Co-reporter:Yuannan Xiong;Wenqi Chen
Research on Chemical Intermediates 2017 Volume 43( Issue 3) pp:1557-1574
Publication Date(Web):2017 March
DOI:10.1007/s11164-016-2715-4
The liquid phase acylation of 2-methylfuran with acetic anhydride over modified Hβ zeolite was first conducted in a continuous flow reactor. The deactivation of Hβ zeolites was attributed to strong adsorption of reactants or products and was verified by GC–MS and 13C MAS NMR. Deactivated zeolites can be regenerated to their original state by calcination. The acidic properties was adjusted by surface modification on Hβ, the maximum yield of 89.5 mol% and selectivity of 100 % were obtained over tartaric acid modified by Hβ. The deposition of tetraethoxysilane to silica on Hβ contributed to enhancing the catalytic stability. Combined with the results of NH3-TPD and Py-FTIR, the amount of Broensted acids played a major role on catalytic activity. A close relationship between the catalytic stability and the ratio of the amount of strong to weak acids at 1:1 was highlighted here. The solvents' effect on the catalytic performances was examined, and 1,2-dichloroethane with moderate polarity exerted a positive effect on catalytic stability.
Co-reporter:Aiwu Zeng;Wenqi Chen;Jianjun Ma;Jiang Yu
Transactions of Tianjin University 2017 Volume 23( Issue 1) pp:26-34
Publication Date(Web):2017 January
DOI:10.1007/s12209-016-0024-z
The selection and design of an optimal solvent for extractive distillation require reliable vapour–liquid phase equilibrium data and knowledge of extraction mechanisms. Compared with time-consuming experiments, molecular simulation presents great potential in research on the properties of fluids. Therefore, in this work, Gibbs ensemble Monte Carlo was applied to successfully predict the vapour–liquid phase equilibrium data of binary and ternary systems containing benzene, thiophene and N, N-dimethylformamide (DMF) at P = 101.3 kPa. The explicit hydrogen version of the transferable potentials for phase equilibria potential model was chosen for benzene and thiophene, whereas the OPLS potential model was selected for DMF. The predicted phase diagrams were compared with experimental data and the UNIQUAC thermodynamic model. A good agreement was obtained, which corroborated the validity of the potential models. In addition, the extraction mechanism was explored by radial distribution function (RDF) of the liquid-phase structure. The RDFs showed that thiophene and benzene shared a similar liquid-phase structure because of the intermolecular interaction. The distinct difference between the RDFs of DMF/benzene and those of DMF/thiophene is that the oxygen atom of DMF is more associated with hydrogen atoms of thiophene than that of benzene, which may be responsible for the extraction effect of DMF.
Co-reporter:Qingjun Zhang, Meiling Liu, Chenxiaodong Li, Aiwu Zeng
Separation and Purification Technology 2017 Volume 189(Volume 189) pp:
Publication Date(Web):22 December 2017
DOI:10.1016/j.seppur.2017.08.016
•The three evaluation indicators are employed to rank the different configurations.•The temperature enthalpy diagram is used to compare the degree of the energy reused.•The control scheme is explored to eliminate the snowball effect for partial PSD case.Design and control of the forward integration of pressure-swing distillation processes is explored with the aid of the tools of Aspen plus and Aspen dynamics taking the separation of the minimum-boiling azeotrope ethyl acetate and ethanol as an example. The optimized separation configuration is obtained by taking the minimization of total annual cost (TAC) as an objective function. The two key performance indicators of second law efficiency (η) and carbon dioxide emissions are employed to evaluate the three operations, which consist of conventional non-heat integration and the corresponding partially and fully heat integration processes. Compared to the non-heat integration process, the fully heat integration process is more attractive since it can achieve 33.33% energy consumption saving, reduction of 31.33% CO2 emissions and 26.64% TAC. Furthermore, the control of the PSD processes with heat integration are explored since the interaction of parameters are complicated for this neat configuration. The effectiveness of the single-end control strategy is evaluated and determined by method of the feed composition sensitive analysis, and a series of control structures are devised and assessed by the perturbations of the feed flow rate and feed composition. It is concluded that the small disturbances are addressed for fully heat integration in comparison with the partially heat integration owing to the degree of freedom reduction. In addition, the efficient control strategy with the ratio scheme to manipulate the cascade flow controller is developed to eliminate the snowball effect for PSD with partially case.(a) The temperature-enthalpy diagram of partially heat integrated PSD process. (b) The temperature-enthalpy diagram of fully heat integrated PSD process.Download high-res image (168KB)Download full-size image
Co-reporter:Qi Zhang, Wenqi Chen, Aiwu Zeng
Journal of Molecular Liquids 2017 Volume 230(Volume 230) pp:
Publication Date(Web):1 March 2017
DOI:10.1016/j.molliq.2016.12.113
•An extensional TraPPE-UA force field for NMP is presented.•Vapor–liquid equilibria of NMP are accurately predicted by the new force field.•Phase equilibria of benzene + NMP, thiophene + NMP, benzene + NMP + thiophene are calculated by GEMC method.•The structural properties of benzene + thiophene + NMP ternary liquid mixture are studied.An extension of the transferable potentials for phase equilibria united-atom (TraPPE-UA) force field to N-Methyl-2-pyrrolidone (NMP) is proposed in this work. The extensional force field can accurately predict the saturated liquid densities, vapor pressures, normal boiling point, heats of vaporization and critical properties of NMP. Gibbs ensemble Monte Carlo (GEMC) simulations are carried out to calculate the isobaric vapor–liquid equilibria for the binary mixtures of benzene + NMP, thiophene + NMP and their ternary mixture at 101.3 kPa. All of these simulation results are in good accordance with the available experimental data without introducing additional binary interaction parameters. In order to study the mechanism of extracting thiophene from benzene by NMP, NPT Monte Carlo simulations are performed to have obtained the radial distribution functions for the ternary liquid mixture benzene + thiophene + NMP. The results show that the oxygen atom of NMP forms stronger hydrogen bond with the hydrogen atom of thiophene than with that of benzene.
Co-reporter:Yuannan Xiong, Wenqi Chen, Jianjun Ma, Zhihua Chen and Aiwu Zeng
RSC Advances 2015 vol. 5(Issue 125) pp:103695-103702
Publication Date(Web):27 Nov 2015
DOI:10.1039/C5RA16139H
The continuous liquid-phase Friedel–Crafts acylation of furan with acetic anhydride was first carried out in a fixed-bed reactor over an H-beta zeolite. A three-level, four-variable Box-Behnken design combined with response surface methodology was employed to determine the optimal acylation conditions, and the accuracy of the model was verified by validation experiments. In this study, it was found that lower liquid velocity and stronger polarity of the solvent were conducive to enhancing the catalytic activity and stability of the H-beta zeolite. The reaction was limited by the acid sites being poisoned due to the adsorption of the by-product and pore blockage. Moreover, the carbon deposit was proved to be the main reason for the deactivation of the H-beta zeolite by using GC-MS, 13C NMR MAS, 27Al NMR MAS, TG/DTG and NH3-TPD.
Co-reporter:Jiang Yu;Lijun Chen;Xigang Yuan;Ji Ju
Chemical Engineering & Technology 2015 Volume 38( Issue 1) pp:173-180
Publication Date(Web):
DOI:10.1002/ceat.201400279
Abstract
Numerical simulation was carried out for a centrifugal short-path distillation arrangement using the computational fluid dynamics technology. Both two phases and interfacial transport were taken into account with an attempt to explore the heat and mass transport in the film body and the interface. The model tried to provide a general method to study the short-path distillation in various situations. The effects of feed flow rates, feed and heating wall temperature controlling the development of the temperature and concentration along the axial and radial direction were investigated. On the basis of the simulation results, detailed characteristics such as distribution of temperature and concentration, heat and mass transfer coefficient throughout the liquid film can be described.
Co-reporter:Jiang Yu;Xigang Yuan;Xinyu Zhang ;Ji Ju
Chemical Engineering & Technology 2015 Volume 38( Issue 10) pp:1865-1872
Publication Date(Web):
DOI:10.1002/ceat.201500022
Abstract
Laminar wave dynamics and the associated heat transfer across the spinning film is a highly important process in chemical engineering, but there is still a lack of sufficient investigation of the transfer flux based on the fundamental hydrodynamics parameters. A two-dimensional computational fluid dynamics simulation of the spinning film on a centrifugal molecular distillator is performed in order to explore the effect of the interfacial wave behavior on the heat transfer. Numerical results reveal that the heat transfer is enhanced by the convective motions in the waves. Resulting from these findings, the relationship between the operation parameters and heat transfer is also discussed.
Co-reporter:Zhihua Chen, Wenqi Chen, Tianxia Tong, Aiwu Zeng
Journal of Molecular Catalysis A: Chemical 2015 Volume 396() pp:231-238
Publication Date(Web):January 2015
DOI:10.1016/j.molcata.2014.09.038
Co-reporter:L.-J. Chen;H.-B. Dong;Q. Li;C.-C. Niu ;A.-W. Zeng
Chemical Engineering & Technology 2013 Volume 36( Issue 5) pp:851-862
Publication Date(Web):
DOI:10.1002/ceat.201200091
Abstract
To simulate the centrifugal short-path distillation process, both two phases and interfacial transport are taken into account simultaneously for the first time. A new computational fluid dynamics model based on the volume-of-fluid and species transport methods is built up to analyze the detailed flow and transfer characteristics. A binary system with dibutyl phthalate-dibutyl sebacate (DBP-DBS) is used as an example for the investigation with both numerical and experimental methods. The residence time and the effects of operating parameters such as evaporator temperature and feed flow rate are explored comparatively. The simulation result for the liquid-film thickness shows a satisfactory agreement with literature data. On the basis of the simulation results, we may also obtain detailed characteristics of the heat and mass transfer such as gradients in temperature and concentration and the liquid overall mass transfer coefficient.
Co-reporter:Jin-Peng Wang;Ai-Wu Zeng;Zhen Liu;Xi-Gang Yuan
Journal of Chemical Technology and Biotechnology 2006 Volume 81(Issue 4) pp:727-729
Publication Date(Web):10 JAN 2006
DOI:10.1002/jctb.1435
Corn starch was hydrolysed by glucoamylase (EC 3.2.1.3, 1,4-a-D-glucan glucohydrolase) in a chemostat; 106 g L−1 reducing sugar was produced at 40 °C after 46 h, whereas only 42 g L−1 was produced at 30 °C. When corn starch concentration was increased from 64.6 g L−1 to 161.5 g L−1, the amount of reducing sugar produced increased with the initial substrate concentration. The studies show that there is a product concentration (p0) above which product inhibition becomes apparent. A new model for starch hydrolysis considering the product inhibition point is presented. Copyright © 2006 Society of Chemical Industry
Co-reporter:Jiang Yu, Xigang Yuan, Aiwu Zeng
Chinese Journal of Chemical Engineering (March 2015) Volume 23(Issue 3) pp:499-504
Publication Date(Web):1 March 2015
DOI:10.1016/j.cjche.2014.10.019
A novel purification process is involved to obtain the high purity [> 99%(by mass)] dodecanedioic acid (DC12). It involves a re-crystallization followed by molecular distillation from the crude product. The objective of this study is to investigate general conditions, feed rate, distilling temperature and vacuum, necessary for centrifugal distillation of DC12. Under the optimum conditions, distilling temperature 180 °C, pressure 30 Pa and feed flow rate 700 ml·h− 1, the purity of DC12 in the residence reached 97.55% with a yield of 53.18% by the analysis of gas chromatography. Multiple-pass distillation made a considerable contribution by improving the purity to 99.22%. Additionally, the effect of pretreatment (re-crystallization) on distillation process was revealed through a series of comparative experiments.This figure is the scheme of a laboratory centrifugal short-path distillation unit Lab3 of Myers company, USA. The main part of the still consists of a conical evaporating rotator, vacuum equipment as well as feed, distillate and residue receivers. The rotator is enclosed in a glass bell jar providing a condensing surface. Evaporating rotator is heated by electric power with a controller inside to maintain a constant evaporating surface temperature. The material is heated and melted to a homogeneous mixture liquid before being pumped to the feed reservoir. When the system is stable (with static pressure and temperature), the mixture is fed to the center of evaporator after degassing. Once on the hot spinning surface, a thin film forms where the lower molecular weight materials evaporate.Download full-size image
Co-reporter:Y.B. Zuo, A.W. Zeng, X.G. Yuan, K.T. Yu
Journal of Food Engineering (December 2008) Volume 89(Issue 4) pp:384-389
Publication Date(Web):1 December 2008
DOI:10.1016/j.jfoodeng.2008.05.004
The effects of modifier composition in terms of methanol content in water, modifier concentration, meal particle size and extraction conditions (temperature, pressure and CO2 flow rate) on isoflavones recovery from soybean meal by supercritical carbon dioxide (SC–CO2) extraction were investigated. The highest isoflavones recovery attained was 87.3%, at 40 °C and 50 MPa, using CO2 flow rate of 9.80 kg/h containing a modifier 7.8 mass% of 80% (v/v) aqueous methanol. Using different modifier concentrations (60–100% methanol) at 50 MPa and 40 °C, it was shown that 80% methanol was optimum for isoflavones extraction. In addition, isoflavones recovery increased with the modifier content in SC–CO2 up to 10.2%. The optimal particle size was 20–30 mesh with bigger and smaller particles resulting in lower isoflavones recovery. The results showed that increasing the temperature from 40 to 70 °C drastically reduced isoflavones recovery at 50 MPa. The higher the extraction pressure, the higher was the isoflavones recovery. The extraction rate increased with CO2 flow rate but the percentage recovery was more or less the same.
