Facile preparation of Cu(I) impregnated MIL‐101(Cr) and its use in a mixed matrix membrane for olefin/paraffin separation

Cu(I) impregnated MIL‐100(Cr) [denoted Cu@MIL‐101(Cr)] is fabricated by a facile method and utilized in mixed matrix membranes (MMMs) for propylene/propane separation. Cu(I) is prepared from a CuCl₂ solution via mild reduction process using sodium sulfite as the reducing agent. The filler is incorporated into a polystyrene‐b‐polybutadiene‐b‐polystyrene (SBS) block copolymer matrix to form MMMs. As a result, both the permeability and selectivity of propylene/propane are improved after Cu(I) impregnation. The best performance is obtained for SBS/Cu@MIL‐101(Cr) MMM, and these values represent 17% and 54% improvements compared to those of SBS/MIL‐101(Cr) MMM, respectively. This result is attributed to the π‐complexation of the loaded Cu(I) by propylene gas, indicating that Cu@MIL‐101(Cr) with internal Cu(I) and a high pore volume acted as an effective filler to aid propylene/propane separation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46545.     

负载离子液体的阳离子交换膜在烯烃/烷烃分离中的应用

制备了负载胆碱赖氨酸盐离子液体（[Ch][Lys]）的阳离子交换膜,测定并表征其膜的性能,研究其在电渗析下分离1-己烯/n-己烷的能力。结果表明,膜含水率和离子交换容量随离子交换树脂质量分数和离子液体含量的增加而增大;膜的面电阻随树脂质量分数增大而减小,随离子液体含量的增大而增大;膜中添加离子液体明显提高了其分离1-己烯/n-己烷的能力,当阳离子交换树脂含量为70%、离子液体添加量为15%时,所制的阳离子交换膜对1-己烯分离的选择性最高,其值可达9.5。     

丙烯/丙烷分离的ZIF-8膜研究进展

同碳数烯烃/烷烃的分离是目前石油化工行业中最耗能的过程之一,开发新型的、低能耗的丙烯/丙烷分离过程被认为是改变世界的七项化工分离技术之一。气体膜分离技术因其高效、节能和环境友好等优点被认为是一种可取代传统低温精馏分离丙烯/丙烷混合气体的新型技术。金属有机骨架材料ZIF-8的有效孔径介于丙烯和丙烷的分子动力学直径之间,可对丙烯/丙烷实现高效分离,是目前分离丙烯/丙烷性能最好的膜材料。本文系统总结了ZIF-8膜的制备方法及用于丙烯/丙烷高效分离的发展历程;探讨了ZIF-8膜微结构的调控,尤其是膜缺陷的修复及ZIF-8骨架柔性的控制;总结了ZIF-8膜在分离丙烯/丙烷时,过程参数对于分离性能的影响规律;并提出ZIF-8膜规模化制备及潜在工业分离丙烯/丙烷研究中存在的问题和未来发展方向。     

Ag+ contained complex membrane for the separation of C4 olefin/paraffin mixture

The C₄ olefin/paraffin mixture was separated by means of the PE modified reversible complexing membrane, polyethylene-g-acrylic acid-Ag₊(PE-g-AA-Ag₊). The olefin could be transported to the other side of the membrane by silver facilitating phenomenon owing to the formation of (Ag-olefin)₊ complex. The SEM-EDX spectrum showed a homogeneous silver ion distribution across the dense complex membrane's cross-section at higher than about 60% grafting. The gas permeation properties measured by a gas chromatographic method implied a silver ions facilitating effect towards olefin. At 30°C and 111.7% grafting, the complex membrane exhibited a trans-2-butene/isobutane selectivity of 12.5 and a cis-2-butene/isobutane selectivity of 9.2. The permeation activation energy of the C₄ olefins became lower than that of C₄ paraffin as a result of the silver ions facilitated effect. The cis-2-butene has a significant higher complex equilibrium constant than that of the trans-2-butene in complexing with the complex membrane.     

Modeling and analysis of the Lurgi‐type methanol to propylene process: Optimization of olefin recycle

This work proposed a strategy to improve the yield of light olefins of industrial methanol to propylene process by reducing the olefins recycled back into the main reactor and appending an olefin cracking reactor. The heterogeneous fixed‐bed model was employed to simulate the reactors with a robust mathematical procedure developed to determine the reactor configuration and the recycle flow rates of the olefins. Two methods were proposed for the modulation: the recycle ratio and species of the olefins, respectively. Results show that the yield of C₂–C₃ olefins can be improved up to 70% from the basement of about 60% when the ratio is reduced from 100% to less than 23% or when only butene apart from pentene and hexene is recycled back into the main reactor, and the latter method is more effective as its catalyst requirement is seven times less than the former's in the appended cracking reactor. © 2016 American Institute of Chemical Engineers AIChE J, 63: 306–313, 2017     

膜蒸馏过程强化及优化技术研究进展

膜蒸馏作为一种新型的膜分离技术,具有脱盐率高、可处理高浓度原料液等技术优势,近年来引起学术界及工业界的广泛关注.膜蒸馏技术可被应用于海水淡化,工业废水/苦盐水脱盐及糖、盐、果汁、有机/无机酸、碱液等的浓缩过程.但由于当前膜蒸馏能耗及成本较高,一定程度上限制了该技术的工业化.本文重点介绍了可用于强化膜蒸馏过程和优化该过程能量利用的方法及研究进展,主要包括膜材料和膜制备方法/工艺的进展、膜蒸馏过程操作条件的优化、改进膜组件和辅助装置的应用、太阳能和低品位热源的使用、蒸发冷凝潜热的回收以及耦合其他分离过程的复合膜蒸馏系统,同时分析了膜蒸馏技术处理高盐工业废水的应用前景,最后探讨和总结了膜蒸馏过程强化及优化的研究方向,为该技术的进一步发展提供了科学性指导.     

Ultrathin carbon molecular sieve membrane for propylene/propane separation

Ultrathin (down to 300 nm), high quality carbon molecular sieve (CMS) membranes were synthesized on mesoporous γ‐alumina support by pyrolysis of defect free polymer films. The effect of membrane thickness on the micropore structure and gas transport properties of CMS membranes was studied with the feed of He/N₂ and C₃H₆/C₃H₈ mixtures. Gas permeance increases with constant selectivity as the membrane thickness decreases to 520 nm. The 520‐nm CMS membrane exhibits C₃H₆/C₃H₈ mixture selectivity of ～31 and C₃H₆ permeance of ～1.0 × 10^?8 mol m^?2 s^?1 Pa^?1. Both C₃H₈ permeance and He/N₂ selectivity increase, but the permeance of He, N₂, and C₃H₆ and the selectivity of C₃H₆/C₃H₈ decrease with further decrease in membrane thickness from 520 to 300 nm. These results can be explained by the thickness‐dependent chain mobility of the polymer film which yields thinner final CMS membranes with reduction in pore size and possible closure of C₃H₆‐accessible micropores. © 2015 American Institute of Chemical Engineers AIChE J, 62: 491–499, 2016     

离子液体在低碳烯烃/烷烃分离中的应用研究进展

低碳烯烃/烷烃的高效分离是石油化工领域可持续发展的关键过程之一,传统的低温精馏过程选择性低、能耗大。离子液体作为一种结构可调的绿色溶剂为低碳烃的高效分离提供了新的思路。本文综述了近年来国内外离子液体在低碳烯烃/烷烃分离中的研究进展,总结了常规离子液体、功能化离子液体以及含过渡金属的离子液体在低碳烯烃/烷烃分离中的应用,阐明了离子液体中阴阳离子、功能化基团、过渡金属与低碳烯烃相互作用的机理,着重介绍了合成金属功能化离子液体、添加金属盐、添加金属纳米粒子3种向离子液体中引入过渡金属方式的特点以及过渡金属的种类、比例,有机配体的类型对离子液体烯烃/烷烃分离性能的影响,并探讨了该方向的研究和发展趋势。     

Integration of molecular dynamic simulation and free volume theory for modeling membrane VOC/gas separation

Gas membrane separation process is highly unpredictable due to interacting non-ideal factors, such as composition/pressure-dependent permeabilities and real gas behavior. Although molecular dynamic (MD) simulation can mimic those complex effects, it cannot precisely predict bulk properties due to scale limitations of calculation algorithm. This work proposes a method for modeling a membrane separation process for volatile organic compounds by combining the MD simulation with the free volume theory. This method can avoid the scale-up problems of the MD method and accurately simulate the performance of membranes. Small scale MD simulation and pure gas permeation data are employed to correlate pressure-irrelevant parameters for the free volume theory; by this approach, the microscopic effects can be directly linked to bulk properties (non-ideal permeability), instead of being fitted by a statistical approach. A lab-scale hollow fiber membrane module was prepared for the model validation and evaluation. The comparison of model predictions with experimental results shows that the deviations of product purity are reduced from 10% to less than 1%, and the deviations of the permeate and residue flow rates are significantly reduced from 40% to 4%, indicating the reliability of the model. The proposed method provides an efficient tool for process engineering to simulate the membrane recovery process.

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新型膜分离过程

介绍渗透汽化、膜萃取和充气膜过程等新发展的膜过程,简要说明它们的原理、研究现状、操作特点及其应用与发展前景。     

Dry beneficiation of fine coal deploying multistage separation processes in a vibrated gas-fluidized bed

In this study, multistage separation processes were introduced into fine coal beneficiation in a vibrated gas-fluidized bed in order to improve the separation performance. The changes of coal properties, operational parameters, and density segregation characteristics during multistage separation were systematically studied. The results showed that with an increase in the separation stage, the range of density was narrowed down and the required input energy decreased. The results showed that with the same yield, the ash content of clean coal decreased from 12.53% for single separation stage to 8.91% for three separation stages, indicating a significant improvement on separation accuracy.     

Reactor modeling and recipe optimization of polyether polyol processes: Polypropylene glycol

The reactor modeling and recipe optimization of conventional semibatch polyether polyol processes, in particular for the polymerization of propylene oxide to make polypropylene glycol, is addressed. A rigorous mathematical reactor model is first developed to describe the dynamic behavior of the polymerization process based on first‐principles including the mass and population balances, reaction kinetics, and vapor‐liquid equilibria. Next, the obtained differential algebraic model is reformulated by applying a nullspace projection method that results in an equivalent dynamic system with better computational performance. The reactor model is validated against plant data by adjusting model parameters. A dynamic optimization problem is then formulated to optimize the process recipe, where the batch processing time is minimized, given a target product molecular weight as well as other requirements on product quality and process safety. The dynamic optimization problem is translated into a nonlinear program using the simultaneous collocation strategy and further solved with the interior point method to obtain the optimal control profiles. The case study result shows a good match between the model prediction and real plant data, and the optimization approach is able to significantly reduce the batch time by 47%, which indicates great potential for industrial applications. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2515–2529, 2013     

用于分布式制氢的甲烷蒸汽重整膜反应器的数值模拟

采用反应-分离集成的膜反应器进行分布式制氢,对简化工艺、降低能耗、提升技术经济性至关重要。本文采用数学模型对甲烷蒸汽重整制氢过程膜反应器进行模拟,系统分析了渗透侧操作策略、反应压力、反应温度、钯基膜性能、催化剂性能对反应器行为的影响;并以1m³/h甲烷最大程度转化为目标进行分布式制氢案例分析,详细比较膜反应器技术与“常规反应器+膜分离”工艺技术。结果表明,膜反应器在反应压力30atm（1atm=101325Pa）、反应温度500℃下操作可实现紧凑设计,比“常规反应器+膜分离”工艺技术具有明显优势,但是亟需研发更佳活性（10倍）的钯基膜和催化剂以实现显著的过程强化。模拟结果可为不同规模分布式制氢膜反应器的操作与设计及进一步的性能强化提供指导。     

An overview of the mathematical modelling of liquid membrane separation processes in hollow fibre contactors

Liquid membranes have traditionally been employed for liquid/liquid mass transfer and have found applications in industrial, biomedical and analytical fields as well as in hydrometallurgical processes, wastewater treatment and remediation of polluted groundwater. However, in spite of the known advantages of liquid membranes, there are few examples of industrial application. The development of reliable mathematical models and design parameters (mass transport coefficients and equilibrium or kinetic parameters associated with the interfacial reactions) is a necessary step for design, cost estimation, process optimisation and scale‐up. This work reports an overview of the different approaches that have been proposed in the literature to the mathematical modelling of liquid membrane separation processes in hollow fibre contactors providing, at the same time, a useful guideline to characterise the mass transport phenomena and a tool for the optimal design and intensification of separation processes. Copyright © 2009 Society of Chemical Industry     

Fine-tuned,molecular-composite,organosilica membranes for highly efficient propylene/propane separation via suitable pore size

Fine-tuned, molecular-composite, organosilica membranes were fabricated via the co-condensation of organosilica precursors bis(triethoxysilyl)acetylene (BTESA) and bis(triethoxysilyl)benzene (BTESB). Fourier transform infrared and UV–vis spectra confirmed the co-condensation behaviors of BTESA and BTESB. The evolution of the network structure indicated that the incorporated BTESB decreased the membrane pore size, which was determined by a modified gas translation model according to the steric effect of the phenyl groups. The incorporation of BTESB to BTESA finely tuned the membrane structure and endowed the resultant composite membrane with improved separation properties. The BTESAB 9:1 membrane (molar ratio of BTESA/BTESB was 9:1) exhibited high C₃H₆ permeance at 4.5 × 10⁻⁸ mol m⁻² s⁻¹ Pa⁻¹ and a C₃H₆/C₃H₈ permeance ratio of 33 at 50°C. One of the most important developments of this study involved clearly defining the relationship between membrane pore size and C₃H₆/C₃H₈ separation performance for organosilica membranes in single and binary separation systems.     

Smooth penalty function method for rigorous optimization of distillation processes

Integer decisions on stage numbers and feed locations, and global optimality are still challenging for rigorous optimization of distillation processes. In the present article, we propose a smooth penalty function method to address both these problems. The proposed method is based on the relaxation of the integer decision problem into continuous nonlinear programming (NLP) problem by adopting the bypass efficiency model developed by Dowling and Biegler. A smooth penalty term (SPT) is proposed and added to the total annual cost (TAC) function to form a new objective function, namely, the smooth penalty function. Using the new objective function, the problem is initially solved with negative weight coefficients for the SPTs regarding each column section to get an optimum near the global optimum of the SPT. Then, starting from this solution, the problem is solved again iteratively by increasing the values of the weight coefficients until all the stage numbers become integers. The performance of the method is validated by an illustrating problem and in three case studies, including a reactive distillation optimization problem.     

湍流促进器对液固一体式膜反应器中膜过滤性能影响的研究

以改善液固一体式膜反应器中膜过滤性能为目的,设计了3种外置式湍流促进器进行膜过滤强化实验,考察了湍流促进器的构型、旋转速度等因素对膜通量的影响。结果表明,旋转的湍流促进器可以明显地提高膜通量,其中推进式湍流促进器的强化效果最明显;随着湍流促进器旋转速度的增加,膜通量也相应增加;采用该湍流促进器可以进行高悬浮液质量浓度的膜过滤强化实验。     

Novel operability‐based approach for process design and intensification: Application to a membrane reactor for direct methane aromatization

This article introduces a novel operability‐based approach for process design and intensification of energy systems described by nonlinear models. This approach is applied to a membrane reactor (MR) for the direct methane aromatization (DMA) conversion to benzene and hydrogen. The proposed method broadens the scope of the traditional path of the operability approaches for design and control, mainly oriented to obtain the achievable output set (AOS) from the available input set, and compare the computed AOS to a desired output set. In particular, an optimization algorithm based on nonlinear programming tools is formulated for the calculation of the desired input set that is feasible considering process constraints and intensification targets. Results on the application of the operability method as a tool for process intensification show reduction of the DMA‐MR footprint (≈77% reactor volume and 80% membrane area reduction) for an equivalent level of performance, when compared to the base case. This case study indicates that the novel approach can be a powerful tool for process intensification of membrane reactors and other complex chemical processes. © 2016 American Institute of Chemical Engineers AIChE J, 63: 975–983, 2017