Optimized ionic liquids for toluene absorption

Conductor‐like‐screening model for real solvents (COSMO‐RS) method was used to analyze the solute‐solvent interactions and to screen Henry's law constant of toluene over 272 ionic liquids (ILs), to select high‐capacity absorbents. Thermogravimetric experiments were carried out to evaluate the toluene absorption by selected ILs at different temperatures and atmospheric pressure. Experimental equilibrium data were found in good agreement with COSMO‐RS predictions. Complete desorption of toluene by N₂ stripping was achieved, indicating an easy regeneration. The kinetic curves were described by a phenomenological diffusion model, obtaining effective diffusivities in reasonable concordance with those calculated by Wilke–Chang correlation. The separation process with selected ILs was modeled by Aspen Plus and a comparison with organic absorbents was carried out. Equilibrium‐ and rate‐based simulations were used to analyze the importance of thermodynamics and kinetics in toluene absorption by ILs. Current computational‐experimental research allowed selecting a set of suitable ILs for toluene absorption. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1648–1656, 2013     

Unstructured kinetic model for reuterin and 1,3‐propanediol production by Lactobacillus reuteri from glycerol/glucose cofermentation

BACKGROUND: Lactobacillus reuteri is unable to grow on glycerol as sole carbon and energy source hence, glycerol is used as an alternative hydrogen acceptor during growth on available carbohydrates. Thus, glycerol is converted to reuterin and 1,3‐propanediol (1,3‐PDL), both products with interesting industrial applications. These compounds are commonly produced by using resting cells in two‐step fermentation processes. RESULTS: The glycerol/glucose cofermentation by L. reuteri yields reuterin and 1,3‐PDL at a glycerol concentration higher than 100 mmol L⁻¹. An increase of glycerol concentration from 200 to 400 mmol L⁻¹ showed no additional stimulatory effect on ethanol and acetate production but consistently reduced the lactate concentration. It was also found that reuterin concentration reached a maximum value and subsequently decreased due to its conversion to 1,3‐PDL. An unstructured kinetic model was proposed to describe simultaneously microbial growth, substrates consumption and products formation. A multi‐response nonlinear regression analysis based on Marquardt algorithm combined with a Runge‐Kutta integration method was used to obtain the values of the fitting parameters. CONCLUSIONS: The optimum concentration of glycerol for maximum reuterin and 1,3‐PDL production was 200 mmol L⁻¹. The complete process was satisfactorily described by the kinetic model proposed. Copyright © 2008 Society of Chemical Industry     

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。     

Over‐expression of glycerol dehydrogenase and 1,3‐propanediol oxidoreductase in Klebsiella pneumoniae and their effects on conversion of glycerol into 1,3‐propanediol in resting cell system

BACKGROUND: Glycerol dehydrogenase [EC.1.1.1.6] and 1,3‐propanediol oxidoreductase [EC.1.1.1.202] were proved to be two of the key enzymes for glycerol conversion to 1,3‐propanediol in Klebsiella pneumoniae under anaerobic conditions. For insight into their significance on 1,3‐propanediol production under micro‐aerobic conditions, these two enzymes were over‐expressed in K. pneumoniae individually, and their effects on conversion of glycerol into 1,3‐propanediol in a resting cell system under micro‐aerobic conditions were investigated. RESULTS: In the resting cell system, over‐expression of 1,3‐propanediol oxidoreductase led to faster glycerol conversion and 1,3‐propanediol production. After a 12 h conversion process, it improved the yield of 1,3‐propanediol by 20.4% (222.1 mmol L⁻¹ versus 184.4 mmol L⁻¹) and enhanced the conversion ratio of glycerol into 1,3‐propanediol from 50.8% to 59.8% (mol mol⁻¹). Over‐expression of glycerol dehydrogenase in K. pneumoniae had no significant influence both on 1,3‐propanediol yield and on the conversion ratio of glycerol into 1,3‐propanediol in the resting cell system. CONCLUSION: The results were important for an understanding of the significance of glycerol dehydrogenase and 1,3‐propanediol oxidoreductase in 1,3‐proanediol production under micro‐aerobic conditions, and for developing better strategies to improve 1,3‐propanediol yield. Copyright © 2008 Society of Chemical Industry     

Application of a two‐stage temperature control strategy to enhance 1,3‐propanediol productivity by Clostridium butyricum

BACKGROUND: The purpose of the present work was to enhance 1,3‐propanediol productivity during the batch cultivation on a type of raw glycerol by application of a two‐stage temperature control strategy. RESULTS: First, the effect of the raw glycerol on microbial growth and 1,3‐propanediol production was investigated. The highest 1,3‐propanediol productivity, 1.93 g L^?1 h^?1, was achieved when the initial raw glycerol concentration was 6% (v/v). Second, the effect of temperature on microbial growth and 1,3‐propanediol production was investigated and kinetic analysis was carried out. The results indicated that 37 °C favored microbial growth while 35 °C was best for 1,3‐propanediol production. Finally, a two‐stage temperature control strategy was applied in 1,3‐propanediol production. The incubation temperature was kept at 37 °C from inoculation to 2 h and then switched to 35 °C. Compared with batch cultivations at 35 and 37 °C, the fermentation time was shortened from 10 to 9.2 h, resulting in an increase in 1,3‐propanediol productivity of around 11%. CONCLUSION: 1,3‐propanediol productivity was enhanced effectively by application of a two‐stage temperature control strategy. © 2012 Society of Chemical Industry     

Effect of diluent on poly(ethylene‐co‐vinyl alcohol) hollow‐fiber membrane formation via thermally induced phase separation

Poly(ethylene‐co‐vinyl alcohol) hollow‐fiber membranes with a 44 mol % ethylene content were prepared by thermally induced phase separation. A mixture of 1,3‐propanediol and glycerol was used as the diluent. The effects of the ratio of 1,3‐propanediol to glycerol in the diluent mixture on the phase diagram, membrane structure, and membrane performance were investigated. As the ratio increased, the cloud point shifted to lower temperatures, and the membrane structure changed from a cellular structure due to liquid–liquid phase separation to a particulate structure due to polymer crystallization. Better pore connectivity was obtained in the hollow‐fiber membrane when the ratio of 1,3‐propanediol to glycerol was 50:50, and the membrane showed about 100 times higher water permeability than the membrane prepared with pure glycerol. For the prepared hollow‐fiber membrane, the solute 20 nm in diameter was almost rejected. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 219–225, 2005     

Downstream processing of 1,3‐propanediol fermentation broth

The downstream processing of 1,3‐propanediol fermentation broth using flocculation, reactive extraction, and reactive distillation was studied. Cellular debris and soluble protein in the broth were flocculated by combined use of chitosan and polyacrylamide at optimal concentrations of 150 ppm and 70 ppm, respectively; the soluble protein in the broth decreased to 0.06 g L^?1, and the recovery ratio of the supernatant liquor to broth was greater than 99%. 1,3‐Propanediol and other alcohols were extracted from the supernatant liquor by reacting with butyraldehyde. In a four‐stage countercurrent extraction with the volume ratio of the extraction solvent to the aqueous phase being 20:100, more than 99% 1,3‐propanediol acetal (2‐propyl‐1,3‐dioxane) and 2,3‐butanediol acetal (2‐propyl‐4,5‐dimethyl‐1,3‐dioxolane) were recovered from the aqueous phase; 35% of the glycerol acetals were recovered. The acetals produced were hydrolyzed in a reactive distillation column using the strongly acidic cation‐exchange resin as catalyst, the bottom product obtained was a mixture of 1,3‐propanediol (407 g L^?1), 2,3‐butanediol (252 g L^?1), glycerol (277 g L^?1), and glycerol acetals (146 g L^?1). Copyright © 2005 Society of Chemical Industry     

Structures and properties of easily dyeable copolyesters and their fibers respectively modified by three kinds of diols

Three kinds of modified poly(ethylene terephthalate) copolyesters were synthesized, using sodium‐5‐sulfo‐bis‐(hydroxyethyl)‐isophthalate as the third monomer, 1,3‐propanediol (PDO), 2‐methyl‐1,3‐propanediol (MPD), and 2,2‐dimethyl‐1,3‐propanediol (neopentyl glycol or NPG) as the fourth monomer, respectively. The copolyester fibers were also prepared by melt spinning and drawing processes. The effect of PDO, MPD, and NPG on the synthesis and spinning process was investigated, and the structures and properties of both copolyesters and the produced fibers were characterized. The results exhibited that the structural difference of PDO, MPD, and NPG played an important role in the synthesis and spinning process, and significantly affected the structures and properties of both copolyesters and the produced fibers, which thereby resulted in the difference in terms of dyeability improvement of copolyester fibers. The dyeing at boiling temperature under normal pressure experiments of copolyester fibers in both disperse dyebath and cationic dyebath revealed that incorporation of the fourth monomer could improve the dyeability of copolyester fiber, and copolyester fiber containing MPD unit had better dyeability due to a looser, more accessible structure when compared with the fiber containing PDO or NPG unit. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The effect of raw glycerol concentration on the production of 1,3‐propanediol by Clostridium butyricum

Raw glycerol, the main by‐product of the bio‐diesel production process, was converted to 1,3‐propanediol by Clostridium butyricum F2b. In batch cultures, 47.1 g dm^?3 of 1,3‐propanediol were produced. Continuous cultures were conducted at a constant dilution rate (= 0.04 h^?1) and various inlet glycerol concentrations with 1,3‐propanediol produced at levels up to 44.0 g dm^?3. At increasing glycerol concentrations in the inlet medium, biomass yield decreased. This decrease was attributed to the microbial metabolism being directed towards the biosynthesis of organic acids (and hence carbon losses as CO₂) instead of biochemical anabolic reactions. An autonomous analytical model was developed, and quantified the effect of inlet glycerol concentration on the production of biomass and metabolites. Indeed, high inlet substrate concentrations positively affected the biosynthesis, principally of butyric acid and to a lesser extent that of acetic acid. In contrast, at increased glycerol concentrations, the relative increase of 1,3‐propanediol production per unit of substrate consumed was lower as compared with that of acetic and, mainly, butyric acid. This could be explained by the fact that the butyric acid pathway represents an alternative and competitive one to that of 1,3‐propanediol for re‐generation of NADH₂ equivalents in the microbial cell. Copyright © 2004 Society of Chemical Industry     

低压高密度聚乙烯装置动态模拟模型开发策略浅谈

讨论了应用通用流程模拟软件AspenPlus、聚合物模拟软件PolymersPlus及动态模拟软件AspenDynamics开发低压高密度聚乙烯装置反应系统动态模型的策略和方法。     

Design and economic analysis of the technological scheme for 1,3-propanediol production from raw glycerol

A technological scheme for producing 1,3-propanediol from raw glycerol was designed, simulated, and economically assessed. The production process was composed of three main stages, namely: glycerol purification, glycerol fermentation, and 1,3-propanediol recovery and purification. First, a typical stream of raw glycerol was purified up to 98 wt %, and then the fermentation took place in a two continuous stages process by means of a Klebsiella pneumoniae strain. For the fermentation stage, a rigorous analysis was carried out using a kinetic model considering both substrate and products inhibition. Thus, multiplicity of steady states and hysteresis loops were studied for the first fermentation stage. Also, in order to optimize both the outlet concentration of 1,3-propanediol and its productivity, three different objective functions were analyzed. As result, each objective function led to an optimal condition, such as: the highest global yield to 1,3-propanediol (0.599 mol/mol), the highest outlet concentration of 1,3-propanediol (0.512 mol/L), and the highest global productivity (1.157 × 10^?2), respectively. Then, the downstream process for 1,3-propanediol recovery and purification was designed based on a reactive-extraction process and a reactive-distillation process. This downstream process was applied to each scenario analyzed on the fermentation stage. Finally, the three scenarios were economically assessed and the lowest production cost was obtained for the third scenario. Simulation process and fermentation analysis were performed using Aspen Plus and MatLab respectively, while the economic assessment was carried out using the Aspen Icarus Process Evaluator.     

Aspen Plus模拟在氟化工中的应用研究

Aspen Plus是生产装置设计、稳态模拟和优化的大型通用流程模拟系统。全球各大化工、石化、炼油等过程工业制造企业及著名的工程公司都是Aspen Plus的用户。举例介绍了Aspen Plus模拟在氟化工中的应用,分析可能存在的困难,并展望Aspen Plus模拟在氟化工中的应用前景。     

Modelling aspects of the biotechnological valorization of raw glycerol: production of citric acid by Yarrowia lipolytica and 1,3‐propanediol by Clostridium butyricum

Raw glycerol, produced in significant quantities during several industrial processes, could be further considered as a potential substrate for microbial conversions. In the present report, modelling approaches are used in order to quantify the kinetic behavior of microorganisms capable of producing growth‐ and non growth‐associated metabolites when cultivated on raw glycerol. Citric acid production by Yarrowia lipolytica strain ACA‐DC 50109 was successfully simulated by Monod‐, Verhlust‐ and Williams‐type models, while the optimized parameter values were found to be similar to those experimentally measured. It has been demonstrated that the production of citric acid from raw glycerol, in terms of specific production rate and conversion yield, was similar or even better as compared with that obtained during cultivation of yeasts or molds on various conventional (eg sugar‐based) media. The production of 1,3‐propanediol by Clostridium butyricum strain F2b from raw glycerol was successfully simulated by a Contois‐type model. It was found that the maximum theoretical 1,3‐propanediol productivity was comparable with the highest one achieved during growth of various bacterial strains on pure glycerol in batch and continuous cultures. Raw glycerol could be used as an alternative substrate for citric acid and 1,3‐propanediol production, and possibly for other microbial products. Copyright © 2003 Society of Chemical Industry     

2,3-丁二醇分离纯化中反应精馏的实验和模拟

对反应萃取-水解精馏法分离发酵液中2,3-丁二醇工艺中的水解精馏进行了实验和模拟研究。实验验证了4,5-二甲基-2-丙基-1,3-二氧戊环(DPD)水解精馏得到2,3-丁二醇的可行性。采用Aspen Plus建立反应精馏模型,以UNIFAC为热力学方程,RadFrac为反应精馏模块,对常压下DPD的水解精馏进行模拟,模拟结果与实验结果吻合较好。以2,3-丁二醇的收率为主要优化目标,考察最佳塔板数、进料位置、进料比、回流比和塔顶馏出比。模拟结果表明,在最佳操作条件下,塔釜2,3-丁二醇的收率为0.981,摩尔分率为0.150。     

D‐isosorbide and 1,3‐propanediol as plasticizers for starch‐based films: Characterization and aging study

In the present work, D‐isosorbide and 1,3‐propanediol are proposed as alternative plasticizers obtained from renewable resources. Plasticized starch films were prepared by solvent casting method. The influence of using different “green” plasticizers in the final properties of starch‐based films was analyzed. Besides, the characterization of the films was also performed after storage time in order to evaluate the effect of the plasticizer on aging. UV‐spectrophotometry results showed better optical properties for both glycerol and D‐isosorbide films with higher transparency. The thermal and mechanical properties resulted influenced by the nature of the plasticizer. It was demonstrated that water vapor permeability was governed by the starch‐water interactions, whereas the oxygen permeability depended on the plasticizer's nature. The storage time affected the surface, mechanical, and thermal properties of the plasticized starch films. Atomic force microscopy results concluded that the topography of the films changed due to aging. The use of D‐isosorbide as plasticizer reduced the evolution of the mentioned properties and enhanced the reliability of the material. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44793.     

Aspen plus在化工过程分析与合成课程教学中的应用

化工过程分析与合成是化工类实践性非常强的专业基础课,精馏塔的实践教学是教学的重点和难点。文章采用Aspen Plus软件,以甲醇制二甲醚的实际工艺为案例,对二甲醚精馏塔进行模拟、分析,同时使学生熟悉Aspen Plus软件的使用,为后续化工设计打下基础。     

物性估算在ASPEN PLUS软件中的应用

利用Aspen Plus软件提供的物性估算功能，计算发酵液中低浓度1,3-丙二醇分离的中间产物2-甲基-1，3-二噁烷（2MD）的物性，从而模拟分离过程，确定工艺条件，得到理想的产物结果。     

2-乙基丙烯醛精馏分离过程模拟与实验研究

基于Aspen Plus软件,利用软件的物性估算功能及UNIFAC-HOC热力学模块,完成了数据库中缺少组分2-乙基丙烯醛物性估算,获得了模拟所需基础数据,通过对软件的相平衡曲线、残余曲线的分析,设计了分离体系的4塔分离流程,采用简捷模拟、严格模拟和灵敏度分析模块完成精馏塔的设计和操作参数的优化,从而获得了纯度达到99%的2-乙基丙烯醛精馏分离流程和操作条件。间歇精馏实验表明:模拟共沸物组成符合实际过程,模拟结果可以指导实际过程的分析和设计。     

生物柴油副产粗甘油的精制工艺研究

对生物柴油副产物粗甘油的分离精制工艺进行了研究。采用减压蒸馏结合活性炭吸附脱色的方法对粗甘油进行了精制提纯,并对操作条件进行了优化,同时,利用过程模拟软件AspenPlus进行了模拟计算,实验结果和计算结果吻合。实验所得的甘油产品的纯度为99.5%,甘油收率为91.8%,原料中的甲醇回收率为96.0%,纯度为99.5%。     

C_4烃与DMF的基础物性处理

基于基团贡献法的UNIFAC模型在缺少参数的系统预测中,具有很高的应用价值。但是随着对C4组分各种测量数据的积累和C4组分中存在的多种异构现象,其它活度系数状态方程更能准确处理该非理想体系。利用文献数据,结合Aspen Plus软件的数据处理功能,回归出C4组分和DMF间的Wilson参数,并在此基础上建立DMF法1,3-丁二烯工艺的全流程模拟,结果显示此方法具有很好的准确性。