The concept of process intensification (PI) has absorbed diverse definitions and stays true to the mission-"do more with less", which is an approach purposed by chemical engineers to solve the global energy & environment problems. To date, the focus of PI has been on processes mainly involving vapor/liquid systems. Based on the fundamental principles of vapor-liquid mass transfer process like distillation and absorption, there are three strategies to intensify interphase mass transfer:enhancing the overall driving force, improving the mass transfer coefficient and enlarging the vapor-liquid interfacial area. More specifically, this article herein provides an overview of various technologies to strengthen the vapor-liquid mass transfer, including application of external fields, addition of third substances, micro-chemical technology and usage of solid foam, with the objective to contribute to the future developments and potential applications of PI in scientific research and industrial sectors.

Extractive distillation (ED) is one of the most promising approaches for the separation of the azeotropic or closeboiling mixtures in the chemical industry. The purpose of this paper is to provide a broad overview of the recent development of key aspects in the ED process involving conceptual design, solvent selection, and separation strategies. To obtain the minimum entrainer feed flow rate and reflux ratio for the ED process, the conceptual design of azeotropic mixture separation based on a topological analysis via thermodynamic feasibility insights involving residue curve maps, univolatility lines, and unidistribution curves is presented. The method is applicable to arbitrary multicomponent mixtures and allows direct screening of design alternatives. The determination of a suitable solvent is one of the key steps to ensure an effective and economical ED process. Candidate entrainers can be obtained from heuristics or literature studies while computer aided molecular design (CAMD) has superiority in efficiency and reliability. To achieve optimized extractive distillation systems, a brief review of evaluation method for both entrainer design and selection through CAMD is presented. Extractive distillation can be operated either in continuous extractive distillation (CED) or batch extractive distillation (BED), and both modes have been well-studied depending on the advantages in flexibility and low capital costs. To improve the energy efficiency, several configurations and technological alternatives can be used for both CED and BED depending on strategies and main azeotropic feeds. The challenge and chance of the further ED development involving screening the best potential solvents and exploring the energy-intensive separation strategies are discussed aiming at promoting the industrial application of this environmentally friendly separation technique.

Recent decades witnessed the significant progress made in the research field of 2D molecular sieve membranes. In comparison with their 3D counterparts, 2D molecular sieve membranes possessed several unique advantages like significantly reduced membrane thickness (one atom thick in theory) and diversified molecular sieving mechanisms (in-plane pores within nanosheets & interlayer galleries between nanosheets). M. Tsapatsis first carried out pioneering work on fabrication of lamellar ZSM-5 membrane. Since then, diverse 2D materials typically including graphene oxides (GOs) have been fabricated into membranes showing promising prospects in energy-efficient gas separation, pervaporation, desalination and nanofiltration. In addition to GOs, other emerging 2D materials, including 2D zeolites, 2D metal-organic frameworks (MOFs), 2D covalent-organic frameworks (COFs), layered double hydroxides (LDHs), transition metal dichalcogenides (TMDCs), MXenes (typically Ti₃C₂T_X), graphitic carbon nitrides (typically g-C₃N₄), hexagonal boron nitride (h-BN) and montmorillonites (MT) are showing intriguing performance in membrane-based separation process. This article summarized the most recent developments in the field of 2D molecular sieve membranes aside from GOs with particular emphasis on their structure-performance relationship and application prospects in industrial separation.

The energy consumption of distillation operation determines the amount of energy consumption throughout the chemical separation process. A heat integrated distillation column (HIDiC) could greatly reduce the irreversibility of the distillation process, so it gradually becomes a research hotspot. There are two major techniques for heat integration in HIDiC:internally and externally. This review paper describes the major research aspects of an internally heat integrated distillation column (IHIDiC), including the heat transfer models, various design structures (including the two-column HIDiC, Concentric HIDiC, Shell and tube HIDiC, Plate-fin HIDiC and the Super HIDiC, etc.), experimental research, simulation and optimization, process control research, as well as industrial plants and potential industrial applications. Among them, the heat transfer performance of various structures was analyzed of the various design structures based on experimental research, the effects of different factors (including relative volatility, reflux ratio, compression ratio, etc.) on HIDiC energy consumption or TAC is summarized in the simulation part. The calculation methods of the overall heat transfer coefficient and heat transfer models are summarized. The various optimization algorithms and optimization results of simplified HIDiC are summarized in the optimization part. The research status and the key technical issues in various aspects of HIDiC are summarized in this paper. In order to meet the requirements of industrial energy efficiency, the selection of multi-component separation distillation configurations needs to be considered more diversified, and internal complex coupling relationship of HIDiC needs to be further studied.

Oil and organic solvent contamination, derived from oil spills and organic solvent leakage, has been recognized as one of the major environmental issues imposing a serious threat to both human and ecosystem health. Among the various presented technologies applied for oil/water separation, oil absorption process has been explored widely and offers satisfactory results especially with surface modified oil-absorbing material and/or hybrid absorbents. In this review, we summarize the recent research activities involved in the designing strategies of oil-absorbing absorbents and their application in oil absorption. Then, an extensive list of various oil-absorbing materials from literature, including polymer materials, porous inorganic materials and biomass materials, has been compiled and the oil adsorption capacities toward various types of oils and organic solvents as available in the literature are presented along with highlighting and discussing the various factors involved in the designing of oil-absorbing absorbents tested so far for oil/water separation. Finally, some future trends and perspectives in oil-absorbing material are outlined.

Recovering alcohols from dilute fermentation broth is an emergent task in bio-fuel production process. Since they are primary planned for fuels, energy required to separate these alcohols should be considered in evaluating the potential of a separation technology. A membrane-based process, pervaporation, is of special interest because of its environmental friendliness and easy integrating character. This review probes into the fundamentals of pervaporation especially in terms of the heat required for evaporation. Meanwhile, the separation data of the most representative alcohol-selective pervaporation membranes reported in the literatures are collected and compared with the vapor-liquid equilibrium curve, which represents the distillation selectivity. They include:inorganic membranes, silicon rubber based membranes, Mixed Matrix Membranes and some other special materials. By doing so, the status of alcohol recovery via pervaporation would be more clear for researchers. For ethanol recovery, it is selectivity rather than flux that is in urgent need of solution. While for butanol recovery, membranes with satisfactory selectivity have been developed, increasing the separation capacity would be more pressing.

Reactive distillation (RD) process is an innovative hybrid process combining reaction with distillation, which has recently come into sharp focus as a successful case of process intensification. Considered as the most representative case of process intensification, it has been applied for many productions, especially for production of ester compounds. However, such problems existing in the RD system for ester productions are still hard to solve, as the removal of the water which comes from the esterification, and the separation of the azeotropes of ester-alcohol (-water). Many methods have been studying on the process to solve the problems resulting in further intensification and energy saving. In this paper, azeotropic-reactive distillation or entrainer enhanced reactive distillation (ERD) process, reactive extractive distillation (RED) process, the method of co-production in RD process, pressure-swing reactive distillation (PSRD) process, reactive distillation-pervaporation coupled process (RD-PV), are introduced to solve the problems above, so the product(s) can be separated efficiently and the chemical equilibrium can be shifted. Dividing-wall column (DWC) structure and novel methods of loading catalyst are also introduced as the measures to intensify the process and save energy.

Magnetically responsive porous materials possess unique properties in adsorption processes such as magneticinduced separation and heat generation in alternating magnetic fields, which greatly facilitates recycling procedures, favors long-term operation, and improves desorption rate, making conventional adsorption processes highly efficient. With increasing interest in magnetic adsorbents, great progress has been made in designing and understanding of magnetically responsive porous materials varying from monoliths to nanoscale particles used for adsorption including oil uptake, removal of hazardous substances from water, deep desulfurization of fuels, and CO₂ capture in the past few years. Therefore, a review summarizing the advanced strategies of synthesizing these magnetically responsive adsorbents and the utilization of their magnetism in practical applications is highly desired. In this review, we give a comprehensive overview of this emerging field, highlighting the strategies of exquisitely incorporating magnetism to porous materials and subtly exploiting their magnetic responsiveness. Further innovations for fabricating or utilizing magnetic adsorbents are expected to be fueled. The potential opportunities and challenges are also discussed.

There would be strong product inhibition on ethanol fermentation process if ethanol is not removed in situ from broth. PDMS membrane pervaporation coupled with fermentation is a promising process for efficient bioethanol production since ethanol inhibition is relieved or eliminated. From the perspective of process operation, membrane separation performance, ethanol fermentation performance and the subsequent processing on membrane downstream are the three key issues. This review aims at contributing a comprehensive overview on the operation performance of the integrated process. The state-of-the-art of the three key issues related to the operation performance is focused. Finally, the tentative perspective on the possible future prospects of the integrated process is briefly presented.

Membrane separation has become an important technology to deal with the global water crisis. The polymerbased membrane technology is currently in the forefront of water purification and desalination but is plagued with some bottlenecks. Laminated graphene oxide (GO) membranes exhibit excellent advantages in water purification and desalination due to the single atomic layer structure, hydrophilic property, rich oxygen-containing groups for modification, mechanical and chemical robust, anti-fouling properties, facile and large-scale production, etc. Thus the GO-based membrane technology is believed to offer huge opportunities for efficient and practical water treatment. This review systematically summarizes the current progress on the water flux and selectivity intensification, stability improvement, anti-fouling and anti-biofouling ability enhancement by structural control and modification. To improve the performance of the laminated GO membrane, interlayer spacing tunability and surface modification are mainly used to enhance its water flux and selectivity. It is found that the stability and biofouling also block the service life of the GO membrane. The crosslinking method is found to effectively solve the stability of GO membrane in aqueous environment. Introducing nanoparticles is a widely used method to improve the membrane biofouling ability. Overall, we believe that this review could provide benefit to researchers in the area of GO-based membrane technology for water treatment.

The traditional gas purification techniques such as wet gas desulfurization, with their advantages of large-scale implementation and maturity, have still been widely used. However, the main drawback of these techniques is the low transfer efficiency, which normally needs towers as tall as tens of meters to remove the pollutants. Therefore, new technologies which could enhance the mass transfer efficiency and are less energy-intensive are highly desirable. As a process intensification technology, high-gravity technology, which is carried out in a rotating packed bed (RPB), has recently demonstrated great potential for industrial applications due to its high mass transfer efficiency, energy-saving, and smaller volume. This consequently provides higher efficiency in toxic gas removal, and can significantly reduce the investment and operation costs. In this review, the mechanism, characteristics, recent developments, and the industry applications of high-gravity technologies in gas purifications, such as hydrogen sulfide, nitrogen oxide, carbon dioxide, sulfur dioxide, volatile organic compounds and nanoparticle removal are discussed, most of the demonstration projects and practical application examples in gas purification come from China. The perspective and prospective of this technology in gas purification and other fields are also briefly discussed.

Catalytic membrane, a novel membrane separation technology that combines catalysis and separation, exhibits significant potential in gas purification such as formaldehyde, toluene and nitrogen oxides (NO_x). The catalytic membrane can remove solid particles through membrane separation and degrade gaseous pollutants to clean gas via a catalytic reaction to achieve green emissions. In this review, we discussed the recent developments of catalytic membranes from two aspects:preparation of catalytic membrane and its application in gas cleaning. Catalytic membranes are divided into organic catalytic membranes and inorganic catalytic membranes depending on the substrate materials. The organic catalytic membranes which are used for low temperature operation (less than 300℃) are prepared by modifying the polymers or doping catalytic components into the polymers through coating, grafting, or in situ growth of catalysts on polymeric membrane. Inorganic catalytic membranes are used at higher temperature (higher than 500℃). The catalyst and inorganic membrane can be integrated through conventional deposition methods, such as chemical (physical) vapor deposition and wet chemical deposition. The application progress of catalytic membrane is focused on purifying indoor air and industrial exhaust to remove formaldehyde, toluene, NO_x and PM2.5, which are also summarized. Perspectives on the future developments of the catalytic membranes are provided in terms of material manufacturing and process optimization.

In modern chemical engineering processes, solid interface involvement is the most important component of process intensification techniques, such as nanoporous membrane separation and heterogeneous catalysis. The fundamental mechanism underlying interfacial transport remains incompletely understood given the complexity of heterogeneous interfacial molecular interactions and the high nonideality of the fluid involved. Thus, understanding the effects of interface-induced fluid microstructures on flow resistance is the first step in further understanding interfacial transport. Molecular simulation has become an indispensable method for the investigation of fluid microstructure and flow resistance. Here, we reviewed the recent research progress of our group and the latest relevant works to elucidate the contribution of interface-induced fluid microstructures to flow resistance. We specifically focused on water, ionic aqueous solutions, and alcohol-water mixtures given the ubiquity of these fluid systems in modern chemical engineering processes. We discussed the effects of the interfaceinduced hydrogen bond networks of water molecules, the ionic hydration of ionic aqueous solutions, and the spatial distributions of alcohol and alcohol-water mixtures on flow resistance on the basis of the distinctive characteristics of different fluid systems.

Caking of products is a common and undesired phenomenon in food, chemical, pharmaceutical, and fertilizer industries which leads to extra cost and irregular quality. In general, caking processes could be identified as amorphous caking or humidity caking. In this review, history of studying caking, formation, methods, and prospects of these two caking processes are summarized and discussed. The relevant studies from the 1920s to today are mentioned briefly. According to the different properties (i.e. hygrocapacity, hygrosensitivity, mechanical properties, and diffusion behavior) of amorphous powders and crystals, the conditions and mechanisms of amorphous and humidity caking are discussed. It is summarized that glass transition, moisture sorption, quantitative methods characterizing caking, accelerated caking tests, and simulation of caking behaviors are the main aspects that should be studied for a caking process. The methods for these five aspects are reviewed. Potential research points are proposed including caking of mixed particles, caking with phase transition or polymorph transition, non-homogenous caking, and simulation of caking.

With the development of manufacturing technology on the nanoscale, the precision of nano-devices is rapidly increasing with lower cost. Different from macroscale or microscale fluids, many specific phenomena and advantages are observed in nanofluidics. Devices and process involving and utilizing these phenomena play an important role in many fields in chemical engineering including separation, chemical analysis and transmission. In this article, we summarize the state-of-the-art progress in theoretical studies and manufacturing technologies on nanofluidics. Then we discuss practical applications of nanofluidics in many chemical engineering fields, especially in separation and encountering problems. Finally, we are looking forward to the future of nanofluidics and believe it will be more important in the separation process and the modern chemical industry.