02.014
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    Copper tailings constitute a large proportion of mine wastes. Some of the copper tailings can be recycled to recover valuable minerals. In this paper, a copper tailing was studied through the chemical analysis method, X-ray diffraction and scanning electron microscope-energy dispersive spectrum. It turned out that chalcopyrite (Cu) and pyrite (S) were the main recoverable minerals in the tailing. In order to separate chalcopyrite from pyrite in low pulp pH, ammonium humate (AH) was singled out as the effective regulator. The depression mechanism of AH on the flotation of pyrite was proved by FTIR spectrum and XPS spectrum, demonstrating that there was a chemical adsorption between AH and pyrite. By Response Surface Methodology (RSM), the interaction between AH, pulp pH and iso-butyl ethionine (Z200) was discussed. It was illustrated that the optimal dosage of AH was 1678 g·t-1 involving both the recovery of Cu and S. The point prediction by RSM and the closed-circuit flotation displayed that the qualified Cu concentrate and S concentrate could be obtained from the copper tailing. The study indicated that AH was a promising pyrite depressor in the low pulp pH from copper tailings.
    Simulation of Cefoselis hydrochloride adsorption on macroporous resin in a fixed-bed column using orthogonal collocation
    Feng Xue, Fugang Wang, Shuai Chen, Sheng Wang, Shengui Ju, Weihong Xing
    2018, 26(9):  1822-1828.  doi:10.1016/j.cjche.2017.12.001
    Abstract ( )   PDF (532KB) ( )  
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    Adsorption operation is of great importance for separation and purification of semi-synthetic cephalosporin compounds in pharmaceutical industry. The adsorption dynamics of Cefoselis hydrochloride (CFH) on XR 920C adsorbent in fixed bed was predicted by the model of modified film-pore diffusion (MFPD). The intraparticle diffusion equation and mass balance equation in fixed bed are discretized into two ordinary differential equations (ODEs) using the method of orthogonal collocation which largely improves the calculation accuracy. The MFPD model parameters including the pore diffusion coefficient (Dp), external mass-transfer coefficient (kf), and the axial dispersion (DL) were estimated. The kf value was calculated by the Carberry equation, in which the effective diffusion coefficient De was fitted based on Crank Model through experimental data. Moreover, three key operating parameters (i.e., initial adsorbate concentration; flow rate of import feed, and bed height of adsorbent) and the corresponded breakthrough curves were systematically studied and optimized. Therefore, this research not only provides valuable experimental data, but also a successfully mathematical model for designing the continuous chromatographic adsorption process of CFH.
    Evaluation of solvent-mediated phase transformation of glycine using oleic acid: Morphology and characterization study
    Sevgi Polat, Perviz Sayan
    2018, 26(9):  1829-1836.  doi:10.1016/j.cjche.2017.11.013
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    The polymorphic phase transformation of β-glycine to α-glycine was carried out both in the absence and presence of various concentrations of oleic acid used as additive at 25℃ in a water/ethanol medium. The effects of oleic acid and its concentration on phase transformation time were determined by continuously measuring the ultrasonic velocity. The crystals obtained by the completion of the phase transformation were characterized by XRD, SEM, and TG/DTG. The XRD and SEM results indicated that oleic acid significantly impacted phase transformation time and the morphological characteristics of the crystals. In addition to SEM analysis, detailed crystal shape analysis was performed and the circularity, elongation, and convexity parameters were determined quantitatively. TG/DTG analyses were performed to investigate thermal decomposition behavior and to calculate the activation energies based on different kinetic models such as FWO, KAS, Starink, and Tang kinetic models. With the addition of oleic acid to the medium, the calculated activation energy values increased from 89.63-90.63 to 153.8-155.4 kJ·mol-1. The activation energy values showed that oleic acid was adsorbed on the crystal surface; this result was supported by FTIR, elemental, and Kjeldahl analyses.
    Separation Science and Engineering
    Design and control of a middle-vessel batch distillation for separating DMC-EMC-DEC mixture
    Minyan Zhu, Yafei Hou, Na Yu, Mengqi Chen, Zhanhua Ma, Lanyi Sun
    2018, 26(9):  1837-1844.  doi:10.1016/j.cjche.2017.11.014
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    In this paper, the mixture of dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate was separated by middle-vessel batch distillation with feeding in middle-vessel and process control characteristics were researched. The steady state simulation results in Aspen Plus were exported to Aspen Dynamics. Then control effect of liquid level control with HighSelector, composition control (structure1, structure2) and temperature control (proportional action, proportional integration action) were proposed. Composition control structure 2 and temperature control with PI action were investigated to achieve a good control effect.
    The effect of membrane pores wettability on CO2 removal from CO2/CH4 gaseous mixture using NaOH, MEA and TEA liquid absorbents in hollow fiber membrane contactor
    Ali Taghvaie Nakhjiri, Amir Heydarinasab, Omid Bakhtiari, Toraj Mohammadi
    2018, 26(9):  1845-1861.  doi:10.1016/j.cjche.2017.12.012
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    The present paper renders a modeling and a 2D numerical simulation for the removal of CO2 from CO2/CH4 gaseous stream utilizing sodium hydroxide (NaOH), monoethanolamine (MEA) and triethanolamine (TEA) liquid absorbents inside the hollow fiber membrane contactor. Counter-current arrangement of absorbing agents and CO2/CH4 gaseous mixture flows are implemented in the modeling and numerical simulation. Non-wetting and partial wetting modes of operation are considered where in the partial wetting mode, CO2/CH4 gaseous mixture and liquid absorbents fill the membrane pores. The deteriorated removal of CO2 in the partial wetting mode of operation is mainly due to the mass transfer resistance imposed by the liquid in the pores of membrane. The validation of numerical simulation is done based on the comparison of simulation results of CO2 removal using NaOH and experimental data under non-wetting mode of operation. The comparison illustrates a desirable agreement with an average deviation of less than 5%. According to the results, MEA provides higher efficiency for CO2 removal in comparison with the other liquid absorbents. The order for CO2 removal performance is MEA > NaOH > TEA. The influence of non-wetting and partial wetting modes of operation on CO2 removal are evaluated in this article as one of the novelties. Besides, the percentage of CO2 sequestration as a function of gas velocity for various percentages of membrane pores wetting ranging from 0 (non-wetting mode of operation) to 100% (complete wetting mode of operation) is studied in this research paper, which can be proposed as the other novelty. The results indicate that increase in some operational parameters such as module length, membrane porosity and absorbents concentration encourage the removal percentage of CO2 from CO2/CH4 gaseous mixture while increasing in membrane tortuosity, gas velocity and initial CO2 concentration has unfavorable influence on the separation efficiency of CO2.
    Catalysis, Kinetics and Reaction Engineering
    Synthesis of ordered mesoporous manganese titanium composite oxide catalyst for catalytic ozonation
    Chaofei Fei, Dan Li, Xian Mao, Yu Guo, Wenheng Jing
    2018, 26(9):  1862-1872.  doi:10.1016/j.cjche.2017.09.019
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    In this account, highly ordered mesoporous MnOx/TiO2 composite catalysts with efficient catalytic ozonation of phenol degradation were synthesized by the sol-gel method. The surface morphology and properties of the catalysts were characterized by several analytical methods, including SEM, TEM, BET, XRD, FTIR, and XPS. Interestingly, Mn doping was found to improve the degree of order, and the ordered mesoporous structure was optimized at 3% doping. Meanwhile, MnOx was highly dispersed in the ordered mesoporous materials to yield good catalytic ozonation performance. Phenol could completely be degraded in 20 min and mineralized at 79% in 60 min. Thus, the catalyst greatly improved the efficiency of degradation and mineralization of phenol when compared to single O3 or O3 + TiO2. Finally, the reaction mechanism of the catalyst was discussed and found to conform to pseudo-first-order reaction dynamics.
    Ultralow-weight loading Ni catalyst supported on two-dimensional vermiculite for carbon monoxide methanation
    Mengjuan Zhang, Panpan Li, Mingyuan Zhu, Zhiqun Tian, Jianming Dan, Jiangbing Li, Bin Dai, Feng Yu
    2018, 26(9):  1873-1878.  doi:10.1016/j.cjche.2017.10.024
    Abstract ( )   PDF (1963KB) ( )  
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    Nickel-based catalysts represent the most commonly used systems for CO methanation. We have successfully prepared a Ni catalyst system supported on two-dimensional plasma-treated vermiculite (2D-PVMT) with a very low Ni loading (0.5 wt%). The catalyst precursor was subjected to heat treatment via either conventional heat treatment (CHT) or the plasma irradiation method (PIM). The as-obtained CHT-Ni/PVMT and PIM-Ni/PVMT catalysts were characterized with scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Additionally, CHT-NiO/PVMT and PIM-NiO/PVMT catalysts were characterized with hydrogen temperature programmed reduction (H2-TPR). Compared with CHT-Ni/PVMT, PIM-Ni/PVMT exhibited superior catalytic performance. The plasma treated catalyst PIM-Ni/PVMT achieved a CO conversion of 93.5% and a turnover frequency (TOF) of 0.8537 s-1, at a temperature of 450℃, a gas hourly space velocity of 6000 ml·g-1·h-1, a synthesis gas flow rate of 65 ml·min-1, and a pressure of 1.5 MPa. Plasma irradiation may provide a successful strategy for the preparation of catalysts with very low metal loadings which exhibit excellent properties.
    A sensitivity analysis and multi-objective optimization to enhance ethylene production by oxidative dehydrogenation of ethane in a membrane-assisted reactor
    Ali Darvishi, Ali Bakhtyari, Mohammad Reza Rahimpour
    2018, 26(9):  1879-1895.  doi:10.1016/j.cjche.2018.02.036
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    Owing to the importance of process intensification in the natural gas associated processes, the present contribution aims to investigate the production of an important natural gas downstream product in an improved system. Accordingly, a membrane-assisted reactor for the oxidative dehydrogenation of ethane is presented. The presented system includes a membrane for axial oxygen dosing into the reaction side. Such a strategy would lead to optimum oxygen distribution along the reactor length and prevention of hot spot formation as well. A feasibility study is conducted by developing a validated mathematical model composed of mass and energy balance equations. The effects of various operating variables are investigated by a rigorous sensitivity analysis. Then, by applying the genetic algorithm, a multi-objective optimization procedure is implemented to obtain the optimum operating condition. Considerable increase in the ethane conversion and ethylene yield are the advancements of membrane-assisted oxidative dehydrogenation reactor working under the optimum condition. More than 30% increase in the ethane conversion is obtained. Furthermore, the ethylene yield is enhanced up to 0.45.
    Membrane enhanced COD degradation of pulp wastewater using Cu2O/H2O2 heterogeneous Fenton process
    Hongjia Zhou, Lin Kang, Ming Zhou, Zhaoxiang Zhong, Weihong Xing
    2018, 26(9):  1896-1903.  doi:10.1016/j.cjche.2018.01.007
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    Both activity and stability of the catalyst can be improved in heterogeneous Fenton reaction, in particular, with no limitation for the working pH and no production of the sludge. In this work, a combination of catalyst Cu2O and pore-channel-dispersed H2O2 is proposed to treat the pulp wastewater. Degradation degree of CODs in the wastewater was up to 77% in the ceramic membrane reactor using Cu2O powder (2.0 g·L-1) and membranefeeding H2O2 (0.8 ml·L-1) within 60 min. Evolution of ·OH radical formation in the advanced oxidation process was analyzed with a fluorescent method. Utilization efficiency of H2O2 was successfully enhanced by 10% with the membrane distributor. Further on, the catalyst recyclability was evaluated in a five-cycle test. The concentration of copper ions being dissolved in the treated water was monitored with ICP. After Cu2O/H2O2 (membrane) treatment the effluent is qualified to discharge with COD concentration lower than 15 mg·L-1 with regard to the national standard GB25467-2010.
    Bi-metallic catalysts of mesoporous Al2O3 supported on Fe, Ni and Mn for methane decomposition: Effect of activation temperature
    Anis H. Fakeeha, Ahmed S. Al-Fatesh, Biswajit Chowdhury, Ahmed A. Ibrahim, Wasim U. Khan, Shahid Hassan, Kasim Sasudeen, Ahmed Elhag Abasaeed
    2018, 26(9):  1904-1911.  doi:10.1016/j.cjche.2018.02.032
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    Methane decomposition reaction has been studied at three different activation temperatures (500℃, 800℃ and 950℃) over mesoporous alumina supported Ni-Fe and Mn-Fe based bimetallic catalysts. On co-impregnation of Ni on Fe/Al2O3 the activity of the catalyst was retained even at the high activation temperature at 950℃ and up to 180 min. The Ni promotion enhanced the reducibility of Fe/Al2O3 oxides showing higher catalytic activity with a hydrogen yield of 69%. The reactivity of bimetallic Mn and Fe over Al2O3 catalyst decreased at 800℃ and 950℃ activation temperatures. Regeneration studies revealed that the catalyst could be effectively recycled up to 9 times. The addition of O2 (1 ml, 2 ml, 4 ml) in the feed enhanced substantially CH4 conversion, the yield of hydrogen and the stability of the catalyst.
    Production of glycerol carbonate using crude glycerol from biodiesel production with DBU as a catalyst
    Ying Qing, Houfang Lu, Yingying Liu, Changjun Liu, Bin Liang, Wei Jiang
    2018, 26(9):  1912-1919.  doi:10.1016/j.cjche.2018.01.010
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    The biodiesel production technology catalyzed by 1,8-diazabicycloundec-7-ene (DBU) is developed in this work. Crude glycerol containing DBU and DBU/glycerol/CO2 (DGC) ionic compounds reacts directly with dimethyl carbonate (DMC) to produce high value-added glycerol carbonate (GC) catalyzed by DBU and DGC. The catalytic performance of DBU and DGC, as well as the kinetics of the reaction catalyzed by DBU, were investigated. The results show that DGC has a weak catalytic effect on the transesterification of glycerol and DMC. When the temperature is higher than 60℃, DGC catalyzes the reaction jointly with DBU, which is produced from the decomposition of DGC. DBU has a good catalytic effect on the reaction between glycerol and DMC, with 90% conversion of glycerol and 84% selectivity to GC under the following conditions:DMC-to-glycerol molar ratio of 3:1, 4.0% DBU (based on glycerol mass), reaction time of 60 min, and reaction temperature of 40℃. The apparent kinetics results show that the activation energies are 30.95 kJ·mol-1 and 55.16 kJ·mol-1 for the forward and reverse GC generation reactions, respectively, and the activation energy of the decomposition reaction of GC to glycidol (GD) is 26.58 kJ·mol-1.
    Sulfur production from smelter off-gas using CO-H2 gas mixture as the reducing agent over modified Fe/γ-Al2O3 catalysts
    Tingting Ge, Cuncun Zuo, Lubin Wei, Chunshan Li
    2018, 26(9):  1920-1927.  doi:10.1016/j.cjche.2018.03.031
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    A series of modified γ-Al2O3 supported iron-based catalysts (M-Fe/γ-Al2O3) was developed to reduce SO2 in actual smelter off-gases using CO-H2 gas mixture as reducing agent for sulfur production. Used as modifiers, three metal additives-Ni, Co, and Ce were added to Fe/γ-Al2O3 catalysts. Changes in catalyst structure and active phase were characterized with X-ray diffraction, XPS, SEM, and EDS. The reduction ability of catalysts was exhibited via CO-TPR. The prepared catalysts only need to be pre-reacted for a period of time, eliminating the need for presulfidation treatment. Reaction conditions were optimized in a fixed bed reactor to achieve high SO2 conversion and sulfur selectivity. XRD characterization was carried out to verify the resulting sulfur products. Combining in situ infrared characterization and catalyst evaluation of support and active component, the reaction mechanism was investigated and proposed.
    Development of a CH4 dehydroaromatization-catalyst regeneration fluidized bed system
    Peng Yan, Zhanguo Zhang, Dapeng Li, Xu Cheng, Xinzhuang Zhang, Fan Yang, Chuanfeng Huang, Xiaoxun Ma
    2018, 26(9):  1928-1936.  doi:10.1016/j.cjche.2018.03.035
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    A pilot-scale methane dehydroaromatization-H2 regeneration fluidized bed system (MDARS) was developed. In the MDARS, the catalyst circulation between a fluidized bed reactor and a fluidized bed regenerator with the help of a catalyst feeder allowed methane dehydroaromatization (MDA) and H2 regeneration to be carried out simultaneously, which is good for maintaining a stable MDA catalytic activity. A fixed bed reactor (FB) and a single fluidized bed reactor (SFB) were also used for a comparative study. The experimental results showed that the catalytic activity in the MDARS was more stable than that in the FB and SFB reactors. The effects of some parameters of MDARS on the CH4 conversion and product selectivity were investigated. To verify the feasibility and reliability of the MDARS, an eight-hour long-term test was carried out, which demonstrated that the operation of the MDARS was stable and that the catalytic activity remained stable throughout the entire experimental period.
    Process optimization study on the carbonylation of methyl acetate
    Baohe Wang, Baomin Ge, Jing Zhu, Lina Wang
    2018, 26(9):  1937-1942.  doi:10.1016/j.cjche.2018.01.024
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    Acetic anhydride is the important organic chemical raw material, and is used widely in chemical industry, pharmaceutical industry, dyes, spices and other fields. In this paper, the process of carbonylation of methyl acetate in rhodium iodine catalyst system was studied, and the suitable reaction conditions were determined. At the same time, the kinetic model was established. The optimum reaction conditions were as follows:the reaction pressure was 5 MPa, the hydrogen content was 8%, the amount of iodomethane was 15%, the amount of lithium iodide was 3%, the reaction temperature was 150℃ and the reaction time is 3 h. Under the above reaction conditions, the selectivity of the reaction is close to 100% and the conversion is as high as 92%. The macroscopic kinetic model of the reaction was established in the temperature range of 120℃-150℃. The reaction is an irreversible reaction without the formation of by-products and the dynamic equation is also given in the Conclusions section.
    The influence of different monodentate P-ligand mixtures on Rh-catalyzed 1-butene hydroformylation
    Weili Jiang, Jinxin Chu, Jie Yang, Pengyu Zang, Lijie Gao, Guanglin Zhou, Hongjun Zhou, Huibo Wei
    2018, 26(9):  1943-1948.  doi:10.1016/j.cjche.2018.05.018
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    Four monodentate P-ligands and their mixtures (six groups of double-ligand systems, four groups of triple-ligand systems and one group of tetra-ligand system) were used with Rh(acac)(CO)2 (acac=acetylacetonate) or Rh (acac)CO(PPh3) as the catalyst in the hydroformylation reaction of 1-butene. It was found that different Rh catalysts showed little difference in the catalysis performance. The general order of catalysis performance is doubleligand system > single-ligand system > triple-ligand system > tetra-ligand system. Some synergistic effect in the double-ligand system was detected which needs a further investigation.
    The study of methanol aromatization on transition metal modified ZSM-5 catalyst
    Keming Ji, Jiayao Xun, Ping Liu, Qingwen Song, Junhua Gao, Kan Zhang, Jingyuan Li
    2018, 26(9):  1949-1953.  doi:10.1016/j.cjche.2018.03.024
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    In this article, transition metals of Cu, La and Zn were used as adjuvant to prepare modified HZSM-5 by impregnation method. The catalysts were characterized by XRD, BET, NH3-TPD and Py-IR to reveal the microstructure and acid property. The catalysis performances of methanol aromatization of catalysts were investigated in a fixed-bed reactor. The results show that the strength and distribution of acid center of these catalysts are significantly influenced by the species of transition metal. There are more mediate strong Lewis acid center in Zn modified HZSM-5 catalyst and therefore exhibits higher selectivity to aromatic, benzene, toluene and xylenes in the MTA reaction.
    Process Systems Engineering and Process Safety
    Adiabatic correction for the esterification of acetic anhydride by methanol via accurate kinetics
    Ze Dong, Liping Chen, Yingying Ma, Haoliang Peng, Wanghua Chen
    2018, 26(9):  1954-1959.  doi:10.1016/j.cjche.2017.10.005
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    In the field of adiabatic correction for complex reactions, a simple one-stage kinetic model was used to estimate the real reaction kinetics. However, this assumption simplified the real process, inevitably generated inaccurate or even unsafe results. Therefore, it was necessary to find a new correction method for complex reactions. In this work, esterification of acetic anhydride by methanol was chosen as an object reaction of study. The reaction was studied under different conditions by Reaction Calorimeter (RC1). Then, Thermal Safety Software (TSS) was used to establish the kinetic model and estimate the parameters, where, activation energies for three stages were 67.09, 81.02, 73.77 kJ·mol-1 respectively, and corresponding frequency factors in logarithmic form were 16.05, 19.59, 15.72 s-1. In addition, two adiabatic tests were performed by Vent Sizing Package2 (VSP2). For accurate correction of VSP2 tests, a new correction method based on Enhanced Fisher method was proposed. Combined with kinetics, adiabatic correction of esterification reaction was achieved. Through this research, accurate kinetic parameters for a three-step kinetic model of the esterification reaction were acquired. Furthermore, the correlation coefficients between simulated curves and corrected curves were 0.976 and 0.968, which proved the accuracy of proposed new adiabatic correction method. Based on this new method, conservative corrected results were able to be acquired and be applied in safety assessment.
    Energy, Resources and Environmental Technology
    Life cycle assessment of oxygen-18 production using cryogenic oxygen distillation
    Meysam Akbarian Shourkaei, Abbas Rashidi, Javad Karimi-Sabet
    2018, 26(9):  1960-1966.  doi:10.1016/j.cjche.2017.12.008
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    In this study, life cycle assessment of oxygen-18 by using cryogenic distillation of oxygen is performed using SimaPro 8.3 software. Life cycle assessment is performed to understand the environmental profile and hotspots of this process in order to be used in design and development. Simulation of oxygen-18 process is executed by Hysys software, and the required inputs and outputs for inventory of life cycle were acquired. By doing life cycle assessment and considering achieved results after characterization and normalization of inventory data it has been investigated that in the majority of environmental impacts electricity consumption has a huge contribution relative to other parts of the system like liquefied oxygen production from air separation unit, required facilities for air separation and oxygen-18 units, and needed transportation. Also, among 17 impact categories investigated in ReCiPe impact assessment method, fossil depletion, climate change (human health), particulate matter formation, climate change (ecosystem), human toxicity, and metal depletion have the most contribution in entire environmental loads respectively. Furthermore, sensitivity analysis showed that changing life cycle impact assessment method from ReCiPe to IMPACT 2002 + has no significant effect on acquired results and results are confident. In addition, assumption of market for depleted oxygen from heavy isotopes which is withdrawn from top of distillation columns showed some positive effects compared to first case and environmental impacts resulted from liquefied oxygen production (feed) reduced but because of huge contribution of electricity consumption compared to other sections, this positive effect has no remarkable influence on entire environmental loads of product system.
    Conversions of fuel-N, volatile-N, and char-N to NO and N2O during combustion of a single coal particle in O2/N2 and O2/H2O at low temperature
    Yuan Li, Hao Zhou, Ning Li, Runchao Qiu, Kefa Cen
    2018, 26(9):  1967-1977.  doi:10.1016/j.cjche.2018.01.009
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    Oxy-steam combustion is a promising next-generation combustion technology. Conversions of fuel-N, volatile-N, and char-N to NO and N2O during combustion of a single coal particle in O2/N2 and O2/H2O were studied in a tube reactor at low temperature. In O2/N2, NO reaches the maximum value in the devolatilization stage and N2O reaches the maximum value in the char combustion stage. In O2/H2O, both NO and N2O reach the maximum values in the char combustion stage. The total conversion ratios of fuel-N to NO and N2O in O2/N2 are obviously higher than those in O2/H2O, due to the reduction of H2O on NO and N2O. Temperature changes the trade-off between NO and N2O. In O2/N2 and O2/H2O, the conversion ratios of fuel-N, volatile-N, and char-N to NO increase with increasing temperature, and those to N2O show the opposite trends. The conversion ratios of fuel-N, volatile-N, and char-N to NO reach the maximum values at ?O2?=30 vol% in O2/N2. In O2/H2O, the conversion ratios of fuel-N and char-N to NO reach the maximum values at ?O2?=30 vol%, and the conversion ratio of volatile-N to NO shows a slightly increasing trend with increasing oxygen concentration. The conversion ratios of fuel-N, volatile-N, and char-N to N2O decrease with increasing oxygen concentration in both atmospheres. A higher coal rank has higher conversion ratios of fuel-N to NO and N2O. Anthracite coal exhibits the highest conversion ratios of fuel-N, volatile-N, and char-N to NO and N2O in both atmospheres. This work is to develop efficient ways to understand and control NO and N2O emissions for a clean and sustainable atmosphere.
    Magnéli phases TinO2n-1 as novel ozonation catalysts for effective mineralization of phenol
    Xian Mao, Fanglu Yuan, Anqi Zhou, Wenheng Jing
    2018, 26(9):  1978-1984.  doi:10.1016/j.cjche.2018.01.011
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    Magnéli phases TinO2n-1 have been demonstrated as promising environmentally friendly materials in advanced oxidation processes. In this study, Magnéli phases TinO2n-1 have been used as catalysts for the ozonation of phenol in aqueous solution for the first time. The materials exhibited excellent catalytic ozonation activities both in phenol degradation and mineralization. When Ti4O7 was added, the reaction rate was six-fold higher than that of with ozone alone, while the total organic carbon removal rate was substantially elevated from around 19.2% to 92%. By virtue of the good chemical stability of the materials, a low metal leaching of less than 0.15 mg·L-1 could effectively avoid the secondary pollution by metal ions. Radical quenching tests revealed ·O2- and 1O2 to be active oxygen species for phenol degradation at pH 5. As semiconductor catalysts, TinO2n-1 materials show electronic transfer capability. Ozone adsorbed at B-acid sites of the catalyst surface can capture an electron from the conversion of Ti(Ⅲ) to Ti(IV), and is thereby broken into the active oxygen species. It was interesting to observe that TinO2n-1 exhibit better catalytic activity for phenol degradation and mineralization with lower n value. The difference in electrical conductivity can be considered as a major factor for the catalytic performances. More highly conductive catalysts show a faster electron-transfer rate and better catalytic activity. Thus, significant evidences have been obtained for a single-electron-transfer mechanism of catalytic ozonation with Magnéli phases TinO2n-1.
    Ferroelectric solid solution Li1-xTa1-xWxO3 as potential photocatalysts in microbial fuel cells: Effect of the W content
    Abdellah Benzaouak, Nour-Eddine Touach, V. M. Ortiz-Martínez, M. J. Salar-García, F. Hernández-Fernández, A. P. de los Ríos, Mohammed El Mahi, El Mostapha Lotfi
    2018, 26(9):  1985-1991.  doi:10.1016/j.cjche.2018.02.008
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    Microbial fuel cells (MFCs) are bio-electrochemical systems that can directly convert the chemical energy contained in an effluent into bioelectricity by the action of microorganisms. The performance of these devices is heavily impacted by the choice of the material that forms the cathode. This work focuses on the assessment of ferroelectric and photocatalytic materials as a new class of non-precious catalysts for MFC cathode construction. A series of cathodes based on mixed oxide solid solution of LiTaO3 with WO3 formulated as Li1-xTa1-xWxO3 (x=0, 0.10, 0.20 and 0.25), were prepared and investigated in MFCs. The catalyst phases were synthesized, identified and characterized by DRX, PSD, MET and UV-Vis absorption spectroscopy. The cathodes were tested as photoelectrocatalysts in the presence and in the absence of visible light in devices fed with industrial wastewater. The results revealed that the catalytic activity of the cathodes strongly depends on the ratio of substitution of W6+ in the LiTaO3 matrix. The maximum power densities generated by the MFC working with this series of cathodes increased from 60.45 mW·m-3 for x=0.00 (LiTaO3) to 107.2 mW·m-3 for x=0.10, showing that insertion of W6+ in the tantalate matrix can improve the photocatalytic activity of this material. Moreover, MFCs operating under optimal conditions were capable of reducing the load of chemical oxygen demand by 79% (CODinitial=1030 mg·L-1).
    Materials and Product Engineering
    Characterization and thrust measurements from electrolytic decomposition of ammonium dinitramide (ADN) based liquid monopropellant FLP-103 in MEMS thrusters
    Asad Rahman, Jitkai Chin, Feroz Kabir, Yew Mun Hung
    2018, 26(9):  1992-2002.  doi:10.1016/j.cjche.2017.09.016
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    Although ammonium dinitramide (ADN) has been targeted as a potential green monopropellant in future space vehicles, its application potential in Micro-electrical-Mechanical System (MEMS) thrusters or microthrusters has been seldom reported in open literature. In this paper, electrolytic decomposition of Ammonium Dinitramide (ADN)-based liquid monopropellant FLP-103 was carried out in an open chamber and MEMS thrusters were fabricated from poly-dimethylsiloxane (PDMS) to characterize the power consumption. Two thrust measurement methods were employed to investigate the electrolytic decomposition of FLP-103 in MEMS microthrusters. The results show that the monopropellant can be successfully ignited at room temperature through 80 V, 0.1 A (8 W) using copper wire as electrodes. In the current thruster design, low thrust was obtained at FLP-103 flowrate of 40 μl·min-1 but it generated the highest specific impulse, Isp, among all the flowrates tested. The experiments successfully demonstrated the potential application of electrolytic decomposition of FLP-103 in MEMS thrusters.