THE SEPARATION OF ISOPROPYL ETHER FROM METHYL ETHYL KETONE BY EXTRACTIVE DISTILLATION

Isopropyl ether (IPE) cannot be completely separated from its mixtures with methyl ethyl ketone (MEK) by distillation because of the presence of the minimum binary azeotrope. However these two can be readily separated by using extractive distillation in which the extractive distillation agent is a higher boiling oxygenated, nitrogenous and/or sulfur containing organic compound or a mixture of these. Typical examples of effective agents are: ethylene carbonate; adiponitrile and 1,4-butanediol; sulfolane, dimethyl-sulfoxide (DMSO) and triethylene glycol.     

Design and control of reactive distillation for ethyl and isopropyl acetates production with azeotropic feeds

Reactive distillations for the production of ethyl acetate (EtAc) and isopropyl acetate (IPAc) are classified as the type-II process where the first column consists of a reactive zone and a rectifying section followed by a stripper [Tang et al., 2005. Design of reactive distillations for acetic acid esterification with different alcohols. A.I.Ch.E. Journal 51, 1683-1699]. Instead of using pure alcohols and acetic acid as reactants, this paper studies the effects of reactant purity on the design and control of reactive distillation. This offers significant economical incentives (by reducing raw materials costs), because ethanol forms an azeotrope with water at 90 mol% and isopropanol/water has an azeotrope at 68%. The purities of the acid is set to 95% for acetic acid (industrial grade), 87% for ethanol, and 65% for isopropanol. The results show that the total annual costs (TAC) increase by a factor of 5% for EtAc and 8% for IPAc production using reactive distillation. Next, the operability of the reactive distillations with azeotrope feeds is explored. Three disturbances, feed flow, acid feed purity, and alcohol feed composition, are introduced to assess control performance using dual-temperature control and one-temperature-one-composition control. Simulation results indicate good control performance can be achieved for reactive distillation with azeotropic feeds.     

THE SEPARATION OF ACETONE-METHANOL MIXTURE BY EXTRACTIVE DISTILLATION

Acetone and methanol can not be readily separated by ordinary distillation because of the presence of the minimum boiling azeotrope. Either acetone or methanol can be the overhead product when an appropriate agent is applied in extractive distillation. An unusual phenomenon, “temperature inversion”, was observed when ketones were used as the extractive distillation agents. The dissolving of the vapors into the liquid phase could be the cause for the overhead at a temperature higher than that of the stillpot.     

THE SEPARATION OF m-DIISOPROPYLBENZENE FROM p-DIISOPROPYLBENZENE BY AZEOTROPIC DISTILLATION

m-Diisopropylbenzene can be separated from p-diisopropyl-benzene by azeotropic distillation when the azeotrope forming agent is selected from certain ketones, e.g. acetophenone; alcohols, e.g. o-isopropyl-phenol; esters, e.g. methyl benzoate; ethers, e.g. dipropylene glycol dimethyl ether or nitrogeneous compounds, e.g. 2-nitrotoluene.     

THE RECOVERY OF ETHYL ACETATE BY EXTRACTIVE DISTILLATION

Ethyl acetate cannot be easily removed from either mixtures with ethanol and water because of the minimum ternary azeotrope or from methyl ethyl ketone because of the proximity of boiling points. Ethyl acetate can be readily recovered from mixtures with these two by using extractive distillation in which the extractive agent is a higher boiling oxygenated, nitrogenous or sulfur-containing organic compound or a mixture of these.     

乙酸乙酯的精制方法

介绍了几种乙酸乙酯的精制方法,并分析了它们的优缺点。分别介绍了用乙酸和乙醇酯化反应合成乙酸乙酯,通常可采用传统的四塔连续工艺过程;添加促进剂萃取精制过程;加饱和盐水萃取脱水工艺过程;加有机溶剂萃取分离过程;加恒沸剂共沸蒸馏和乙酸萃取反应精馏过程。乙醛缩合法生产乙酸乙酯的三塔连续精馏过程以及乙烯与乙酸气相催化反应的加水精制工艺过程。     

甲醇与碳酸二甲酯恒沸物的萃取精馏分离

在萃取精馏实验装置中,分别以乙酸异戊酯和邻二甲苯为萃取溶剂,研究了甲醇和碳酸二甲酯恒沸物的分离,通过实验考察了原料配比,回流比,塔釜温度（加热量）等工艺操作条件对取精馏过程和相应萃取溶剂再生的影响,为工业应用提供理论与实践基础。     

联合精馏分离四氢呋喃-水共沸物的实验及优化模拟

由于四氢呋喃与水会生成沸点64 ℃的最低共沸物,采用三塔联合精馏的方法对其进行分离。根据文献资料选择乙二醇作为萃取精馏过程的萃取剂,并在脱水塔中对萃取精馏塔产物进行脱水。选择Aspen Plus软件对工艺流程进行模拟。选择Wilson模型及RadFrac模块对单塔工艺参数进行模拟及优化,确定了各塔进料板与回流比等最适宜参数。经实验考察的项目结果均与模拟结论一致。脱水塔产物四氢呋喃含水量可低至170 μg/g。根据优化后的参数在Aspen Plus中进行全工艺流程的闭合与模拟,终产物四氢呋喃的质量分数可达0.9995,收率为0.9988。其质量分数优于常见双塔萃取精馏流程。     

合成氨工艺正丙醇废液精馏处理的工艺技术

采用共沸精馏技术处理合成氨工艺流程中脱碳工段产生的含大量正丙醇混醇废液。本文采用共沸精馏的方法,选用合理可行的共沸剂,在间歇精馏塔内进行正丙醇-水共沸物系的分离实验,优化了该共沸精馏技术处理工业混醇废液的最佳操作条件。结果表明：采用共沸精馏方法,以环己烷为共沸剂,可使原料液中20%～40%的正丙醇含量提纯至质量分数≥95%,塔顶回收的共沸剂质量分数≥97%。该工艺流程较大地减小了设备投资和能耗。实验表明采用共沸精馏技术用于正丙醇-水共沸物系的分离具有可靠性和实用性。     

DMC-甲醇-水三元混合物的萃取精馏分离工艺

运用Aspen Plus软件回归文献数据校正了碳酸二甲酯（DMC）-水（H₂O）混合物的UNIQUAC热力学模型参数,并以该模型为基础分析了水作为萃取剂萃取精馏分离DMC-甲醇（CH₃OH）-水三元混合物的分离原理,结合混合组分的三角相图和物料组成设计了反向萃取精馏工艺,发现选用水为萃取剂可以利用DMC-水的部分互溶特性,通过三塔精馏即可分离DMC-甲醇-水三元混合物,沸点较高的DMC和少量水由塔顶馏出,而沸点较低的甲醇和大部分水由塔底采出,避免了DMC-甲醇二元共沸物的形成。同时,在相同分离要求下设计了变压精馏工艺,通过对两个精馏工艺参数模拟优化,发现萃取精馏工艺的总冷凝负荷和总加热负荷分别为888.7kW和898.2kW,其总能耗较变压精馏工艺节约了47.2%,萃取精馏工艺的年总费用（TAC）比变压精馏工艺下降了48.8%。     

煤制乙二醇装置联产碳酸二甲酯精馏工艺优化

在煤制乙二醇的生产过程中,会副产碳酸二甲酯（DMC）、甲酸甲酯、甲缩醛等,目前煤制乙二醇联产残液大都未进行有效分离和纯化,只能作为低纯度碳酸二甲酯或廉价杂醇处理,这样不仅造成甲醇损耗,而且降低了装置应有的经济性,因此经济合理地回收碳酸二甲酯具有重要的意义。由于甲醇与DMC形成二元共沸物,常规精馏方法无法将二者彻底分离。本文总结了各种DMC-甲醇分离方法,并优选采用变压精馏技术进行甲醇与DMC分离。利用煤制乙二醇中富含碳酸二甲酯以及甲醇、甲酸甲酯等杂质的副产残液为原料,提出3种改进工艺,获得99.9%以上高纯度DMC产品。计算结果表明,3种工艺方法分别适用于含量低于高压共沸组成、高于常压共沸组成、90%以上浓度DMC物料的分离,实现以更低能耗、更优化流程获得高纯度DMC产品。     

The modification and analysis of vegetable oil for cheese making

Objectives of this study were (i) to incorporate short-chain fatty acids (SCFA) in vegetable oils to obtain a bland product that could be used as a milk fat substitute in cheese making and (ii) to improve the methods for fatty acid analysis of vegetable oils modified with SCFA. Short-chain triglycerides (SCTG) were synthesized by esterifying SCFA with glycerol, and using a toluene azeotrope to remove the water of esterification. SCFA from two sources were used: (i) commercial acids and (ii) acids isolated by double distillation of milk fat methyl esters. The SCTG had a bitter, unacceptable flavor, but after interesterification with high-oleic sunflower oil (HOSO) and deodorization, the flavor was quite acceptable. SCTG were incorporated into HOSO at 100 and 120% of the levels found in the milk fat, by sodium methoxide-catalyzed interesterification. For fatty acid analysis, milk fat and simulated milk fat were converted to their decyl ester derivatives and analyzed by gas chromatography without further purification. The method was accurate and rapid for fatty acid analysis of fats containing a wide range of fatty acid chain lengths. All modified HOSO gave bland and acceptable flavors and had a SCFA composition close to that of milk fat. Results from using the modified HOSO in cheese making are reported in a later paper.     

THE SEPARATION OF METHYL ACETATE FROM METHANOL BY EXTRACTIVE DISTILLATION

Methyl acetate cannot be completely removed from methyl acetate-methanol mixtures by distillation because of the presence of the minimum binary azeotrope. Methyl acetate can be readily removed as overhead product from mixtures containing it and methanol by using extractive distillation in which the extractive distillation agent is a higher boiling oxygenated, nitrogenous and/or sulfur containing organic compound or a mixture of these. Typical examples of effective agents are dimethylsulfoxide, glycerine plus propylene glycol, ethylene glycol plus dimethylsulfoxide plus 1,5-pentanediol. Methanol can be removed as the overhead product from methyl acetate when the extractive distillation agent is nitrobenzene, propylene carbonate or ethylene glycol phenyl ether.     

THE SEPARATION OF METHYL ACETATE FROM METHANOL BY EXTRACTIVE DISTILLATION

Methyl acetate cannot be completely removed from methyl acetate-methanol mixtures by distillation because of the presence of the minimum binary azeotrope. Methyl acetate can be readily removed as overhead product from mixtures containing it and methanol by using extractive distillation in which the extractive distillation agent is a higher boiling oxygenated, nitrogenous and/or sulfur containing organic compound or a mixture of these. Typical examples of effective agents are dimethylsulfoxide, glycerine plus propylene glycol, ethylene glycol plus dimethylsulfoxide plus 1,5-pentanediol. Methanol can be removed as the overhead product from methyl acetate when the extractive distillation agent is nitrobenzene, propylene carbonate or ethylene glycol phenyl ether.     

Design and Control of Heterogeneous Azeotropic Distillation for Separating 2‐Methylpyridine/Water

In industrial processes, 2‐methylpyridine/water mixtures can be separated via the conventional heterogeneous azeotropic distillation (HAD) using benzene as entrainer. 2‐Methylpyridine and water can form a heterogeneous azeotrope by themselves, based on which an improved HAD process is proposed. This allows for reducing the total operating cost and total annual cost (TAC) by more than one‐tenth compared with the conventional HAD process. Two different control structures were established for the enhanced HAD process. The results indicate that applying the feedforward ratio controllers to the control structure can handle the feed disturbances and maintain product purities with smaller transient deviations and shorter settling times.     

共沸蒸馏在化工生产中的应用与研究进展

共沸蒸馏为共沸物或相对挥发度接近于1的非理想物系的分离过程提供了选择。介绍了蒸馏残余曲线图的热力学原理,并以反应蒸馏生产乙酸乙酯工艺为例说明了蒸馏残余曲线图在流程设计等方面的应用。分别从夹带剂选择、过程设计、过程集成强化、过程控制等角度阐述了共沸蒸馏过程相关理论研究进展;在应用方面,主要综述了乙醇、异丙醇稀溶液、稀乙酸等脱水及回收利用情况,共沸蒸馏过程强化反应蒸馏、变压共沸蒸馏、共沸蒸馏耦合膜分离研究进展情况以及反应蒸馏工艺的局限性,并对其未来的发展前景作了展望。     

丙酮一步法生产MIBK装置的副产物精馏分离研究

针对丙酮一步法生产MIBK装置的副产物（丙酮、异丙醇、水、MIBK混合物）,采用间歇精馏分离得到纯度〉98％的丙酮、纯度〉99％的异丙醇和水恒沸物、纯度〉90％的MIBK。对分离得到的纯度〉99％的异丙醇和水恒沸物用乙二醇作为萃取剂进行萃取精馏分离得到纯度99．5％异丙醇,同时减压精馏回收乙二醇。     

Mechanism analysis of solvent selectivity and energy-saving optimization in vapor recompression-assisted extractive distillation for separation of binary azeotrope

Octane and p-xylene are common components in crude gasoline, so their separation process is very important in petroleum industry. The azeotrope and near azeotrope are often separated by extractive distillation in industry, which can realize the recovery and utilization of resources. In this work, the vapor–liquid equilibrium experiment was used to obtain the vapor–liquid equilibrium properties of the difficult separation system, and on this basis, the solvent extraction mechanism was studied. The mechanism of solvent separation plays a guiding role in selecting suitable solvents for industrial separation. The interaction energy, bond length and charge density distribution of p-xylene with solvent are calculated by quantum chemistry method. The quantum chemistry calculation results and experiment results showed that N-formylmorpholine is the best solvent among the alternative solvents in the work. This work provides an effective and complete solvent screening process from phase equilibrium experiments to quantum chemical calculation. An extractive distillation simulation process with N-formylmorpholine as solvent is designed to separate octane and p-xylene. In addition, the feasibility and effectiveness of the intensified vapor recompression assisted extraction distillation are also discussed. In the extractive distillation process, the vapor recompression-assisted extraction distillation process is globally optimal. Compared with basic process, the total annual cost can be reduced by 43.2%. This study provides theoretical guidance for extractive distillation separation technology and solvent selection.     

糠醛萃取精馏分离甲醇-碳酸二甲酯二元共沸物研究

采用糠醛作萃取剂 ,用萃取精馏法对甲醇 -碳酸二甲酯二元恒沸物进行分离 ,找到了合适的实验条件和色谱分析方法 ,得到纯度为 99. 7%的碳酸二甲酯产品 ;研究了萃取剂的配比对分离性能的影响 ,得到最佳萃取剂配比为糠醛 /甲醇 (质量比 )为 6～ 8;考察了萃取剂的循环使用对分离性能的影响 ,发现糠醛经减压蒸馏提纯后循环使用基本不影响分离性能 ;对整个过程物系的回收率进行了考察 ,发现各组分的回收率均比较高。结果表明糠醛是一种毒性较小 ,价格较低 ,分离效果比较理想的新型萃取剂。     

TOC Destruction of a Phenol/Water Azeotrope by “Photoreactive Distillation” Through an Incoherent Vacuum-UV Excimer Lamp

The simultaneous treatment of a phenol/water azeotrope by distillation and by vacuum-UV(VUV) oxidation with a Xenon excimer flow-through photoreactor (emission maximum λ_max of 172 nm) is demonstrated on a laboratory scale. The so-called “photoreactive distillation” of the phenol/water mixture led to a TOC-free distillate. Therefore, this combined process of distillation and VUV oxidation has unprecedented potentials in water recycling technologies. Furthermore, this novel concept of “photoreactive distillation” by using excimer VUV or UV lamps as flow-through photoreactors may open new fields of photochemical research.