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Table of Content
28 May 2018, Volume 26 Issue 5
    Bioregeneration of spent activated carbon: Review of key factors and recent mathematical models of kinetics
    Kwok-Yii Leong, Siew-Leng Loo, Mohammed J. K. Bashir, Wen-Da Oh, Pasupuleti Visweswara Rao, Jun-Wei Lim
    2018, 26(5):  893-902.  doi:10.1016/j.cjche.2017.09.018
    Abstract ( 823 )   PDF (694KB) ( 39 )  
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    The disposal of spent activated carbon (AC) will inevitably create secondary pollution. In overcoming this problem, the spent AC can be regenerated by means of biological approach. Bioregeneration is the phenomenon in which through the action of microorganisms, the adsorbed pollutants on the surface of the AC will be biodegraded and this enables further adsorption of pollutants to occur with time elapse. This review provides the challenges and perspectives for effective bioregeneration to occur in biological activated carbon (BAC) column. Owing to very few reported works on the bioregeneration rate in BAC column, emphasis is put forward on the recently developed models of bioregeneration kinetic in batch system. All in all, providing potential solutions in increasing the lifespan of AC and the enhancement of bioregeneration rate will definitely overcome the bottlenecks in spent AC bioregeneration.
    Fluid Dynamics and Transport Phenomena
    CFD simulations of quenching process for partial oxidation of methane: Comparison of jet-in-cross-flow and impinging flow configurations
    Xinyu Yu, Tianwen Chen, Qi Zhang, Tiefeng Wang
    2018, 26(5):  903-913.  doi:10.1016/j.cjche.2016.04.039
    Abstract ( 719 )   PDF (2622KB) ( 25 )  
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    A new quenching process using the cold pyrolysis gas has been proposed for the partial oxidation (POX) of methane to recover the heat. The mixing of hot product gas and cold pyrolysis gas in milliseconds is critical to this new approach. Two most widely-used rapid mixing configurations, i.e. the jet-in-cross-flow (JICF) and impinging flow configurations, are compared in terms of mixing and quenching performances using computational fluid dynamics (CFD) coupled with detailed reaction mechanism Leeds 1.5. The mixedness, residence time distribution, temperature decreasing rate and loss ratio of acetylene during the quenching are systematically studied. The results show that the impinging flow has a more uniform mixing and narrower residence time distribution than the JICF. However, the temperature decreasing rate of the mainstream is faster in the JICF than in the impinging flow. The loss ratio of acetylene in the quenching process is 2.89% for the JICF and 1.45% for the impinging flow, showing that the impinging flow configuration is better and feasible for the quenching of POX of methane.
    Quantifying growth and breakage of agglomerates in fluid-particle flow using discrete particle method
    Lingfeng Zhou, Junwu Wang, Wei Ge, Shiwen Liu, Jianhua Chen, Ji Xu, Limin Wang, Feiguo Chen, Ning Yang, Rongtao Zhou, Lin Zhang, Qi Chang, Philippe Ricoux, Alvaro Fernandez
    2018, 26(5):  914-921.  doi:10.1016/j.cjche.2017.05.018
    Abstract ( 624 )   PDF (6908KB) ( 12 )  
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    The cohesive solids in liquid flows are featured by the dynamic growth and breakage of agglomerates, and the difficulties in the development, design and optimization of these systems are related to this significant feature. In this paper, discrete particle method is used to simulate a solid-liquid flow system including millions of cohesive particles, the growth rate and breakage rate of agglomerates are then systematically investigated. It was found that the most probable size of the agglomerates is determined by the balance of growth and breakage of the agglomerates the cross point of the lines of growth rate and breakage rate as a function of the particle numbers in an agglomerate, marks the most stable agglomerate size. The finding here provides a feasible way to quantify the dynamic behaviors of growth and breakage of agglomerates, and therefore offers the possibility of quantifying the effects of agglomerates on the hydrodynamics of fluid flows with cohesive particles.
    Coupling simulation of fluid structure interaction in the stirred vessel with a pitched blade turbine
    Yangyang Liang, Zhengming Gao, Dai'en Shi, Wanli Zhao, Ziqi Cai
    2018, 26(5):  922-929.  doi:10.1016/j.cjche.2017.10.026
    Abstract ( 811 )   PDF (4457KB) ( 17 )  
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    The interaction between fluid and a down-pumping pitched blade turbine fixed with a flexible shaft in the stirred vessel, as a typical fluid structure interaction phenomenon, was simulated by coupling the Computational Fluid Dynamics and Computational Structural Dynamics. Based on the verification of the simulated impeller torque and dimensionless shaft bending moment with experimental result, the dimensionless shaft bending moment and various loads acting on impeller (including lateral force, axial force and bending moment) were discussed in detail. By separating and extracting the fluid and structural components from those loads, the results show that the shaft bending moment mainly results from the lateral force on impeller although the axial force on impeller is much larger. The impeller mass imbalance increases the shaft bending moment and the lateral force on impeller, but has little influence on the axial force and bending moment acting on impeller. The dominant frequencies of impeller forces are macro-frequency, speed frequency and blade passing frequency, and are associated with the impeller mass imbalance.
    An integrated model for predicting the flame propagation in crimped ribbon flame arresters
    Zheng Wang, Bing Sun, Qingshan Huang, Fuhua Jiang
    2018, 26(5):  930-941.  doi:10.1016/j.cjche.2017.12.004
    Abstract ( 679 )   PDF (8647KB) ( 21 )  
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    Crimped ribbon flame arresters are important safety devices in the chemical industry, especially for the dangerous situations. Although proper design of arresters by the numerical simulation method is promising, its reliability and accuracy are dependent upon the mathematical model. In this work, an integrated mathematical model for the microchannel in the crimped ribbon flame arresters was set up; the fluid flow behavior and the sensitivities of four chemical kinetics mechanisms of propane-air on the accuracy were analysed. It is shown that turbulence is predominant in the microchannel of the crimped ribbon flame arresters under the deflagration and detonation conditions, and a new quenching criterion for the numerical simulation is proposed. The kinetics mechanism of Mansouri et al. among the four ones is the most accurate due to the best agreement of the predicted outlet temperature at the experimental flameproof velocity with the autoignition temperature of propane-air. The species mass fraction profiles and the temperature distribution, which are too difficult to measure due to the tiny dimension of the microchannel in experiments, are captured. The fundamental insights into chemical reactions and heat loss are well portrayed. It can be concluded that the integrated mathematical model established in this work can be used as a reliable tool for modeling, selecting and designing such type of crimped ribbon flame arresters with the propane-air medium in the future.
    Assessment of k-ε models using tetrahedral grids to describe the turbulent flow field of a PBT impeller and validation through the PIV technique
    Víctor X. Mendoza-Escamilla, Alejandro Alonzo-García, Helvio R. Mollinedo, Israel González-Neria, J. Antonio Yáñez-Varela, Sergio A. Martinez-Delgadillo
    2018, 26(5):  942-956.  doi:10.1016/j.cjche.2018.02.012
    Abstract ( 610 )   PDF (7864KB) ( 14 )  
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    In turbulence modeling, the RNG and Realizable models have important improvements in the turbulent production and dissipation terms in comparison to the Standard. The selection of the appropriate turbulence model has an impact on the convergence and solution in STRs, and they are used in mixing, multiphase modeling or as starting solution of transient models as DES and LES. Although there are several studies with the pitched blade turbine (PBT) impeller, most of them used the Standard model as representative of all k-ε models, using structured hexahedral grids composed of low number of cells, and in some cases under axial symmetry assumptions. Accordingly, in this work the assessment of the Standard, RNG and Realizable models to describe the turbulent flow field of this impeller, using the Multiple Reference Frame (MRF) and Sliding Mesh (SM) approaches with tetrahedral domains in dense grids, is presented. This kind of cell elements is especially suitable to reproduce complex geometries. Flow velocities and turbulent parameters were verified experimentally by PIV and torque measurements. The three models were capable of predicting fairly the pumping number, the power number based on torque, and velocities. Although the RNG improved the predictions of the turbulent kinetic energy and dissipation rate, the Realizable model presented better performance for both approaches. All models failed in the prediction of the total dissipation rate, and a dependence of its value on the number of cells for the MRF was found.
    Separation Science and Engineering
    Super-hydrophobic and super-lipophilic functionalized graphene oxide/polyurethane sponge applied for oil/water separation
    Huiwen Meng, Tao Yan, Jingang Yu, Feipeng Jiao
    2018, 26(5):  957-963.  doi:10.1016/j.cjche.2017.09.004
    Abstract ( 729 )   PDF (3184KB) ( 17 )  
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    Nowadays, oil spills have led to a serious environmental crisis of the world. To deal with this problem, inspired from super-hydrophobic lotus leaf, this study fabricated super-hydrophobic and super-lipophilic functionalized graphene oxide/polyurethane (FGP) sponge by a simple and inexpensive dip coating method. The resulting FGP sponge was characterized by infrared spectroscopy, X-ray diffraction, scanning electron microscopy and water contact angle. The results expressed that FGP sponge exhibited a similar surface structure to that of a lotus leaf, and possessed the super-hydrophobic characteristic with the water contact angle (WAC) of 152° ±1°. The absorption capacity and reusability were also investigated. It can be seen that, the FGP sponge can remove a wide range of oils and organic solvents from water with good absorption capacities (up to 35 times of its own mass). Significantly, after 10 cycles the absorption capacity of the oils and organic solvents was higher than 90% for the reused FGP sponge, demonstrating the good reusability of the FGP sponge. Therefore, this study probably provided a simple way to remove the pollutions of oil spills and toxic organism from water.
    Solubility of red palm oil in supercritical carbon dioxide: Measurement and modelling
    Wan Jun Lee, Chin Ping Tan, Rabiha Sulaiman, Gun Hean Chong
    2018, 26(5):  964-969.  doi:10.1016/j.cjche.2017.09.024
    Abstract ( 621 )   PDF (631KB) ( 23 )  
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    The solubility of red palm oil (RPO) in supercritical carbon dioxide (scCO2) was determined using a dynamic method at 8.5-25 MPa and, 313.15-333.15 K and at a fixed scCO2 flow rate of 2.9 g·min-1 using a full factorial design. The solubility was determined under low pressures and temperatures as a preliminary study for RPO particle formation using scCO2. The solubility of RPO was 0.5-11.3 mg·(g CO2)-1 and was significantly affected by the pressure and temperature. RPO solubility increased with pressure and decreased with temperature. The Adachi-Lu model showed the best-fit for RPO solubility data with an average relative deviation of 14% with a high coefficient of determination, R2 of 0.9667, whereas the Peng-Robinson equation of state thermodynamic model recorded deviations of 17%-30%.
    Modelling of heat transfer for progressive freeze concentration process by spiral finned crystallizer
    Shafirah Samsuri, Nurul Aini Amran, Mazura Jusoh
    2018, 26(5):  970-975.  doi:10.1016/j.cjche.2017.09.025
    Abstract ( 717 )   PDF (884KB) ( 23 )  
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    This study presents a novel design for a spiral finned crystallizer which is the primary element of progressive freeze concentration (PFC) system, which simplifies the setup of the conventional system. After the crystallizer has been designed, the research experiments have been conducted and evaluated through a thorough analysis of its performance by developing a mathematical model that can be used to predict the productivity of ice crystal at a range of coolant temperature. The model is developed based on the basic heat transfer equation, and by considering the solution's and the coolant's convective heat transfer coefficient (h) under the forced flow condition. The model's accuracy is verified by making comparison between the ice crystal mass' experimental value and the values predicted by the model. Consequently, the study found that the model helps in enhancing the PFC system.
    Osmotic concentration of succinic acid by forward osmosis: Influence of feed solution pH and evaluation of seawater as draw solution
    Jeng Yih Law, Abdul Wahab Mohammad
    2018, 26(5):  976-983.  doi:10.1016/j.cjche.2017.10.003
    Abstract ( 538 )   PDF (1068KB) ( 7 )  
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    In this study, we investigated the essential role of feed solution pH so as to gain insights into the transport mechanisms of succinic acid concentration by osmotically-driven forward osmosis (FO) process. FO performances including water flux and bidirectional transport of succinate and chloride anions were systematically examined using cellulose triacetate-based FO membrane. Additionally, real seawater was explored as draw solution. Experimental results revealed that the pH-dependent speciation of succinic acid can affect the FO performances. Ionization of succinic acid at higher solution pH enhanced the osmotic pressure of feed solution, thus leading to lower water flux performance. A strong effect was pointed out on the succinate rejection for which nearly 100% rejections were achieved at pH above its pKa2 value. The rejection of succinate increased in the following order of chemical form:C2H4C2O4H2 < C2H4C2O4H- < C2H4C2O42-. With real seawater as the draw solution, low to moderate water fluxes (<4 L·m-2·h-1) were observed. The divalent succinate anion was highly retained in the feed side despite differences in the succinic acid feed concentration at pH of approximately 6.90.
    Effect of the chelating agents on bio-sorption of hexavalent chromium using Agave sisalana fibers
    H. Bendjeffal, A. Djebli, H. Mamine, T. Metidji, M. Dahak, N. Rebbani, Y. Bouhedja
    2018, 26(5):  984-992.  doi:10.1016/j.cjche.2017.10.016
    Abstract ( 548 )   PDF (4514KB) ( 38 )  
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    The current work is focused on the study of the bio-sorption of hexavalent chromium from aqueous solution using sisal natural fiber (Agave sisalana) treated by various chelating agents (ligands) such as urea (UR), thiocarbamide (TC), ethylenediaminetetraacetic acid (EDTA), and diphenyl carbazide (DCZ). The fiber treatments were investigated using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning electron microscope (SEM). The kinetics of chromium bio-sorption was studied in batch presses under the effect of some physicochemical factors such as the nature of chelating agent (F@UR, F@TC, F@DCZ, and F@EDTA), adsorbent dose (2-10 g·L-1), chromium initial concentration (100-500 mg·L-1), solution pH (1-6), and batch temperature (20℃-50℃). This study resulted in an optimum adsorption at a chromium initial concentration of 100 mg·L-1, at pH 2, and at 20℃. The obtained results showed clearly that the treatment with chelating agent boosts the adsorptive capacity of A. sisalana fibers Cr(VI) 10.9 mg·g-1 to 58.6 mg·g-1. The modeling study showed that the adsorption kinetics obey the pseudo-second-order model, with an R2 in the range of 0.991 and 0.999. The bio-sorption isotherms followed the Langmuir model; the maximum uptake capacity of (F@N, F@UR, F@TC, F@DCZ, and F@EDTA) was found to be respectively, 12.3 mg·g-1, 25.33 mg·g-1, 28.73 mg·g-1, 42.54 mg·g-1, and 61.45 mg·g-1. The determined adsorption thermodynamics parameters such as enthalpy, free energy, and entropy showed that the adsorption process is exothermic, spontaneous, and has a stable configuration.
    Effect of thermodynamic parameters on prediction of phase behavior and process design of extractive distillation
    Hui Jia, Huixin Wang, Kang Ma, Mengxiao Yu, Zhaoyou Zhu, Yinglong Wang
    2018, 26(5):  993-1002.  doi:10.1016/j.cjche.2017.11.003
    Abstract ( 740 )   PDF (3077KB) ( 25 )  
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    Extractive distillation was investigated for separation of the minimum azeotrope of n-propanol/water, via the Aspen Plus simulation platform. Experimental data of n-propanol/water, which could pass the thermodynamic consistency test, were regressed to get suitable binary interaction parameters (BIPs) by the UNIQUAC thermodynamic model. The azeotrope system was heterogeneous in the simulation with built-in BIPs, which was contrary to the experimental data. The study focused on the effect of thermodynamic parameters on the prediction of phase behavior, and process design of extractive distillation. N-methyl-2-pyrrolidone (NMP) and ethylene glycol were used as solvents to implement the separation. Processes with built-in and regressed BIPs were explored, based on the minimum total annual cost (TAC). There were significant differences in the phase behavior simulation using different thermodynamic parameters, which showed the importance of BIPs in the design and optimization of extractive distillation.
    Synthesis of activated carbon from spent tea leaves for aspirin removal
    Syieluing Wong, Yowjeng Lee, Norzita Ngadi, Ibrahim Mohammed Inuwa, Nurul Balqis Mohamed
    2018, 26(5):  1003-1011.  doi:10.1016/j.cjche.2017.11.004
    Abstract ( 1062 )   PDF (1197KB) ( 126 )  
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    Adsorption capacity of activated carbon prepared from spent tea leaves (STL-AC) for the removal of aspirin from aqueous solution was investigated in this study. Preliminary studies have shown that treatment with phosphoric acid (H3PO4) increased removal efficiency of STL-AC. Characterizations on STL-AC revealed excellent textural properties (1200 m2·g-1, 51% mesoporosity), as well as distinctive surface chemistry (1.08 mmol·g-1 and 0.54 mmol·g-1 for acidic and basic oxygenated groups, pHpzc=2.02). Maximum removal efficiency of aspirin observed was 94.28% after 60 min when the initial concentration was 100 mg·L-1, 0.5 g of adsorbent used, pH 3 and at a temperature of 30℃. The adsorption data were well fitted to the Freundlich isotherm model and obeyed the pseudo-second order kinetics model. The adsorption of aspirin onto STL-AC was exothermic in nature (ΔHΘ=-13.808 kJ·mol-1) and had a negative entropy change, ΔSΘ (-41.444 J·mol-1). A negative Gibbs free energy, ΔGΘ was obtained indicating feasibility and spontaneity of the adsorption process. The adsorption capacity of AC-STL (178.57 mg·g-1) is considerably high compared to most adsorbents synthesized from various sources, due to the well-defined textural properties coupled with surface chemistry of STL-AC which favors aspirin adsorption. The results demonstrate the potential of STL-AC as aspirin adsorbent.
    Water-stable ZIF-300/Ultrason® mixed-matrix membranes for selective CO2 capture from humid post combustion flue gas
    Muhammad Sarfraz, M. Ba-Shammakh
    2018, 26(5):  1012-1021.  doi:10.1016/j.cjche.2017.11.007
    Abstract ( 696 )   PDF (3229KB) ( 22 )  
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    Water stable mixed-matrix membranes (MMMs) were developed to help control the global warming by capturing and sequestrating carbon dioxide (CO2) from post-combustion flue gas originated from burning of fossil fuels. MMMs of different compositions were prepared by doping glassy polymer Ultrason® S 6010 (US) with nanocrystals of zeolitic imidazolate frameworks (ZIF-300) in varying degrees. Solution-casting technique was used to fabricate various MMMs to optimize their CO2 capturing performance from both dry and wet gases. The prepared composite membranes indicated enhanced filler-polymer interfacial adhesion, consistent distribution of nanofiller, and thermally established matrix configuration. CO2 permeability of the membranes was enhanced as demonstrated by gas sorption and permeation experiments performed under both dry and wet conditions. As compared to neat Ultrason® membrane, CO2 permeability of the composite membrane doped with 40 wt% ZIF-300 nanocrystals was increased by four times without disturbing CO2/N2 ideal selectivity. In contrast to majority of previously reported membranes, key features of the fabricated MMMs include their structural stability under humid conditions coupled with better and unaffected gas separation performance.
    Experimental and simulation study of nylon 6 solid-liquid extraction process
    Chunxi Qin, Jie Tang, Fenglei Bi, Zhenhao Xi, Ling Zhao
    2018, 26(5):  1022-1030.  doi:10.1016/j.cjche.2017.12.002
    Abstract ( 765 )   PDF (1929KB) ( 21 )  
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    The solid-liquid extraction process of nylon 6 to eliminate small molecules, i.e., caprolactam (CL), cyclic dimers (CD) and cyclic trimers (CT), is investigated in detail by both batch extraction experiments and numerical simulations. In the batch extraction experiments, due to the small molecules attaching to the polymeric surface, the basic physical mechanism shifts from surface diffusion to internal diffusion as the extraction proceeded. The experimental data are well reproduced by a diffusion model consisting of two distinct steps, characterized as surface diffusion and internal diffusion. Furthermore, based on the established mass transfer mechanism and diffusion model of the two distinct steps, the equilibrium constants and internal diffusion coefficients of CL, CD and CT are acquired. An industrial countercurrent extraction tower is further simulated. It is found that the extraction efficiency of CL can be significantly improved by increasing the temperature at the bottom portion of the tower. The elimination of CD, which can be greatly promoted by a high-concentration CL-water solution, is controlled by mass transfer resistance, whereas the removal of CL is mainly affected by the equilibrium.
    Catalysis, kinetics and reaction engineering
    High-performance phosphate supported on HZSM-5 catalyst for dehydration of glycerol to acrolein
    Feng Zhang, Xin Ren, He Huang, Jun Huang, Medak Sudhakar, Licheng Liu
    2018, 26(5):  1031-1040.  doi:10.1016/j.cjche.2018.01.005
    Abstract ( 622 )   PDF (3410KB) ( 17 )  
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    The purpose of this study is to increase acrolein yield and capability of coking resistance in the reaction of glycerol dehydration to acrolein by assembling metal phosphate supported on HZSM-5 catalyst. The as-prepared catalysts were characterized by XRD, SEM, EDS, BET, NH3-TPD, CO2-TPD and Py-IR techniques. It was found that metal phosphate species were incorporated into the porous structure of HZSM-5 zeolites, thus influencing the surface and textural physico-chemical properties of the supporters. The alkaline-treated HZSM-5 catalyst promoted the dispersion of phosphate species on the carriers. Moreover, the amount of strong acidity was tremendously improved by adding the different metal hydrophosphates and the catalysts show high catalytic activity. In this present work, the Sn1/4H2PO4/HZSM-5 catalyst exhibited good performance in the catalytic activity and coking resistant ability, which resulted in a high acrolein yield of 83% initially and acrolein yield of 68% after 30 h. The acidity, especially the ratio of strong to weak acid, plays an important role in promoting acrolein yield and stability simultaneously.
    Kinetic contribution of CO2/O2 additive in methane conversion activated by non-equilibrium plasmas
    Qi Chen, Jintao Sun, Xiaojun Zhang
    2018, 26(5):  1041-1050.  doi:10.1016/j.cjche.2018.01.006
    Abstract ( 964 )   PDF (4628KB) ( 33 )  
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    A temperature-controlled and pressure-controlled coaxial dielectric barrier discharge (DBD) reactor was developed to decouple the thermal and kinetic effects of radio frequency (RF) discharge on methane conversion, and further to compare the kinetic behaviors of the mechanistically similar reactions of methane conversion with O2 and CO2 additives. A kinetic mechanism for RF plasma assisted methane conversion was assembled. The formation of products in the RF plasma reactor was measured with Gas Chromatography (GC-TCD) and the data were used to validate the kinetic model. The experimental and computational results showed the different kinetic roles of carbon dioxide and oxygen additives in methane conversion, due to the different dissociation and ionization energy of the two additive gases, as well as the thus produced electron energy distribution function (EEDF). Fuel oxidation by plasma generated O, O(1D), O2(a1Δg), O2(b1Σg+) and O+ in partial oxidation of methane was observed essential for methane consumption, which resulted in an increase in methane conversion rate, compared to pure methane pyrolysis and dry reforming of methane with CO2 additive. It was also found that dry reforming of methane with CO2 was by far the easier to produce the syngas as well as C2 hydrocarbon species, due to the weak oxidation ability of CO2 and also the significant deposition of the electron energy on CH4 dissociation in a dry reforming discharge mixture. This kinetic study produced comparative data to demonstrate the contribution of CO2/O2 additive in non-equilibrium plasma assisted methane conversion.
    Effect of copper precursors on the catalytic performance of Cu-ZSM-5 catalysts in N2O decomposition
    Tao Meng, Nan Ren, Zhen Ma
    2018, 26(5):  1051-1058.  doi:10.1016/j.cjche.2018.02.015
    Abstract ( 583 )   PDF (3593KB) ( 41 )  
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    Five Cu-ZSM-5 catalysts were obtained by treating Na-ZSM-5 (Si/Al ratio=15) with aqueous solutions of different Cu precursors (CuCl2, Cu(NO3)2, CuSO4, Cu(CH3COO)2, and ammoniacal copper (Ⅱ) complex ion). After being pretreated in flowing He at 500℃ to form active Cu+, these catalysts exhibited quite different activities in catalytic decomposition of N2O. CZM-AC(Ⅱ) (prepared by ammoniacal copper (Ⅱ) complex ion) with 9.4 wt% Cu content was the most active among these Cu-ZSM-5 catalysts, achieving almost complete N2O conversion at 400℃. CZM-CA (prepared using Cu(CH3COO)2 as the Cu precursor) with 2.8 wt% Cu content was the second most active catalyst among these Cu-ZSM-5 catalysts, achieving almost complete N2O conversion at 425℃. CZM-CC, CZMCN, and CZM-CS prepared by using CuCl2, Cu(NO3)2, or CuSO4 as the Cu precursor with similar Cu contents (≈1.7 wt%) were the least active among these Cu-ZSM-5 catalysts, achieving ca. 90% N2O conversion at 500℃. XRD, ICP, SEM, TEM, EDX-mapping, and CO-IR experiments were conducted to characterize relevant samples. The superior activity of CZM-AC(Ⅱ) can be attributed to the high contents of total Cu+ and dimeric Cu+ among these samples. The influence of co-fed O2 or H2O on the catalytic performance of typical samples was also studied.
    Influence of dehydrating agents on the oxidative carbonylation of methanol for dimethyl carbonate synthesis over a Cu/Y-zeolite catalyst
    Dong-Ho Lee, Jiin You, Je-Min Woo, Jung Yoon Seo, Young Cheol Park, Jong-Seop Lee, Hyunuk Kim, Jong-Ho Moon, Seung Bin Park
    2018, 26(5):  1059-1063.  doi:10.1016/j.cjche.2018.02.018
    Abstract ( 679 )   PDF (1061KB) ( 16 )  
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    The influence of the dehydration by metal oxides on the synthesis of dimethyl carbonate (DMC) via oxidative carbonylation of methanol was studied. A Cu/Y-zeolite catalyst was prepared by the ion exchange method from CuCl2·2H2O and the commercial NH4-form of the Y type zeolite. The catalyst was characterized by X-ray fluorescence (XRF), N2 adsorption (BET method), X-ray diffraction (XRD), and temperature-programmed desorption of ammonia (NH3-TPD) to evaluate its Cu and Cl content, surface area, structure, and acidity. Reaction tests were carried out using an autoclave (batch reactor) for 18 h at 403 K and 5.5 MPa (2CH3OH + 1/2O2 + CO ? (CH3O)2CO + H2O). The influence of various dehydrating agents (ZnO, MgO, and CaO) was examined with the aim of increasing the methanol conversion (XMeOH, MeOH conversion). The MeOH conversion increased upon addition of metal oxides in the order CaO >> MgO > ZnO, with the DMC selectivity (SDMC) following the order MgO > CaO > ZnO. The catalysts and dehydrating agents were characterized before and after the oxidative carbonylation of methanol by thermogravimetric and differential thermogravimetric (TG/DTG), and XRD to confirm that the dehydration reaction occurred via the metal oxide (MO + H2O → M(OH)2). The MeOH conversion increased from 8.7% to 14.6% and DMC selectivity increased from 39.0% to 53.1%, when using the dehydrating agent CaO.
    Catalysis, Kinetics and Reaction Engineering
    Catalyst-free and solvent-free oxidation of cycloalkanes (C5-C8) with molecular oxygen: Determination of autoxidation temperature and product distribution
    Haimin Shen, Yan Wang, Jinhui Deng, Long Zhang, Yuanbin She
    2018, 26(5):  1064-1070.  doi:10.1016/j.cjche.2018.02.019
    Abstract ( 648 )   PDF (830KB) ( 115 )  
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    Autoxidation of cycloalkanes (C5-C8) with molecular oxygen under catalyst-free and solvent-free conditions was conducted systematically for the first time, focusing on the autoxidation temperature and product distribution. The autoxidation of cyclopentane, cyclohexane, cycloheptane and cyclooctane occurs at 120℃, 130℃, 120℃, and 105℃ respectively, with obvious oxidized products formation. At 140℃, 145℃, 130℃ and 125℃, acceptable yields of the oxidized products could be obtained for them, and the oxidized product distributions were investigated in detail. The autoxidation of cycloalkanes follows the pseudo-first-order kinetic model and the apparent activation energies (Ea) for the autoxidation of cyclopentane and cyclohexane are 159.76 kJ·mol-1 and 86.75 kJ·mol-1 respectively. This study can act as an important reference in screen of suitable reaction temperature and comparison of the performance of various catalysts in the catalytic oxidation of cycloalkanes in the attempt to enhance the oxidized product selectivity.
    Process Systems Engineering and Process Safety
    A sludge volume index (SVI) model based on the multivariate local quadratic polynomial regression method
    Honggui Han, Xiaolong Wu, Luming Ge, Junfei Qiao
    2018, 26(5):  1071-1077.  doi:10.1016/j.cjche.2017.08.007
    Abstract ( 718 )   PDF (936KB) ( 55 )  
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    In this study, a multivariate local quadratic polynomial regression (MLQPR) method is proposed to design a model for the sludge volume index (SVI). In MLQPR, a quadratic polynomial regression function is established to describe the relationship between SVI and the relative variables, and the important terms of the quadratic polynomial regression function are determined by the significant test of the corresponding coefficients. Moreover, a local estimation method is introduced to adjust the weights of the quadratic polynomial regression function to improve the model accuracy. Finally, the proposed method is applied to predict the SVI values in a real wastewater treatment process (WWTP). The experimental results demonstrate that the proposed MLQPR method has faster testing speed and more accurate results than some existing methods.
    A risk-based methodology for the optimal placement of hazardous gas detectors
    Kang Cen, Ting Yao, Qingsheng Wang, Shengyong Xiong
    2018, 26(5):  1078-1086.  doi:10.1016/j.cjche.2017.10.031
    Abstract ( 605 )   PDF (2950KB) ( 30 )  
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    Hazardous gas detection systems play an important role in preventing catastrophic gas-related accidents in process industries. Even though effective detection technology currently exists for hazardous gas releases and a majority of process installations have a large number of sensitive detectors in place, the actual operating performance of gas detection systems still does not meet the expected requirements. In this paper, a riskbased methodology is proposed to optimize the placement of hazardous gas detectors. The methodology includes three main steps, namely, the establishment of representative leak scenarios, computational fluid dynamics (CFD)-based gas dispersion modeling, and the establishment of an optimized solution. Based on the combination of gas leak probability and joint distribution probability of wind velocity and wind direction, a quantitative filtering approach is presented to select representative leak scenarios from all potential scenarios. The commercial code ANSYS-FLUENT is used to estimate the consequence of hazardous gas dispersions under various leak and environmental conditions. A stochastic mixed-integer linear programming formulation with the objective of minimizing the total leak risk across all representative leak scenarios is proposed, and the greedy dropping heuristic algorithm (GDHA) is used to solve the optimization model. Finally, a practical application of the methodology is performed to validate its effectiveness for the optimal design of a gas detector system in a high-sulfur natural gas purification plant in Chongqing, China. The results show that an appropriate number of gas detectors with optimal cost-effectiveness can be obtained, and the total leak risk across all potential scenarios can be substantially reduced. This methodology provides an effective approach to guide the optimal placement of pointtype gas detection systems involved with either single or mixed gas releases.
    Composition control and temperature inferential control of dividing wall column based on model predictive control and PI strategies
    Jianxin Wang, Na Yu, Mengqi Chen, Lin Cong, Lanyi Sun
    2018, 26(5):  1087-1101.  doi:10.1016/j.cjche.2017.12.005
    Abstract ( 664 )   PDF (1721KB) ( 28 )  
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    The dividing wall column (DWC) is considered as a major breakthrough in distillation technology and has good prospect of industrialization. Model predictive control (MPC) is an advanced control strategy that has acquired extensive applications in various industries. In this study, MPC is applied to the process for separating ethanol, n-propanol, and n-butanol ternary mixture in a fully thermally coupled DWC. Both composition control and temperature inferential control are considered. The multiobjective genetic algorithm function "gamultiobj" in Matlab is used for the weight tuning of MPC. Comparisons are made between the control performances of MPC and PI strategies. Simulation results show that although both MPC and PI schemes can stabilize the DWC in case of feed disturbances, MPC generally behaves better than the PI strategy for both composition control and temperature inferential control, resulting in a more stable and superior performance with lower values of integral of squared error (ISE).
    Modeling and optimization of industrial Fischer-Tropsch synthesis with the slurry bubble column reactor and iron-based catalyst
    Chufu Li
    2018, 26(5):  1102-1109.  doi:10.1016/j.cjche.2018.01.002
    Abstract ( 774 )   PDF (1227KB) ( 34 )  
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    To optimize industrial Fischer-Tropsch (FT) synthesis with the slurry bubble column reactor (SBCR) and ironbased catalyst, a comprehensive process model for FT synthesis that includes a detailed SBCR model, gas liquid separation model, simplified CO2 removal model and tail gas cycle model was developed. An effective iteration algorithm was proposed to solve this process model, and the model was validated by industrial demonstration experiments data (SBCR with 5.8 m diameter and 30 m height), with a maximum relative error < 10% for predicting the SBCR performances. Subsequently, the proposed model was adopted to optimize the industrial SBCR performances simultaneously considering process and reactor parameters variations. The results show that C5+ yield increases as catalyst loading increases within 10-70 ton and syngas H2/CO value decreases within 1.3-1.6, but it doesn't increase obviously when the catalyst loading exceeds 45 ton (about 15 wt% concentration). Higher catalyst loading will result in higher difficulty for wax/catalyst separation and higher catalyst cost. Therefore, the catalyst loading (45 ton) is recommended for the industrial demonstration SBCR operation at syngas H2/CO=1.3, and the C5+ yield is about 402 ton" per day, which has an about 16% increase than the industrial demonstration run result.
    Chemical Engineering Thermodynamics
    Effect of different additives on the phase separation behavior and thermodynamics of p-tert-alkylphenoxy poly (oxyethylene) ether in absence and presence of drug
    Marzia Rahman, Md. Anamul Hoque, Mohammed Abdullah Khan, Malik Abdul Rub, Abdullah M. Asiri
    2018, 26(5):  1110-1118.  doi:10.1016/j.cjche.2017.10.011
    Abstract ( 736 )   PDF (1009KB) ( 29 )  
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    Cloud point (CP) determinations of 4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (TX-100 (nonionic surfactant)) was carried out in aqueous as well as in the attendance of drug (ceftriaxone sodium trihydrate (CFT))/(CFT + different inorganic salts) and discussed thoroughly. Nonionic surfactants are employed extensively in different formulations. In aqueous solution, the values of CP of TX-100 are obtained to increase by means of enhancing of their concentration in the solution. The CP values of TX-100 solutions were found to decrease in the presence of drug and their values decrease more with rising concentrations of the drug. The values of CP of CFT and TX-100 mixtures were found to further decrease in the attendance of inorganic salts in comparison to their absence. The effect of different sodium salts in decreasing CP values of TX-100 was achieved in the following order:NaCO3 > Na2SO4 > NaCl. However, in the case of potassium and ammonium salts, the decreasing order obtained is K2SO4 > KCO3 > KCl and (NH4)2SO4 > Na2CO3 > NH4Cl respectively. Various thermodynamic parameters for example standard free energy (ΔGcΘ), standard enthalpy (ΔHcΘ) as well as standard entropy (ΔScΘ) changes of phase separation were also evaluated and discussed in detail on the basis of their behavior.
    Effect of different additives on the phase separation behavior and thermodynamics of p-tert-alkylphenoxy poly (oxyethylene) ether in absence and presence of drug
    Marzia Rahman, Md. Anamul Hoque, Mohammed Abdullah Khan, Malik Abdul Rub, Abdullah M. Asiri
    2018, 26(5):  1110-1118.  doi:10.1016/j.cjche.2017.10.011
    Abstract ( 243 )   PDF (1009KB) ( 4 )  
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    Cloud point (CP) determinations of 4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (TX-100 (nonionic surfactant)) was carried out in aqueous as well as in the attendance of drug (ceftriaxone sodium trihydrate (CFT))/(CFT + different inorganic salts) and discussed thoroughly. Nonionic surfactants are employed extensively in different formulations. In aqueous solution, the values of CP of TX-100 are obtained to increase by means of enhancing of their concentration in the solution. The CP values of TX-100 solutions were found to decrease in the presence of drug and their values decrease more with rising concentrations of the drug. The values of CP of CFT and TX-100 mixtures were found to further decrease in the attendance of inorganic salts in comparison to their absence. The effect of different sodium salts in decreasing CP values of TX-100 was achieved in the following order:NaCO3 > Na2SO4 > NaCl. However, in the case of potassium and ammonium salts, the decreasing order obtained is K2SO4 > KCO3 > KCl and (NH4)2SO4 > Na2CO3 > NH4Cl respectively. Various thermodynamic parameters for example standard free energy (ΔGcΘ), standard enthalpy (ΔHcΘ) as well as standard entropy (ΔScΘ) changes of phase separation were also evaluated and discussed in detail on the basis of their behavior.
    Temperature-dependent aggregation of bio-surfactants in aqueous solutions of galactose and lactose: Volumetric and viscometric approach
    S. Chauhan, Vivek Sharma, Maninder Kaur, Poonam Chaudhary
    2018, 26(5):  1119-1131.  doi:10.1016/j.cjche.2017.10.025
    Abstract ( 705 )   PDF (846KB) ( 16 )  
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    Modulation in the aggregation behavior of bio-surfactants (bile salts), sodium cholate (NaC) and sodium deoxycholate (NaDC) in aqueous solutions of carbohydrates (galactose and lactose) have been investigated by measuring the density (ρ), speed of sound (u) and viscosity (η) of the mixtures at different temperatures 293.15, 298.15, 303.15, 308.15 and 313.15 K. The density and speed of sound data have been used to calculate various volumetric and compressibility parameters such as apparent molar volume (Vφ), isentropic compressibility (κs), apparent molar adiabatic compression (κs, φ) to get a better insight into the micellization mechanism of bile salts. Further, the viscosity data have been studied in the light of relative viscosity (ηr) and viscous relaxation time (τ). Some derived parameters such as free volume (Vf), internal pressure (πi) and molar cohesive energy (MCE) of NaC and NaDC in aqueous solution of saccharides have also been calculated from viscosity data in conjunction with density and speed of sound values. All the calculated and derived parameters provide qualitative information regarding the nature of interactions i.e. solute-solute, solute-solvent and solvent-solvent in the solution.
    Biotechnology and Bioengineering
    The occurrence, fate, and distribution of natural and synthetic hormones in different types of wastewater treatment plants in Iran
    Mohammad Mehdi Amin, Bijan Bina, Afshin Ebrahimi, Zeynab Yavari, Farzaneh Mohammadi, Somayeh Rahimi
    2018, 26(5):  1132-1139.  doi:10.1016/j.cjche.2017.09.005
    Abstract ( 542 )   PDF (974KB) ( 17 )  
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    Over the past few years, the presence of steroid estrogens in the environment has become a major concern. In this study, the concentrations of estrone (E1), 17β-estradiol (E2), and 17α-ethinyl estradiol (EE2) were measured in some wastewater treatment plants (WWTPs) in Iran. These samples were collected from the municipal, rural, livestock, commercial, and hospital WWTPs, extracted by dispersive liquid-liquid micro extraction (DLLME) technique, derivatized, and detected by GC/MS. In these treatment plants, various processes including conventional activated sludge (CAS), aerated lagoon (AL), moving bed biofilm reactor (MBBR), and activated sludge with wetland (AS + WL) are used. The highest concentration of hormones was observed in the influents and effluents of livestock, municipal, commercial, and hospital WWTPs, respectively. The maximum elimination rate was obtained in MBBR followed by AS + WL, CAS and AL. The biodegradation and adsorption rates along with adsorption coefficients of lg kd and lg koc were measured for all target compounds.
    Adaptation of intestine-based microbial functions to bioethanol production
    Zhuojun Ying, Xidong Zhang
    2018, 26(5):  1140-1144.  doi:10.1016/j.cjche.2017.10.004
    Abstract ( 572 )   PDF (1890KB) ( 9 )  
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    Animal intestine is a favorable habitat to microbes. It facilitates the evolution of dense and diversified microbial communities that are highly active and persistent throughout life span. Here, we stimulate this unique biosystem to develop high-efficient continuous bio-manufacturing processes. The pig small intestine was explored as a novel bioreactor with industrial Saccharomyces cerevisiae for biofuel production. Results showed that the small intestine was a beneficial material for cell adherence. The cells on the intestine exhibited the abilities of selfimmobilization, self-duplication and self-repairing. Therefore the intestine-based S. cerevisiae could be continuously used for a long time at high metabolic activities. Both the fermentation speed and ethanol yield were improved. This study provides valuable insights into the functions of intestine-based biosystem and should inspire the development of bionic industrial processes. Future dissection of the interface mechanism and design of more bionic materials will make bioprocesses more economically favorable and environmentally sustainable.
    Energy, Resources and Environmental Technology
    Integration of high-solid digestion and gasification to dispose horticultural waste and chicken manure
    Wangliang Li, Changbo Lu, Gaojun An, Yuming Zhang, Yen Wah Tong
    2018, 26(5):  1145-1151.  doi:10.1016/j.cjche.2017.09.020
    Abstract ( 586 )   PDF (1331KB) ( 20 )  
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    To realize full energy recovery from grass and chicken manure (CM), the integration of high-solid anaerobic digestion (HSAD) and gasification was investigated experimentally. The anaerobic biodegradability of grass can be enhanced through codigestion with CM. When the volatile solid (VS) ratio of CM to grass was 20:80, C/N ratio calculated to be 21.70, the cumulative biogas yield was the highest, 237 ml·(g VS)-1. The enhancement of biogas production was attributed to the buffering effects of ammonia and rich trace elements in CM. In semi-continuous systems, when the organic loading rate was 4.0 g VS·L-1·d-1, the HSAD process was stable, with the average biogas yield 168 ml·(g VS)-1. More than 80% fractions of the digestates were volatile matters, which meant that the digestates can be used as feedstock for gasification to produce syngas. The VS ratio of grass to CM had significant overall energy generation through HSAD and gasification. Compared with gasification of digestate, cogasification with woodchips increased syngas yield and low heat value (LHV). Increasing of mass ratio of digestates to woodchips led to the decrease of LHV.
    Enhanced electrokinetic remediation of cadmium-contaminated natural clay using organophosphonates in comparison with EDTA
    Yingying Gu, Albert T. Yeung, Hongjiang Li
    2018, 26(5):  1152-1159.  doi:10.1016/j.cjche.2017.10.012
    Abstract ( 572 )   PDF (3127KB) ( 22 )  
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    Soil contamination by metals is a worldwide environmental problem. Electrokinetic extraction is a promising technology for in-situ remediation of contaminated soils of low hydraulic permeability. However, the extraction of metals is usually hindered by the high buffer capacity of natural soils. Organophosphonates are strong metal chelates as ethylenediaminetetraacetic acid (EDTA) which has been widely studied in the enhancement of electrokinetic remediation. In this study, batch desorption experiments and bench-scale electrokinetic extraction experiments were carried out to study the effect of two organophosphonates, i.e., (nitrilotrimethylene)triphosphonate (NTMP) & (ethylenedinitrilo)-tetramethylenephosphonate (EDTMP), on the extraction of cadmium from a natural clay in comparison with EDTA. Results of the batch desorption experiments showed that more than 75% of the sorbed cadmium could be dissolved into solution using 0.1 mol·L-1 organophosphonates or EDTA in the wide pH range of 1-11. Results of the electrokinetic extraction experiments showed that the cadmium spiked in the specimen migrated towards the anode with the enhancement of NTMP, EDTMP, and EDTA under a constant voltage gradient of approximately 1.0 V·cm-1. Although cadmium mobilization enhanced by EDTA was more efficient than that by the organophosphonates, accumulation of cadmium was observed in the vicinity of the anode. The average removal efficiencies of cadmium from the soil after approximately 5 days of electrokinetic extraction enhanced by 0.1 mol·L-1 NTMP (22.8%) and EDTMP (22.4%) were higher than that by 0.1 mol·L-1 EDTA (15.1%).
    Thermodynamic behaviors of Cu in interaction with chlorine, sulfur, phosphorus and minerals during sewage sludge co-incineration
    Jingyong Liu, Chao Liu, Guang Sun, Wuming Xie, Xiao'e Dang, Jiahong Kuo, Kenlin Chang, Jian Sun, Shuiyu Sun, Musa Buyukada, Fatih Evrendilek
    2018, 26(5):  1160-1170.  doi:10.1016/j.cjche.2017.10.019
    Abstract ( 645 )   PDF (5635KB) ( 29 )  
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    Thermodynamic equilibrium calculations were performed to reveal effects of interactions among Cl, S, P and other minerals on Cu migration. Our results showed that HCl(g), SO2(g) and (P2O5)2(g) were released from the sewage sludge co-incineration. Cl was found to weaken adsorption of Cu by Al2O3, CaO and Fe2O3, while S delayed reactions of Fe2O3 and Al2O3 with Cu, with P having no effect on reactions between the minerals and Cu. Among the coupled systems of Cl, S and P, the co-existences of Cl and S, and Cl, S and P were determined to inhibit Cu volatilization, and the co-existence of Cl and P had an enhancing effect. Cu migration was affected only by S in the S and P system. With the SiO2, CaO and Al2O3 system, both Cl alone and Cl and P led to failed reactions between the minerals and Cu. In the systems of S, S and Cl, S and P, and S, Cl and P, the migration behavior of Cu was mainly affected by S at low temperatures and by Cl at high temperatures, whereas P had no effect on Cu migration during the entire process.
    Effect of industrial microwave irradiation on the physicochemical properties and pyrolysis characteristics of lignite
    Guoshun Zhou, Qunxing Huang, Ben Yu, Hui Tong, Yong Chi, Jianhua Yan
    2018, 26(5):  1171-1178.  doi:10.1016/j.cjche.2017.11.002
    Abstract ( 646 )   PDF (1758KB) ( 20 )  
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    The surface functional groups and pyrolysis characteristics of lignite irradiated by microwave were comparatively studied to evaluate the feasibility of using industrial 915 MHz for lignite drying. The drying kinetics, micro structure, chemical functional groups, re-adsorption properties, and pyrolysis characteristics of the dried coal were respectively analyzed. Results indicated that for typical Chinese lignite studied in this paper, 915 MHz microwave drying was 7.8 times faster than that of the hot air drying. After industrial microwave drying, the sample possessed much higher total specific surface area and specific pore volume than that of air dried sample. The oxygen functional groups and re-adsorption ratio of microwave irradiated coal decreased, showing weakened hydrophilicity. Moreover, during the pyrolysis of the coal dried by hot air and microwave, the yield of tar largely increased from 1.3% to 8.5% and the gas production increased correspondingly. The composition of the tar was also furtherly analyzed, results indicated that Miscellaneous hydrocarbons (HCs) were the main component of the tar, and microwave irradiation can reduce the fraction of polycyclic aromatic hydrocarbons (PAHs) from 26.4% to 22.7%.
    An innovative trigeneration system using biogas as renewable energy
    Grazia Leonzio
    2018, 26(5):  1179-1191.  doi:10.1016/j.cjche.2017.11.006
    Abstract ( 761 )   PDF (1665KB) ( 50 )  
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    One of the ways to decrease the global primary energy consumption and the corresponding greenhouse gas emissions is the application of the combined cooling, heating and power generation technologies, known as trigeneration system. In this research an innovative trigeneration system, composed by an absorption heat pump, a mechanical compression heat pump, a steam plant, and a heat recovery plant is developed. The low temperature heat produced by absorption chiller is sent to a mechanical compression heat pump, that receives process water at low temperature from the heat recovery plant and bring it to higher temperatures. The trigeneration system is fed by biogas, a renewable energy. A design and a simulation of the system are developed by ChemCad 6.3® software. The plant produces 925 kW of electrical energy, 2523 kW of thermal energy and 473 kW of cooling energy, by the combustion of 3280 kW of biogas. Primary energy rate (P.E.R.) is equal 1.04 and a sensitivity analysis is carried out to evaluate the effect of cooling capacity, produced electrical energy and process water temperature. The first has a negative effect, while other parameters have a positive effect on P.E.R. Compared to a cogeneration system, the trigeneration plant produces the 28% higher of power and the 40% lower of carbon dioxide emissions. An economic analysis shows that the plant is economically feasible only considering economic incentives obtained by the use of heat pumps and steam plant at high efficiency. Saving 6431 t·a-1 corresponding to 658000 EUR·a-1 of incentives, the plant has a net present value (N.P.V.) and a pay back period (P.B.P.) respectively equal to 371000 EUR and 4 year. Future works should optimize the process considering cost and energetic efficiency as the two objective functions.
    Cr(Ⅲ) removal from simulated solution using hydrous magnesium oxide coated fly ash: Optimization by response surface methodology (RSM)
    Min Xia, Chunsong Ye, Kewu Pi, Defu Liu, Andrea R. Gerson
    2018, 26(5):  1192-1199.  doi:10.1016/j.cjche.2017.11.008
    Abstract ( 703 )   PDF (1833KB) ( 32 )  
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    Hydrous magnesium oxide coated fly ash (MFA) has environmental remediation potential by providing a substrate for the adsorption of aqueous Cr(Ⅲ). Aqueous Cr(Ⅲ) adsorption onto MFA was examined as a function of MFA dosage, pH and initial Cr(Ⅲ) concentration with the Box-Behnken approach used for experimental design and optimization using response surface methodology (RSM). pH and dosage (dosage and concentration) have significant interactive effects on Cr(Ⅲ) adsorption efficiency. Analysis of variance shows that the response surface quadratic model is highly significant and can effectively predict the experimental outcomes. Cr(Ⅲ) removal efficiency of 98% was obtained using optimized conditions of MFA dosage, pH and initial Cr(Ⅲ) concentration of 1.57 g·L-1, 4.11 and 126 mg·L-1, respectively. Cr(Ⅲ) adsorption onto MFA is mainly attributed to the interaction between Cr(Ⅲ) and the functional group —OH of the hydrous magnesium oxide, in all probability caused by chemisorptions. The results of this study can conduce to reveal the interactions between Cr(Ⅲ) pollutant and MFA characteristics, posing important implications for the cost-effective alternative adsorption technology in the treatment of heavy metal containing wastewater.
    Antioxidant activity of phytosynthesized biomatrix-loaded noble metallic nanoparticles
    Preeti Dauthal, Mausumi Mukhopadhyay
    2018, 26(5):  1200-1208.  doi:10.1016/j.cjche.2017.12.014
    Abstract ( 533 )   PDF (3097KB) ( 16 )  
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    Biofabrication of noble monometallic platinum nanoparticles (Pt-NPs) and bimetallic gold-silver nanoparticles (AuAg-NPs) using aqueous extract of Delonix regia is presented here. Antioxidant activity of biomatrix-loaded metallic nanoparticles is estimated for scavenging of two model radicals i.e., 2,2'-Azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt and 1,1'-Diphenyl-2-picrylhydrazyl. Broad spectral continuum spanning from visible to ultra-violet region (Pt-NPs:30 min) and broad high intensity absorption peak around at 500 nm (AuAg-NPs:10 min) in two different UV-Visible spectra confirmed the biofabrication. Nanoparticles fabricated with distorted spherical shape and crystalline face-centred-cubic geometry. Strong signal around at 2.10 keV (pure-phase platinum) and typical X-ray peaks observed at 2.20 and 3 keV suggested, co-existence and alloying interaction of Au and Ag in AuAg-NPs. ζ potential (-15.2 mV:Pt-NPs and -13.9 mV:AuAg-NPs) values suggested surface adsorption of polyphenolic compounds to provide stability. Nanoparticles exhibited pronounced antioxidant activity against free radicals through their electron/hydrogen transfer ability.
    Materials and Product Engineering
    A simple strategy to synthesize and characterization of zirconium modified PCs/γ-Al2O3
    Chidchon Sararuk, Dan Yang, Guoliang Zhang, Chunshan Li, Suojiang Zhang
    2018, 26(5):  1209-1212.  doi:10.1016/j.cjche.2017.06.017
    Abstract ( 786 )   PDF (976KB) ( 17 )  
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    Crystalline phase is the key factor for catalyst activity. The zirconium modified PCs/γ-Al2O3 samples were prepared through a simple step incipient-wetness impregnation method. The raw materials and samples were characterized by thermogravimetric-differential analysis (TG-DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), temperature-programmed desorption of ammonia and carbon dioxide (NH3-and CO2-TPD). The effects of calcination temperature and zirconium content on structure, chemical transformation, and acidity-basicity were investigated. Calcination temperature exhibited the major effect on the crystalline phase of samples. The new phase of Al0.1Zr0.9O1.95 was exhibited which was above 650℃. In addition, zirconium content was influenced by the acidic and basic properties of the surface. The acidity and basicity of the ZrPCs/γ-Al2O3 sample increased with the increasing of zirconium content.
    Thermal conductivity of PVDF/PANI-nanofiber composite membrane aligned in an electric field
    Hong Guo, Xin Li, Ziyi Wang, Bao'an Li, Jixiao Wang, Shichang Wang
    2018, 26(5):  1213-1218.  doi:10.1016/j.cjche.2017.12.015
    Abstract ( 829 )   PDF (2691KB) ( 24 )  
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    Poly(vinylidene fluoride) (PVDF) is a semi-crystalline thermoplastic polymer with excellent thermal stability, electrochemical stability and corrosion resistance, which has been widely studied and applied in industrial nonmetallic heat exchanger and piezoelectric-film sensor. In this study, polyaniline (PANI) nanofibers were synthesized using dodecylbenzene sulfonic acid as the surfactant. The obtained PANI nanofibers were blended in PVDF matrix to enhance thermal conductivity and tensile strength of composite materials. Electric field was applied for the orientation of membrane structure during membrane formation. Scanning electron microscope (SEM) images exhibited that the PANI nanofibers were well-dispersed in the composite membranes. The structure of composite membranes was more orderly after alignment. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) indicated that the content of PANI nanofibers contributed to the transformation of PVDF from α-phase to β-phase. Both the tensile strength and thermal conductivity of composite membranes were significantly improved. This tendency was further enhanced by the application of electric field. The maximum tensile strength was obtained when the content of PANI nanofibers was 3 wt%, which was 46.44% higher than that of pure PVDF membrane. The maximum thermal conductivity of composite membranes after alignment was 84.5% greater than that of pure PVDF membrane when the content of PANI nanofibers was 50 wt%. The composite membrane is a promising new potential material in heat transfer field and the mechanism explored in this study would be informative for further development of similar thermal conductive polymeric materials.
    Morphological, mechanical and thermal properties of cyanate ester/benzoxazine resin composites reinforced by silane treated natural hemp fibers
    Abdeldjalil Zegaoui, Ruikun Ma, Abdul Qadeer Dayo, Mehdi Derradji, Jun Wang, Wenben Liu, Yile Xu, Wan'an Cai
    2018, 26(5):  1219-1228.  doi:10.1016/j.cjche.2018.01.008
    Abstract ( 633 )   PDF (11453KB) ( 9 )  
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    This present study deals with the reinforcement of thermosetting resin blends composed of cyanate ester (CE) and benzoxazine (BOZ) resins with natural hemp fibers (NHFs). These NHFs were initially treated by using a silane coupling agent (SCA) in order to chiefly enhance their distributions as well as adhesions within the CE/BOZ resin matrix, then incorporated with various weight amounts ranging from 5 wt% to 20 wt% with a regular interval of 5 wt%. The obtained results showed that at the maximum treated fiber loading (20 wt%), distinctive enhancements in the mechanical properties in terms of flexural strength and microhardness were obtained. Besides, the thermal stability and glass transition temperature (Tg) were appreciably enhanced and were higher than those of the pure CE/BOZ resin properties. With respect to the astonishing properties of the NHFs, these enhancements could be possibly due to the good dispersion and adhesion of the treated NHFs inside the CE/BOZ resin achieved upon using the SCA. Therefore, we believe herein that these renewable and cheap NHFs have considerable potential to be used as reinfocer materials for CE/BOZ resin composites to be used in various industrial sectors.
    Controlling dispersion and morphology of MoS2 nanospheres by hydrothermal method using SiO2 as template
    Zhenwei Zhang, Peng Wang, Fei Wang, Yaqing Li, Wei Lu, Xingmao Jiang, Xia Gui, Zhi Yun
    2018, 26(5):  1229-1234.  doi:10.1016/j.cjche.2017.12.016
    Abstract ( 635 )   PDF (10612KB) ( 11 )  
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    Monodispersed MoS2 nanospheres were successfully synthesized by using SiO2 as hard template. The size and morphology of the MoS2 nanospheres could be finely controlled by the content of SiO2 and sulfur precursors. Furthermore, higher surface area of monodispersed MoS2 nanospheres exhibited high reaction rate for hydrodesulfurization (HDS) of dibenzenethiophene (DBT).