Recent advances in cellulosic membranes for gas separation and pervaporation

Cellulose acetate membranes have been used commercially for many gas separation applications in recent years. Advances have been made in understanding their behaviour in the presence of various vapours and under severe operating conditions, for example at very high carbon dioxide and hydrogen sulphide partial pressures. In addition, a new membrane module design has been developed for use in high recovery systems and at high gas flow rates. Extension of cellulose acetate gas separation membrane technology into the pervaporation field has resulted in a new application related to the production of methyl t-butyl ether (MtBE). In this case the membrane is used to remove methanol from MtBE and hydrocarbons to increase the reaction yield.     

Recent advances on mixed matrix membranes for CO2 separation

Recent advances on mixed matrix membrane for CO2 separation are reviewed in this paper. To improve CO2 separation performance of polymer membranes, mixedmatrixmembranes (MMMs) are developed. The concept of MMM is illustrated distinctly. Suitable polymer and inorganic or organic fillers for MMMs are summarized.Possible interface morphologies between polymer and filler, and the effect of interface morphologies on gas transport properties of MMMs are summarized. The methods to improve compatibility between polymer and filler are introduced. There are eightmethods including silane coupling, Grignard treatment, incorporation of additive,grafting, in situ polymerization, polydopamine coating, particle fusion approach and polymer functionalization. To achieve higher productivity for industrial application,mixed matrix composite membranes are developed. The recent development on hollow fiber and flat mixedmatrix composite membrane is reviewed in detail. Last, the future trend of MMM is forecasted.     

石墨烯基材料在CO2分离膜领域的研究进展

节能高效的CO₂分离技术的开发具有重要的现实及长远意义,膜法CO₂分离在该领域备受关注,具有优异传质特性的新型分离膜材料对膜分离过程有决定性的影响。近年来,石墨烯及其衍生材料因独特的单原子层厚度、亚纳米级别的孔道结构以及优异的机械、化学和热稳定性,成为气体分离膜领域的研究热点,膜的加工难度、技术成本、大面积制备、工作稳定性等问题是限制其实际应用的关键因素。石墨烯基CO₂分离膜主要有三种形式：纳米孔石墨烯膜、层状结构氧化石墨烯膜、基于石墨烯及其衍生材料的混合基质膜。本文综述了石墨烯基CO₂分离膜领域的突破性研究进展,重点介绍了气体的跨膜传质机理和膜的构性关系,总结了膜性能的优化思路和原理,梳理了石墨烯基CO₂分离膜发展面临的挑战,提出了潜在的研究方向。分析表明,进行系统的理论研究,采用先进的表征手段,以建立膜构性关系的理论模型,指导膜结构设计是未来研究的重点。此外,进一步降低膜加工成本,充分研究膜在实际工作环境中的稳定性也至关重要。     

Polymer membranes for high temperature proton exchange membrane fuel cell: Recent advances and challenges

Proton-exchange membrane fuel cells (PEMFCs) are considered to be a promising technology for efficient power generation in the 21st century. Currently, high temperature proton exchange membrane fuel cells (HT-PEMFC) offer several advantages, such as high proton conductivity, low permeability to fuel, low electro-osmotic drag coefficient, good chemical/thermal stability, good mechanical properties and low cost. Owing to the aforementioned features, high temperature proton exchange membrane fuel cells have been utilized more widely compared to low temperature proton exchange membrane fuel cells, which contain certain limitations, such as carbon monoxide poisoning, heat management, water leaching, etc. This review examines the inspiration for HT-PEMFC development, the technological constraints, and recent advances. Various classes of polymers, such as sulfonated hydrocarbon polymers, acid-base polymers and blend polymers, have been analyzed to fulfill the key requirements of high temperature operation of proton exchange membrane fuel cells (PEMFC). The effect of inorganic additives on the performance of HT-PEMFC has been scrutinized. A detailed discussion of the synthesis of polymer, membrane fabrication and physicochemical characterizations is provided. The proton conductivity and cell performance of the polymeric membranes can be improved by high temperature treatment. The mechanical and water retention properties have shown significant improvement., However, there is scope for further research from the perspective of achieving improvements in certain areas, such as optimizing the thermal and chemical stability of the polymer, acid management, and the integral interface between the electrode and membrane.     

有机框架膜在气体分离中的研究进展

高渗透性、高选择性和高稳定性的膜材料是决定膜分离过程效率的关键。有机框架膜（organic framework membranes,OFMs）具有孔隙率高、孔道长程有序、易于官能化修饰、稳定性强等特点,在气体膜分离领域具有重要发展前景。综述了有机框架膜的化学组成、结构特征、制备方法及其在二氧化碳捕集与分离、烯烃/烷烃分离及稀有气体分离等气体分离过程中的应用。最后,对有机框架膜在气体分离领域的机遇和挑战进行了总结,并对其发展方向进行了展望。     

Targetting membranes for gas separation

This paper describes a method of setting targets for the development of new membranes, such that the resulting membrane separator will be economically viable in a particular commercial process. The example used is the separation of carbon monoxide and hydrogen for the production of acetic acid. It is shown by an economic evaluation of the complete process, that the total cost of manufacturing acetic acid depends on the permeability and selectivity of the membrane. Costs upstream and downstream of the membrane separator are considered. The same production cost may be achieved by many different combinations of selectivity and permeability, and thus iso-cost lines may be generated which provide guidance for the development of new membranes.     

A review of technological advances and open challenges for oil and gas drilling systems engineering

The ever-increasing quest to identify, secure, access, and operate oil and gas fields is continuously expanding to the far corners of the planet, facing extreme conditions toward exploring, securing, and deriving maximum fluid benefits from established and unconventional fossil fuel sources alike: to this end, the unprecedented geological, climatic, technical, and operational challenges have necessitated the development of revolutionary drilling and production methods. This review paper focuses on a technological field of great importance and formidable technical complexity—that of well drilling for fossil fuel production. A vastly expanding body of literature addresses design and operation problems with remarkable success: what is even more interesting is that many recent contributions rely on multidisciplinary approaches and reusable Process Systems Engineering (PSE) methodologies—a drastic departure from ad hoc/one-use tools and methods of the past. The specific goals of this review are to first review the state-of-art in active fields within drilling engineering and explore currently pressing technical problems, which are in dire need or have recently found, PSE- and/or computational fluid dynamics-relevant solutions. Then, we illustrate the methodological versatility of novel PSE-based approaches for optimization and control, with an emphasis on contemporary problems. Finally, we highlight current challenges and opportunities for truly innovative research contributions, which require the combination of best-in-class methodological and software elements in order to deliver applicable solutions of industrial importance.     

Carbon membranes for gas separation: Developmental studies

Carbon membranes with 0.2 and 1.0 μm pore sizes are commercially available for liquid microfiltration applications. These membranes may be modified for gas separation applications by providing a gas separation layer with pores in the 1 to 10 nm range. With such pores, gases are separated by Knudsen diffusion with an individual gas species permeation rate inversely proportional to the ratio of the square root of the molecular weight of the permeating species. This paper describes some of the techniques used for depositing a suitable layer starting with various organic polymeric precursors. The in situ polymerization technique was found to be the most promising, and pure component tests with membrane samples prepared with this technique indicated Knudsen diffusion behaviour. The gas separation factors obtained by mixed-gas permeation tests were found to depend strongly on gas temperature and pressure indicating significant viscous flow at high-pressure conditions.     

Bioconversion of CO2 and potential of gas fermentation for mainstream applications: Critical advances and engineering challenges

The undesirable consequences of climate change are attributed to the ever-increasing emissions of greenhouse gases, especially carbon dioxide. For the sustainable development of human society, there is an urgent need to develop novel techniques for efficient conversion and utilization of carbon dioxide. Hence, carbon capture and storage, artificial bioconversion of carbon dioxide are topics of great interest for current researchers across the globe. Here, we elucidate the different techniques of carbon fixation, which fall under the broad categories of natural fixation pathways, thermo-catalytic conversion techniques, and synthetic carbon fixation pathways. Based on a comparative analysis, gas fermentation is a promising method for the microbial conversion of CO₂-containing gases into fuels and chemicals. However, for mainstream applications, in-depth reviews of different reactor configurations and the various engineering aspects related to process development are still lacking. We have analyzed the published literature relating to artificial bioconversion of carbon dioxide and focused on the factors like equipment selection and reactor design that can assist in scale-up of gas fermentation technology. The review provides an in-depth understanding of engineering aspects related to stirred tank and bubble column reactors, focusing on the technical design parameters and discussing the conditions for optimal operation and performance during commercial gas fermentation processes.     

高性能气体分离聚苯胺膜

系统论述了聚苯胺自支撑膜和复合膜对气体的分离性能。聚苯胺自支撑膜、聚苯胺 /尼龙、聚苯胺 /氧化铝复合膜经去掺杂尤其是二次掺杂后 ,气体分离系数会显著提高 ,而透气系数略有提高。二次掺杂态聚苯胺自支撑膜和复合膜都具有极高的氧氮分离性能 ,已超过了一般聚合物材料的上限 ,最优异的聚苯胺膜的氧氮选择分离系数可达 30 ,它在包括有高选择性能膜材料聚酰亚胺、聚吡咙、聚三唑等在内的所有聚合物膜中排行第一 ,对空气分离显示出极大优势。预计聚苯胺复合膜及纳米膜在医疗保健等领域具有很大应用潜力     

Opportunities and challenges for a Golden Age of chemical engineering

Chemical engineering is entering a new Golden Age of practice, thought, and impact, accompanied by great new opportunities and challenges. Five aspects mark this development: a new abundance of hydrocarbons; the evolution of biology into a molecular science; the ubiquity of powerful computational tools; the trend in manufacturing to be more process-oriented; and the systems approach that is part of ChE education from its first stages. There are important technical challenges, including technology creation and environmental impact, but just as important are new appreciation for and attention to challenges that require societal dialogues about complexity, uncertainty, and evolving and sometimes contradictory requirements. Crucial to all these impacts is enhancing the identity of what the profession is. That must be based on recognizing that the core of chemical engineering is applying molecular sciences to create value and advance the quality of life.     

Recent advances on graphene microstructure engineering for propellant-related applications

As a special polymeric composite and military-strategic material, composite solid propellant has attracted extensive attention and efforts to improve its performances. Graphene been regarded as an ideal material to enhance the performances of propellants, because of its excellent physical and chemical properties, such as ultra-strong strength, large specific surface area, remarkable thermal conductivity, and phenomenal electrical performance. Moreover, the microstructure engineering based on graphene has been demonstrated to reveal effective influences on the composites. Recently, many new advances have been developed in microstructure engineering of graphene for propellant-related applications. In this article, we first present an overview of the main synthesis methods of graphene. Subsequently, these new advances are reviewed, discussed, and summarized carefully. Finally, the application prospects of microstructure engineering of graphene in the propellant field are proposed.     

Recent advances in bioreactor engineering

A bioreactor is the core of biological processes. To design an appropriate bioreactor system for a particular bioprocess, intensive studies on the biological system, such as cell growth, metabolism, genetic manipulation, and protein or other product expression are needed to understand the cells’ requirement on their physical and chemical environments. It is also necessary to control and optimize the bioreactor environment via operating variables in order to favor the desired functions of cells and achieve cost-effective large-scale manufacture. This article briefly describes fundamental design principles and new types of bioreactors such as centrifugal impeller and wave bioreactors. Bioreactor operation factors and modes including mixing, oxygen supply, shear force, fed-batch, and perfusion cultures are discussed. The trends in bioreactor engineering are also briefly shown.     

Recent advances on the membrane processes for CO2 separation

Membrane separation technology has popularized rapidly and attracts much interest in gas industry as a promising sort of newly chemical separation unit operation. In this paper, recent advances on membrane processes for CO₂ separation are reviewed. The researches indicate that the optimization of operating process designs could improve the separation performance, reduce the energy consumption and decrease the cost of membrane separation systems. With the improvement of membrane materials recently, membrane processes are beginning to be competitive enough for CO₂ separation, especially for post-combustion CO₂ capture, biogas upgrading and natural gas carbon dioxide removal, compared with the traditional separation methods. We summarize the needs and most promising research directions for membrane processes for CO₂ separation in current and future membrane applications. As the time goes by, novel membrane materials developed according to the requirement proposed by process optimization with increased selectivity and/or permeance will accelerate the industrialization of membrane process in the near future. Based on the data collected in a pilot scale test, more effort could be made on the optimization of membrane separation processes. This work would open up a new horizon for CO₂ separation/Capture on Carbon Capture Utilization and Storage (CCUS).     

Rigid and microporous polymers for gas separation membranes

Microporous polymers are a class of microporous materials with high free volume elements and large surface areas. Microporous polymers have received much attention for various applications in gas separation, gas storage, and for clean energy resources due to their easy processability for mass production, as well as microporosity for high performance. This review describes recent research trends of microporous polymers in various energy related applications, especially for gas separations and gas storages. The new classes of microporous polymers, so-called thermally rearranged (TR) polymers and polymers of intrinsic microporosity (PIMs), have been developed by enhancing polymer rigidity to improve microporosity with sufficient free volume sizes. Their rigidity improves separation performance and efficiency with extraordinary gas permeability. Moreover, their solubility in organic solvents allows them to have potential use in large-scale industrial applications.     

Polymer nanocomposites from modified clays: Recent advances and challenges

Since the end of the last century, the discovery of polymer nanocomposites and their ever-expanding use in various applications has been the result of continuous developments in polymer science and nanotechnology. In that regard, progress in developments on the use of modified natural and synthetic clays for designing polymer nanocomposites is presented herein. The modified clays used in composite preparation include natural clays such as montmorrilonite, hectorite, sepiolite, laponite, saponite, rectorite, bentonite, vermiculite, biedellite, kaolinite, and chlorite, as well as synthetic clays including various layered double hydroxides, synthetic montmorrilonite, hectorite, etc. The preparation, structure and properties of polymer nanocomposites using the modified clays are discussed. Even at a low loading, these composites are endowed with remarkably enhanced mechanical, thermal, dynamic mechanical, adhesion and barrier properties, flame retardancy, etc. The properties of the nanocomposites depend significantly on the chemistry of polymer matrices, nature of clays, their modification and the preparation methods. The uniform dispersion of clays in polymer matrices is a general prerequisite for achieving improved mechanical and physical characteristics. Various theories and models used to design polymer/clay nanocomposites have also been highlighted. A synopsis of the applications of these advanced, high-performance polymer nanocomposites is presented, pointing out gaps to motivate potential research in this field.     

Polyacetylene derivatives as membranes for gas separation

In this paper the use of polyacetylene derivatives as membranes for gas separation is investigated. The role of additives is discussed. Permeability measurements, X-ray, d.t.a. and t.g.a. characterizations are carried out.     

Highly selective polymeric membranes for gas separation

Polymeric membranes have gained an important place in chemical technology and are used in a broad range of applications. The key property that is exploited is the ability of a membrane to control the permeation rate of a chemical species through the membrane. The goal is to allow one component of a mixture to permeate the membrane freely, while hindering permeation of other component. To accomplish this, we proposed a novel concept of a (universal) ‘organic molecular sieve’ and experimentally proved its possibility by showing that organic polymer molecules at the interface between the permeable phase and the impermeable phase play the role of molecular sieves. This resulted in a significantly improved selectivity in gas separation, in fact going over the so-called ‘upper-bound’ sought for the past 30 years by many researchers but without much success. Since, this is not size selective like an inorganic molecular sieve but diffusion selective (the compatibilizer works like a molecular sieve to separate one gas molecules from the other), it can be used for the preparation of polymeric membranes for separation of any gas molecules pair. Because of polymer processability, this method is quite promising for the continuous mass production of polymeric membranes for real applications, especially when the polymers are insoluble to common solvents so that solution based techniques are hard to apply. This strategy can be applicable to various separation processes of many chemicals and gases.