Simulation study on a reactive distillation process of methyl acetate hydrolysis intensified by reaction of methanol dehydration

Methyl acetate (MeOAc) recovery from the polyvinyl alcohol (PVA) production is a difficult and heavy energy consuming process. In this work, a reactive distillation (RD) process of MeOAc hydrolysis intensified by methanol (MeOH) dehydration, as an auxiliary reaction, was proposed. Two different feeds with the mole ratio of MeOAc to MeOH at 1:1 and 1:9 were studied, and the effect of the operating pressure, the feed location and the reflux ratio on the RD column was analyzed. The simulations of reactive distillation were performed using a three phase non-equilibrium model implemented by gPROMS. As the limit of the reaction rate of MeOH dehydration, it is impossible to get 100% conversion of MeOAc and MeOH by a single RD column. Therefore, two novel processes for recovery of methyl acetate in PVA production were developed. The simulation results show that the high purity of dimethyl ether (DME) could be achieved with a complete conversion of MeOAc, and a large amount of energy demand and equipment costs can be reduced.     

超临界甲醇制备生物柴油的多元相平衡研究进展

超临界甲醇制备生物柴油与传统方法制备生物柴油相比具有着多方面的优点,包括无需催化剂、反应速率快、对原料要求低、产物不需要后处理,因而近年来越来越受到国际社会的关注。由于与酯转化相关的反应物、中间产物以及产物在甲醇中的高压相平衡是理解与调控超临界甲醇反应的基础,为更好的理解多元混合物高温高压相行为对于酯转化反应的控制条件和机理,需要对相关体系的高压相平衡、转酯化反应动力学以及二者之间的关系等基础性问题进行深入研究。但由于超临界流体对温度、压力变化的敏感性和高温高压取样的困难性,使得在相平衡方面的研究起步较晚,基础数据缺乏。本文比较了当前几种生物柴油生产方式的优缺点,同时对现有超临界甲醇制备生物柴油的多元相平衡研究进展情况进行了总结。     

反应精馏制备丁酸酐的过程模拟和实验研究

测定了乙酸-乙酸酐的汽液平衡数据,并拟合得到二元交互作用参数。使用Aspen Plus软件,选择NRTL-HOC热力学方程,在已获得的动力学数据基础上,对制备丁酸酐过程进行模拟和过程优化,得到酰化反应制备丁酸酐反应精馏过程适宜的条件:全塔理论级数18,回流比1.5,进料酸酐比(摩尔比)2.5,丁酸进料位置为第5块板,乙酸酐进料位置为第12块板,该条件下得到乙酸酐的转化率99.97%,塔顶乙酸质量分数99.25%,塔釜丁酸酐质量分数85.37%。以模拟结果为参考,在连续精馏塔中进行了实验验证,丁酸和乙酸酐分别从塔2/5,4/5处进料,酸酐比2.5,回流比1.5,此条件下乙酸酐转化率可达98.88%,塔釜丁酸酐质量分数为83.802%。实验值与模拟计算值有良好的一致性,相对误差<5%,在允许范围之内,验证了模拟计算的可靠性,为工业化提供了理论基础。     

聚碳硅烷的高温高压生成机理研究Ⅱ蒸馏产物的结构分析

以液态聚硅烷（LPS）在450℃反应得到的聚碳硅烷（PCS）粗产品为原料,经溶解、过滤、热处理后减压蒸馏,收集蒸馏馏分并进行表征,由此推出不同摩尔质量的PCS的典型结构,进而推测出LPS转化为PCS分子的机理是：随着温度的升高,LPS中的Si—Si键发生断裂、重排,转化为Si—C键,生成低分子碳硅烷;随着温度的继续升高,碳硅烷分子间发生脱氢、脱甲烷缩合反应,摩尔质量逐渐长大,生成PCS。     

聚碳硅烷的高温高压生成机理研究II蒸馏产物的结构分析

以液态聚硅烷(LPS)在450℃反应得到的聚碳硅烷(PCS)粗产品为原料,经溶解、过滤、热处理后减压蒸馏,收集蒸馏馏分并进行表征,由此推出不同摩尔质量的PCS的典型结构,进而推测出LPS转化为PCS分子的机理是:随着温度的升高,LPS中的Si—Si键发生断裂、重排,转化为Si—C键,生成低分子碳硅烷;随着温度的继续升高,碳硅烷分子间发生脱氢、脱甲烷缩合反应,摩尔质量逐渐长大,生成PCS。     

高温高压法液氯生产工艺的优越性

对比生产原理、工艺流程和生产条件,介绍齐化化工有限公司液氯生产用低温低压法生产工艺和高温高压法生产工艺,进一步说明高温高压法更节能.     

Comparison of emissions of a direct injection diesel engine operating on biodiesel with emulsified and fumigated methanol

Biodiesel is an alternative fuel for internal combustion engines. It can reduce carbon monoxide (CO), hydrocarbon (HC) and particulate matter (PM) emissions, compared with diesel fuel, but there is also an increase in nitrogen oxides (NO_x) emission. This study is aimed to compare the effect of applying a biodiesel with either 10% blended methanol or 10% fumigation methanol. The biodiesel used in this study was converted from waste cooking oil. Experiments were performed on a 4-cylinder naturally aspirated direct injection diesel engine operating at a constant speed of 1800 rev/min with five different engine loads. The results indicate a reduction of CO₂, NO_x, and particulate mass emissions and a reduction in mean particle diameter, in both cases, compared with diesel fuel. It is of interest to compare the two modes of fueling with methanol in combination with biodiesel. For the blended mode, there is a slightly higher brake thermal efficiency at low engine load while the fumigation mode gives slightly higher brake thermal efficiency at medium and high engine loads. In the fumigation mode, an extra fuel injection control system is required, and there is also an increase in CO, HC and NO₂ (nitrogen dioxide) and particulate emissions in the engine exhaust, which are disadvantages compared with the blended mode.     

萃取精馏分离甲醇-乙酸乙酯的模拟研究

通过Aspen Plus化工流程模拟软件,利用萃取精馏法,以二甲基亚砜(DMSO)为萃取剂,对甲醇-乙酸乙酯共沸物进行了分离模拟研究。确定最优工艺参数为:萃取精馏塔理论板数41,混合物进料位置25,萃取剂进料位置4,回流比2.1,溶剂比3.8;溶剂回收塔理论板数12,进料位置7,回流比0.7。萃取精馏塔塔顶乙酸乙酯质量分数达99.80%,溶剂回收塔塔顶甲醇质量分数达99.74%。对分离过程优化操作及设计提供了理论依据。     

热泵变压精馏分离乙二胺水溶液的模拟

基于乙二胺和水物系共沸组成随压力变化显著的特点,采用变压精馏工艺分离乙二胺和水物系;为了降低变压精馏工艺的能耗,提出了热泵变压精馏新工艺。使用Chem CAD软件,对变压精馏工艺和热泵变压精馏工艺进行了模拟。结果表明:采用变压精馏工艺和热泵变压精馏工艺都能实现乙二胺和水共沸物的高纯度分离,每个产品的纯度(质量分数)都可以达到99%;与变压精馏工艺相比,采用热泵变压精馏工艺,加热公用工程可节能62.24%;冷却公用工程可以节能49.51%。     

Epitaxial growth on nickel-plated diamond seeds at high pressure and high temperature

Epitaxial growth on nickel-plated diamond seeds at high pressure and high temperature (HPHT) was observed with graphite as carbon source. The thickness of the electroplating nickel film which acts as a catalyst/solvent ranges from 54.6 μm to 255.6 μm. The relationship between the Ni film thickness and diamond growth rate is investigated. When the nickel film thickness is from 90 μm to 129 μm, diamond crystals can nearly grow up to three times as large as the original seeds at ∼ 5.8 GPa and ∼ 1460 °C within 14 min. The mechanism of the crystal growth with nickel-plated diamond seeds under HPHT is discussed. The results and techniques might be useful for high quality saw-grade diamonds production and large diamond single crystal growth.     

Trickle-bed reactors: Tracer study of liquid holdup and wetting efficiency at high temperature and pressure

Liquid holdup and wetting efficiency were measured by means of stimulus-response (pulse-tracer) experiments in a trickle-bed reactor, packed with a commercial hydrodemetallization catalyst, and operated at 10 MPa and 330–370°C, with a superficial liquid velocity of 1.4 to 8.3 × 10^?4 m/s. The total liquid holdup was obtained from the first moments, and the external wetting efficiency from the second moments, of the response curves. The dynamic holdup obtained from the total holdup lies within the range described by existing correlations, but wetting efficiency is significantly lower than literature data obtained at ambient conditions.     

Photoelectrochemical study of nickel base alloys oxide films formed at high temperature and high pressure water

The oxide film formed on nickel base alloys at high temperature and high pressure water exhibits semi-conducting properties evidenced by photocurrent generation when exposed to monochromatic light. The use of macro- and micro-photoelectrochemical techniques (PEC and MPEC) aims to identify the different semiconductor phases and their distribution in the oxide film.Three different nickel base alloys were corroded in recirculation loop at 325 °C in pressurised water reactor primary coolant conditions for different exposition durations.PEC experiments on these materials enable to obtain macroscopic energy spectra showing three contributions. The first one, with a band gap around 2.2 eV, was attributed to the presence of nickel hydroxide and/or nickel ferrite. The second one, with a band gap around 3.5 eV, was attributed to Cr₂O₃. The last contribution, with a band gap in the range of 4.1-4.5 eV, was attributed to the spinel phase Ni_1−xFe_xCr₂O₄. In addition, macroscopic potential spectra recorded at different energies highlight n-type semi-conduction behaviours for both oxides, Cr₂O₃ and Ni_1−xFe_xCr₂O₄.Moreover, MPEC images recorded at different energies exhibit contrasted regions in photocurrent, describing the distribution of nickel hydroxide and/or nickel ferrite and Cr₂O₃ in the oxide film at a micron scale.It is concluded that PEC techniques represent a sensitive and powerful way to locally analyse the various semiconductor phases in the oxide scale.     

The use of dilute acetic acid for butyl acetate production in a reactive distillation: Simulation and control studies

The recovery of dilute acetic acid, which is widely found as a by-product in many chemical and petrochemical industries, becomes an important issue due to economic and environmental awareness. In general, separation of acetic acid in aqueous solution by conventional distillation columns is difficult, requiring a column with many stages and high energy consumption. As a result, the primary concern of the present study is the application of reactive distillation as a potential alternative method to recover dilute acetic acid. The direct use of dilute acetic acid as reactant for esterification with butanol to produce butyl acetate in the reactive distillation is investigated. Simulation studies are performed in order to investigate effect of the concentration of dilute acetic acid and key process parameters on the performance of the reactive distillation in terms of acetic acid conversion and butyl acetate production. In addition, three alternative control strategies are studied for the closed loop control of the reactive distillation. The control objective is to maintain the butyl acetate in a bottom product stream at the desired purity of 99.5 wt%.     

Continuous production of biodiesel with supercritical methanol: Optimization of a scale-up plug flow reactor by response surface methodology

A scale-up plug flow reactor was evaluated for the continuous production of biodiesel from refined palm kernel oil (PKO) with supercritical methanol and optimized by response surface methodology. The effects of the operating temperature (270–350 °C), pressure (15.0–20.0 MPa) and methanol:PKO molar ratio (20:1–42:1) were evaluated at a constant residence time of 20 ± 2 min by using a central composite design. Analysis of variance demonstrated that a modified quadratic regression model gave the best coefficient of determination (R² = 0.9615) and adjusted coefficient of determination (Adj. R² = 0.9273). The interaction terms in the regression model illustrated small synergistic effects of both temperature–pressure and temperature–methanol:PKO molar ratio. The optimal conditions were 325 ± 5 °C, 18.0 ± 0.5 MPa and a methanol:PKO molar ratio of 42 ± 2:1, attaining a maximum production rate of 18.0 ± 1.5 g biodiesel/min with a fatty acid methyl ester content of 93.7 ± 2.1%. The product obtained from the optimal conditions had high cetane number, and could be considered as a fuel additive for cetane number enhancement.     

Effects of free fatty acids,water content and co-solvent on biodiesel production by supercritical methanol reaction

In the present study, non-catalytic supercritical methanol (SCM) reaction was utilized to produce biodiesel from palm oil. The effects of free fatty acids and water content on the yield of biodiesel were investigated and subsequently compared with conventional catalytic reaction. In addition, the feasibility of utilizing co-solvent to reduce the operating conditions needed in SCM was carried out as well. Results show that catalytic reaction suffers from low yield with the presence of high water content in oil. On the other hand, the yield of SCM reaction was found to increase with the increment of water content in the reaction mixture. Hence, SCM has been shown to have a high tolerance for water content in oil, which is important in order to utilize other sources of triglycerides such as waste oil. On the other hand, non-polar solvent such as heptane was found to have potential to decrease the temperature required in the reaction.     

Inter-integration reactive distillation with vapor permeation for ethyl levulinate production: Equipment development and experimental validating

Ethyl levulinate, one of the main derivatives of levulinic acid (LA), is of significant potential as platform chemicals for bio-based materials. The esterification of LA was generally carried out in a conventional batch reactor or in a conventional reactive distillation column. However, traditional methods are hard to deal with equilibrium limited reactions and azeotropic issues. Therefore, the inter-integration reactive distillation with vapor permeation (R-VP-D) process, which integrated reaction, vapor permeation, and distillation into one single unit, is proposed in this paper and validated in the pilot-scale experiments. A comparative study is made between a pilot-scale RD column with and without VP module. Owing to the water-selective VP membrane and the ingenious design of related apparatuses, the R-VP-D process reveal a superiority in LA conversion of 21.9% maximum higher than RD without VP process and removing of product water about 53.6% from VP module, which indicates its promising industrial application in process intensification field.     

An experimental study of fragmentation of coals during fast pyrolysis at high temperature and pressure

An experimental apparatus has been developed in order to perform tests of primary fragmentation of solid fuels under severe heating conditions (up to 2200 K and 12 bar). Particles are laid on the strip and pyrolyzed under inert conditions, fragments are recovered and analyzed by a laser granulometer to assess the fragmentation propensity of the fuel.Experiments have been carried out at temperatures between 1400 K and 1900 K, heating rate of 5000 K/s, pressure in the range 1-12 bar. Four different coals have been studied: Gracem, Venezuelan, Omsky, and Kleincopje, classified respectively as anthracite, high and medium volatile bituminous coals.Results show that primary fragmentation at high heating rate and high temperature may result in the formation of relatively coarse fragments and sometimes in a multitude of fines. The probability of fragmentation and the propensity to form coarse versus small fragments varies from coal to coal. For a given coal fragmentation increases monotonously with temperature, whereas the effect of pressure is nonmonotonous.The role of different chemico-physical properties of coals on the pattern and the extent of primary fragmentation is discussed, in particular volatile matter content, ash melting point, rigidity and porosity of the carbon structure and swelling index.     

Synergistic effect of nitrogen and hydrogen on diamond crystal growth at high pressure and high temperature

Diamond crystals co-doped with nitrogen and hydrogen atoms are successfully synthesized in the metal–carbon system with melamine (C₃N₆H₆) additive in a series of experiments at temperatures of 1200–1740 °C and pressures of 5.0–6.0 GPa. Experimental results show that the crystallization of our obtained diamonds changes significantly, which is attributed to the simultaneous incorporation of nitrogen and hydrogen into the diamond crystal structure. IR measurement shows that the intervention of hydrogen effectively changes the nitrogen concentration and substitutional form, accompanied by a non-uniform distribution of nitrogen and hydrogen in the synthesized diamond. Raman measurement indicates that such non-uniform distribution of nitrogen and hydrogen in the synthesized diamond leads to the change of internal structure of diamond crystals. For the crystals co-doped with hydrogen and nitrogen, a special feature of photoluminescence spectroscopy is typically observed at 536 nm. Base on our results, a possible incorporated route is introduced for the crystallization diamond with simultaneous incorporation of nitrogen and hydrogen.     

Esterification of acrylic acid with methanol by reactive chromatography: Experiments and simulations

The esterification of acrylic acid with methanol using Amberlyst 15 as a stationary phase has been investigated using a chromatographic reactor. Several experimental runs at various operating conditions have been conducted on a batch column. A classical reactive chromatography model including lumped kinetics, a linear driving force transport model and a heterogeneous kinetic model for the catalytic reaction has been developed. The additional dispersion of concentration fronts due to density gradient effects has been accounted for in the model. The model parameters have been determined in a fast and reliable way by directly fitting the batch column experiments. In general, a good agreement between experimental and calculated results is obtained. The evaluation of the covariance of the fitted model parameters reveals important insights about the system behavior.Based on the detailed batch column model, a complete model of a simulated-moving-bed reactor has been implemented and its optimal point of operation for the synthesis of methyl acrylate from acrylic acid has been determined. Particularly when considering the low-operating temperature, we can regard this process as a possible competition for current technologies.