Korean Journal of Chemical Engineering - Perspective Review Series

Korean Journal of Chemical Engineering selects topics of high interest and relevance and invites world-renown experts to write perspective reviews on them. We have aimed at including one to two such reviews in each issue. Below we highlight these contributions as they provide authoritative viewpoints on the status and future directions of some important topics in chemical engineering.

Recent advances in the synthesis of mesoporous materials and their application to lithium-ion batteries and hybrid supercapacitors
Eunho Lim, Jinyoung Chun, Changshin Jo & Jongkook Hwang

• Link: https://link.springer.com/article/10.1007/s11814-020-0693-0 (this opens in a new tab)
• Short Summary: The ever-growing demand for high performance energy storage systems has fueled the development of advanced electrode materials with light weight, high energy/power densities, and stable cycle life. Mesoporous materials play an important role in achieving these goals because of their unique features such as high surface area, tunable pore size, pore volume, and pore structures, as well as adjustable particle size and morphology. In this review, we summarize the recent progress in the synthesis of mesoporous materials and their applications in lithium-ion batteries (LIBs) and lithium-ion hybrid supercapacitors (Li-HSCs) over the past ten years. The block copolymer guided softtemplate route is highlighted as a simple and versatile tool for designing mesoporous materials with controlled nanoand macrostructures without complicated synthetic procedures. The structural/morphological benefits of designed mesoporous materials translate into highly improved electrochemical performance in LIBs and Li-HSCs. Finally, future challenges and perspectives on the development of mesoporous materials in energy storage devices are provided, which will be useful both in academia and in industry.

A short review on dissolved lithium polysulfide catholytes for advanced lithium-sulfur batteries
Rakesh Saroha, Jou-Hyeon Ahn & Jung Sang Cho

• Link: https://link.springer.com/article/10.1007/s11814-020-0729-5 (this opens in a new tab)
• Short Summary: This manuscript reviews systematically the feasibility of lithium–sulfur batteries based on dissolved polysulfide catholyte as an active material (Li-LiPSs) for commercial applications such as large-scale grids and EVs/HEVs, that can be realized only by optimizing battery characteristics in terms of high sulfur loading, high sulfur content, and low E/S ratio. In addition, advanced cathode substrates with a highly porous structure that can accommodate high amount of active material, tolerate large volume variations, and provide sufficient conductive channels for the efficient diffusion of lithium-ions during the charge-discharge process, are also discussed.

Porphyrinic zirconium metal-organic frameworks: Synthesis and applications for adsorption/catalysis
Kwangsun Yu, Dong-Il Won, Wan In Lee & Wha-Seung Ahn

• Link: https://link.springer.com/article/10.1007/s11814-020-0730-z (this opens in a new tab)
• Short Summary: Zr-based porphyrinic MOFs, which have isolated porphyrin units imbedded in MOFs' rigid structure, exhibit excellent textural properties and high stability. Among the porphyrin ligands, tetrakis(4-carboxyphenyl)-porphyrin (TCPP) is broadly employed, and the Zr-based porphyrinic MOFs of MOF-525, MOF-545 (also named PCN-222), PCN-221, PCN-223, PCN-224, PCN-225, and NU-902 have been synthesized using TCCP. The built-in TCPP ligand with various functionality and coordinatively unsaturated Zr clusters can be subjected to diverse pre- and post-synthesis functionalization or guest encapsulation. Aided by the excellent hydrothermal/chemical stability and high porosity, these Zr-based porphyrinic MOFs are gaining attention for applications in adsorption, sensors, heterogeneous catalysis for chemical conversions, photocatalysis, electrocatalysis, and others. This paper reviews the current status of research and development on the synthesis, characterization, functionalization, and adsorption/catalysis applications of Zr-based porphyrinic MOFs.

Recent applications of the liquid phase plasma process
Sang-Chai Kim, Young-Kwon Park & Sang-Chul Jung

• Link: https://link.springer.com/article/10.1007/s11814-020-0739-3 (this opens in a new tab)
• Short Summary: This manuscript reviews, the principle and application of plasma are briefly described, and in particular, the principle and practical application examples for plasma generated in liquid are introduced. Also, the research results of water treatment, synthesis of metal nanoparticle, synthesis of visible light-responsive photocatalyst, synthesis of energy material, and hydrogen gas production, which were tested using liquid phase plasma, were introduced. The liquid phase plasma (LPP) process has been successfully applied in various fields given that it can be easily and conveniently used, and presently it is being applied in several new fields and many possibilities for its future application are expected.

Catalytic production of hexamethylenediamine from renewable feedstocks
Jechan Lee, Younghyun Lee, Soosan Kim, Eilhann E. Kwon & Kun-Yi Andrew Lin

• Link: https://link.springer.com/article/10.1007/s11814-020-0725-9 (this opens in a new tab)
• Short Summary: Renewable biomass-derived chemicals receive considerable interest because of the potential for substituting petroleum-derived chemicals. Hexamethylenediamine is a key intermediate in manufacturing nylon 66, a synthetic polymer commonly used in daily life. This review assesses catalytic production of hexamethylenediamine from biomass-derived chemical feedstocks. The bio-based routes toward hexamethylenediamine are analyzed. Although no commercially available methods to directly transform biomass to hexamethylenediamine are present, promising and emerging chemical pathways from biomass-derived compounds to hexamethylenediamine using heterogeneous catalytic systems via combined processes have been suggested. The proposed routes for the renewable production of hexamethylenediamine are not yet fully competitive with its petrochemical production mostly because of low efficiencies and high costs. However, there should be much room for further developing the renewable bio-based routes to synthesize hexamethylenediamine; hence, commercialization of the biomass-derived nylon monomer is just a matter of time.

A review on the recent developments of ruthenium and nickel catalysts for COx-free H2 generation by ammonia decomposition
Thien An Le, Quoc Cuong Do, Youngmin Kim, Tae-Wan Kim & Ho-Jeong Chae

• Link: https://link.springer.com/article/10.1007/s11814-021-0767-7 (this opens in a new tab)
• Short Summary: Hydrogen (H2) energy is considered a viable future replacement for fossil-fuel, with little potential impact on the climate change. The current H2 economy faces storage and transport challenges, and the use of ammonia (NH3) as a COx-free source of H2 via its decomposition has recently attracted attention. Ru- and Ni-based catalysts have been predominantly studied for NH3 decomposition during the past two decades. Based on the recent developments regarding these catalysts, our review covers the fundamental concepts of NH3 decomposition (i.e., reaction mechanism and kinetics), and the recent developments regarding these catalysts with the focus on high catalytic performance at low temperatures. Major challenges in efforts to improve the efficiency of both Ru- and Ni-based systems are also introduced in this review. This review can serve as a comprehensive work for evaluating effective long-term strategies.

A review of synthesis strategies for MOF-derived single atom catalysts
Jongkook Hwang

• Link: https://link.springer.com/article/10.1007/s11814-021-0741-4 (this opens in a new tab)
• Short Summary: Single atom catalysts (SACs) have attracted great attention as promising catalysts that integrate the benefits of both heterogeneous and homogeneous catalysts. SACs exhibit unique properties that are otherwise difficult to achieve, such as high atom utilization efficiency, unprecedentedly high catalytic activity and selectivity. However, it still remains a great challenge to prepare stable SACs without particle aggregation and sintering. Among the various fabrication methods for SACs, metal-organic framework (MOF)-derived synthesis routes have shown great potential by taking advantage of MOFs’ high structural/chemical tunability, large surface area and high porosity. In this review, the synthesis strategies for MOF-derived SACs are comprehensively summarized and classified into five classes, metal node modification, ligand modification, guest encapsulation, migration and trapping, and others. The current challenges and future opportunities of MOF-derived SACs are further discussed. This review will be useful for the rational design of MOF-derived SACs for various catalytic reactions.    

Recent progress in metabolic engineering of Corynebacterium glutamicum for the production of C4, C5, and C6 chemicals
Kei-Anne Baritugo, Jina Son, Yu Jung Sohn, Hee Taek Kim, Jeong Chan Joo, Jong-il Choi & Si Jae Park

• Link: https://link.springer.com/article/10.1007/s11814-021-0788-2 (this opens in a new tab)
• Short Summary: Microbial fermentation for bio-based production of chemicals in biorefineries is currently a more sustainable and eco-friendly process as compared to traditional petroleum-based refineries. The non-pathogenic Corynebacterium glutamicum has extensively been developed and used as an industrial platform host strain for the commercial production of L-lysine and L-glutamate. Recently several strains have been developed using multiomics approaches, synthetic biology tools and metabolic engineering strategies for transforming C. glutamicum into a versatile microbial cell factory for utilization of renewable lignocellulosic biomass (cellulose, pectin, xylan) for biobased production of value-added platform chemicals with C4-C6 carbon backbone such as C4-isobutanol, 2,3-butanediol, C5-itaconic acid, 3-methyl-1-butanol, 2-methyl-1-butanol and C6-muconic acid.

Radical-driven photocatalytic transformation of organic molecules
Minsoo Kim, Gui-Min Kim, Nianfang Wang & Doh C. Lee

• Link: https://link.springer.com/article/10.1007/s11814-021-0794-4 (this opens in a new tab)
• Short Summary: Organic transformations, such as C-H arylation and the Diels-Alder reaction, typically involve molecular catalysts such as Ru- or Ir-based compounds. While the molecular catalysts record relatively high laboratory-scale efficiency, the noble metal-based molecular catalysis poses cost and recycling issues. For this reason, the field has turned its eyes to semiconductor nanoparticle photocatalysts for organic transformation. In this review, we highlight the progress in photocatalysis in the comparative context of semiconductor particles and molecular catalysts for radical-driven organic transformations. The discussion includes the classification of various reactions, according to the bond formation, the bond cleavage, and the oxidation. Furthermore, characteristics and merits of each photocatalyst are also organized.

A perspective on nonlinear model predictive control
Lorenz Theodor Biegler

• Link: https://link.springer.com/article/10.1007/s11814-021-0791-7 (this opens in a new tab)
• Short Summary: Model predictive control (MPC) is widely accepted as a generic multivariable controller with constraint handling. More recently, MPC has been extended to nonlinear model predictive control (NMPC) in order to realize high-performance control of highly nonlinear processes. In particular, NMPC allows incorporation of detailed process models (validated by off-line analysis) and also integrates with on-line optimization strategies consistent with higherlevel tasks, such as scheduling and planning. NMPC for tracking and so-called “economic” stage costs has been developed, and fundamental stability and robustness properties of NMPC have been analyzed. This perspective provides an overview of NMPC concepts and approaches, as well as the underlying optimization strategies that support the solution strategies. In addition, three challenging process case studies are presented to demonstrate the effectiveness of NMPC. 

Techno-economic and environmental feasibility of mineral carbonation technology for carbon neutrality: A Perspective
Ji Hyun Lee & Jay Hyung Lee

• Link: https://link.springer.com/article/10.1007/s11814-021-0840-2 (this opens in a new tab)
• Short Summary: This manuscript reviews potential of mineral carbonation as a general CCUS technology and the techno-economic & environmental feasibility of a representative technology, which produces sodium bicarbonate through the saline water electrolysis & carbonation steps, and examines the potential CO2 reduction derived from the application of this technology. The future implementation of mineral carbonation technology in ocean alkalinity enhancement for sequestrating atmospheric CO2 or the production of abandoned mine backfill materials are also discussed in order to deploy the technology at much larger scales for a meaningful contribution to the reduction of greenhouse gas emissions. 

Machine learning-based discovery of molecules, crystals, and composites: A perspective review
Sangwon Lee‡, Haeun Byun‡, Mujin Cheon, Jihan Kim†, and Jay Hyung Lee†

• Link: https://link.springer.com/article/10.1007/s11814-021-0869-2 (this opens in a new tab)
• Short Summary: Recent advances in artificial intelligence and machine learning have sparked significant paradigm shifts in sciences and engineering.  As such, developments in new molecules and materials can benefit significantly from this technology where structure-property relationship that connects the materials and the property space can be elucidated by the neural networks.  Various models are currently used to represent these molecules and materials and judicious selection can expedite the progress in which new materials are discovered.  Moreover, some of the optimization techniques involved in expediting this search are greatly reducing the computational cost as well as the amounts of data needed to unearth the structure property relationship.  It is expected that further advancements can not only facilitate the materials discovery process but enhance our understanding of what is being learned by the neural networks.

Recent advances in three-dimensional bioprinted nanocellulose-based hydrogel scaffolds for biomedical applications
Anam Saddique and In Woo Cheong†

• Link: https://link.springer.com/article/10.1007/s11814-021-0926-x (this opens in a new tab)
• Short Summary: Cellulose has been used in wide-range of applications due to its biocompatibility, biodegradability and sustainability. Due to its unique characteristics, high surface area and narrow size distribution, cellulosic materials tend to exhibit mechanically stable self-assembled structures that is being utilized to develop a promising biomaterials. In this manuscript, we reviews the role of cellulose based hydrogel in biomedical applications due to its biocompatibility and ability to be controllably moulded into different shapes. Furthermore, we described the emerging approaches to design and fabrication of advanced cellulose-based biomaterials (i.e., cellulose nanocrystals, cellulose nanofibrils, and bacterial nanocellulose), as well as their roles in traditional and emerging (3D bioprinting) biomedical fields, mainly in drug delivery, wound dressings, tissue engineering, and scaffold applications.

Perspective - the need and prospects for negative emission technologies - direct air capture through the lens of current sorption process development
Matthew J. Realff†, Youn Ji Min, Christopher W. Jones, and Ryan P. Lively

• Link: https://link.springer.com/article/10.1007/s11814-021-0957-3 (this opens in a new tab)
• Short Summary: We have known about the effect of CO2 on global temperatures for over a century, Arrhenius published the original hypothesis of the greenhouse effect of CO2 in 1896. Measurements of CO2 concentration on Mauna Loa, begun in the 1950’s, show we have increased our atmospheric CO2 by 50% since the industrial revolution and currently we are increasing it by over 2ppm per year. To meet the challenge of stabilizing atmospheric CO2 concentrations we must develop a sufficiently diverse portfolio of scalable energy technologies and simultaneously satisfy a more equitable global energy demand that provides a reasonable standard of living for all.
  A critical component of any strategy to manage CO2 concentrations, is a scalable negative emissions technology or NET. In this perspective we describe some of the critical challenges for sorption-based direct air capture (DAC) which shows promise as a scalable NET. Successful DAC systems will have to process huge volumes of air with minimal pressure drop but with reasonable mass transfer kinetics to deliver CO2 to sorbents that have sufficient affinity for the CO2 but not lead to high energy penalties of regeneration. Chemical engineer will provide the foundation for innovative DAC systems that manage these tradeoffs and lead to an industry that could match the scale of current fossil-based hydrocarbon processing.

Research needs targeting direct air capture of carbon dioxide: Material & process performance characteristics under realistic environmental conditions
Fanhe Kong, Guanhe Rim, MinGyu Song, Cornelia Rosu, Pranjali Priyadarshini, Ryan P. Lively, Matthew J. Realff, and Christopher W. Jones†

• Link: https://link.springer.com/article/10.1007/s11814-021-0976-0 (this opens in a new tab)
• Short Summary: The extraction of CO2 from ambient air, or direct air capture (DAC), is a crucial negative CO2 emissions technology with great potential for contributing to the mitigation of global warming and climate change.  Unlike most chemical processes, which operate under fixed conditions in an enclosed process, DAC operates outdoors under conditions that change due to variations in location, seasons, weather or time of day.  However, most research to date on materials and processes has been conducted under fixed, controlled, laboratory conditions.  This perspective discusses some of the knowledge gaps that must be filled to enable DAC to be a robust technology that is deployable all over the world.  A particular gap is the design and optimization of materials and processes that operate under cold temperatures ranging from -20 to 10 ° C.  There are many more that await exploration.

Recent progress in dehydrogenation catalysts for heterocyclic and homocyclic liquid organic hydrogen carriers
Yeongin Jo, Jinho Oh, Donghyeon Kim, Ji Hoon Park, Joon Hyun Baik & Young-Woong Suh  

• Link: https://link.springer.com/article/10.1007/s11814-021-0947-5 (this opens in a new tab)
• Short Summary: The concept of liquid organic hydrogen carriers (LOHC) is an attractive solution for H₂ storage and transportation. Among challenging tasks for practical applications, the most stringent limitations stem from the dehydrogenation reaction requiring high temperatures thermodynamically. This review highlights the state-of-the-art catalysts reported for the dehydrogenation of homocyclic and heterocyclic LOHC molecules. The dehydrogenation mechanism for these molecules consists of reactant adsorption, surface reaction, and product desorption. Reactant adsorption to active metals should occur strongly, but product adsorption would be weak for fast desorption. During the surface reaction, C–H bond cleavage proceeds well with almost no side reactions caused by cleavage of other bonds including C–C bond. Therefore, active metals of suitable adsorption strength are vital when considering their electronic and geometric effects, which is called the Sabatier principle. Aside from catalytic activity, H₂ purity (i.e., reaction selectivity) and catalyst stability should be considered for catalyst selection. From this review, readers can easily catch up a variety of endeavors for precise tuning of active metals, appropriate incorporation of promoters and metal additives, and elegant support modification, thereby enabling to design a powerful strategy to find an active and stable dehydrogenation catalyst for the realization of LOHC technology.

Emerging strategies for biomaterial-assisted cancer immunotherapy
Kye Il Joo

• Link: https://link.springer.com/article/10.1007/s11814-021-0985-z (this opens in a new tab)
• Short Summary: This manuscript provides an overview of recent developments in biomaterial-assisted cancer immunotherapy that aim to enhance the therapeutic efficacy while reducing the adverse effects. This review mainly focuses on various strategies of biomaterial-assisted cancer immunotherapy for localized, targeted, and combined treatments and then summarize the promises and challenges for integrating biomaterial-based delivery technologies into cancer immunotherapy. The number of clinical trials in immune checkpoint blockade (ICB) therapy and chimeric antigen receptor (CAR)-T cell therapy has been remarkably increasing in recent years. However, the currently available options for these treatments pose significant challenges related to immune-related adverse effects and limited therapeutic efficacy. Excellent delivery technologies by leveraging biomaterials to mitigate these limitations could potentially advance current cancer immunotherapies for a wide range of applications.

Recent progress in electrochemical reduction of CO2 into formate and C2 compounds
Wei Jyun Wang, Louis Scudiero† & Su Ha†

• Link: https://link.springer.com/article/10.1007/s11814-021-1009-8 (this opens in a new tab)
• Short Summary: Global warming and climate change enhanced by the high atmospheric CO2 concentration have been correlated to the frequency of extreme weather causing a significant amount of property damage and loss of human lives. Among current atmospheric CO2 concentration control strategies, the electrochemical reduction of CO2 (eCO2R) process is a promising technology that can utilize CO2 gas as a feedstock to produce valuable C1 and C2 compounds at room temperature. This review discusses current technological advancements of electrocatalytic materials and the design of gas diffusion electrodes that increase energy efficiency and reduce the mass transfer resistance of CO2 conversion into C1 with a focus on formate and C2 chemical compounds. A techno-economic analysis is briefly provided, and future and technical challenges of CO2 conversion at the industrial scale into formate and C2 products are also addressed.

New frontiers of quantum computing in chemical engineering
Akshay Ajagekar & Fengqi You†

• Link: https://link.springer.com/article/10.1007/s11814-021-1027-6 (this opens in a new tab)
• Short Summary: Advancements in quantum hardware and algorithms have further fueled the adoption of quantum computing (QC) into various applications ranging across fields. Owing to the sole reliance on classical computing techniques that may not scale well with the increasing size and complexity of applications, chemical engineering offers excellent potential to benefit from advantages promised with QC. This review identifies areas of application in chemical engineering that may benefit from such quantum algorithms implemented on quantum computers. Achieving speedups over classical computing with quantum algorithms implemented on current quantum devices is possible for a few specific tasks. It is imperative to identify chemical engineering problems of practical relevance that may benefit from novel quantum techniques either with current quantum computers or of the future. In this work, we review quantum algorithms that may benefit optimization and machine learning in chemical engineering with current quantum devices as well as fault-tolerant devices. This work also sets expectations for quantum computers of the future by exploring similar applications that may benefit from quantum algorithms implemented on such devices.

Energy metabolism in Chinese hamster ovary (CHO) cells: Productivity and beyond
Jong Uk Park‡, Hye-Jin Han‡, and Jong Youn Baik†

• Link: https://link.springer.com/article/10.1007/s11814-022-1062-y (this opens in a new tab)
• Short Summary: Chinese hamster ovary (CHO) cell lines have been widely used to produce recombinant proteins. Whilethe biosynthesis of recombinant proteins is energy-intensive, CHO cells exhibit inefficient metabolism, characterized byrapid conversion of glucose to lactate, possibly leading to lower cell growth and productivity of therapeutic proteins.Therefore, it is important to understand and engineer cellular metabolism to increase recombinant protein production.In this review, cellular energy metabolism of CHO cells with respect to protein synthesis is overviewed. Then, geneticand process engineering approaches to enhance metabolic efficiency are described, resulting in the improvement of cellculture performance. Finally, recent modeling technologies for understanding and predicting cellular metabolic behaviorsare reviewed. These efforts will aid to further advance the biomanufacturing of therapeutic proteins.

Epigenome editing and epigenetic gene regulation in disease phenotypes
Gaochen Jin and Bomyi Lim†

• Link: https://link.springer.com/article/10.1007/s11814-022-1076-5 (this opens in a new tab)
• Short Summary: An increasing number of studies have emphasized the role of biochemical changes in proper gene regulation. Epigenetic modifications, including DNA methylation and post-translational modifications on histones via methylation, acetylation, phosphorylation, etc., do not alter DNA sequences. Yet, disruptions of the epigenome can still induce gene malfunction, aberrant cell differentiation, proliferation, and apoptosis, resulting in various diseases such as cancer, neurological disorders, and autoimmune diseases. This review highlights recently developed engineering techniques to systematically perturb the epigenome, in an effort to provide potential therapeutic methods for associated diseases.

A review of formic acid decomposition routes on transition metals for its potential use as a liquid H2 carrier
Sierra Schlussel and Stephanie Kwon†

• Link: https://link.springer.com/article/10.1007/s11814-022-1276-z (this opens in a new tab)
• Short Summary: Formic acid (HCOOH) has emerged as a promising H2 energy carrier due to its reasonable gravimetric and volumetric H2 densities, low toxicity, low flammability, and ease of handling. The utilization of HCOOH requires a catalytic system to selectively dehydrogenate HCOOH to CO2 and H2 products at low temperatures without forming any CO by-products, which act as a poison in fuel cell applications. This review summarizes the recent progress in understanding HCOOH decomposition pathways and surface chemistry on transition metals, including Cu, Pt, Pd, and Au. In doing so, this review provides the current catalyst design strategies for HCOOH dehydrogenation to facilitate the future development of catalytic processes for H2 storage and utilization.

Objectives, challenges, and prospects of batch processes: Arising from injection molding applications
Yuanqiang Zhou, Zhixing Cao, Jingyi Lu, Chunhui Zhao, Dewei Li & Furong Gao†

• Link: https://link.springer.com/article/10.1007/s11814-022-1294-x (this opens in a new tab)
• Short Summary: Batch process is preferred for the manufacturing of specialty chemicals or other high value-added products. Due to the differences between continuous process and batch process, the modeling, monitoring, control, and optimization methods must be developed according to the batch process nature. By using thermoplastic injection molding, a process converting plastic granules into various molded parts, this review paper emphasizes the batch process nature of injection molding and identifies three main objectives for future development: i) greater efficiency, ii) greater profitability, and iii) sustainability. From the perspective of system engineering, this paper discusses four primary challenges for batch process manufacturing: 1) Model development in face of product changes, 2) Control strategies in face of dynamic changes, 3) Data analysis and process monitoring, and 4) Safety assurance and quality improvement. Finally, some promising technologies, including (a) machine learning methods, (b) big data analytics, (c) the internet of things, and (d) digital twin technology, has been briefly introduced, particularly in relation to injection molding, which may break existing capability limits in the near future and revolutionize batch process automation.