Frontiers of Chemical Science and Engineering

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Recovery of waste heat in cement plants for the capture of CO2
Ruifeng DONG, Zaoxiao ZHANG, Hongfang LU, Yunsong YU
Front Chem Sci Eng.  2012, 6 (1): 104-111.
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Large amounts of energy are consumed during the manufacturing of cement especially during the calcination process which also emits large amounts of CO2. A large part of the energy used in the making of cement is released as waste heat. A process to capture CO2 by integrating the recovery and utilization of waste heat has been designed. Aspen Plus software was used to calculate the amount of waste heat and the efficiency of energy utilization. The data used in this study was based on a dry process cement plant with a 5-stage preheater and a precalciner with a cement output of 1 Mt/y. According to the calculations: 1) the generating capacity of the waste heat recovery system is 4.9 MW. 2) The overall CO2 removal rate was as high as 78.5%. 3) The efficiency of energy utilization increased after the cement producing process was retrofitted with this integrated design.

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Hierarchically porous materials: Synthesis strategies and emerging applications
Minghui Sun, Chen Chen, Lihua Chen, Baolian Su
Front. Chem. Sci. Eng..  2016, 10 (3): 301-347.
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Great interests have arisen over the last decade in the development of hierarchically porous materials. The hierarchical structure enables materials to have maximum structural functions owing to enhanced accessibility and mass transport properties, leading to improved performances in various applications. Hierarchical porous materials are in high demand for applications in catalysis, adsorption, separation, energy and biochemistry. In the present review, recent advances in synthesis routes to hierarchically porous materials are reviewed together with their catalytic contributions.

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Mechanistic understanding of Cu-based bimetallic catalysts
You Han, Yulian Wang, Tengzhou Ma, Wei Li, Jinli Zhang, Minhua Zhang
Front. Chem. Sci. Eng..  2020, 14 (5): 689-748.
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Copper has received extensive attention in the field of catalysis due to its rich natural reserves, low cost, and superior catalytic performance. Herein, we reviewed two modification mechanisms of co-catalyst on the coordination environment change of Cu-based catalysts: (1) change the electronic orbitals and geometric structure of Cu without any catalytic functions; (2) act as an additional active site with a certain catalytic function, as well as their catalytic mechanism in major reactions, including the hydrogenation to alcohols, dehydrogenation of alcohols, water gas shift reaction, reduction of nitrogenous compounds, electrocatalysis and others. The influencing mechanisms of different types of auxiliary metals on the structure-activity relationship of Cu-based catalysts in these reactions were especially summarized and discussed. The mechanistic understanding can provide significant guidance for the design and controllable synthesis of novel Cu-based catalysts used in many industrial reactions.

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Measurement and correlation of the solid-liquid equilibrium of 2-(tert-buty)-5-methylphenol and 2-(tert-buty)-4-methylphenol binary system
Yanhong SUN, Zhiyong LI, Chuang XIE, Wei CHEN, Cui ZHANG
Front Chem Sci Eng.  2013, 7 (1): 110-115.
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In this work, the enthalpy of fusion and melting points of 2-(tert-butyl)-5-methylphenol (2B5MP) and 2-(tert-butyl)-4-methylphenol (2B4MP) were measured by differential scanning calorimetry (DSC). The binary solid-liquid equilibrium (SLE) of both compounds were predicted by integrated computer aided system (ICAS) and measured by DSC. The corresponding eutectic molar composition is 0.6998 and the eutectic temperature is 281.96 K. The quasi-static heat capacities of 2B5MP and 2B4MP were evaluated by stochastic temperature modulation DSC technique (TOPEM). The SLE experimental data were correlated using the Margules, Wilson, and non-random two liquid (NRTL) equations and a good agreement between measurement and calculation could be obtained.

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Synthesis and properties of tetrathiafulvalene-porphyrin assemblies
Meijiang LI, Rui HUANG, Changzhi WU, Hujin ZUO, Guoqiao LAI, Yongjia SHEN
Front Chem Sci Eng.  2011, 5 (4): 422-428.
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Two donor-σ-acceptor molecular systems incorporating tetrathiafulvalene (TTF) and tetraphenylporphyrin (TPP) units, TTF-TPP (dyad 1) and TTF-TPP-TTF (triad 2), were synthesized. Both dyad 1 and triad 2 and their synthetic intermediates have been characterized by 1H nuclear magnetic resonance (1H NMR) and mass spectrography (MS). Their ultraviolet and visible spectroscopy (UV-Vis) and cyclic voltammetry (CV) showed negligible intramolecular charge transfer interaction in their ground states. Their fluorescence intensity was strongly quenched compared with TPP, which implied the photoinduced electron transfer occurred from the TTF unit to the TPP unit in the excited state. On the other hand, their fluorescence intensity could be modulated by sequential oxidation of the TTF unit using chemical methods, which exhibited their potential application in fluorescence molecular switch.

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Current understanding and applications of the cold sintering process
Tong Yu, Jiang Cheng, Lu Li, Benshuang Sun, Xujin Bao, Hongtao Zhang
Front. Chem. Sci. Eng..  2019, 13 (4): 654-664.
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In traditional ceramic processing techniques, high sintering temperature is necessary to achieve fully dense microstructures. But it can cause various problems including warpage, overfiring, element evaporation, and polymorphic transformation. To overcome these drawbacks, a novel processing technique called “cold sintering process (CSP)” has been explored by Randall et al. CSP enables densification of ceramics at ultra-low temperature (≤300°C) with the assistance of transient aqueous solution and applied pressure. In CSP, the processing conditions including aqueous solution, pressure, temperature, and sintering duration play critical roles in the densification and properties of ceramics, which will be reviewed. The review will also include the applications of CSP in solid-state rechargeable batteries. Finally, the perspectives about CSP is proposed.

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Advances in the slurry reactor technology of the anthraquinone process for H2O2 production
Hongbo Li, Bo Zheng, Zhiyong Pan, Baoning Zong, Minghua Qiao
Front. Chem. Sci. Eng..  2018, 12 (1): 124-131.
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This paper overviews the development of the anthraquinone auto-oxidation (AO) process for the production of hydrogen peroxide in China and abroad. The characteristics and differences between the fixed-bed and fluidized-bed reactors for the AO process are presented. The detailed comparison indicates that the production of hydrogen peroxide with the fluidized-bed reactor has many advantages, such as lower operation cost and catalyst consumption, less anthraquinone degradation, higher catalyst utilization efficiency, and higher hydrogenation efficiency. The key characters of the production technology of hydrogen peroxide based on the fluidized-bed reactor developed by the Research Institute of Petroleum Processing, Sinopec are also disclosed. It is apparent that substituting the fluidized-bed reactor for the fixed-bed reactor is a major direction of breakthrough for the production technology of hydrogen peroxide in China.

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A review on emulsification via microfluidic processes
Yichen Liu, Yongli Li, Andreas Hensel, Juergen J. Brandner, Kai Zhang, Xiaoze Du, Yongping Yang
Front. Chem. Sci. Eng..  2020, 14 (3): 350-364.
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Emulsion is a disperse system with two immiscible liquids, which demonstrates wide applications in diverse industries. Emulsification technology has advanced well with the development of microfluidic process. Compared to conventional methods, the microfluidics-based process can produce controllable droplet size and distribution. The droplet formation or breakup is the result of combined effects resulting from interfacial tension, viscous, and inertial forces as well as the forces generated due to hydrodynamic pressure and external stimuli. In the current study, typical microfluidic systems, including microchannel array, T-shape, flow-focusing, co-flowing, and membrane systems, are reviewed and the corresponding mechanisms, flow regimes, and main parameters are compared and summarized.

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Detoxification and concentration of corn stover hydrolysate and its fermentation for ethanol production
Qing Li, Yingjie Qin, Yunfei Liu, Jianjun Liu, Qing Liu, Pingli Li, Liqiang Liu
Front. Chem. Sci. Eng..  2019, 13 (1): 140-151.
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Environmental and energy concerns have increased interest in renewable energy sources, particularly biofuels. Thus the fermentation of glucose from sulfuric acid-hydrolyzed corn stover for the production of bioethanol has been explored using a combined acid retardation and continuous-effect membrane distillation treatment process. This process resulted in the separation of the sugars and acids from the acid-catalyzed hydrolysate, the removal of most of the fermentation inhibitors from the hydrolysate and the concentration of the detoxified hydrolysate. The recovery rate of glucose from the sugar-acid mixture using acid retardation was greater than 99.12% and the sulfuric acid was completely recovered from the hydrolysate. When the treated corn stover hydrolysate, containing 100 g/L glucose, was used as a carbon source, 43.06 g/L of ethanol was produced with a productivity of 1.79 g/(L∙h) and a yield of 86.31%. In the control experiment, where glucose was used as the carbon source these values were 1.97 g/(L∙h) and 93.10% respectively. Thus the integration of acid retardation and a continuous-effect membrane distillation process are effective for the production of fuel ethanol from corn stover.

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Special Topic on environment and sustainable development
Front. Chem. Sci. Eng..  2017, 11 (3): 291-292.
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Erratum to: Multifunctional peptide conjugated amphiphilic cationic copolymer for enhancing ECs targeting, penetrating and nuclear accumulation
Xinghong Duo, Lingchuang Bai, Jun Wang, Jintang Guo, Xiangkui Ren, Shihai Xia, Wencheng Zhang, Abraham Domb, Yakai Feng
Front. Chem. Sci. Eng..  2021, 15 (1): 220-220.
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Extension of pilot tests of cyanide elimination by ozone from blast furnace gas washing water through Aspen Plus® based model
Ismael Matino, Valentina Colla, Teresa A. Branca
Front. Chem. Sci. Eng..  2018, 12 (4): 718-730.
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For improving wastewater quality, one of the dare of steelworks is reducing cyanide in wastewater of gas washing treatment of blast furnaces. Costs of existing treatments, stringent environmental regulations and changeable composition of water from gas treatment, have led to study how available treatments can be modified and to examine new ones. Ozonation is one of cyanide treatments, tested within a European project. A process model was set up with Aspen Plus®, to assess operating conditions and wastewater distinctive characteristics and to demonstrate treatment robustness. Process was modeled by theoretical reactors, taking into account all more affecting reactions. A genetic algorithm was exploited to find kinetic parameters of these reactions. After validation, the model was used to analyse scenarios, by considering also real contexts. Pilot tests were extended, process knowledge was enhanced and suggestions were obtained. To promote cyanide removal with ozone, temperature and pH values were 30°C and 10, respectively. With an ozone (mg/h)/water (L/h) ratio of 100 mg/L, batch mode ensure reaching cyanide regulation limit (0.2 mg/L) after maximum 4.5 h, if initial amount was less than 20 mg/L. Higher removal was obtained than in continuous mode due to constraints related to this last run. Higher wastewater contamination needed further time and more ozone.

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An efficient technique for improving methanol yield using dual CO2 feeds and dry methane reforming
Yang Su, Liping Lü, Weifeng Shen, Shun’an Wei
Front. Chem. Sci. Eng..  2020, 14 (4): 614-628.
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Steam methane reforming (SMR)-based methanol synthesis plants utilizing a single CO2 feed represent one of the predominant technologies for improving methanol yield and CO2 utilization. However, SMR alone cannot achieve full CO2 utilization, and a high water content accumulates if CO2 is only fed into the methanol reactor. In this study, a process integrating SMR with dry methane reforming to improve the conversion of both methane and CO2 is proposed. We also propose an innovative methanol production approach in which captured CO2 is introduced into both the SMR process and the recycle gas of the methanol synthesis loop. This dual CO2 feed approach aims to optimize the stoichiometric ratio of the reactants. Comparative evaluations are carried out from a techno-economic point of view, and the proposed process is demonstrated to be more efficient in terms of both methanol productivity and CO2 utilization than the existing stand-alone natural gas-based methanol process.

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Catalytic process modeling and sensitivity analysis of alkylation of benzene with ethanol over MIL-101(Fe) and MIL-88(Fe)
Ehsan Rahmani, Mohammad Rahmani
Front. Chem. Sci. Eng..  2020, 14 (6): 1100-1111.
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A solvothermal method was used to synthesize MIL-101(Fe) and MIL-88(Fe), which were used for alkylation of benzene. The synthesized catalysts were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscope, dynamic light scattering, and BET techniques. Metal-organic frameworks (MOFs) were modeled to investigate the catalytic performance and existence of mass transfer limitations. Calculated effectiveness factors revealed absence of internal and external mass transfer. Sensitivity analysis revealed best operating conditions over MIL-101 at 120°C and 5 bar and over MIL-88 at 142°C and 9 bar.

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Novel engineered proteins for mechanomaterials
Giuseppe Portale
Front. Chem. Sci. Eng..  2020, 14 (6): 1122-1123.
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Mesoporous zeolites as efficient catalysts for oil refining and natural gas conversion
Jie ZHU, Xiangju MENG, Fengshou XIAO
Front Chem Sci Eng.  2013, 7 (2): 233-248.
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Zeolites have been regarded as one of the most important catalysts in petrochemical industry due to their excellent catalytic performance. However, the sole micropores in zeolites severely limit their applications in oil refining and natural gas conversion. To solve the problem, mesoporous zeolites have been prepared by introducing mesopores into the zeolite crystals in recent years, and thus have the advantages of both mesostructured materials (fast diffusion and accessible for bulky molecules) and microporous zeolite crystals (strong acidity and high hydrothermal stability). In this review, after giving a brief introduction to preparation, structure, and characterization of mesoporous zeolites, we systematically summarize catalytic applications of these mesoporous zeolites as efficient catalysts in oil refining and natural gas conversion including catalytic cracking of heavy oil, alkylation, isomerization, hydrogenation, hydrodesulfurization, methane dehydroaromatization, methanol dehydration to dimethyl ether, methanol to olefins, and methanol to hydrocarbons.

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Immobilization of nano-zero-valent irons by carboxylated cellulose nanocrystals for wastewater remediation
Bangxian Peng, Rusen Zhou, Ying Chen, Song Tu, Yingwu Yin, Liyi Ye
Front. Chem. Sci. Eng..  2020, 14 (6): 1006-1017.
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Nano-zero-valent irons (nZVI) have shown great potential to function as universal and low-cost magnetic adsorbents. Yet, the rapid agglomeration and easy surface corrosion of nZVI in solution greatly hinders their overall applicability. Here, carboxylated cellulose nanocrystals (CCNC), widely available from renewable biomass resources, were prepared and applied for the immobilization of nZVI. In doing so, carboxylated cellulose nanocrystals supporting nano-zero-valent irons (CCNC-nZVI) were obtained via an in-situ growth method. The CCNC-nZVI were characterized and then evaluated for their performances in wastewater treatment. The results obtained show that nZVI nanoparticles could attach to the carboxyl and hydroxyl groups of CCNC, and well disperse on the CCNC surface with a size of ~10 nm. With the CCNC acting as corrosion inhibitors improving the reaction activity of nZVI, CCNC-nZVI exhibited an improved dispersion stability and electron utilization efficacy. The Pb(II) adsorption capacity of CCNC-nZVI reached 509.3 mg·g1 (298.15 K, pH= 4.0), significantly higher than that of CCNC. The adsorption was a spontaneous exothermic process and could be perfectly fitted by the pseudo-second-order kinetics model. This study may provide a novel and green method for immobilizing magnetic nanomaterials by using biomass-based resources to develop effective bio-adsorbents for wastewater decontamination.

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The preparation, characterization, and catalytic performance of porous fibrous LaFeO3 perovskite made from a sunflower seed shell template
Zhifei Wu, Li Wang, Yixiao Hu, Hui Han, Xing Li, Ying Wang
Front. Chem. Sci. Eng..  2020, 14 (6): 967-975.
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LaFeO3 perovskite with a porous fibrous structure was successfully synthesized using a sunflower seed shell as a template. To investigate the effects of this template, a sample was prepared without a template via the same procedure. Through various characterization techniques, such as X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy, oxygen temperature programed desorption, and hydrogen temperature programed reduction, the physiochemical properties of the samples were investigated. The results showed that the sample made with a template had a larger surface area and a larger amount of adsorbed oxygen, which further illustrated that the sunflower seed shell template had a significant impact on the physiochemical properties of the samples. Furthermore, we explored the catalytic activity for nitric oxide (NO) oxidation, and studied the factors affecting it, which highlighted its potential application in automobile exhausts.

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Supramolecular self-assembly of two-component systems comprising aromatic amides/Schiff base and tartaric acid
Xin Wang, Wei Cui, Bin Li, Xiaojie Zhang, Yongxin Zhang, Yaodong Huang
Front. Chem. Sci. Eng..  2020, 14 (6): 1112-1121.
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The gelating properties and thermotropic behaviors of stoichiometric mixtures of aromatic amides 1, 2, and the aromatic Schiff base 3 with tartaric acid (TA) were investigated. Among the three gelators, 2-TA exhibited superior gelating ability. Mixture 2-TA exhibits a smectic B phase and an unidentified smectic mesophase during both heating and cooling runs. The results of Fourier transform infrared spectroscopy and X-ray diffraction revealed the existence of hydrogen bonding and p-p interactions in 2-TA systems, which are likely to be the dominant driving forces for the supramolecular self-assembly. Additionally, it was established that all of the studied gel self-assemblies and mesophases possess a lamellar structure. The anion response ability of the tetrahydrofuran gel of 2-TA was evaluated and it was found that it was responsive to the stimuli of F, Cl, Br, I, AcO.

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Efficient elimination of environmental pollutants through sorption-reduction and photocatalytic degradation using nanomaterials
Njud S. Alharbi, Baowei Hu, Tasawar Hayat, Samar Omar Rabah, Ahmed Alsaedi, Li Zhuang, Xiangke Wang
Front. Chem. Sci. Eng..  2020, 14 (6): 1124-1135.
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With the rapid development of industrial, large amounts of different inorganic and organic pollutants are released into the natural environments. The efficient elimination of environmental pollutants, i.e., photocatalytic degradation of persistent organic pollutants into nontoxic organic/inorganic chemicals, in-situ solidification or sorption-reduction of heavy metal ions, is crucial to protect the environment. Nanomaterials with large surface area, active sites and abundant functional groups could form strong surface complexes with different kinds of pollutants and thereby could efficiently eliminate the pollutants from the aqueous solutions. In this review, we mainly focused on the recent works about the synthesis of nanomaterials and their applications in the efficient elimination of different organic and inorganic pollutants from wastewater and discussed the interaction mechanism from batch experimental results, the advanced spectroscopy techniques and theoretical calculations. The adsorption and the photocatalytic reduction of organic pollutants and the sorption/reduction of heavy metal ions are generally considered as the main methods to decrease the concentration of pollutants in the natural environment. This review highlights a new way for the real applications of novel nanomaterials in environmental pollution management, especially for the undergraduate students to understand the recent works in the elimination of different kinds of inorganic and organic chemicals in the natural environmental pollution management.

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Cationic and amphipathic cell-penetrating peptides (CPPs): Their structures and in vivo studies in drug delivery
Jennica L. Zaro,Wei-Chiang Shen
Front. Chem. Sci. Eng..  2015, 9 (4): 407-427.
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Over the past few decades, cell penetrating peptides (CPPs) have become an important class of drug carriers for small molecules, proteins, genes and nanoparticle systems. CPPs represent a very diverse set of short peptide sequences (10?30 amino acids), generally classified as cationic or amphipathic, with various mechanisms in cellular internalization. In this review, a more comprehensive assessment of the chemical structural characteristics, including net cationic charge, hydrophobicity and helicity was assembled for a large set of commonly used CPPs, and compared to results from numerous in vivo drug delivery studies. This detailed information can aid in the design and selection of effective CPPs for use as transport carriers in the delivery of different types of drug for therapeutic applications.

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Charge-carrier photogeneration and extraction dynamics of polymer solar cells probed by a transient photocurrent nearby the regime of the space charge-limited current
Boa Jin, Hyunmin Park, Yang Liu, Leijing Liu, Jongdeok An, Wenjing Tian, Chan Im
Front. Chem. Sci. Eng..  2021, 15 (1): 164-179.
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To understand the complex behaviors of photogenerated charge carriers within polymer-based bulk-heterojunction-type solar cells, the charge-carrier photogeneration and extraction dynamics are simultaneously estimated using a transient photocurrent technique under various external-bias voltages, and a wide range of excitation intensities are analyzed. For this purpose, conventional devices with 80 nm thick active layers consisting of a blend of representative P3HT and PTB7 electron-donating polymers and proper electron-accepting fullerene derivatives were used. After the correction for the saturation behavior at a high excitation-intensity range nearby the regime of the space charge-limited current, the incident-photon-density-dependent maximum photocurrent densities at the initial peaks are discussed as the proportional measures of the charge-carrier-photogeneration facility. By comparing the total number of the extracted charge carriers to the total number of the incident photons and the number of the initially photogenerated charge carriers, the external quantum efficiencies as well as the extraction quantum efficiencies of the charge-carrier collection during a laser-pulse-induced transient photocurrent process were obtained. Subsequently, the charge-carrier concentration-dependent mobility values were obtained, and they are discussed in consideration of the additional influences of the charge-carrier losses from the device during the charge-carrier extraction that also affects the photocurrent-trace shape.

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Progress in membrane distillation crystallization: Process models, crystallization control and innovative applications
Xiaobin Jiang, Linghan Tuo, Dapeng Lu, Baohong Hou, Wei Chen, Gaohong He
Front. Chem. Sci. Eng..  2017, 11 (4): 647-662.
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Membrane distillation crystallization (MDC) is a promising hybrid separation process that has been applied to seawater desalination, brine treatment and wastewater recovery. In recent years, great progress has been made in MDC technologies including the promotion of nucleation and better control of crystallization and crystal size distribution. These advances are useful for the accurate control of the degree of supersaturation and for the control of the nucleation kinetic processes. This review focuses on the development of MDC process models and on crystallization control strategies. In addition, the most important innovative applications of MDC in the last five years in crystal engineering and pharmaceutical manufacturing are summarized.

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Optimal design of extractive dividing-wall column using an efficient equation-oriented approach
Yingjie Ma, Nan Zhang, Jie Li, Cuiwen Cao
Front. Chem. Sci. Eng..  2021, 15 (1): 72-89.
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The extractive dividing-wall column (EDWC) is one of the most efficient technologies for separation of azeotropic or close boiling-point mixtures, but its design is fairly challenging. In this paper we extend the hybrid feasible path optimisation algorithm (Ma Y, McLaughlan M, Zhang N, Li J. Computers & Chemical Engineering, 2020, 143: 107058) for such optimal design. The tolerances-relaxation integration method is refined to allow for long enough integration time that can ensure the solution of the pseudo-transient continuation simulation close to the steady state before the required tolerance is used. To ensure the gradient and Jacobian information available for optimisation, we allow a relaxed tolerance for the simulation in the sensitivity analysis mode when the simulation diverges under small tolerance. In addition, valid lower bounds on purity of the recycled entrainer and the vapour flow rate in column sections are imposed to improve computational efficiency. The computational results demonstrate that the extended hybrid algorithm can achieve better design of the EDWC compared to those in literature. The energy consumption can be reduced by more than 20% compared with existing literature report. In addition, the optimal design of the heat pump assisted EDWC is achieved using the improved hybrid algorithm for the first time.

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Overcoming oral insulin delivery barriers: application of cell penetrating peptide and silica-based nanoporous composites
Huining HE, Junxiao YE, Jianyong SHENG, Jianxin WANG, Yongzhuo HUANG, Guanyi CHEN, Jingkang WANG, Victor C YANG
Front Chem Sci Eng.  2013, 7 (1): 9-19.
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Oral insulin delivery has received the most attention in insulin formulations due to its high patient compliance and, more importantly, to its potential to mimic the physiologic insulin secretion seen in non-diabetic individuals. However, oral insulin delivery has two major limitations: the enzymatic barrier that leads to rapid insulin degradation, and the mucosal barrier that limits insulin’s bioavailability. Several approaches have been actively pursued to circumvent the enzyme barrier, with some of them receiving promising results. Yet, thus far there has been no major success in overcoming the mucosal barrier, which is the main cause in undercutting insulin’s oral bioavailability. In this review of our group’s research, an innovative silica-based, mucoadhesive oral insulin formulation with encapsulated-insulin/cell penetrating peptide (CPP) to overcome both enzyme and mucosal barriers is discussed, and the preliminary and convincing results to confirm the plausibility of this oral insulin delivery system are reviewed. In vitro studies demonstrated that the CPP-insulin conjugates could facilitate cellular uptake of insulin while keeping insulin’s biologic functions intact. It was also confirmed that low molecular weight protamine (LMWP) behaves like a CPP peptide, with a cell translocation potency equivalent to that of the widely studied TAT. The mucoadhesive properties of the produced silica-chitosan composites could be controlled by varying both the pH and composition; the composite consisting of chitosan (25 wt-%) and silica (75 wt-%) exhibited the greatest mucoadhesion at gastric pH. Furthermore, drug release from the composite network could also be regulated by altering the chitosan content. Overall, the universal applicability of those technologies could lead to development of a generic platform for oral delivery of many other bioactive compounds, especially for peptide or protein drugs which inevitably encounter the poor bioavailability issues.

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Problems, potentials and future of industrial crystallization
J. Ulrich, P. Frohberg
Front Chem Sci Eng.  2013, 7 (1): 1-8.
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This review discusses important research developments and arising challenges in the field of industrial crystallization with an emphasis on recent problems. The most relevant areas of research have been identified. These are the prediction of phase diagrams; the prediction of effects of impurities and additives; the design of fluid dynamics; the process control with process analytical technologies (PAT) tools; the polymorph and solvate screening; the stabilization of non-stable phases; and the product design. The potential of industrial crystallization in various areas is outlined and discussed with particular reference to the product quality, process design, and control. On this basis, possible future directions for research and development have been pointed out to highlight the importance of crystallization as an outstanding technique for separation, purification as well as for product design.

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Carbon-coated lithium titanate: effect of carbon precursor addition processes on the electrochemical performance
Shilei Ding, Zelong Jiang, Jing Gu, Hongliang Zhang, Jiajia Cai, Dongdong Wang
Front. Chem. Sci. Eng..  2021, 15 (1): 148-155.
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In this paper, two carbon-coated lithium titanate (LTO-C1 and LTO-C2) composites were synthesized using the ball-milling-assisted calcination method with different carbon precursor addition processes. The physical and electrochemical properties of the as-synthesized negative electrode materials were characterized to investigate the effects of two carbon-coated LTO synthesis processes on the electrochemical performance of LTO. The results show that the LTO-C2 synthesized by using Li2CO3 and TiO2 as the raw materials and sucrose as the carbon source in a one-pot method has less polarization during lithium insertion and extraction, minimal charge transfer impedance value and the best electrochemical performance among all samples. At the current density of 300 mA·h·g–1, the LTO-C2 composite delivers a charge capacity of 126.9 mA·h·g–1, and the reversible capacity after 300 cycles exceeds 121.3 mA·h·g–1 in the voltage range of 1.0–3.0 V. Furthermore, the electrochemical impedance spectra show that LTO-C2 has higher electronic conductivity and lithium diffusion coefficient, which indicates the advantages in electrode kinetics over LTO and LTO-C1. The results clarify the best electrochemical properties of the carbon-coated LTO-C2 composite prepared by the one-pot method.

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Cell surface protein engineering for high-performance whole-cell catalysts
Hajime Nakatani,Katsutoshi Hori
Front. Chem. Sci. Eng..  2017, 11 (1): 46-57.
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Cell surface protein engineering facilitated by accumulation of information on genome and protein structure involves heterologous production and modification of cell surface proteins using genetic engineering, and is important for the development of high-performance whole-cell catalysts. In this field, cell surface display is a major technology by exposing target proteins, such as enzymes, on the cell surface using a carrier protein. The target proteins are fused to the carrier proteins that transport and tether them to the cell surface, as well as to a secretion signal. This paper reviews cell surface display systems for prokaryotic and eukaryotic cells from the perspective of carrier proteins, which determine the number of displayed molecules, and the localization, size, and direction (N- or C-terminal anchoring) of the passengers. We also discuss advanced methods for displaying multiple enzymes and a new method for the immobilization of whole-cell catalysts using adhesive surface proteins.

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