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Table of Content
28 August 2020, Volume 28 Issue 8
    Emerging applications of nanomaterials in chemical enhanced oil recovery: Progress and perspective
    Najeebullah Lashari, Tarek Ganat
    2020, 28(8):  1995-2009.  doi:10.1016/j.cjche.2020.05.019
    Abstract ( )   PDF (2050KB) ( )  
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    In enhanced oil recovery, different chemical methods utilization improves hydrocarbon recovery due to their fascinating abilities to alter some critical parameters in porous media, such as mobility control, the interaction between fluid to fluid, and fluid to rock surface. For decades the use of surfactant and polymer flooding has been used as tertiary recovery methods. In the current research, the inclusion of nanomaterials in enhanced oil recovery injection fluids solely or in the presence of other chemicals has got colossal interest. The emphasis of this review is on the applicability of nanofluids in the chemical enhanced oil recovery. The responsible mechanisms are an increment in the viscosity of injection fluid, decrement in oil viscosity, reduction in interfacial and surface tension, and alteration of wettability in the rock formation. In this review, important parameters are presented, which may affect the desired behavior of nanoparticles, and the drawbacks of nanofluid and polymer flooding and the need for a combination of nanoparticles with the polymer are discussed. Due to the lack of literature in defining the mechanism of nanofluid in a reservoir, this paper covers majorly all the previous work done on the application of nanoparticles in chemical enhanced oil recovery at home conditions. Finally, the problems associated with the nano-enhanced oil recovery are outlined, and the research gap is identified, which must be addressed to implement polymeric nanofluids in chemical enhanced oil recovery.
    Recent advances in non-thermal plasma (NTP) catalysis towards C1 chemistry
    Huanhao Chen, Yibing Mu, Shanshan Xu, Shaojun Xu, Christopher Hardacre, Xiaolei Fan
    2020, 28(8):  2010-2021.  doi:10.1016/j.cjche.2020.05.027
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    C1 chemistry mainly involves the catalytic transformation of C1 molecules (i.e., CO, CO2, CH4 and CH3OH), which usually encounters thermodynamic and/or kinetic limitations. To address these limitations, non-thermal plasma (NTP) activated heterogeneous catalysis offers a number of advantages, such as relatively mild reaction conditions and energy efficiency, in comparison to the conventional thermal catalysis. This review presents the state-of-the-art for the application of NTP-catalysis towards C1 chemistry, including the CO2 hydrogenation, reforming of CH4 and CH3OH, and water-gas shift (WGS) reaction. In the hybrid NTP-catalyst system, the plasma-catalyst interactions are multifaceted. Accordingly, this review also includes a brief discussion on the fundamental research into the mechanisms of NTP activated catalytic C1 chemistry, such as the advanced characterisation methods (e.g., in situ diffuse reflectance infrared Fourier transform spectroscopy, DRIFTS), temperatureprogrammed plasma surface reaction (TPPSR), kinetic studies. Finally, prospects for the future research on the development of tailor-made catalysts for NTP-catalysis systems (which will enable the further understanding of its mechanism) and the translation of the hybrid technique to practical applications of catalytic C1 chemistry are discussed.
    Busting the efficiency of SAPO-34 catalysts for the methanol-to-olefin conversion by post-synthesis methods
    Guoju Yang, Ji Han, Yujun Huang, Xiaoxin Chen, Valentin Valtchev
    2020, 28(8):  2022-2027.  doi:10.1016/j.cjche.2020.05.028
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    As an effective non-petroleum based process for producing light olefins, the methanol-to-olefin (MTO) route has become an indispensable alternative to the industrial production of light olefins. The silicoaluminophosphate SAPO-34 zeolite (CHA-type structure) has proven to be an efficient industrial catalyst for the production of ethylene and propylene by the MTO reaction. However, the inherent structure and related diffusion limitations of SAPO-34 limit the mass transport and thus cause rapid deactivation of the catalyst. Fabrication of hierarchical SAPO-34 zeolite is one of the most effective strategies to address the intrinsic diffusion limitation. As simple, inexpensive, and efficient approach, the post-synthetic route has attracted considerable attention and widely used to introduce secondary meso-/macropores into the microporous SAPO-34 material. Significant effort has been dedicated to the development of post-synthesis strategies to prepare hierarchical SAPO-34 zeolite, thereby enhancing its catalytic performance in the MTO process. This mini-review addresses the post-synthesis preparation of hierarchical SAPO-34 catalysts and their MTO performance. Furthermore, some current problems and prospects of the post-synthesis route to hierarchical SAPO-34 catalysts are also revised. We expect this minireview to inspire the more efficient preparation of hierarchical SAPO-34 catalysts for the MTO process.
    Microenvironmental engineering: An effective strategy for tailoring enzymatic activities
    Yifei Zhang, Henry Hess
    2020, 28(8):  2028-2036.  doi:10.1016/j.cjche.2020.04.010
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    Rationally, engineering a favorable physicochemical microenvironment for enzymes has recently emerged as an effective strategy to improve their catalytic performance. In this review, we discuss four microenvironmental effects according to the mechanism of action: localizing and excluding reactants and regulators, regulating microenvironmental pH, creating a water-like microenvironment, and increasing the local temperature. These mechanisms are enzyme-independent and can in principle be used in combination to tailor enzyme behaviors, offering new approaches to enabling, enhancing, and regulating enzyme catalysis in diverse applications without the need for genetic engineering.
    Multienzyme co-immobilization-based bioelectrode: Design of principles and bioelectrochemical applications
    Ranran Wu, Haiyan Song, Yuanming Wang, Lei Wang, Zhiguang Zhu
    2020, 28(8):  2037-2050.  doi:10.1016/j.cjche.2020.04.003
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    Enzyme cascade reactions play significant roles in bioelectrochemical processes because they permit more complex reactions. Co-immobilization of multienzyme on the electrode could help to facilitate substrate/intermediate transfer among different enzymes and electron transfer from enzyme active sites to the electrode with high stability and retrievability. Different co-immobilization strategies to construct multienzyme bioelectrodes have been widely reported, however, up to now, they have barely been reviewed. In this review, we focus on recent state-of-the-art techniques for constructing co-immobilized multienzyme electrodes including random and positional co-immobilization. Particular attention is given to strategies such as multienzyme complex and surface display. Cofactor co-immobilization on the electrode is also crucial for the enhancement of catalytic reaction and electron transfer, yet, few studies have been reported. The up-to-date advances in bioelectrochemical applications of multienzyme bioelectrodes are also presented. Finally, key challenges and future perspectives are discussed.
    Fatty acid hydratase for value-added biotransformation: A review
    Yan Zhang, Bekir Engin Eser, Peter Kristensen, Zheng Guo
    2020, 28(8):  2051-2063.  doi:10.1016/j.cjche.2020.02.008
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    The synthesis of hydroxy fatty acids (HFAs) from renewable oil feedstock by addition of water onto C=C bonds has attracted great attention in recent years. Given that selective asymmetric hydration of non-activated C=C bonds has been proven difficult to achieve with chemical catalysts, enzymatic catalysis by fatty acid hydratases (FAHs) presents an attractive alternative approach to produce value-added HFAs with high regio-, enantioand stereospecificity, as well as excellent atom economy. Even though FAHs have just been investigated as a potential biocatalyst for a decade, remarkable information about FAHs in different aspects is available; however, a comprehensive review has not been archived. Herein, we summarize the research progresses on biochemical characterization, structural and mechanistic determination, enzyme engineering, as well as biotechnological application of FAHs. The current challenges and opportunities for an efficient utilization of FAHs in organic synthesis and industrial applications are critically discussed.
    Fluid Dynamics and Transport Phenomena
    CFD investigation of the agitation in the desupersaturation during the wet-process phosphoric acid (WPPA) process
    Asmaa Hadane, Lhachmi Khamar, Saad Benjelloun, Abderrahman Nounah, Mohammed Khamar
    2020, 28(8):  2064-2074.  doi:10.1016/j.cjche.2020.03.041
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    Desupersaturation is a complex cooling operation that involves hydrodynamic, thermal and mechanical phenomena. This process requires continuous agitation to avoid fouling problems and sludge deposition. The current work aims to investigate the well mixedness in the desupersaturation tank for optimal performance. For this purpose, a multi-fluid CFD study was conducted based on the Euler-Euler modeling approach, considering a multiphase flow involving a liquid phase (phosphoric acid) and a poly-dispersed solid phase, i.e. a sludge with three different sizes where each size is considered as a separate phase. First, the hydrodynamic behavior of the flow within the agitated desupersaturator is analyzed through the investigation of the velocity fields as well as the power and pumping numbers, to determine both the agitator capacity to pump the flow and its power consumption during the operation. Then, in order to assess the mixture homogeneity, we evaluated the solid suspension in the desupersaturation reactor following conventional methods and two new proposed methodologies: the first approach is to evaluate the suspension quality in the mixing system by compartment and the second consists on the assessment of the uniform convergence of the solid concentration. Furthermore, we calculated the time required to achieve a full suspension at different solid concentrations. On other hand, we conducted a detailed analysis of the solid distribution dependency on the impeller rotational speed at different solid volume fraction, which allows a good understanding of the parameters controlling the homogenization in the desupersaturator.
    Separation Science and Engineering
    Influence of slug flow on flow fields in a gas-liquid cylindrical cyclone separator: A simulation study
    Xiaoming Luo, Jing Ren, Tong Chen, Yibin Wang, Yuling Lü, Limin He
    2020, 28(8):  2075-2083.  doi:10.1016/j.cjche.2020.03.026
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    A simulation method for slug flow based on the VOF multiphase flow model was implemented in ANSYS® Fluent via a user-defined function (UDF) and applied to the dissipation of liquid slugs in the inlet pipe of a gas-liquid cylindrical cyclone (GLCC) separator while varying the expanding diameter ratio and angle of inclination. The dissipation of liquid slug in inlet pipe is analyzed under different expanding diameter ratios and inclination angles. In the inlet pipe, it is found that increasing expanding diameter ratio and inclination angle can reduce the liquid slug stability and enhancing the effect of gravity, which is beneficial to slug flow dissipation. In the cylinder, increasing the expanding diameter ratio can significantly reduce the liquid carrying depth of the gas phase but result in a slightly increase of the gas content in the liquid phase space. Moreover, increasing the inclination angle results in a decrease in the carrying depth of liquid in the vapor phase, but enhances gas-liquid mixing and increases the gas-carrying depth in the liquid phase. Taking into consideration the dual effects of slug dissipation in the inlet pipe and carrying capacity of gas/liquid spaces in the cylinder, the optimal expanding diameter ratio and inclination angle values can be determined.
    Catalysis, Kinetics and Reaction Engineering
    Systematic study of H2 production from catalytic photoreforming of cellulose over Pt catalysts supported on TiO2
    Lan Lan, Yan Shao, Yilai Jiao, Rongxin Zhang, Christopher Hardacre, Xiaolei Fan
    2020, 28(8):  2084-2091.  doi:10.1016/j.cjche.2020.03.030
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    Hydrogen (H2) production from photocatalytic reforming of cellulose is a promising way for sustainable H2 to be generated. Herein, we report a systematic study of the photocatalytic reforming of cellulose over Pt/m-TiO2 (i.e. mixed TiO2, 80% of anatase and 20% of rutile) catalysts in water. The optimum operation condition was established by studying the effect of Pt loading, catalyst concentration, cellulose concentration and reaction temperature on the gas production rate of H2 (rH2) and CO2 (rCO2), suggesting an optimum operation condition at 40 ℃ with 1.0 g·L-1 of cellulose and 0.75 g·L-1 of 0.16-Pt/m-TiO2 catalyst (with 0.16 wt% Pt loadting) to achieve a relatively sound photocatalytic performance with rH2 = 9.95 μmol·h-1. It is also shown that although the photoreforming of cellulose was operated at a relatively mild condition (i.e. with an UV-A lamp irradiation at 40 ℃ in the aqueous system), a low loading of Pt at ~0.16 wt% on m-TiO2 could promote the H2 production effectively. Additionally, by comparing the reaction order expressed from both rH2 (a1) and rCO2 (a2) with respect to cellulose and water, the possible mechanism of H2 production was proposed.
    Continuous, homogeneous and rapid synthesis of 4-bromo-3-methylanisole in a modular microreaction system
    Pei Xie, Kai Wang, Jian Deng, Guangsheng Luo
    2020, 28(8):  2092-2098.  doi:10.1016/j.cjche.2020.06.001
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    4-Bromo-3-methylanisole is mainly used to synthesize black fluorane dye (2-anilino-3-methyl-6- dibutylaminofluorane, ODB-2), which is one of the most important heat and pressure-sensitive dyes in the manufacture of thermal papers. Compared to the industrial heterogeneous batch process, a continuous homogeneous bromination technology in a modular microreaction system has been developed, and 4-bromo-3-methylanisole has been successfully prepared through high-selective mono-bromination of 3-methylanisole with Br2 solution in CHCl3. In optimal conditions, the content of bis-brominated byproducts can be controlled less than 0.5%, which is superior to the industrial standard with 99.5% 3-methylanisole conversion at very short residence time and mild reaction temperature.
    Modeling the rate of corrosion of carbon steel using activated diethanolamine solutions for CO2 absorption
    Lubna Ghalib, Ahmed Abdulkareem, Brahim Si Ali, Shaukat Ali Mazari
    2020, 28(8):  2099-2110.  doi:10.1016/j.cjche.2020.03.006
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    A mechanistic model is developed to investigate the influence of an activator on the corrosion rate of carbon steel in the absorption processes of carbon dioxide (CO2). Piperazine (PZ) is used as the activator in diethanolamine (DEA) aqueous solutions. The developed model for corrosion takes into consideration the effect of fluid flow, transfer of charge and diffusion of oxidizing agents and operating parameters like temperature, activator concentration, CO2 loading and pH. The study consists of two major models: Vapor-liquid Equilibrium (VLE) model and electrochemical corrosion model. The electrolyte-NRTL equilibrium model was used for determination of concentration of chemical species in the bulk solution. The results of speciation were subsequently used for producing polarization curves and predicting the rate of corrosion occurring at the surface of metal. An increase in concentration of activator, increases the rate of corrosion of carbon steel in mixtures of activated DEA.
    Application of kinetics and computational fluid dynamics in pinene isomerization
    Jionghua Xiang, Litao Zhu, Zhenghong Luo
    2020, 28(8):  2111-2120.  doi:10.1016/j.cjche.2020.03.021
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    A reliable kinetic model to describe the effects of various factors on the reaction rate and selectivity of pinene isomerization is developed. Furthermore, computational fluid dynamics (CFD) is applied to simulate the solid- liquid dispersion in reactor. The catalyst TiM is obtained by improving the composition and structure of hydrated titanium dioxide. The kinetic equation of pinene isomerization is deduced based on reaction mechanism and catalyst deactivation model. The kinetic equation of pinene isomerization reaction is fitted, and the results show that the fitted equation is correlated with the experimental data. The rate and selectivity of pinene isomerization reaction are affected by the amount of catalyst, deactivation of catalyst, structure of catalyst, reaction temperature and water content of catalyst. The solid-liquid distribution of the reactor is calculated by computational fluid dynamics numerical simulation, and the solid-liquid dispersion in commercial scale reactor is more uniform than that in lab-scale reactor.
    Process Systems Engineering and Process Safety
    Systematic exploration of the applicability of the idiomatic vapor balance rule to distillation column consolidation
    Shuo Zhang, Yifan Sun, Yiqing Luo, Hongzhe Hou, Xigang Yuan
    2020, 28(8):  2121-2130.  doi:10.1016/j.cjche.2020.05.018
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    For N-component distillation (N ≥ 3), consolidation between different column sections is an inevitable manipulation when synthesizing complex distillation configurations. In the consolidation, the idiomatic vapor balance (IVB) rule, in which the larger vapor flowrate in the two columns before consolidation will be chosen as the balanced vapor flowrate at the consolidation point, has been widely used. However, the applicability of the IVB rule has not been verified, which is of essential importance to the accuracy of the distillation configuration synthesis. In the present study, the applicability of the IVB rule to distillation column consolidation was systematically explored by rigorous method for the first time. First, the separation of ideal and non-ideal three-component mixtures with variable compositions was studied, and the optimized configurations before and after consolidation were determined by a rigorous method. The results indicated that for the separation of an ideal mixture, the IVB rule was applicable for the whole composition range, while for the separation of a non-ideal mixture, the IVB rule was only applicable for very limited composition range. Finally, two cases of synthesizing distillation configurations for the separation of non-ideal mixtures were studied to verify the remarkable deviations the IVB rule may cause. The results indicated that the applicability of the shortcut method using the IVB rule to the distillation configuration synthesis depended on the composition of the non-ideal mixture, and a remarkable error might result and the truly optimal configuration might be missed if the IVB rule is applied to a non-ideal mixture.
    Research on thermal risk and decomposition behavior of methyl nitrite
    Haoyu Zhai, Shaomeng Wang, Diankun Chen, Xuanying Cheng, Chuanxin Xie
    2020, 28(8):  2131-2136.  doi:10.1016/j.cjche.2020.05.031
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    The thermal hazards of methyl nitrite (MN) were investigated in the present study. The determination and evaluation of MN decomposition were conducted using a C600 micro thermometer. The thermal runaway reaction characteristics of the compound under different initial pressures were obtained using a VSP2 calorimeter. The kinetic parameters of MN were obtained by regression fitting and calculation of the microthermal experimental data. The experimental and calculated results demonstrated that the potential explosion risk of MN is very high. In addition, there was a high energy barrier in the early stage of the uncontrolled decomposition of MN; however, once the decomposition reaction was initiated, the subsequent decomposition was easily conducted. Under the conditions of adiabatic simulation, the possibility that the reaction was uncontrolled increases with the initial temperature and pressure of the system, and there is a great potential safety risk.
    Chemical Engineering Thermodynamics
    Solubility measurement and prediction of phase equilibria in the quaternary system LiCl + NaCl + KCl + H2O and ternary subsystem LiCl + NaCl + H2O at 288.15 K
    Ruizhi Cui
    2020, 28(8):  2137-2141.  doi:10.1016/j.cjche.2020.05.020
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    Using isothermal dissolution method, the phase equilibrium relationship in quaternary system LiCl + NaCl + KCl + H2O and the ternary subsystem LiCl + NaCl + H2O at 288.15 K were investigated. Each phase diagram of two systems was drawn. The phase diagram of LiCl + NaCl + H2O system contains two solid phase regions of crystallization LiCl·2H2O and NaCl. In the phase diagram of LiCl + NaCl + KCl + H2O system, there are three crystallization regions: LiCl·2H2O, NaCl and KCl respectively. In this paper, the solubilities of phase equilibria in two systems were calculated by Pitzer's model at 288.15 K. The predicted phase diagrams generally agree with the experimental phase diagrams.
    Optimization of FX-70 refrigerant evaporative heat transfer and fluid flow characteristics inside the corrugated tubes using multi-objective genetic algorithm
    Mirollah Hosseini, Hamid Hassanzadeh Afrouzi, Sina Yarmohammadi, Hossein Arasteh, Davood Toghraie, A. Jafarian Amiri, Arash Karimipour
    2020, 28(8):  2142-2151.  doi:10.1016/j.cjche.2020.05.036
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    In this study, the heat transfer optimization (evaporation) and the specification of the FX-70 zeotropic refrigerant flow inside a corrugated pipe have been investigated. Despite the low HTC (HTC), this type of refrigerant is highly applicable in low or medium temperature engineering systems during the evaporation process. To eliminate this defect, high turbulence and proper mixing are required. Therefore, using heat transfer (HT) augmentation methods will be necessary and effective. In order to find the most favorable operating conditions that lead to the optimum combination of pressure drop (PD) and HTC, empirical data, neural networks, and genetic algorithms (GA) for multi-objective (MO) (NSGA II) are used. To investigate the mentioned cases, the geometric parameters of corrugated pipes, vapor quality, and mass velocity of refrigerant were studied. The results showed that with vapor quality higher than 0.8 and corrugation depth and pitch of 1.5 and 7 mm, respectively, we would achieve the desired optimum design.
    Biotechnology and Bioengineering
    Immobilized laccase on magnetic nanoparticles for enhanced lignin model compounds degradation
    Xinyan Chen, Bin He, Mi Feng, Dingwei Zhao, Jian Sun
    2020, 28(8):  2152-2159.  doi:10.1016/j.cjche.2020.02.028
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    As a natural aromatic polymer, lignin has great potential but limited industrial application due to its complex chemical structure. Among strategies for lignin conversion, biodegradation has attracted promising interest recently in term of efficiency, selectivity and mild condition. In order to overcome the issues of poor stability and non-reusability of enzyme in the biodegradation of lignin, this work explored a protocol of immobilized laccase on magnetic nanoparticles (MNPs) with rough surfaces for enhanced lignin model compounds degradation. Scanning electron microscope with energy dispersive spectrometer (SEM-EDS), flourier transformation infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA) were utilized to characterize the immobilization of laccase. The results showed a maximum activity recovery of 64.7% towards laccase when it was incubated with MNPs and glutaraldehyde (GA) with concentrations of 6 mg·ml-1 and 7.5 mg·ml-1 for 5 h, respectively. The immobilized laccase showed improved thermal stability and pH tolerance compared with free laccase, and remained more than 80% of its initial activity after 20 days of storage at 4 ℃. In addition, about 40% residual activity of the laccase remained after 8 times cycles. Gas chromatography-mass spectrometry (GC-MS) was utilized to characterize the products of lignin model compound degradation and activation, and the efficiency of immobilized laccase was calculated to be 1-5 times that of free laccase. It was proposed that the synergistic effect between MNPs and laccase displays an important role in the enhancement of stability and activity in lignin model compound biodegradation.
    Highly efficient synthesis of (R)-1,3-butanediol via anti-Prelog reduction of 4-hydroxy-2-butanone with absolute stereoselectivity by a newly isolated Pichia kudriavzevii
    Han Zu, Hui Zhang, Anwen Fan, Jie Gu, Yao Nie, Pengjie Luo, Yan Xu
    2020, 28(8):  2160-2166.  doi:10.1016/j.cjche.2019.12.015
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    (R)-1,3-butanediol is an important pharmaceutical intermediate, and the synthesis of (R)-1,3-butanediol using green biological methods has recently been of interest for industrial application. Here, a novel strain QC-1 that efficiently transforms 4-hydroxy-2-butanone to (R)-1,3-butanediol was isolated from soil samples. Based on morphological, physiological, and biochemical tests and 5.8S-internal transcribed spacer sequencing, the strain was identified as Pichia kudriavzevii QC-1. The reaction conditions were optimized to 35 ℃, pH 8.0, rotation speed 200 rpm, and 6:5 mass ratio of glucose to 4-hydroxy-2-butanone. Evaluation of the effects of 4-hydroxy- 2-butanone concentrations on yield and cell survival rate showed that 85.60 g·L-1 product accumulated, with an enantiomeric excess of more than 99%, when 30 g·L-1 4-hydroxy-2-butanone was added at 0, 10, and 30 h in a 3-L bioreactor. Thus, strain QC-1 showed excellent catalytic activity and stereoselectivity for the synthesis of (R)-1,3-butanediol from 4-hydroxy-2-butanone.
    Efficient production of cyclic adenosine monophosphate from adenosine triphosphate by the N-terminal half of adenylate cyclase from Escherichia coli
    Chen Ma, Jing Wang, Xuelin Wang, Dandan Mai, Yuqi Jin, Kequan Chen, Xin Wang, Pingkai Ouyang
    2020, 28(8):  2167-2172.  doi:10.1016/j.cjche.2020.01.003
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    In this study, we aimed at developing an efficient biocatalytic process for bio-production of cyclic adenosine monophosphate (cAMP) from adenosine triphosphate (ATP). First, adenylate cyclase from Escherichia coli MG1655 (EAC) and Bordetella Pertussis (BAC) were expressed in E. coli BL21 (DE3) and comparatively analyzed for their activities. As a result, EAC from E. coli MG1655 exhibited a higher activity. However, amount of EAC were obtained in an insoluble form. Therefore, we expressed the first 446 amino acids of EAC (EAC446) to avoid the inclusion body. The effects of induction temperature, incubation time, and incubation pH were further evaluated to improve the expression of EAC446. Subsequently, the reaction process for the production of cAMP with ATP as a starting material was investigated. As none of cAMP was detected in the whole-cell based biocatalytic process, the reaction catalyzed by the crude enzyme was determined for cAMP production. What's more, the reaction temperature, reaction pH, metal ion additives and substrate concentration was optimized, and the maximum cAMP production of 18.45 g·L-1 was achieved with a yield of 95.4% after bioconversion of 6 h.
    Immobilization of urease in metal-organic frameworks via biomimetic mineralization and its application in urea degradation
    Xiao Liang, Qing Li, Zhiyuan Shi, Shaowei Bai, Quanshun Li
    2020, 28(8):  2173-2180.  doi:10.1016/j.cjche.2020.01.014
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    Enzyme immobilization has been accepted as an efficient technique for improving the stability and recyclability of enzymes. Herein, biomimetic mineralization strategy was employed to achieve the immobilization of urease in a type of metal-organic frameworks (zeolite imidazolate framework-8, ZIF-8), and the immobilized enzyme urease@ZIF-8 was systematically evaluated for its structure, activity, stability and recyclability, using the hydrolysis of urea as a model. The entrapment of urease was found to be realized in a synchronous manner with the formation of ZIF-8 crystal. The loading of urease in ZIF-8 was measured to be ca. 10.6% through the bicinchoninic acid (BCA) protein assay. The encapsulated urease could efficiently maintain its native conformation, which endowed the immobilized urease with excellent activity and stability, even in harsh conditions (e.g., in the presence of trypsin, acidic or alkali conditions, or at high temperature). Further, urease@ ZIF-8 exhibited good recyclability during the degradation of urea, in which it could keep 58.86% of initial activity after being used for 5 cycles. Thus, biomimetic mineralization could be potentially utilized as a promising method to prepare immobilized ureases with superior activity, stability and recyclability, thereby facilitating the construction of efficient catalysts for industrial biocatalysis and biosensing.
    Using multiple site-directed modification of epoxide hydrolase to significantly improve its enantioselectivity in hydrolysis of rac-glycidyl phenyl ether
    Yao Li, Xiaoyang Ou, Zewang Guo, Minhua Zong, Wenyong Lou
    2020, 28(8):  2181-2189.  doi:10.1016/j.cjche.2020.03.025
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    The epoxide hydrolase gene (SpEH) from Sphingomonas sp. HXN-200 was synthesized and expressed in robust Escherichia coli cells that had a dual protection system. The enantioselectivity (E-value) of the recombinant SpEH was 7.7 and the yield of the remaining (R)-PGE was 24.3% for the hydrolysis of racemic phenyl glycidyl ether (rac-PGE). To improve the catalytic properties of SpEH, the site-directed mutagenesis was carried out based on homology modeling, sequence alignment and molecular docking. Six residues (V195, V196, F218, N226, Q312, and M332) near the active site were mutated to hydrophobic amino acids and the positive mutations were selected for combinatorial mutation. The optimal mutant SpEHV196A/N226A/M332A had an enhanced E-value of 21.2 and a specific activity of 4.57 U·mg-1-wet cells, which were 2.8-, and 2.3-fold higher than those of wild-type SpEH. The optimal temperature and pH for purified SpEHV196A/N226A/M332A to catalyze the hydrolysis of rac-PGE were 25 ℃ and 7.0 with 200 U·mg-1. The enantioselectivity and yield of the remaining (R)-PGE of E. coli_SpEHV196A/N226A/M332A increased from 7.7 to 21.2 and 24.3% to 40.9%, respectively. The molecular docking and kinetic parameter analyses showed that SpEHV196A/N226A/M332A has a greater affinity toward (S)-PGE than (R) - PGE, and that it was more difficult for the O-atom of ASP170 to achieve the nucleophilic attack on the Cα of (R)-PGE, resulting in its improved enantioselectivity.
    Enhancement of α-ketoisovalerate production by relieving the product inhibition of L-amino acid deaminase from Proteus mirabilis
    Shanshan Pei, Xiaobo Ruan, Jia Liu, Wei Song, Xiulai Chen, Qiuling Luo, Liming Liu, Jing Wu
    2020, 28(8):  2190-2199.  doi:10.1016/j.cjche.2020.04.009
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    L-Amino acid deaminase (LAAD) is a key enzyme in the deamination of L-valine (L-val) to produce α- ketoisovalerate (KIV). However, the product inhibition of LAAD is a major hindrance to industrial KIV production. In the present study, a combination strategy of modification of flexible loop regions around the product binding site and the avoidance of dramatic change of main-chain dynamics was reported to reduce the product inhibition. The four mutant PM-LAADM4 (PM-LAADS98A/T105A/S106A/L341A) achieved a 6.2-fold higher catalytic efficiency and an almost 6.7-fold reduction in product inhibition than the wild-type enzyme. Docking experiments suggested that weakened interactions between the product and enzyme, and the flexibility of the “lid” structure relieved LAAD product inhibition. Finally, the whole-cell biocatalyst PM-LAADM4 has been applied to KIV production, the titer and conversion rate of KIV from L-val were 98.5 g·L-1 and 99.2% at a 3-L scale, respectively. These results demonstrate that the newly engineered catalyst can significantly reduce the product inhibition, that making KIV a prospective product by bioconversion method, and also provide the understanding of the mechanism of the relieved product inhibition of PM-LAAD.
    Energy, Resources and Environmental Technology
    Acoustic emission detection of slag performance in coal gasifiers
    Zhengliang Huang, Peng Zhang, Yao Yang, Jingyuan Sun, Jingdai Wang, Yongrong Yang, Chenghao Huang, Zhixiong Huang
    2020, 28(8):  2200-2207.  doi:10.1016/j.cjche.2020.05.038
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    This work first investigated the detection of slags, slag pool liquid level, and slag accumulation height in laboratory scale based on acoustic emission (AE) detection, and further tried the feasibility of this method in an industrial scale coal gasifier. Results show that the energy and variance of acoustic signals can realize the accurate detection of large slag (criterion: E > 1.5E0, S > 1.2S0), and the average relative error is only 0.28%. The acoustic energy in the frequency range of 20-40 kHz is defined as the characteristic energy, which can realize the accurate detection of slag accumulation height and slag pool liquid level, and the average relative error is only 3.94%. Furthermore, AE detection also realize accurate detection of large slag in an industrial scale gasifier and the acoustic signals at slag screen can be used to realize the early warning of the slag collapse (5 h earlier).
    A novel method for extracting vanadium by low temperature sodium roasting from converter vanadium slag
    Rongrui Deng, Hao Xiao, Zhaoming Xie, Zuohua Liu, Qiang Yu, Geng Chen, Changyuan Tao
    2020, 28(8):  2208-2213.  doi:10.1016/j.cjche.2020.03.038
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    Long-term high temperature in conventional vanadium extraction process would cause particles to be sintered and wrapped, thus reducing extraction efficiency of vanadium. Based on the purpose of directional conversion and process intensification, this work proposed a combination of low temperature sodium roasting and high efficiency selective oxidation leaching in vanadium extraction. The investigation of the reaction mechanism suggested that the structure of vanadium slag was changed by roasting, which also caused the fracture of spinel. The addition of MnO2 promoted the directional oxidation of low-valent vanadium into high valence. It also found that Na2S2O8 could oxidize low-valent vanadium effectively in leaching. The leaching efficiency of vanadium reached 87.74% under the optimum conditions, including a roasting temperature of 650 ℃, a roasting time of 2.0 h, a molar ratio of sodium-to-vanadium of 0.6, a MnO2 (roasting additive) dosage of 5 wt% and a Na2S2O8 (leaching oxidant) dosage of 5 wt%. This percentage is 7.18% higher than that of direct roasting-andleaching under the same conditions.
    Materials and Product Engineering
    Mixed phase sodium manganese oxide as cathode for enhanced aqueous zinc-ion storage
    Xinyu Wang, Xinghua Qin, Qiongqiong Lu, Mingming Han, Ahmad Omar, Daria Mikhailova
    2020, 28(8):  2214-2220.  doi:10.1016/j.cjche.2020.05.015
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    Aqueous zinc-ion batteries have been regarded as a promising alternative to large-scale energy storage, due to associated low-cost, improved safety and environmental friendliness. However, a high-performance cathode material for both rate capability and specific capacity is still a challenge. One kind of the more promising candidates are sodium manganese oxide (NMO) materials, although they suffer from individual issues and need to be further improved. Herein, we present a novel mixed phase NMO material composed of nearly equal amounts of Na0.55Mn2O4 and Na0.7MnO2.05. The structured configuration with particle size of 200-500 nm is found to be beneficial towards improving the ion diffusion rate during the charge/discharge process. Compared with Na0.7MnO2.05 and Na0.55Mn2O4, the mixed phase NMO demonstrates an enhanced rate capability and excellent long-term cycling stability with a capacity retention of 83% after 800 cycles. More importantly, the system also delivers an impressive energy density and power density, as 378 W·h·kg-1 at 68.7 W·kg-1, or 172 W·h·kg-1 at 1705 W·kg-1. The superior electrochemical performance is ascribed to the fast Zn2+ diffusion rate because of a large ratio of capacitive contribution (63.9% at 0.9 mV·s-1). Thus, the mixed phase route provides a novel strategy to enhance electrochemical performance, enabling mixed phase NMO as very promising material towards large-scale energy-storage applications.
    Calcium sulfate whisker prepared by flue gas desulfurization gypsum: A physical-chemical coupling production process
    Jing Gao, Qiang Li, Fuli Liu
    2020, 28(8):  2221-2226.  doi:10.1016/j.cjche.2020.05.021
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    In this paper, the solid waste desulfurization gypsum produced by coal-fired power plants was used as a raw material to prepare calcium sulfate whiskers with high application prospects. Calcium sulfate whiskers with uniform morphology and high aspect ratio can be prepared by hydrothermal method in sulfuric acid solution. A new process of desulfurization gypsum activated by high-energy grinding to reduce the reaction temperature and sulfuric acid concentration was developed. Through the comparison of product morphology, the best grinding time was determined to be 3.5 h. The mechanism of desulfurization gypsum through physical-chemical coupling to reduce energy consumption was clarified. The activation of desulfurization gypsum by grinding and the acidic environment provided by the sulfuric acid solution made the calcium sulfate solution reached rapid saturation and accelerated the nucleation rate. By calculating the conversion and crystallization rate of calcium sulfate whiskers, it was found that there were obvious “autocatalytic” kinetic characteristics during the crystallization process.