Chemical Engineering Research Articles

Electrochemical impedance spectroscopy (EIS12–2023): Foreword

In this foreword, the Symposium on Electrochemical Impedance Spectroscopy (EIS12–2023), which was held by Beijing University of Chemical Technology and Tsinghua University in Beijing from July 2 to 7, 2023, was in details introduced. It was the first time that EIS12 -2023 took place in China since it was established in France 1989. At the opening ceremony, a film illustrating the history of the conference on electrochemical impedance spectroscopy was also shown. Meanwhile, the Claude Awards were given to Prof. Annick Hubin from Vrije Universiteit Brussel in Belgium and Prof. Jianqing Zhang from Zhejiang University in China. During EIS12–2023, 15 plenary talks, 21 invited talks in the corrosion session and in memory of Prof. Chunan Cao, 10 keynote talks in the energy and measurement sessions were presented. There were also 51 posters and 54 talks. Xingyue Yong from Beijing University of Chemical Technology and Assistant Professor Burak Ulgut from Bilkent University, Turkey were elected as new members of the Technical Committee of International Electrochemical Impedance Spectroscopy Additionally, it was decided that the 13th International Symposium on Electrochemical Impedance Spectroscopy will be held in Brazil in November 2026. EIS12–2023 organizing committee sincerely thanks everyone for supporting EIS12–2023 and express its great gratitude to Prof. Sotiris Sotiropoulos, the Special Issues Editor of Electrochimica Acta, for his contribution in making this Special Issue possible.

Generalization of the Wong-Sandler mixing rule to a generic cubic equation of state: Examples of use for systems of industrial interest (Hydrogen, CCUS, refrigeration)

Cubic equations of state (EoS) remain the most widely used models in chemical engineering, and their predictive capabilities are highly dependent on mixing rules (MR). Considered as one of the most accurate, Wong Sandler's (WS) MR, have been generalized in this work, to allow its use with all 2-parameter (PR, SRK, …) and 3-parameter (PT, mPT, NEOS, …) cubic EoSs. The procedure for implementing the generalized WS MR is presented and tested with PR, PT and its variants (mPT and NEOS) on vapor-liquid equilibrium (VLE) and density data on various classes of mixtures for different types of use (hydrogen, CCUS, refrigeration). The results clearly show the benefits of this type of MR, especially around the critical point and for density data without considering volume translation frequently used with PR and SRK EoS.

Incorporating ecological economics into engineering education

Engineering students require an education which facilitates the development not just of functional design of technological artefacts and processes, but they also need to be equipped to understand and engage with their wider implications and context. Consequently, as part of the formation of sustainability informed engineers, there is a clear necessity to integrate the socio-economic aspects of sustainability in order to posit technology in appropriate contextualised settings. The chemical engineering degree programme at University College Cork incorporates a strong emphasis on integrating the socio-economic dimension of sustainability within the programme. This paper focuses on ecological economics, and how it can connect with engineering and why it is important that engineering students receive a grounding in ecological economics. It outlines the content of a five-lecture series on ecological economics given to fifth-year chemical engineering students. This includes environmental aspects, such ecological limits analysis and the use of strategies, including economic, to move unsustainable natural resource use and emissions discharges to within their ecological limits. It explores social aspects and the critical barriers to transitioning to a sustainable economy, as well as the impact of ecological economics on engineering. Finally, three consecutive final year classes were surveyed to elicit their feedback on being taught ecological economics and to test the hypothesis that the inclusion of ecological economics appreciably enhances students’ ability to engage productively with sustainability and the UN Sustainable Development Goals (SDGs); a key accreditation and professional requirement for contemporary engineering graduates. Overall, most students enjoyed the material, stating that is of value to engineering students, and they provided a useful qualitative assessment of the content.

Drop breakup at reduced energy cost using a turbulent pulse –implications for improving efficiency in emulsification devices

Emulsification devices break drops by rapidly pushing them through a region of intense turbulence–a ‘turbulent pulse’. These devices are widely used in chemical engineering. However, the thermodynamic efficiency is low, and design modifications allowing more breakup at lower energy input is much in need.This study uses a combination of statistical models and direct numerical simulation coupled to high resolution interface tracking to investigate how a turbulent pulse should be designed to reach a desired breakup probability at minimum energy cost. It is concluded that breakup is not determined by the total energy input. Consequently, the energy cost of achieving a given breakup extent could be reduced by carefully tuning pulse amplitude and duration. The optimal pulse is compared to that delivered by homogenizers, revealing that the inability to dissipate turbulent kinetic energy in a sufficiently narrow region is partially responsible for the low efficiency.

Снижение экологической нагрузки на регион за счет рационального способа утилизации фторангидрита

The article considers the chemical industry technologies contaminating the environment with sulfate-calcium waste in three regions of the former Soviet Union, i.e., the Tomsk region (SHK LLC, Seversk), the Perm territory (Galopolimer JSC, Perm), and East Kazakhstan region (UMZ JSC, Ust-Kamenogorsk). The differences and similarities of technological processes of anhydrous calcium sulfate production in the above-mentioned regions have been considered. Some properties of sulfate calcium (acid fluoride) that until recently was the main environmental contaminator used in the technology of hydrogen fluoride production have been specified. The objective of the study is to provide generalized positive results obtained by the authors of the article in the field of optimization of sulfuric decomposition of fluorspar not changing the production conditions and the quality of the main product — hydrogen fluoride. As a result of the process, the solid waste of hydrogen fluoride production is transformed into a target product, i.e., a technogenic anhydrite binder that can be an alternative to Portland cement and gypsum binders in the construction industry. Therefore, acid fluoride waste is removed from the hydrogen fluoride technology, and the environmental contamination with sulfate-calcium waste is prevented. In addition, a new trend in the construction industry is set, which is the industry production of anhydrite materials and products. The list of pilot-industrial and semi-industrial tests of the production of various anhydrite products has been provided (as an image listing the fields of use of acid fluoride in the industry of construction materials). In conclusion, the amount of environmental damage caused by the acid fluoride waste has been specified. In the Ob basin of the West Siberian region, it was 270 million rubles for 2023.

An efficient and scalable melt fiber spinning system to improve enzyme-based PET recycling

Chemical recycling technologies based on hydrolase enzymes that can depolymerize PET thermoplastic are emerging, yet these approaches require the polymer to be low crystallinity to achieve high conversion. To prepare the polymer for enzymatic depolymerization, current processes rely on melting and cryomilling PET at depressed temperatures to reduce crystallinity and prevent annealing during micronization; however, these approaches require large capital investment in costly equipment, and are not easily incorporated into intermediate-scale, distributed systems. Here, we describe a melt fiber spinning system that achieves significant reduction in crystallinity for real-world PET feedstocks without the need for any active cooling, and can easily be scaled up or down as needed. Single-use water bottles and drinking cups are tested, where they are extruded, drawn and spooled as thin fibers that cool by passive heat dissipation rapidly enough to quench the polymer to low crystallinity (<10%). Additionally, we estimate the fiber spinning also increases the feedstock surface-area-to-volume ratio by up to 15-fold, which further benefits heterogenous enzyme biocatalysis. In small scale PET hydrolase enzyme incubation tests, fiber spinning increased monomer released from PET by 4-fold for drinking cups and 10-fold for water bottles compared to shredded-only controls. Finally, we also show that this system can scale to >300 gs, with the potential for much larger scales, and allows for >95% depolymerization in a larger 20 liter bioreactor run.

Discussion on plastic waste management hierarchy

Although recycling is one of the main solutions proposed in the waste hierarchy established by the Waste Framework Directive, the effective recycling of plastic packaging waste in Italy is still insufficient. Through a review of European Union and Italian legislation, recycling strategies and technological innovations, such as the use of bioplastics and chemical recycling, this work aims to help fill possible knowledge gaps and guide decisions in both, the public sector and the private sector, in the development of policies that enhance the management of plastic packaging waste. Among the results it was found that the low recycling rate of plastic packaging is in partly due to the technical and regulatory limitations that exist at European level for the growth of innovative solutions in the plastic industry. These limitations in- clude the complexity of plastic packaging waste streams and the lack of a single European Union Directive that harmonizes the laws of the Member States regarding the use of bioplastics, chemical recycling technologies and value-added products obtained.

A novel multi-objective optimization strategy based on vibrating particle system algorithm applied to chemical process design

Chemical process design is a highly interesting field within the chemical engineering community due to the numerous potential applications it offers. Traditionally, this problem involves multiple objectives and constraints related to mass, energy, and momentum balances, as well as limitations based on environmental, physical, and operating conditions. Over the past few decades, various multi-objective optimization strategies incorporating evolutionary algorithms have been proposed and tested using test cases of varying complexity. In this study, we propose a new Multi-objective Optimization Vibrating Particle System (MOVPS) algorithm. This numerical strategy extends the Vibrating Particle System Algorithm to a multi-objective context by incorporating three operators into the original algorithm: Pareto dominance, crowding distance, and a mutation strategy. To expedite the convergence process and avoid local optima, an external repository is considered. We evaluate the performance of the proposed methodology by applying it to mathematical functions (ZDT functions) and chemical process design problems. Regarding the ZDT functions, the computational cost (number of objective function evaluations and the processing time) was not increased considering the proposed methodology, as well as the values of convergence and diversity metrics are in agreement with those calculated considering other multi-objective optimization strategies. For most engineering case studies, it was possible to verify that the proposed methodology was able to obtain good estimates for the Pareto curve without increasing the computational cost. However, for the industrial styrene reactor problem it was possible to improve the Pareto curve and reduce the computational cost in relation to other multi-objective optimization algorithms.

Direct observation of ordered-disordered structural transition of MoS2-confined ionic liquids

Ionic liquids (ILs) are an emerging class of media of fundamental importance for chemical engineering, especially due to their interaction with solid surfaces. Here, we explore the growth phenomenon of surface-confined ILs and reveal a peculiar structural transition behavior from order to disorder above a threshold thickness. This behavior can be explained by the variation of interfacial forces with increasing distance from the solid surface. Direct structural observation of different ILs highlights the influence of the ionic structure on the growth process. Notably, the length of the alkyl chain in the cation is found to be a determining factor for the ordering trend. Also, the thermal stability of surface-confined ILs is investigated in depth by controlling annealing treatments. It is found that the ordered monolayer ILs exhibit high robustness against high temperatures. Our findings provide new perspectives on the properties of surface-confined ILs and open up potential avenues for manipulating the structures of nanometer-thick IL films for various applications.

Exploration and Practice in the Curriculum Construction of Integrated Production &amp; Education under the Background of New Engineering-Taking the Chemical Engineering Safety and Environmental Protection as an Example

Exploration and Practice in the Curriculum Construction of Integrated Production &amp; Education under the Background of New Engineering-Taking the Chemical Engineering Safety and Environmental Protection as an Example

Effect of surfactant modified phosphogypsum whisker on service performance of asphalt based on multi-scale experiments

The development of modern chemical technology had inevitably produced massive phosphogypsum (PSP), the accumulation and storage of PSP had caused serious economic losses and environmental pollution. As the secondary refining product of PSP, the application of phosphogypsum whisker (PSW) to asphalt pavement not only effectively mitigated the adverse impact of PSP on the economy and environment, but also promoted the resourceful utilization of solid waste. However, since PSW was an inorganic material, it was difficult to fuse well with asphalt. Therefore, to enhance the compatibility of PSW with asphalt, this study investigated the modification process of PSW by using four surfactants to modify PSW with organic coating. The effect of surfactants on the surface activity of PSW was evaluated by relevant tests, and the surface enhancement modification mechanism and microstructure of surfactants on PSW were investigated, and then the effect of surfactant-modified PSW (MPSW) on the service performance of asphalt was evaluated. The results showed that the surfactant covered the surface of PSW by intermolecular forces and chemical bonding, which enhanced the surface activity of PSW. The compatibility of PSW with asphalt was enhanced by surfactant, and the MPSW 10599was just physically blended with virgin asphalt. Although the brittleness of virgin asphalt was enhanced to a certain degree by MPSW, the thermophysical properties of virgin asphalt at low temperature was significantly improved, and the incorporation of MPSW enhanced the thermal stability and flame retardancy of virgin asphalt. The incorporation of MPSW would slightly increase the viscosity of virgin asphalt, but the viscous activation energy was reduced and the temperature sensitivity was improved. Furthermore, the low temperature performance of virgin asphalt was improved to a certain degree with the incorporation of MPSW, while the improvement effect was not significant once the temperature was close to the glass transition temperature. Finally, combined with the relevant test results, the recommended dosage of MPSW in asphalt was 10% in this study, and the surface modification of PSW by surfactant was a multifunctional method of powder modification.

Teaching classical machine learning as a graduate-level course in chemical engineering: An algorithmic approach

The demand for engineering graduates with technical skills in data science, machine learning (ML), and artificial intelligence (AI) is now growing. Chemical engineering (ChemE) departments around the world are currently addressing this skills gap by instituting AI or ML elective courses in their program. However, designing such a course is difficult since the issue of which ML models to teach and the depth of theory to be discussed remains unclear. In this paper, we present a graduate-level ML course particularly designed such that students will be able to apply ML for research in ChemE. To achieve this, the course intends to cover a wide selection of ML models with emphasis on their motivations, derivations, and training algorithms, followed by their applications to ChemE-related data sets. We argue that this algorithmic approach to teaching ML can help broaden the capabilities of students since they can judge for themselves which tool to use when, even for problems outside the process industries, or they can modify the methods to test novel ideas. We found that students remain engaged in the mathematical details as long as every topic is properly motivated and the gaps in the required statistical and computer science concepts are filled. Hence, this paper also presents a roadmap of ML topics, their motivations, and bridging topics that can be followed by instructors. Lastly, we report anonymized student feedback on this course which is being offered at the Department of Chemical Engineering, University of the Philippines, Diliman.

Influence of quadratic thermal radiation and activation energy impacts over oblique stagnation point hybrid nanofluid flow across a cylinder

Quadratic thermal radiation is a fundamental term within the field of radiative heat transfer, which pertains to the interaction of thermal radiation. It encompasses a quadratic correlation between temperature and radiative qualities. Although linear thermal radiation is more prevalent in numerous everyday applications, non-linear thermal radiation is important in some situations, particularly where a more precise representation of the radiative transfer of heat is required. The phenomenon assumes a crucial function in some contexts that need enhanced accuracy in modeling radiative heat transfer. In view of this, the present investigation is carried out to examine the hybrid nanofluid flow across a cylinder under the influence of quadratic, nonlinear and linear thermal radiation and activation energy. The governing system of nonlinear differential equations is transformed into a system of ordinary differential equations via similarity transformations. The current study presents the results utilizing the shooting and Runge-Kutta Fehlberg 45 numerical scheme. The outcomes show that the curvature constraint will improve all three profiles while solid fraction decreases velocity and raises the other two profiles. Quadratic thermal radiation shows less temperature distribution, followed by linear and non-linear thermal radiation cases. The rate of thermal distribution improves 0.60 % for linear thermal radiation case, 0.52 % for nonlinear thermal radiation case and 0.656 % for quadratic thermal radiation case from hybrid nanofluid to nanofluid. Further, the rate of mass transfer shows 0.068 % improvement for from hybrid nanofluid to nanofluid. The results provide useful insights that may be used to enhance system efficiency across various applications, including but not limited to the mechanics of fluids, chemical technology, and thermal administration.

A Roadmap to Support the Development of Chemistry Virtual Reality Learning Environments Merging Chemical Pedagogy and Educational Technology Design

A Roadmap to Support the Development of Chemistry Virtual Reality Learning Environments Merging Chemical Pedagogy and Educational Technology Design

Knowledge-Enhanced Spatiotemporal Analysis for Anomaly Detection in Process Manufacturing

Effective fault detection and diagnosis (FDD) is crucial for proactively identifying irregular states that could jeopardize operator well-being and process integrity. In the era of Industry 4.0, data-driven FDD techniques have received particular attention, driven by the proliferation of stored manufacturing sensor data. While these methods have proven adept at categorizing established process fault scenarios, there remains an imperative to identify and explain anomalies stemming from uncharted faults or the interplay of consecutive anomalies. To address this we present a knowledge-enhanced FDD approach that integrates well-defined chemical engineering knowledge with cutting-edge deep learning techniques. We apply our methodology, named Knowledge-Enhanced Spatiotemporal Analysis (KESA), to identify abnormal process conditions that may be a precursor to failure. Furthermore, we utilize the knowledge of the fundamental relationships governing the process to explain why this fault case has occurred. This type of in-depth fault analysis is only possible through leveraging domain expertise and marks a step forward in FDD technology in comparison to current literature. Using the benchmark Tennessee Eastman process dataset, we establish superiority in the accuracy and efficiency of our KESA model against state-of-the-art FDD algorithms. This work highlights the importance of a knowledge-enhanced approach to deep learning in complex environments, emphasizing the critical role of timely and interpretable fault detection. By providing explanations for model results, our KESA framework not only aids in effective decision-making but also has the potential to significantly reduce the time between fault detection and the implementation of proactive mitigation actions. This capability is paramount for improving overall safety, minimizing downtime, and ultimately contributing to substantial cost savings in industrial processes.

КАФЕДРЕ ЭНЕРГЕТИКИ ТЕПЛОТЕХНОЛОГИИ – 35 ЛЕТ

The article is dedicated to the 50th anniversary of the Department of Processes and Apparatus of Chemical Technology and the 35th anniversary of its renaming, in connection with the opening of a new specialty, to the Department of Energy engineering of heat technologie. Since 1990, the department has graduated more than three thousand specialists (engineers, bachelors, masters) for the energy sector, housing and communal services, the building materials industry, engineering and design centers. More than a third of graduates completed full-time education, and every tenth graduate received a diploma with honors. The department is implementing programs of additional professional education in the field of energy saving and increasing energy efficiency; 1,300 specialists have undergone advanced training at the department. The educational and scientific work of the department is aimed at basic heat engineering and heat and power education, energy saving and increasing energy efficiency, recycling of secondary energy resources, and the use of renewable and alternative energy sources.

Mutual Diffusivities of Mixtures of Carbon Dioxide and Hydrogen and Their Solubilities in Brine: Insight from Molecular Simulations.

H2-CO2 mixtures find wide-ranging applications, including their growing significance as synthetic fuels in the transportation industry, relevance in capture technologies for carbon capture and storage, occurrence in subsurface storage of hydrogen, and hydrogenation of carbon dioxide to form hydrocarbons and alcohols. Here, we focus on the thermodynamic properties of H2-CO2 mixtures pertinent to underground hydrogen storage in depleted gas reservoirs. Molecular dynamics simulations are used to compute mutual (Fick) diffusivities for a wide range of pressures (5 to 50 MPa), temperatures (323.15 to 423.15 K), and mixture compositions (hydrogen mole fraction from 0 to 1). At 5 MPa, the computed mutual diffusivities agree within 5% with the kinetic theory of Chapman and Enskog at 423.15 K, albeit exhibiting deviations of up to 25% between 323.15 and 373.15 K. Even at 50 MPa, kinetic theory predictions match computed diffusivities within 15% for mixtures comprising over 80% H2 due to the ideal-gas-like behavior. In mixtures with higher concentrations of CO2, the Moggridge correlation emerges as a dependable substitute for the kinetic theory. Specifically, when the CO2 content reaches 50%, the Moggridge correlation achieves predictions within 10% of the computed Fick diffusivities. Phase equilibria of ternary mixtures involving CO2-H2-NaCl were explored using Gibbs Ensemble (GE) simulations with the Continuous Fractional Component Monte Carlo (CFCMC) technique. The computed solubilities of CO2 and H2 in NaCl brine increased with the fugacity of the respective component but decreased with NaCl concentration (salting out effect). While the solubility of CO2 in NaCl brine decreased in the ternary system compared to the binary CO2-NaCl brine system, the solubility of H2 in NaCl brine increased less in the ternary system compared to the binary H2-NaCl brine system. The cooperative effect of H2-CO2 enhances the H2 solubility while suppressing the CO2 solubility. The water content in the gas phase was found to be intermediate between H2-NaCl brine and CO2-NaCl brine systems. Our findings have implications for hydrogen storage and chemical technologies dealing with CO2-H2 mixtures, particularly where experimental data are lacking, emphasizing the need for reliable thermodynamic data on H2-CO2 mixtures.

Improving Representation of Women in the Chemical Engineering Undergraduate Curriculum

Improving Representation of Women in the Chemical Engineering Undergraduate Curriculum

Modulation of polyaniline memristive device switching voltage by nucleotide-free analogue of vitamin B12

Memristive devices offer essential properties to become a part of the next-generation computing systems based on neuromorphic principles. Organic memristive devices exhibit a unique set of properties which makes them an indispensable choice for specific applications, such as interfacing with biological systems. While the switching rate of organic devices can be easily adjusted over a wide range through various methods, controlling the switching potential is often more challenging, as this parameter is intricately tied to the materials used. Given the limited options in the selection conductive polymers and the complexity of polymer chemical engineering, the most straightforward and accessible approach to modulate switching potentials is by introducing specific molecules into the electrolyte solution. In our study, we show polyaniline (PANI)-based device switching potential control by adding nucleotide-free analogue of vitamin B12, aquacyanocobinamide, to the electrolyte solution. The employed concentrations of this molecule, ranging from 0.2 to 2 mM, enabled organic memristive devices to achieve switching potential decrease for up to 100 mV, thus providing a way to control device properties. This effect is attributed to strong aromatic interactions between PANI phenyl groups and corrin macrocycle of the aquacyanocobinamide molecule, which was supported by ultraviolet-visible spectra analysis.

Role of ionic liquids in the electrodeposition of metals

Green chemistry techniques have gained significant importance in advancing chemical engineering and processes in the modern era, contributing to the implementation of sustainable development strategies. Ionic liquids (ILs) at room temperature have emerged as versatile solvents in catalysis, separation science, and electrochemistry. Conventional synthesis of ILs typically involves a two-step process using refluxing solvents, which is time-consuming and requires large amounts of organic solvents. This study investigates the synthesis of alkylmethylimidazolium salts by the co-heating of haloalkanes and 1-methylimidazole, highlighting the role of ILs in green chemistry, particularly in the electrodeposition of metals. The objective of this research is to explore the impact of ILs on the electrodeposition process, aiming to develop environmentally friendly and efficient metal deposition methods. The methodology involves the preparation of ILs through a facile and sustainable approach, followed by the characterization of their physicochemical properties. The ILs are then utilized as electrolytes for metal electrodeposition, and the resulting metal films are analyzed for their morphology, structure, and properties. The findings of this study demonstrate the significant influence of ILs on metal electrodeposition. The ILs exhibit excellent solvation properties, facilitating the reduction and deposition of metals with improved control over morphology and structure. Additionally, the ILs offer the advantage of reduced environmental impact compared to traditional organic solvents. The main innovation lies in the application of ILs as green solvents in metal electrodeposition, contributing to the development of sustainable and efficient processes in the field of green chemistry.