SIMULATION STUDIES OF THE REMOVAL OF WATER FROM ETHANOL BY A CATALYTIC DISTILLATION PROCESS

A new approach based on catalytic distillation (CD) technology was proposed to remove water from ethanol. Isobutylene was introduced to react with water in the CD column. The commercial software simulation tool Aspen Plus was used to investigate the effects of key design factors such as operating pressure and temperature, reactant ratios, reflux and distillate to feed ratios, number of separation and reaction stages, and feed and reaction zone location. It was found that the CD technology offers potential advantages of reduced energy consumption and reduced capital cost over traditional approaches for the removal of water from ethanol.     

含乙醇废水的超临界水氧化反应动力学及反应机理

研究了等温平推流反应器中乙醇的超临界水氧化反应（SCWO）,反应温度475～550 ℃、压力22～30 MPa、停留时间0.6～63.7 s、氧气与乙醇摩尔浓度比4.56～9.09.一氧化碳和二氧化碳分别是反应中间产物和最终产物.随停留时间增大、温度升高,乙醇去除率增大,压力和氧气浓度变化对过程无显著影响.以幂指数方程描述乙醇SCWO动力学,乙醇和氧气的反应级数分别为1和0,计算值和实验值相差基本在10%以内.超临界条件下分别以过氧化氢和氧气为氧化剂时乙醇的氧化反应无明显差别,亚临界条件下过氧化氢氧化速率大于氧气.基于对此现象的分析,作者推测：无论以过氧化氢或氧气作为氧化剂,在超临界水中,它们之间可以通过一系列自由基反应迅速达到平衡,且各物种的平衡分布与初始分布无关,体系的主要氧化过程在平衡分布下进行.     

超临界水氧化法处理醇类废水(Ⅰ)处理效果及过程参数的影响

研究了以超临界水氧化法（ ＳＣＷＯ）处理乙醇废水的过程。实验表明,一氧化碳和二氧化碳分别是反应中间产物和最终产物。５５０℃、２５ＭＰａ、停留时间大于１０ｓ时,ＳＣＷＯ能将乙醇完全氧化为二氧化碳,达到彻底处理的目的。随停留时间增大、温度升高,乙醇的去除率增大,而压力和氧气浓度的变化对过程没有显著影响。     

Hydrogen production from bioethanol reforming in supercritical water

Hydrogen production by reforming and oxidative reforming of ethanol in supercritical water (SCW) at the intermediate temperature range of 500-600 °C and pressure of 25 MPa were investigated at different ethanol concentrations or water to ethanol ratios (3, 20 and 30), with the absence and the presence of oxygen (oxygen to ethanol ratio between 0 and 0.156). Hydrogen was the main product accompanied with relatively low amounts of carbon dioxide, methane and carbon monoxide. Some liquid products, such as acetaldehyde and, occasionally, methanol were present. The ethanol conversion and hydrogen yield and selectivity increased substantially as the water to ethanol ratio and the reaction temperature increased. Ethanol was almost completely reformed and mainly converted to hydrogen giving a H₂/CO ratio of 2.6 at 550 °C and water to ethanol ratio of 30 without carbon formation. Coke deposition was favored at low water to ethanol ratio, especially at high temperatures (≥550 °C). The hydrogen yield improved as the ethanol was partially oxidized by the oxygen added into the feed at oxygen to ethanol ratios <0.071. It was evidenced that the metal components in Inconel 625 reactor wall reduced by a hydrogen stream acted as a catalyst promoting hydrocarbon reforming as well as water-gas-shift reactions while dehydrogenation of ethanol forming acetaldehyde can proceed homogeneously under the SCW condition. However, at high oxygen to ethanol ratio, the reactor wall was gradually deactivated after being exposed to the oxidant in the feed. The loss of the catalytic activity of the reactor surface was mainly due to the metal oxide formation resulting in reduction of catalytic activity of the reactor wall and reforming of carbon species was no longer promoted.     

硬脂酸镁合成新工艺

介绍一种在水介质中由硬脂酸与新生成的氢氧化镁进行皂化反应合成硬脂酸镁的湿法新工艺。与传统的复分解法工艺相比,新工艺反应温度明显下降、反应时间大大缩短、反应物料液-固比大大降低、滤饼湿质量分数显著减少,因此大大提高了生产效率,降低了能耗、水耗。     

吸附强化乙醇水重整制氢的工艺条件

采用吸附强化技术强化了乙醇水重整制氢过程。考察了温度、水醇比、液空速对无强化乙醇水重整制氢反应特性的影响,在此基础上研究了吸附强化乙醇水重整制氢反应特性。通过响应面法确定了吸附强化乙醇水重整制氢最优工艺条件为温度422～444 ℃、水醇比10.2～10.8、液空速0.13 h?1,在此条件下的氢产率为3.2 mol/mol,同比提高了51.7%,氢含量为88.91%,同比提高了22.9%,反应温度降低了178 ℃,降低了能耗,控制了CO2排放。     

Preparation of PVA membranes containing β-cyclodextrin oligomer (PVA/CD membrane) and their pervaporation characteristics for ethanol/water mixtures

Poly(vinyl alcohol) (PVA) membranes were modified by introducing β-cyclodextrin (β-CD) oligomer, which has an inclusion ability sensitive to size, structure, and hydrophilicity of the guest molecule. The modified membranes (PVA/CD membrane) were prepared by casting of the aqueous solutions of PVA and β-CD oligomer. The CD oligomer was immobilized in the membranes by cross-linking with glutaraldehyde. The cross-linking times were 1 and 8 h. The content of CD in the membranes was 33 wt %. The effects of CD on the pervaporation characteristics for water/ethanol were investigated by comparisons with those of the cross-linked PVA membranes. For the 1 h cross-linked membranes, CD increased both the water permeation rate and selectivity at lower ethanol concentrations in the feed. At higher ethanol concentrations, CD increased the water selectivity, but it decreased the water permeation rate. For the 8 h cross-linked membranes, at lower ethanol concentrations, CD increased the water permeation rate, but the water selectivity through the PVA/CD membrane was almost equal to that of the PVA membrane. At higher ethanol concentrations, CD increased the water selectivity and decreased the water permeation rate. These effects of CD can be interpreted in terms of the inclusion strength in the cavity and the reduction of the cross-linking density of the PVA phase in the membranes. © 1994 John Wiley & Sons, Inc.     

A Kinetic Study of Ethanol Steam Reforming Using a Nickel Based Catalyst

A kinetic study of ethanol steam reforming to produce hydrogen within the region of kinetic rate control was carried out. A Ni(II)–Al(III) lamellar double hydroxide as catalyst precursor was used. H₂, CO, CO₂ and CH₄ were obtained as products. Using the Langmuir–Hinshelwood (L–H) approach, two kinetic models were proposed. The first was a general model including four reactions, two of them corresponding to ethanol steam reforming and the other two to methane steam reforming. When high temperatures and/or high water/ethanol feed ratios were used, the system could be reduced to two irreversible ethanol steam reforming reactions.     

超临界水氧化法处理醇类废水(Ⅱ)反应路径及动力学

研究了超临界水氧化法（ＳＣＷＯ）处理乙醇废水过程的反应路径和动力学。乙醇ＳＣＷＯ反应的最终产物为Ｍ氧化碳,一氧化碳是此过程的中间产物。以幂指数方程描述乙醇ＳＣＷＯ反应动力学,得到对于乙醇的反应级数为１,对氧气的反应级数为 ０。求出活化能和指前因子分别为 ３．５１×１０５　Ｊ·ｍｏｌ－１和 ７．７４×１０２１ｓ－１。方程计算值和实验值吻合较好,误差基本在１０％以内。     

The Chatham demonstration: From design to operation of a 20 m/d membrane-based ethanol dewatering system

Distillation/dehydration represents the largest fraction of the energy used in the production of ethanol. The Siftek™ technology introduced in this paper carries the potential of reducing energy consumption of distillation/dehydration by up to 50% through the single pass removal of water from the water/ethanol stream at the beer column outlet, using a novel membrane process.Siftek™ is a polymeric membrane that can be used to dry ethanol in the vapor phase. The membrane preferentially permeates water over ethanol in a continuous process. Energy reductions are obtained because this membrane is well suited to remove large quantities of water without phase change.The Siftek™ technology has been piloted since August 2006 in a Greenfield Ethanol plant in Tiverton, Ontario, Canada. The Tiverton unit has a capacity of 1 m³/d and has been producing fuel ethanol from a feed containing between 75 and 90 wt.% ethanol in a single stage system.Based on the successful operation of the pilot, it was decided to scale-up the technology. A two-stage membrane system with a capacity of 20 m³/d was built for the Greenfield Ethanol plant in Chatham, Ontario, Canada. The unit is equipped with full-scale commercial membrane modules and is capable of treating a beer-column feed containing 60-70 wt.% ethanol, producing > 99 wt.% fuel-grade ethanol.     

环氧丙烷水合制丙二醇反应精馏新工艺

本文利用环氧丙烷水合反应系统具有较大沸点差的特点,提出制备丙二醇的反应精馏新工艺,并通过过程模拟对反应精馏塔的工艺条件进行了研究。与原有工艺相比,新工艺的进料摩尔水比从15～20降至1.5～3,生成丙二醇的选择性从85％提高到93％,单耗从0.947tPO/tPG下降至0.853tPo/tPG。     

SWELLING PROPERTIES OF POLY(N-VINYLIMIDAZOLE) HYDROGELS

The swelling capacity of poly(N-vinylimidazole) hydrogels in aqueous solutions and organic solvents was measured as a function of polymer network structure. In pure water, the swelling capacity decreases monotonously upon increasing the crosslinker ratio and the total comonomers concentration in the polymerization feed mixture. In methanol a similar behaviour was observed while in ethanol, the swelling capacity shows an abrupt change from large values to 0.01 grams of water per gram of dry gel, that is to say, PVI experience swollen-collapsed transitions with small changes of the gel crosslinking degree. Molecular weight of chains between crosslinks, determined from swelling measurements in methanol, scales with the product of the crosslinker and total comonomers concentrations in the feed mixture to m1.14-0.05. The dependence of the polymer solvent interaction parameter on the polymer concentration inside the swollen gel was also determined for water and ethanol.     

Coupling of reaction and separation at the microscopic level: esterification processes in a H-ZSM-5 membrane reactor

A catalytically active zeolite membrane has been used to displace equilibrium by selective water permeation during ethanol esterification. Unlike previous works in which water separation was carried out by zeolitic membranes that did not take part in the reaction, the H-ZSM-5 membrane used in this work had sufficient catalytic activity to carry out the esterification of ethanol with acetic acid, and at the same time was selective for water permeation. As a consequence, the reaction and separation functions could be coupled very efficiently, and the conversion obtained at the same feed rate and catalyst loading was greater than in conventional fixed bed reactors, or in reactors where the zeolite membrane was kept separated from the catalyst.     

Conversion of ethanol over zeolite H-ZSM-5

The conversion of ethanol over H-ZSM-5 was studied as a function of ethanol partial pressure, reaction temperature, weight hourly space velocity and Si/Al ratio. The results obtained were in qualitative agreement with most of those in the literature. Combination with all published results to give a significant regression model was not possible due to the large scatter of the data from various scientific groups. In mechanistic investigations, temperature programmed reaction measurements of ethanol, diethyl ether and ethene were performed. The formation of ethene from ethanol via direct elimination or from diethyl ether as intermediate could be confirmed. In the conversion of ethanol/water mixtures, the product distribution did not change significantly up to a water content of 60 wt%. Then, a pronounced increase of ethene formation and a considerable decrease of the yields of aromatics was observed. When several reaction mixtures from syngas conversion to ethanol were converted over H-ZSM-5, the coking rate depended on the product distribution in the feed. Product mixtures from processes with higher amounts of compounds having an unfavourable C/H ratio led to rapid deactivation of the zeolite.     

Sorption equilibria and diffusion coefficients of ethanol and water in the PVA membranes containing cyclodextrin

Effects of cyclodextrin (CD) on the pervaporation characteristics for water/ethanol through the PVA/CD membranes (PVA membranes containing β-CD oligomer) have been investigated in terms of sorption equilibria and diffusion coefficients based on the sorption–diffusion theory. The increase in water selectivity through the pervaporation by CD was due mainly to the changes in the diffusion coefficients by CD, which depended on the feed composition and the cross-linking time. The water selectivity through the sorption equilibria was not increased by the addition of CD, and the ethanol-sorption amount was increased by CD. These effects of CD were interpreted by the inclusion strength in the CD cavity and the cross-linking density of the PVA phase. © 1994 John Wiley & Sons, Inc.     

Thermo pervap: The next step in energy efficient pervaporation

Thermo pervaporation (PV) is a pervaporation process that makes use of low quality heat to recover or purify solvents from water. Based on this technology it is possible to integrate the condensation energy for the direct heating of the feed during pervaporation in one single module.This concept was experimentally investigated for the separation of ethanol from a mixture of ethanol-water. It was possible to obtain a heat recovery of 33% (meaning that 33% of the heat transferred to the feed stream is condensation heat) and fluxes up to 0.5 kg/m² h at high ethanol concentration.     

Chemical grafted 4-vinylpyridine onto polycarbonate membranes for pervaporation

4-Vinylpyridine-homografted-polycarbonate (PC-g-4VP) membrane was prepared for water perselective pervaporation. The conditions of the chemical grafting reaction for synthesis PC-g-4VP were studied in terms of the reaction time, reaction temperature, monomer concentration, and the concentration of initiator in the reaction. The effect of feed composition, degree of swelling, and operation on temperature on the pervaporation performances were investigated. It was found that water permeated through the PC-g-4VP membrane perferential in all range of feed compositions. The permeation rate and separation factor increased with increasing 4-vinylpyridine content in the membrane. PC-g-4VP membrane effectively improved both the water permeation rate and water–ethanol separation factor of the unmodified polycarbonate membrane. The total permeation rate of PC-4-VP membrane with 26.7% degree of grafting was 153 g/m² h, and the separation factor was above 6300 for a 90 wt % aqueous ethanol feed solution. © 1995 John Wiley & Sons, Inc.     

催化精馏水解醋酸甲酯研究

建立了一套催化精馏的小试装置 ,对催化精馏工艺在聚乙烯醇 (PVA)生产中取代固定床工艺水解醋酸甲酯(MeOAc)进行了实验研究。对催化精馏过程中影响MeOAc水解效果的 3个主要因素 :进料水酯比Rm,回流进料比Rf 及空速S ,进行了较详细的讨论 ,并与固定床工艺的水解效果进行了对比。结果表明 ,与固定床工艺相比 ,采用催化精馏工艺水解MeOAc可以大幅提高MeOAc转化率 ,并节省大量能量     

常压水介质直接法洁净合成硬脂酸镁

通过采用新工艺,实现了在常压水介质中由硬脂酸与碱式碳酸镁直接反应合成色泽好的高质量硬脂酸镁．试验研完表明：反应温度、反应物料液-固质量比对合成反应速率有较明显的影响;合成优等品硬脂酸镁的适宜的工艺条件为：反应温度80℃,反应物料液-固质量比6：1,反应时间300min。与传统的复分解法工艺相比,该工艺生产效率明显提高,能耗、水耗显著下降、由于可沿用复分解法工艺的生产设备,该工艺特别适用于现采用复分解法工艺的硬脂酸镁生产企业的环保化升级改造。     

Characterization of permeation behaviors of ethanol–water mixtures through sodium alginate membrane with crosslinking gradient during pervaporation separation

Dense sodium alginate (SA) membranes crosslinked with glutaraldehyde were prepared by a new solution technique, which had different extents of crosslinking gradient structures. The SA membranes having a crosslinking gradient structure were fabricated by exposing one side of the membrane to the reaction solution while blocking the other side by a polyester film to prevent the reaction solution from contacting it. The extent of the crosslinking gradient was controlled by the exposing time. When the swelling measurements were performed with uniformly crosslinked membranes in aqueous solutions of 70–90 wt % ethanol contents, it was observed that the crosslinking could reduce both the solubility of water in the membrane and the permselectivity of the membrane toward water. The pervaporation separation of the ethanol–water mixture of 90 wt % ethanol content was carried out with membranes with different extents of crosslinking gradients. As the crosslinking gradient was developed more across the membrane, the resulting flux as well as the separation factor to water was found to decrease while the membrane became stable against water. The pervaporation performances of the membranes with different membrane loadings in a membrane cell were also discussed using the schematic concentration and activity profiles of the permeant developed in them. The pervaporation separations of the ethanol/water mixtures through the membrane with an optimal crosslinking gradient were performed at different feed compositions and temperatures ranging from 40 to 80°C. The change in the membrane performance due to the relaxation process during pervaporation was observed with the operating temperature and feed composition. The relaxational phenomena were also elucidated through an analysis of the experimental data of the membrane performance measured by repeating the operation in a given temperature range. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1607–1619, 1998