反应精馏与渗透蒸发膜分离耦合法合成乙基叔丁基醚

以乙醇和叔丁醇为原料 ,通过催化反应、精馏与渗透蒸发膜分离三单元耦合过程合成了乙基叔丁基醚(ETBE) ,建立了相关五元高度非理想体系的耦合过程数学模型 ,以改进的超松弛法对模型求解 ,并进行了模型校验和工艺操作参数的模拟寻优     

汽油添加剂乙基叔丁基醚(ETBE)的复合过程制备

利用国产固体酸催化剂,以低浓度乙醇及丙烯氧化副产品叔丁醇为原料,用反应精馏与膜分离相耦合的高新技术,直接制取高效无污染汽油添加剂乙基叔丁基醚（ETBE）。研究了不同种类催化剂对反应的影响,建立了反应动力学模型。考察了中空纤维膜除水的能力以及反应膜分离耦合效果。比较了反应精馏以及反应精馏与膜分离耦合后目的产品的得率。经有关部门鉴定,用该工艺生产的乙基叔丁基醚对提高汽油辛烷值的效果优于同类产品甲基叔丁基醚（MTBE）。     

Reactive distillation-pervaporation hybrid column for tert-amyl alcohol etherification with ethanol

The etherification of tert-amyl alcohol with ethanol was carried out in a reactive distillation column inserted by a zeolite NaA membrane tube. Experimental tests were carried out in both of a pervaporation module and a reactive distillation column. Under suitable conditions, the pervaporation tests have shown higher than 99.9% H₂O mole fraction in the permeate. The design by the residue curve maps has shown the alleviation of azeotropes of H₂O-reaction components mixtures under pervaporation. The experimental study at standard conditions has shown a gain of 10% in tert-amyl ethyl ether (TAEE) yield when the zeolite membrane tube was inserted inside the distillation column. Further improvements in TAEE yield were realized when the feed location was separated and the time factor or the reflux ratios was increased.     

Development of Cellulose Acetate Propionate Membrane for Separation of Ethanol and Ethyl tert-Butyl Ether Mixtures

Abstract

For pervaporation separation of ethanol and ethyl tert-butyl ether mixtures, a cellulose acetate propionate membrane was chosen as the experimental membrane because of its high selectivity and good mass fluxes. The properties of the membranes were evaluated by the pervaporation separation of mixtures of ethyl tert-butyl ether/ethanol and the sorption experiments. The experimental results showed that the selectivity and the permeates depend on the ethanol concentration in the feed and the experimental temperature. With increases of the ethanol weight fraction in the feed and the temperature, the total and partial mass fluxes increased. With respect to the temperature, ethanol mass flux obeys the Arrhenius equation. The selectivity of this membrane decreases as the temperature and the ethanol concentration in the feed increase. This membrane shows special characteristics at the azeotropic composition. In the vicinity of the azeotropic point, minimum values of ethanol concentration in the permeate and in sorption solution are obtained. The swelling ratios increase when temperature and the ethanol concentration in the feed are increasing. The ethanol concentration in the sorption solution is also influenced by the temperature and the mixture's composition. When the temperature increases, the sorption selectivity of the membrane decreases.     

A techno‐economic comparison of various process options for the production of 1,1‐diethoxy butane

BACKGROUND: Acetals can be considered important bio‐based diesel additives. The production of most of these compounds, from an alcohol and an aldehyde, suffers from low conversion due to thermodynamic limitations. These limitations can be overcome through the removal of the by‐product water. Previous studies showed that the in situ dehydration options of reactive distillation and pervaporation membrane reactor integration offer little advantage or at least not at reasonable unit dimensions. The aim of the present work is the development of a membrane based process and comparison with other alternatives (based on experimental data). RESULTS: Three different membrane processes were developed. The one in which the reaction mixture is recycled over a first dehydration membrane module and subsequently through a simple distillation column, was found to give the highest overall conversion (100%) at low recycle rates and reasonable membrane area. This process was techno‐economically compared with other possible alternatives: (1) a process based on a conventional tubular reactor and several distillation columns; and (2) a process based on reactive distillation. CONCLUSIONS: Efficient water removal by membranes avoids possible azeotropes in downstream distillation units making them much simpler, reducing considerably the unit sizes and the energy demand (40% lower). Copyright © 2012 Society of Chemical Industry     

Hybrid reactive distillation systems for n-butyl acetate production from dilute acetic acid

The recovery of dilute acetic acid, regarding as a waste stream in many chemical and petrochemical processes, becomes an important issue due to economic and environmental awareness. In this work, a simulation study on the direct utilization of dilute acetic acid to produce n-butyl acetate via esterification with butanol in a reactive distillation is presented by using Aspen Plus. The performance of a hybrid reactive distillation with a pretreatment unit, i.e., a conventional distillation or a pervaporation, is investigated. For a single reactive distillation system, it is found that higher overall energy of the system is required when the concentration of acetic acid is lowered. By considering the enrichment of acetic acid in the reactive distillation column feed from 35 to 65 wt.%, a hybrid pervaporation–reactive distillation requires lower energy than both the conventional distillation–reactive distillation system and the single reactive distillation.     

Crucial Role of Weak Acid Sites for Catalytic Performance of Zeolites in Ethyl tert-butyl Ether Synthesis

Catalytic activity of different zeolites: H,NH₄-form of mordenite-containing rock (H-CMK) and H-Beta with a Si/Al ratio of 15–407 (H-ВЕА) in ethyl tert-butyl ether (ETBE) synthesis in a packed-bed flow reactor at 80–180°C and 1?MPa has been studied. Acid characteristics of zeolites were determined by stepwise (Quasi-Equilibrium) ammonia thermodesorption. Three types of acid sites of different strength has been found, which is marked as weak (E_NH3?=?60–75?kJ/mol), medium (E_NH3?=?86–123?kJ/mol), and strong (E_NH3?=?112–145?kJ/mol). The correlation between ETBE productivity and the concentration of weak acid sites has been found. Thereby, it was established that weak acid sites of zeolites are the active sites in ETBE synthesis.     

Addition of an azeotropic ETBE/ethanol mixture in eurosuper-type gasolines

This study proposes an azeotropic ETBE/ethanol mixture as a possible oxygenated additive for the formulation of eurosuper-type gasolines. Two eurosuper gasolines with different chemical compositions and well defined characteristics of density, volatility and octane numbers are used. Gasoline formulations containing azeotropic mixtures display an intermediary behavior between that of ETBE (ethyl tert-butyl ether) and ethanol in gasoline blends. Formulations containing this additive offer advantages over ethanol (low volatility and low solubility in water) and ETBE (higher octane number and lower production cost). Gasolines with azeotropic additives show lower Reid vapor pressures (RVPs) than gasolines formulated with ethanol, and therefore low levels of volatile organic compounds, similarly to highly pure ETBE. The use of the azeotropic mixture containing ethanol (renewable, deriving from biomass) and ETBE (produced from ethanol and isobutene) in its formulation is environmentally attractive in industrialized countries due to the need to reduce carbon dioxide emissions.     

Separation of alcohol–water mixture by pervaporation through a reinforced polyvinylpyridine membrane

A membrane consisted of cross-linked poly(4-vinylpyridine) and reinforced by a nonwoven cloth made of poly(ethylene terephthalate) was prepared by copolymerization of 4-vinylpyridine with divinylbenzene in the presence of the nonwoven cloth. Pervaporation performance of this polyvinylpyridine membrane was examined at several feed alcohol concentrations and temperatures. The membrane showed water selectivity, and the permselectivity, α_W/_A, for the alcohol–water mixture was in the order isopropyl > propyl > tert-butyl > ethyl > methyl. The membrane showed a large permeability, and the pervaporation flux, ?, for the ethanol–water mixture was 7–13 kg/h per square meter of the membrane in pervaporation with sweeping of carbon dioxide under atmospheric pressure and at 40°C. The membrane was durable and long lasting for a prolonged-period, and permselectivity and permeability of the membrane did not fall off even after repeated use for 1000 h. © 1993 John Wiley & Sons, Inc.     

Separation of ethyl tert-butyl ether-ethanol by combined pervaporation and distillation

A cellulose derivative membrane (30 wt.% cellulose acetate butyrate (CAB) combined with 70 wt.% cellulose acetate propionate (CAP)) was prepared, and its properties were evaluated by the pervaporation separation of mixtures of ethyl tert-butyl ether (ETBE) and ethanol. The experimental results showed that the selectivity and permeability of the membrane were dependent on the blend composition, the processed feed and the experimental temperature. With respect to the temperature, the fluxes obeyed the Arrhenius equation. On the basis of these results, a separation process for the production of ETBE was developed by combining pervaporation and distillation. The distillation column was designed with the software ASPEN PLUS, and the liquid-vapour equilibria were predicted by the UNIFAC method. The area of the membrane was calculated according to the production capacity. It may be concluded that the combined process for the separation of mixtures of ETBE and ethanol is simple with high recovery of the ETBE product.     

Permeation behaviour in cellulose triacetate dense membrane during pervaporation separation of methanol/methyl tert-butyl ether mixture

The pervaporation separation of methanol/methyl tert-butyl ether through cellulose triacetate dense membranes has been carried out under different feed compositions, permeation temperatures and temperature cycles to investigate the permeation behaviour of the membrane during pervaporation process. The experimental data indicate that the plasticization effect has a decisive influence on pervaporation flux, permselectivity and permeation activation energy. The results show that the penetrants of different feeds are transported through the membrane by different pathways with the influence of plasticization effect at different temperatures. It has also been observed that plasticization had great effect on the membrane swelling and sorption selectivity. Furthermore, DSC results show that the membranes retain the influence of the plasticization effect after pervaporation separations are tested. © 2000 Society of Chemical Industry     

Separation of MTBE-Methanol Mixtures by Pervaporation

Abstract

Membranes made of a polymer blend of poly(acrylic acid) and poly(vinyl alcohol) were evaluated for the separation of methanol from methyl tert-butyl ether (MTBE) by pervaporation. The influence of the blend composition and the feed composition on the pervaporation performance were investigated. Methanol permeates preferentially through all tested blend membranes, and the selectivity increases with increasing poly(vinyl alcohol) content in the blends. However, a flux decrease is observed with increasing poly(vinyl alcohol) content. With increasing feed temperature the flux increases, and the selectivity remains constant. In addition, the influence of crosslinking on the permselectivity was investigated. The pervaporation flux decreases with increasing crosslinking density, but the selectivity is enhanced. This is due to a more rapid decrease in the component flux of MTBE compared to that of methanol.     

Production of ethyltert-butyl ether fromtert-butyl alcohol and ethanol catalyzed byβ-zeolite in reactive distillation

The synthesis of ethyl tert-butyl ether (ETBE) from a liquid phase reaction between tert-butyl alcohol (TBA) and ethanol (EtOH) in reactive distillation has been studied.β-Zeolite catalysts with three compositions (Si/Al ratio=13, 36 and 55) were compared by testing the reaction in a semi-batch reactor. Although they showed almost the same performance, the one with Si/Al ratio of 55 was selected for the kinetic and reactive distillation studies because it is commercially available and present in a ready-to-use form. The kinetic parameters of the reaction determined by fitting parameters with the experimental results at temperature in the range of 343–363 K were used in an ASPEN PLUS simulator. Experimental results of the reactive distillation at a standard condition were used to validate a rigorous reactive distillation model of the ASPEN PLUS used in a simulation study. The effects of various operating parameters such as condenser temperature, feed molar flow rate, reflux ratio, heat duty and mole ratio of H₂O : EtOH on the reactive distillation performance were then investigated via simulation using the ASPEN PLUS program. The results were compared between two reactive distillation columns: one packed withβ-zeolite and the other with conventional Amberlyst-15. It was found that the effect of various operating parameters for both types of catalysts follows the same trend; however, the column packed withΒ-zeolite outperforms that with Amberlyst-15 catalyst due to the higher selectivity of the catalyst.     

Production and Isolation of n‐Butyl Acrylate Using Pervaporation‐Aided Esterification Reaction: Kinetics and Optimization

Synthesis of n‐butyl acrylate by esterification of acrylic acid with n‐butyl alcohol was carried out in a batch membrane reactor. Optimization and design of the experiment was accomplished by response surface methodology with Box‐Behnken experimental design. The effects of different parameters like reaction temperature, catalyst concentration, molar ratio of alcohol to acid, and ratio of membrane surface to initial volume on water flux and conversion of acrylic acid were evaluated. A kinetic model for the esterification‐coupled pervaporation process was developed. Kinetic parameters were estimated by a nonlinear optimization technique in the MATLAB optimization toolbox. The experimental and simulation results were applied for developing a concept to effectively conduct a pilot‐scale esterification‐pervaporation experiment.     

Multiple Analysis in a Reactive Distillation Column for the Synthesis of tert‐Amyl Methyl Ether

tert‐Amyl methyl ether (TAME) is produced via reactive distillation. A simulation is set up and controlled on Aspen HYSYS v 8.0 for generating the highest purity of TAME. This simulation includes a plug‐flow reactor and a reactive distillation column. Emphasis was put on finding the optimal operating conditions of the reactive distillation column in order to get the maximum purity of TAME. The operational parameters were reflux ratio, number of reactive stages in the distillation column, and condenser pressure. The results indicated the optimal reflux ratio and condenser pressure which could be adapted to industrial scale.     

Analysis of TBA‐Based ETBE Production by Means of an Optimization‐Based Process‐Synthesis Approach

The current article presents the extension of a recently developed optimization‐based approach to process synthesis for process intensification. It generates phenomena‐based flowsheet options using superstructure optimization and provides a dedicated translation into equipment‐based flowsheets. The considered case‐study illustrates the application of the method for the analysis of ethyl tert‐butyl ether production, based on the conversion of tert‐butyl alcohol, under consideration of variable configurations of a rector network and a newly introduced pervaporation‐based membrane‐reactor block.     

Mechanism of anionic polymerization of (meth)acrylates in the presence of aluminium alkyls

Summary Methyl methacrylate was polymerized with tert-butyl lithium in the presence of triethylaluminium or triisobutylaluminium at 78°C in toluene. As indicated by GPC and MALDI-TOF mass spectrometry, the polymerization is accompanied by side reactions. The lower oligomers were fractionated by distillation and characterised by NMR, FT-IR, UV and electron impact (EI) mass spectrometry. All these data show that part of the polymer chains are carrying exactly one tert-butyl isoprenyl ketone unit. In order to avoid the formation of tert-butyl isoprenyl ketone a molar ratio of Al/Li>2 is necessary.Part 2, cf. Ref. 10     

Kinetic studies of liquid phase ethyl tert-butyl ether (ETBE) synthesis using macroporous and gelular ion exchange resin catalysts

Ethyl tert-butyl ether (ETBE) synthesis from ethanol (EtOH) and tert-butyl alcohol (TBA) was studied with different macroporous and gelular ion exchange resin catalysts. Purolite^® (CT-124, CT-145H, CT-151, CT-175 and CT-275) and Amberlyst^® (15 and 35) ion exchange resins were used for the present work. Effect of various parameters such as catalyst type, temperature, reactants feed molar ratio and catalyst loading were studied for the optimisation of reaction condition. Among the catalysts studied, Purolite CT-124 gave the best results for TBA conversion and selectivity towards ETBE. Kinetic modelling was performed with this catalyst and activation energy and water inhibition coefficient were determined. Heterogeneous kinetic models [e.g., Eley-Rideal (ER), Langmuir-Hinshelwood-Hougen-Watson (LHHW)] were unable to predict the behaviour of this etherification reaction, whilst the quasi-homogeneous (QH) model represented the system very well over wide range of reaction conditions.     

Solvent treatment of CTA hollow fiber membrane and its pervaporation performance for organic/organic mixture

Cellulose triacetate (CTA) hollow fiber membrane used to separate methanol/methyl tert-butyl ether (MTBE) by pervaporation (PV) has been prepared from CTA hollow fiber reverse osmosis (RO) membrane for desalination of brackish water with high salinity. Acetone was selected as a modification agent of CTA membrane. PV performance depended on the solvent concentration, the treatment time and modification temperature of CTA RO hollow fiber membrane soaked in the aqueous acetone. The results show that CTA hollow fiber membrane modified with the solvent has a superior performance both the separation factor and the permeate flux in the PV experiment conditions.     

Optimization of the ETBE (ethyl tert-butyl ether) production process

The synthesis of ETBE (ethyl tert-butyl ether) from the reaction of ethanol with isobutene is an exothermic reaction of equilibrium. To increase the conversion of isobutene requires operating the reaction system at low temperatures and with excess ethanol in order to displace the equilibrium towards the products. ETBE and ethanol form an azeotropic mixture which hinders the recycling of nonreacted ethanol in the process. The purpose of this work is to optimize the synthesis of ETBE eliminating the introduction of water into the system to break the ETBE/Ethanol azeotrope. The production process model proposed here eliminates the recycling of ethanol and suggests the use of the azeotropic mixture (ETBE/Ethanol) in the formulation of gasolines. The direct use of the azeotrope in the formulation of automotive gasolines reduces the implementation and production costs of ETBE.