Experimental and simulation of the reactive dividing wall column based on ethyl acetate synthesis

Reactive dividing wall column(RDWC) is a highly integrated unit which combines reaction distillation(RD) with dividing wall column separation technology into one shell, and it realized the chemical reaction and the separation of multiple product fractions simultaneously. In this paper, the reaction of esterification with acetic acid and ethanol to produce ethyl acetate was used as the research system, experiments and simulations of the RDWC were carried out. This system in the traditional process mostly used the homogeneous catalyst(e.g. sulfuric acid). However, in view of the corrosion of the equipment caused by the acidity of the catalyst, we used the heterogeneous catalysts – iron exchange resins – Amberlyst15 and proposed a novel catalyst loading method. Firstly,the reliability of the model of the simulation was verified by the experimental study on the change of liquid split ratio and reflux ratio. After that, the four-column model was established in Aspen Plus to analyze the effects of the amount of azeotropic agent, reflux ratio and acetic acid concentration. Finally, for a fair comparison, the economic analysis was conducted between traditional RD column and RDWC. The results showed that RDWC can save34.7% of total operating costs and 18.5% of TAC.     

Vapor permeation of ethyl acetate,propyl acetate,and butyl acetate with hydrophobic inorganic membrane

This study is focused on the permeation characteristics of ester compounds from aqueous solutions through hydrophobic membrane; ethyl acetate (EA), propyl acetate (PA) and butyl acetate (BA). A surface-modified tube-type alumina membrane (Al₂O₃) was used for ester compounds recovery by vapor permeation. Experiments were performed to evaluate the effects of the feed concentration (0.15–0.60 wt.%) and feed temperature (30–50 °C) on the separation of EA, PA, and BA from dilute aqueous solutions. It was found that the permeation flux increased with increasing feed ester concentration and operating temperature. The fluxes of EA, PA, and BA at 0.60 wt.% feed concentration and 40 °C were 282, 526, 661 g/m² h, which were much higher than those of polymer membranes. The separation factors for the 0.15–0.60 wt.% feed solution of EA, PA, and BA at 40 °C were in the range of 28.1–93.9, 83.6–129.4, and 190.7–209.9, respectively. The membrane tested showed high flux and high selectivity.     

隔板塔共沸精馏分离二氯甲烷-乙腈-水-硅醚体系

以二氯甲烷-乙腈-水-硅醚为分离体系,采用自制隔板塔小试装置,研究了共沸剂回流比和液相分配比等操作参数对隔板塔分离效果的影响。实验结果表明,当气相分配比R_v为0.5,共沸剂回流比为3时,液相分配比R_l在[0.12,0.2]范围内,隔板塔分离效果较好。在实验的基础上,采用Aspen Plus软件对隔板塔共沸精馏工艺进行模拟,考察了隔板塔共沸精馏工艺最佳操作区域及节能效果。模拟结果表明,特定分离要求下,隔板塔存在一个使再沸器热负荷最小的最佳操作区域,在此最佳操作区域内,R_l和R_v相互关联,呈一一对应关系;与三塔串联简单精馏工艺相比,完成相同的分离任务,隔板塔共沸精馏工艺再沸器节能32.74%,冷凝器热负荷减少33.70%,乙腈回收率由66.47%提高到96.01%,且大幅降低设备投资。     

Reactive dividing wall column for hydrolysis of methyl acetate:Design and control☆

Reactive distillation and dividing wall column distillation are two kinds of effective separation technologies, and their integrated configuration, reactive dividing wall column (RDWC), presents attractive advantages. In this study, the rigorous simulation of RDWC for methyl acetate hydrolysis is performed, and sensitivity analysis is conducted to obtain the minimum reboiler duty. Then a comparison is made between the conventional process and RDWC process, and it shows that 20.1%energy savings can be achieved by RDWC process. In addition, the dynamic characteristic of RDWC is studied and an effective control strategy is proposed. The simple PI control scheme with three temperature loops can obtain reasonable control performance and maintain products at de-sired purities. It is proved that this RDWC process is an energy efficiency alternative with good controllability. ? 2016 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. Al rights reserved.     

Comparison of continuous homogenous azeotropic and pressure-swing distillation for a minimum azeotropic system ethyl acetate/n-hexane separation

Continuous homogenous azeotropic distillation (CHAD) and pressure-swing distillation (PSD) are explored to separate a minimum-boiling azeotropic system of ethyl acetate and n-hexane. The CHAD process with acetone as the entrainer and the PSD process with the pressures of 0.1 MPa and 0.6 MPa in two columns are designed and simulated by Aspen Plus. The operating conditions of the two processes are optimized via a sequential modular approach to obtain the minimum total annual cost (TAC). The computational results show that the partially heat integrated pressure-swing distillation (HIPSD) has reduced in the energy cost and TAC by 40.79% and 35.94%, respectively, than the conventional PSD, and has more greatly reduced the energy cost and TAC by 62.61% and 49.26% respectively compared with the CHAD process. The comparison of CHAD process and partially HIPSD process illustrates that the partially HIPSD has more advantages in averting the product pollution, energy saving, and economy.     

Self-assembly of C60 containing poly(methyl methacrylate) in ethyl acetate/decalin mixtures solvent

[60]Fullerene (C₆₀) was mono-substituted with well-defined poly(methyl methacrylate) (PMMA-b-C₆₀) using the atom transfer radical polymerization (ATRP) technique. The self-assembly behaviors of PMMA-b-C₆₀ in ethyl acetate (EA) and decalin mixtures were studied using laser light scattering (LLS) and transmission electron microscopy (TEM). Homogeneous solutions of PMMA-b-C₆₀ can be obtained in the solvent mixtures containing more than 40 wt% EA, where the molar ratio of decalin to EA is close to 1. For each solvent mixture, unimers coexist with micelles and large aggregates. The sizes of PMMA-b-C₆₀ micelles and aggregates are independent of polymer concentration, confirming that they are produced via the closed association mechanism. For the various solvent mixtures, the weight-averaged molecular weights, M_w of the PMMA-b-C₆₀ aggregates range from 4.1×10⁷ to 12.5×10⁷ g/mol. The hydrodynamic radii of the large aggregate, R_h, vary from 90 to 136 nm, while the z-averaged radii of gyration, R_g, range from 210 to 311 nm. The R_g/R_h value for each solvent mixture is ∼2.3, which is independent of decalin contents in the mixed solvents. The morphological study using the transmission electron microscope suggests that the large aggregates are composed of porous large compound micelles (LCM) in solution.     

Design and control of extractive distillation for the separation of methyl acetate-methanol-water

The azeotrope of methyl acetate methanol and water was isolated using extractive distillation with water as entrainer. The pressure-swing extractive distillation (PSED) process and vapor side-stream distillation column (VSDC) with the rectifier process were designed to separate the methyl acetate, methanol and water mixture. It was revealed that the VSDC with the rectifier process had a reduction in energy consumption than the PSED process. Four control schemes of the two process were investigated: Double temperature control scheme (CS1), Q_R/F feedforward control of reboiler duty scheme for PESD (CS2), Q_R/F feedback control scheme for VSDC (CS3), the feedback control scheme of sensitive plate temperature of side-drawing distillation column to dominate the compressor shaft speed (CS4). Feed flow and composition disturbance were used to evaluate the dynamic performance. As a result, CS4 is a preferable choice for separation of methyl acetate-methanol-water mixture. A control scheme combining the operating parameters of dynamic equipment with the control indicators of static equipment was proposed in this paper. It means using the sensitive plate temperature of side-drawing column to control the compressor shaft speed. This is a new control scheme for extractive distillation.     

化学吸收法回收低浓度CO_2工艺流程改进与模拟

现有MEA法回收烟气中的CO2工艺存在能耗较高的情况。本研究开展了CO2脱除工艺的节能研究。通过在吸收塔中添加一股循环物流,对工艺流程做了改进。采用商业软件Pro/Ⅱ,在全流程模拟的基础上采用不同再沸器热负荷操作条件,对改进前后的工艺进行了模拟研究,并对模拟结果进行了分析。结果表明:改进后烟气脱碳工艺流程,在较低的再沸器热负荷条件下,提高了CO2的脱除率,收率提高5.0%～14.3%,提高了CO2产量。在对收率要求不高条件下,再沸器热负荷降低7.5%～8.1%,节省了高压蒸汽,节能降耗效果明显。     

Dynamically formed polyelectrolyte membranes on partially cured cellulose acetate

The mechanism of dynamic formation of polyelectrolyte membranes was investigated. Quaternized 2-polyvinylpyridine (2-PVP) and polyvinylamine hydrochloride (PVA) were deposited on partially cured asymmetric cellulose acetate (CA) membranes. The average pore size distribution in (CA) membranes was controlled by changing their annealing temperature within the range of 70 to 77°C. Hyperfiltration measurements revealed that a prolonged exposure of such CA-membranes to diluted polyelectrolyte solutions suffices to cause a substantial increase in their salt rejection properties (R). The increase in R depends on the initial salt rejection (R₀) of the CA membrane. ΔR_max were observed forR_o = 50 and R₀= 43 for 2-PVP and PVA respectively.Streaming potential measurements indicate the presence of acidic groups on the surface of untreated CA membranes and their interaction with the quaternary amino groups after treatment with 2-PVP. Spectrophotometric measurements do not, however, indicate that a significant amount of 2-PVP may be adsorbed on a non-porous surface of powdered acetyl cellulose. The experimental findings have been rationalized in terms of a snake-cage mechanism of formation of the dynamic membrane. Matching of the molecular weight distribution of the polyelectrolyte and the pore size distribution in the support is thus an essential condition for the formation of such membranes.     

热泵耦合甲醇多效精馏节能新工艺

粗甲醇精馏的能耗是影响甲醇生产成本的关键因素之一。虽然五塔多效精馏可以降低精馏过程能耗,但仍存在相当的低品位余热未利用,为进一步降低五塔多效精馏工艺的能耗,本研究引入机械蒸汽再压缩式（MVR）热泵,在常压塔提馏段增设辅助再沸器,形成热泵耦合多效甲醇精馏新工艺。基于新工艺的全流程模拟数据,文章利用夹点技术对热泵设置的合理性进行分析,采用能耗、效能系数（COP）和年总成本（TAC）等指标对新工艺过程进行评价。结果表明：热泵耦合多效甲醇精馏新工艺中热泵设置合理,冷负荷为24.7MW,再沸器总热负荷为22.25MW,COP为22.5,相比五塔多效精馏工艺,冷负荷、热负荷以及TAC分别降低33.76%、32.64%和26.97%。热泵耦合多效甲醇精馏新工艺节能效果显著。     

Ethyl acetate as a bio-based solvent to reduce energy intensity and CO2 emissions of in situ bitumen recovery

We introduce ethyl acetate (EA), a bio-based chemical, as a potential solvent for bitumen recovery through comprehensive phase behavior and numerical simulation studies. Phase behavior and thermophysical properties of EA/live bitumen are measured at temperatures and pressures up to 190°C and 4 MPa, respectively. Experimental studies suggested that coinjection of EA with steam can reduce the bitumen viscosity by several orders of magnitude. Our numerical simulations show that coinjection of 2–8 mol% EA with steam can significantly reduce the steam-oil-ratio (SOR) by almost 0.9 units while increasing the bitumen production rate. This reduction in SOR can be translated to significant energy saving of ~2.2 GJ, emission reduction of ~120 kg of CO₂, and wastewater reduction of ~120 m³ per ton of the produced bitumen, which are almost 20–25% lower than the steam-assisted gravity drainage (SAGD) process.     

Development of support vector regression (SVR)-based model for prediction of circulation rate in a vertical tube thermosiphon reboiler

The hydrodynamics and heat transfer in a thermosiphon reboiler interact with each other making the process very complex. Prediction of the rates of heat transfer and thermally induced flow are the primary requirements for the design of thermosiphon reboilers. The objective of this study was to develop, for the first time, a unified data-driven model, for the prediction of circulation rate in a thermosiphon reboiler for different pure components with wide variation in thermo-physical properties and operating parameters, using support vector regression (SVR)-based modeling technique. In the present work, 148 experimental data points from accessible sources, including the author's own study were used. First, a multiple regression (MR) model for circulation rate (in the form of Reynolds number) was developed as a function of dimensionless parameters namely, Peclet number for boiling (Pe_b), Subcooling number (K_sub), and the Lockhart–Martinelli parameter (X_tt), followed by the formulation of an SVR-based model. Statistical analysis revealed that the proposed generalized SVR-based model had high prediction accuracy with an average absolute relative error (AARE) of 3.82%, root mean square error (RMSE) of 0.0717, leave-one-out cross validation (Q²_LOO) of 0.9975 and mean relative error (MRE) of 0.0288 on the training data. Corresponding values of 6.11% AARE, 0.0816 RMSE, 0.9991 leave-one-out cross validation on test data (Q²_ext) and 0.0541 MRE were obtained for the test data. A comparison of the SVR-based correlation was made with the MR model and with some selected empirical correlations in the literature. It was observed that the proposed SVR-based model significantly exhibited an enhanced prediction and generalization performance.     

Grafting onto wool. XIV. Graft copolymerization of vinyl monomers by use of Mn(AcAc)3 as an initiator

Ethyl acrylate (EA), butyl acrylate (BA), and vinyl acetate (VAc) have been graft copolymerized onto Himachali wool fiber in an aqueous medium by using Mn(AcAc)₃ as an initiator. Graft copolymerization was studied at 45°, 55°, 65° and 75°C for various reaction periods. Percentage of grafting and percent efficiency were determined as functions of concentration of monomer, concentation of initiator, concentration of nitric acid, time, and temperature. Several grafting experiments were carried out in the presence of various additives which included: (i) pyridine and (ii) Et₃ N. EA, BA, and VAc were found to differ in reactivity towards grafting and followed the order: EA > BA > VAc.     

Pervaporation of flavors with hydrophobic membrane

Using a pervaporation process, a surface-modified hydrophobic membrane was used for recovery of esters which are volatile organic flavor compounds; ethyl acetate (EA), propyl acetate (PA), and butyl acetate (BA). A surface-modified tube-type membrane was used to evaluate the effects of the feed concentration (0.15–0.60 wt%) and feed temperature (30–50 °C) on the separation of EA, PA, and BA from dilute aqueous solutions. The permeation flux increased with the increasing feed ester concentration and operating temperature. EA, PA, and BA in the permeate were concentrated up to 9.13–32.26, 11.44–34.95, and 14.96–36.37 wt%, respectively. The enrichment factors for the 0.15–0.60 wt% feed solution of EA and BA were in the range of 48.5-62.8 and 97.7-101.5, respectively. Phase separation occurred in the permeate stream because the ester concentration in the permeate was above the saturation limit. This meant that selectivity of the membrane was high enough for the recovery of esters from dilute aqueous solution, even though the enrichment factor of the membrane was lower than that of non-porous PDMS membrane. The fluxes of EA, PA, and BA at 0.60 wt% (6,000 ppm) feed concentration and 40 °C were 254, 296, and 318 g/m².hr, which are much higher than those obtained with polymer membranes. In the case of non-porous PDMS at feed concentrations of 90-4,800 ppm and at 45 °C, it was reported that the permeate flux of EA was 1.1–5.8 g/m^2.h. Compared to non-porous PDMS, the surface-modified membrane investigated in this study showed a much higher flux and enough selectivity of esters.     

不同热集成变压精馏工艺分离乙酸乙酯/正己烷共沸物的优化与控制

基于变压精馏分离乙酸乙酯/正己烷共沸体系两塔的温差,利用Aspen Plus软件,以年度总成本最小为目标函数,对部分及完全热集成变压精馏工艺进行了稳态模拟及优化。在此基础上,利用Aspen Dynamics软件开发了多种控制结构,通过引入不同进料流量及组成的扰动测试控制结构的有效性。结果表明,完全热集成变压精馏工艺比部分热集成变压精馏工艺的经济性稍好。动态响应结果表明,部分热集成变压精馏工艺的压力?补偿温度控制结构可有效处理不同程度的干扰,能有效提高控制结构对干扰的响应速度,缩短达到新稳态的时间,保证乙酸乙酯和正己烷产品纯度在99.9wt%之上;而完全热集成变压精馏工艺的组分?温度串级控制结构仅能处理较小的组分和流量干扰,实现稳健控制,无法处理较大的干扰。综合比较两种工艺的经济性和可控性,认为部分热集成变压精馏工艺分离乙酸乙酯/正己烷共沸体系优于完全热集成变压精馏工艺。     

Biosorption studies of Cu(II) onto Mansonia sawdust: Process design to minimize biosorbent dose and contact time

The aim of this paper is to examine the various operating processes and determine the overall biosorption rate and how each of the processes influences biosorption. The results revealed that external mass transfer, film diffusion and ion exchange were predominant at the initial 5 min of biosorption and their rate constants were measured. The pseudo-second order model rate constants were determined and the relationship between these constants and the biosorption performance such as the approaching equilibrium factor, R_w, the rate factor k₂q_e, the biosorption half-life (t^0.5) and the operating time (t_x) were determined. The pore and film diffusion coefficients decreased with increasing copper(II) concentration. The values of initial biosorption factor, R_i, for the biosorption process showed that for all initial copper(II) concentrations, initial biosorption was faster than intraparticle diffusion. The activation energies, enthalpies, entropies and free energies for each of the operating processes were determined and the results showed that film diffusion had the highest activation energy and may be the overall rate limiting step. Mathematical models for the optimization of multistage process for minimum biosorbent mass and contact time were also developed.     

Synthesis and Radical Copolymerization of Ethyl Acrylate and Butyl Acrylate with N-[4-N'-(Phenylamino-carbonyl) phenyl] maleimide

Radical copolymerization of ethyl acrylate (EA) and butyl acrylate (BA) with 4-maleimidobenzanilide (MB), that is N-[4-N′-(phenylaminocarbonyl)phenyl]maleimide, initiated by AIBN was performed in THF solvent at 65°C. Nine copolymer samples of each type were prepared using different feed ratios of comonomers. All the polymer samples have been characterized by solubility test, intrinsic viscosity measurements, FT-IR and ¹H-NMR spectral analysis, and thermo-gravimetric analysis. The values of monomer reactivity ratios r₁ and r₂ are 1.13 and 0.48 in MB/EA system and 0.45 and 0.52 MB/BA system. Alfrey-Price Q-e values for MB were Q = 1.31 and e = 1.33 in MB/EA and Q = 2.04 and e = 2.06 in MB/BA systems. The initial decomposition temperature of copolymer samples were in the range 310 to 365°C.     

Optimization of Reactive Dividing‐Wall Distillation Column for Ethyl t‐Butyl Ether Synthesis

Ethyl t‐butyl ether (ETBE) was synthesized via reaction of ethanol and isobutene by means of a reactive dividing‐wall distillation column (RDWC). The RDWC was simulated using the RADFRAC model of Aspen Plus. Multi‐response optimization by response surface methodology (RSM) with desirability function approach was applied for maximizing product purities and minimizing energy requirements and CO₂ emissions simultaneously with a constraint that the difference in pressure drop across the dividing wall should be zero. The prediction from the RSM optimization agrees well with the simulation. The optimized RDWC provided an excellent purity of 99.99 mol % of the product ETBE with about one‐third reduction in energy requirements and CO₂ emissions as compared to reactive distillation.     

蒸汽压缩技术应用于再沸器的节能减碳分析

利用热工理论与工程技术分析了蒸汽压缩技术应用于再沸器时其技术特点以及对再热器运行成本和节能减碳的影响。从运行可靠性、经济性和节能减碳效果3个方面全面分析了蒸汽压缩技术应用于再沸器的优点与缺点。分析结果表明,蒸汽压缩技术应用于再沸器的技术在运行可靠性、经济性和节能减碳上都为再沸器提供更有优势的热源。运行可靠性上,蒸汽压缩技术的应用使得再沸器运行温度更加恒定可控,降低再沸器物料积碳和局部热应力过大的问题与风险;经济性上,蒸汽压缩技术的应用使得再沸器运行成本相比电导热油锅炉降低62.9%;节能减碳效果上,蒸汽压缩技术的应用使得再沸器比使用电导热油锅炉的情况下减碳65%左右,为国家实现碳中和的长远目标提供有效的技术升级。因此,开发更高效更宽工作范围的蒸汽压缩技术和应用技术迫在眉睫。     

原甲酸三甲酯-醋酸萃取精馏全局多目标优化

在生产杀菌剂嘧菌酯中间体过程中,反应物原甲酸三甲酯（TMOF）与生成物醋酸（HAc）发生共沸,导致反应物堆积和原料损耗。为解决共沸物分离问题,使用Hayden-O'Connell修正的UNIFAC基团贡献法研究其汽液平衡,设计常规萃取精馏（CED）、侧线萃取精馏（SED）、隔壁塔萃取精馏（EDWC）三种工艺,以分离组分摩尔纯度、再沸器热负荷（Q）、年度总费用（TAC）为目标,运用灵敏度耦合箱线图响应面法（S-BBD）对三种工艺参数分别优化。结果表明,优化方法预测值与实际值存在较优拟合关系, CED、SED、EDWC对TAC和Q的预测误差均不超过1%。分离纯度相同时,SED较CED节约10.37%TAC和6.88%热负荷,EDWC较CED节约10.65%TAC和10.53%热负荷,三种工艺方案均可为化工实际生产提供理论基础。